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Installing the Special Inverted 29 gallon Fuel Tank

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Ed T

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Spent part of last month installing the special inverted 29 gallon fuel tank in my Skybolt. I had read many descriptions of difficulty fitting this tank into the Bolt, so I took some pictures along the way to document the procedure for others who follow. Please note: I have the tank described by Mac McKensie in the May 77 issue of his Skybolt News, pages 4-7. The flop tube in this tank is installed in the rear of the sump. I believe Hale Wallace later moved the flop tube flange to the front of the sump in his update of the plans, and this where I believe it is also located in the tank sold by Steen Areo Lab. The right diagonal cabane and front instrument panel were removed during the installation. I highly recommend that you have capable help when you attempt this. Helper shown in second photo. You can see in my photos numerous locations are covered with heavy tape to protect the tank and the powder coating on the fuselage frame. The first three photos show the orientation of the tank before it is lowered between the upper longerons between stations 0 and 24.
Left Side.jpg
Front with Helper.jpg
Front against Cabane Tab.jpg


Note in the last photo above that the front of the tank is hard against the cabane tab to maximize clearance at the rear of the tank. The next two photos show the two interferences that must be resolved in the next stage of tank installation. The first is the flop tube flange on the cross tube at station 24. The second is the sump drain flange that must move past the upper right longeron.
Flop Tube Flange under Tube at Sta 24.jpg
Sump Flange past Right Upper Longeron.jpg

The small signs on the tank show the order in which these conflicts were resolved with small movement of the tank from the initial position shown in the first three photos. We had the tank in and out several times and on subsequent tries, and we found out either one of the pipe flanges could be positioned first. If you have a newer tank with the flop tube flange in the front of the sump half of your problem may already be solved. After both flanges are below the interference the tank can be rolled level and lowered into position.
In Position.jpg

Here is he tank lowered into position. Lower tank straps are loose and the tank is sitting on the diagonal tubes in this bay. My tank had less that 3/4" clearance on each side between the upper longerons. To maximize space behind the rear of the tank and the the front instrument panel, the front of the tank was positioned 3/4" from the upper cross tube at station 0. This allowed room for the two tank vent lines at the front of the tank, however it will be mandatory to install the top two bolts for the engine mount through the spools before permanently installing the tank. The sides of the sump had bulged out slightly during welding and fabrication of the tank. After protecting the tank with sections of silicone hose on both diagonals it was necessary to pull the tank down into final position with the top straps with the lower straps loose. In final position the front of the tank was 1" lower than the rear to gain clearance below the coaming that covers this bay. Fabrication and fitting of the tank straps was another full adventure that I will detail later in this thread.
 

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