I'm not sure what this plane is (I bought it used) but it's a glider with a fiberglass fuseleage. On it's most recent landing, one wing tip was a few inches lower than the other, and it pivoted around that point and broke the fuselage back near the tail. I didn't think it was a particularly bad landing, but even so, it broke -- obviously it's quite fragile. Here's a picture (92 KB) --
I've never dealt with fiberglass before. What's the best way to fix this?
Since we're pretty far back from the CoG, any weight added right here will probably mean that I'll have to add an equal amount to the nose, so I'd rather not add much weight if I can at all avoid it.
One suggestion would be to wrap the fuselage forward of the break tightly with wax paper and tape into place. Cut a piece of 4 oz cloth (you could use something in the 2-6 oz range) long enough to wrap around it and about
4"-6" wide . Apply some 30 minute (or longer setting) epoxy to the wax paper and lay the cloth onto it. Using some paper towels, blot out the extra epoxy by laying it over the cloth and pressing it firmly onto it then pull it off and discard the towels.
While the glue's drying, realign the fuse and mark a few reference lines on it so they pass through the break. Pull the fuse completely apart and taking sand paper, rough up the interior of the fuse forward and aft of the break. You can roll the sandpaper around a dowel rod if it helps. Wipe out the fuse with alcohol to get a clean surface.
After the epoxy has cured, pull the wax paper/fiberglass off the fuse and pull the wax paper out of the new fiberglass tube you just molded. Because the tube will be a larger diameter than where it will slide into the broken area, take a pair of scissors and cut a slit down the length of the new tube. Now it should slide into the fuse by either overlapping the edges (put one edge inside the other and compress it slightly) or carefully trim the edges to get an even fit. Trial fit the new tube so you get an even amount forward and aft of the break.
Slightly roughen the outside of the new tube and clean with alcohol. Spread
30 minute epoxy inside the fuselage covering the area where the tube will make contact with the inside of the fuselage. Put a small amount of epoxy on the outside of the tube and slide it into position. Align the marks you made earlier when the fuse is back together again and using clear packing tape, wrap the area to support it as the glue dries. If you have missing areas of original fiberglass, you can fill them in with epoxy and wrap with wax paper to get an even surface.
Sand the outside and finish to your needs.
Of course, you could always use CA to tack the fuse back into place, roughen up the area on the outside and put on a layer of glass on the outside if you're not worried about aesthetics.
I've used this procedure on FG fuses in the past......
Finish breaking off the tail section. Remove the control rods. Clean up the area as well as possible. You'll need to determine if the construction is epoxy or polyester glass... mix up a small amount of patching resin and paint the inside of one portion of the fuse with it lay in 4 or 5 strips of .014 X 1/4" carbon fiber, spaced evenly around the fuse. Take a long skinny balloon, spray it with Pam as a release agent, then drop it inside the fuse asn partially inflate it. Adjust the position of the carbon fiber strips the finish blowing up the balloon...
Remove the balloon after the resin has cured. Put a coat of resin into the rear portion of the fuse and on the exposed carbon fiber strips. Slide the rear portion of the fuse into place.
Take another balloon and fabricate an extension from some type of tubing that will allow you to position the balloon inside the fuse across the break, working from the wing saddle. Inflate the balloon and align the fuse parts. Let the repair cure and yank the balloon... Fill and sand the break. It would be best to wrap the area with a layer of .5 oz cloth, but may not be necessary if the break is clean enough...
It may break again, but it won't be here... Weight should be no problem as long as you use thin coats of resin...
Judging by the picture alone, it appears that the glass wasn't completely filled with resin during layup. This will make for a very weak structure. About the only way to repair this so that it doesn't look bad is to cut the fuselage apart at that point, clean it up (loose fibres, etc) and stick it back together with a layer of cloth on the inside.
I would cut a piece that is about 3" long and roll it into a tube to fit into the front half. Make sure that it approximates the taper so that the rear half can slide on later. Use LAMINATING epoxy. Finishing epoxy will not bond well to others. Sand the inner surfaces with some heavy grit like
80-100 so that the surface is good and rough for adhesion. Roll up the joiner so that it fits into the front half and use a small bit of tape to hold the shape for the rear half. Leave half sticking out for the rear fuselage part. Mix the epoxy and saturate the entire joiner. When the epoxy is almost completely cured (cooling off a little)remove the tape and mix up a bit more and slop it on the joiner and the rear fuselage where it will interface. Slide the two parts together and wipe off any excess now. Block. brace and set so that the fuselage stays straight until the epoxy sets.
Looking at your picture I also see some cracks. Best to reinforce these from the inside before joining.
I see that the fuselage is Kevlar back there. Here is the simple way:
Bend back the fuselage so that it isrealigned and straight. Put 2 popsicle sticks along the sides and one top and bottom and tape them to hold the fuselage straight. Now, take thin CA and drop a few drops onto the tears. The CA will fume very rapidly, so get your nose away from it. One glued, take off the popsicle sticks, and use a file to remove all of the lumps caused by the CA. The fuselage should be in one piece now, lighter than its original condition, and ready for your patch.
Since it is made of Kevlar, it would be best to put a Kevlar patch on, but I've used 1 1/2 oz cloth, 3layers, in a pinch. Cut the patch cloth on a 45 degree bias, about 2 inches wide, and long enough to wrap the circumference of the fuselage 1-1/2 to two times. Dust on a coat of 3M77 spray dahesive and let dry, then wrap the cloth over your boo-boo. Smooth the cloth out with your warm hands, and the
3M will tack the cloth neatly over the fuselage. Now, mix up your favorite surfacing epoxy and wet out the cloth. Once the cloth is wetted out, wipe off all the excess with a roll of toilet paper, and wrap the entire mend with packing tape, overlapping to the unbroken fuselage. Let this cure, remove the packing tape, and sand off any remaining ridges. This mend takes only about 20 minutes, but it took me 10 minutes to explain it.
| Seems to me that to repair it without adding weight will pretty much put | you in the pray for a miracle league. With all that's going on in the | world right now I'd say your at the very back of a real long line.
I didn't say I expected to fix it without adding any weight. I said I'd like to avoid adding much weight if possible. I'll show you the relevant part again --
| >Since we're pretty far back from the CoG, any weight added right here | >will probably mean that I'll have to add an equal amount to the nose, | >so I'd rather not add much weight if I can at all avoid it.
In any event, I've got some things to look into now. Doesn't sound like it should be too bad, but yes, I will have to add some weight -- but that was expected.