I'm about to start a four star 60 kit, and have seen several people install 16oz tanks for longer running times. They usually install a hatch of some sort so they can get to the tank later, if necessary.

I was going to go ahead and do this mod, figuring I'd regret it later if I was spending too much time refueling as I'm sticking a 91 4s on it, when I noticed the Sullivan Flextanks on Tower's site.

Anybody used these? Looks like I could pull it out later without the need to construct some type of hatch.

Just curious what your experiences were with these?

Thanks,
Heath

Anything Sullivan makes is great and they are a top notch company in my book. The flex tanks are great and they say you can reform them somewhat to fit into tight spaces with a heat gun and I bought two for a twin project and the flexibility enabled me to literally squeeze them in. Take some reenforced shipping tape and make a handle on the rear of the tank and you'll be able to get it out. Personally I like hatches for access to everything.

If you have access to reach your hand in and pull the tank back (with the tape handle mentioned above) then you don't need a flextank.

Dave Segal

There is really only one cosideration when deciding on using a flex tank. If your motor is a YS brand then your tank is going to be under considerable presure from the pump on the YS (use the stiff tank). If your running a non pumped motor say like a Saito then use either tank.

Wow - -YS puts out that much pressure that its a serious consideration huh? Learn sumpin new every tiime I hang around these forums!

Well, not using a YS, got a thunder tiger 91 four stroke.

So, any reasons NOT to use one? Thinkin' I'm gonna try it if no one has something bad to say about 'em.

Thanks,
Heath

One thing no one has mentioned about the flex tank is why it is!
To install this tank it is possible to run your fuel tubing through the fire wall and then suck the air out of the tank and make it very small. Then put the tank in place and cut your fuel tubing to allow the tank to expand to original size and shape.
I have a Pattern plane that this is the only way that you can change out or repair the tank. If it wasn't for the flex tank you couldn't service or replace the tank..

Just my $0.02 worth


Don

I have used a heat gun to squeeze a 10oz tank into a GP PT-40. Taking what I say with a pinch of salt since I have yet to fly my plane (or any other for that matter), this is my story.

Tank was slightly too big for the compartment when all the control rods ar running through it. GPlanes recommends a 6 or 8 oz, but LHS "expert" said 10oz would fit, and be better. I took 10oz, and sure it fitted, but only if it "bent" the control rods for the nose gear, and throttle. I decided to make the tank longer and thinner using heat gun and re-forming. Only needed to make the top 1/3rd of the tank narrower by 1/4 inch, and needed to make the back end slightly more pointy so that I could force the tank into the compartment without cutting away too much of the fuel tank compartment floor (I had already cur away some, but needed just a little more).

So, out came heat gun, and blasted it until the plastic goes transparent. Made me a little nervouse, but it only goes mouldable at that point. Then, reshaped tank as desired.

The final result looked pretty amateurish, whih was to be expected, but the tank did fit, and I could squeeze enough foam around it to avoid impeding the control arms.

Problem was when I re-installed the clunk in the tank. Re-forming of tank means that the clunk can not reach all the corners. If I had the plane level, then I had to shorten the clunk flex so that the clunk rested on the floor of the tank. but then, it was about 1/2 inch from the back. Lengthening the clunk to reach the back meant that the clunk would never fall quite to the floor.

My concern that I would suddenly suck air instead of fuel made me decide to can the 10oz tank, and go with the smapper 8oz. My reasoning was that I probably had only 8oz of reliably reachable fuel anyway.

So, reforming the tank is easy, but reforming it so that you have access to your fuel, and you can feel confident in it is something else.

gus

P.S. I would need a huge suction to deflate the tank. I could not guess what would be needed to do it. I can not picture doing what Perdo suggests, although maybe with bigger tanks it would work (10oz is quite rigid and tough).

Sullivan makes more than one kind of tank. The "Flex Tank" is almost transparent and if very easy to remove the air and make the tank kind of flatter. The standard sullivan tank would be almost impossible to suck the air out. it indeed would have to have heat to reform. but the flex would just push in where the control rods went by it.


Just a thought
Don//