25 Bridge Building Tips

By on January 2, 2006

1. Humidity affects the weight of your bridge. Keep your bridge in a closed container with a few grains of rice. or some silica gel packets.

2. Go easy with the glue bottle. As a general rule of thumb, if you can see it than you are using too much.

3. Keep your hands clean! Oils and grease from your skin can ruin your glue joints.

4. Perfect practice makes perfect. The more bridges you build, the better your construction skills will be.

5. Keep your bridge from twisting by using lateral bracing.

6. An L-beam is more efficient than a square, but harder to build.

7. Balsa wood comes in a wide range of densities and stiffness. Weigh each piece that you buy.

8. It is cheaper to buy Balsa in sheets and cut your own wood strips.

9. It’s still true, measure twice and cut once.

10. Keep a log of every bridge you build. Record notes and dimensions; you won’t remember later on.

11. Try to videotape testing your bridge. You may get a clue on what failed first.

12. Always keep safety in mind when using sharp tools. Most mistakes are made when you aren’t paying attention.

13. By cutting a piece in half, you more than double its strength in compression.

14. Good lighting when working will help you perfect those little details.

15. Always test your bridge before taking it to a competition, but leave enough time to build another.

16. Draw out your bridge on graph paper to make sure that it is symmetrical. I prefer the 11″ x 17″ graph paper.

17. Different trusses have different ways of spreading out the load.

18. Wood has about the same strength in tension, no matter how long it is.

19. CA glue is a fairly strong, light, fast-drying glue used by many builders.

20. Balsa wood sands very easily. Be careful not to sand off too much.

21. You can mix wood glue with water to cut down on weight. Doing this also helps the glue to seep into the wood, creating a stronger joint.

22. Remember to close your glue bottle when you are done using it.

23. Basswood will bend easier than Balsa wood. Try steaming or soaking your wood to help it bend.

24. Use Lap joints whenever possible to get the best strength.

25. What you want to look for in glue: drying time, price, weight, and strength.

These bridge building tips will give you a head start when you start designing and building your model bridges. These tips come from my years of experience starting from my time in the Science Olympiad competition and continuing beyond building for fun. Disclaimer: these tips are my own opinion based out of my experience. Other builders might have different views and we might not agree. I encourage you to try things out on your own and decide for yourself what is the best way to build a bridge. Who knows, I could have been wrong about something.

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27 thoughts on “25 Bridge Building Tips”

  1. is it actually very hard joints when mix water to the glue?

    By subhash -- September 28, 2016
    • The water helps the glue soak into the wood a little more.

      By Garrett Boon -- September 28, 2016
  2. we are doing this in my class… its so cool! I will wright back what happens soon! Thanks for all of this information!

    By xavier zuniga -- October 15, 2013
  3. Can testors glue (for metal and wood models) be mixed with water?

    By emma -- February 27, 2012
  4. I once built a bridge for an Odyssey of the Mind competition, and now I have to build one for an Engineering class. I remember my OM coach drying out the bridge in an oven. She set the structure on a cookie sheet and then sprinkled silica gel on the sheet before baking it. I don’t remember the specifics but would like to try this trick for a better efficiency ratio. Do you know anything about this weight-saving method?

    By Erik C. -- February 14, 2012
    • Erik,

      What I have heard is that baking a bridge in an oven has only temporary gain in weight loss. The moisture that is removed by the oven is quickly replaced by the humidity in the air. Also, you have to be careful about the heat level and what glue you are using.

      By Garrett Boon -- February 15, 2012
  5. Random factoid for those interested,when you put a beam in compression the formula for the weight it can hold is P = c * (E*I)/L^2 where P is you load and L is the length. Making a beam half as long actually increases the weight capacity by 4. Similarly cutting it down to a fourth the size increase the weight 16 fold.

    By christopher pepin -- May 3, 2011
    • This was very informative and helped me very much. I am very grateful. 😀

      By Raelynn -- November 15, 2011
  6. i need blueprints and fast! Garrett Boon can you help me obtian them,please.

    By garrett -- December 6, 2010
    • You can get blueprints at my store:
      https://www.garrettsbridges.com/store

      By Garrett Boon -- December 6, 2010
      • Dude your a genius. How will laminating the bridge effect the efficiency ratio?

        By Kahler Science Olympiad -- March 7, 2015
        • I’ve heard differing opinions on laminating. But for Science Olympiad in particular, I think if you look at the winning bridges you will see they don’t laminate.

          By Garrett Boon -- March 8, 2015
  7. how do you build a suspension?
    I’ve been to the summer camp to learn those stuff but they didn’t told me how to build a suspension??

    By bowen zhan -- October 15, 2010
  8. OMG I have to finish my bridge before this friday =O im scared XD Will my bridge make it?? :O

    By Fidel -- May 23, 2010
    • It will just calm down and take a deep breath and pray for the best

      By Kayla Barhorst -- December 10, 2015
  9. Any tips when using squared cross section popsicle sticks to avoid uneven beams or elements (because of different cross section dimensions between one stick and another)? And… should I cut sticks ends in angle to exactly fit between other 2 sticks forming an angle?

    By Fidel -- May 4, 2010
    • Okay so let me get this straight that this will help me to build a home made bridge?

      By Kayla Barhorst -- December 10, 2015
  10. Wouldn’t putting water into your glue dilute it therefore making it weaker???

    By Michael -- May 2, 2010
    • yeah… it will!

      By yonu -- May 20, 2010
    • No, if it is wood glue (Elmer’s, Titebond) then adding a percentage of water will actually increase the strength of the joint. The water thins the glue, making better able to seep deep in the wood, creating a better joint.

      By Garrett Boon -- May 21, 2010
      • you have to dry it first..

        By bowen zhan -- October 15, 2010
  11. what is the best glue to use for making the bridge. I was using crazy glue it doesnt seem to be working.
    thanks

    By ann -- January 8, 2010
  12. hey, that post really helped! im doing research for a secme competition!lol, thanks!

    By Harmony -- October 19, 2009
  13. THANKS! This was super helpful, I am doing a model bridge for science olmpiad and i hope these tips work.

    By Jenny -- October 16, 2009
    • Same here, im going to state this year hopfully win

      By mike -- March 20, 2015
  14. i like this, thank you very much. this is so cool

    By bob -- September 10, 2008

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