25 Bridge Building Tips
November 29th, 20061. Humidity affects the weight of your bridge. Keep your bridge in a closed container with a few grains of rice.
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.
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December 1st, 2006 at 2:47 pm
Not only the weight, but also the length of a bridge. I don’t think we will forget the day a bridge got DQ’d for being too long after entering the wet air of the East Coast.
December 2nd, 2006 at 12:29 pm
Ah, the effects of humidity on the wood. Humidity changes especially effect Balsa wood.
What year was that, Skystrider? I can’t seem to recall a maximum length rule ever. Unless it was the year you could build the bridge extending below the top of the test supports. In which case, you did have to build the bridge extremely well, and a swelling due to humidity would cause the bridge to no longer fit inside the hole, which would then cause you to be DQ’ed because the loading block was higher than 1mm above the top of the test supports.
Ack, my days in Mission affected my sentence writing capabilities.
January 25th, 2007 at 10:50 am
Hey Garrett,
I had a question for you. I am in a bridge contest for school, as extra credit. The requirements are that: you use only 3/32 inch cross-section bass wood, mass is no greater than 25 grams, span a gap of 300mm, max width 80mm, and height 200mm. Our judge has decided that, instead of measuring the bridges by overall weight held, they will divide the weight held over the weight of your bridge (weight held/mass). The winners from last year had very light bridges, simple small rectangle shaped bridges. Would this be optimal under the circumstances, or is there another way to help negate the feather-weight’s advantage?
Thanks,
Matt
January 25th, 2007 at 3:26 pm
Here are the exact specifications, in case my description was a bit confusing
tinyurl.com/9hq63
February 14th, 2007 at 9:19 pm
Why does the compression strength in wood increase as the stick is shortened, but the tension strength is relativly the same?
Also, if the compression strength increases as the sticks becme shorter, then should I have made a bridge with an arch that was one bent stick because there would be infinite fragments of stick making the arch super strong, or was putting my very curvy arch into segments stronger.
Later, I have a very specific question on if my bridge was good. I read somewhere that the effeciency varies with the restrictions.
Please respond…
February 28th, 2007 at 7:53 pm
hey thomas, to answer your question about compression and tension- think of this. You must know that compression is when the wood gets squished together to consume less space. When you have a longer piece of wood and try to compress it, it will flex in all different directions with minimum force. If you try to compress a two inch piece of wood, it will take much more force to make it snap, or flex. As for tension, wood will have the strength of the grain. All throughout the wood, the grain is the same kind and will break with the same amount of force. So… if you pull on a 1” piece of basswood and a 1′ piece of basswood, they should break at the same weight. I don’t know what you are talking about in the part with “infinite fragments of stick.” Hope I helped.
March 1st, 2007 at 10:02 am
Im making a toothpick bridge you didnt tell any thing about that. But i got a litle info thakns.
March 13th, 2007 at 9:43 am
I like the info it helped out alot thanks.
April 3rd, 2007 at 1:11 pm
i love garrett you are my idol!!!!!!!!!!!! you are soooooooooooooooo cool!!
with your bridge buildyness!!!!!!!!!!!!!!!!!!!!!!!!!!!
love ya
April 20th, 2007 at 6:02 pm
Hey,
I love what you’e doing!
Don’t ever change and best of luck.
Raymon W.
May 14th, 2007 at 1:31 pm
Hey I’m doing a project at school for building popsicle bridges. I could use a lot of help. My bridge 20 inches long, 8 inches off the surface, and 10 inches wide.
May 25th, 2007 at 1:12 pm
i need deasigns for my sckool project:)
July 19th, 2007 at 3:18 pm
it was antastic
December 19th, 2007 at 9:26 am
Thanks for all the info! It really helped me out.
Thanks for all the convience-!!!
January 2nd, 2008 at 10:16 am
This helped me alot….thanks a ton garrett bridges!!!!!!!!
January 2nd, 2008 at 11:34 pm
please help me to construct a model of Aircraft Hangar with popsicles
January 3rd, 2008 at 3:24 pm
these tips really bhelped me…i am compeating in a natinal chapionchip. If i win, i have to thank you Garrett Boon. I have some really neat pics of the New River Gorge Bridge in WV. I live about 20 miles from it. Would you like to see them? Also I am going to get my son a bridge building kid for his birthday. What kind should i get him? Thanks Garrett i aprriciate it.
January 3rd, 2008 at 3:28 pm
you guys are awesome…you helped me win my school final.. thanks garrett
January 3rd, 2008 at 6:04 pm
Kelton, I would love to see more photos of the New River Gorge Bridge. You can send them to me at webmaster [at] garrettsbridges.com
January 4th, 2008 at 8:23 am
how many pics do you want.. i have one when im in the river looking up at the bridge.
January 4th, 2008 at 8:33 am
can you explain tip #1 to me more in depth? ( . )Y( . )
January 4th, 2008 at 8:35 am
I love you Garrett thanks for all the help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
January 4th, 2008 at 9:56 am
Can you use elmers glue as a bondage adhesave?
January 4th, 2008 at 10:02 am
In tip one, does the rice absorb the moisture?
January 4th, 2008 at 10:16 am
For the money can you buy cheap wood instead of bass and balsa wood?
U Should build a model bride buissness. U would make allot of money
Can you cut your own wood?……What demention should i make it
Kan you write back plz…thanks garrett
January 4th, 2008 at 12:08 pm
How many grams “on average” does your bridges weigh
January 4th, 2008 at 12:11 pm
I have told all my friends about this website. This page is so cool.Thanks for all the help
January 4th, 2008 at 2:27 pm
Duke and Brady:
Yes, the rice is supposed to absorb moisture. This will cut down on the water weight of your bridge which will increase the efficiency score. This tip is mainly for those who are in a competition where the weight of the bridge is measured in .1 or .01 of a gram. It won’t make a ton of difference, but it will help a little.
Gup:
My bridges have no average weight. Each bridge was built for completely different specifications and cannot really be compared to each other.
“Me”:
There is really no other wood worth the money besides Balsa or Basswood. And yes, you can cut your own pieces out of sheets of the wood.
Humphrey:
Elmer’s white glue is not very strong and should not be the glue of choice for a model bridge.
January 4th, 2008 at 5:18 pm
Kelton, I’ll take as many as you want to send.