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Old Apr 16, 2007, 12:11 AM
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Help!
laminated wing tips

I've been laminating wing tips for R/C oldtimers from 1/16x1/4 balsa for some time. My usual procedure has been to soak the 1/16x1/4 strips for about 24 hours, then laminate them with full strength aliphatic glue wiping as much of the water from as possible from the strips with paper towels before applying the glue. The problem is that when the laminates are dry they are not well glued together and require the use of CA glue to make them stable. It works OK but it requires two steps to complete the process. Anyone out there have a better method that will give a usable laminate with only one step??


Thanks, John
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Old Apr 16, 2007, 04:19 AM
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My results are the same as yours.
I recall an article where the author formed each lamination by pulling it around the base of a hot soldering iron (95 watt). Seems they were almost dry after forming.
Would make gluing more straightforward.
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Old Apr 16, 2007, 04:24 AM
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Old Apr 16, 2007, 04:34 AM
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Old Apr 16, 2007, 04:45 AM
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I've used thin CA, which works. But leaves a brittle residue.

Probably the better approach is to make up the laminations from sopping wet ammonia drenched balsa, and then let them dry out overnight. THEN glue.

If you make a well oversized former from balsa, ply or MDF, and use lots of rubber bands round it to keep all in place, you should be able to make a double width pair that can sliced in half and sanded to get a precise matching pair of tips.I have found ribber bands to be very good with sheeting curves..spreads the load far better than pins etc do. Tape works as well..
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Old Apr 16, 2007, 05:35 AM
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Old Apr 16, 2007, 06:05 AM
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I have done lams on verticals, and rudders as well as wing tips using Titebond yellow aliphatic resin and very rarely have I experienced voids or delamination

I do not soak my wood more than 30 to 45 minutes and I start out with very hot water

I think your problem may be that you are soaking the wood too long

Also I glue up the individual lams then slide them back and forth to distribute the glue evenly when adding them to the " stack "
Once I have my 3, 4, or 5 layer " stack " assembled I then stretch and form the lams around the form and hold in place using pins and blocks to hold in place. Hope this helps,

Roger aka GIFLYRC
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Old Apr 16, 2007, 07:15 AM
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I've done mine using thin CA and no soaking. They're done instantly, and sand fairly easily.

This is for 1/4 scale, however. The tips are large, with a relatively mild curvature.
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Old Apr 16, 2007, 08:18 AM
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I agree with vintage1, I just use an aliphatic (usually Titebond II) with rubber bands around a form and never have any voids. On very large structures, instead of rubber bands, I use a mating surface to clamp the laminations in place until dry but that requires more effort to make the proper mating surface.
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Old Apr 16, 2007, 09:24 AM
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Quote:
Originally Posted by Rodney
I agree with vintage1, I just use an aliphatic (usually Titebond II) with rubber bands around a form and never have any voids. On very large structures, instead of rubber bands, I use a mating surface to clamp the laminations in place until dry but that requires more effort to make the proper mating surface.
That is a good trick..for laser cut kits one cold include both male, and female, cut moulds.
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Old Apr 16, 2007, 09:52 AM
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This is the way I have always done mine. I don't like CA because it makes it difficult to sand.

Les
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Old Apr 16, 2007, 10:02 AM
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yes..that's exactly what I had in mind.

Do you soak, bend, clamp, dry, then clamp and bond, or all of a piece?
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Old Apr 16, 2007, 10:03 AM
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I think you are right about too much water in the wood, (but really soggy over night soaked wood sure bends easy), as it seems to dilute the glue even when it's applied full strength. Probably better to let the strips dry on the form without glue and then glue them together dry.

What I use to hold the strips against the form are strips of 1/4" masking tape for severe curves and regular 3/4" tape for gentler curves. When the laminated piece is untaped you will have rounded edges where the tape has crushed the wood where the tape was pulled down. There is an easy fix for this problem though. Just moisten the crushed edges with a wet finger and then go over them with a hot iron and they will pop right back to their former shape. This also works well for most other dents in balsa.

A tip for those who like to use really wet wood, an easy way to soak it is to get a piece of PVC pipe a little longer than the strips (I use a 4 foot piece of 1") and two end caps. glue on one of the end caps and leave the other loose. When you use it, fill the pipe partiallly with water, put in the balsa strips, hold them down and finish filling the pipe to the top and press on the loose cap which will hold the wood under water. Leave it standing vertically as the pressed on cap will probably leak if you lay it down. The next day you will have very floppy wet balsa for laminating. Just pull out the strips as you need them and pull them through a paper towel to remove the excess water.

Attached is a photo of a wing with the entire leading edge and trailing laminated in one piece (two layers of 1/16" on the leading edge increasing to 8 layers on the trailing edge). The span is 33inches and the curve at the tip has about a 1 1/4" diameter (The covering is transparent SoLite). This was done with 1/16X1/4 strips after a 24 hour soak. The reason for 1/16x1/4 strips is simple: A very large bundle of them 48"long, (thus the 48 " PVC pipe) were given to me some time ago by a former balsa cutter in Fresno, who's employee cut them out of about 5lb/cu. ft. balsa, and he couldn't sell them as strip because of their light weight so he asked me if I wanted them, talk about being in the right place at the right time!

Thanks for you ideas and help, John
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Old Apr 16, 2007, 12:01 PM
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I agree there is too much water in the wood. I use a cheap plastic wallpaper tub (about 4"x4"x30") to soak the strips in.

I fill the tub with about an inch of water and throw the strips in about 5-10 minutes before I start.

Pull a strip out and squeege it between finger and thumb. Then coat one side with Titebond (I use original) and run it between finger and thumb again to get rid of the excess glue and work it into the wood.

Next place it on the form. I usually make a foam core form, but I've also just stuck pins into the plan covered with waxed paper.

Keep adding strips until complete. With the foam core form, you can use rubber bands to hold the strips in place. If you use pins into the plans, you just add pins around the outside to keep everything in place.

The only voids I ever had were when I used the pins and didn't get the outside pins tight enough in a couple of spots.

- Roger
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Old Apr 17, 2007, 09:42 AM
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Vintage. It takes longer, but I clamp and dry, then glue and clamp again.

Les
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