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Foaming Fuel

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Old 07-02-2007, 08:24 AM
  #1  
Debris Field
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Default Foaming Fuel

I have a scale twin engined Cessna which by very neccessity has fuel tanks that are bound a little too tight in their cradles. Now this is causing the fuel to foam somewhat at high RPM. it is not a holed fuel line, loose bung or any of these other reasons as i have been up and down that path allready. There is no room to further soft mount the fuel tanks either, so we have to deal with what is there.

I mix my own fuels using 17% Coolpower and 15% Nitro. What can I add to my fuel to reduce it's tendancy to foam? I had heard that a few drops of dishwashing liquid will do this (!! yeah I know, dishwashing liquid itself foams in a sink full of water !!) from a well known fuel mixer around my parts. can anyone comment?

This site is soooo large that a search on this leads to thousands of irrelevant posts, so sorry if it seems obvious to someone.....

cheers

Mick
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Old 07-02-2007, 08:51 AM
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bigchap
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Default RE: Foaming Fuel

use felt clunks or add a couple of drops of silicon into the tank each time you fuel up.
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Old 07-02-2007, 08:57 AM
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BillS
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Default RE: Foaming Fuel

The only way I found to stop fuel foaming is to mount the tanks loosely in latex foam rubber. If the tank is against wood anywhere fuel will foam at some rpm.

Redesign whatever necessary. Fuel foaming will shut an engine down and on a twin an engine down is bad news.

Good luck.

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Old 07-02-2007, 09:11 AM
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Default RE: Foaming Fuel

what size tanks? My idea would be to take those tanks out and put in some bladder tanks that CANT foam (the fuel NEVER mixes with air thus you can actually ziptie these tanks to the firewall and it wont foam)

This is my idea because i dont like the idea of adding stuff to fuel (silicon will turn to glass on your glow plug[&o])

So I guess one of the ideas would be to look at getting a "Tettra Bubbless fuel tanks" or a "Bubble-Jett Tanks " from http://www.jettengineering.com/ you will also need a tanker type thing

yes its expensive put its 100% fuel proofe this is what they use in pylon racing were there running nelsons turning 32 plus thousand rpm and foaming is a big deal.
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Old 07-02-2007, 09:43 AM
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Default RE: Foaming Fuel

I agree with the bubbleless tank suggestion. You can get them in some pretty large sizes: I have an 18 oz one in my cermark f16. I use bubbleless tanks on all of my planes and never have a fuel bubble problem.
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Old 07-02-2007, 11:18 AM
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Ed Smith
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Default RE: Foaming Fuel

Bladder tank, the only way to absolutely prevent fuel foaming, and place the tank on the balance point not right up behind the firewall.

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Old 07-02-2007, 11:35 AM
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Default RE: Foaming Fuel

felt clunk,felt clunk,felt clunk.keep it simple!
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Old 07-02-2007, 12:07 PM
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Default RE: Foaming Fuel

I was once test running my spitfire inverted with the wing off. I was surprised to see the clunk bouncing about 1/4" off the tank; It ran fine then and ever since in the air.
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Old 07-02-2007, 03:44 PM
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Debris Field
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Default RE: Foaming Fuel

Geez thanks guys, plenty of good stuff there. I'll have a look into them all.

thanks

Mick
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Old 07-02-2007, 04:18 PM
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Ed Smith
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Default RE: Foaming Fuel

felt clunk,felt clunk,felt clunk.keep it simple!
Nothing simpler than a bladder tank. Just two lines, a feed line and a pressure line. Not only will the foaming be eliminated but the engine run stays the same from start to finish. The engine will not go lean as the tank empties.

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Old 07-02-2007, 06:53 PM
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wylieruneyjr
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Default RE: Foaming Fuel

I,ve heard of peope putting a few drops of armorall in their fuel. Also bubbless clunks in tank. Tower Hobbies has one, the best one sold by ys four stroke engine company.
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Old 07-03-2007, 02:42 AM
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Default RE: Foaming Fuel

G'day Mick,
Try all the above, & also make very sure your Props & spinners are properly balanced, not just the blades but the hubs as well, after all, vibration is what causes fuel foaming, if you can reduce vibration, it has to help.
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Old 07-03-2007, 02:14 PM
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macdona
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Default RE: Foaming Fuel

I have good luck with Sullivans Flex tanks. I have a twin seaplane with ten ounce tanks stuffed in the nacelles and have no problems what so ever.
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Old 07-03-2007, 05:49 PM
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Jerry Sigur
 
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Default RE: Foaming Fuel

Padding the tanks with foam is a good idea. I've also used
two drops of armorall in every gallon of fuel I've ever used.
No probs, no foaming, no glow plug problems. Been doing it
for years.
Try shaking a gallon of fuel with no armorall and then adding
two drops to it and see the difference.

Good luck with it
Jerry
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