Finally pressure tested my fuel tanks and after putting EZ Turn on the sending unit screws the tanks held pressure for 20-24 hours. Has anyone used a gasket (paper or otherwise) under the sending unit screws like in the plans or just ez turn or aviation permatex? FYI, for what it's worth I sealed my tanks with "Flamemaster" product that I bought from Van's as it is what they use and was less than half the price of Pro Seal from Aircraft Spruce. DO NOT TAKE this as a recommendation, use at your own risk if using a product like this to build your tanks. This is FYI only but worked well for me. I also mixed by weight very carefully...

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That's a nice milestone Tim.

Thanks Dan, I think I put it off because I didn't want to find a leak. I only gave in and tested when I realized if I got side-tracked any longer and had a leak I might have to buy more goop (sealant) because I would excede it's expiration date. I think I held my breadth as long as the test(s). I've been following your build since I joined this site, your an inspiration, you do some awesome work.


When I sealed the sending units on my tanks, I "think" I didn't have the fiber washers (can't remember where the reference was to them -  ? HomeBuiltHelp DVD or Builder's Guide?) - anyhow, I discussed it with Caleb and he said they didn't use them anymore and just seal the screw threads with EZ Turn, which I did and it worked fine.

I can't remember why - maybe I was dubious of the EZ Turn sealant and no washers - but on the other tank I got some screws from McMaster Carr that had a rubber washer bonded to the underside of the screw's head. I used those plus the EZ Turn on the threads.

Bottom line - no leaks on either side!

Thanks for your reply and your solution. I guess like you, I just had a nagging thought about the EZ Turn only even though it is some impressive stuff. I may look at McMaster Carr for the screws as you did. The thought of working through the access hole later doesn't sound like it would be fun if it can be prevented.

Jerry Bryan showed me the "inflated glove" trick to pressure test - sealing a glove over the filler neck and mildly pressurizing the tank and letting it sit. Being a "belt and suspenders" type guy, when I actually mounted the wings for the last time and had everything plumbed, I filled the tanks with avgas and just let it sit for a few days before riveting the top skin on - like you, I sure didn't want to have to try to re-do the seal through the access hole! I also used braided stainless teflon lines and I have never detected a leak nor ever even smelled a hint of fuel in cockpit, etc. (Hope God doesn't get me for that! LOL!)

I will confess to you, however, I'm so Type A that it really bugs me I sealed the senders differently on the tanks, BUT, at least I had the good sense to leave well-enough alone since neither was leaking! HA!

By the way, here's the description of the screws I got from McMaster Carr:

1 94709A113 1 Pack Neoprene-bonded 18-8 Ss Sealing Washer, No. 10 Screw Size, 3/8" Od
Thanks John,
You saved me a bit of searching. I couldn't agree more with what you said, unfortunately I am not ( I don't think) remotely type "A" so I tend to think, doubt, think, get confused and doubt and think some more.

I don't know if you are out of phase testing or not but give me a shout if you ever come down to Athens or Cleveland you have a good looking plane and I would love to see it if you come this way.

You're welcome and will-do!

Hey Tim

I have some Permatex #59214(available from NAPA) to seal the screw threads and also changed the screws to brass!  Works ok... just let it cure for 24 hours! There were only lock washers with the VDO ring mount... no paper washers!  I just made the hole in the tank 42mm dia and sealed the mounting ring to the inside of the tank with the Flamemaster sealant... works a hell of a lot better if you ever have to repace the sender.  My sender is a Stewart Warner - ISS unit from ACS,  Van's or Chief Aircraft, it's better quality then the VDO junk and the gauges are real 2-1/4" aircraft gauges... not automotive!  They are standard in all of Van's Aircraft!  the senders are much cheaper from Van's - $27 and are left or right! the float arm is detachable and you can buy extra is you screw them up bending...


Hi Ron,
Thanks for the info about the sending unit from Van's, I broke one arm trying to rebend to get full full and empty and need to replace. I also like the bonding the mounting ring, it would (will) make it easier if I ever need to remove/replace, I think I will do that. Why the brass screws though?

Hey Tim...

Keep in mind that you will have to use the matching ISS fuel gauges with those sending units!  I used the brass screws/washers because I did not like the steel screws that came with the sender... it would probably be better to use some copper if you can find!  I think tat i got the screws from home depot!


That's what I'm using for my tanks... still the same formulation as Pro Seal but at a great price!  Here is a paper on a few of the sealtants available...


Thanks Ron,

I am really pleased with the results I had and you're right, the price was right.


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