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Best Firewall Sealer

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Old 07-27-2010, 07:30 AM
  #1  
mccolld
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Default Best Firewall Sealer

I want to determine what material is best to seal the firewall and fuel compartment of a gasoline powered plane.

The two that come to mind are epoxy and polyurathane. Does gas affect either of these?

Can you think of anything else to use? (no silicone!)
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Old 07-27-2010, 07:45 AM
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Default RE: Best Firewall Sealer

This is my experience:

1. I have used epoxy thinned with rubbing alchohol. Works well but with time, the epoxy peels off in the engine compartment.
2. If the surface of the firewall is large enough, I cover it with monokote. Works very well.
3. For small spaces or small firewalls, I am using balsarite. However, I haven't use it for long time for giving you a fair assessment about it.
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Old 07-27-2010, 08:12 AM
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Default RE: Best Firewall Sealer

Z Poxy finishing resin.
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Old 07-27-2010, 08:54 AM
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mccolld
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Default RE: Best Firewall Sealer

Does the epoxy hold-up to exposure to gas (and ethanol) over time?
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Old 07-27-2010, 09:07 AM
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Default RE: Best Firewall Sealer

I prefer epoxy but avoid trying to thin it with alcohol. Use a finishing resin (it is thin) or just simply mildly warm 30 minute or longer epoxy as you apply it. Thinning epoxy with anything will weaken the chemical bond which makes epoxies so durable, heat works much better and creates a much more durable coating. Epoxy paints work well also, for instance Klass Kote is excellent and, if you use a light color like white or yellow, makes the area inside the fuse much more visible if that is a requirement for installation of fuel lines, tanks, etc.
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Old 07-27-2010, 11:05 AM
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Default RE: Best Firewall Sealer

Hi!
35 years in the hobby and I don't use anything!
Just fly!
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Old 07-27-2010, 11:12 AM
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Default RE: Best Firewall Sealer

To seal a firewall you can use:

polyester resin
epoxy finishing resin
slow-cure epoxy glue
polyurethane varnish (may need a few coats)
clear butyrate dope (or colored to match the model.
epoxy-based paint (whatever color you like)

All of these are moderately fuel-proof. Keep the fuel exposure low, or keep it clean, and use fuel with 15% nitro or less, and the finish will keep its sealing properties.
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Old 07-27-2010, 11:28 AM
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Default RE: Best Firewall Sealer

I use the same mix for gasoline that I use fot glow - 30 minute epoxy thinned with about 20% acetone. It seems to hold up as well to gasoline - but then I am more gareful, generally, and little dribbles exaporate quickly. I also use a Jersey Modeler Fueler that has a take-up line so there is no overfill squirt.

Really can't say if it would hole up to long term pooling as in a tank leak. However, with gasoline you know it almost immediately if the model is near you from the odor of spilled gas.

If you are real worried an automotive primer or enamel would be gasoline safe. I also know folks who topcote giant scale fabric with polyurethane for the fuel proofness.
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Old 07-27-2010, 11:49 AM
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Default RE: Best Firewall Sealer

Pretty much everything Bill posted. I started as a kid using clear dope, I use finishing resin when I have some in my shop, I have been using thin epoxy using 90% alcohol to thin it most the time. I have even used fuel proof paint for the inside of wood cowls. I haven't tried the varnish though or poly U for fuel proofing. I always have 30 minute epoxy and alcohol in my shop so that is my number one product.
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Old 07-27-2010, 01:35 PM
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Default RE: Best Firewall Sealer

OK, I'll fess-up......I use thinned epoxy for my firewalls for glow and gas and have never had a failure ~ been flying since about '88.

My real reason for asking the question is for a repair job that I'm doing to my SeaDoo. It's fuel guage has failed. The float inside the sending unit that resides within the gas tank has a leak. What I'm going to do is drill a small hole in it and drain it. Then, I plan to plug the hole with JBWeld. Next, I want to coat the whole thing with a thin layer of ????something????. I haven't decided what. All it needs to do is plug the microscopic hole(s) that have developed over the last 10 years or so.

The float is in gas all the time.

So guys, what sealant do you recommend? All suggestions.....(realistic) creativity welcomed!

Thanks!
Doug
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Old 07-27-2010, 03:08 PM
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Default RE: Best Firewall Sealer

Hi, all of the above but also...

I Googled SeaDoo fuel tank float - this was the first link - [link=http://www.seadoosource.com/fuelfloat.html]Seadoo Float[/link]

Not 100% sure this is the part but it seems you can replace it very easily and cheaply without having to worry about the repair failing.
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Old 07-27-2010, 08:00 PM
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Default RE: Best Firewall Sealer

No need to seal it with anything the JB Weld will do the job. With sealing it you run the risk of weighting it down which could cause the carb to flood. It should be real easy to find the pin hole or leak. Most brass floats when they leak it will be along a soldered seam. JB Weld is perfect for this and is impervious to gasoline.

Vince
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Old 07-28-2010, 07:07 AM
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Default RE: Best Firewall Sealer

Vince,

It's not the carb float. It's a plastic float inside the gas tank.

I could buy a new one but why? The fix is so simple.

I'm leaning toward epoxy paint. Comments?

Doug
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Old 07-28-2010, 07:12 AM
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Default RE: Best Firewall Sealer


ORIGINAL: mccolld

Vince,

It's not the carb float. It's a plastic float inside the gas tank.

I could buy a new one but why? The fix is so simple.

I'm leaning toward epoxy paint. Comments?

Doug
Yeah, if it comes away and fouls the fuel system it'll cost more than $20 (cost of a new float) to fix...

Isn't a SeaDoo about $10Ks worth of gear.

Anyway - have fun with it! [sm=thumbs_up.gif]
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Old 07-28-2010, 08:14 AM
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Default RE: Best Firewall Sealer

Seems like thinned JB weld would do the job. I thin it with denatured alcohol and use it as a heat sheild for mufflers that are real close to the fuse.
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Old 07-28-2010, 08:51 AM
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Default RE: Best Firewall Sealer

Edwin,

Good suggestion. The float is inside a plastic "sending unit". The "sending unit" is sealed at the top with what looks to be JBWeld. It has a fine mesh screen at the bottom so, should the coating delaminate, it will get caught in the screen (plus the system has two filters, too ~ 1 fuel line and 1 @ carb).

Doug
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