Thread: Discussion LJMP Meteor
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Old May 16, 2006, 12:59 PM
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Gladstone, MO
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Sailplaner: I have built quite a few Meteors and the only one I saw any wing flutter with was John Brown’s and as I remember his was the prototype and had only a single spar. The plans call for a main spar of 3/8x1/8” spruce and a second one of 1/4x1/8”. The plans say to use 3/8” vertical grained sheer web between the spruce on the main panel but the aft spar is only webbed with 1/16” on the rear. But I never built that way. I always used 1/2x1/8” or like this one 1/2x3/16” spruce (and I mean quarter sawn spruce, not basswood) and used a second spar at about 60% of 3/8x1/8” spruce. The spoilers were located behind the second spar not the main spar like the plans show. The first 24” of the spar is sheer webbed with 1/6’ plywood forward and 12” plywood aft. The entire spar is sheer webbed with 1/2” vertical grained balsa between the spruce and also on front and back with 1/16” balsa. This is also done on the tips stopping 3 bays from the tip. I also sheeted out 12’ from the root and to the rear spar both top and bottom and I think that really stiffens the wing. This one has .014 carbon top and bottom of the spar (and I really don’t think it was needed) and is wrapped with carbon tow for the entire length of the plywood. Back in the 80’s I had a couple of joiner boxes separate under stress and started using fishing line, something like 100 pound test but the tow is far better, stronger and easier to work with. The spar was constructed totally independent of the wing itself. The tips are built with about 1/8” of washout into the panel because I could never get it to warp in with the covering and hold.

I really believe in this D tube-box type of construction and if I am looking for strength I use it, heck, I use it just about in all my building, I just scale the parts down to fit what I am building. There is a little bit of weight penalty but most of it is at CG. My wings still wiggle in the lightest of lift. But the only flex is during launch and that is the wing rod and I’ve never seen or heard any flutter. The wing joiner is a 3/8" ejector pin and although it does flex it is nothing like the old rods we used in the 80’s.

I actually built one extra main panel (by mistake, don’t ask, don’t tell) and I destroyed it testing to see just how strong it was. I can only measure up to about 90 pounds and it took far more than that to break the panel and then it only cracked and buckled the top sheeting at, I am guessing about 150 pounds. I was not able to break the spar until I took it and put one end in vise and pulled on the end of the panel. It broke just where the forward plywood sheer web stopped. Figured it would break there if anywhere. But even then it did not shatter, but splintered and I think the plane would have been somewhat flyable. I should have made a video! It was neat.

One of the things I always liked about the Meteor was when you went fast the wings would flatten somewhat due to joiner rod flex and it really look cool flying across the sky, but alas, this one doesn’t do that!

Just for fun, here is the original John Brown Meteor – front center.

Okay, enough of this stuff, back to fixing my web server!
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