Choosing the Right Glue
The glue you choose to use on your model bridge (or model airplane) can make or break your structure. I’d venture to say that glue choice is just as important as your wood choice, which makes it pretty important. If you build your bridge with a weak glue, then no matter how good the design is your bridge will not perform well. This article compares and contrasts different types of glues, showing the strengths and weaknesses of each so that you can make an informed choice for what glue to use on your bridge.
What you want to look for in glue:
- Drying time
- Price
- Weight
- Strength
- Ease of Use
CA Glue
This is a very common glue used for a variety of projects. It dries in seconds, like super glue. It is also widely available. Numbers of hobby stores and online companies sell it. However, it is not cheap. CA glue can be bought in three types: thin, medium, and thick. The thin stuff is very light, but not especially strong. The thicker stuff is heavier, but stronger. I have known people to build extremely efficient bridges using CA glue. I do know that I will never use regular super glue after seeing how much better CA glue is. Purchase Pro CA Glue 1/2 oz Thin
Elmer’s Carpenter Wood Glue
This wood glue is very well known and well used. Elmer’s makes a solid glue, although I see it as on the heavy side. If you want to go with a good glue, then this is a good choice. Remember that with wood glue, you can actually get a stronger joint by adding a little bit of water to the glue. This allows the glue to seep into the wood, creating a stronger joint. Buy Carpenters Wood Glue by Elmers from Amazon
White Elmer’s glue
This glue can be bought anywhere, and is relatively cheap. It usually dries in 30 minutes, which is somewhat long for building bridges. Also, it is not very light or strong. I have come to the conclusion that white Elmer’s glue is not a good choice for model bridge building. Buy Elmer’s White Glue
Titebond Wood Glue
This glue bonds balsa wood very well. It also can be found in most hardware stores. However, it is fairly heavy. Many people mix water with the glue to cut down on weight. It dries fairly quickly, less than 10 minutes in small amounts. Elmer’s wood glue also provides a strong joint. The reason I don’t use this glue is because I don’t think that it is the best. But it is still pretty good. Titebond III Ultimate Wood Glue, 8-Ounces
Epoxy. The first glue I ever used in building model bridges was 30-minute epoxy. I liked it because it was very strong and could be bought at many stores. Epoxy comes in several different “setting times”. You can get 90 second, 5 minute, 15 minute, 30 minute, and up to 4 hour epoxy. The bad thing about epoxy is that you have to mix it. I had trouble mixing it correctly in small amounts. I ended up wasting a lot of glue mixing a lot of it at once. Also, epoxy is not very light. An interesting feature about epoxy, it heats up when curing. Sometimes it can get quite hot. Purchase PermaPoxy 5 Minute General Purpose Epoxy
Special Glues:
Probond
This is polyurethane based glue and is super strong. It is a cousin of Gorilla glue. It is not light, but you don’t have to use very much of it. However, the only place I know of that sells it is a local Ace Hardware store. It is also very expensive, which is why I don’t use it much anymore. It takes at least 4 hours to set, which is a really long time to wait. I still keep a bottle of it on hand, because it works for about anything. Elmer’s Probond Wood Glue 16-Ounce
Weldbond
This is the glue I have switched to, after seeing it at good ol’ Ace. It is lighter than Probond, almost as strong, and a whole lot cheaper. It looks a lot like white Elmer’s glue, but dries completely clear. It sets in no more than 30 minutes, but often in less than 10. Weldbond Universal Glue 4 oz Bottle
If the type of glue you use is not listed, shoot me an email telling me about it at webmaster@garrettsbridges.com
Chart Comparing Glues
| Wood Glues | CA Glue | Probond | Weldbond | Epoxy | White Elmer’s | |
| Strength | 3/5 | 4/5 | 5/5 | 4/5 | 4/5 | 2/5 |
| Price | 3/5 | 2/5 | 2/5 | 5/5 | 3/5 | 5/5 |
| Weight | 3/5 | 5/5 | 2/5 | 4/5 | 2/5 | 3/5 |
| Drying Time | 3/5 | 5/5 | 2/5 | 4/5 | 2/5 | 3/5 |
| Ease of Use | 4/5 | 3/5 | 3/5 | 4/5 | 2/5 | 5/5 |
| Average | 3.2/5 | 3.8/5 | 2.8/5 | 4.2/5 | 2.6/5 | 3.6/5 |
Obviously this chart is biased to my own experience with these glues. Please share your thoughts and experiences by leaving a comment.
Additional Resources:
Oh… Well, thank you anyway for taking time to respond to my question
. What glue would you recommend for balsa wood? Thanks SO much.
What about loctite superglue? For balsa wood?
Jennifer, I have not had any experience with Loctite super glue, so I cannot speak as to its properties.
I tend to use a hot glue gun for my model. It isn’t very light, but you don’t need much and it is very strong. I used balsa wood.
I love using just regular wood glue for building a bridge. It is so easy to use and it doesn’t add a lot of weight to your bridge if you know how to use it correctly. It is made for wood so why wouldn’t you use it? That is what I would recommend for anyone who is or wanting to build a model bridge.
Sorry i did not read the policy anyways i am going to the Michaels craft store and i am wondering what the best type of wood glue is for my project?
Forrest, I do not have plans for that popsicle bridge because I did not actually build it. Thanks for pointing out my typo. It is fixed now.
Hello my name is Forrest Rogers and for my 9th grade science project I have to make a Popsicle stick bridge that’s dimensions are 1 foot long and no height or width requirement( I have not found out how many Popsicle sticks we are issued but I am thinking about 100.)
I am thinking along the lines of your bridge that you built on this web site.
http://www.garrettsbridges.com/photos/popsicle-bridges/coolest-popsicle-bridge
could you please give me the design of this bridge it would be appreciated and I would tell everyone about your great web site.
Also I could help notice that in the Other Glues section that u have a typo. [edited by admin due to comment policy...thanks for pointing it out]
* I can only use wood glue.
* Whats the strongest wood glue?
* Were can I get it?
Thanks, Forrest Rogers
Arianna, here are the answers to your questions.
1. Yes, both affect the bridge. Some glues are stronger than others. If you test your bridge without letting the glue dry properly, then obviously it won’t hold as much as it could have. Usually 24 hours is enough time for any glue to completely cure.
2. It is correct that a Warren truss looks like a bunch of zig-zags. But what makes the Warren truss strong is simply the fact that it is composed of triangles. The triangle is the strongest shape to use on a model bridge.
3. There is a difficult concept behind this answer. Part of it is related to the actual construction. If your bridge is not symmetrical, then probably the overall construction of bridge is not the best. A symmetrical bridge also has a greater capacity to distribute the weight throughout the bridge.
4. I think you are talking about mitered joints. The reason a mitered joint is stronger than a regular end joint is simply the added surface area for the glue. However, an even stronger joint to use a lap joint.
5. Every bridge will break eventually if enough force is applied. Most bridges do have weak points, but those weak points are engineered to be so strong that they will not break under normal circumstances?
6. The weight of the wood is not directly related to the strength of the bridge. Instead, the density and stiffness of the wood are more important.
7. Your best bet is to use all of your allocated 16 grams. I can’t tell you the best design to use, because that is usually a matter of debate. Use a standard truss as they are very solid designs.
Hey garrett boon. I was wondering if you could answer a few questions for me. Okay here it goes… 1) When building a bridge , does the type of glue used effect the outcome of the bridge, the amount of time given to let the glue bond with the wood, both, or neither? 2) Since a warren truss bridge’s design is basically zig-zags, does the zig-zag design help distribute the amount of pressure put on the bridge when weight is applied or does the design have a different purpose? Why or why not? 3) Why is it so important that when building a bridge that each side should be as symetrical as possible? 4) When building a bridge, why does connecting to ends of wood with accurate angles, instead of regular flat ends, help the bridge withstand more pressure? 5) Does every bridge have weak points? If so, why? 6) Does the weight of the wood used in building a bridge affect the amount of pressure the bridge can withstand or is it just the design you use? 7) What is the best design for a bridge if the goal is to hold as much weight as possible but the bridge is to weigh no more than 16 grams? Please answer these questions ASAP. Thanks for your help.
Christopher, my expertise is not in toothpick bridges. But I would recommend CA glue over Weldbond for a toothpick bridge.
Hey Garrett,I want to build truss bridge with glue and toothpicks.otherwise,the bridge must have a mass less than 50 grams but 30 cm long ,4 cm wide and 5 cm hight,at least.what I gonna do?which kind of glue should I use, CA glue or weldbond ?By the way,the bridge must hold the weight about 400 times compare with its mass.What I gonna do,should I build a truss bridge,Kingpost,queenpost or X-Herrn bridge?
Hey Garrett, I tried using Weldbond but because of its slow setting time, I want to try using CA glue. Would you recommend just regular Super Glue or Super Glue Gel? The “minimizing weight while gluing” article in additional resources said to use the “thin stuff” but I don’t know whether to use the regular (liquid) one or the no-drip gel one because even though it says that wood works best with the gel, it might not be the best choice.
Hey, my name’s Curtis and I was wondering if you could help me out. I have a lab for my intro to engineering class and the task is to build the bridge with the highest load-to-weight ratio. We are required to use Forster Mini Sticks (I believe these are it, http://www.hobbycosf.com/fomist50.html) and Elmer’s “Glue-All” Multi-Purpose Glue. It must carry at least 1250 times its own weight. It must span a length of 250 mm and be no more than 100 mm wide. And the all-time record in the class is 4400:1. It is being tested using a three point bend test on a fixture Instron testing machine. Do you have any recommendations on the type of bridge I should use? Specifically, are there any I should avoid or are perfect based on the size of the sticks? Since I have to use elmer’s glue what can I do to strengthen it, maybe a different joint design, someway of drying the glue that creates a stronger bond. You advice would be greatly appreciated. Thank you.
First Timer, thank you for your comment. What do you mean when you say the glue had not bonded after 4 hours. By that time the glue should have “set”. That means the glue will be starting to get hard but it will not be full strength yet. Krazy glue is the only glue you mentioned that will have cured in a very short time. The others take 24 hours to reach full strength.
I would caution against combining glues. Sometimes the chemicals in different glues could create a very harmful mixture.
Well for my science class we were given the option to do an experiment or build I a bridge I chose the latter of the two. I followed your instructions about buying sheets and cutting and I was able to set up a jig to cut the pieces i needed and everything was going great I had my sketches on graph paper and supplies next to me my hands were clean but when i went to to glue my first pieces together to build the frame of my K-Truss ( I used Welbonde but also I didn’t mix it with water because I am not sure how too) and i started to glue the first two joints and they didn’t work so i decided to wait 4 hours for it to bond. After Four hours i checked in it still hadn’t bonded so i decided to use some Elmer’s Carpenter glue. Same result as the previous. Then i tried plain old glue (paste). And after a that on the verge of losing it I pulled out extreme adhesive paste and Krazy glue. And surprisingly when i combined them it worked but not that well. Could you please give me some advice about glue also if it helps the requirement are as follows for:
2.38 mm balsa must weigh 16.0 grams or less base must be 45.0 cm horizontal opening must be centered and a with a width of 26 cm or more must have a central vertical opening 8 cm or higher and spanning the width of 26 cm or more the height of the bridge must be 13 to 25
and width of the bridge must be 11 to 12 cm at the base but there is no limit at the top.
-thank you very much for all the help-