Online Community of Zenith Builders and Flyers
That's a nice milestone Tim.
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!
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|
You're welcome and will-do!
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...
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... http://www.vansairforce.net/articles/tank_sealant.pdf