More changes/bench trimming

I've been slowly adding tail weight to the P-51 to get more sensitive controls. I can afford to do it because of the stability. I can trade some to get the control feel I think it should have. The other day I remembered a nitro pipe set up I bought from Fox Mfg. years ago for a .40 size engine. I never used it. But now the exhaust adapter and exhaust pipe tube screw together unlike other headders that are welded. I took the assembly apart and found it would fit the Fox .45 exhaust port. Now all I need to make a very light. sort of muffler is a tube to fit into the exhaust adapter. Sort of like a tongue muffler only different. This one is free. After a short search I found some aluminum tube that I used for tuned pipe extensions on the r/c pattern planes. The tube almost fit into the threaded portion of the adapter but needed to be necked

down a bit. In my basement is a small wood lathe that has a chuck to hold small pieces of wood. I put the tube in the chuck and tightened it up. After several tightenings and fittings the tube was necked down enough to fit tightly into the exhaust adapter. Now to close up the other end of the tube. I figured the tube shouldn't be closed completely so I found a steel washer that almost fit and ground the o.d. of the washer down to make a tight fit in the tube. I used a tubing cutter to make an indent in the tube so the washer wouldn't go too far in the tube. Then I bent the end of the tube inward to capture the washer securely. I calculated the area of the exhaust hole in the stock muffler and the hole in the washer and drilled some holes in the wall of the tube above the washer to equal the area of the hole in the muffler. OOPS. A slight miscalculation on the area. Now how do I close the holes without having to make a new tube assembly.I thought about using some window screen rolled up and inserted into the tube through the hole in the washer but I couldn't get any as the neighbors were home. Then it hit me I could take a piece of a screw

clamp with the slots in it and roll it small enough to fit around the outside of the tube over the now too many holes. It worked. Making the new muffler served two purposes, it took two ounces of weight off the nose which kept me from adding weight to the tail and it reduced restriction on the exhaust which will give more power. A couple days prior to this session I got some advise on how to fix a problem I was having with the engine run when it was inverted. I was advised to lower the tank in relation to the engine. I did and it helped. I also noticed that engine vibration on the plane was causing air bubbles in the fuel feed line to the engine. Now how do I insulate the tank from the vibration and keep it adjustable. The original setup has a slotted arangement that is bolted to the plane. I made a metal tray with many holes instead of slots and hooks to rubber band the tank to the tray. I glued a piece of foam padding under the tank and when I test run the engine to check the muffler there were no bubbles in the fuel line.