Comment

Comment by Larry Zepp on July 8, 2013 at 9:51pm

Hi John,  Thanks - I did check for a good ground connection before and after adding the sealant - AOK.

Hi Gerald, I used the #8 pressure sealing washers because they have a tight fit on the thread of the screws. For four of the screws the primary seal is between the head of the screw and the raised boss around the hole on the sender. But for the fifth screw that has the ring terminal, having a good seal on the thread is more important - even if it is augmented by the sealant. For the ground screw I used the following sequence: screw head, ring terminal, flat washer, pressure sealing washer and then the sender body. The molded rubber seal on the inside of the McMaster Carr seal washers was a tight enough fit that I threaded the screw through the rubber so I wouldn't tear it up.

For sealant, I used the  AC-240-2 sealant from AC Spruce. This came in a small caulk tube, but I only needed a small amount for the two senders. I borrowed a digital scale from work that would read grams. Mix ratio is 10 parts resin to 1 part hardener by weight. 10 grams resin and 1 gm. hardener was enough to seal both senders, screws and both sides of the gasket. I hand mixed this for about 10 min. When mixed it has a 2 hr. working time at 70 deg. F.

 

I made a small spatula to fit into a small Xacto knife handle using thin stainless or aluminum. With all 5 screws started into the clamp ring, you need a small tool to get in there to apply sealant. The spatula worked fine for this. I applied a thin coating or the polysulfide rubber sealant to: underside of screw head, both sides of pressure seal washers, and both sides of the rubber seal. For the ground ring terminal, I applied thin sealant to all surfaces and it squeezed out fine and made a good low resistance ground when I tightened the screw.

 

Another note - I figured that the fuel tanks would have a lot of condensation due to air vs fuel temp differences - and potential corrosion. I used two light coats of etch primer (in spray cans) to prime the tank and the inside of the nose skin in the tank area.

Happy Building, Larry Zepp  

Comment by John Austin on July 8, 2013 at 10:04am

Larry, if you haven't already done so, be sure and test your ground pigtail on the sender to make sure the sealing washers and sealant haven't insulated the screw from good contact with the sender.

Looks great!

John

Comment by Gerald Zuhlke on July 8, 2013 at 1:18am

Larry, I too am at the point of mounting the fuel senders.  There have been many helpful comments.  I really like your idea of using the pressure sealing washers.  I now plan to use them also.  From one of your previous posts you mentioned that you used the #8 washer size.  The screws are size #10 but I'm assuming you used the #8's to get a little more compression to seal the screw?  Also, did you put the sealant on the both the sender gasket and the washers as well?  Thanks for the comments and photo!