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Engine basics => Engine set up tips => Topic started by: frank mccune on October 16, 2013, 05:24:53 PM

Title: Can a tank be too large?
Post by: frank mccune on October 16, 2013, 05:24:53 PM: Hi All:

I have been having problems with the tank set up on my Fox.25 profile stunt trainer.

The problem is that after I set the engine to run a great 4 cycle on the ground it leans out to a screaming 2 cycle in the air that results in a very hot run. The engine is fried when it finally lands! Thanks to a large proportion of Castor Oil in my fuel , the circa 1953 Fox still has a bit of compression.

The tank is 2.5" long,1.5" tall and 2.375 widr. The distance to the fuel pickup crease in the tank is 2" from the nva. Is this too far to draw fuel? There are no leaks in the system or fuel foaming as far as I know. Is this tank, four oz.. too large for this application?

I need to ask about the profile tanks that Veco and Duke Fox sold at one time. These tanks were designed to used on profile planes but I have been told that they will not work! They look good but what do I know? The Veco box call it a T series tank. Pehaps I should convert these tanks to a Uniflwow system to see if they work. Any thoughts about these tanks?

I am having the same problems with a Midwest Me 109 profile stunter with a 5 ounce wedge tank and an O.S. .35 Stunt. I converted the tank to uniflow but that seemed to make the problem worse. Any thoughts about this prblem?

Perhaps it is past time for me get new tanks! Lol Hello Brodak!!

Thanks for any input that you may have concerning my tank problems.

Stay well,

Frank
Ps.
This tank on the Fox .25 worked very well on a slow combat plane in the 80's. It is a suction tank.
Title: Re: Can a tank be too large?
Post by: Brett Buck on October 16, 2013, 06:34:32 PM: Quote from: frank mccune on October 16, 2013, 05:24:53 PM
The tank is 2.5" long,1.5" tall and 2.375 widr. The distance to the fuel pickup crease in the tank is 2" from the nva. Is this too far to draw fuel?

That sounds like a good guess. It's still drawing fuel, but the pressure drops as you build up speed, and the faster it goes, the leaner it gets.

Brett
Title: Re: Can a tank be too large?
Post by: Chris Wilson on October 16, 2013, 09:14:31 PM: Place the tank inboard?
Title: Re: Can a tank be too large?
Post by: Balsa Butcher on October 16, 2013, 09:19:32 PM: Get a Brodak or RSM modern uniflow tank. Yes, both tanks are too large. You will probably only need a 2.5 ounce tank for the 25, 3.5 ounce for the 35 S. They are very thrifty. Try some bench runs to confirm. 8)
Title: Re: Can a tank be too large?
Post by: frank mccune on October 17, 2013, 05:36:55 AM: Hi Guys:

Thanks for the replies! "I needed that!" Lol

Frank
Title: Re: Can a tank be too large?
Post by: Brett Buck on October 17, 2013, 10:19:18 AM: Quote from: frank mccune on October 17, 2013, 05:36:55 AM
Hi Guys:

Thanks for the replies! "I needed that!" Lol

Frank

It's not too large so much as it is too wide. Try a Sullivan clunk tank with the flat side up against the fuselage.

The 20FP needs a relatively narrow tank on a conventional profile mount. A typical Veco wedge tank will not work.

Brett
Title: Re: Can a tank be too large?
Post by: Tim Wescott on October 17, 2013, 12:03:35 PM: The LA 40 that I have has the same problem -- I had a wide metal tank on the plane, and had to launch blubbery rich so that when the plane leaned out it was about right.

I changed to a Sullivan clunk as Brett describes (but with a uniflow, just because). The plane runs roughly the same on the ground as it does in the air, I can adjust the needle by RPM instead of by listening to the nature of the blubbery richness, life is good.