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Author Topic: Fuel Resistant Sealants  (Read 1708 times)

Offline Steve Dwyer

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Fuel Resistant Sealants
« on: May 06, 2021, 06:00:48 AM »
I'd like to seal the openings around the copper tubing where the tank fittings come through the bulkhead behind the motor on my recent Jameson build.

Any thoughts? Any experience with Permatex Permashield?

Steve

Offline Dan McEntee

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Re: Fuel Resistant Sealants
« Reply #1 on: May 06, 2021, 08:07:50 AM »
If installed during the construction phase, thinned epoxy would be all that you would need. It can be sanded smooth and what ever finish put over that. If added after the fuselage is finished, careful application of thin CA glue would fill any seam, and then a thin dab of clear silicone around the tube. If that wears off, it can be replaced easily.
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Offline Trostle

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Re: Fuel Resistant Sealants
« Reply #2 on: May 06, 2021, 12:44:56 PM »
Epoxy and micro balloons.

Why use micro balloons which can absorb oil?  The micro balloons still have to be sealed.

Keith

Offline Steve Dwyer

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Re: Fuel Resistant Sealants
« Reply #3 on: May 06, 2021, 02:24:53 PM »
The plane is finished (just painted) and now I want to install the removable tank. I read that silicone is not resistive to fuels, anyone have experience using Permatex it is supposed to remain flexible and resists gasoline??

Steve

Offline Steve Dwyer

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Re: Fuel Resistant Sealants
« Reply #4 on: May 06, 2021, 02:59:55 PM »
Here's several shots showing the tank fittings coming through the bulkhead where I'd like to seal to prevent fuel from reaching the tank compartment and soaking into the fuse. The tank will be removable so I rather not use forever epoxy.

Steve

Offline Steve Dwyer

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Re: Fuel Resistant Sealants
« Reply #5 on: May 06, 2021, 03:31:50 PM »
Here's the Permatex Permashield

Steve

Online Jim Svitko

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Re: Fuel Resistant Sealants
« Reply #6 on: May 06, 2021, 03:41:09 PM »
I would forget about the Permatex and instead coat all surfaces of the tank compartment and engine bay with something like finishing epoxy.  No need to try to seal off the tank compartment.  You probably would not succeed anyway.

Two-part auto clear might work as well.  That is what I use to coat inside of cowlings.

Nice looking plane.


Offline Dan McEntee

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Re: Fuel Resistant Sealants
« Reply #7 on: May 06, 2021, 03:51:45 PM »
   I have used white silicone for wing fillets with no troubles. Your fuel line is silicone. If you are wanting to seal the larger holes, and if you have to remove the tank, it will come out anyway, just use regular silicone caulk. It's not like you are going to pour it over it all the time. You probably have some of it on hand. If you buy the Permatex product, use just a few dabs, the rest may go bad before you need it again. Being resistant to gasoline is different that alcohol also. It may be resistant to gas, but NOT to alcohol . You could take a piece of this plastic like credit card stock, drill some nice fitting holes in that to match your tank plumbing, and glue that in place with the clear silicone and create a better seal and use less silicone. And if you ever need to remove it, you will be able to do that also.
   Good luck with it,
    Dan McEntee
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Offline Steve Dwyer

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Re: Fuel Resistant Sealants
« Reply #8 on: May 07, 2021, 05:55:29 AM »

I have coated the tank compartment several times using clear butyrate dope before I painted the plane. Good idea Dan, I think I'll place small tabs on the bulkhead over the fittings using 1/32" plywood sealed behind with silicone. That should prevent seepage of fuel and still allow for removal of the tank in the event I ever have problems. No point in using expensive Permatex when a dab of clear silicone behind the tabs will work fine.

Thanks everyone,

Steve

Offline Trostle

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Re: Fuel Resistant Sealants
« Reply #9 on: May 07, 2021, 02:46:50 PM »
Why have any "openings" (holes) in the firewall behind the engine?  Cut down the portion of the firewall so no openings exist at all.  If there is any reduction in strength or stiffness of the nose section, my experience is that it is negligible.  Makes it a lot easier to install and remove the tank.  Still need to fuel proof everything in the engine and tank compartments with resin or some form of epoxy.

Keith
« Last Edit: May 07, 2021, 06:37:03 PM by Trostle »

Offline Steve Dwyer

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Re: Fuel Resistant Sealants
« Reply #10 on: May 08, 2021, 06:02:24 AM »
Keith,

Certainly looks different from the 50s style configuration with a Jameson Special. Nice layout!!

Steve

Offline George Grossardt

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Re: Fuel Resistant Sealants
« Reply #11 on: May 08, 2021, 08:34:47 AM »
Why have any "openings" (holes) in the firewall behind the engine?  Cut down the portion of the firewall so no openings exist at all.  If there is any reduction in strength or stiffness of the nose section, my experience is that it is negligible.  Makes it a lot easier to install and remove the tank.  Still need to fuel proof everything in the engine and tank compartments with resin or some form of epoxy.

Keith

Clean!

Offline Juan Valentin

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Re: Fuel Resistant Sealants
« Reply #12 on: May 08, 2021, 12:42:16 PM »
Hello Steve
                        I would use a piece of rubber from an inner tube. Cut a square piece of rubber and punch two holes spaced to the spacing of the tubing going thru the firewall. Push the tubing thru the small rubber square and then fly the plane in case you would have to adjust tank height. once the tank is set right just glue the piece of rubber to the firewall but not to the tubing that way you can slide the tank out if needed. Here are some pics.
                                                                                                                                                                                           Juan

Offline Steve Dwyer

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Re: Fuel Resistant Sealants
« Reply #13 on: May 09, 2021, 08:10:11 AM »
Juan,

I like this idea best of all, keeping the rubber on the tank side of the bulk head affords more available length of the vent and filler tubes into the thickness of the 1/8"  bulkhead to attach the fuel line tubing. I can still apply a dab of silicone on the fitting where it come through the rubber for extra assurance; this leaves the tank fully removable as well.

Good idea!

Steve


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