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Building Tips and technical articles. => 1/2 A building. => Topic started by: minnesotamodeler on January 19, 2008, 06:49:37 PM
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Here's a concept I've been messing with for awhile--a suspended bellcrank supported by the fuselage, not the wing. Nothing new I know, except in 1/2A application.
Bellcrank is trapped on a wood dowel by 2 pieces of thin ply glued to the dowel, which is then installed through (and glued to) 1/8" balsa supports top and bottom. The dowel extends out of the wing about 3/16" both ways; the fuselage is slid (slidden?) on from the inboard side; dowel ends rest in notches in the fuse--all load is transferred to the fuselage. This particular model will have 1/32" balsa skin applied that will cover the dowel and notches.
Slick?
--Ray
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Ray, gotta love you for sharing with us the efforts and ideas that you have to share.
I truly like the clear and crisp photos that help lend more info than words can convey.
To this I must also applaude your enthusiasm for these things and ultimately the hobby itself! Heck! You can't wait 'till the glue is completely hardened!
This looks pretty easy to do, thank you again for sharing,
Robert
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That looks pretty interesting. Do the leadouts go all the way thru the BC. BC is wood? Not bushed? Just wondering and trying to guess how strong it will turn out to be. Knowing your experience its probably great.
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That looks pretty interesting. Do the leadouts go all the way thru the BC. BC is wood? Not bushed? Just wondering and trying to guess how strong it will turn out to be. Knowing your experience its probably great.
Yup, LOs continuous, I've been doing that for a few years now. Also wooden BCs, but gotta be hard, 5 ply 1/8" thick stuff. No bushing, no need, these are 1/2As after all...we're talking maybe 5 lbs. pull on a fast, heavy one? Probably not that much.
Wood BC means I can put a 3" in with no weight penalty.
Robert, thanks for the good words. Designing and finding new ways of doing things is my favorite part of the hobby.
--Ray
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The "double-shear" mounting of the bellcrank is good practice, for all applications, including 1/2A.
I hate to say it, but the "laced leadouts" you show have been banned from all events. It was popular for a short time in speed and racing, but disaster ensued.
This form of leadout makes the cable flex in a very small radius every time the controls are moved. The heavier the line pull, the worse it gets.
It probably won't bite you on that little plane, but don't do it again.
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I've had a wooden bellcrank in a 1/2A eat through the leadout. I bush mine these days.
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Looks like a good application for that pile of old 3" Veco's we all must have hanging around <=
W.
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The "double-shear" mounting of the bellcrank is good practice, for all applications, including 1/2A.
I hate to say it, but the "laced leadouts" you show have been banned from all events. It was popular for a short time in speed and racing, but disaster ensued.
This form of leadout makes the cable flex in a very small radius every time the controls are moved. The heavier the line pull, the worse it gets.
It probably won't bite you on that little plane, but don't do it again.
Wow...didn't know I'd run up against the leadout police: "I'll let it go this time, but don't do it again!"
No offense taken, nor intended to give...just struck me as funny.
My planes are not designed or intended for competition; they are most all sport planes. So whether or not they are "banned" isn't my concern, sorry to be so cavalier about it but that's the way it is. Dunno how you'd check for it anyhow, in a closed-wing model. I'm a pragmatist when it comes to models--try it; if it works keep it. As mentioned, I've done leadouts this way (on wood BCs and nylon too) for years now. Some control systems have survived several airplanes. Never broke one, nor saw one frayed, yet. Till I do I'll just keep on using it, thank you, since it makes such a clean connection at the BC, no loose ends to snag anything at all.
Thanks for the comments, guys, pro and con both.
--Ray
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I like look of your b/c mount. Just wondering how thick the wing is and how long your chord is? I always have trouble trying to fit the controls in a skinny wing so my designs tend to grow fat.
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Jim, the rib height is 1 1/16", but the BC pivot is behind the high point so the thickness there is about 15/16". The root chord is 7 1/4". It does get tricky trying to do this is a skinnier wing. On my smaller (thinner) planes I generally use a 1/8" ply. floor spanning the center ribs, glued flush against the underside planking, and just bolt the BC through that.
--Ray
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Ray
you might want to look at the leadout wire that is rubbing on the washer on the underside of the bellcrank post, it looks like it might rub everytime the bellcrank moves.
that could end up causing a drag problem or even sawing thru the washer or post.
it could be it just looks that way in the picture.
dave jr.
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I see what you're seeing, Dave...no tension on that portion of the leadout; also that's a piece of 1/32" ply. it's riding on, not a metal washer. No drag or wear problems. Thanks for the heads up anyhow.
--Ray