What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

diamonds and stones

Dan_E_Root

Active Member
Ladies and Gentlemen, come share with me my misery and elation.

Yesterday, we put two gallons in each tank, pressurized the fuel system with the boost pump and checked for leaks. After tightening up a couple of fittings, we gave her the once over a second time. Finding no new faults, we started my brand new mattituck for the first time. It ran like a champ, the prop tracked true, the spinner looked like it was stationary, God was in His heaven, and the sky was never so blue. I was JACKED UP! What a GREAT DAY!

Later in the day I put five gallons in each tank, and went home. Today there was a puddle under the fuse, and a quart of gas under the seat. It was seeping through one of the aft rivets along the spar in my quick-build tanks. It ran along the seams through capillary action, through the wing root, and accumulated in the fuse. Some of it just dripped onto the ground dissolving the tar in the tarmack under my hangar. I cannot possibly express on this forum how genuinely displeased I am.

Well I pulled the tank off (you guys know how many bolts and screws there are), drilled out the offending rivet, cleaned up the hole, prosealed both sides of the hole, smashed another rivet in there, daubed the shop head with more goop, and cleaned off the manufactured head. Maybe that'll stop the leak, but the true cause of the leak is inside the tank. The proseal installed during assembly along that spar didn't seal very well, got dried out, or whatever. I understand this happens sometimes, and the guys who built this tank did a good job as near as I can tell. But @)#*&#!!!

I'll pressure test the tank tomorrow after the new proseal has cured, looking for bubbles. If it didn't work and I need to do something more, maybe I can get inside with some kind of elongated whizbang thingamajig to slather some proseal in the offending area. (the leak is through that the freakin' rivet along the back row, smack in the middle of the tank along the bottom).

Yesterday was a diamond. Today was coal, but it's gonna be a diamond someday... :p
 
If I understand correctly, you have a leak at the joint between the tank skin and the tank aft baffle plate, at the lower joint. I had a similar leak (upon testing) and fixed it thusly: I drilled out the rivet at the site of the leak plus a few rivets on either side. I filled a 5 cc plastic syringe with proseal and used a 16 ga. (ie: large diameter) needle to shoot some sealant under the flange of the baffle. The needle bevel acts as a wedge allowing the needle to slip between the skin and the flange of the baffle. The rivets were replaced and the subsequent test was good. This could work for you if your next test is no good. This method beats making a big hole in the baffle, fixing the leak, and applying a patch to the hole. Good luck.
 
Me Too.

Dan,
I too had a leak in ONE RIVET of my left QB tank.
It was at the intersection of the first rib from the inboard end and the stringer on the bottom side.
Mine was just a weep and so slow that the fuel spread out 2" from the rivet and evaporated leaving a circle of blue fuel dye. Had me fooled for a while.
As the flange in the rib faces outboard and the holes in the ribs are two small to get your hand through I could not buck a new rivet.
I rang Vans but did not like Ken Scott's suggestion of removing the tank, cutting a hole in the back, bucking a new rivet and then recovering the hole I had cut. Sounded like I was likely to end up with a bigger leak trying to seal the hole I had cut for access.
So I thought I would try a simpler way first and if that failed resort to Ken?s suggestion.

I very carefully drill the head of the rivet and removed it. Then with a punch very carefully tapped the rivet up and as I suspected, found it trapped by the proseal- which I did not wish to disturb.
So I then used a syringe to squeeze a ridiculous amount proseal in the rivet hole to retain the drilled rivet tail and to seal the hole, followed by a blind rivet, also covered in a ridiculous amount of proseal.

It worked.

Not the way I like to do things but, the rivet tail is secure and I have the ?Optional Extra Deluxe Van?s Pickup tube?, so if it did get loose it is not getting into the fuel system.

Incase it did not occur to you, there are 144 sq inches in a sq Ft. so go easy on the pressure testing.I believe 1 (One) psi is all you should apply to the tank.

Pete.
 
Last edited:
Thanks Peter and Steve,

One of our local rocket drivers (and winner of an OSHKOSH craftsmanship award) suggested the prosealed rivet replacement idea to me, admitting while it's not perfect, it's quick and often successful.

The preseal injection with a needle seems like a more complete and less invasive solution, because as the seam closes the sealant speads out to fill the gaps.

If my first method (replace and seal the offending rivet) doesn't work I'll try the injection method. failing that, I'll try to get to the rivet line from the inside, enlarging baffle holes if need be.

This is an idea that should be saved to the "tech tips".

blue skies
 
closing the thread

The "sealed rivet" method solved the problem. The leaky rivet was replaced two nights ago according to my buddy's instructions. Turns out, in addition to the poor prosealing, the hole had been enlarged. Pre-squashing a slightly longer rivet slightly to fatten it up before installing it made for a better fit, along with a dab of proseal. Last night I put two pounds air pressure into the closed up tank, and successfully leak tested the repair. Then I installed the tank (with just five screws), attached the fuel and vent lines, and put in five gallons of gas. No leaks appeared during the next hour or so. Tonight we'll check again, after sitting for 24 hours with fuel in it.

Fortunately, the pressure also revealed that the AN vent fitting leaks. It would not have leaked much unless the tank was nearly full, cuz it's so high on the side. Since the tank is not fully installed, I can easily pull it off to seal the fitting. Checking the other tank as well is a must, but if that fitting leaks, I hope to fix it in place.
 
Be carefull pressure testing tanks. Two pounds is quite a bit. Normally pressure testing is done with 1 to 1 1/2 lbs.
 
Back
Top