This discussion area is for basic structure building concepts. Not intended for advanced concepts.
*Good Example: Balsa can bend with the addition of boiling water.
*Good Example: Triangle is the strongest shape for most applications of bracing.
*Bad Example: Balsa can hold X pounds under these conditions.
*Bad Example: Use this shape for this application.
Basically I want you to think a design through with the basics instead of someone else thinking through your design for you.
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Post by huskers4ever5 » Sat Apr 22, 2006 10:55 am

I am working on an honors physics project of making a balsa wood structure/ tower. We have used super glue and wood glue (containing cyanoacrylate) so far. We are thinking of using gorilla glue. Any suggestions would be great. We have the permission of our teacher to consult outside help, so don't worry about any giving information (since it is allowed).

a little extra info: our structure is to be made of 1/8 by 1/8 balsa wood
-no more than 18.5 g (mass)
-between 20.3-21.59 cm (height)
- must be open at least 5.08 cm (diameter)

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Location: Grand Rapids, MI


Post by ClarkInMI » Mon Apr 24, 2006 10:23 am

I know of many in OM that swear by Gorilla glue, and an equal number that swear at it. My comments are chiefly around workability of the glues you're using. Gorilla glue is a very good glue for bonding wood as it has perhaps the best penetration into wood pores of all the glues you are considering. This comes from it's characteristic of foaming and expanding when curing. It literally forces its way into the wood. This expansion also makes it ideal for glueing two surfaces that are rough, it will fill gaps.

Unfortunately, this characteristic is also a detriment when it comes to cleaning up as the excess glue must be removed if it will impede the attachment of other pieces. This is made more difficult by the shear hardness of the cured glue - it is much more difficult to sand off than say excess carpenter's glue (an aliphatic glue). Also, like aliphatic glues and epoxies, there is a long cure time which requires clamping the pieces together to ensure a good glue joint and the passage of a fair amount of time. Either requirement can also be a detriment if you're trying to get something built quickly.

As far as ultimate strength of the joint the real determinant is if it is stronger than the wood itself. In other words, when a joint fails is it because the glue failed or the wood gave way? In all cases with the glues discussed here a properly glued, clamped, and cured joint will fail because the wood gives way. The only real deciding factor of what glue to use must be driven by consideration of the glue characteristics for your building needs.

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