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Old Oct 13, 2012, 09:30 PM
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kimchiyuk's Avatar
United States, NY, Eldred
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wetting balsa to shape

I'm building my first kit. A Tower Hobbies fun 51. One of the balsa sheeting strips for the leading edge is very firm. I have lightly wet other blasa with windex with great results. This sheet though doesn't want to budge with a light spray. How much can I saturate it without ruining the wood or its future integrity or any other ideas? I don't have a place to get balsa within a reasonable distance or I'd just get a new piece.
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Old Oct 13, 2012, 09:40 PM
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Put that stubborn piece in the bath tub under water overnight.weight it down,and let it think about it's bad behaviour...The harder it is,the longer it takes to soak it up..It won't hurt the balsa to lie there for a long time.

When you do try to bend it, do it gradually, slowly,as the wood fibers stretch into the new shape. Weight it down and let it dry.

If you presoak with windex,be sure it contains ammonia-some of the new blends don't,and Ammonia is what you need.
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Old Oct 13, 2012, 10:00 PM
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+1 on the Ammonia. I mix it 80:20 with some water in a spray bottle for bending Balsa.
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Old Oct 13, 2012, 10:22 PM
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Thanks for the info...and yes the windex I'm using contains ammonia. Just out of curiosity, what is it about the ammonia that makes it the go to for balsa shaping?
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Old Oct 13, 2012, 10:31 PM
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Can't say-apparently it breaks up the wood's "surface tension", allowing water to penetrate into the fibers.
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Old Oct 13, 2012, 10:52 PM
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Quote:
Originally Posted by kimchiyuk View Post
Just out of curiosity, what is it about the ammonia that makes it the go to for balsa shaping?
The ammonia breaks down the hydrogen bonds within cell walls and within the lignin matrix. This allows molecular movement when subjected to tensile or compressive forces. Once the ammonia evaporates from the wood, new bonds are made creating a permanent set.

The process is reversible by further ammonia treatment. Chemical set is not recoverable by treating with hot water or steam; unlike with steam and hot water bending treatments, no stresses or strains are bent into the wood. Thus, the new shape is like other kiln or air dried wood. It is ready to be machined, glued and finished.
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Old Oct 13, 2012, 10:56 PM
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So after soaking it in the tub overnight, I still spray it with ammomia when setting to the desired shape?
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Old Oct 13, 2012, 10:59 PM
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Put some ammonia in the tub with the water.
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Old Oct 13, 2012, 11:08 PM
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Soak it down and keep it that way until it's like overdone pasta...

When it dries the lignum that forms the cell walls of the wood will harden up just fine once the water and ammonia evaporates.

Instead of Windex, which isn't a "real" ammonia, use straight cleaning ammonia. To avoid the fumes I'd put the wood into a plastic garbage bag and then, while holding your breath, reach in and pour about two cups of the stuff over the wood then immediately fold the bag closed with as little air in it as practical and let it sit for about 5 to 10 minutes. If what I've read is right it'll come out like that overdone pasta I was talking about and lay in place just fine. And once it dries completely you'll be good.
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Old Oct 14, 2012, 01:24 AM
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Floorboards?

All the above is sound advice, but if a piece of balsa in a kit needs that much attention to make it behave, it is probably heavy as well.
My tendency is to replace the offending piece from decent stock in my pile, and save the kit balsa for floorboards.
Cheers,
PeteM
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Old Oct 14, 2012, 05:01 AM
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Quote:
Originally Posted by Petem View Post
All the above is sound advice, but if a piece of balsa in a kit needs that much attention to make it behave, it is probably heavy as well.
My tendency is to replace the offending piece from decent stock in my pile, and save the kit balsa for floorboards.
Cheers,
PeteM
Most of us would,also,but the OP suggested an inconvenience to obtain new wood...learning to bend the piece he has would be beneficial.
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Old Oct 14, 2012, 05:08 AM
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-Funny this would come up,at the moment I'm researching "Balsa Wood" for a new forum soon to be added.
'Balsa and lite ply,scratch and kit builds' should be running soon.

Our intent is to further the traditional balsa building techniques which have brought us so much satisfaction.

I had thought an in-depth discussion would be helpful to neophytes and elders as well.
Once it's running,maybe you gents would join and share your knowledge and experience. If we're going to build with balsa,we should at least know what it is, and how it can benefit us the most.
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Old Oct 14, 2012, 08:18 AM
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To preserve domestic harmony, Don't use the tub, make a Balsa bath from a piece of plastic waste pipe. Solvent seal one end and use a plug in cap for the other. Check your plumbers supplies for waste pipe systems.

You can keep it filled ready for use and despite what others may say, Ammonia is preferable, it makes the balsa feel like rubber.

Regards Ian.
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Old Oct 14, 2012, 08:51 AM
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Here is a link to an old post showing what can be done with ammonia and water!

http://www.rcgroups.com/forums/showp...51&postcount=3

Martin.
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Old Oct 14, 2012, 10:30 AM
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Another suggestion for a soaking container is the trough used to soak pre-pasted wall paper. Most are 4 ft long with access to bend the balsa after it gets initially wet so you don't have to fill the trough too much in order to totally submerge the balsa piece.

Alan
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