Tank position

[Gary Dowler]

Might be a rookie question, but I'm a rookie so....

Profile P-47 Stunter. Was started some time back by Gerald Schamp, now it's being completed by me.  Will have a 46LA on it when it arrives. (Engine shown is just to show position).  My 4.5oz uniflow is at hand.  Given a lot of room to position it, should it be forward and snugged right up behind the motor, or a little further aft towards the CG?


Or

[Perry Rose]

That particular tank can go close to the engine as in the top photo. I always place my tanks as close to the engine as possible.

[Jim Svitko]

Depending on how that LA 46 is set up, the nitro content of the fuel, and weather conditions, 4.5 ounces might not be enough.  Most of the time, I have been able to get by on a bit less than 4.5 ounces using 5/22 fuel.  But, because of different conditions at some contests I have attended, there have been times when I needed about 4.75 ounces.

[Paul Walker]

Make your mount adjustable. Moving the tank will affect the way the motor runs, and your preferences for that run on that plane with your flying ability.
Farther forward,  less break when the nose goes up or down. Farther back, more break. The LA 46 is a good running engine and should "tolerate" either position.

[Tony Drago]

How do you like  your Dillon Press.

[Brett Buck]

Listen to Paul, but, while it should work, I think the tank you have (probably 2" wide) is probably marginal without muffler pressure, so plan on that. I would strongly recommend not making the tank any more than about 1.5" wide from the base of the engine mounting plane to the furthest edge. This will reduce the pressure drop from the uniflow "uphill" against centrifugal force to the venturi. And for sure start with it as close to the rear of the engine as you can get it.

     Brett

[Ken Culbertson]

Depending on how that LA 46 is set up, the nitro content of the fuel, and weather conditions, 4.5 ounces might not be enough.  Most of the time, I have been able to get by on a bit less than 4.5 ounces using 5/22 fuel.  But, because of different conditions at some contests I have attended, there have been times when I needed about 4.75 ounces.

Jim - I am curious what prop you are using and how rich?  The only IC ship I currently fly is a 610 sq" profile with an OS46LA and I get the full pattern and about 10 or so laps on 3.5 oz.  5.4 laps.  Maybe I have a teeny venturi.  Don't know size, it is stock whatever that is.

As for the thread question -get it as close as possible but I have one where "possible" is a full inch behind the engine.   The LA runs well close up or way back.  It is just a tolerant workhorse.

Ken

[Scott Richlen]

LA-46 runs well on muffler pressure to the uni-flow.  Brand new, the LA-46 gobbles the fuel (making you think that you need a larger tank.)  After a bunch of flights you'll notice the fuel use going down.  I've been using 15% syn/5% castor at either 5 or 10% nitro.

Some like to kick back on starting and throw the prop, so I always flip mine counter (it doesn't do this all the time, but usually at a contest.....)

Very reliable and consistent engine runs.

[Gary Dowler]

You guys are awesome. Paul, Brett, it shall be done as you say.  Thanks to all for your input!!  Today should see another coat of silver on it. Getting closer! 

Gary

[Paul Walker]

About how much of an adjustment would make a difference?

M

Any change will make a difference. It will depend on venturi size, mixture, amount of oil in the fuel, prop selection, rpm, head clearance, glo plug to name just a few. For your set-up, you will have to test to find out.

[Gary Dowler]

Got about 3/4 done with an adjustable fuel tank mount.  Not only will the tank position be adjustable, but there is room for the 5oz version if it's needed.

Gary