TIGHT WING TUBE FIX
02-23-2007, 04:31 AM
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TIGHT WING TUBE FIX
Putting together a 50 cc class ARF, I decided to replace the well-fitting (!) supplied aluminum wingtube with CF, to save 5 oz. CF tube was very tight. It would start in, but not go more than an inch into either wing or fuselage socket without binding up. E-mailed the ARF mfr, who I know as fellow club member, and asked what his recommendation was for enlarging the ID of the sockets. He urged me to instead sand the OD of the CF wingtube, taking dust precautions, rubber gloves, wet-sanding with fine grade sandpaper.
I followed his advice, and found it very slow going, taking it outdoors to sand, counting the strokes, coming back in, wiping the tube clean, dusting it with talcum powder, trying the fit, finding I had made very slight progress after a lot of sanding. After a couple frustrating hours, several trial fits and finally a dinner break, I pondered the matter, noticed the wingtube was now smooth as a baby's bottom, but the inside surface of the sockets was relatively very rough.
Decided to attack the ID's, as per my original plan. Tried a few different methods, wasted another hour or two with little progress.
To make a long story short: for a 1-1/2" wingtube, to sand out the interior of the sockets, the perfect tool is the cardboard tube in which Dubro ships its 2-56 threaded rods. By itself it is just shy of 1-1/2" diameter. But if you wrap the end with exactly two layers of Great Planes adhesive backed 80 grit sandpaper, it just fits inside the socket and can be twisted down the full depth of the tube. The first few twisting passages are tight but doable, and after just a few you can feel it loosening up and pretty soon make a straight up & down plunge stroke. Make a few strokes, try the fit, make a few more, try again, and in about thirty minutes I had a nice snug slip-fit on both wings and fuselage socket.
I followed his advice, and found it very slow going, taking it outdoors to sand, counting the strokes, coming back in, wiping the tube clean, dusting it with talcum powder, trying the fit, finding I had made very slight progress after a lot of sanding. After a couple frustrating hours, several trial fits and finally a dinner break, I pondered the matter, noticed the wingtube was now smooth as a baby's bottom, but the inside surface of the sockets was relatively very rough.
Decided to attack the ID's, as per my original plan. Tried a few different methods, wasted another hour or two with little progress.
To make a long story short: for a 1-1/2" wingtube, to sand out the interior of the sockets, the perfect tool is the cardboard tube in which Dubro ships its 2-56 threaded rods. By itself it is just shy of 1-1/2" diameter. But if you wrap the end with exactly two layers of Great Planes adhesive backed 80 grit sandpaper, it just fits inside the socket and can be twisted down the full depth of the tube. The first few twisting passages are tight but doable, and after just a few you can feel it loosening up and pretty soon make a straight up & down plunge stroke. Make a few strokes, try the fit, make a few more, try again, and in about thirty minutes I had a nice snug slip-fit on both wings and fuselage socket.
