I Then coated the foam with a spackle made of epoxy and microballoons. pic surf57, 58
The epoxy and microballoons will seep into the surface of the foam to make a hard solid surface that can be sanded smooth. This coating will also keep the mold in it’s curved shape. Remember that the foam is mounted on plied balsa which is tacked to the frame. After sanding the rails smooth. The whole piece of foam and the balsa mount will be removed. I will lay wax paper on the bare rails to protect the board and then tack the foam mold back onto the board. with the wax paper in between. Then I will coat the mold with release wax and lay my kevlar on. After it dries I will remove the mold from the board and I should be left with a kevlar shell shaped to fit the frame.
A big problem with the r/c airplane hobby is that nobody builds airplane kits anymore. The industry has moved tward pre built almost ready to fly airplanes which need minor assembly to complete. There are only few people building kits these days, and a tiny fraction of those people actually deign and build their own aircraft. So in the end, there is just a few scattered builders without any contact. Its rather unfortunate. Thats where I fall in.
ARF planes suck! I’m a novice compared to you, but I’ve designed and built two planes from scratch. It’s a much more fun experience to turn a flat sheet of balsa into something that flys. Buying an ARF (almost ready to fly) airplane would be like buying a machine shaped surfboard blank where all you had to do was final sand it. There’s no room to try something new.
My rails will have a balsa carbon framework with the hollow molded kevlar/carbon shell on top. I need to make stringers for the framework. I have decided to make balsa/carbon stringers. I made 80" long molds to make the stringers. They work by sandwiching strips of 1/8" x 1/4" balsa and carbon tow. The carbon is brushed with thinned epoxy, the balsa and carbon is then squeezed in the mold from top to bottom and side to side. Excess resin is allowed to squeeze out of the seams. Check em out.
Im still waiting on a uni carbon strip for the bottom of the stringer… meanwhile, a buddy of mine dropped off a plane for me to assemble, a 1/4 scale Russian Yak 54 aerobatic plane. This thing is huge!! 81" wingspan and a 27cc engine. It looks something like this.
I got my uni-carbon today!!! Now I can start laying on the skins. Im so excited.
I’ve got the plane almost done, here is a pic to put its size in perspective. It takes up most of the space in the shop. What’s really sick is that there are guys out there who consider this a “small” airplane.
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Where is there to fly those things anyways?
In St. Pete, there is a field called SPARKS on the corner of 275 and Roosevelt. It’s behind the fire station off Roosevelt.
There is another field just north of 686 and alt 19 but I’ve never been there.
I was up there this morning… Had to take my mom to the airport at 5am! :eek:
I’ve gotta arrange some time to head over there and check that out still… School MWF 8-3 Work Tues, Thurs, Sat 9-5… I think I’ll give you a ring on Sunday.
My only percievable use for Dow blue foam is as a nice surface to lay up some skins.
Im sorry that I’ve been slow with the updates. I had a disaster a few days ago when I pulled the sand-bags off the skin. The sand bags sank into the open rib bays and made big dimples in skin on the bottom of the board as deep as 1/4". It never crossed my mind that the veneer would flex that much. I was lucky that the epoxy wasn’t completely dry and I was able to rip the skin off without doing much damage. I have since glued the skin back on and I put a slice of Dow blue foam between the skin and the sandbags to give more support. The result was much better but not perfect. The deepest dimple was about 1/16" deep after the second attempt. Then I took a 8 sheets of 1/16" x 4" x 48" balsa and layed them up on the bottom of the board with some 3M-77 spray adhesive. Then I sanded the shit out of it with a BIG LONG FLAT sanding block. I am pleased with the results. Now I have a smooth flat bottom. This did not affect the concave at all because that was built into the frame.
I also glued the first layer of skin on the top of the board. I didnt have the dimpling problem because of the extra support from the sub-deck and the domed effect. The top is belted with 2" carbon tape along each rib. It is super strong. I also set up the first hollow kevlar rail. It is drying tonight and I can pop it out of the mold in the morning. Sorry, but I don’t have any pics of the recent progress. I will post them soon.
