nitrobeast

Hey guys

I am building my first arf which is my second plane a sig 4 star 40. In the manual it mentions that its a good idea to seal the tank. What should i use?

Any other tipe for a new guy?

Thanks

ro347

My Feedback: (13)

Would regular silicone hold up to glow fuel?

nitrobeast

Not sure. I figure someone will know what to use.

carrellh

I have a 4*60 ARF. The actual tank seal comes from tightening the screw that holds the stopper assembly together.

If I remember correctly, it mentioned using RTV silicone sealant around where the fuel tank stopper comes through the firewall.

It also mentioned sealing the wood in the fuel tank compartment. There are several ways to do that.
Brush water based polyurethane on the wood
Brush fuel proof dope on the wood
Mix up 30 minute epoxy, thin with a few drops of acetone or denatured alcohol, brush on
Mix up 30 minute epoxy, thin by heating with heat gun, brush on

bigedmustafa

My Feedback: (2)

Good question, I normally just make sure that the rubber stopper or plastic cap is screwed on tightly. It's a good idea to check it every so often, as well.

jmurphy18

I am assuming they mean to seal below the tank and the area. Use thined 30min epoxy. Thin with heat. Better know as fuel proofing the area if I read this right.

Took me to long to type this, you got lots of good answers.

Scar

My Feedback: (3)

This sounds like a translation error. Typical instructions say to fuelproof the tank compartment. A fuel leak will soak into untreated balsa or ply, and weaken the structure. Others have mentioned good methods for fuelproofing.

Is it really Sig?

Best wishes,
Dave Olson

FlyingGreg

My Feedback: (4)

Just tighten the screw holding the lid on. Test it by plugging the vent line and blowing into the fuel line. Squeeze it off with forcepts and let it sit for 5-10 minutes. Release the forcepts and your should get a woosh of air. If not hold it under water and blow into the line again to identify where the leak is. Others mentioned fuel proofing the tank area--a good idea.

nitrobeast

No error here. I want to know what to you use seal the rubber to the actuall tank? I am trying to avoid any chance of the fuel making it out. I do understand fuel proofing the compartment.
The instructions say to use silicon and then put the tank in. Do they mean to use silicon to glue the tank to the engine wall?
Sorry for the dumb questions.

bruce88123

You seal the rubber to the tank by tightening the screw and that's all. I'm sure what Sig had in mind was sealing the opening in the firewall where the tank stuck thru with silicon.

Trollmaster

Would be a better idea to chuck that tank and spend $4 on a better on like Sullivan etc. Cheap Arf Tanks are notorious for causing problems

CGRetired

My Feedback: (1)

I recall a recent post about fuel tanks and the rubber stopper and how to install this and what is to tight or to loose.

Follow the instructions for the tank, and when final assembly is ready (you've trimmed tubing, bent the metal tubes, put the clunk on the feed line, and so on), the screw that goes through the stopper to that round 'nut' on the inside of the tank is tightened. Do NOT tighten it until you start to sweat trying to turn it more. That will insure that the tank will split at some point and.. of course, fail.. spilling fuel in the tank compartment. Just tighten it until it is snug but still slightly rotates. It will self seal after that and not leak. Any tighter and it will split by pressure from the inside by that stopper expansion.

If they are talking about sealing the tank compartment, well all of the above are great. I simply use epoxy resin (used to bond fiberglass.. it is plenty thin) or a long setting epoxy that is basically thin, and adding some alcohol to thin it out a tad bit more, and brush it in.

If you have done all of this, you may also use your finger to apply a light coating of RTV or Silicon sealant (use clear rubber or silicon bath tub sealant) around the neck of the tank and push it into the hole in the firewall and let it set up, which might take overnight to set up properly. This will seal the tank compartment from the engine compartment. Do not over do-it, though. Enough is enough when you can see it but it is not bulging out.

FlyingGreg

My Feedback: (4)

Yeah--I think CG Retired is right- Some arfs come with a hole in the fire wall for the whole tank stopper assembly to fit in. While I don't think its necessary, guys will use Goop or some other silicone sealant and glue it in. Sometimes hard to get out. I like to wrap strapping tape around the tank and make a little tab to pull on to remove it.

CGRetired

My Feedback: (1)

Thanks, Greg. It's not necessary, but if you gotta do it, then that's the way I would do it. I've done that on some planes and not done it on others. No noticeable difference. In both planes, the tank compartment stayed dry. The big thing is not to over tighten that tank stopper. As said before in another post, tight enough is so it is sealed but can still rotate (with some effort, but will still rotate). It won't leak if done right and over tightening it will only cause the tank neck to split.

DS.

nitrobeast

Great info guys, thanks for the help.

ro347

My Feedback: (13)

Is brushing water based polyurethane on the wood a good solution to fuelproofing the engine compartment and area around wing opening?

richardehead

I've always put RTV silicone around the stopper on the OUTSIDE of the tank. Once you've socked it down as the others have suggested, put a thin bead of RTV (room temperature vulcanizing) silicone around it. I also put RTV around the fuel tubing where it connects to the brass tubing (again, on the OUTSIDE). All of that probably isn't necessary but it's cheap insurance against a stopper leak.

For sealing the engine and tank compartment I've always used epoxy finishing resin. It's already thin so you don't have to mess with alcohol and regular epoxy. Finishing resin can be mixed (it's two-part as well) and then painted on with a brush. Dries at about the same rate as 30-minute regular epoxy.

CGRetired

My Feedback: (1)

Yeay, actually, that's what I use. It is thin enough to apply with an acid brush (cheap and you just throw it away when done) and give a good coating, and let it set up overnight for a good permanant bond. It will be totally fuel proofed that way, and will not add any significant weight. You can thin out 30 minute epoxy, but the epoxy finishing resin is real easy to work with and apply.