To any new guys starting out, and to all ARF fanciers likely to purchase a ready built: After 25 years in this hobby, you tend to learn a few things, and the first one I was taught in building technique, is to always, and I repeat always, fiberglass the center section of any wing panel you join. NO EXCEPTIONS AND I DONT CARE WHAT ELSE YOU ARE THINKING OF!!!! No joiner no matter what the material is made out of, will prevent wing fold over during a high "G" maneuver, without a good and proper fiberglass job![X(] If you already own an ARF, and you assembled the wing halves just with epoxy, fiberglass your center section NOW!!!. Put on some Nitrile or latex gloves and apply plenty of 30 minute epoxy for joining the root rib ends and associated joiners, (wipe off any excess with denatured alcohol) check and re-check then fixture the dihedral with end spacer shims and weights, let set. Failure to "set in place" the dihedral during curing can ruin your wing! Remove at least a 3 inch wide strip of original covering in the case of an ARF, top and bottom of the center section, (use a brand new #11 blade and press very very lightly not to cut into the sheeting!!!!!) Now we do the bottom first: Apply a low tack painters type masking tape just at the very end of the recently removed covering, staying on the covering, not the wood, its ok if a little epoxy wicks the end of the covering by maybe 1/16 of an inch. Remember all this fiberglass work will soon be covered again with Iron on! We now are controlling where the extra epoxy will be going! Sparingly brush some well mixed 10-15% thinned out 30 minute epoxy over the newly exposed center section, (use denatured alcohol and an acid brush. Dont over thin the glue! Mix the epoxy first very well before thinning), apply the fiberglass strip (cut it an extra 4 to 6 inches long) onto the thinly applied epoxy and position it centered and parallel to the joined center seam. (Don’t ever try this with medium "CA" as some instructions say to do, its way too brittle after it cures, and the fumes will lock your heart right up!!![:'(] ) Tape the ends of the fiberglass CLOTH STRIP, to the opposite sides of the wing, (the top of the wing where you are not fiberglassing) with regular masking tape, wrapping over towards the top, and pulling it as tightly as possible. (Use a three-inch wide strip of glass on planes weighing over 12 lbs.) Continue to now wet and cover the top of the glass sparingly with the thinned out epoxy, until the white changes to translucent. Push the glue into the weave with the brush, or try your gloved finger tips, as just a little epoxy goes a long way here. Keep the gloves cleaned off with alcohol, so you won’t mess up the rest of your covering. Allow adhesion and purchase, to extend a 1/2-inch onto the end area, past the center line of the leading and trailing edge, onto the opposite side of the wing. When we do the other side, this gives us eventually a one inch over lap, and its strong as steel. You may decide to follow up with another layer while still wet, but cut it an inch wider on both sides. I personally think it's over kill at that point, and adds unwanted weight. Only a big quarter scale or third scale project demands the second layer. Get your fiberglass wing joiner cloth at an automotive body repair supply house, it's usually a heavy grade like 5 to 6 ounce cloth, and a single strip is plenty. If you purchase cloth from your LHS, specify 5 or 6 ounce cloth. Dont bother with finer weaves, they're way too weak. Now here's the big secret to a glass smooth perfect fiberglassed joint: Cover the wet glass with a 6 to 8 inch wide strip of plan protector or even better, some old discarded mono-cote plastic backing. (You can consider taking off the gloves at this point too) Spread and work the glue in and across the joint area, but don't push too hard allowing it to migrate past our low tack masking tape borders. Two separate paper towels to smooth it with in both hands, makes it nicer. Continue to smooth it down for a while, and In about 20 to 25 minutes, try lifting one end in a quick jerk. If its still tacky at this point, rub the plastic back down, and wait 5 more minutes. (It makes a distinctive ripping sound when its ready to remove) When you can shear a corner of the plastic sheet off the epoxy without any stringy adhesion, continue to remove all the smoothing plastic, and after 45 minutes, slowly and at a sharp angle, remove the low tack masking tape. Let set overnight and do the same again for the other side. Do not allow the epoxy to cure completely with the smoothing plastic on top, you might not be able to remove it at that point! Sand off any raised fiberglass before you start the top, and repeat all the steps again. If you do a good job, you will be able to stand on the center section and it will hold a 200 lb. guy without collapsing. (But dont try it though! Duh[sm=bananahead.gif])
"What goes up, will surely come down"
And: "Haste Makes Waste, so fiberglass your wings religiously!
Dave the Rave...
P.S.: Let me know if you liked this method......
HERES ONE OF MY 3 GP LEARJETS I BUILT