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Large balsa

Old 12-05-2005, 01:11 PM
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Lomcevak Duck
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Default Large balsa

Hey guys. I'm just about half way through rolling a massive project, and I need to find a good source for big wood. Like the balsa for the leading edge, each wing panel is going to be 5'3" long, plus an 18" center section. Yup. 12' span from scratch. I'm not really comfortable with joining multiple pieces together to get the neccessary length because I'm not too sure about the strength I would give up. I need some recomendations on where to find this stuff if you can help.
Much appretiated, Steve.
Old 12-05-2005, 02:09 PM
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Default RE: Large balsa

Lone star balsa offers 48" wood I have built two 12' planes and can say joining multiple pieces together adds to the strength . Like plywood multi grain and direction is a bonus. Just rember to offset your joints on the leading and trailing areas. Both of these planes are scrathed from 48" wood. Giant Telemaster and a "Enlarged" Precedent T240 Trainer[X(]
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Old 12-05-2005, 03:03 PM
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iaclmac
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Default RE: Large balsa

Joining lengths of balsa is not as hard as you might think. I have been doing it for years. I have followed a few basic guidelines. First, make all your joints on a 45 degree angle. This give you a larger surface for glue. Second is to make sure that your joints are centered over a rib. In this way when the joined material is also joined to the rib, it gives it further stability. Remember, the glue goint is strobger than the balsa wood. Third is to stager your joints. That is to say, if your first joint on a leading edge is over rib #8, do not place the joined trailing edge materila over the same rib. In this way the joints are further strengthen by not having them all in the same place.
Old 12-05-2005, 08:11 PM
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Default RE: Large balsa

OK. Thanks. I didn't think about joining at an angle. I was picturing a butt joint and a failing wing. Stickmaster, the plane I'm rolling is about the same dimensions as a Giant Telemaster. I didn't plan it that way, just sort of happened. The biggest difference is that the fuselage on mine is going to be mostly open stick construction. How much does yours weigh, and what are you powering it with?
Thanks again, Steve.
Old 12-05-2005, 08:13 PM
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Default RE: Large balsa

Wooden aircraft builders and boat builders have been joining lengths up for years by using something called a Scarff joint. Iaclmac has the right idea but the angle is not long enough (although epoxy will probably make it strong enough). To achieve the best joint strength the angle needs to be longer. For harder woods that can withstand more force the angle is 1:6 for softwoods and 1:8 for hardwoods. For balsa I would suggest 1:4. So to join two pieces of 1/2 inch stock end to end the overlap angle should be 2 inches long. That will provide enough longer side grain for a decent glue joint. If you try it I think you'll find that the wood around it fails before the joint does.
Old 12-05-2005, 08:28 PM
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Default RE: Large balsa

The Giant Telemaster Weighed in just over 35# with a 50cc Kioritz throwing a 20-6 It flew like A Telemaster or Cub for that matter. The other monster finshied at 47# with a 70cc Sachs No madien flight yet ..Now you see how small my build area is..[]
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Old 12-05-2005, 11:59 PM
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Default RE: Large balsa

Yeah. You think your buildig space is small? you should see mine. It's half of a walk in closet in an appartment. You can find pictures in a recent build thread I did in the extreme speed forum under the title "Dominator 200 build" about on the third or fourth page back now. I'll be building this beast on a 20' x 3' table in the basement of my parents' house. When the time comes I may do a build thread on it too.
Old 12-06-2005, 11:48 PM
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BWooster
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Default RE: Large balsa

Bruce is right (as always), except that it is called a scarf joint. There is also something called a keyed scarf joint, which is even stronger, where you cut a key at the end of each taper, to interlock with the other piece. Or, you can put a third piece as a separate key in the middle of the joint.

If you're interested I can diagram these things, and post them.

The piece will be at least as strong as the original. I do simple scarf joints all the time, especially when I'm running out of wood!

Or you can build a 'glulam' piece, and scarf the individual layers out of, say, 1/8": really strong. That would be overkill for a LE, but perfect for a spar top or bottom chord.
Old 12-07-2005, 12:00 AM
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BWooster
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Default RE: Large balsa

Diagram below
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Old 12-07-2005, 12:43 AM
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Default RE: Large balsa


ORIGINAL: snitch

Bruce is right (as always), except that it is called a scarf joint.......
...my finger stuttered.... I knew that but somehow an extra "f" got in there.
Old 12-07-2005, 10:06 AM
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Default RE: Large balsa

That's funny: my finger stuttered. HA! Thanks for the diagrams. I think I can figure this out now.
Old 01-20-2006, 08:40 AM
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a j o e l v a r d y
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Default RE: Large balsa

I know you can get large bits of balsa from THE BALSA CABIN

http://www.zyworld.com/balsacabin/home.htm
Old 01-20-2006, 09:14 AM
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Default RE: Large balsa

What about making the spars out of a lamination of two pieces that are half the thickness and are joined at different places?
-------------- l ----
------- l -----------

(consider this a question, not a suggestion)
Old 01-20-2006, 09:41 AM
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Default RE: Large balsa

So Sory I don't know

Old 01-20-2006, 10:31 AM
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Default RE: Large balsa

I just built a tower hobbies fun 51 and for every one of the wing spars the instructions called for scarf joints. Just make sure you put the joints at different sides of the wings. Also when i made the joints i lined them up against a ruler so that they came out pretty much perfectly straight.
GUS
Old 01-20-2006, 11:20 PM
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Default RE: Large balsa

been useing 60 degree angle splices for years, they are stronger than the balsa to begin with. just make sure that the pieces match, no gaps, no bad angles. if in doubt make the splice at least 6 x the stock size. dick

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