ST G-61, Optimal prop for best vertical?

ST G-61, Optimal prop for best vertical?
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ST G-61, Optimal prop for best vertical? - 5/27/2008 7:45:09 AM

twn

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Joined: 4/8/2007
From: Revelstoke, BC, CANADA
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I'm currently running a st 61 with a 12-5 MA the vertical is ok but I am hoping for more.

Its in my midstar the weight is about 5.8lbs

What is the best prop for this engine for best thrust? (not speed)

< Message edited by twn -- 5/27/2008 3:17:14 PM >

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RE: ST G-61, Optimal prop for best vertical? - 5/27/2008 5:56:08 PM

Flyboy Dave

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....the 11-7 1/2 Master Airscrew is the best prop for most sport .61's.

FBD.

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RE: ST G-61, Optimal prop for best vertical? - 5/27/2008 6:15:02 PM

DarZeelon

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quote:

....the 11-7 1/2 Master Airscrew is the best prop for most sport .61s.

Dave,

I would have to disagree.

The 11x7½ and 11x7¾ were the best prop sizes for late '70s and early '80s, high RPM .60 F3A planes (before the advent of the 'Long Stroke'...). Those that would not fly below 50 mph...

But for sport flying with a muffler equipped engine (no tuned-pipe) and with the emphasis on best thrust, the 12x6 and 13x5 sizes will serve Tom much, much better.

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RE: ST G-61, Optimal prop for best vertical? - 5/28/2008 4:48:13 AM

Kweasel

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From: fort worth, TX, USA
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The 12-5 that you are using is very good for your application. Try some other brands around that size, remember to retune the needle between prop changes.

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RE: ST G-61, Optimal prop for best vertical? - 5/28/2008 5:21:35 AM

j.duncker

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When you say the best vertical are you talking about the ability to climb out vertically from a slow start. If so then try an APC 13 x 4W where the W means WIDE.

This should give the best thrust vertically.

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RE: ST G-61, Optimal prop for best vertical? - 5/30/2008 6:10:48 AM

xlr82v2

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From: Ellis Grove, IL, USA
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+1 for the APC 13-4W.

That's what I run on my Hangar 9 Ultra Stik 60. An old Supertigre S61K drags it around with authority... I used to run an APC 12-6 and liked it quite a bit, but I put on the 13-4W, and it made the airplane a lot more fun... more braking in the downlines, and more pull on takeoff and vertical... although it did lose a bit of speed... but the engine will sure sing with that 13-4W also.

If I use flaperons, I can takeoff with a ground roll of 3-5 feet, and then climb vertically nearly out of sight with a full tank of fuel, all on Omega 10% and the stock muffler (the old loud one, not the "quiet" new style). If I wait till near the end of the flight after I've burned off 6-8 ounces of fuel, the vertical is even better!

I was going to put my G90 on this airplane... but why? Gotta love the old Supertigres!!!

< Message edited by xlr82v2 -- 5/30/2008 6:11:25 AM >

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RE: ST G-61, Optimal prop for best vertical? - 5/30/2008 1:30:33 PM

Sport_Pilot

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I suspect the APC 12 1/2 x 3 3/4. But you engine will rev a lot higher. If the 13x4 will work it will be easier on your engine.

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RE: ST G-61, Optimal prop for best vertical? - 5/30/2008 2:51:56 PM

xlr82v2

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Yeah, I don't know if I'd trust the 12.5-3.75 to stand up to a 60... a healthy .40-.46 will already spin it up pretty good... I'd start worrying about throwing blades I think if it were on a good 60-61...

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RE: ST G-61, Optimal prop for best vertical? - 5/30/2008 3:29:29 PM

bob27s

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From: Cleveland, OH, USA
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Props are inexpensive....... experiment a bit.

Prop selection is a balance between the engine/exhaust system/airframe/indented application.

The answers you get here or in any forum are based on others experience with the same or similar combination of all of the above. The only way to know for sure is to measure/evaluate what you have now ....... change the prop ....... and try again.

For $3-$4 each, pick up an 11x7.5, a 12x6 ...... and the 13x4W. They rarely go to waste.

There are bonuses to each.

The 11x7.5 will allow the engine to turn up higher. On a 2C engine, higher rpm means more power being is being produced. The ST-61 actaully does enjoy turning higher rpm. You may find that the engine prefers to turn up a bit and the resulting climb performance might improve. Pipe or not, if the engine is "Happy", the aircraft will tend to perform better.

My experience with the ST 61 engine in similar rolls I agree with the 13x4W. However I might also look at a standard blade 13x4 and 13x5 props. And if I were looking for rate of climb for a climb-n-glide funfly event, i would probably try the 11x7.5 too. Again, a bit of testing.

Bob

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RE: ST G-61, Optimal prop for best vertical? - 5/30/2008 3:29:32 PM

DarZeelon

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quote:

ORIGINAL: xlr82v2

Yeah, I don't know if I'd trust the 12.25x3.75W prop to stand up to a .60... a healthy .40-.46 will already spin it up pretty good... I'd start worrying about throwing blades I think if it were on a good .60-.61...

Well, Brian,

That is exactly why the 13x4(W) and the 14x4(W) props were invented...

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RE: ST G-61, Optimal prop for best vertical? - 5/30/2008 8:09:12 PM

Sport_Pilot

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quote:

I'd start worrying about throwing blades I think if it were on a good 60-61...

I don't think it will rev that high. It is only 1/2" shorter and 1/4" less pitch than a 13x4.

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RE: ST G-61, Optimal prop for best vertical? - 5/30/2008 8:46:03 PM

xlr82v2

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quote:

ORIGINAL: DarZeelon

quote:

ORIGINAL: xlr82v2

Yeah, I don't know if I'd trust the 12.25x3.75W prop to stand up to a .60... a healthy .40-.46 will already spin it up pretty good... I'd start worrying about throwing blades I think if it were on a good .60-.61...

Well, Brian,

That is exactly why the 13x4(W) and the 14x4(W) props were invented...

Well, DarZeelon,

You are exactly correct.

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Post #: 12

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