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Joined: 10/27/2002 From: Woodstock, GA, USA Status: offline
Wing cores
I do something a little different than most here. I like to honeycomb the outer 1/3 of my wing panels. It reduces mass at the tips, and makes snapping and spinning manuevers more controllable. That's the theory anyway, it seems to work in practical application.
Otherwise, just sheet as normal. Note that you can't use a vacuum on a honeycombed wing panel, it will either distort or crush.
I start out by cutting a piece of poster board the shape of the wing panel. Cut it just a little bigger chord-wise, and then place it between the shuck and the core. Align the TEs and mark the LE line in this condition. Trim the poster board until it's a perfect match when layed on top of the core.
Now make a second piece just like it. Tape the TEs together length-wise, so they lay on top of each other, "hinged" at the TE.
Lay out a diagonal pattern as shown in the pic, leaving the strips of foam about 3/8" wide. Don't make them too far apart as this will weaken the wing and distort the sheeting. 3-4 inches is about right. Make sure you don't get close to the hinge line or the spar locations. Go ahead and make a cut out for your servo box as well.
When satisfied with your pattern, place it around the wing core and tape it securely.
Either using a long, sharp blade, or better yet a hot knife, cut away the voids. A hot knife works really well for this; you can get them at CST or any foam supplier for less than $20.
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Either making an extra slot on the honeycomb template, or by marking it and using a band saw, make the cut for the false rib. It should run from just behind the wing tube all the way out of the LE.
Place the core on one half of the shuck. Mark the line following the wing spars. These are 1/8" wide, 2 per side.
The best way I know to do this is by using a router attachment on a dremel set at the depth of the spar. Using the edge of a level, run the router down the core cutting a perfectly straight 1/8" slot.
Flip over and repeat on the other side.
Now cut an oversized square of 1/8" lite ply, about 2" wide. Lay it into the false rib slot, and insert the wing tube. Bump it up against the piece of wood and press and turn. This should make a barely visible mark when you remove the piece.
Now using a 7/8" hole saw, cut the hole in the false rib for the wing tube. Slide your wing tube socket through this hole and be sure it passes through without too much friction.
Place the rib back in place, and insert the socket into the wing, through teh hole to locate the false rib. Trace the outline with a sharpie. Remove the piece and trim just larger than the outline.
Using polyurethane glue, apply a thin layer to the false rib on each side. If it fits tightly in it's slot, you're good to go. if it's a little loose, spray a fine mist of water on the glue before installing the piece. This will cause it to foam and fill the cracks.
Put the false rib in position, and insert the tube again to make sure you don't have alignment problems later. if you wish, you can glue the socket in at this point with a thin application of laminating resin. I usually wait until after the cores are sheeted and capped (just to make sure I don't waste a socket if it comes out defective). So far, I'm batting 1000 on that one
After the glue dries, use a long sanding block and CAREFULLY sand the false rib flush with the core. Go slow and take your time here.
< Message edited by MHester -- 12/15/2005 2:16:45 AM >
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I have a 1/8" thick file that I use to match the slot on the false rib to the slot I cut in the core.
Cut 4 pieces of 1/8x1/4 spruce strips to a length of 14". These are the main spars.
For the outer spars, I laminate a piece of 1/16" balsa with .007" C/F strip. Add another piece of 1/16" balsa to the carbon for light laminated spar. Use either laminating resin and a lot of weight or CA, either works fine.
When dry cut into 16" long 1/4" strips, you'll need 4 of them.
Using polyurethane glue, install the spars and let dry. If you used the router method they should fit very tightly and neatly. Adjust anything that doesn't fit with a file or sandpaper....or blade if it's bad enough. The only place the bond is critical is where the spruce spars intersect the false rib. Don't stress over the rest.
I usually place these in the shucks, with wax paper between the shucks and cores, and add a little weight (on a flat table of course) just to make sure I dont accidentally induce a little preload on the core.
After dry, carefully sand these flush with the core.
Go over the entire core with a long sanding block and 220-400 grit paper, and use compressed air to blow off the dust. Alternatively you can use a vacuum, but the air works better.
Posts: 2415
Joined: 10/27/2002 From: Woodstock, GA, USA Status: offline
Honeycombing the outer 1/3 gains about 1 ounce per wing panel, 2 ounces off the total plane. About 56 grams or so. It's not quite as effective on the tail surfaces.
But the real advantage is not so much in the weight savings as moving the CG of the wing panel itself more toward the centerline of the plane. Less mass in the tips, better the snap and spin.
-Mike
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Mike, I have to ask... or point out rather.. is that your thumb in the pic with the red nail polish?????
on a serious note, why do you not honeycomb the inboard side of the wing? i wunderstand the whole inertia and rotaion of mass thing but even doing the inside of the wings may gain you another ounce perwing.. 4 oz total?
Just curious.. more so of the wing and not the nails VBG
Posts: 2415
Joined: 10/27/2002 From: Woodstock, GA, USA Status: offline
LMAO!!!
No I had my wife hold the core for me. She's a rare one, she actually makes some of the composites, does my Monokote, tell me my square on corner from top with half rolls looks like s* and I should be ashamed.....
She doesn't have any polish lately, she's been making frikken sweet carbon canopies and the acetone from the clean-up keeps messing it up
-Mike
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Owner Custom Airframes of America, Team YS, Mercury Adhesives
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Looks good Mike. One of these days you're gonna have to let me fly it.
On the retracts, you can instantly take about 2ozs of unnecessary weight off them by cutting the steel struts about 1/2" down from the coils and epoxying carbon tubes in place. Less work on the servo also.
On the other hand, retracts on an electric are a cinch with this method.
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RE: Black Magic v2 builder's thread! - 
