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Fuel Tank Question

So How Did the Fay-Sealing Work

I am starting to assemble my tanks. I would like to know how the Fay-seal process worked out?
Tom Roberts
 
On my 7A I built my fuel tanks both ways. Built the first one by the plans, the second one using faye sealing. I HIGHLY recommend going with faye sealing! Much less messy, easier, and the results are fantastic. You can check my wing build section on my website for more info and lots of pictures. I'm sure it's similar to what the RV-14 will be.
 
Tested my first tank yesterday (I used the cleco over night method) and so far only the fuel cap leaked. I tightened it and after four hrs the manometer only increased by a 1/4 inch. I was applying soapy water and I think it cooled the tank. After drying off the level raised.
I'll probably regret this post as I'm about to go back out to the hangar and do a check.
 
I am fay sealing everything on the tanks. I figure if you can fay seal the ribs, then why not the rest of the parts. The bigger reason is that I got all the tank stiffeners in place on one tank and ran out of proseal. I figured that I would just bring all the parts in the house to cure, then I will wet rivet later.
 
Fay sealing the read baffle

I have been reading up on the process to build the fuel tanks.

Are any people following the "fay sealing" process versus the plans? I assume that the plans are not the same. Essentially put all the proseal in place with cleacos, allow the glue to setup for a while up to a several days, the wet set the rivets.

http://www.vansairforce.com/community/showthread.php?t=7602&highlight=proseal+channel


Ken

I just finished both my tanks using the fay sealing, wet rivet method and they both passed air test with no leaks. I went even one step farther than some others and fay-sealed the rear baffle. I'd read about too many rear baffle leaks and decided to go overboard. I "buttered" the contact areas of both the baffle and the skins with a thin brushed-on coat of sealant, and then also added the "bead just forward of the rivet holes" called for in the plans.

The plans warn about "pillowing" if you get too much sealant between the baffle and the skin, so I used my seaming pliers to squeeze out the excess while still in clecos.

As final insurance that my generous use of sealant didn't present any fit-up problems later, I temporarily installed each tank after riveting while still wet.

I'm very happy with the results. No leaks, tanks that bolt-up with no interference. Probably added a few OZ of weight that I didn't need to, but it seemed like a good trade-off.

I'll paste in a couple of pictures since I don't have a builder's web site.







 
+1 Rick's method..

..and I did 4 tanks, all of which are supposedly leak free. However, I'm not flying yet. Seemed to work real well if you time it right (i.e. DON'T let the proseal completely cure before riveting.)
 
I'm certainly no expert but I question using the seaming pliers to squeeze out proseal. You would not want the skins to pillow back out to where they were before the seaming pliers as you could have a leak. I would allow the clecoes to squeeze what they can and then rivet, but that's just my opinion.
 
I am starting to assemble my tanks. I would like to know how the Fay-seal process worked out?

Ummm........

I know I'm aiming upwind, but hey, let's review the correct terms.

All methods with any chance of long-term success (including Rick's "cleco until partial cure") approach, incorporate a fay seal, a fastener seal, and a fillet seal.

A fay seal is the film trapped between the parts. It is only .001" ~ .003" thick in the vicinity of fasteners, and thicker where parts don't quite pull together.

A fastener seal is about the same thickness. It is sealant not squeezed out around the rivet when the coated rivet is set.

A fillet seal is the smooth band of sealant applied after the rivets are set, covering all the shop heads, and the edges of the previously fay-sealed rib to skin junctions. It is 50 to 100 times thicker than fay and fastener seals, and as such, the only seal capable of surviving even the most tiny relative motion between the components.
 
I had good luck with the Fay method on my 14 tanks. I have tested them with auto gas, overnight at all angles. Only the cap leaks (and I've adjusted them)
 
Not sure about the thicknesses you came up with but here is what I did.

1. Used a Semco gun to lay down beads of sealant on the part and the skin.
2. used a spatula to smooth out and make a continuous layer on both parts. Probably too much sealant.
3. cleocoed in place, which caused a lot of sealant to ooze out.
4. used a spatula to make a fillet on the one side and the seam (like in a shower on the other side of the stiffener.
5. I then used q-tips saturated with acetone to get off excess where it dripped onto skins.

I have attached some pictures for people to make comments on my technique.





I did the initial sealant on Sat and Sun. I have the parts in the basement curing. I will rivet sometime this week.

cheers

ken
 
Rivet callouts

The callouts for the fuel cap are wrong. The flange varies in thickness. The plans call for the same rivet in all holes. The thick part of the flange needs a longer rivet.
Is anything nastier than Proseal?
 
I'm certainly no expert but I question using the seaming pliers to squeeze out proseal. You would not want the skins to pillow back out to where they were before the seaming pliers as you could have a leak. I would allow the clecoes to squeeze what they can and then rivet, but that's just my opinion.

Ron- Roger your concern, but my thinking was that Van's instructions suggest that clecoes alone don't provide enough force and suggest squeezing between the clecoes with C-clamps. I felt the seaming pliers were a better option because they spread out the force more evenly than clamps. In my case a fair quantity of proseal oozed out when I squeezed and I saw no tenancy of the metal to move once squeezed.

The tanks passed air test (soap test plus several days holding a pound of pressure with no leak-down) and they fit perfectly on the spars. In the end, I'm just providing one man's experience.
 
The callouts for the fuel cap are wrong. The flange varies in thickness. The plans call for the same rivet in all holes. The thick part of the flange needs a longer rivet.
Is anything nastier than Proseal?

Probably a leftover from the standard Vans cap days. The flanges for the "standard" caps were formed, and were constant thickness. Flanges for the Newton caps have a machined surface to mate with the curvature of the tank skin, so they're thicker in the middle than on the front and rear. I also found this out the hard way...
 
Ivan, if they passed the test they should be fine. My view on the clamps Van's recommend would be that they stay in place until the sealant sets up some. Just passing my view not a recommendation.
 
The callouts for the fuel cap are wrong. The flange varies in thickness. The plans call for the same rivet in all holes. The thick part of the flange needs a longer rivet.
Is anything nastier than Proseal?

My plans show different rivets for the thicker part of the flange. It's a little tricky cause some are diamonds and some are squares on the drawing. It looks like squares rotated around the circle.

2zrkguo.jpg
 
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and the one square at the top is where T-0005B goes, so it does need a longer rivet and does make it look like the squares are just rotating around the circle.
 
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