Fuel tank

[Kmdpilot]

Ok, I dont think I have posted a rookie question in a bit, so here goes. I read a lot about how everyone seems to hate tank sealing. Looks super messy and a PITA. So, why don't they use a liner or custom molded plastic tank?

 

[PhatRV]

The Proseal is messy but it is not as bad as people made it out to be, as with most topics on the forum. Buy a lot of nitrile gloves, MEK, acetone, and plastic liners for your work bench. My biggest worry was will it leak.

Anecdotal: recently a RV8A tank was re-Proseal but it reverted to mush after 3 years. Some people cured a proseal tank in a heated bathroom for over 24 hours to ensure it is fully cured. One builder applied Proseal really thick and his tanks are still leak free while another QB tank had rivet hole leaks after 2 years. Also, a fully cured proseal will look gray after a year or two. The proseal that was reverted to mush was mostly black.

 

[wirejock]

Proseal

The Proseal is messy but it is not as bad as people made it out to be, as with most topics on the forum. Buy a lot of nitrile gloves, MEK, acetone, and plastic liners for your work bench. My biggest worry was will it leak.
<snip>

I agree.
I don't get it either. I enjoyed the tanks.

 

[Desert Rat]

Back in the day, They did just that. Lots of airplanes had separate metal gas tanks or rubber bladder style tanks thad just dropped into a hole in the top of the wing.

Fast forward to today and the simplest way to utilize all the available space without adding a bunch of weight is to just build the wing a little more robust where you want it to carry fuel then get out the pro seal gun, seal up the inside of the wing and then stick a gas cap on top.

Yeah, RV tanks are removable, but in a practical sense, it's just another part of the wing, not a huge gaping hole in the wing that has to be designed around. You can still have ribs inside it, don't need the weight or complexity of close out panels on top or whatever.

But yeah, pro seal isn't very fun to work with.

 

[Mikeyb]

It’s a legitimate question. VAF polls have shown that roughly half of respondents had tank leaks at some point or another. I developed leaks after a few hours and a few G’s in tanks that were well sealed initially.

 

[PhatRV]

Back in the day, They did just that. Lots of airplanes had separate metal gas tanks or rubber bladder style tanks thad just dropped into a hole in the top of the wing.

Where I was working, they installed a complicated shape fuel bladder inside the F18 mid-fuselage. It was interesting to see one installed, from a tight bundle that could squeeze inside an access opening and it filled a large space after all the restraint straps were removed.

Fast forward to today and the simplest way to utilize all the available space without adding a bunch of weight is to just build the wing a little more robust where you want it to carry fuel then get out the pro seal gun, seal up the inside of the wing and then stick a gas cap on top.

I think all the transport aircraft wings use this concept. They seal up the rib/wingskin interfaces with sealants. They use the special rivets where the sealants was preapplied and this is done to save labor cost. Without the preapplied sealant, they have to coat each rivet head with a glob of sealant. Very similar to our RV tanks but in a much much bigger scale.

 

[Ralph Inkster]

Ok, I dont think I have posted a rookie question in a bit, so here goes. I read a lot about how everyone seems to hate tank sealing. Looks super messy and a PITA. So, why don't they use a liner or custom molded plastic tank?

Generally speaking, RV builders are attracted to sheet metal construction because it is clean, dry work overall. So when it comes to dealing with gooey smelly work like fiberglass or tank sealing work - much belly aching results.