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Building Tips and technical articles. => Building techniques => Topic started by: Leester on February 24, 2008, 12:55:22 PM
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I have a small 45" wing I would like to build using the Brodak leveling bar system. The wing is tapered so when laying out the bottom spar am I just concerned with shimming the tip so that the center line of the tip rib is the same hieght from the board as the root ribs center line ?? This system seems to be less hassle to set up than a rod or other type wing jig. I do realize the spar needs to be straight its entire length. TIA
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Lee, the levelling bar method works fine, and is easy enough to set up if you remember a few critical considerrations.
Carefully measure the width of the root rib, at the spar cutout, and the tip rib, again at the spar cutout. we want the width of the rib to its' outer edge, not to the bottom of the spar cutout.
Figure 1/2 the difference between the two measurements, and that's the hieght of your shim at the tip. This will take care of the wing taper difference between the root and the tip.
Use two straight 1/2" square pieces of hard balsa as your levelling bars. These need to be reasonably straight in all directions.
Find the spot, towards the trailing edge, where this 1/2" sq. bar holds the rib absolutly level with the work surface. Place a mark on the rib where the bar touches the rib when it's level and supported by the bar.
Likewise, find the spot on the tip rib where the same thing is happening.
Align your bar to these two marks and you have set up your levelling bar.
This only works accuratley with a single, constant taper. It won't work withan elyptical taper.
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Thanks John, that answers everything and my building surface IS straight and level.
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You're going to want to support that bottom spar to hold it straight and true. I build on glass and glue little blocks of balsa between ribs then pin the spar to the little blocks.
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You're going to want to support that bottom spar to hold it straight and true. I build on glass and glue little blocks of balsa between ribs then pin the spar to the little blocks.
Hmmmmmm......... we got a lot of building habits in common, there, Frank! A glass surface is the greatest thing I ever did for building. A friend of mine gave me a run down billiards table years ago. It wasn't fit for playing on without a LOT of work. But, the bed is still perfect, and a piece of roughly 4X6 foot 3/8ths" glass is the perfect surface when shimmed flat, easy enough to do in my case!
I wouldn't trade it for the world, especially since it holds a LOT of memories of when Aaron lived here and he was building his first planes!
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BTW: Lee, I like using the leveling bar system when building from laser cut ribs and such!
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Glass is the cat's meow......I put the plans under the glass and glue those balsa blocks in place. Workd real good for making a disposable fixture for each model.
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Frank and Bill I totally agree with the glass top, I didn't realize how much of an improvement it made until I got one. My small building area is a desk the original owner built in a closet inset. My house is all steel frame construction on a concrete slab and every wall is straight and true. He built it using the walls as bracing and used a 1" thick top covered in counter top material. The top is perfectly level in all dimensions, so I put dry wall on top and 1/4" glass on top of that. The only draw back is I can only get up to a 48" wing built on it, but at least there straight and the leveling bar or block system works fine in this area. Thanks for all the tips everyone.
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Hi Lee,
It isn't too hard to build wings in halves. That would allow you over 96" wings! LOL!!
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Thats what I use to do when I built RC gliders. n~ Up to 118" wing span.