Hey folks! I've just completed my Tower Fun 51. I have a Magnum 52 Four Stroke onboard which gives great performance, but shakes the front of the airplane to death. I'm running into an issue with the fuel in the tank foaming. I've attempted to secure it a number of different ways, but the result is always the same. I can get the motor to run well enough to fly for a while, but as soon as it gets to about a 1/3 tank it begins to suck air and lean out. I've heard about octyl alcohol as a defoaming agent but, I don't know A: where to get it and B: whether anyone has used it before. I've read that Armor All and vinyl cleaner works, but I don't want to put a bunch of different things in my fuel when I can minimize the amount of contaminants and achieve the same result without fouling plugs. Any help anyone can offer would be great and I appreciate your time.

Get rid of the zip ties or Velcro straps. Use a 1/2" foam rubber pad under the tank and some screwhooks and use 2 rubber bands to hold the tank on. If it's not a Hayes you can add a sintered bronze clunk. Forget the foaming agents and dampen the vibes transferred to the tank.

I think the photo uploaded successfully, but this is the current setup I have running. I've varied between 1/2 to 1 1/2" of latex foam and regular foam rubber. This is the second tank I've tried, but my LHS has a somewhat small selection of tanks and I'm loathe to buy another tank if I can fix it with configuration or minor changes.

Also, it appears there is an excessive amount of rubber bands, but those are actually looped together to reduce the amount of tension applied between the tank and the fuselage. I.e., one band is made up of two or three joined rubber bands. I don't want the tank to seperate during an outside snap!

I have had real good luck with a chunk of EPP foam........it's the stuff they pack computers in. It's high density, and really absorbs the vibration. Mount it just like you have the foam....but you don't need that many bands......just enough to hold it in place.

You may also want to check your prop balance......you should not have that much vibration to cause flameout!!

Have you flown it yet? I didn't see any wheels on the plane in the pic. If you haven't the foaming is always worse on the ground. Once in the air that takes away most of the foaming. I have had plenty of profiles with no problem on the foaming. Does seem like a lot of rubber bands. Remember to bring more with you to the field. Sometimes they will snap early if they get any fuel or exhaust on them. Check them every flight. One more thing you may want to do. Put a small hose on the Crankcase nipple. We have two of these and they do blow a fair amount of oil out of the nipple in flight. And it is pointed right at your foam which will just suck it up and make a mess.

I know its a issue with foaming, but you may want to try shortening up the fuel lines a bit, I've always noticed the shorter the lines, smoother the engine runs, at least in my experience.

I appreciate all the input! The plane is missing a tire due to a nut backing off on landing roll out (good place for it!) I've ordered some new props and double checked the existing one on it. It appears to have been a little off, so rebalancing it should mitigate some of the vibration. Other than that, I'll continue to work the issue! Thanks again.

That looks like a Sullivan Flex tank in the photo, with too many rubber bands. The flexible tank is probably transmitting the vibration straight to the fuel instead of allowing the tank to "float" inside the rubber bands.

I'd suggest trying a normal tank mounted with two #64 rubber bands to see if the problem goes away.

I've built a lot of Control Line profiles and that fuselage design is pretty anemic. I haven't built my Fun 51 yet but I remember studying the plans and thinking it's all wrong for strength. You're laminating balsa over a double lamination of Lite Ply. Would be better with the Lite ply being the outside lamination. Profiles suffer from a lot of flexing and will commonly break right at the wing leading edge. This flexing could be a cause for your excessive foaming. I've been adding 4-7 drops of Armor All to every gallon of fuel as an anti foaming agent with no ill effects.

So you might consider strengthening the front of that fuselage, eliminating some of the flex and maybe the foaming wont be as significant.

Food for thought?

Those tubes exiting the front of the tank are way too long and will shake the heck out of the tank. Make them no longer than about 5/8" or so. Also if you had 4 hooks like usual instead of 2, the bands would not have to be quite so tight or so many, allowing the foam to do it's job better. Use a fuel filter right before the engine. That tends to condensate air bubbles. The cintered clunk seems to work good but I haven't used them yet on my profiles and am doing okay. Man do you have some right thrust!

Good luck, keep us posted and have fun.

Ernie

Go here http://www.ronlund.com/Merchant2/mer...y_Code=Filters
And scroll down to fuel magnet and bubbleless klunk. The Heli guys use both. I don't think you are supposed to let the fuel magnet get dry. (It needs to stay submersed in fuel). I'm not sure about the bubbleless clunk. There was a pretty good thread on them at Runryder. I havn't used one. But I'm just getting into helis, and thats where Iread about them.