Carlson Skunk Works

Well, it is time to add another update on the progress that has been made on Sawdust. However, the progress that has been made really doesn’t show very much.

The summer has been very hot and VERY busy. Two weeks ago we were planning on going to Minnesota on Friday to attend the 125th anniversary of the church that we grew up in. Then our son and his family let us know that they would be visiting from Dallas on Wednesday and Thursday. To top things off my brother in law’s brother in law passed away and we drove to Minnesota for the Tuesday funeral. Therefore, the week ended up with two trips to Minnesota. Last week I had two days where I had to start work at 1:00 AM, then on Saturday we had promised to take our youngest son to Omaha to catch a 6:20 AM flight to California to visit his oldest brother. That meant another 1:00 AM start.

Yesterday I spent the whole afternoon inside the plane! I was working on drilling the pilot holes for the mounting plates for the rear spar attachments. It was hot and when I was done I just tossed my shirt in the washer because it was soaked with sweat.

So. What have I gotten done? The fuel tank is done!

I got the materials through Gary a friend of mine who has a machine shop here in town. He ordered the aluminum and then sheared it to the major dimensions. I proceeded to lay out the other required cuts and bends. I did the bending then turned it over to my friend Fred who offered to TIG weld it for me. Fred did a great job of welding and pressure testing it. He dropped the finished tank off at my place last Monday.

To pressure test the tank I had to come up with some way of plugging all the holes/openings in the tank and a method of pumping air into it. There were three holes that I had to deal with, the filler hole, the hole where the fuel gauge sender unit fits and the hole where the gas will come out to go to the carburetor. The two larger holes were plugged with plugs that are designed for plugging plumbing lines for pressure testing. I got those at Menards. The fuel exit hole was plugged with some plumbing fittings and a air valve similar to the valves used on bicycle tires.

Fred had removed one plug and welded a thick ring of aluminum to the tank where the sender unit would be mounted. He then positioned the sender unit and drilled and tapped holes for the mounting screws to go in. I think this will provide a very nice and secure method of mounting the sending unit.

I removed the other plug which was in the threaded filler neck adapter. This was a weldable aluminum piece with threads on the inside where the filler neck can be screwed into. I bought the adapter, neck and cap as a set from Aircraft Spruce. The only “problem” is that the filler neck is quite short. It must have been designed for installations where the tank sits just under the skin of the airplane. Maybe for wing installations.

I grabbed a couple of ropes and tied it into place in the plane to start figuring out how to do the final mounting.

It fits!

However, the top of the filler cap is below the level of the plywood deck.

The fuel tank will clear the rudder pedals. You can see the air valve still in the bottom of the tank. I will need to take that out and install a fuel valve. The fuel line will then go from the valve through the firewall to the gascolator.

The filler location is toward the top and the fuel gauge sender is toward the bottom. The fit within the windshield frame pretty nicely.

The top of the filler cap is definitely below the plywood deck. Hmmm …

I guess I will have to think about how to proceed with this for a while. In the mean time I will need to come up with a way to mount the tank. The weight of the full tank should be somewhere around 120 pounds. This is an 18 gallon tank according to the plans. I tried to follow the plans very closely. I am thinking that I may run a piece of 4130 tubing across the inside of the nose at the rear of the tank and secure a couple of straps to it. Maybe the next time I post I will have it figured out.