Tutorials

 

The tutorials are listed in the order that I believe they should be studied. However, the site is arranged so that the team can skip to any particular tutorial of interest. I highly recommend that Safety be covered first and then reviewed on a regular basis.

It is not interference for the Team Manager or an outside expert to teach the team about structural concepts or how to use tools, equipments and glues. It is interference for the Team Manager or anyone other than a team member to give specific solutions applicable to the challenge. The Team Manager should instruct anyone who comes in to teach that they can only teach general concepts and cannot teach specific solutions for the challenge. Nor can they answer specific questions about the way the team should proceed with any aspect of their solution.

When you are finished viewing a tutorial page click on the Tutorials link
on the left side of the page to be returned to this page or select
one of the links at the bottom to move to another page of the tutorial

 

 

Safety

General Safety Rules

 

Glue Safety Rules

If you misuse or abuse some of the glues you might find yourself making a trip to the emergency room. Carelessness can get you hurt or at the least cause some pain.

 

Weight Placement Safety Rules

 

Introduction to the Structure Challenge

The main object of every structure challenge is for the team to build a structure (or structures) to a certain specification and to test that structure (or structures) at the tournament on a structure tester. The specifications and scoring may change each year but the basic principle remains - you have to build a structure that supports weight.


If you are new to the structure challenge then you may have never seen a structure tester. Here are a couple of pictures of a structure tester. Photos were taken during the challenge It's Not Impastable. The first photo shows the tester base alone and the second shows the tester base with a structure, pressure board and a few weights.


In the first photo notice four white 4" x 4" posts at the corners. These are safety posts designed to keep the weight stack from falling more than a few inches when the structure being tested fails. There are plastic safety shields installed over the four sides of the tester. These shields keep pieces of the structure from flying out when the structure fails. Note the pipe extending from the middle of the tester base. This is a safety pipe over which the weights are placed. Its purpose is to keep the weight stack from tipping over when the the structure fails.

In the second photograph you can see the black pressure board sitting on top of the pasta structure. The pressure board is always the first "weight" placed on the structure. Olympic style weights are then placed on top of the pressure board.

If you look around you can find ideas about what structures look like. Here are some photos from my area. Two are from a local theme park and one is of an electrical tower that is in a field near my house.


Oil Derrick @ 6 Flags

Titan Roller Coaster
@ 6 Flags

Electrical
Tower

There are common elements in each of these structures. There are vertical or almost vertical pieces extending from the ground to the top (columns) that are designed to hold weight and there are pieces less than are less than vertical that do not contact the ground but run between the columns (braces).

General Concepts

 

Don't worry if you don't understand everything on these pages. Sometimes I am not sure that I completely understand all of these concepts.  There are 5 parts in this section:

 

What do you really need to know off of these pages?

 

Definitions

These definitions are probably not technically correct from an engineers standpoint but they are working definitions for these tutorials.

  • Structure - This is what you are building to hold weight.
     
  • Column - A full height vertical piece of the structure that has the primary purpose of supporting weight. Since columns primary purpose is to hold weight it is important that the bottoms of the columns contact the ground and the tops of the columns contact the surfaces they are supporting.
     
  • Brace - A piece of the structure that is designed to resist pressure (or stress) on the structure. Braces typically run between columns and are less than vertical.
     
  • Member - A general term used to refer to a Column or a Brace.
     
  • Critical Length - The length where wood (or any material) no longer bends but crushes. As a wood column gets shorter and shorter it becomes harder and harder to make it bend by putting weight on the top of the column. At some point the wood will not bend no matter how much weight you put on it - it will simply crush.
     
  • Buckling load- amount of weight required to cause a structure to fail.
     
  • Stress (Force) - Stress is what your team managers feel when it is 2 weeks to tournament and your script isn't done, your props aren't complete and you haven't finished a structure.
    smiley  Actually, stress is a force or pressure when one member of part of a member presses on, pulls on or pushes against another member or part of a member.  It can also be the pressure that tends to compress or twist another member or part of a member.

 

Stresses that act on your structure

What are the stresses (forces) that are acting on your structure?

 

Compression Compression Tension Shear
Compression forces try to crush things Compression forces also try to buckle (or bend) things. Tension forces try to pull things apart. Shear forces try to break things.

 

Typically, columns are always in compression. The columns are put in compression as the pressure board and weights are added on top of the structure. Braces can either be in compression or tension depending on the structure design. Braces are used to resist compression in columns.

Shear is difficult to explain. The technical definition of shear is the internal stress in a beam that is a result of non-axial loading. (Yeah.....I am sure you got that). Imagine holding your hands together upright in a prayer position and then sliding one of them down. (Thanks to Ernie Change for the definition and the visual demonstration). This is shear. Shear can occur at different places in the structure depending on the design. Most teams that solved the challenge DIsigning Bridges had to deal with shear in the bridges they constructed.

Another force that acts on a structure is a rotational force (or twisting). Technically it is called torsion or torque. This rotational force is a result of forces being transferred from the vertical load (i.e. the weights being placed) to a slightly horizontal load. Many teams structures fail because they do not adequately control the tendency of the structure to twist or rotate.

Click the link on the right for a short video of a structure twisting to failure. We took this video during the Triplicity challenge. We modified our structure tester so we could test the smaller individual pieces of the three part structure. I was using a strip of paper wrapped around the columns to resist twisting. As you watch the video you will see a bend form in the paper which affected its ability to resist the twisting forces and the structure twists down. Notice that the columns did not crush. This structure failed because it was not braced sufficiently to stop the rotational forces acting on it. VIDEO
(1.4MB MPG file)

The types of stresses or forces that act on your structure (be they compression, tension, shear) fall into two general categories. "Static" forces and "dynamic or live" forces. Static forces are forces that do not move. Once a weight is placed on a structure it is a "static" force or load because it is not moving. If you were to climb on top of the pressure board and do a dance this would be a live load because you are moving. The initial placement of a weight on a structure places a dynamic load on the structure because it is in motion.

When designing a structure, the team should concentrate on carrying the static loads placed on the structure while keeping in mind that they must also deal with a certain amount of dynamic or live load during weight placement.

Most structure challenges involve testing a static load on the structure by placing weights. The only dynamic load placed on the structure is the dynamic load created by weight placement.

Years ago my brother's team competed in a couple of structure challenges that required placing dynamic loads on the structure by: 1) applying a twist to the structure as certain increments of weight placement were reached and 2) by rolling pool balls down ramps into the sides of the structure at certain weight placement increments. I have never competed in this type challenge so have no experience in dealing with these types of forces.

Columns and the Law of Squares

There is an inverse square relationship between the length of a column and the amount of weight that it can carry. If you cut a column in half, one of the shorter pieces will carry four times as much weight as the original column. This is calculated as follows: Take the ½ (you cut the column in half) and invert it to get 2. Then square the 2 (2 x 2) to get 4. If you take a column and cut it into thirds, one of the shorter pieces will carry nine times as much weight. (Invert 1/3 to get 3 and then square the 3 to get 9). A column that is one forth (1/4) the length of another column will carries 16 times as much weight. You can only carry this so far. You can’t make a material stronger than it is. These examples assume that the only thing that changes is the length of the columns. If the column material changes in any way then the examples do not work.

An easier way to look at this may be to think of it this way. If I cut a column into 2 equal sections, the shorter section will hold four times as much weight (2 squared or 2 x 2). If I cut a column into 3 equal sections, the short section will hold nine times as much weight (3 squared or 3x3).

Here is a simple experiment to demonstrate this.

  1. Take a piece of 1/8" x 1/8" x 36" long balsa wood (do not use larger pieces and use only balsa wood).
  2. Lay the stick of balsa on a gram scale. The scale will register some weight for the wood.  With the balsa stick still on the scale, tare the scale (zero it).  This removes the weight of the stick from the scale reading.
  3. Holding the balsa stick perpendicular to the scale place a finger on the top of the stick and press down until the wood starts to bend. Record the reading on the scale. The number will fluctuate so just pick a number that is in the middle of the readings.
  4. Record this reading  - you have just calculated the "buckling" load (weight) of this particular 36" stick of wood.
  5. Cut the 36" stick into two 18" pieces.
  6. Take one of the 18" pieces and repeat steps 2,3 and 4. You have now calculated the buckling load of this 18" piece of the original 36" column. The buckling load of the 18" piece should be very close to four times the buckling load of the 36" piece.
  7. Take one of the 18" pieces and cut it to 12" in length. The length is now 1/3 the length of the original 36" piece. Try to predict what the buckling weight of the 12" piece will be by multiplying the buckling weight of the 36" by 9. (1/3 inverted = 3 * 3 squared = 9).
  8. Repeat steps 2,3 and 4 with the 12" piece and compare to your estimate.
  9. You can use these experiments to learn more about the properties of wood. Make up a chart and record the weight of each stick of balsa before you cut it and then the weight of each piece as you cut it into 18" and 12" pieces. How close to 1/2 the weight of the 36" stick are the two 18" pieces? How close to 1/3 the weight of the 36" stick are the three 12" pieces?

(Note: 1/8" x 1/8" balsa wood is used in this demonstration because most scales should be able to record all of the readings. Conducting the experiment with larger pieces or heavier woods could be dangerous because the amount of force required to make the pieces bend could be excessive resulting in breaking the wood and having a broken sharp point stick into a hand.)

You may wonder what good this information does, because the height of the structure has to meet the specifications of the challenge. It does not do any good to know that if you build a structure that is one half the required height that it will hold four times as much weight.

This information is useful because when designing and building a structure, bracing a column makes it act like two shorter columns. So, if you properly brace a 9” column in the middle you now have effectively created two 4.5" columns which can support four times as much weight.

Bracing Your Structure

There are two basic types of braces

  • Horizontal Braces - Braces that run horizontal between columns
  • Diagonal Bracing - Braces that run at an angle between columns

It is possibly an over simplification but horizontal bracing is generally used to resist compression forces in the column and diagonal bracing is generally used to add stability to the structure by resisting twisting.

The goal of designing a structure is to find the optimum mix of

  • Column material, size and shape
  • Brace material, size, shape and spacing

Ideally, columns should be braced at their critical length. The critical length of a column is the length at which the column will no longer buckle (or bend) no matter how much weight is placed on it.  A column at its critical length will fail by crushing.  One way to determine if you have braced a structure correctly is to watch the structure as it is tested. If you see the columns buckling (or bending) right before the structure fails then you have not properly braced the structure for the particular columns you have chosen. Well built structures should not "explode" but should simply crush.

There is one other thing you should keep in mind about bracing a structure. Imagine that a 6" column section will support 25 pounds. The Law of squares tells us that a 3" section of the same column will support 100 pounds (invert 1/2 to get 2 - square 2 to get 4 and multiply 4 x 25=100). How much weight will the column support if you stack the 3" piece on top of the 6" piece thus creating a 9" column.

If you said it will support 125 pounds then you guessed wrong. A column is only as strong as its weakest section so this column would only support 25 pounds since the 6" section of column would fail at 25 pounds.

Making a Plan - Drawing Your Structure

It is a good idea to have a plan before you start building. During the initial process of generating ideas and making quick tests of ideas a few notes and sketches may be all that are required. But quick notes and a few sketches do not help the team move toward consistent, strong, repeatable structures.

When designing a structure, draw enough details and views of the design so that it is clear what is being built. A structure may have a lot of symmetry and thus only a couple of views of the design will be required to describe the structure. If the design is complex then additional views of the structure may be required.

Different views that a team may wish to to draw:

You should be able to draw most structure designs to actual size. This makes it easier to refer to when you actually start building.

Assign numbers or labels to each structure design so that it is easy to refer to them later on.

Keep all of your designs in a notebook. You may want to augment the designs with digital photos of the completed structures.

Teaching drafting skills is beyond the scope of this website but following is a list of drafting tools and equipment a team may want to use as they begin to draw their designs.

  • Graph paper (comes in various grid sizes)
  • Sharp Pencils or mechanical pencils
  • Pencil sharpeners
  • Rulers with at least 1/8" precision
  • T-Squares
  • Triangles
  • Compass
  • Notebook (for keeping up with designs)
picture of drafting tools

The team may want to learn to use CAD software to draw their designs. CAD software can take a long time to learn to use. Check the links page for a link to a site that provides links to free CAD software.

Drafting Hints:

A drafting table makes it easy to draw consistently square lines. An alternative to a drafting table is to use a smooth square surface. I use glass samples (see discussion on building surfaces). Another alternative is to get a 2' x 2' piece of Medium Density Fiberboard (MDF) from a home improvement center and use this as your drafting surface.

pic - squaring up paper for drawing

This photo shows a piece of graph paper being squared up with the side of my glass "drafting" table using a T-Square. Once the graph paper lines are lined up it will be taped down. A piece of regular copy paper could also be taped down. By using the T-Square and a ninety degree triangle you can draw parallel lines that are consistent and perpendicular to the floor line of the drawing. Make sure the edges of the drawing surface are perfectly square so that you can use your T-Square from any side of the board or glass.

 

A good thing to know

Many times while designing you may find the need to divide a length into something that is not easily measured on a ruler. For instance you may have an eight inch column that you want to divide into three equal pieces. Even if you do the math you cannot find the calculated measurements on your ruler. Here is an easy way to divide a line into equal sections no mater what its length. Take the example given of dividing an eight inch column into three equal sections. That means each section is 2 and 2/3 inches long - something you can't find on your ruler. Here is an easy way to divide a length into any number of sections.  Click Images for larger picture. 

In this photo I have a piece of graph paper that has been squared with the edges of the glass. On the left side of the graph paper I have a column that is eight inches long that we want to divide into three sections.
In this photo you can see that I have extended a line across the page from the bottom and the top of the column. I have also laid a ruler with the "0" touching the base of the column and the 9 inch mark touching the line drawn from the top of the column. At this point I lightly drew a line along the edge of the ruler and place a mark at the three inch and the six inch lines - thus dividing the 9" long diagonal line into three equal sections.

In the final photo I take the T-square and squaring it with the edge of the glass I draw lines from the three inch and six inch marks on the nine inch long diagonal line over to the eight inch column. I have now successfully divided the eight inch column into three equal pieces and I didn't even have to figure out what the exact dimensions were - all I had to be was to be able to divide 9 by 3.

This same concept can be applied to dividing any line length into any number of equal sections.

 

Wood

While some structure challenges have required the building of structures with such diverse materials as pasta, paper and duct tape, wood and glue are the typical building materials specified in the structure challenge.

At times the challenge may limit the variety and sizes of wood that teams can use to build their structures. In recent years Destination ImagiNation® challenges have allowed the use of any woods in any size.

Teams should read the challenge and make sure they are using only materials that are allowed by the challenge. Composite materials such as particle board, plywood, hardboard, etc. have not been allowed in the past but it is possible that this may change in the future.

Hobby shops typically carry three types of wood: basswood, spruce and balsa. You can find other varieties of wood at Lumber Yards or Home Improvement Centers. You can also find specialty wood shops by checking the yellow pages or doing on-line searches.

Properties of wood

Wood has a grain to it and will react differently depending on the way the grain runs in the wood. An easy way to demonstrate this is to take a piece of 4" x 4" x 1/8" balsa wood and try to bend it one direction and then try to bend it in the other direction. You will find that the sheet bends easily when you bend it with the grain of the wood and that it is more difficult to bend the wood against the grain of the wood. When designing and building your structure keep in mind how the grain affects how the wood performs.

Tensile Strength

If you have long thin strips of wood that you are going to work with you might want to test all the strips for tensile strength before you begin to cut them up into pieces for your structure. You can do this with a simple deflection test. Note that you can only run this simple test on wood sizes up to about 1/4" x 1/2" cross section.

To test deflection you need:

Steps

  1. Use the yardstick to measure the height of the table from the floor (assume 30" for this example)
  2. Hold a strip of wood with all but 6" of the wood hanging off the edge. Lay a book across the wood strip even with the edge of the table. Hang the paperclip hook with the clay on it about 1" from the free end of the strip of wood. If you are testing wood with a very small cross section (for instance 1/8" x 1/16") it may not be necessary (or possible) to hang the clay on the end of the strip. With other cross section sizes you may have to use a different size pieces of clay.
  3. One person should hold the yard stick vertically on the floor at the end of the stick. Write down the height of the end of the wood strip from the floor. Subtract this number from the height of the table (measured in step 1) and this gives you the amount of deflection for the particular wood strip you are measuring.

The wood with the least amount of deflection is the wood that has the greatest tensile strength. Group the wood of similar tensile strength together. You could label the wood lightly in pencil with the amount of deflection. The smaller the number the greater the tensile strength.

This is the wood that you should use to construct your structure. If you have limited supplies of the wood strips then use the strips of wood with the greatest tensile strength for the longest pieces of your structure. Then move toward the strips with lesser tensile strength for the shorter pieces of the structure.

What wood should I use?

Destination ImagiNation structure challenges typically allow the use of any natural wood. As you are trying to decide what woods to use, spend some time with the various types just playing with them.

Other Considerations?

Moisture in the air affects how the wood performs. All woods absorb some moisture from the air - especially balsa wood. This moisture also affects the weight of the structure. It is possible for a wood structure weighing less than 20 grams to absorb as much as 1 gram of moisture from the air. Brainstorm ways to control this moisture absorption and to remove moisture from the structure if necessary.

Structure Building Tools and Equipment

The following sections will help you when you start choosing the things you want to build with and on.

Work Area - Where to build your structure.

Construction Aids - Things that will help you assemble your structure.

Cutting Tools and Surfaces - How do I cut the balsa?

Other Tools and Equipment - Others items you may wish to use

 

Work Area

The ideal work area is a location that can be dedicated to building a structure. The area should be well lit and well ventilated since many glues give off fumes that might irritate eyes. Good lighting is essential. If room lights are not sufficient you may want to use desk lamps.

A sturdy table that does not rock is important. The kitchen table at the team manager's house is probably not the best location to build structures because it is inevitable that glue or razor saw marks will end up in a location that the team manager's spouse will not appreciate. If there is no option other than the team manager's table then the team manager may want to purchase a piece of 1/8" or 1/4" hardboard (Masonite) to cover the table while the team works.

Since building structures creates dust and wood scraps it is better if the floor in the work area has a hard surface instead of carpet so that cleanup is easier. Also, some glues will melt some carpet fibers and spills will happen.

It is important to keep your work area dust free. Dust floating around in the air can get into your glue and affect its performance. Always cleanup dust and scraps before you start assembling your structure.

Construction Aids

There are many tools available at hardware stores that can aid in the Construction of your structure. Tools for making sure things are aligned, or to help you determine if you have constructed something square. Most the model suppliers listed on the Additional Links page carry various modeling tools that are useful to structure teams. Pitsco and Micro-Mark also sell tools that can be used by structure teams.

Construction Aids

  • Carpenters or Framing Square to help in squaring things or measuring the height of a structure. (Carpenter's and framing squares are not always 100% square since they are designed primarily for rough carpentry. They are probably accurate enough for most structure teams since no one can build perfectly anyway. However, the obsessive structure builder may want to invest in an Engineer's square. These are more expensive that the carpenter's and framing squares.)
  • Clamps to hold things in place (most hobby shops carry some type of model clamps.) Most home improvement centers carry clamps that are small enough for structure teams to use.
  • Triangles - to assist in drawing and setting up jigs
  • Hat Pins or Safety pins (can be used to hold materials in place on a jig)
  • Masking Tape (to hold things in place)

You can find many uses for these tools. For instance, assume you would like to mark several pieces of wood in the exact same place. You could measure each piece individually or you could use a carpenter's square and framing square to do it all at once.

In the photo on the right you can see that I have taped a framing square to a piece of glass and have laid several pieces of wood flush against the framing square. The piece of wood on the far right with a blue dot is my marking template. By placing the carpenter's square flush against the side of the framing and lining it up with my marking template I can draw a light line across all of the pieces I wish to mark. If you do this use a soft lead pencil. A hard lead pencil or ballpoint pin will indent the wood.

When you start constructing your structure you may want to have a construction surface that you keep clear of glue scrapes and cut marks. Here are some materials that work well as construction surfaces.

Surfaces to build on

  • Glass
  • Plastic
  • Plastic Laminate
  • Hardboard

Glass is a good surface to work on because it is flat, non-porous and glue can be easily removed from the surface with a razor blade scraper. If you know someone in the construction industry ask them to ask one of their glass subcontractors to give them old glass samples. Glass samples are usually 12" x 12" in size. Add some rubber feet to one side and you have a great work surface. If you do not know anyone in the construction industry check with some local glass shops. They may have some glass samples that they would be willing to donate.

Some plastics also make good surfaces to work on. However, you may need to test the surfaces because some glues will react with the plastics and melt them creating a surface that is no longer smooth.

Plastic laminate is another surface to consider. You can find plastic laminate (or melamine) shelves at most home improvement centers. Test them with the glues that you are using. It is possible that glue that dries on the surface will remove the laminate when you try to clean it off.

1/8" or 1/4" hardboard (sometimes called Masonite) is another surface you can consider.  Most hardboard has a smooth surface on one side that is a good building surface.  You can purchase hardboard in 2'x2' or 2'x4' pieces of hardboard at most home improvement centers.  You can ask them to cut it into 12" x 12" squares.  It can be difficult to clean dried glue off of hardboard without damaging the surface of the hardboard.  Promptly wipeup any spills to keep your worksurface smooth.

Other Aids

  • Notebook - for recording notes and results
  • Digital camera - for "as built" documentation of the structure
  • Digital video camera - for recording testing and documenting failure of the structure
  • Calculator or computer spread sheets - for planning how much the structure might weigh
  • First Aid Kit (aneseptic and bandages)
     

 

Cutting Tools and Surfaces

There are many different types of tools that are available to use for the construction of your structure.  These tools generally fall into 2 categories - cutting tools and shaping tools.

 

Cutting tools include this such as:

 

Razor blades are generally only good for cutting balsa wood to a thickness of about 3/16". When the material being cut is other than balsa wood or balsa wood larger than 3/16" the team may need to consider using a Razor Saw. Razor Saws are generally used in conjunction with a miter box. The miter box helps insure that the cut is square. Razor saws come in a variety of sizes and teeth configurations. You may have to test several saws to find the saw that works best for the material you are cutting.

The "Timber Cutter" from Pitsco is a tool designed specifically for cutting 1/8" x 1/8" wood at a 90 degree angle with a single edged razor blade. The design is such that the razor blade is kept away from fingers. Pitsco also sells another cutting device called the "Chopper III" that makes angle cuts on larger material. The blade on this cutter is exposed.

 

Shaping Tools

There may come a time that you need to make a small adjustment to your structure whether it be too much glue dried in a spot and it keeps you from placing a piece of wood properly or you have to make a piece just a "little bit" shorter to fit. Shaping tools are what you need for this.

  • Sandpaper (Various Grits)
  • Files
  • Emory boards

Cutting Surfaces

When cutting you will need to have something sturdy underneath the piece of wood that you are cutting.  Preferably not the kitchen table.  I recommend that you get a separate surface for cutting on even if you have covered your kitchen table with hardboard for protection.


One surface to consider is the self healing cutting mats available from hobby shops. Another option is to use 1" x 12" lumber cut into 12" to 24" sections. Most home improvement centers will cut lumber into pieces for a small additional charge.

It is important to remember that if you are using glass, plastic or plastic laminate for a building surface, you should not cut on these surfaces. You might scratch the surface (thus making it harder to cleanup) and you will be dulling your cutting tools when the contact the hard surface.

Notes about cutting wood

When cutting with razor blades a slight rocking back and forth motion (parallel with the blade) produces a cleaner cut than just pressing straight down with the blade.

When cutting with a razor saw make sure that you are using the saw to "saw" the wood with a smooth back and forth motion. Do not try to "cut" the wood with the saw.  Let the saw do the work.

When you cut wood you damage or crush the cells in the end of the wood. This can have an impact on how the wood performs. Many of you have done the experiment where you roll up a piece of copy paper, hold it in place with a rubber band and are able to support a book or several books on the rolled up tube. Now think of what happens when you bend or crush one end of the tube - it no longer supports as much weight. You may want to brainstorm ways to reduce this damage to the wood.

Other Tools and Equipment

Other Useful Equipment

Using a scale helps the team to select the wood that they want to use. They also can use the scale to make sure they meet the specifications of the challenge. An accurate scale helps to keep track of your structures weight at all steps during the construction process.

Levels are useful for determining if surfaces that are designed to be level are actually level. Levels can also be used to make sure your structure tester is setting level.

I recommend that structure teams have their own structure tester or at least have ready access to a structure tester. A structure tester is the best way for testing your designs. Most teams do not spend enough time practicing and working with weights, weight placement and the structure tester. A team should not show up a tournament without having practiced with a structure tester at least a few times. Information on constructing a structure tester is available here: How To Build a Tester.

Destination ImagiNation® tournaments use Olympic Style weights. There are a variety of styles of Olympic weights - each with different edge details. Some weights might have a straight edge like a washer, others may have very wide edge details and some edge details may be rounded like a bagel. Click here to see a close up of a couple of types of edge details. Note that the silver 45 pound weight has a much wider edge detail than the black weight. The sliver weight is more difficult to grip since the edge rim is so wide. Tournament Directors generally have little or no control over the specific types of Olympic weights that will be used at the tournament so it is important that a team have been exposed to a variety of the types so they can develop a strategy for the different weight styles they might see.

Glues and Adhesives

Most structure challenges allow the use of any type of adhesive. However, it is important that teams read the challenge and make sure that there are no restrictions on the types of adhesives that can be used. This page deals primarily with products that fit under the generally accepted definition of glue. Sometimes the challenge may have a very loose definition of what is allowed to be used as glue or adhesives. Teams should take this as an opportunity to research alternate "glue-like" products that are not covered under this topic.

It is not interference for the Team Manager to tell a team they cannot use a glue if the Team Manager does not believe the team can use the glue safely. It is not interference for the Team Manager to purchase a variety of glues for the team to experiment with and to teach them how to use them properly. However, the team must make the choice about the glue or glues that they wish to use for their structure.

Gluing two pieces of wood together may not seem like a big deal. But there are many different glues and adhesives that teams can choose from and that they must then learn to use correctly. Experienced builders try to glue their structure together so the joints are consistently strong without using too much glue.

All glues require that application of some amount of pressure to set properly. Refer to the manufacture's recommendations for the amount and length of time pressure should be applied. It is also important that the process used to apply pressure to the glue joint does not apply extra stress to the materials so that they are weakened by the gluing process.

The following is a list of different types of glues. This list is not all-inclusive. You can find additional glues that are available by visiting a local home improvement center, hobby shop and by doing searches on-line. Click on the links below for additional information about the glues listed. Brand names are listed for reference only and are not meant to imply that this is the only (or best) product to use in any particular category.

Select a link at the bottom of the page for more information on specific adhesives.

Review the safety rules on the SAFETY page before using any glues.

Criteria teams should consider when selecting a glue.

(Teams may also want to devise tests to determine the answers to these questions.) Plans for a glue joint testing device are available from the Specialized Balsa Wood website listed on the links page.

This is by no means a complete list of all the criteria teams should consider when selecting a glue or glues. Teams should come up with their own glue selection criteria.

General Rules for Gluing

Is there a best glue to use?

There are structure teams that "know" that they are using the best glue for their structures. While certain glues work best in different conditions my personal observation is that it is not so much the particular glue that a team uses - it is how the team uses the glue they have chosen. Most glues will form a bond that is stronger than the wood that is being glued. Examine structures that you have tested paying particular attention to the glue joints. If the joints tore and there are shreds of surface "A" clinging to surface "B" then you have probably used the glue correctly. This demonstrates that the glue joint was stronger than the materials being glued. If, however, the joint broke "clean" and there is no tear out of one surface then you may not be using the glue correctly. If this continues to occur then the glue you have selected may not be the best glue for this particular application.

More than you want to know

The terms glue and adhesive are often used interchangeably. Technically "glue" is a natural adhesive made by "boiling collagenous animal parts into hard gelatin and then adding water." Adhesives include glues and any synthetic material capable of creating a bond between two materials.

Polyvinyl Acetate Glue

(PVA for short) is the white glue typically sold for school use.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Pros

  • Very safe.
  • Non-toxic.
  • Easy to clean up.
  • Bonds in about one hour.

Cons

  • It is not waterproof
  • Not specifically designed for wood

Cleanup

  • Cleanup with damp cloth.
  • Remove from skin with soap and warm water.

How to Use

Apply a small amount of glue to wax paper (about the size of an aspirin or dime). Use a toothpick to apply a drop (or several drops depending on the size of the piece being glued) on one surface. Place pieces together and hold under pressure per manufacturer's recommendation. Refer to aliphatic glue page for pictures. The procedure is the same. Once the glue on the wax paper starts to film over the glue should not be used.

Aliphatic Glues

Aliphatic glues are also referred to as wood glues and include glues such as Elmers Wood Glue and Titebond.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Pros

  • Non-toxic.
  • Joints are slightly flexible.
  • Easy Cleanup.

Cons

  • Joints must be clamped or held under pressure for at least 30 minutes.
  • Joints are slightly flexible.

Cleanup

  • A damp cloth can remove glue that has not dried.
  • Clean hands with warm soap and water

How to use

It does not take a lot of Wood glue to make a good joint. In fact, too much glue will create a weak joint. The tips with most wood glues do not allow fine control of the amount of glue being dispensed. One method for applying wood glues is to place a small dab of wood glue (about the size of an aspirin or possibly a dime) onto a piece of wax paper and then use a toothpick to pickup small amounts of glue (Photo 1). Then use the toothpick to transfer glue to the structure. (Photo 2). Then apply pressure to the joint per the manufacturer's use instructions. You can use a small weight (Photo 3) or a book to apply pressure. You can also use hat pins (Photo 4) to maintain pressure on the joint. When the glue on the wax paper starts to film over (may take from 10 to 20 minutes) it is no longer useable and should be discarded and replaced with fresh glue.

Photo 1
Photo 2
Photo 3
Photo 4

 

Cyanoacrylate

Cyanoacrylates (CA glues for short) include glues such as Jet, Super Glue and Krazy Glue.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Pros

  • Sold in various viscosities with set times from 1 second to 1 minute allowing very quick assembly.
  • Generally non-toxic (but that doesn't mean you should eat it)

Cons

  • CA glues give off fumes while setting that can irritate the eyes (wear goggles and work in a well ventilated area)
  • CA glues give off heat while setting which can lead to minor burns on the skin.
  • Typically has a very quick set time once it is put under pressure and thus is not very forgiving of mistakes during assembly.
  • Does not fill gaps very well although certain of the slower setting CA glues will fill some gaps.
  • Does not work well for end-joint connections.

Cleanup

  • Most CA manufactures sell a De-bonder for cleanup and removal of CA glues.
  • Most De-bonders are acetone which can be purchased in quart containers at hardware stores. Fingernail polish remover will also work.

How to use

  • When cutting the tip off CA glues for the first time it is a good idea to remove the lid to release any pressure that may have built up in the bottle so that you do not risk the glue spraying out when the tip is cut.
  • With CA glues the closer the parts fit together the stronger the bond.
  • CA glues work best in a thin layer between smooth surfaces so any rough spots on the mating surfaces should be smoothed before gluing.
  • Do not touch the tip to the surface being glued.
  • Most places that sell CA glues also sell Teflon tubing and/or extender tips which can aid in controlling the amount of glue that is dispensed.
  • Medium viscosity (5-15 second bond time) and heavy viscosity (20-60 sec bond time) CA glues are used in the same way. Place a small dot (or dots depending on the area being glues) on one surface. Then carefully place the pieces together (you probably will not get a second chance) and hold them under pressure for the manufacturer's recommended time. (see photo below)
  • Practice using small dots of glue to glue pieces together. Experiment using more or fewer dots of glue to determine the optimum amount of glue to use for each type of joint.
  • Very thin viscosity (1-3 second bond time) CA glues are used differently. Place the pieces you wish to glue together and then carefully drop the glue onto the joint. These glues are so "thin" that they wick into the joint creating an almost instantaneous bond. Be very careful because it is very easy to glue your fingers to the materials.

Other Notes

  • While CA glues set very quickly they do not reach full strength for several hours. Refer to instructions included with the glues. Allow for this before subjecting to maximum stress.
  • CA glues should be kept in a cool place out of direct sunlight.
  • CA glues typically have a shelf life of from 12 to 24 months.
  • Unopened bottles of CA glue can be stored in the refrigerator to prolong shelf life but should be warmed to room temperature before using.
  • Always buy a few extra tips when purchasing CA glues. If manufactures instructions for cleaning up after each use aren't followed it is very possible that a glue tip may become unusable until it is soaked in acetone to remove the glue that has setup in the tip.
  • Buy several extra tips. When you finish using a tip, store it into a small medicine bottle (the type with a water tight lid) filled with acetone and let it soak. If you do this make sure you remove the tip from the acetone and let it dry thoroughly before using.

  Interesting Fact

CA glues are sometimes used to suture wounds and to graft skin, bone and cartilage. However, if you happen to graft your skin to the structure you are constructing you should remove it so that you aren't cited for using a material on the structure that is not allowed in the challenge. ☺
 

Epoxy Adhesive

There are many brands of Epoxy Glues. Elmer's sells a product called Elmer's Probond Epoxy Glue. Epoxy glues are sold as two components that must be mixed to be used.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Safety

  • Use in well ventilated area.
  • Keep from contact with skin.
  • Work in well ventilated area.
  • Keep away from flames and sparks.

Pros

  • Water resistant
  • Solvent resistant
  • Fills gaps
  • Bonding times vary from very quick to 24 hours.

Cons

  • Some epoxies are toxic (varies by brand and product)
  • Once the two components are mixed there is a limited time that the glue is useable.
  • Some epoxies are flammable (varies by brand and product)
  • Relatively expensive when compared to other glues.

Cleanup

  • Remove dried glue from hands and work surfaces with Acetone. Wash hands with soap and water after cleaning with acetone.

How to use

Every epoxy glue has its own requirements but generally equal parts of the two components are mixed on a piece of wax paper. Use a toothpick to apply glue to joints. Follow manufactures recommendations for open work time, clamp time and bonding time. The same technique shown in the pictures on the Aliphatic glue page can be used for Epoxy glues.

 

Polyurethane Adhesives

Polyurethane Glues include glues such as Gorilla Glue, Elmer's Ultimate Glue Polyurethane and Titebond Polyurethane Liquid Glue. Polyurethane glues were designed specifically for wood but may work well on other materials as well.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Safety

  • Work in well ventilated area
  • Keep acetone or denatured alcohol on hand for cleanup from hands
  • Keep from contact with skin.
  • Wear goggles

Pros

  • It is solvent free.
  • It is waterproof.
  • It has a twenty minute open working time which gives time to get things positioned properly and clamps or other holding mechanisms in place.
  • Because of its expansive properties it tends to work better than most glues for end-grain joints.
  • Slightly elastic.
  • It expands and gets "into" the wood as it sets so creates a very strong joint.

Cons

  • It is toxic to touch and ingest.
  • One surface must be slightly moistened for the glue to set. Polyurethane glues expand with moisture and can be extremely messy if not used carefully.
  • Polyurethane glues require pressure to adhere and so joints must be kept under pressure until the glue has set. Set time can run as long as 4 hours during which the joint must be kept under pressure.
  • More expensive when compared to other glue options.
  • It expands and foams as it sets so if used incorrectly can spill out beyond the allowable limits for a glue joint.
  • Slightly elastic.
  • Difficult to remove from hands once it dries.

Cleanup

  • Denatured Alcohol or other solvents will cleanup polyurethane glues.
  • Acetone will also work for cleanup.

Instructions for use

Each manufacturer's instructions for use are slightly different. These instructions are included for reference only. It takes very little polyurethane glue to make a strong joint. After the surfaces to be glued have been smoothed, take a damp (not wet) cloth and lighted dampen one of the surfaces being glued. Next spread a very small amount of the polyurethane glue on the other surface. A good way to spread the glue is to use an old credit card and holding one of the long ends hold light pressure on the card as you drag it across the glue to create a thin sheen of glue on the surface. Mate the two pieces together and apply pressure in accordance with the manufacture's recommendation - usually 2 to 4 hours.

It is very easy to use too much of a polyurethane glue so you may want to practice on scrap pieces of wood until you get a feel for the correct amount of glue to apply. Click on the link on the right to see an example of what happens when you have too much glue in the joint. You can see that the glue has foamed out beyond what is generally allowable under structure challenge specifications. It is very difficult to remove this foam without damaging the underlying surface.

Because these glues expand it is very important that the surface you are building on be non-porous. Otherwise, the glue from the joint may expand into the surface underneath and you will find your structure glued to the work surface. I have had the glue grip onto a plastic laminate surface I was working on and tear off a piece of the laminate when I picked up the structure. Taping a piece of wide clear shipping tape to the surface under the joint prevents this from happening.

These instructions are from my experience using Gorilla glue. As I browed websites looking for information on glues I noticed that some manufacturer's have a polyurethane glue that may not require moistening of one surface.

Contact Cement

Contact cement includes glues such as DAP Weldwood. Used in the construction industry for joining plastic laminate to counter tops.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Safety

  • Use in well ventilated area.
  • Keep away from heat, sparks and open flames.

Pros

  • Long open time (up to 2 hours) with short (almost instant) set time

Cons

  • Very Toxic - Inhaling vapors can be harmful or fatal.
  • Vapors and liquid are extremely flammable.
  • Can be very messy.
  • Very difficult to adjust pieces once put into place.

Cleanup

  • Remove from skin with acetone and then wash with soap and water.
  • Remove from work surfaces with acetone.

How to use

  • Apply thin layer to both surfaces and allow to dry until glossy. Typically at least 15 minutes up to two hours.
  • Press parts together.

 

Model Cement

Model cement is sold by many suppliers but the most commonly known is Testor's Wood Cement. Note that Testor's and other manufacturer's sell many different types of model cement - some intended for use with plastic and some intended for use with wood. Read the labels before purchasing.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Safety

  • Avoid breathing vapors
  • Work in well ventilated area.
  • Avoid contact with eyes and skin.
  • Wear goggles.
  • In case of eye contact, flush eyes immediately with water and seek medical attention.
  • Vapors may cause a flash fire if exposed to open flames or sparks.

Pros

  • Designed specifically for small model construction.
  • Relatively quick initial set time allows rapid assembly of structure although full bonding does not take place for at least twelve hours.

Cons

  • Toxic.
  • Fumes are dangerous if used in an enclosed area. Use only in a well ventilated area.
  • There is a reason that this glue is kept behind the counter at hobby stores.
  • Highly flammable.

Cleanup

  • Remove dried glue from hands and work surfaces with Acetone. Wash hands with soap and water after cleaning with acetone.

How to use

Use in a well ventilated area away from open flames and sparks. The tips of model cement are generally small enough to control the amount dispensed. However, you may find it easier to dispense a small amount on a piece of wax paper and then use a toothpick to apply the glue. Apply a small amount of glue to each surface to be glued. Allow to dry for a few seconds, press together and allow twelve hours for full bonding of wood. Pictures on the Aliphatic Glue page illustrate this technique.

Structure Building Jigs

t_structure/image/pics/jigmaterials.jpg

A Jig is a gauge, pattern, or mold used as a guide to the form of a piece being made. They can be 2 dimensional or 3 dimensional. You do not have to use a jig but using a jig helps you build consistently.

 

ANY JIGS USED BY THE TEAM MUST BE BUILT BY THE TEAM

 

2 Dimensional Jigs

Create a 2 dimensional jig by pinning down a design drawing to a piece of cardboard and then place this cardboard on top of a piece of very heavy form or insulation board. Use straight pins or hatpins to hold pieces in place while gluing.
Create a 2D jig by using magnets on a piece of sheet metal. You can find small 1' x 2' pieces of 1/8" sheet metal at most home improvement centers. Small square magnets are available at most hardware and hobby shops. The flexible magnetic strips designed to have business cards glued to them are also useful. Lay your design on the sheet metal and then use magnets to outline your design and hold pieces in position while gluing.
Tape a design drawing under a piece of glass and then tape your pieces to the top of the glass while assembling.
Glue aluminum tubing and keystock to a piece of glass using CA glue to create a 2 dimensional frame for assembling a structure. Square up a piece of aluminum tubing with the side of the glass and glue in place. Use a triangle or square to position keystock (metal bars) in the position you want and glue them into place with CA glue.
As you start building you may want to make some tests using different jig configurations. The structures for DIsigning Bridges were very large (150 grams) when compared to the typical structure challenge (20 grams or less). Initially I created some temporary jigs using only pieces of wood, clamps and triangles to create my jig. The aluminum angle is screwed to a piece of laminate shelf to create the bottom of this jig. The weights are being used to hold pieces in position and to put pressure on the glue joints.
After a while I created a jig using pieces of cut up wood shelving screwed to pieces of MDF board (Medium Density Fiberboard). You can't see it very well in the picture but I put clear tape on the jig around all of the places where glue might seep out of a joint so that i didn't glue my structure to the jig.


3 Dimensional Jigs


At some point you will want to assemble your two dimensional sections into a three dimensional structure. This can be done without the use of a jig by using carpenter's squares, a steady hand and patience. You may also want to create a 3D jig to use in assembling your structure.

The picture on the right shows a variety of materials that can be used to construct a 3D jig.  You can use aluminum tubing or blocks of wood to assemble a jig.

There are lots of options to choose from when creating a 3 dimensional jig. You may decide to make your own using materials such as those shown in the photograph. You should also visit hobby shops and home improvement centers and look for materials that can be used for a 3D jig with little or no modification. Hobby shops have plastic boxes and florist foam in various sizes. Home Improvement centers have blocks of wood in various sizes and shapes. Just remember that the team must create any jigs that you choose to use. This does not mean you cannot use something that you have purchased from the store as a jig. It does mean that if the thing you purchased requires modifications to use as a jig - then the team must make the modifications.

Final Notes on Construction Jigs

 

Documenting Your Work

Most think that being able to build a great structure is the key to doing well in the structure challenge. While this is definitely important there is one thing that is much more important than being able to build a great structure. And that is being able to build a great structure twice. The best design in the world does you no good if you can't repeat it.

While building your structure document every step of the construction process. What is your design? What wood are you using? What glues are you using? How much does it weigh? Keeping good records allows you to build the same structure again.

Record keeping

Part of your record keeping should be to analyze the broken structure to determine what failed and what might be changed to improve the structure.

Analyzing the structure

  • Watch the structure while it is being tested and make notes. It is best to leave the safety shields in place while doing this. If your tester does not have safety shields make sure you wear safety goggles although I recommend that you wear them even if safety shields are in place.
  • Video tape the testing and then watch the video tapes to see if you can determine what caused the failure. The failure of structures is faster than most video cameras can record but you may be able to get an idea what happened. Something I have always wanted to do is to find someone who has a sports camera like those used to film golf swings. These cameras are fast enough to record the actual collapse of the structure.
  • Keep your old structures to review while contemplating new designs. Study them to see if you can determine what caused the failure. I keep structures in a baggie with a label and the results so that I can refer back to them while thinking about design changes. In the photo on the right you can see that we labeled structures with the initial of the person who built them with a running count number of the structure. Thus "J5" in the photo indicates that this was the fifth structure built by Jeff. These tests were of structures that were scored on a ratio and so we also recorded the structure weight and weight held on each of the label sheets we put into the baggies with the structures.

One reason it is difficult to analyze a broken structure is that the failure is often catastrophic with lots of pieces flying all over the place. One way to control this is to adapt the structure tester. After the structure is set and the pressure board is in place (but before any weights are placed) add shims made from hardboard and sheet metal to the top of every safety corner post so that the maximum the pressure board will fall when the structure fails is 1/8" to 1/16" or less. The shims should be cut to approximately the same size as the safety posts (3-1/2" x 3-1/2"). If the pressure board only falls 1/16" when the structure fails it may be easier to isolate the initial failure.

As you modify the design of your structure to improve its performance don't change too many variables at once. If you change too many things you may not be able to determine which design changes worked and which didn't. Consider changing only one variable at a time. This may require you to build more structures initially but it will pay off in being able to isolate the changes that improve the structures performance and those that do not.

The Tournament

Weight Placement

Many new structure teams do not spend enough time thinking about weight placement. During the tournament there are no do-overs for weight placement. If you drop a weight or hit the structure and it breaks early then testing is over. Make sure that you have practiced enough with weight placement so that you are comfortable around the tester and with handling the weights.

Have more than one person practice weight placement. A weight placer could be sick on tournament day and someone else would have to take their place.

Elementary and Middle Level teams may have adults assist with placement of weights that weigh 25 pounds or more. Teams should verify this within the rules of the current years challenge. It is the teams decision on whether an adult will assist with weight placement. It is very important that the adult assistant provide only muscle. The selection and placement of weights is the teams responsibility and the adult assistant should not be directing this in any way. If appraisers feel that the adult assistant is guiding weight placement then the adult assistant may not be allowed to continue to assist with weight placement. The adult assistant should also practice with the team so that the weight placers and the adult assistant are comfortable with each other. There are additional comments on the adult assistant on the Team Manager info page of this site.

Click the following link to see a short (2 minute) video of a team placing weights. This is from the challenge Triplicity where teams had to construct three structures that stacked on top of each other. (You Tube Video)

Mock Check In

It is very important that structure(s) brought to tournament meet the specifications of the challenge. Structures that do not meet ALL of the specifications will not be scored for weight held. A few weeks before tournament the team should do their own mock check in. Take the specifications from the challenge and go down the list, checking off each item (weight, height, center hole clearance, etc.). It is very stressful to get to tournament and find out that the structure must be modified in order to be able to test it for score.

Transporting the structure

The team needs to decide on what they think is the safest way to carry the structure to the tournament. A cardboard box can easily be sat on and destroy the structure inside. Laying it loose in the front seat of the car is probably not a good idea either because someone can just jump into the car and sit on it. (This hasn't happened to my team but I do know of teams that had this happen to them.) Treat the structure like gold so that it arrives safely at the tournament. Some teams carry a spare structure to tournament as a backup just in case.

Tournament Day Considerations

Tournament Day

These comments are generic. Refer to the specific challenge and travel guide for specifics on the current year's challenge.

As soon as possible scope out the performance site and determine what weights are available. The weights you planned on using may not be available. Note that the challenges generally state that a team can ask the Regional Director or Tournament Director for a list of the specific weights that will be available at tournament.

Checking out the site also allows you time to think about how to stage your performance. The location of the tester board and weights cannot be changed so you may have to adjust your staging to accommodate the actual layout of the performance site.

Check In Procedures

Typically, structure teams must check their structures in from 30 minutes to 1 hour before their presentation time. Check in times will generally be noted when the tournament schedule is published. Check in procedures vary from year to year. Consult the Travel Guide for Teams that is published in January or February of each year for current year check in procedures. Generally, structure teams are responsible for all handling of the structure during check in and appraisers are trained to not touch the structure during the process. Refer to the current years challenge and travel guide for additional information.

Teams with structures that do not meet specifications will be given time (as it is available) to modify their structure to comply with specifications. Once check in is complete the structure is left with the weigh in appraisers. Teams should have a container to store the structure. The weigh in appraisers will "seal" the container in some manner. Teams will be instructed when to return to weigh in to pick up their structure prior to their performance.

Brainstorm a list of materials and tools that you might need if for some reason you have to modify and/or repair the structure once your reach the tournament site. Pack these in a "structure emergency repair kit" and bring them to the tournament.

The Performance

At some point after you check in with the prep area appraiser you will be directed to have someone to return to weigh in to pick up your structure. Do not remove the seal from the structure container until directed to do so by an appraiser.

Once time begins, relax and enjoy yourself.

Glossary of Structure Terms

General Definitions of terms as used on this website.

Adhesive - Any material capable of creating a bond between two materials.

Brace - A piece of a structure that is designed to resist pressure.  It typically runs between columns and is less than vertical.

Buckling load-  The amount of weight required to cause a structure to fail.

Column -  A full height vertical piece of the structure that has the primary purpose of supporting weight.

Critical Length - The length where wood no longer bends but crushes.

Glue - Any commercially available adhesive material applied in a non-solid form capable of creating a permanent bond.  Often used interchangeably with the term adhesive.  Technically "glue" is a type of adhesive made by boiling collagenous animal parts such as bones, hides, and hooves into hard gelatin and then adding water."

Jig - A gauge, pattern, or mold used as a guide to the form of a piece being made.  They can be 2 dimensional or 3 dimensional.

Lamination - Gluing layers of wood together in order to increase strength.  Laminating two pieces of wood (wood-glue-wood) would be legal since the glue is used only to adhere one piece of wood to another.  Laminating two pieces of wood with a layer of glue on the outside (wood-glue-wood-glue) would NOT be legal in most challenges since the second glue layer would be considered a 'coating' on the wood.

Member-  A general term for any part of the structure, a column or a brace.

Stress (Force) - Stress is a force or pressure where one body or body part presses on, pulls on or pushes against another body or body part. It can also be a pressure that tends to compress or twist another body or body part.

Structure- the thing you have to build to hold weight.

Is there a Secet to Structure

Yes, there are probably lots of little secrets and tricks of the trade that teams have discovered through years of participating in the structure challenge.

Do I know what they are?

Not really.

My secret is simple and its in this box. (Click to open)

My "secret" is to build lots of structures. This box contains just part of the structures that were built and tested for one structure challenge.

See, I really don't fully understand all of the concepts included in the tutorial. What I do understand is that if I build a structure, test and analyze what caused the failure and then try to correct that failure that eventually I will end up with a pretty good structure. Making small changes in the design allows me to gradually zero in on a design that works.

Building lots of structures also helps to improve your building technique. It is like any other skill. The more you practice the better you become.

Good Luck and hope to see you at a tournament!