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Fuel tank repair kit - which saw for hole

.063 is a little overkill in my opinion. IIRC I think I used .040. And I think even .032 would work fine. I did mine several years before Van's offered a "repair kit". The use of closed end rivets is not required. You're using pro-seal to seal everything anyway.

Agreed, I would've probably used .040 unless someone had advised to use thicker for the covers. Also, Vans kit has 25 rivets per cover, which seems like a lot compared to the 12 screws in the access plate on the root rib.
If the covers ever need to be removed again in future then the closed end rivets will be difficult to drill out because the mandrel can't be knocked out, so that's another argument to use normal pulled rivets sealed by Proseal over the heads.
 
I just assumed the vans covers were 1/16” and mimicked what I thought they were. Used the sealed rivets. They were inexpensive and easy to procure. Also had the opportunity to remove one of these covers. The rivets are easy to remove on the inside with side cutting pliers. I thought the general consensus was tank sealer worked best on the inside of tanks.
 

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Maybe someone who has purchased the access covers from Vans will be able to 100% confirm the thickness?

In a couple of posts above, #32 and #35 above I think, there is a recommendation to put sealant on the outside of the rivet heads, though if they are closed end and have been installed wet then that seems redundant. The Vans repair kit includes the rivets for $0.10 each so it's not much assuming the repair is successful.

There doesn't unfortunately appear to be an instruction sheet listed in the bill of materials for the Vans repair kit.
 
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Maybe someone who has purchased the access covers from Vans will be able to 100% confirm the thickness?

In a couple of posts above, #32 and #35 above I think, there is a recommendation to put sealant on the outside of the rivet heads, though if they are closed end and have been installed wet then that seems redundant. The Vans repair kit includes the rivets for $0.10 each so it's not much assuming the repair is successful.

There doesn't unfortunately appear to be an instruction sheet listed in the bill of materials for the Vans repair kit.

Just measured the T-412’s I bought for the ER tank build. 0.0425”. Fortunately, didn’t need any of them.
 
Getting ready to do this but may go for square or rectangular holes for improved access (I need to clean off and reseal everything inside because the original sealant has turned to goo).

Question: can anyone please confirm how thick is the aluminum for the Vans-supplied T-412 cover plates?

Please don't do square or rectangular. Take a look at AC43.13-b for guidance (chapter 4-50). You will need lots of rivets and rounded corners for something more square. Using Van's repair kits is akin to following guidance from the manufacturer, so you should be able to trust that the repairs are structurally adequate.

The plates should be the same thickness as the underlying material.
 
Thanks for confirming the thickness of the Vans T-412 cover plates. The rear baffle on the tank is .032 so they have made the plates one gauge thicker. The AD42H rivet spec states a minimum material thickness of .063 therefore a cover plate thickness of .032 would also work.

Re. square access covers, there was a post on VAF by someone who made square cutouts with rounded corners using a step drill. I also looked at AC43-13 and the implication of following the guidance is a double row of rivets in the patch, whether round or square. I think I'll probably just order the round covers from Vans, along with the Proseal, and get on with the cleaning task while waiting for the shipment.
 
Any externally used pro-seal (the fillet around the patch and the material ontop of the rivet heads) should be tob-coated with CS 3600. Pro-seal will turn to gooe after repeated exposure to fuel vapor. It will not happen inside the tank, but will most assuredly happen to the exterior material.
Take the extra time to top-coat it and you will tank me in 5 years.
 
Any externally used pro-seal (the fillet around the patch and the material ontop of the rivet heads) should be tob-coated with CS 3600. Pro-seal will turn to gooe after repeated exposure to fuel vapor. It will not happen inside the tank, but will most assuredly happen to the exterior material.
Take the extra time to top-coat it and you will tank me in 5 years.

Do you have any further info or background on why the Proseal turns to goo if it is exposed to fuel vapor?

I (unfortunately) know that it can happen but it is totally bizarre that a product intended for sealing fuel tanks may dissolve if it is exposed to fuel vapor!
 
To prevent the hole saw from wandering, I used a 1/2” thick piece of star board (heavy plastic) cut to fit in the the square and drilled it with the holesaw. Lots of grease to collect shavings and it worked out fine.

A note: even after using grease, cleaning up thoroughly and flushing 15 gallons through the tank with the sump drain out, I still got a couple of shavings in the sump Oring months after.
 
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