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Cardstock Pattern/Stainless Steel Part
My RV-6 does not have a cabin heater. The exhaust muff heater that is on it now, is used for the carb heat.
Carb heat keeps the engine running in high humidity days that can develop carb icing. I'd rather be cold than have the engine quit. Last April when I flew to Mt. Denali for photos, I froze. Decided that I would find away to add another heat muff for heat to the cabin. Last summer while my engine cowling was off for fiberglass repair, I measured and built some patterns for a cabin heat muff. A heat muff is a small "pipe" that goes over the exhaust pipe trapping the heated air off of the hot exhaust pipe. You then use "scat" tubing to route it to a cabin heat control box. All my patterns have been first drawn and printed onto cardstock. Cut out and then taped into shape before fit testing on the actual exhaust pipe. My pipe has a 135 degree angle bend in it. This has created an issue with the outside heat muff. Finally after testing found a shape that will work. It is an open end truncated cone, just like nosecones or rocket cones. It has a 3" wide opening at the front, tapers along the main body (9"-long) to a 2-3/4" opening at the rear. Exhaust pipe is 1-3/4" O.D., so a spacer will be added to the rear to block air-loss. A hole will be cut once the muff is rolled to the correct shape and a 2" diameter Stainless steel tube will be inserted to remove the warmed air. Lessons learned from designing fuselage and rocket bodies, I know that you can't just draw a circle and the 2" dia pipe will fit. Drew an ellipse shaped hole for the pipe. Today I used the final pattern to mark the shape onto some 26ga stainless steel. After marking I used a sabre saw to cut the stainless steel into shape. Total part count is 7-pieces. Next step is to "pre-shape" just like cardstock. Will roll it around a 2" PVC pipe. For glue, will be using a TIG welder and some 308L 1/16" Tig rod. The side seam will have stainless steel self taping screws to seal the seam along the body length. The screws make it easy to install or remove as needed. A few photos of what I'm doing you can see the main SS part under the cardstock pattern. Cutting the rear curve pieces in these photos-good thing I stopped for photos; realized my mistake=the inside curve needs cut first, that way I can hold the larger piece while cutting. That's all for now. Will show more photos as project continues. Drill the screw holes next before the pre-forming rolling takes place. Mike |
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