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Laminating balsa fuselages sides together

Old 01-01-2020, 11:38 AM
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j3df
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Default Laminating balsa fuselages sides together

I'm building the Balsa USA 1/4 Scale Piper J-3 Cub kit. The primary adhesive I will use is Titebond II. What glue would you recommend to laminate the balsa fuselages sides together.

Using this method How to Make Your Own Plywood
, I was able to get good results with Gorilla glue (polyurethane). However, I'm having second thoughts about GG - I'm wondering how it will hold up in the long run (like 30 years from now). Would a thin layer of 30 min epoxy be a better choice?

- Josh


(2) 1/8 in. balsa sheets laminated together

Last edited by j3df; 01-01-2020 at 12:18 PM.
Old 01-01-2020, 03:01 PM
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A. J. Clark
 
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Use the titebond sparingly and you will be good . Pin it so it stays lined up and some weight on it until it drys. It will last for years.
Old 01-01-2020, 04:43 PM
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j3df
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Should the weights just be placed around the edges? And what do you normally use as weights?

I'm worried about the glue drying in the middle and warping. With the GG, I sandwiched the balsa sheets between two boards and places weights on top of that.

I am going to practice with some spare sheets! Thanks for your help!
Old 01-01-2020, 09:35 PM
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tedsander
 
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Use anything you have to pile on top, covering the whole area as completely as you can. If some of the edges stick out a little, it will be fine. If it was me, after thinly coating one surface, I would apply the second piece on top. Then angle a few pins in along a couple of the edges so it won't slide around. Cover the top with wax paper or plastic film (so if any glue does squish out, you don't glue your weight to the wood). Finally, find something that will fit over it as well as you can, but clears the pins, if needed. Then stack whatever you have on top - lots of books, or anything else. GG could tend to push things out of alignment as it foams and cures. Titebond will last forever. As will epoxy, but it adds weight more than Titebond.

If you really want to get fancy, coat both surfaces with Titebond and let it dry completely. Then put them together, and fire up your covering iron to max heat. Then you can iron one piece of wood down on top of the other. The heat polymerizes the dried glue, making a bond that will never let go. Usually done to apply thin balsa "skins" to foam wings, but would work here too. Just go slow, to give the heat time to penetrate, given it is thicker than the 1/16th used for wings.
Old 01-02-2020, 01:39 AM
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j3df
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I will try both techniques. The second way sounds intriguing! Thank you!

Old 01-02-2020, 05:17 AM
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Maybe a bit over kill but if one had access to a vacuum baggin setup, I have done thus very thing by applying a very thin coat of epoxy laminating resin to one side, put the two together with tape on each corner, place on a flat non porous surpace, outline with sealant tape and place bagging film with vacuum port over the part and pull vacuum. Sounds like a lot of work but in reality would go quickly. Once you have a vacuum system, you find many uses for it.
Old 01-14-2020, 10:31 AM
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j3df
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I tested the second method described by tedsander. Using a brush, I coated the balsa with Titebond and then let it dry. The balsa bowed up but slowly returned to its original form as the glue dried. I was able to iron the two sheets together and the final result was pleasing.

Is it normal for the balsa to become bowed after the glue is applied? I'm worried about it warping down the road.

Thanks,
Josh
Old 01-15-2020, 09:57 PM
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DGrant
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It's not uncommon for balsa to bow, although there's factors that can either prevent it or amplify it. Our goal is to prevent it though. That's why it's suggested to weight balsa down flat when laminating, that's about the only guarantee we have for the flattest outcome possible. The only way balsa will warp later down the road is by being exposed to moisture or elements/climates that are extreme. Don't leave your model in a damp garage, and don't leave it in a 140 degree garage or car for any length of time... and when you're out for a day of flying, keep it in the shade or covered in some way. Of course that makes sense though right. If your skin is hot/cold/wet/moist your model is too... LOL. So keep your models and your pets comfy... and neither one will bow or warp.

I've laminated parts very similar to what's described here. I've used slow cure epoxy, rolled on with a weenie roller from the local paint department, then set the assembly on the flattest table I have and stack several 12"x12" pavers on the whole thing, then forget about it for a day. The components come out very straight, and very solid/stiff.. and have lasted many years.
Old 01-22-2020, 10:23 AM
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I am no fan of CA glue but when it comes to laminating, it's hard to beat. I would simply put down thick CA on the outer pieces then place the inner one over it and be done in a minute. I use Titebond all the time and laminating is not it's strong point due to warping. I built a stab and laminated the balsa skin over the framework only to have bad warping. Built a second one more carefully and it did the same thing. Built a third (mad as heck by now) in about 10 minutes using thick CA and straight as an arrow.

I've also done quite a bit of sheeting using the iron on method and tite bond. It works but it's messy and very slow. The best way to dry the glue is with a heat gun. You want it dry but rubbery. If it dries overnight and becomes hard, you won't be able to iron it on.

carl
Old 01-22-2020, 02:04 PM
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For weighs I use plastic bags filled with dry sand. Also be very careful using CA if you bethe the vapor it WILL mess up your sinuses!!!!! I can't be around it at all. There is oderless and it's fine to use. It costs more but it's worth it.
Old 01-30-2020, 07:13 AM
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Slow cure laminating resin, flat table, vacuum bagged to table or in an vacuum envelope. It doesn’t get better than that.

Bob

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