Firewall
I decided to make the firewall in one piece. The material is stainless steel 0.018. A buddy will be guiding me when it comes to shrinking and stretching the material as I form the flange around the perimeter. I started to use the original firewall that I acquired with my salvaged Skybolt, but it soon became apparent that it was not symmetrical :0|. So I decided to use one half of the old firewall as a pattern, then flipped it over for the other half. The initial pattern was from 1/4 ply. This pattern was used as a router guide, from which I routered out a final template out of 3/4" MDF. I then added a 1/8 round-over to the template with the router. For spring-back when bending the flange, I slightly beveled the edge of the 3/4" template. That part was actually pretty tricky: I made a jig for the bed of the router to angle it somewhat, but I couldn't get it to not interfer with the 1/8 radius previously cut. I couldn't add the 1/8 radius afterwards, since the bearing guide would make contact with the lower region of the 3/4 MDF (which would be angled in slightly), resulting in the cutter going deeper into the template (the end result would have been a round over with a 'small step'). So, I did it the artisan way...I scored a pencil line around the template right at where the round-over starts, then I colored in the area below that line (bevel area) with pencil. I setup the bench mounted disc sander at the required angle and gradually worked my way around the template, sanding, until I removed the shaded pencil area. All seemed to come out OK.
The steel sheet was then cut out with some overlap, for now. I then made another cloned template from 3/4" MDF. This had no bevel/round-over etc. This piece sits on top of the primary template, with the steel sheet sandwiched in the middle. This was all then clamped together using 6,000,013 C-clamps (in the UK we call em G-clamps...they do look more like a G...). the top template is there to keep the steel sheet down while the hammering goes on. For final locking reference point, I drilled the top two engine mount locating bolt holes through the whole sandwich. Now I need my buddy to stand over me so I cancontinue with the hammering/shrinking/stretching...
Heel Rails
I decided to keep the flooring to a bare minimum, so heel rails it was to be. These were made from 6061-T6 x 0.063. The most tedious part was fabricating and welding in the attachment tabs. I used 3-sided tabs for where there was no inherent support from the fuselage structure, and simple flat tabs where the tubes would take the weight. An annoying mistake I made on the first two tabs, was to align the tabs flush at the top of the tubes, which is fine - as long as all the tubes are the same diameter :0|. These tubes are like, 7/8, 3/4, 1 1/8 etc. Luckily I only did two before I caught on. I am considering powder coating these heel rails...
Spring Steel Landing Gear
The engine mount is now back from finish welding. I decided to add a torsion strap (see pic). I added a bushing on the outside (see pic bottom right). A slot will be cut through this, slotting through the socket, too. A pinch bolt would then be utilized through the bushing. Iam notgoing to utilize this, for now. It might come in handy, later down the road...
Prior to modification, the engine mount weighed 8 pounds. It now weighs just over 17 pounds. This gives me a total weight for landing gear modification of almost 48 pounds. About the same weight, and a lot cheaper than the Groves gear. If I missed anything from the following comparison, please let me know.
Comparison:
Groves Gear
00.30 - 0.90 4130 various small fillers (ballpark)
39.00 - alum gear (for 1800GW)
00.92 - tube 4130 3/4x0.49x30"
00.60 - tube 4130 3/4x0.35x27"
00.21 - tube 4130 7/8x0.49x6"
00.85 - tube 4130 3/4x1.88x9"
01.30 - support channel 4130 2.5x10x0.90 2 of
00.86 - clamp plate 4130 1.75x7x0.375 2 of
00.65 - bolt nut washer AN6-42A 4 of
02.56 - grove axle 2 of
00.48 - alum bearing block 1x1x1.25 4 of
00.24 - alum radius plates 1.5x7x.250 4 of
n/a - brake linings (gun drilled)
======
47.97
Spring round tapered steel (RV/Wittman style)
35.80 - legs 2 of (custom made for Skybolt S 1800GW)
00.25 - bolt nut washer 4 of (ballpark)
00.30 - 0.90 4130 gussetts
02.00 - fairings & wood (competition balsa) dampers
00.30 - brake linings (best guess)
9.30 - engine mount weight difference (sockets, brace trubes)
======
43.85 47.95
Heel rails locked down. I need a new camera...
Engine mount torsion strap...
