A question about glues

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

hornet driver

Well-Known Member
Joined
May 1, 2011
Messages
4,639
Reaction score
9
Here's the sitch, I'm going to lay up some balsa sheets as ply---3 layers-- after the layers are dry I need to wet warp the balsa. What kind of glue do you guys and gals suggest for the lay up process. It needs to be unaffected by the wet warp process. I thought about epoxy but it might be to brittle and give me problems, I have not used gorilla glue---moisture activates it. Thoughts , ideas?----H-------I did consider finishing resin. it stays pretty flexible in thin layers.
 
That's a great question. ...
I would use carpenter's glue, like TiteBond. ..
The wet warping process will soften it,,
but I don't think it will affect it in any other way...
after the warping the glue will dry just like it did the first time...
And for sure it's really strong glue....

Teddy
 
I would suggest to bend your balsa and laminate to get your curve. If you lay it up like plywood the you may have problems getting it to bend how you want. how thick is this going to be and how large? As for the glue, I think it would depend on how wet you are going to get the part. I would search the internet and do some tests before doing the final. Should be kinda fun.

https://www.pldaniels.com/flying/balsa/model-aircraft-workshop-howtos.html
 
Titebond is also fairly water resistant (TBIII is near waterproof), you may have to use steam to warp a panel put together with TB. I agree with the above poster, if you can laminate the piece on the curve since the finished balsa ply will be resistant to bending.
 
You will have much lower residual stress in the materials if you laminate the curved piece as recommended by those above. The result will be stronger overall than if you laminate and then bend.
 
Yeah,, I think you guy's are right...
After making the ply lay up and letting it harden fully it may not want to take the bend..
How about you steam warm moisten the wood
and glue it and bend warp it at the same time.....

Teddy
 
[video=youtube;7WAwuSK36Gw]https://www.youtube.com/watch?v=7WAwuSK36Gw&feature=player_embedded[/video]
 
Steam Heat Tunnel for bending. Easily made out of pvc pipe, electric hot plate and a pan of water.
NOTE: if you are laying the layers like plywood, balsa bending against the grain will put stress on the other layers when it's dry.
This type of laminating is typical with layers 10 mils or less with other hardwoods.
Gorilla glue is what's used for making larger blocks of balsa by balsa companies, I suggest that.
Clamping isn't really going to be an option here, you'll need a flexible vacuum chamber.
A better description of the shape you are trying to get would help me advise better.

Some basic knowledge can be found HERE
 
Last edited:
If you can figure it out I'd try to laminate in the bent condition as was said above. To get an idea of how much inter-laminar stress (fancy composites term for the amount of stress on the resin between plies) stack your sheets up unglued and bend them a bit, (you don't have to go the full curve you're doing) and notice how far the edges displace from each other. All that distance will be locked in by the gluing and that adds up to lots of stress. Hey you don't even have to use wood grab a thick book and curl the pages over and you'll see the same thing.
 
+1 on forming the curve, then laminating. You might also want to consider a layer or two of really thin ply, like 1/32" as an outer skin or inner member. Its a harder wood, and it's a ply (usually 3 play at this thinness), but still quite bendy..
 
+1 on forming the curve, then laminating. You might also want to consider a layer or two of really thin ply, like 1/32" as an outer skin or inner member. Its a harder wood, and it's a ply (usually 3 play at this thinness), but still quite bendy..

There's even a 1/64 ply for model airplane skin. Really thin and tough. About the only wood they can do this with is Birch
 
If you can figure it out I'd try to laminate in the bent condition as was said above. To get an idea of how much inter-laminar stress (fancy composites term for the amount of stress on the resin between plies) stack your sheets up unglued and bend them a bit, (you don't have to go the full curve you're doing) and notice how far the edges displace from each other. All that distance will be locked in by the gluing and that adds up to lots of stress. Hey you don't even have to use wood grab a thick book and curl the pages over and you'll see the same thing.

Yea I thought about that . It's the old compression ,regression conundrum. Warping out the core and then overlaying with the skins might be the best bet. I can build a jig first . then I don't have to worry about memory loss during the assembly process.--Unless I find the wine--- The 1/64 birch is a great idea for finishing. I'm willing to bet that it's a break even or better as far as weight goes(outer surface does not need to be glass smooth just no bad grain). For the record. This is for the Pterosuar build. It needs to be lite but strong and I'd like to lay the wing up as one piece. The span is around 3 ft+ and lateral warping is a concern( as opposed to span wise). Core warping also makes my question academic.But I DO appreciate the responses .I'll put that knowledge in the library for future use. Thank you all, now it's time to find Hobby Lobby and raid the wood pile !!---H
 
You might look into the long open time varieties of wood glue for your laminating work. Titebond III has about double the open time as regular TB and TBII.
 
IMHO, polyurethane, while it might work in theory, would be terribly difficult to use. For one thing you'd have to keep uniform pressure on the complex curve or risk getting bumps.
 
Back
Top