Foaming tank

[Brian Dorricott 1]

I wonder if anyone can offer a solution to a problem with the tank in a Funfly. The Funfly was a old ARTF kit I picked up at Weston Park ( missing it this year) and decided to put it together after totalling my Spacewalker due to dumb thumbs. I have fitted a Saito 82 and used the tank supplied and all seemed well on the ground but we could not get full power consistently it seemed to hunt . It was landed and we could see air at WOT in the fuel pipe so it was taken to workshop and stripped down . The clunk had fallen off but nothing else found with the tank so it was replaced with a new tankatank tested again with the same result air in the fuel feed from tank . Standing over it with the wing removed showed that the tank was frothing like mad at WOT , I loosened the ply plate and foam that held it in place and voila the air stopped . The tank is fitted with neck through the bulkhead with a foam buffer around it and the ply plate has foam around where it holds the tank but this seems too rigid . Should I wrap it in foam and and wedge it in or something else ? The clunk is a straight brass one should I change it to felt clunk , would that help ? Any ideas as I'm a bit restricted as to what tank I can fit easily and the Seagull oval ones fit really well . Just to be sure I balanced the prop because of the vibration but it didn't help . Over to the more experienced types !

[FlyinFlynn]

I think you will find the foaming is purely down to the vibration, loosen the packing around the tank until it stops foaming and leave it at that. fit a felt clunk anyway as additional filtering is never a bad thing. I believe some people have added a few drops of washing up liquid to the fuel in the past to reduce the fuels surface tension to help reduce foaming but I do not know if that is a good idea or not.

[jrman]

A couple of drops of silicon furniture polish added to a gallon of fuel stops foaming.

[Former Member]

[This posting has been removed]

[Denis Watkins]

You should also stop the vibration Brian, re-balance the prop and fit an aluminium spinner if not already

Plastic spinners are often out of balance

Edited By Denis Watkins on 18/08/2020 10:54:04

[Jon H]

What fuel are you using? some are prone to foaming up

[Trevor Crook]

An anti-foaming trick I remember from my glow flying days is a couple of squirts of car dashboard cleaner in a gallon. I used to use stuff called Armor All. Contains silicon like furniture polish.

As suggested, try to get everything as balanced as possible.

[Jon H]

I wouldnt recommend adding random stuff to your fuel, there is no guarantee you wont damage the engine.

[Richard Wills 2]

Glow plugs will not thank you if you add too much silicone to the fuel, much better to cure the vibration issue.

[Brian Cooper]

Use Pro-Synth fuel from Weston UK.

It is designed to eliminate foaming in the tank. . Problem solved.

[Jon H]

Posted by Brian Cooper on 18/08/2020 15:06:34:

Use Pro-Synth fuel from Weston UK.

It is designed to eliminate foaming in the tank. . Problem solved.

Shame it foams more than any fuel i have ever known. Its why i asked the question in the first place as its very likely to be part of the problem if he is using it.

[Martin Harris - Moderator]

I've always found that packing foam around the fuel tank has been successful but I wonder whether the fact you're using a Saito 82 on what is presuably a lightweight airframe may be at the heart of the problem? I have never owned one but experience with clubmates' ones have coloured my opinion of them for this type of installation. My feeling is that they are build very lightly and with the recommended 20% nitro this results in an inherently rough running engine.

Perhaps try some lower nitro content fuel if you're running a higher percentage?

[Richard Wills 2]

On the Saito front particularly, a rich 180 can literally shake an airframe to pieces, although it is true of all engines is that if your needles are in anyway on the rich side vibration greatly increases, I have seen this often in helicopters where it can be bad enough to send gyro's crazy and the solution was simply to lean the motor out properly so it runs smoother.

Edited By Richard Wills 2 on 18/08/2020 22:13:56

[john stones 1 - Moderator]

You stated yourself, I removed the rigid ply plate, it was o.k, put some soft foam in n try it out.

Sometimes the answer is simple.

[Brian Dorricott 1]

Just to clarify its running on 12% Optifuel I don't use anything else . I will go with a loose fit so the tank can't escape but isn't rigid with foam to keep it roughly in place . Thanks for suggestions everyone better fixed in the workshop than deadstick above the Mersey where we fly !

[Engine Doctor]

If foaming persists fit a sintered metal clunk in the tank. These will help stop tower fuel from being drawn to engine and are an excellent filter. I always throw away original clunks and fit the sintered as standard, it's well worth it.

Ps also do as previous post say and loosen tank packing a bit an balance prop etc.

Edited By Engine Doctor on 19/08/2020 10:31:25

[Brian Cooper]

Posted by Jon - Laser Engines on 18/08/2020 16:03:14:

Posted by Brian Cooper on 18/08/2020 15:06:34:

Use Pro-Synth fuel from Weston UK.

It is designed to eliminate foaming in the tank. . Problem solved.

Shame it foams more than any fuel i have ever known. Its why i asked the question in the first place as its very likely to be part of the problem if he is using it.

Very strange. . Are we using the same Pro-Synth? . . Lol.

[Jon H]

Posted by Brian Cooper on 19/08/2020 11:08:07:

Posted by Jon - Laser Engines on 18/08/2020 16:03:14:

Posted by Brian Cooper on 18/08/2020 15:06:34:

Use Pro-Synth fuel from Weston UK.

It is designed to eliminate foaming in the tank. . Problem solved.

Shame it foams more than any fuel i have ever known. Its why i asked the question in the first place as its very likely to be part of the problem if he is using it.

Very strange. . Are we using the same Pro-Synth? . . Lol.

we are. I suspect its one of those situations where you only see if you look, and lets face it none of us usually look into our fuel tanks while the engine is running.

I only spotted it when i knocked a half filled gallon off the shelf and was surprised to see the amount of foam it created. A brief investigation followed and it was much worse than the other 4 fuels i had on hand.