Andrew

Like many of you, I've had difficulty finding fuel tubing flexible enough to keep a clunk on the bottom of the tank at all times. I wanted to use a film can tank on a Cheap Delta and stopped by the LHS to pick up some small tubing. My LHS now caters mostly to cars and when they sell out of plane related products, they generally won't reorder -- so, no small tubing. I had noticed earlier that they carried silicone insulated battery wire that was very flexible, so I bought a couple of feet. At $.70/ft, it was cheaper than tubing and I thought I might be able to use the insulation. I purchased General Silicones Ultimate Wire Mega-V in 14 AWG. (www.willstech.com/listings.html or www.gsracing.com/gsracing/page.asp -- search for wire).

It has about the same ID as small tubing, but thinner walls and is very flexible -- it does take some effort to strip the insulation from the wire. I liked CombatPigg's idea of using a single length of tubing, but he mentioned having to be careful not to collapse the tubing where it passed thru the tank stopper. Being of the Old F**t generation, many of my friends have stints [] -- for you younger guys, a stint is a short piece of semi-rigid tubing placed into an artery to open it and keep it from collapsing -- I used a stint.

I cut a 1/4" piece of brass tubing, rounded the ends smooth and worked it into the insulation to the location where the tubing would pass thru the can bottom. With the brass tubing inside, it gives a good tight friction fit around the outside. The bamboo skewer points to the location of the "stint". I took an old clunk from a split Sullivan tank, cut the barb off and sweated in a piece of 1/8" brass tube -- the insulation would not fit over the barb. Plain tubing with a wheel collar or two would probably work too. The vent line also has a piece of tubing inserted.

The attached images show the clunk, fuel line with stint in place (skewer point) and vent line. One of the images shows how much the insulation will flex -- the fuel line was held inline with the tank at a location where it would pass thru the bottom -- you can see that the clunk will droop well past the tank floor.

I don't know how the ends of the tubing will hold up to being repeatedly removed and reattached to the spraybar barb on the engine -- but if it splits, you can always splice on a piece of standard tubing.

the "other" Andrew

Andrew

Here are two more images of the finished tank -- one on the inside and one from the front. I think this will work well and extends the good ideas already presented here. Time will tell, but the cost and ease of building one of these is really low.

the "other" Andrew

jboy381-RCU

have you soaked a peice of it in fuel???that stuff might get hard as a rock like the cox stuff...great idea tho,let us know how it works for ya...

john

DICKEYBIRD

Very cool & creative there Andrew! It should ought'a work great. Being silicone and designed as a heavy use, hi-temp insulation, I'll bet it'll hold up great.

gusman

I tried building a tank from the fuji container for my ap .061. It worked for a little bit but the brass tubing is so small that it's hard to keep it open when cutting and stuff. It is also hard to keep stuff in place.
My first question is should i use regular size tubing and second what kind of clunk will fit small tubing if i use that. And third if i use small tubing, what size brass tubing should i use. Thanks
Gus- the man

Andrew

Hi John --

Since it was a high-temp silicone, I had felt like DickeyBird that it should work, but had not soaked it. The COX tubing is not silicone, vinyl possibly or other PVC based plastic. In any event, I think this insulation would have been more likely to soften or swell. I did soak a piece in 25% nitro fuel for 72 hours with no apparent ill effects. My guess is that UV will have a greater impact than the fuel.

Gus --

The tubing that ships with fuel tank kits and associated tank stopper kits is usually annealled -- the brass is softer and allows the tubing to be bent without collapsing or cracking. The tubing I used was 3/32" OD and 1/8" OD hard brass -- available at the LHS is 12" and 36" lengths. The 3/32" was inserted into the tubing to keep it from collapsing and give me a good tight friction fit when I pulled the tubing thru the bottom of the tank. The 1/8" tubing was sweated into the clunk (after cutting the original barb away) because the clunk had a 1/8" hole in it -- the original barb was too large for the insulation. The typical "small" silicone fuel tubing will slip over 1/8" and 5/32" with no problem. You can buy clunks, but if you don't have one left over from a blown out tank, just make one with a piece of 1/8" tubing and a couple of 1/8" wheel collars -- you can add or remove collars depending on the weight needed.

I think the guys building the tanks with tubing passing thru the bottom are probably using 1/8" OD, but will let them respond.

I have cut tubing with a tubing cutter and with an abrasive dremel cutoff wheel. The tubing cutter leaves a ridge on the outside that should be dressed off and a ridge in the inside that can be chamfered away with a pocketknife or you can file both away by filing off the end about 1/32". I prefer the cutoff wheel both for speed and less cleanup. In either case, be sure to flush out any chips or filings before hooking up your engine.

The fuel consumption rate of the smaller engines is so low that 1/8" or 3/32" OD tubing would be more than sufficient for acceptable fuel flow.

the "other" Andrew

Larry Driskill

Gus,

I cut brass tubing with a #11 Exacto blade by rolling the tubing back and forth under the blade with moderate pressure.

rrragmanliam

My Feedback: (1)

Highly flexible silicone fuel tube can be had from sig #sh284 and Sullivan #201. I've used both in the film tanks and they are plenty flexible enough to get the clunk to the bottom of the tank without wory as to there fuel proof effectiveness.

Rrragman

rrragmanliam

My Feedback: (1)

An excellent idea Andrew. Do you solder them? I think I would.

Andrew

I had read on the forum that the Sullivan tubing was very flexible -- I used the insulation only because the LHS was out of small and I didn't want to wait and pay shipping from one of the mail orders. The insulation looks like it will hold up OK and it's readily available locally. And, I'm always looking for alternate ways of doing something -- some work and some don't -- but it's all part of our hobby.

I haven't, but probably should (someone once said, "Expediency is the downfall of the fool) -- DuBro and Great Plains collars are brass with chrome or nickle plating -- probably to get a good stick, the plating should be removed. A little quick work with a Dremel would do it.

the "other" Andrew

rrragmanliam

My Feedback: (1)

.

Yea I hear you Andrew. Please note that the two part numbers I listed are tubing MFG specificly for 1/2A. The regular sullivan small is not the same thing. It's not nearly as flexable and will not work. I have my LHS order for me from sig whenever they order from them and it saves me the shipping. I didn't want to pay $7.00 shipping in a two dollar item either. Thanks for the tip in the clunk. I got my last few micro clunks from the other Andrew in Canada. Now I can leave him alone as it seems he always has a very full plate!

Rrragman

gusman

I've been away and just read your responses today. I think that the fuel tubing i got at my LHS was a lot smaller than what your talking about. i had to buy this really small brass to fit through it and you can hardly see thru it. so now i will buy some other small stuff but hopefully not this small. and i will also buy 1/8" size brass tubing. Is that right? and where should i buy this stuff.
thanks again

gus

Larry Driskill

I had an issue today with changing needle settings on my throttled VA bolted to a LiteHawk wing.

I think I have tracked the problem down to a small split in the film can cap where the silicone tubing went thru the plastic.

If that was the problem, then the slight amount on muffler pressure to the tank may have been escaping thru an intermittent leak that changed the pressure to the needle.

Has anyone else had a problem with the plastic cap splitting?

combatpigg

My Feedback: (3)

Yep, I've had the same problem too. I think we should start a class action law suit against DB! [>:]

Big Al-RCU

Absolutely, CP add me to the list! [8D]
al

DICKEYBIRD

Sorry, I ain't got no class....you can't sue me. However, I guess I should worry about a copyright lawsuit from Fuji in light of all the hoopla from Boeing and Lockheed these days.

Larry I had a couple split on me too so I changed to some softer blue fuel line I had lying around instead of the pink stuff I was using to seal the brass tubing. That seems to have stopped the problem. Also, I drill the bottom of the canister, not the snap-on cap. Maybe a difference there as well?

Larry Driskill

Thank you DB.

I'll look around the shop for some softer line.

Turning the can around might be problematic on this setup. The tie wrap might pop the lid loose.

andrew b

A brass clunk?? why not use an aluminium inline fuel filter that has a brass nut screwed onto it, clunk and filter in one and while your at it, why not use tubular heat shrink over the entire tank. Get a piece thats almost the same diameter as the tank and a little longer. When you hit it with the heat gun (carefully) the excess ends will shrink and make the thing try to go a sausage shape as the unsupported ends shrink and pull the top tighter on.

what anyone think of that?

Toad

How much fuel do these fuji film cans hold for real? I was useing the std sulivan 1oz round at the race last weekend, I was sputtering for fuel on the 11th lap,. I would luv to find a slightly larger tank, say maybe 1.25oz that handles pressure from a backplate. We have a one minute start window, if I start early in that minute, I risk running out of fuel durring the heat. If I wait till the 30sec mark, my tired fat old butt may not make it to the start line in time. I need a slightly bigger bucket of go juice in there.

dieFluggeister

Cap Splitting---

I had the same problem and then started melting holes instead of drilling them. It forms a thick little ridge around the hole that seems to add strength and relax the plastic. I haven't had a split yet, knock on wood.

I have had a lot of trouble with the fuji tank leaking around the lid. Still havent solved that problem yet.


I got my hands on a hotel shampoo bottle that is the exact same size as a film canister except that it has an aluminum screw on cap! Unfortunately it was from a hotel my wife stayed at on a corporate business trip. Too expensive for a regular joe like me to stay at.[]

Larry Driskill

I like your melting suggestion. I am going to build me a couple like that.

With digital cameras everywhere, I worry a bit about continued can availability. I once got several cans from the film developer at a local supermarket and think I best pay them another visit.

Andrew

I've been using sharpened brass tubing -- I wonder if a drill leaves a nick that eventually turns into a stress fracture. The melting approach might cure that problem. I also try to pick a hole size where the silicon tubing is snug, but not too tight.

I had been getting cans from Walmart, but lately, I haven't been able to get any at all -- we don't have a full time film processor here, so I may have to look for another source too.

max cook

how about high school photography class? I'm taking photo and we colect the canisters to recycle, about 2, 2'x2'x3' cardboard boxes a semester.

or just take more pictures of your planes!!!

max

GallopingGhostler

I don't think so. When I drill plastic, I use by hand a larger drill bit to remove the burr around the hole, above and below. That should remove the "nick". Using a sharp, not worn bit helps cut a clean hole without much force. Also, I use a speed slow enough that the bit doesn't significantly heat the plastic. It should cut cleanly through with next to no force.

049flyer

My Feedback: (18)

I use fuel line from here: Texas Timers

There fuel line is thin wall and very flexible, they have different sizes. The smaller sizes work great for 1/2A engines and the larger size has an inner diameter equal to normal medium size tubing but is way more flexible, perfect for those 2 oz to 4 oz tanks used with .15 to .25 size engines.

I use film canister tanks and a modified fishing weight from Walmart for a clunk, no problems getting every drop out of the tank regardless of what I do with the airplane.

The stuff is a little “spendy” but worth every penny, it works great and has ended my search for a perfect tank/clunk/ fuel line for all of my planes from .020 up to .25 glow.