autoreply
Well-Known Member
I guess the subject is pretty clear; how to connect load-bearing composite parts. I'm assuming molds, pulled off a plug, given my own design ideas.
Much of the knowledge I got from the HP-24 project (Bob Kuykendall). He is also the author of most of the pictures.
My fuselage is has a highly-tapered tail (roughly 10" inner diameter) and a conventional (albeit downwards) fin/rudder with probably a monocoque structure, save some local reinforcements. The leading edge joint of the wing is pretty highly loaded, not only in shear, but also in tension (wing skin pressures and mostly, fuel pressure during a spin/sloshing), wing skins are traditional glider-like, sandwich construction, no foam at the leading edge, spar and drag spar.
"Repair"
Keep both parts in the mold, sand away at the joint and apply several layers of wet lay-up, identical to how you would repair. Seems the best, easiest, lightest, straight-forward way. Can't be used in areas where access is limited, like the tail, fin, elevator and wing.
Lots of glue/flox/adhesive
Here's a nice description (picture from
You're looking at the mold (pink), with a blue wingskin, a light-blue foam and some glue/mumpe (epoxy/cotton I presume). The foam constrains the mumpe and the joint is glue-only. I have difficulties, believing the glue joint is reliable enough.
Built-in joggle
One of the more common methods. Here's a great description.
I have several (unfounded?) problems with this method. First of all, the problem Bob mentions; the glue forcing away the joggles part. He applies manual force. Would it be possible to "vacuum-bag" the joint and apply a vacuum? To me that looks like a good way to apply a large force to the joint, without complex structures or other parts. Does reality support my theories?
Another thing I'm having trouble with is visualizing the wing skins done this way. Wet layup of the joggle seems difficult, given that it's "hanging" in the mold, though vacuum bagging could help. Does this work in reality?
Separate joggle
Described here
Basically, you're building a separate joggle on your plug on double molds and bend it a bit to fit the (slightly smaller) interior dimensions. Positioning could be a problem as could/would clamping be. Same question, does vacuum-bagging work?
Wet joggle
Apply enough layers of fabric on the joint and position them correctly. Can be done either via wet layup and vacuum bagging, or via vacuum infusion.
Positioning and sealing should be troublesome (in wings/tail surfaces), but I've done spar inspections on 30 ft long wings with a remote camera and with a boom you can do quite a lot in very tight areas. Especially with vacuum infusion this doesn't sound impossible to me. Ideas?
Other ideas, how you can join composite parts? I recall Orion, mentioning a foam joint?
Much of the knowledge I got from the HP-24 project (Bob Kuykendall). He is also the author of most of the pictures.
My fuselage is has a highly-tapered tail (roughly 10" inner diameter) and a conventional (albeit downwards) fin/rudder with probably a monocoque structure, save some local reinforcements. The leading edge joint of the wing is pretty highly loaded, not only in shear, but also in tension (wing skin pressures and mostly, fuel pressure during a spin/sloshing), wing skins are traditional glider-like, sandwich construction, no foam at the leading edge, spar and drag spar.
"Repair"
Keep both parts in the mold, sand away at the joint and apply several layers of wet lay-up, identical to how you would repair. Seems the best, easiest, lightest, straight-forward way. Can't be used in areas where access is limited, like the tail, fin, elevator and wing.
Lots of glue/flox/adhesive
Here's a nice description (picture from
You're looking at the mold (pink), with a blue wingskin, a light-blue foam and some glue/mumpe (epoxy/cotton I presume). The foam constrains the mumpe and the joint is glue-only. I have difficulties, believing the glue joint is reliable enough.
Built-in joggle
One of the more common methods. Here's a great description.
I have several (unfounded?) problems with this method. First of all, the problem Bob mentions; the glue forcing away the joggles part. He applies manual force. Would it be possible to "vacuum-bag" the joint and apply a vacuum? To me that looks like a good way to apply a large force to the joint, without complex structures or other parts. Does reality support my theories?
Another thing I'm having trouble with is visualizing the wing skins done this way. Wet layup of the joggle seems difficult, given that it's "hanging" in the mold, though vacuum bagging could help. Does this work in reality?
Separate joggle
Described here
Basically, you're building a separate joggle on your plug on double molds and bend it a bit to fit the (slightly smaller) interior dimensions. Positioning could be a problem as could/would clamping be. Same question, does vacuum-bagging work?
Wet joggle
Apply enough layers of fabric on the joint and position them correctly. Can be done either via wet layup and vacuum bagging, or via vacuum infusion.
Positioning and sealing should be troublesome (in wings/tail surfaces), but I've done spar inspections on 30 ft long wings with a remote camera and with a boom you can do quite a lot in very tight areas. Especially with vacuum infusion this doesn't sound impossible to me. Ideas?
Other ideas, how you can join composite parts? I recall Orion, mentioning a foam joint?
