Back Seat Fuel Tank Construction/Plumbing

[apd405]

I am two years into the construction of a new VE.  After reading a recent post from Waiter, I'd like to ask for suggestions/opinions about aux fuel tanks in a Varieze and Pro's/Con's for back seat vs. wing pod tanks, etc.  I am also open to suggestions about plumbing, mounting, and any other idea you might have on installation.  Photos, diagrams, or links to websites would be greatly appreciated.

Thanks in advance,
Trevor
trevorharris@charter.ne t

[Waiter]

I'm not familiar with the VariEZ fuel system, but this is how I did it on the LongEZ:

The tank is constructed out of 1/2 urethane foam, with two layers of BID on the inside and out. There is one vertical baffle in the the middle of the tank. this provides fuel slosh baffle, plus added structural support where the seat belt wraps around the tank to secure it in flight.

(Hardpoints are installed exactly the same way the as the hardpoints used for the low point drains in the front of the strakes)

A hardpoint is installed in the back of the tank to mount the solenoid. The location of this hardpoint is crutial so  that when the tank is installed, the solenoind valve is positioned in the center of the hell hole. A feed tube on the inside of the hard point extends down to the low point inside the tank.

Another hardpoint is installed at the top of the tank. This is were the vent tube and fitting are mounted.  I used a standard ACS fuel cap. they offer one with a welding flange that can be epoxied into the top of the tank.

Make a cardboard mock up first. verify that the tank rests solidly in the seat and does not interfere with the control system. Use the cardboard mock up as a template to cut the urethane sheets. Cut out the foam where the aluminum hard points are mounted, and install these before glassing the sheets. Glass both sides of the sheets with two layers of BID. PEEL PLY EVERYTHING

When cured, cut and trim the sides, bottom, baffle, and top. Fit check everything.

I used small dabs of super glue to hold the sides , bottom, and baffle together, Lay up 2 layers of BID tapes on the inside edges. When cured, cut openings in the baffle, and mount the feed tube to the solenoid hard point. Flox a fine mesh screen over the pickup tube to prevent crap from plugging up the fuel solenoid.

Mount the fuel cap into the top, and drill and tap the vent ard point. The fuel cap is mounted exactly the same as mounting the cap in the top of the strake. However, mount the cap before installing the top,

Prepare the tank top in a similar manner that the strake tops were prepared. i.e. dig out foam in the sides and baffle to form a "U" channel.

Vacuum out the tanks and make sure its absolutly clean.

Fill the "U" channel with FLOX and place the top on the tank, Place weights on it and let cure. Glass two layers of BID all the way around on the top. Where the seat belt wraps around, I added a couple extra layers of BID for additional support.

I bought a couple self adhesive carpet squares, I cut them  and installed on the bottom, back, and sides of the tank to provide a little cussion and scuff protection.

I installed a "T" fitting in the main fuel line just before it passes through the firewall. This is AFTER the main fuel shut off valve. I have a 3 ft piece of AN4 hose connected to the "T". The other end of the hose connects to my BackSeat fuel tank. (When not in use, the hose is capped and tucked away in the hell hole)

A three ft long piece of AN3 hose connects to the high point of the tank to provide vent. The other end of the hose has a 3 inch long tube on it, I insert this tube into the back seat external air vent to vent the tank.

Mounted on the rear of the tank is an electric solenoid with a six ft wire and plug.I have a receptacle on the side of my strake electrical panel that I plug the solenoid into.

USING THE TANK:

It takes about 10 minutes to install the tank. I have to readjust the seat belt and shoulder harnesses to fit the tank. The seat belt goes arount the top of the tank. the shoulder harneses don't really do anything, but I connect them so they arn't flopping around. The tank cannot slide forward, as its wedged into the seat  and thigh support.

I depart with full fuel in the two strakes and the back seat tank. I select the left tank and burn it for 1/2 hour, then select the right tank and burn it for 1/2 hour. By then I'm at my cruising altitude of 17,500 and am settled in for the long haul. The rear seat tank is selected by turning the main fuel valve to the OFF position, and turning on the fuel valve solenoid.

Waiter

[niceez]

You might check with Joe Person.  He made his strakes larger to carry more fuel.  The header tank on the VEZ is essential to the design.  I an refurbishing a VEZ now and am having to make a new header tank because the original builder made it incorrectly and it appears to leak.

A VEZ is not really the type of plane to carry a lot of extra weight whereas a LEZ can.

Dale

[Drew]

I believe that the main reason for a header in a Varieze (sorry, not a VE guy) is that the VE has no fuel sumps.  Would it be better to put a sump in the R/C underthigh support?  Is there enough room?  Just thinkin'.

[apd405]

Thanks for the detailed post, Waiter.  I am certainly aware of the weight restrictions and would only be interested in carrying extra fuel for long range solo trips.  Any fuel system upgrades would surely be simpler if done now while I still have access to the Hell Hole from the bottom.  As for making larger strakes, I have not yet installed the strake tops, but the strake size is already established.  
Niceez, I will try to look Joe up and get his input.  Would anyone recommend installing sump blisters under the strakes or just rely on the header tank above the spar?
Trevor

[Drew]

Most Longez guys are doing their best to get rid of the sump blisters for either a thigh support sump----or like in my Cozy, R/C armrest sumps.  Others keep the underwing sumps but fair them into the cowl.