RV-4 FUEL TANKS
This Page Last Updated : 05 December 2004 01:55
RV aircraft use integrated wing tanks that are constructed separately from the wing and bolted on to the forward edge of the wing spar. The wing tanks are a sealed, wet-wing type and comprise a section of the wing, forward of the wing spar, and extend from the wing-root to about 3 feet.
When I purchased the kit, the wing tanks were started. The tank ribs were formed and the skins cut and bent to size. Most of the holes were already drilled for the skin-to-rib rivets, but little else.
??? : I got the inboard rib all done and riveted. The access panel ring, fuel vent elbow and sender connector have all been installed and sealed. This picture shows the rib before riveting and sealing. I'll post one in the future after sealing and riveting.
??? : The bottom tank stiffeners with Pro-Seal applied during and after riveting. Note the anti-hang-up bracket going from the #2 Rib to the inboard Rib. The plans in the Van's manual aren't terribly precise, so I basically winged it a little and made sure that it won't let the flop-tube get caught on anything. You can also the surge gate that I installed in the #2 rib. I also took the advice of a few people who recommended that I drill a few more holes for internal venting when fueling. I guess when fueling with a more-than-capable fuel truck, the air has trouble escaping through the holes in the tops of the ribs.
??? : Installation of tank surge flapper. This is similar to a surge box found in commercial and military aircraft (like my beloved P-3 Orion). It is a simple flapper installed in the most inboard internal wing tank used to maintain fuel in near the inlet during radical attitudes and maneuvers with lower fuel quantities. It allows duel to free-flow into the inboard-most chamber, but will shut if the fuel in the inboard-most chamber tries to spill back into the rest of the tank as might happen in yawing motions or a slip.
28 Mar 04 : I tried to get something done today, but I had been up for about 20 hours, since I had to work from midnight to 8 a.m. All I did was trim the stiffeners to clear the capacitive fuel quantity senders. I know that Van's plans (hey that rhymes!) calls to cut notches in the sending plates, but I didn't like that, so I trimmed the vertical portion of the stiffeners. It only needs to be done on 2 of them in each tank.
17 Mar 04 : Dimpled some of the ribs and clecoed the tank together to make it easier to rivet. I actually riveted the stiffeners that I did the normal way, instead of back-riveting them, though I know most people will recommend it. I just decided to try it that way.
14 Mar 04 : Every RV builder truly looks forward to the time when he/she gets to enjoy the aroma of Pro-Seal. The only things we enjoy more than that the aroma, is the pleasure of riveting components with wet Pro-Seal. After mixing a small tube of Pro-Seal, I Riveted 4 of the stiffeners to the Tank skin.
Yes, it's a pain, yes, it smells, but it's not as horrible as many make it out to be. I've been using the stuff in the Navy for 17 years, so I guess I've gotten used to it.
Most of the jobs I see done with Pro-Seal, the stuff looks like it was put on with a hand-grenade. Here's the trade secret to working with the stuff.
First: Mask anywhere where you don't want the sealant. 'Nuff Said.
Second: Use your worst clecoes, because they WILL get sealant on them and IN them. I have a container with paint thinner to soak them in. Even if the stuff does set-up inside the cleco, you can usually work it enough to get most of the stuff out eventually.
Third: forget the plastic gloves! I never use them. Instead of avoiding the stuff, embrace it. Dive in! Typically, I use one hand to work with placing and forming the sealant, and the other hand I keep clean and use it to smear and smooth the sealant. you're going to get the stuff all over your fingers, but it comes off with paint thinner or naptha (coleman fuel). I think paint thinner works better than naptha. You just have to use some disposable rags and wipe hard, but it comes off.
Fourth: Use your clean hand to smear and smooth the sealant. But here's the trick, you have to constantly lick you fingers. I haven't tried water, but I think it works the same way as shining shoes. Water just doesn't work as well as spit (That's why its called a 'spit shine', right?) Lick your finger, smear the sealant, lick again.
Once you get the hang of it, you'll realize that you can make sealant jobs look so much better and I think its much less hassle to ditch the gloves and just dig-in.
12-13 Mar 04 : Dimpled and countersunk Tank skins and stiffeners.
10 Jan 03 : Dimpled The LH Tank skin.
22 Dec 03 : With some new tools finally in-hand, I was able to start dimpling the parts of the fuel tanks. I've still got some more to do, but it'll have to wait until I get a return spring for a C-Frame that I am borrowing from a friend at the EAA Chapter.
27 Sep 03 : Even more sanding on the T405 brackets. Drilled and smoothed holes for capacitive fuel quantity (CFQ) sending plates, wiring, and vent lines. Riveted plate nuts on CFQ plates and temporarily mounted. Started soldering wiring for CFQ system.
23 Sep 03 : More sanding on the T405 tank brackets. Its going to take forever. I can only work on them for about 10 minutes at a time before they become too hot to handle (from the sanding). I also did some drilling and fitting of parts on the ribs. These started out as a hunk of 1/4" thick 2"x3" aluminum angle.
13 & 14 Sep 03 : Cut, drilled and rounded edges of tank stiffeners for both LH and RH tanks. For the T405 tank brackets, I gave up the die grinder and started using a belt sander, and that worked much better! Here's a picture of the tank stiffeners. They will get riveted to the bottom tank skin, between the ribs so as to keep the bottom of the tank from bulging from the weight of the fuel.
July 03 : Did rough cutting of T405 tank brackets using band saw. Took a lot of time. Started cutting and flaring of vent tubes.
May 03 : Measured and drilled holes for fuel tank caps. Cut slosh holes in ribs, and holes for capacitive fuel sender units.