Original Posted By: "Ken Rickards"
Subject: Pietenpol-List: Fuel Tank RequirementsI recently sent Ed G. some ideas on how I did my fuel tank...thought I might post it to the group.First, I set out my design criteria : 1) No fittings in the cowling, so there is no chance of fuel leaks inside the cowling, or passenger compartment.2) In the tail down attitude (static laden) all the water in the fuel must make it's way out of the tank, to the gascolator.3) Make use of every available cubic inch, for fuel quantity.4) Simple, effective fuel quantity indicator, while in flight. - Cork / Wire in the filler cap of the cowling tank, like on a J3 Cub. Each of my two fuel caps also has a 1/4" copper ram tube J.B. welded into the caps, and 90 bend pointing into the slipstream, to keep a positive pressure in the tank. I made my fiberglass cowl tank with the flanges on the sides of the tank, to rest on the top of the longerons. The flanges are about 10 layers thick, with the layers laid 90 bend to the exterior of the tank. I used polyester resin, and at least 4 layers of fiberglass on both tanks. I used several extralayers around any fittings and mounts. I put a lot of time and thought into the mold for the tank. I made the inlet on the top left side, (at about 10 O'clock pilot's view), and made a fiberglass blister stand outboard of the cowling, to prevent posibility of leaks entering the cowling. The outlet is alsooutside of the cowling shelf, and points forward, through the firewall. The bottom of the tank slopes forward, while in the tail down attitude (as it sitsin the hanger), so any water in the tank makes it's way all the way out of thetank, and into the gascolator (a very important design criteria). The aft bottom also has a step in it, that also sloaps forward, to make use of the spaceall the way back to the cabane cables. I used the aluminum 'weldable fittings' that AS&S sells, grinded the outboard ring off, and glassed them in at the inlet and outlet. On the outletside, I modified a finger screen, so it threads into the 'weldable fitting', bytaping the o.d. threads, and then install the 90 EL, which threads into the 'weldable fitting' on top of the finger screen. To service the finger screen,the 90 EL has to be removed first. As a result, I was able to squeeze a lot of fuel in the cowling tank. It holds 10.7 gals. I didn't know how much fuel it would hold, till I did a leak test, by setting it up at the gas pump, at the angle the tank sits in theplane with the tail down, and put one gallon in at a time, then dipping a stickinto the fuel, to mark off each additional gallon. That's how I made my 'FuelQuantity Indicator Stick'. I topped it all the way off, then put the full tank in my trunk, brought it home and left it sit for 3 or 4 days to check forleaks - No Leaks !! My wing tank holds 9.8 gals. so my total fuel onboard can be 20 gal. That's a lot of fuel. I don't think I could sit there long enough to burn that much fuel at a time, but on the way back from Oshkosh, I diddo one 4 hr leg, and two 3 1/2 hr legs, and still had plenty of reserve. But you know what they say - "The only time you have too much fuel onboard, is whenyou're on fire !!" It was quite a chore to design and build this tank, but it all works very well, and I'm pleased with how it turned out. A note about fiberglass fuel tanks: It is of utmost importance, that you NEVER use any fuel with alcohol in it. It will soften the polyester resin, and you'll have to scrap the tank. My scanner stopped working, so I can't send you any pics. I sure wish I could send pics that I took, as it would easily explain what I've just put in text. Let me know if you have any other questions.Chuck G.From trees & rags,to Stick & Rudder -"Contact" hot mags,Pietenpol's are Forever !!________________________________________________________________________________