laminating balsa

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LW Bercini

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Since the right size stock is not available, I need to laminate some balsa together to approximate a complex shape. Afterward I will carve and sand it to the final shape.

What is the minimum adhesive I could use that would keep the layers together, but will not be so much harder than the surrounding balsa to make shaping difficult?

I'm thinking just old-fashioned white glue, but maybe there is some other glue that works better?
 
I recently made some 3/4 inch diameter balsa hemispheres by gluing up 3 layers of 1/8 balsa sheet, then shaping them with a file and some sandpaper. Used Elmer's Glue All, and didn't have any problems with the glue joints shaping weird because they were harder than the bulk wood.
 
I made the nose cone for my Smurf rocket by layering 1-inch balsa boards into a cube and then shaping. Used regular carpenter's glue and pressed over night to dry. I accidentally twisted off one layer with a chisel, but I'm not worried about regular use.
 
I'm thinking just old-fashioned white glue, but maybe there is some other glue that works better?

White glue would be my bet as well. I think it would work, as long as your balsa is not super light weight (like "contest grade" 4-6 lb stuff), and you use a sanding block.
 
As many threads here have gone into, any PVA glue (white glue or yellow wood glue) is stronger than the balsa (with the possible exception of School Glue, but I'm skeptical that is an exception) so strength is not an issue. And they're all easily sandable and knife cuttable. White may be a little easier to work with, so I'd go with that.

Which seems to be unanimous.
 
I routinely laminate balsa for helicopter rotor stops in order to take stresses 90 degrees apart.

Also did it for the Squirrel due to the weird shaped fins

https://www.rocketryforum.com/threads/the-squirrel-2-almost-perfect-flight.146038/
Lessons learned.

Balsa with white or wood glue applied to a broad side warps LIKE CRAZY, the pieces will curve away from each other. IMO you must have some thing flat to keep them together. I wrap them in wax paper and stick them in a nonglossy paper book overnite. You may consider sewing them together at the edges, they sometimes slip a bit.

I don’t have electrical cutting equipment, just a drill and a Dremel (actually a black and decker, but works the same.)
I tried gluing wood then cutting to shape, found it REALLY hard to cut with a blade (which kind of goes along with strength.). So I cut three pieces, one orthogonal grain direction, just a bit large, and after gluing sand to fit.
 
I would use zpoxy or Bob smith finishing epoxy. It sands easier than wood glue and works great for papering and finishing balsa. It also cures quicker when laminating under pressure away from oxygen.
 
Since the right size stock is not available, I need to laminate some balsa together to approximate a complex shape. Afterward I will carve and sand it to the final shape.

What is the minimum adhesive I could use that would keep the layers together, but will not be so much harder than the surrounding balsa to make shaping difficult?

I'm thinking just old-fashioned white glue, but maybe there is some other glue that works better?

Sig-ment from SIG https://sigmfg.com/products/sig-sig-ment?_pos=1&_sid=f12740211&_ss=r

Sands easily, much easier than white glues. Strong enough to be used to glue balsa sheets together edge to edge, so it should work much better in your situation, since you’ll have far more surface contact area.
 
Balsa with white or wood glue applied to a broad side warps LIKE CRAZY, the pieces will curve away from each other. IMO you must have some thing flat to keep them together. I wrap them in wax paper and stick them in a nonglossy paper book overnite. You may consider sewing them together at the edges, they sometimes slip a bit.

Whenever I laminate balsa I wet the backside of the balsa with water and let it begin to curve. Then apply glue on the front side and press the pieces together. The moisture levels will be balanced on both sides and help prevent long time deformation. Then put the balsa under weights for at least a day. Then sand slightly to ensure a even surface.
 
Whenever I laminate balsa I wet the backside of the balsa with water and let it begin to curve. Then apply glue on the front side and press the pieces together. The moisture levels will be balanced on both sides and help prevent long time deformation. Then put the balsa under weights for at least a day. Then sand slightly to ensure a even surface.
Great Idea. I wonder if you could paper it at the same time you "plied" it? The ply would add strength in multiple planes of stress, the paper would add some strength in any plane and also reduce the cosmetic filling/priming required on balsa finishing.

One problem, you may not have the final product full smoothly shaped, which is kind of important BEFORE papering.
 
Great Idea. I wonder if you could paper it at the same time you "plied" it? The ply would add strength in multiple planes of stress, the paper would add some strength in any plane and also reduce the cosmetic filling/priming required on balsa finishing.

One problem, you may not have the final product full smoothly shaped, which is kind of important BEFORE papering.
I think papering or filling can be left as a second/third step after the laminating and after shaping shaping to avoid having too many things going on at the same time. I'm a patient guy and I don't mind a process that takes me several days to achieve the final result.
 
Hey LW, I also favor using epoxy, except that I'd use West 105/205 or Aeropoxy laminating epoxy for this - they sand a lot better than BSI. The advantages are that the zero water content suppresses warping, and it's ready to sand much sooner since you don't have to wait for all the water to escape a thick stack of material.
 
Thanks Eric. I've never heard of this product before. Is it similar to Ambroid?
Yup, only much easier to get (I think Ambroid is now OOP?). Dries quickly and doesn't remain tacky (I think Ambroid did)? I don't believe it's water-based so there shouldn't be any warping issues -- at least I haven't noticed any.
 
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