built-up wing disaster--help!
03-04-2002, 09:44 PM
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built-up wing disaster--help!
I am building a 117" dynaflite Sensor that I started about 13 years ago (I took a hiatus from the hobby).
Here is the problem (and perhaps the reason I quit building it way back then, but I don't remember): I over-sanded the leading edge spar and when I put on the leading edge top-sheeting it cracked along the front edge (both left and right inner wing panels--at least I was consistent).
Options:
1) tear the wing apart and redo the screw-up: I think this isn't worth the trouble--better to toss in trash.
2) Sand the wing and fly the plane as-is. I suspect the plane would fly ok, but it's probably a little weak so if I ding the leading edge I'll get a serious crunch.
3) I could shape the leading edge then use some thin fiberglass to strengthen (adding some weight to the plane).
Which of these makes the most sense (or is there some other option I should consider)?
Thanks,
Wayne
Here is the problem (and perhaps the reason I quit building it way back then, but I don't remember): I over-sanded the leading edge spar and when I put on the leading edge top-sheeting it cracked along the front edge (both left and right inner wing panels--at least I was consistent).
Options:
1) tear the wing apart and redo the screw-up: I think this isn't worth the trouble--better to toss in trash.
2) Sand the wing and fly the plane as-is. I suspect the plane would fly ok, but it's probably a little weak so if I ding the leading edge I'll get a serious crunch.
3) I could shape the leading edge then use some thin fiberglass to strengthen (adding some weight to the plane).
Which of these makes the most sense (or is there some other option I should consider)?
Thanks,
Wayne
03-04-2002, 10:26 PM
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LE fix
You could do the following:
With a brand new #11 blade, cut the LE off, including the amount of LE sheeting that overlaps it. Glue on a new LE. Your new LE should be the same dimensions as your old LE PLUS the little bit of sheeting overlap that was glued on top. It doesn't really matter for a floater, if the LE butts up against the backside of your LE (as it would if you did this repair) or if it overlaps the top of your LE (as it did originally, if I understood your description correctly). If worried about the sheeting sagging at the LE between ribs, you could also add a sub-LE as shown in the sketch: Glue a strip of 1/16" balsa along the back surface of the LE to form a sort of shelf for the LE to rest on. After glueing, saw slots in the 1/16 strip to accomodat the front of your ribs.
Hope this helps
-Elliot
With a brand new #11 blade, cut the LE off, including the amount of LE sheeting that overlaps it. Glue on a new LE. Your new LE should be the same dimensions as your old LE PLUS the little bit of sheeting overlap that was glued on top. It doesn't really matter for a floater, if the LE butts up against the backside of your LE (as it would if you did this repair) or if it overlaps the top of your LE (as it did originally, if I understood your description correctly). If worried about the sheeting sagging at the LE between ribs, you could also add a sub-LE as shown in the sketch: Glue a strip of 1/16" balsa along the back surface of the LE to form a sort of shelf for the LE to rest on. After glueing, saw slots in the 1/16 strip to accomodat the front of your ribs.
Hope this helps
-Elliot
03-05-2002, 04:39 AM
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built-up wing disaster--help!
Elliot,
Yep, that's better than any of my ideas. Thanks. I'm hoping the quick and detailed response means I'm not the first to put his foot in this particular cow-pie.
Dan Thornburg wrote that the leading ten percent of the airfoil is more important than the remaining 90 percent. If that's true then you saved the lion's share of my airfoil.
Regards,
Wayne
Yep, that's better than any of my ideas. Thanks. I'm hoping the quick and detailed response means I'm not the first to put his foot in this particular cow-pie.
Dan Thornburg wrote that the leading ten percent of the airfoil is more important than the remaining 90 percent. If that's true then you saved the lion's share of my airfoil.
Regards,
Wayne
03-05-2002, 05:26 AM
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built-up wing disaster--help!
no prob Wayne,
Naw, you're probably not the first to step into that one. Plenty of ways to damage our models before they're off the drawing board! This technique and variations thereof, will come in handy should you your plane happen to strike the occasional hard branch or bush in the landing zone.
Yes, front of airfoil is generally most critical (not to discount what comes after) but at the same time, most of us are incapable of achieving the precision required to produce a wing with the performance characteristics defined by the intended airfoil. Deviations on the order of a thousandth of an inch can be significant. But still, it is nice to try to avoid any gross deviations.
Cheers,
-Elliot
Naw, you're probably not the first to step into that one. Plenty of ways to damage our models before they're off the drawing board! This technique and variations thereof, will come in handy should you your plane happen to strike the occasional hard branch or bush in the landing zone.
Yes, front of airfoil is generally most critical (not to discount what comes after) but at the same time, most of us are incapable of achieving the precision required to produce a wing with the performance characteristics defined by the intended airfoil. Deviations on the order of a thousandth of an inch can be significant. But still, it is nice to try to avoid any gross deviations.
Cheers,
-Elliot
