Access port cover plate

[s/v Jedi]

Originally Posted by malyea

Thanks to all for the good info!

No intent to pit “idea A” against “idea B” per se, but I’m left with deciding the merits/pros/cons of “how to attach the cover plate” to the fiberglass tank...

A - tap threads directly into fiberglass, or
B - glue screws with 5200 pointing up from inside to outside, or
C - drill and insert threaded metal inserts into the fiberglass tank top

Final/additional thoughts?

Thanks

Yes, for tapping into the fiberglass, wall thickness should be 1.5x fastener diameter for optimum strength. Epoxy a ring of G10 on top of the tank opening to increase thickness if needed 👍

[jharding]

Jedi has got the answer, could use g10 or I use a lot of GPO3 from mcmaster carr for 1/2 the price. no reason to use metal, easy job with epoxy. I would use a Fein tool to cut hole, best tool I have ever bought.

[sailah]

Personally I'd cut the hole with a hole saw. I did this on my aluminum tank and was doing it to install a pickup for my fuel polisher. Which was convenient since the hole saw dropped a bunch of shavings into tank even after I tried hard to vacuum as I was doing it. No matter, polisher sucked them all up.

Anyways that gets your hole in there. Then I'd make up an aluminum disc from 1/4" aluminum plate with holes spaced around. You can also buy pretty good discs like this directly on ebay but I made my own since I have a lathe.

Then I'd make a ring, same diameter as disc, with same holes but tapped for machine screws like 10-32 etc. Drill your bolt holes in the tank using disc as guide. As mentioned then pop rivet the back up 1/2 ring in place by holding it with the machine screws. The backup ring would go on inside of tank. Then do the other half. Then cut a gasket or buy one from McMaster. Put it all together.

I like aluminum because 1/4" you can tap directly for pipe fittings.

[JeffOnTheBoat]

I just discovered an alternative to the seabuilt option. The only issue is they only have a 4 inch hole version. Is 4 inches large enough to get my arm in to scrub the tank very easily? They said they may add a 6 inch one someday, but don't know when. The price is right at $39 each.
https://www.fueltankparts.com/6-od-b...ess-plate.html

[Boston Blackie]

Atlantic Gasket sells buna N closed cell foam fuel tank gasket sheet in varying thicknesses and durometers. I found it much more reliable for sealing the ports in our aluminum diesel tanks without distorting the aluminum plate.

Also used (http://www.farnell.com/datasheets/676882.pdf) buna N self sealing machine screws to attach the cover plates without need for washers.

[model 10]

If you choose to only glue on the cover plate, wax the tank surface first. It's common practice to wax fuel access panels on the bottom of aircraft wings and then glue the cover on. Waxing the screws helps too. They pop right off when you need to get in. And no, they don't leak!