h-ray-RCA

Ok, I've searched and read all the posts about water vs ammonia, etc. This is my first kit (a DARE Design & EngineeringJn-4D Jenny www.darehobby.com) that I have to do so much laminating.

I have to laminate and bend some 1/16x1/8 balse to form the outline of the stab/elev, rudder/fin, and wingtips. The stab is about 12' wide and 8" chord, the fin/rudder is about 12" long by 6" high.


I'm going to use the water method of bending & laminating (or is that laminating and bending?), but my dumb question is do I hold the wood over the steam, boil it in the water, or soak it in the water then bend it? And do I laminate first then bend or the reverse.


Thanks for everyone's patience. I'll start a thread when I get going here in a couple days.

michpittsman

My Feedback: (11)

Full-size boat builders use a steam box. It's a simple wooden box just big enough to hold your strips, connected to a steam generator (tea kettle) with a tube. A few minutes should do it. Jim

MinnFlyer

My Feedback: (4)

For 1/16 x 1/8 strips, just wet them down with a wet rag and let set for a minute. They are so thin, they may even go around the curve dry.

majortom-RCU

My Feedback: (40)

For 1/16" thickness I normally wipe with a wet sponge, give the wood a few minutes to absorb the water, then wrap around your form or template or whatever you have. In cold weather the house air should dry the wood in maybe a half hour. Find something in the way of a circular disc with radius in the range of your tightest bends, and make yourself a balsa hoop just for practice. I presume you'll be using 4-6 strips of thickness for 1/8" thick parts. You can glue as you lay up, or lay up first then glue. I like to glue as I lay up, using aliphatic thinned with water 1:1, brushed on with a cheap student brush; that way the glue is more easily absorbed by the wet wood, and everything dries all together. If you keep the brush wet you can clean it under the tap and use it again.

For your first attempt you might just lay up with no glue, let the pieces dry and see how well they retain their shape when you take the pins out or otherwise let them go loose. You'll see they will spring out to a somewhat bigger radius than what they were formed to, but they will go back on the form with not much pressure.

You can try bending everything together, then dropping in thin CA. People complain how hard it is to sand CA, but I've found fresh 150 grit sandpaper and a firm block will cut the CA pretty quickly down to the wood grain.

dicknadine

Again its simple-- so they say-. here is my Hoop Plane Wing laminated with 1/16 strip's, using Windex and rubber bands, then good old yellow glue, over a cardbord template. it is strong and lite. dick

h-ray-RCA

Hey guys,

Thanks for the input, here's the result of my first try.

I scanned the plans and used them as a template to cut out the foam board for the template (I made dang sure the copies from my scanner/printer were the same size as the plan) Then I pinned the templates over the plan.

I used warm water and a sponge to soak the strips then bent them. I got some cracking on the first one so I soaked the rest longer but stil got the cracking.


Comments? Suggestions? I have to do another wingtip and the rudder/fin so I might try the ammonia/windex method next time.

majortom-RCU

My Feedback: (40)

Those are some pretty tight radiuses, so cracking is not a surprise. What I would try next is checking your balsa, selecting for light and soft grain; then soak the wood thoroughly rather than just getting it damp. Wet wood will expand across the grain, but almost no expansion along the length, so there should be no problem with shrinking outline as the wood dries. When I've had tight radiuses, I've sometimes run a rolling pin or a stout glass jar over the part of the piece that will have the tight radius. This compresses the grain, helps it bend. In extreme cases, I've used a razor saw to cut little kerfs, closely spaced in the area of the tight bends, kerfs on the inside. This facilitates compression on the inner part of the bend. If you're doing three or four strips in the lamination, and the kerfs are staggered randomly across the lamination, they are usually small enough to fill with glue and when everything dries you still have plenty of strength.

Strat2003

My Feedback: (1)

Keeping the strip under tension as you bend it....sort of pulling it around the form....will help prevent kinking on the tighter radii.

the-plumber

Water only makes the wood cells swell. Doesn't do a thing to make the wood any more pliable.

Ammonia on the other hand softens the cell walls, and that's where the strength is. When dried the wood is as strong as ever.

Don't use household cleaners with ammonia, it's a waste of time and money. Use ammonia, like Parson's Household Ammonia. No soap, no detergent, just ammonia (and enough water to make the ammonia somewhat less noxious). Most grocery chains carry the stuff; get mine at Kroger.

Open the windows, turn on a fan, and hold yer nose - stuff stinks but it works like majik.

h-ray-RCA

Score one for windex.

In case no one's thought of this, after trying the bowl of water and a sponge (and having the wood crack) I stopped by Home Depot today after flying. 2 lengths of 1" PVC pipe, one 25" and the other 37" (for 24" and 36" length wood.) . Fill full of Windex, insert wood, cap and let sit.


They still cracked at one place but I put that to it being the last peice of wood and it dried out wating for me to get to it. Learned something.


These are the dried ones I did last night, and the new ones I just did. Now waiting for the glue to dry.

Question: On the wingtip I did last night it straightnend out a litttle bit, enough that I'm going to have to bend it back into position when I build the wing. Since it's such a small, lightweight wing would this cause too much stress and should I just make another one? Or do you think it would be ok? Likewise how much effect do you think the gaps on the original stab would have had?


Thanks for the help everyone, wish I could buy you all a round.

majortom-RCU

My Feedback: (40)

A little springback is to be expected. When you glue it up, it should bend to the desired outline without a lot of stress. Glue it up and don't worry about it. As to the gaps in your first pieces, the worst thing about them is they are not a great testament to your craftsmanship--which is more a matter of your own satisfaction than a practical problem. Once the piece is covered, there's hardly any stress to worry about. Nice to see your problem solved so well.

Xrod

My Feedback: (2)

Steam bending is the solution to your problem. I use this method to bend sides for guitars out of hardwood. First let the stips soak in water for a while. Depends on the thickness of the wood, and hot water will help. The wood should be saturated. While you are waiting for the wood to soak, heat up your covering iron. I use a small trim iron with the rounded tip, but any will do. Clamp the iron to your bench so that you can use two hands to handle the wood. Work on about an inch at a time. Hold the wood against the heat while bending, the wood will steam and "relax", hold the bend while it cools, then check against your plan. This will only be needed for your sharp radius bends. The rest can be held against your plan with pins and will be set when the wood/glue dries. If you still have problems with cracking, then thinner laminations will be neccessary.

Gollywock

h-ray- If you are having problems with the 1/16, you might buy a sheet of straight grain 1/32 and strip it 1/8 wide. Twice as many strips, but a good bit easier to form. jim

kdheath

To help your trouble with the tight radii, try gently running the wet strips back-and-forth over a smooth, round bar. Maybe a large piece of tubing or rod. I've used the handle on the bench vise. The idea is to work a little bend into the wet wood before wrapping them onto your forms.

I wish I had a digi-cam handy to show you some I made out of 1/64th thick model RR bass wood. They're for a peanut size rubber scale model (13" wingspan) and turned out great.

dicknadine

here is my method. soak the strips, usually 1/32 x1/4 in water, can add some ammonia, and wrap around the foam plug. hold in place with whatever works, till dry. take off straps and check for form, if ok start to bond them together and then start the 2nd layer at a 45 degree's. i usually use contact cement, the 3rd layer at 90 degrees, etc- etc. THEN hog out the foam plug. its strong and works. dick will post photos when I find them

Gollywock

You can wax a cardboard form with a candle. Pin the form down, and start forming the wet strips around the form. Using alphatic resin (carpenter's glue), glue the strips as you go. You will need to use pins or whatever to hold the strips tight against the form until dry (I use balsa sticks about an inch long pinned to the building board). After it's dry, you can remove it from the form and it will maintain it's shape. The wax prevents it from sticking to the cardboard form. Jim