Fuel Tank Alternative for OS 20 FP BBTU

[Paul Raley]

I have read most of the posts about the Flite Streak OS 20 FP killer installation by Dan Rutherford and Brett Buck.  I have all the major components, but unfortunately I am about a decade too late to be able to buy the 3 oz Hayes clunk tank which was listed as a mandatory part of the package.  Is there a proven substitute for this tank?  There is one on ebay for 59.99 but I don't want it that much...

[Brett Buck]

I have read most of the posts about the Flite Streak OS 20 FP killer installation by Dan Rutherford and Brett Buck.  I have all the major components, but unfortunately I am about a decade too late to be able to buy the 3 oz Hayes clunk tank which was listed as a mandatory part of the package.  Is there a proven substitute for this tank?  There is one on ebay for 59.99 but I don't want it that much...

    Sullivan SS-4 is what I use. Plumb normally for suction, use muffler pressure, and put the "flat" side up against the fuselage so it is not too wide.

        Brett

[Paul Raley]

    Sullivan SS-4 is what I use. Plumb normally for suction, use muffler pressure, and put the "flat" side up against the fuselage so it is not too wide.

        Brett

Excellent. Thanks Brett!

[Paul Raley]

    Sullivan SS-4 is what I use. Plumb normally for suction, use muffler pressure, and put the "flat" side up against the fuselage so it is not too wide.

        Brett

I have not run suction in a long time.  Would I cap the overflow and run the vent to the muffler? 

Just got the answer from one of your previous posts; overflow to muffler and vent/uniflow to bump

[Brett Buck]

I have not run suction in a long time.  Would I cap the overflow and run the vent to the muffler? 

Just got the answer from one of your previous posts; overflow to muffler and vent/uniflow to bump

    Glad you found it helpful!

     Brett

[Motorman]

Paul, Those plastic tanks are nice but, they can be hard to get the plumbing in and there's really nothing magical about them. Go on the Brodak site and find a metal 3oz uniflow wedge tank(BH-548), solder a couple of brass angles (BH-777) on it then bolt it down and fly.

MM

[Brett Buck]

Paul, Those plastic tanks are nice but, they can be hard to get the plumbing in and there's really nothing magical about them. Go on the Brodak site and find a metal 3oz uniflow wedge tank(BH-548), solder a couple of brass angles (BH-777) on it then bolt it down and fly.

MM

   I think that one is too wide for reliable operation. You might get away with it if you use really thin fuel, or if you recess it into the fuselage by about 1/2". But otherwise, I have seen 2" tanks give unstable runs because the pressure drop is too large pulling the fuel "uphill" against centrifugal force.   I think it is much better to run a narrower tank, I would suggest no more than 1 3/4". A Nobler-size tank is about that size, I think Brodak makes one of those, too, essentially the same thing but 1/4" narrower. I haven't tried it, I made my own and it worked fine, but that will give you a better chance.

    Brett

https://brodak.com/medium-wedge-uniflow-fuel-tank-7oz.html

   Which is 2x as large as you need, but can easily be cut down. Again, I haven't tried it but I think this will give you a better chance if you don't want to use the Sullivan tank.

[Paul Raley]

   I think that one is too wide for reliable operation. You might get away with it if you use really thin fuel, or if you recess it into the fuselage by about 1/2". But otherwise, I have seen 2" tanks give unstable runs because the pressure drop is too large pulling the fuel "uphill" against centrifugal force.   I think it is much better to run a narrower tank, I would suggest no more than 1 3/4". A Nobler-size tank is about that size, I think Brodak makes one of those, too, essentially the same thing but 1/4" narrower. I haven't tried it, I made my own and it worked fine, but that will give you a better chance.

    Brett

https://brodak.com/medium-wedge-uniflow-fuel-tank-7oz.html

   Which is 2x as large as you need, but can easily be cut down. Again, I haven't tried it but I think this will give you a better chance if you don't want to use the Sullivan tank.

The Sullivan tank can be mounted inboard right?  It is too long to fit behind the motor on the FS

[Brett Buck]

The Sullivan tank can be mounted inboard right?  It is too long to fit behind the motor on the FS

  Yes, if needed.

    Brett

[Colin McRae]

Paul, another option:

This is my Flite Streak (OS 25 LA) with a 2.5 oz Brodak oval profile uniflow tank on muffler pressure. Engine runs fine and stable, no issues (APC 9-4 sport prop at 12,000 rpm on the ground). I have the same tank design on 4 different models using various engines. These tanks from Brodak are shorter compared to the Brodak wide wedge design and fit on models with short noses.

However, one change. The 'stock' Brodak oval profile uniflow tank has the fuel pickup on the top of the tank adjacent to the uniflow vent tube. This is not a good design IMO as the fuel line routing is not efficient and goes up and down on its way to the spray bar. I had Brodak do a custom mod for me (a few extra bucks) to simply relocate the fuel pickup to the bottom of the tank so the fuel line is a short straight shot under the engine to the spray bar. Has worked great for me.

And I run the muffler pressure line to the uniflow vent, not the overflow. The overflow is plugged during flight.

And if you want to try a 3 oz, the Brodak website shows all the tank dimensions for you to check to see if it will fit. But I would think 2.5 oz should be enough for a 20 FP on a Streak to get thru the pattern.

[Martin Quartim]

  Yes, if needed.

    Brett

Brett,

donīt you get even better results with the fueltank mounted inboard?

It works very very well in my R.M S1 this way.

Martin

[Brett Buck]

Brett,

donīt you get even better results with the fueltank mounted inboard?

It works very very well in my R.M S1 this way.

Martin

    I tried it on the Skyray, but I am running fast enough to be stable even with the 1 1/2" of hydrostatic pressure, so it didn't make a big difference. If you were going to run it on larger props, centering the tank, or moving it inboard, is probably better. Centering it, you could use something like Motorman suggests, because it will fit between the engine bearers.

     I note that the 9-4 prop is intended to be inefficient enough to get the RPM and shaft HP up without generating too much airspeed (per the other thread) and increase the fuel draw. It's nowhere near the max diameter or minimum pitch the engine can handle. I have seen people running Tornado 10-4 3-blades, it got pretty hot but ran just fine.

     Brett

[Motorman]

When I first started with CL Endurance I did an experiment with 4 tank locations. Above the wing inboard and outboard and below the wing inboard and outboard. The only difference it made was the needle setting. Running with the needle valve almost closed is tricky so, I went with below the wing outboard to get the most opening on the needle valve. Don't know if that relates to stunt or not.

MM

[Lauri Malila]

  Yes, if needed.

    Brett

Maybe the .20FP is less sensitive, but isn't it quite extreme to change from one side of fuselage to another?
I mean, my basic setting is such that the end of pickup line is 6-8mm more "out" than the hole in spraybar, measured from fuselage centerline. Then I try a few different lateral positions with 3mm increments.
It's certainly worth experimenting. L

[Brett Buck]

Maybe the .20FP is less sensitive, but isn't it quite extreme to change from one side of fuselage to another?
I mean, my basic setting is such that the end of pickup line is 6-8mm more "out" than the hole in spraybar, measured from fuselage centerline. Then I try a few different lateral positions with 3mm increments.
It's certainly worth experimenting. L

   It is a substantial difference. I ended up using uniflow when it was inboard, to limit the pressure head change from the ground to air.

       Brett