BAD tank leak

mg1003 · #1 02-28-2009, 08:56 PM

Today I put the access hole cover on my right tank (RV7a slow build) and could not resist trying a leak test (Van's leak test kit). Oh boy does this tank leak.

The inboard upper corner were baffle, skin, and ribs meet leaks audibly. My balloon deflates in seconds.
Looking to see if there is more bad news, I sprayed soapy water on the baffle to skin joint and the outboard ribs.
The baffle leaks in about 6 (or so) places (large bubbles) along the lower joint. The upper joint has large bubbles near the outboard end. Many rivets in the upper joint show small bubbles. Spraying the Z-Brackets, I found one place with tiny bubbles.

These joints were sealed and riveted one week ago and it has been cool (probably 50 to 65 in my garage) here in CA. All baffle rivets were squeezed to exactly the right shop head size but it appears that there is a good .01" gap between the skin and the baffle (from which soapy water comes squishing now).

Admittedly I used ProSeal quite sparingly when riveting the stiffeners and ribs (and I have not checked them for leaks yet), but when it came to the baffle, I put a solid 1/8" bead just ahead of the rivet hole line (onto the skin) and placed gobs of glue in every corner. When inspected from the inside (as far as I could see), there was a nice bead squishing out of the corner everywhere.

To be frank, I feel dismayed about this problem. What options do I have? What did I do wrong (I am in the process of building the second tank)?
I just googled "sloshing sealant" and found that they exist and a bunch of safety advice about how they have brought down planes. There seems no mention of these on this forum. Is there experience with these (or opinions)?
Should I first of all pull the acess hole cover back off (it is easy to clean now)? Should I try to squeeze the baffle rivets harder?
There seems to be no point trying to address the leaks one by one? There seem to be too many and they seem too big.
Shall I put the tank in a corner for two or three weeks to give the sealant more time to cure? Or did I ruin that chance with this leak test ...

mcencula · #2 02-28-2009, 10:04 PM

If it was my tank that had that number of leaks, I believe I'd drill out the rivets, remove the baffle, clean it all up and try sealing / reinstalling the baffle.

I'm sure that's not what you'd like to hear, but it'll only take a few hours to get through it.

Good luck.

sglynn · #3 02-28-2009, 10:35 PM

I agree, I'd remove the baffle and reseal every seam, every rivet and then redo the baffle with lots for proseal and the z-brackets with plenty of proseal. Or you could cut some access holes in the baffle to allow you to spread around proseal. My tanks had no leaks. I just finished them a couple months ago. I used a lot of proseal. Don't forget to score the interfacing surfaces with sandpaper and to thoroughly clean surfaces with MEK so the proseal sticks. My reading on slosh is that it is a no-no. It comes apart and plugs the fuel lines. Good luck.

videobobk · #4 03-01-2009, 05:29 AM

While you have the rear wall of the tank off, rivet four small (3/4" square) pieces into the inboard and outboard upper and lower corners. There seems to me to be too large a gap in those places where the inboard and outboard ribs meet the skin/back. These are not truly square and must be cut to fit, but the gap will be much smaller. Sorry I don't have pictures.

Bob Kelly

Ron B. · #5 03-01-2009, 05:54 AM

I would seek help from some knowledgeable person for the second tank. As for the first tank I would think it will be harder to reseal than with a first try. A clean slate would be better. If you take it apart them find help.
Ron ( no expert)

8CW · #6 03-01-2009, 06:05 AM

Quote:

Originally Posted by videobobk

While you have the rear wall of the tank off, rivet four small (3/4" square) pieces into the inboard and outboard upper and lower corners. There seems to me to be too large a gap in those places where the inboard and outboard ribs meet the skin/back. These are not truly square and must be cut to fit, but the gap will be much smaller. Sorry I don't have pictures.

Bob Kelly

I finished up my tanks about a year and a half ago with no leaks, but I didn't scrimp on the proseal either... I didn't think to do what Bob has suggested, but it seems like a good idea and I'd probably do it next time.

Steve Barnes · #7 03-01-2009, 08:18 PM

I'll throw an unpopular idea in to the mix. A friend of mine put in a large access hole for each bay on the rear baffel, (same as the one for fuel pickup and fuel float) so just in case he had a leak any place in any bay he could easily fix it. As luck would have it, I don't think he ever had a leak, so he never got a chance to use his access holes.

As far as fixing your leaks, I would highly recommend, pulling rear baffels, throughly cleaning and scuffing. Carefully add more seal to the back of all rib flanges, all corners, and don't be to skimpy with the tank sealant. If you are nervous about more leaks, think about more access holes.
Something else to think about;
A very experienced builder that I know, put LP-4-3 rivets on his rear baffels. He discovered his mistake when he pressure tested his tanks.

Steve Barnes the Builders Coach

Mel · #8 03-01-2009, 08:38 PM

if your baffle to skin has a .010" gap, it sounds like maybe the skins were dimpled and nothing was done to the baffle to accept the dimple.

mg1003 · #9 03-01-2009, 10:11 PM

Thanks for the feedback!!

I will first try to save the situation by applying seal from the outside, but I put little hope in this approach.
If this does not work, the baffle will come back off, clean-up, etc ...

I will think about the idea to put openings in the baffle. It sounds like bringing an umbrella to make sure it will not rain.

As suggested by Vans the skins are countersunk (not dimpled) on the skin to baffle joint and only deburring was performed on the baffle.