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Fuel Tank Frustration

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Old 03-23-2006, 01:48 PM
  #1  
Mikel-t
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Default Fuel Tank Frustration

Maybe because I hate doing fuel tanks I almost always get something wrong. My prefered install is using a 3-line system and would like to know an easy method of pre-bending vent tubing and what material is best. Also I can never get that stopper tight enough without twisting all the plumbing around. Can sealing caulk be used to safeguard the seal?. I would gladly pay 3x's the cost of an average glow tank if it was already plumbed and sealed ready for exterior lines. Hey, why do you think ARF'S are so popular..... Mikel-t
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Old 03-23-2006, 02:25 PM
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greyfoxx
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Default RE: Fuel Tank Frustration

A good friend shared this with me, and I have found that it works quiet well. I was in working on one of my new planes the other day and was building the fuel tank. While I was bending the brass tubing I felt compailed to share this “how-to” tip with my fellow club members. This tip was shown to me by our own club member Bill Pierce and is one of the best tips on how to do something that I have learned since being in this hobby. Bill presented this to us in one of our meetings a couple of years ago but just in case you missed it or you are a new club member hungry for knowledge in this hobby here it is. Many of you seasoned builders that have been around this hobby a while will most likely already know how to do this. I found one of the most annoying things about bending nice curved radius bends with tubing is that ever so annoying kink that you get when you bend tubing very far. You can purchase tubing benders and there are several out on the market that work well but one of the best, simplest and cheapest I have seen is taking a common hex head bolt and 2 hex head nuts. This is how it works. You simply Lay the tube on the bolt against the threaded part and screw in the hex nuts up against the tubing. This sandwiches the tubing between the 2 hex nuts and when you start to bend it the hex nuts will not allow the tubing to kink. It is amazing how something so simple works so well. Goes back to the KIS method (Keep It Simple). You need to use at least a 3/8” diameter bolt. I use a 5/8” diameter bolt and the larger the diameter the bigger radius you can bend. The bolt I use is also about 5” long. You don’t have to have one that long but it gives you something to hold on to like a handle when making bends. Attached is a drawing showing how this works. You can open it in WORD and you may have to zoom up to see a better view of it. I have a drawing this if you need it. Just send me an e-mail at greyfoxx@charter.net and I will send you a copy.

As for the other problem, I have not yet experienced that problem. You might try so RTV Silicone like used on automible transmissions. I know of some that insist on using that before they secure the stopper.

"Experience is a hard teacher. She gives the test first, and the lesson sometime later!"
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Old 03-23-2006, 02:30 PM
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bubbagates
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Default RE: Fuel Tank Frustration

Mikel,

there are tubing benders that you can buy that look like springs that slide over the tube abd you bend it with your hands. There are also others that you insert the tubing into, hold or place one end of the tube onto something solid and bend it as much as you need. Then other that has two handles you move as much as you need once you insert the tube. The other way is to bend it ever so carefully with just your fingers but that can lead to pinching.

Here are some links to various ones

http://www2.towerhobbies.com/cgi-bin...?&I=LXE228&P=7

http://www2.towerhobbies.com/cgi-bin...?&I=LXR791&P=7
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Old 03-23-2006, 02:45 PM
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k3 valley flyer
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Default RE: Fuel Tank Frustration

Two words - Hayes Tanks.
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Old 03-24-2006, 10:47 AM
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fishmissile2000
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Default RE: Fuel Tank Frustration

The last tank I put together I got everything arranged and right before puting the stopper in I wiped my finger around one time with alcohol and water I had sitting close by for plane cleaning and it slid right in no trouble and evaporates fairly quickly there was hardly any resistance on the way in. Also there was so little water it never even made it into the tank as condensation.
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Old 03-24-2006, 01:50 PM
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dant-RCU
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Default RE: Fuel Tank Frustration

Mikel-t:

Here is my method on the stopper. Throw away the stupid screw and simply tap the screw holes with a 4-40 tap. Then use a 4-40 hex head bolt and tighten the stopper with a ball driver. it is much easier to get the stopper the correct tightness using a hex-head bolt and a ball driver so get a good grip on the stopper with one hand and go for it. Once done, I run a bead of Silicone Sealer around the cap where it fits to the tank. Smooth with the finger, let it set and you should be just fine. If you ever need to take the tank apart it is easy to get the sealer off with an x-acto knife.

Works for me - "your mileage may vary".

Dan
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Old 03-24-2006, 10:49 PM
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Default RE: Fuel Tank Frustration

Hey greyfoxx, great tip for bending tubing. I'll give it a try next time. I have a couple other suggestions for bending tubing without using a special tool.
Use a piece of wire as close to the inside diameter of the tube. Make your bend and then pull the wire out. Fill the tube with fine sand or suger or salt. seal the ends. make your bends. If I have to tell you to remove the sand. then this method is too advanced for you
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Old 03-24-2006, 11:21 PM
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David Cutler
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Default RE: Fuel Tank Frustration

Use a Hayes tank. They don't have tubes stuck through a plastic/rubber stopper.

I have always used them with a YS engine as they can hold their pressure much better.

They come in various sizes. This is an 8 oz one:-

http://www2.towerhobbies.com/cgi-bin...&I=LXK830&P=ML

-David C.
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Old 03-25-2006, 08:11 AM
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flipstart
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Default RE: Fuel Tank Frustration

The easiest way I have found to bend tubing without buying a bunch of benders is to use string trimmer line that is close to the ID of the tubing. Just slide it in, bend and pull plastic string back out. This plastic string also works for helping to thread the fuel tubing through the firewall on a big fuselage. Push the string into firewall holes, attach to tubing lines and pull tank into position. As for sealing the stopper on tank, use the pure silicon grease, a little smeared on the stopper, and it inserts easily, this stuff does not harden like RTV. Pressure test under water and you have a trouble free tank.
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Old 03-25-2006, 03:25 PM
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Ernie Misner
 
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Default RE: Fuel Tank Frustration

The trick on tightening the screw in the stopper is to do it over a period of time. Assemble the tank before you actually need to install it, and just snug the screw good the first time. The next day you will find that the screw will easily turn another 1/2 turn. (the rubber is "forming" it's fit into the neck of the tank) Do this a couple of more times and you will have a stopper that does not leak, but yet will not split the neck of the tank because it hasn't been forced all at once and is not too tight.

Also, use 5/32 aluminum tubing rather than 1/8" tubing. It fits tighter in the rubber stopper holes (the tubing does not want to twist when you tighten the screw), and the tank fills and drains easier.

Ernie
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Old 03-25-2006, 08:56 PM
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Mikel-t
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Default RE: Fuel Tank Frustration

Great suggestion Dan with the 4-40's I will give a try as this is second tank installation this week!. I'm swapping out tanks and engines in my Funtana 90 and going with a Saito 150 so I'm wrestling with tubes again, I did however try putting a piece of silver solder in the tube after I poked it thru that cheap-as-a donut stopper, and made an effective loop in it, to make a nice vent tube....can't tell where it is in relation to the bubble however, geezz I hate doin this!!!!!!. Dave how do you test your tank ? ..hooked up to a test stand engine or what? Thanks. I pretty sure that the little tank I did Monday is'nt thru giving me a hard time yet.
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Old 03-25-2006, 09:16 PM
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Default RE: Fuel Tank Frustration

Something I haven’t seen mentioned above anywhere but maybe I missed it. Before you even think about bending brass tubing heat it in a clean flame until you see it change color. This is annealing the brass tube and when it cools down you'll find it bends like soft aluminum in your fingers. No need for benders, nylon, nothing.
Without annealing it’ll tend to kink.
Try it, you’ll like it. It doesn't tke a lot of heat.

Cheers
Glen
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