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Building Tips and technical articles. => Building techniques => Topic started by: Bootlegger on January 01, 2020, 11:33:04 AM
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This is something that I have been wanting to do for sometime, but need some instructions on how to do it.
I am thinking about 1/16" thick by 1/2" wide for the tips, but I have never done this so I need all the help to build good ones.
Do I soak the balsa in water then form around the jig or what? Thanks for all the help, and Happy New New Year
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OK Gil..need more info, What plane has 1/2" wide tips ??? I must be missing something.
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OK Gil..need more info, What plane has 1/2" wide tips ??? I must be missing something.
He's laminating 4 pieces of 1/16" around a form to create a "bow" that is then used to form the outer perimeter of the tip, if I understand correctly.
You create a form with the inside edge of the perimeter, in this case, 1/4" smaller. You soak the wood in hot water for a while, apply carpenter's glue to the surfaces, then stack them and bend them around the form. Block them in place somehow, wait a day or two for everything to dry, then remove it. It will retain the shape (mostly), then you use that to form the outer part of the wing tip.
Brett
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It works great. Last summer I did a laminated leading edge for an elliptical wing. I used some plywood for the full-span mold. A bunch of laminations of 1/16" balsa. Soaked in hot water and pre-clamped and let dry. I used brads on either side of the mold to hook rubber bands to. Any damage to the edges of the outer layer was inconsequential as that part gets sanded off when shaping the LE. Then I went back and glued it up with highly thinned Titebond on the mold. I think I used waxed paper on the mold to prevent gluing the parts to it. Very little springback in the finished part. Strong.
I weighed the lams before and after gluing. Surprisingly, it added less than 10 gm, if I remember correctly. And some of that will get removed when I get to work shaping it.
Dave
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Gents:
The basic concept of what's being done here eludes me, as the old gray matter just won't allow an image match with the words so graciously shared. I hesitate to drill down on this any more, but am afraid I might be missing a good wingtip technique (I've grown to dread 'em).
I understand the laminating. Perimeter I kind of get in this context (or maybe not). Sorry Brett, but your word "bow" has three definitions in my noggin.
Again, much obliged.
Moe...
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Dave: "bow" in this context means "bend gently".
There's three ways I know how to do this:
- Hot water will soften the wood a bit, and allows for gentle bows
- Ammonia water will soften the wood a bit more (it softens the lignen) and lets you bend more aggressively -- but I was just reading that it's incompatible with white glue, so you need to let everything dry before gluing (which I do anyway, 'cuz I prefer to glue up laminations with Ambroid)
- Real heat, like a light bulb, soldering iron shank, hot monocoat iron, etc., will let you make amazing bends -- like 1/2" diameter with 1/16" balsa. But it takes the right touch, and the wood has to be moist. I think that the only reason the wood needs to be moist for is to conduct the heat into the interior -- but it has to be there. You want the wood to be steaming; sizzling is OK, and I often end up with wood that's a bit browned on the inner edges (which is OK -- cooked balsa actually smells kinda nice). If you want to go this route, scout out some YouTube videos for the pictures that tell the story.
For any of the above techniques, you know when you've gone too far because the wood buckles along the inner edge. Then you curse a bit, throw that part away, and start over. I always strip out and soak some extras when I'm doing this.
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if I remember correctly, Dave used a laminated wing tip as suggested on his Start Gazers.
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I take it none of you gents ever built a rubber powered model??? Virtually most wing tips are laminated and formed around a form. H^^
That's where I learned the "really hot" technique, for my own design Bostonian called "SquareCoupe" (it should be obvious what it's derived from).
(https://stunthanger.com/smf/scale-models/ercoupe-build-(slow)/?action=dlattach;attach=281778;image)
Here's an example done with heat, IIRC, on 1/8" thick wood, but it buckled slightly -- were I to do it again I'd use 3/32". It's from my Ercoupe build (https://stunthanger.com/smf/scale-models/ercoupe-build-(slow)/msg511469/#msg511469):
(https://stunthanger.com/smf/scale-models/ercoupe-build-(slow)/?action=dlattach;attach=283828;image)
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if I remember correctly, Dave used a laminated wing tip as suggested on his Start Gazers.
Well, yes, although there's not really any such thing as a "Star Gazer". It's a Trivial Pursuit, and I think this is shown on the plans.
Brett
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Tim: Your second picture said it all. Thanks!
Moe...
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Gents:
The basic concept of what's being done here eludes me, as the old gray matter just won't allow an image match with the words so graciously shared. I hesitate to drill down on this any more, but am afraid I might be missing a good wingtip technique (I've grown to dread 'em).
I understand the laminating. Perimeter I kind of get in this context (or maybe not). Sorry Brett, but your word "bow" has three definitions in my noggin.
Again, much obliged.
Moe...
Think Bend instead of bow. Bend strips of balsa around a a wingtip shaped curved form, with thin glue in between the strips. Look at a photo of a Piper Cub wing being recovered. The tips are just curved plywood made around a former.
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https://outerzone.co.uk/plan_details.asp?ID=2278
Lazy Bee RC model with bent laminated wingtips, and excellent instructions including tips like prebending on a pickle jar.
Hope this is a helpfulset of directions.
Phil