Post by thevon on Apr 15, 2009 7:27:47 GMT 10
This is my new JW60 just finished. I got the kit from Kane, and used big golf club spars in (same as Reaper) and a 2nd 6mm solid carbon spar (from my Bat) aft of the main one, allowing enough space in between them for the standard sized servos. It has the ballast tube from the Reaper. The servos are HS5475HB’s which I reckon are fantastic value, digital and super strong, no slop.
I covered it in 150micron laminating film on top and some Ballisticover light on the bottom, which Swoopdown gave me ages ago. It was able to go full span with no joins or cuts, and the tips came out well.
The silver foil tape is some stuff they use to join sheets of “Aircell” plastic insulation, used in prefab garage sheds. I loved the look of the Aircell for making wingbags so I snaffled some offcuts. I had to spend about $30 on a big roll of the tape, but it’s amazing stuff. It has a backing paper to peel off, and the glue sticks to anything. The tape is quite thin and has a thread in it, and is very strong and hard to break. So I decided to try using it for a few things including wrapping around the tips, hingeing the elevons, and covering the fuse.
I fitted a carbon dragspar (again, leftovers from the Reaper). The wing was gooped first. Then spackled and sanded about 3 times with about 10% PU glue and a bit of water mixed with the spackle. Then it was thin-gooped again a couple of times and the laminating film applied straight on. This all happened pretty slowly so everything was dry before the next treatment. I didn’t use any bi-di tape anywhere. I used the wife’s iron because my hobby one ran out of heat too fast. I never seem to get a perfect finish with the lam film on EPP, but it’s not bad.
The elevons were covered in 150 micron lam film too, lapped over a few mm at the TE. I have a couple of inches of fixed elevon at the tips. You have to run the aerial out of the wing because I’ve found from bitter experience that golf club spars and carbon dragspars block the signal really badly. I “Y” the aerial near the Rx and run 2 wires, one to each wingtip and dangle them back from the fixed elevons. Seems to work really well.
I shaped the fuse in minutes using my new bench belt sander- woo-hoo, this thing makes it so easy! Then fitted the battery pack into the nose and a lead running back to be joined to the wing switch. I cut little trenches and laid 2.4mm glass rods (kite spar, dirt cheap) along the fuse to brace it. Then gooped the fuse heavily a couple of times. Then a layer of bi-di tape (doubled at the nose) sanding between layers. Then ironed the tape to “bed it in” then more thin goop. Finally I covered it with the foil tape, which was one of the easiest things I’ve done.
But the big innovation with this plane is the method of fitting the fuse to the wing. I’ve tried to dream up ways of fitting the fuse that don’t involve gluing. The idea here is that I’ve epoxied very thin ply to the wing mating surfaces of the fuse, allowing it to stick out about 8mm. I pressed it all together when the epoxy was setting and it’s a perfect fit. Once I’d routed the battery wire into the servo bay and tested it all out, I taped the ply lip to the wing using the foil tape. So far it feels solid as a rock.
Then I just put colour onto the wings using foamie tape. For me this is the best method because it really sticks well, is quick to do, and you can iron it.
I was a bit shocked at how much nose weight I needed to balance it to the CG! The threads seem to reckon 2 5/8” is the best starting CG and it took 290gm of lead to do that! I made a mold out of alfoil and poured molten lead in to make a neat brick.
The AUW is 1.74kg! I was a bit shocked, but the guys on the JW threads seem to reckon that’s a perfect weight for DSing (60 ounces). Various guys told me not to build it light, so I’m happy that it’s pretty much on the mark.
