Tip: Proseal ...The fact and the fiction

[LettersFromFlyoverCountry]

A big glob of Prosealover the shop head...a generous filet along one side of the rib, and then along the flange/skin on the other... can't leak. Buy extra proseal.

[pvalovich]

-8A QB N192NM so I haven't had the fun assembling the tanks. However, it is time to install the float-type fuel senders.

I've got a tube of "stuff" from Vans that's supposed to work - if I can really figure out the mixing instructions. Some really basic questions:

1. Urban legand sez to toss the cork gaskets. Is that correct?
2. Bead size - what's appropriate? While subscribing to the "More is better" idea, what happens if the excess oozes from the cover plate into the tank and possibly breaks loose sometime in the future?
3. Rubber gaskets - just in case the **** thing doesn't work and I have to remove the sender, I intend to use the provided rubber gaskets without sealer, but put pleny of sealer on the screws before assembly. Good idea?
4. Shelf life - or more accurately - "After mixing useful life". How long do I have after mixing for useful application capability?

[RVjim]

Hi Rick,

I just found your thread. Nice write up.

I did my RV-3 wing tanks Van's way 20+ years ago. Messy, but lasts a long time.
A friend of mine is also on the C-17 program.
I did my RV-4 wing tanks the same way you discribe. Much cleaner, and easier to inspect for possble leak paths.
In addition to placing a cleco in every rivet hole, I included a #6 nut against the inside of the wing rib to increase the cleco spring compression and distribute the cleco force around the dimple.
I usually waited a week (48 hours minimum) before I riveted the tanks.
I didn't clean the clecos or nuts. Just removed them. (You'd normally have to pay someone to provide these custom non-scratch clecos.)

I installed the rivets dry. Very easy this way.
Any potential for problems with the dry rivet installation? I understand the the shop head is self sealing.

I sealed around each rivet inside the tank, and formed a overlapping bead over the rib and onto tank skin by about 3/16" all around.

I also sealed the fuel line fitting and nut, instead of Van's safety wire method. 1/4" overlap on each part and .15 minimum thckness is supposed to meet the same standards on fuel fittings as safety wiring them.

Any comments, or suggestions?

Regards,
Jim Ayers

[Rick6a]

Originally Posted by RVjim

.....I installed the rivets dry. Very easy this way.
Any potential for problems with the dry rivet installation? I understand the the shop head is self sealing.....

Jim,

No doubt it is easier to install the rivets dry but many, many field reports of weeping rivets and blistering paint suggest to me that the shops heads of the rivets are not necessarily self sealing when bucked into a thin dimpled stackup. In addition to any given builder's level of workmanship, there are other variables that determine overall quality such as rivet length...the callout is 3.5 and I prefer a 4....hole preparation...usually reamed with a #40 and I prefer a #41 to produce a slightly snugger fit...the quality of the shop head after bucking...some people leave bad rivets in place reasoning that they will cause more damage by replacing than leaving alone.....All the more reason to dab a touch of sealer around the countersink prior to seating the manufactured head, and then fully encapsulate the shop head after setting the rivet. Extra work...sure...but I'd rather pay now than pay later.

[Greg Arehart]

I second the queries of pvalovich, as I am in the same position about to install/seal the float senders and would like to know what works and what is less likely to work

[RVjim]

Originally Posted by Rick6a

Jim,

No doubt it is easier to install the rivets dry but many, many field reports of weeping rivets and blistering paint suggest to me that the shops heads of the rivets are not necessarily self sealing when bucked into a thin dimpled stackup. In addition to any given builder's level of workmanship, there are other variables that determine overall quality such as rivet length...the callout is 3.5 and I prefer a 4....hole preparation...usually reamed with a #40 and I prefer a #41 to produce a slightly snugger fit...the quality of the shop head after bucking...some people leave bad rivets in place reasoning that they will cause more damage by replacing than leaving alone.....All the more reason to dab a touch of sealer around the countersink prior to seating the manufactured head, and then fully encapsulate the shop head after setting the rivet. Extra work...sure...but I'd rather pay now than pay later.

I installed the rivets dry so the rivet head wouldn't float up on wet seal.
C-17 program. NEVER shoot wet seal. ?

I didn't see the need to dimple extra deep to allow room for the floating rivet head. Seems contrary to rivet structure considerations.

I shot my RV-3 wing tanks per Van's instructions for shooting wet seal. I still got one rivet that blistered the paint around the rivet head. It seems like there are no guarantees with that method, either.

Jim

[longranger]

I started out back riveting tank stiffeners (wet) but most were being left slightly proud on the outside. Thinking the workbench may be giving somewhat, I moved the backrivet plate from the bench to the concrete floor and got slight improvement, but still not as flush as I'd like to see. I got even better results with the mushroom set and bucking bar with the skin in the cradle. I did notice that after 3 or 4 rivets they started sticking up again. That's when I started wiping the set after each rivet and had no more problems. (I assume the layer of sealant holds the set off the skin slightly?) Slower this way, but the results are worth it.

BTW, I seemed to be able to better control the right end of this bucking bar while shooting solo than I did with my new titanium bar, resulting in fewer clinched shop heads.

[WSBuilder]

Rick,
I'll start sealing this weekend and plan to use your suggested 100% cleco process and post-semi-cured rivets. Two questions: is it easier to just do the ribs that way but not the stiffeners, and 2) would it be a good idea to thin the pro-seal a little for wet installing the rivets?

[Rick6a]

Originally Posted by WSBuilder

Rick,
I'll start sealing this weekend and plan to use your suggested 100% cleco process and post-semi-cured rivets. Two questions: is it easier to just do the ribs that way but not the stiffeners, and 2) would it be a good idea to thin the pro-seal a little for wet installing the rivets?

Bill,

You can do the stiffeners that way but their installation counts among the easiest jobs in fuel tank construction and I just install them wet. The ribs are another story. As the photo shows, I prepped all the internal ribs in both tanks at the same time and shot the rivets over the next few days. I have no experience with thinning proseal so I won't go there.

[TGRV7]

Use the method Rick has shown.
I did and had no leaks.


Thx Rick