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Old 07-18-2014, 10:26 AM
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Jetguy Jetguy is offline
Join Date: Aug 2008
Location: Texas, Fort Worth
Posts: 1,237
Default Adding an Aux Fuel Tank!

For all you guys who want more fuel the easiest and cheapest way is to add an aux tank after you are done building. For non engineer types its easier than inventing the wheel. I've had the following setup in my plane for over 500 hours without a problem. The whole setup only weighs 9 pounds. If you don't need the fuel don't fill it up. Weight conscious, only add what you need up to a max of 6 gallons. Headed out beyond round trip fuel simple remove and stop at local gas station for what you need to get back to home base. Provides a lot of capabilities depending on what you need.
Buy a Marine fuel tank from many on line vendors like Cabelas or Bass Pro Shops
Moeller A/D Portable Fuel Tank with Handle

Buy Chrysler brand fuel fittings male and matching female also from Marine supply or Cabelas or Bass Pro, 3 pair
Seasense Chrysler/Force Connector Male
Seasense Chrysler/Force Connector Female

Buy another fuel pump exactly like the aux fuel pump in your plane from Vans

Buy two barbed fitting to put on the fuel pump to slide fuel tubing over

Buy power port plug with built in on-off switch and fuse from Radio Shack
Custom Accessories 18713 12V 5 Amp Lighted On/Off Plug

Buy inline fuel filter
Moeller Universal Inline Glass View Fuel Filter (3/8", 5/16", & 1/4" Barb In Kit)

Buy 2 inch wide nylon webbing with buckle
Cosmos ® 2 Inch Wide 10 Yards Black Nylon Heavy Webbing Strap+10 PCS 2" Black Color Flat Shape Plastic Side Release Plastic Buckles with Cosmos Fastening Strap

Buy 3/8 ID auto-ethonal fuel proof fuel line

Freezer water tubing from hardware store or left over brake line tubing from RV12 build.

3/16 inch long shaft pop rivet

6 hose clamps

Swivel air fitting
Tru-Flate 21-607 1/4" NPT Male Fitting x 1/4 NPT Female Fitting Air Line Swivel Fitting

Nut needed to attach male fitting to filler neck.

Let's start with the 6 gallon tank first. You are going to have to rivet two brackets to the floor of the baggage compartment for the 2 inch nylon strap to go through to hold the fuel tank in place. Put them far enough apart so the tank won't rub on them when in place. Just use some thick scrap aluminum left over from your build to make them. Next you need to vent the tank to the outside air so it won't expand or collapse. Take the swivel air fitting and install it in the filler cap of the tank. The fuel tank in the web link I provided has a vent in the fuel cap you will have to remove and you may have to drill and tap it for the swivel air fitting. Then you need to screw on a male Seasense Chrysler/Force Connector. The thread on the male fitting should screw into the swivel air fitting. You could probably leave the swivel air fitting off if you want but I liked its mobility. Now attach the nylon freezer line to the female Seasense Chrysler/Force Connector. You may need to use a larger piece of tubing to put on the barb of the connector and then push the nylon tubbing in side of it. What ever works for you. Then run the nylon tubing down through the hole in the center of the main spar, where the wiring come through, to the center inspection plate on the bottom of the airplane. In the center of this inspection plate install a long shaft 3/16 inch rivet with the nylon tubing on it like the static ports in the plane. Pop the Mandril out before you attach the other end of the tubbing to the female connector on the cap. Don't worry about the ethanol factor in this line, it won't have fuel in it accept for the occasional slosh when completely fuel on a bumpy ride and it won't be under pressure either. Also leave a little slack in the nylon line for future removal of the inspection plate. Next attach male Seasense Chrysler/Force Connector to the fuel pickup on top of the fuel tank. The threads should match, 1/4 inch NPT. Then connect a female Seasense Chrysler/Force Connector to the end of the 3/8 ID fuel line you can probably picked up at your local auto parts with one of the hose clamps. Remember that this tubing will not be under pressure either but should be ethanol compatible . Then connect this tubing to the barb connector screwed onto the in side of the facet fuel pump. You will need to attach the two Jeggs barbed AN fittings onto the Facet pump. Next attach another length of 3/8 ID fuel tubbing on the out side barb of the Facet pump. Run this fuel tubbing to the right side of the aircraft up past the ELT toward the fuel tank neck. About half way along the top of the airplane fuel tank install the Moeller inline fuel filter using a couple more hose clamps. Then add the last female Seasense Chrysler/Force Connector to the 3/8 fuel tubing. Next mark the airplane fuel tank filler next where you want to install the last male Seasense Chrysler/Force Connector and then remove it and drill a hole onto the filler neck to install the connector. When you insert the male Seasense Chrysler/Force connector into the filler neck you are going to need a nut to install on the 1/4 NPT thread to hold it in place. Which nut fits this? Would you believe a AN bulkhead fitting nut. An AN 6 as shown in the Jeggs web site link will work. It will be a little loose so don't over tighten or you will strip it. Put some proseal on the threads and smooth some around the hole then tighten the fitting on to the nut just slightly past hand tight. Remember this won't be under pressure either, you want it to hold firm but not leak. I mounted my Facet fuel pump inside the main spar using the same bolt that holds the fuel tank in place as you can see in the pics with this post. To do this you will have to cut the bottom mounting tab off so the other tab will line up correctly. Also if you were on a cross country flight and you in plane electric pump failed you now would have a temporary spare. I put 3/4 inch heat shrink over my hose clamps to give it a more pleasing look as you can see in the pictures. Next you will need to wire up your pump to the power port plug with the on/off switch. This will go into the power port when you want to use the aux tank. Couple things to remember. You have to burn off 6 gallons of fuel in your main tank be for you transfer your aux tank fuel. It takes about 20 mins to transfer 6 gallons. Hey it's only a 3.5-4PSI fuel pump. You don't want to leave the pump running dry for to long. Think about setting a count down timer on your Dynon to keep track of your transfer. Also the best part is you can look over you right shoulder and view the fuel filter just beyond the Moeller gage and see the fuel running through it and know for sure when you are done transferring fuel. I think I've cover most of what guys need to know to build and install their own tank. I reserve the right to have left something out or maybe posted the wrong link to a wrong size part. If I have then when you build your Aux tank feel free to post the correction here like when we find a mistake with RV12 plans. Also this is a very simple setup for use in an experimental airplane that can be removed in 5 minutes. Also if you improve on the design the let us all know. If you don't feel safe using it then don't use it. Remember as PIC you make the call.

Maybe the Flightline guys can come up with a hose kit for a cleaner installation.

Pics to follow!
RV12 N1212K
Flying Since June 2010
1020 Hours as of 9/30/2017
RV14 Wing, arrived and building at Rdog's new Hanger at 16X
S/N 140014

Last edited by Jetguy : 07-18-2014 at 10:35 AM.
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