Tip: Proseal ...The fact and the fiction

[TShort]

I guess I see the potential path...
The way I did mine, I "buttered up" the rib with a good layer of proseal on all surfaces where there is a rivet hole. I then placed the rib carefully into position, and when clecoed / riveted in place the proseal squeezed out and made a nice fillet all the way around the rib and all the rivet holes. I did not put any proseal on the tabs at the very end where there are no rivet holes; the area you marked as "potential path" has plenty of proseal, however.

I'm 1/2 way done with the interior ribs, doing all the shooting and bucking solo, and this is not nearly as bad as I had anticipated.

Thanks for the tips!

Thomas

[RV8SQDN]

RV-6A,

One rivet weeping. Not bad. Are you planning on a fix for that? And if so, what is your plan? Because I am not sure if I would have one in your place. Getting something under the rivet head is going to be very difficult. And going in through another way is not very appealing either.

[Rick6a]

Originally Posted by RV8SQDN

RV-6A,

One rivet weeping......Are you planning on a fix for that? And if so, what is your plan?...... Getting something under the rivet head is going to be very difficult.........

There are a few options to try in my particular circumstance without tearing into the tank.
#1. Do not fill the tank above 15-16 gallons. I know this works but the single weeper only yields a very small amount of blue dye over a period of several days. It really is no big deal to wipe the dye away. In practice, I routinely top off the tank anyway.
#2. Apply Loctite Threadlocker Green (901?) to the rivet head which I am told sometimes works due to its superior wicking powers. I may try that sometime, if I ever get the tank really dry.
#3 Apply a vacuum to the tank to "suck" proseal in from the outside. Apparently this has been done successfully many times.
#4. At AirVenture this year, I was amazed to spot an RV-6A with a blind rivet protruding from the exact same hole location as my weeper. What do you suppose the odds of that are? You can bet it was installed to deal with a weeper. This is a very common fix. Still, a protruding rivet just isn't my thing.
Builders sometimes cut access holes into the rear baffle to deal with bad leaks or in the case of older RV's....peeling slosh. I really don't see removing
the tank and going through all that just to address one single rivet.

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A day or so after I wrote those comments, using eyeball effort alone I mixed what I guessed to be an approximate 10-1 by weight dollop of sealer from what is left in a can of oh-so-long expired proseal purchased from Van in 2000. I applied a dab of it over the head of that weeping rivet and worked a popsicle stick back and forth over the area in an effort to shove some of the sealer underneath the less than perfectly seated rivet head. When in my imaginings I was reasonably sure I did as much as possible under the circumstances, I left the sealer glob to cure in place over the rivet and continued to fly the plane several times over the next few days. Later, I cleaned off the excess sealer from around the area and noticed a distinct halo of proseal remains around the perimeter of the noted weeper. The minimalist effort seems to have worked because since that time with the fuel tank constantly filled to the max, no traces of tell-tale dye have yet emerged from under that rivet. I?d rather be lucky than smart. As a back-up plan, I did manage to locate and purchase some very hard to find -1 grip length flush head Cherry rivets (CR9162-4-1) from Bon-Aero. At this point, my gut tells me it will not be necessary to eventually replace that rivet but as in all things, time will ultimately tell.

[b17fe]

Rick,
Your method worked brilliantly. Wish I had known this on the 1st tank.
Much easier to deal with ... less mess and increased visual inspection of rivets.
A counter sink bit was all I needed to clean the dimple of sealant after cleco
removal.
One thing I did learn was not to discard the little nubs (from the inside
of the tank, after cleco removal) onto the floor... Use the garbage can!!
Steve 81604

[Naruto]

This procedure seems pretty good. The only question I have is if you let the proseal partially dry with the cleco's installed and then when you go to rivet everything together later. Is there any chances for the skins to get a wave in them between the rivet because the dried proseal may prevent the space between rivets from compressing. Do the skin come out smooth down the rivet line on each rib by letting the proseal dry before riveting?

I can see when riveting the rib to the skin with wet proseal, the proseal will squeeze out and make a tight fit between the rib and skin. Is my thinking faulty?

[az_gila]

Originally Posted by Rick6a

....... As a back-up plan, I did manage to locate and purchase some very hard to find -1 grip length flush head Cherry rivets (CR9162-4-1) from Bon-Aero. At this point, my gut tells me it will not be necessary to eventually replace that rivet but as in all things, time will ultimately tell.

Rick,
For this application, wouldn't the oversize CherryMax CR3242 - which are easily available in the -4-1 size - be a better choice?

The existing hole, which I presume is double dimpled, will not have very parallel sides, which is of little effect to a standard driven rivet, but is not the best hole for pulled rivets, which prefer nice straight sides....

It seems to me that drilling the hole out 1/64 and using a OS CherryMax rivet would give a better joint and also probably better sealing... with no effect on the fit into the existing dimple.

...just a question... gil A

[Rick6a]

Originally Posted by Naruto

......if you let the proseal partially dry...... Do the skin come out smooth down the rivet line on each rib by letting the proseal dry before riveting.....

You are not really allowing the sealer to cure up hard, merely some degree of tack dryness and in my experience, no discernable waviness has ever been encountered.

Originally Posted by az_gila

....The existing hole, which I presume is double dimpled...

Gil,

IF the hole were double dimpled (which it is not) the CR3242 would be a better choice. In this case however, the hole is of the standard DWG dimension complete with nice straight sides.

[Naruto]

I shared this procedure with a friend of mine who is a A&P and he also sees nothing wrong with this way to seal the tanks, even though they (Duncan) rivet with the proseal wet. One thing he recommended was to spread proseal completely over the shop heads of the ribs flange instead of just wetting the rivet's shop head themselves with a q tip on the inside of the tank. He said a complete layer of proseal will lessen any chances of a individual rivet leaking later.

He was the one who questions the potential waviness between the rivets.

[8CW]

Those of you who used the pre-filled tubes method, how many does it take to do everything on both tanks?

[WSBuilder]

Thinking about the weeping rivets...we're told to Scotchbrite the fay surfaces between ribs/stiffeners and skin before sealing, but what about the fay between the rivet and outside skin dimple surface? Seems like the dimpling process is not a good adhesion-promoting prep. Could that be a reason for poor sealing and should we be addressing those?