Lately, we seem to be surrounded by fiberglass! In the past two weeks, we have built an empennage fairing, two cowl cheek extensions, and now a canopy skirt, all from raw fiberglass materials. ?Why?? you may ask?.?why are you building those things from scratch?! All the other Van?s kits come with all the pieces you need!? Ahh, grasshopper?.the RV-3 is different?.
The plans and kit for the RV-3 assume that you are pretty good at making compound curves in aluminum sheet and making things fit in a world where nothing is pre-punched and no two airplanes are identical. The cowl cheek extensions are provided as two triangular-shaped pieces of sheet metal with a slight curve and a pair of formed bulkheads that fit about as well as the fuselage bulkheads (which means ?so-so?). The Canopy skirt parts are likewise aluminum, obviously rough-worked on a stretcher of some kind to give a little bit of a bubble shape ? but the curve is dependent on the shape of both the fuselage and the canopy, and no two of those are really alike, so?.no, they are sort of non-starters as well. The fiberglass empennage fairing is nicely in a gel-coated way ? but again, the fit leaves something to be desired because so much depends on how you built the tail feathers. The net result is that it is far easier to learn a little fiberglassing and build new parts from scratch than it is to try and beat these things in to submission. At least they provide you with raw parts on which to build forms and molds!
The canopy skirt is a good example. Once we had riveted on the turtle deck, the boot cowl was finished with screws, and the canopy bubble and frame were installed, it was time to build up a male ?mold? for the skirt. We followed the lead of several prominent and recent RV-3B builders, and referred to Randy and Rob?s pictures quite a bit (and it is impossible to ignore the outstanding composite ?how to? advice of Dan Horton!). We used the supplied skirt material to close out the big rectangular holes on each side of the canopy frame, cutting off what I didn?t need. 3/32? countersunk pop rivets were used in a few places for temporary attachment. The plan was to use lots of clay to form the necessary fillets between the canopy, skirt, and fuselage, but I was quite surprised at how little it actually took ? I think we used about 5 sticks of non-hardening modeling clay (about the size of a stick of butter) for all that we needed. I actually found that aluminum tape worked will to build fillets ? cut it in to short segments to allow for compound curves. The only large area that needed to be build up was a mismatch between the port rear side of the canopy frame and the turtle deck, and again, this was filled in with clay over aluminum tape.
The clay didn?t really need to be smoothed to the mirror-finish that I expected ? uniform streaks in the direction of the airflow seemed to be fine, as we covered the entire mold with 2? electricians? vinyl ?bundling tape? before fiberglassing. This makes compound curves much better than clear mailing tape, and is not as prone to wrinkles. You can also do a little smoothing of the clay underneath once it has been applied. The tape doesn?t really stick to the oily clay, but it sticks fine to itself, so start where you have clean aluminum, then use a generous overlap. It really helped during the lay-up process to draw the expected final outline of the skirt on the tape, both for the bottom edge and on the bubble ? that way, we knew that we had sufficient material where we wanted it. We used an old can of turtle-wax spread liberally on the tape as further mold-release.
We didn?t take any pictures of the lay-up process itself, because for two ?rookie? composite folks, it was intense enough that we didn?t really have time to pick up the camera. In retrospect, we had plenty of time ? we just didn?t want to embed the camera in resin! We used 4 plies of 8.9 ounce ?BID? from Aircraft Spruce to make the layup, layering the four plies on the table and wetting it out that way between layers of 4-mil plastic sheeting. We basically made a single lay-up for each side, a series of strips for the front and rear quarters, and a continuously curving piece for the rear. We used West Systems resin with slow hardener, and in the Houston summer, it was set up firm in about four hours ? but we gave it overnight before touching it, and it is amazing the difference between ?firm? and ?rock hard?. Don?t sand until it is ?rock hard?. And watch out for those splinters ? wear gloves, or you?ll be donating lots of blood to the project!
Once the piece was hard, we pried it off pretty easily and began trimming. We could see our previous markings through the lay-up, and traced these with Sharpies to give us a guide. The cut-off wheel and 90-degree sanding disks made quick work of the excess, and then it was on to final fit. Four clecoes (two per side) picked up pre-drilled holes in the canopy and canopy from ? those anchored the position so that we could drill holes for the latch shaft and mounting screws. And with that, it is ready for endless filling and finishing. It?s good to have the actual structure complete, and the truth is, it only took about four 3-hour work sessions from start to finish. It is about as artistic as it gets in RV construction ? it helps to picture where the air molecules are going to go as they find their way around the airplane.
On to fill and sand!
Paul
The plans and kit for the RV-3 assume that you are pretty good at making compound curves in aluminum sheet and making things fit in a world where nothing is pre-punched and no two airplanes are identical. The cowl cheek extensions are provided as two triangular-shaped pieces of sheet metal with a slight curve and a pair of formed bulkheads that fit about as well as the fuselage bulkheads (which means ?so-so?). The Canopy skirt parts are likewise aluminum, obviously rough-worked on a stretcher of some kind to give a little bit of a bubble shape ? but the curve is dependent on the shape of both the fuselage and the canopy, and no two of those are really alike, so?.no, they are sort of non-starters as well. The fiberglass empennage fairing is nicely in a gel-coated way ? but again, the fit leaves something to be desired because so much depends on how you built the tail feathers. The net result is that it is far easier to learn a little fiberglassing and build new parts from scratch than it is to try and beat these things in to submission. At least they provide you with raw parts on which to build forms and molds!
The canopy skirt is a good example. Once we had riveted on the turtle deck, the boot cowl was finished with screws, and the canopy bubble and frame were installed, it was time to build up a male ?mold? for the skirt. We followed the lead of several prominent and recent RV-3B builders, and referred to Randy and Rob?s pictures quite a bit (and it is impossible to ignore the outstanding composite ?how to? advice of Dan Horton!). We used the supplied skirt material to close out the big rectangular holes on each side of the canopy frame, cutting off what I didn?t need. 3/32? countersunk pop rivets were used in a few places for temporary attachment. The plan was to use lots of clay to form the necessary fillets between the canopy, skirt, and fuselage, but I was quite surprised at how little it actually took ? I think we used about 5 sticks of non-hardening modeling clay (about the size of a stick of butter) for all that we needed. I actually found that aluminum tape worked will to build fillets ? cut it in to short segments to allow for compound curves. The only large area that needed to be build up was a mismatch between the port rear side of the canopy frame and the turtle deck, and again, this was filled in with clay over aluminum tape.
The clay didn?t really need to be smoothed to the mirror-finish that I expected ? uniform streaks in the direction of the airflow seemed to be fine, as we covered the entire mold with 2? electricians? vinyl ?bundling tape? before fiberglassing. This makes compound curves much better than clear mailing tape, and is not as prone to wrinkles. You can also do a little smoothing of the clay underneath once it has been applied. The tape doesn?t really stick to the oily clay, but it sticks fine to itself, so start where you have clean aluminum, then use a generous overlap. It really helped during the lay-up process to draw the expected final outline of the skirt on the tape, both for the bottom edge and on the bubble ? that way, we knew that we had sufficient material where we wanted it. We used an old can of turtle-wax spread liberally on the tape as further mold-release.
We didn?t take any pictures of the lay-up process itself, because for two ?rookie? composite folks, it was intense enough that we didn?t really have time to pick up the camera. In retrospect, we had plenty of time ? we just didn?t want to embed the camera in resin! We used 4 plies of 8.9 ounce ?BID? from Aircraft Spruce to make the layup, layering the four plies on the table and wetting it out that way between layers of 4-mil plastic sheeting. We basically made a single lay-up for each side, a series of strips for the front and rear quarters, and a continuously curving piece for the rear. We used West Systems resin with slow hardener, and in the Houston summer, it was set up firm in about four hours ? but we gave it overnight before touching it, and it is amazing the difference between ?firm? and ?rock hard?. Don?t sand until it is ?rock hard?. And watch out for those splinters ? wear gloves, or you?ll be donating lots of blood to the project!
Once the piece was hard, we pried it off pretty easily and began trimming. We could see our previous markings through the lay-up, and traced these with Sharpies to give us a guide. The cut-off wheel and 90-degree sanding disks made quick work of the excess, and then it was on to final fit. Four clecoes (two per side) picked up pre-drilled holes in the canopy and canopy from ? those anchored the position so that we could drill holes for the latch shaft and mounting screws. And with that, it is ready for endless filling and finishing. It?s good to have the actual structure complete, and the truth is, it only took about four 3-hour work sessions from start to finish. It is about as artistic as it gets in RV construction ? it helps to picture where the air molecules are going to go as they find their way around the airplane.
On to fill and sand!
Paul
