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Thread: os 61sf


  1. #1
    MetallicaJunkie's Avatar
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    os 61sf

    11800 peak on a MAS 12x7 scimitar stock muffler
    10% nitro
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    RE: os 61sf

    12200 peak on a MAS 12x7 scimitar macs head on a macs muffled pipe (untuned)
    10% nitro
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    rainedave's Avatar
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    RE: os 61sf

    Stock muffler; 10% Powermaster; APC props; warm, humid weather; rich of peak:

    12x8 - 10,780

    12x6 - 12, 140

    11x10 - 10,860

    11x11 - 9,780

    David

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    RE: os 61sf

    I'm hoping to run mine with the pipe and a 12x8 today or tomorrow.

    I'll take some tach readings.

    David
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    MetallicaJunkie's Avatar
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    RE: os 61sf

    looks good.... i plan on running mine as well, i finally got around to putting the finishing touches on the bird the SF is going into..... i cut about one inch off the stock length header, hopefully ill get it to sing higher ill be using a 12x6 xoar/jfx black prop..

    any new numbers, with yur set up?
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    RE: os 61sf

    13,300 peak w/ 10% @ sea level with a 12x6 xoar nylon and 1" cut off the header. Does hat sound about right, this is my first tuned pipe setup i have tached
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    RE: os 61sf

    MJ, I ran my SF w/pipe for a short while, but I didn't take any tach readings. I can't really do a lot of running on the patio, so I need to take the engine to my field. I cut my header to 6" which is what Macs recommends for this engine. But, I extended it a bit with a longer Aerotrend blue coupler. I'm using the 10cc Long Stroke quiet pipe #1062. Anyway, it really sounded strong with an APC 12x8 and as I tune the length I'm sure it will get better.

    I think you 13,300 sounds good. It will probably go up as you shorten the header. However, I think this engine was intended to be propped around 12,000 or so. I'm setting mine up for a 12x8 or 11x10 (they turn about the same) and I hope to get close to 12,000. I'll be very happy with that, if I get it.

    BTW, Graves R/C is selling the #1062 long stroke pipe for $52.99. It's the cheapest I've seen anywhere. I got it in two days; great service, IMO:

    http://www.gravesrc.com/MAC_S_MUFFLE..._p/mac1062.htm

    Macs lists this pipe for $100.95!

    I'll post again when I have some numbers. Maybe by next week. Oh, it's going in my Bridi UFO:

    http://www.rcuniverse.com/forum/m_4017336/tm.htm

    David

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    RE: os 61sf

    Hmmm, i think i'll take your advice and run a higher pitch prop, as you know way more about these kinds of things... its just that when ever i hear a tuned ppe i used to hearing them scream.. I know my pipe is a macs, it has a baffle in it... but im not sure its the quiet pipe.... you got a good deal Gravesrc is awesome,,,, i can remember when i was a teen you could get the combo(pipe/header) for about the same price as a pipe is going for now. So you lengthened the header with a longer couple to get less RPM? My SF is in a Miss Norway.... i am going to maiden her today According to the original owner it hasnt flown in over 20 years
    ORIGINAL: rainedave

    MJ, I ran my SF w/pipe for a short while, but I didn't take any tach readings. I can't really do a lot of running on the patio, so I need to take the engine to my field. I cut my header to 6" which is what Macs recommends for this engine. But, I extended it a bit with a longer Aerotrend blue coupler. I'm using the 10cc Long Stroke quiet pipe #1062. Anyway, it really sounded strong with an APC 12x8 and as I tune the length I'm sure it will get better.

    I think you 13,300 sounds good. It will probably go up as you shorten the header. However, I think this engine was intended to be propped around 12,000 or so. I'm setting mine up for a 12x8 or 11x10 (they turn about the same) and I hope to get close to 12,000. I'll be very happy with that, if I get it.

    BTW, Graves R/C is selling the #1062 long stroke pipe for $52.99. It's the cheapest I've seen anywhere. I got it in two days; great service, IMO:

    http://www.gravesrc.com/MAC_S_MUFFLE..._p/mac1062.htm

    Macs lists this pipe for $100.95!

    I'll post again when I have some numbers. Maybe by next week. Oh, it's going in my Bridi UFO:

    http://www.rcuniverse.com/forum/m_4017336/tm.htm

    David
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    RE: os 61sf

    Please post your Miss Norway info in the Classic Pattern forum; a lot of folks will be interested to see how it flew.

    The only reason I extended the pipe was to make sure I had some leeway to make adjustments. The Macs info might be for maximum rpm and I want to work up to that gradually.

    David

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    RE: os 61sf

    Ok will do, my maiden flight with her went well. I didnt do any abrupt maneuvers with her but she knife edged nicely, did nice hammerheads,loops, and axial rolls.... i ended up like the sound of the motor best with a 12x6 apc, i tried an 11x9 but the motor didnt seem to like it i didnt have a 12x8 to try out
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    RE: os 61sf

    I finally tached my SF .61 with a Mac's long stroke quiet pipe.

    APC 11x10, Powermaster 5% nitro: 11,630

    I cut the header to 6" as the Mac's site suggests. I haven't done any serious tuning yet.

    David

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    RE: os 61sf


    ORIGINAL: rainedave

    I finally tached my SF .61 with a Mac's long stroke quiet pipe.

    APC 11x10, Powermaster 5% nitro: 11,630

    I cut the header to 6" as the Mac's site suggests. I haven't done any serious tuning yet.

    David
    This number, Dave, is a respectable 1.42 HP.

    ...But it's not exactly piped engine material, I am afraid.


    MJ's number on the 12x6 Xoar sounds exaggerated, however, at 2.26 HP


    Experience with this engine on a length-adjusted pipe, suggest ~1.85 HP to be a typical real-life output.

    Without a tuned-pipe (i.e. with the normal, included OS muffler), about 1.25-1.3 HP is the expected output.
    Dar Zeelon - ISRAEL - ddzeelon@gmail.com
    MVVS - Jett - MS Composit - Rossi - Mejzlik

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    RE: os 61sf

    Thanks Dar. I have not yet begun tuning the header length. That figure is with the 6" starting point and an addition 1/2" gap from the coupler. If I reach 12,000rpm I will be more than satisfied. Running 15% nitro instead of 5% will be good for a couple of hundred, too.

    David

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    RE: os 61sf

    Dave,


    It is the length adjustment...

    The RPM difference between 5% and 15% would typically be ~200-300...


    Dar Zeelon - ISRAEL - ddzeelon@gmail.com
    MVVS - Jett - MS Composit - Rossi - Mejzlik

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    RE: os 61sf

    Then, I'll easily hit or break 12,000 when I get the header trimmed down and use hotter fuel. 12, 250 would equate to 1.65hp; 9.26lbs of thrust and a pitch speed of 100mph. Perfect for my 7 1/2lb Bridi UFO.

    David

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    RE: os 61sf

    OS 61SF, well used, stock muffler, Omega 10%...

    12~8 wood Zinger = 10,000

    11~10 wood Zinger = 10,000

    13~6 APC = 11,000

    13~8 APC = 10,000

    More later.

    Terry in LP

    edited for: Later results. Same engine/fuel but all APC props.

    12~7 = 11,500

    11~10 = 10,600

    13~9 = 9100 (this is a heavy prop)

    14~5N = 11,200

    Gotta get my flightbox battery installed so I can use a starter instead of a chicken stick.




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    RE: os 61sf


    [/quote]

    This number, Dave, is a respectable 1.42 HP.

    ...But it's not exactly piped engine material, I am afraid.


    MJ's number on the 12x6 Xoar sounds exaggerated, however, at 2.26 HP


    [/color]
    [/quote]

    Sorry im replying so late but thats the number my globee tach gave me, perhaps its maybe off cuz i was taching it in the shade, but i doubt it
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    RE: os 61sf

    13,300 is really too high for this engine. If it were an FSR I'd say great, but the SF was designed to spin in the mid elevens. A 12x8 or 11x10 are about the best props to use.

    David

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    RE: os 61sf

    ill have to give a higher pitch a try, im just so used to trying to get higher rpms out of my engines, and hearing them scream, especially since its on a pipe
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

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    RE: os 61sf

    I fully understand. Think of the SF/RF series as OS's attempt to design a 2-stroke that would run more like a powerful (for its day) 4-stroke: quieter running on bigger props at lower rpms. Remember, it wasn't too long after the Hanno was in production that pattern fliers switched to 120 4-strokes. In retrospect, the SF/RF engines represent a transitional time period between the short stroke screamers turning 11x7's to the 120 4-strokes turning high pitched props.

    David

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    RE: os 61sf

    I ran my SF with its Mac's 10cc long stroke quite pipe again today. This time I surpassed my target rpm of 12,000.

    Temp: 67°
    Powermaster GMA 5/22
    OS #8 plug
    APC 11x10
    12,128
    1.6hp
    8.72lbs. static thrust

    Calculated prop speed is 99.8mph. This setup is extremely quite. Below 1/2 throttle it's not much louder than a 4-stroke.

    David

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    RE: os 61sf

    I cut another 1/4" off and I think I'll stop there. Length of my header is now 5 3/4" and Mac's web site suggests 6" for this engine.

    Temp: 70°
    Powermaster GMA 5/22
    OS #8 plug
    APC 11x10
    12,337
    1.68hp
    9.02lbs. static thrust

    This is probably about the maximum power this engine will produce with this prop. Going up to 15% nitro would add a bit, too. Though, nine pounds of thrust is a lot for an 11" prop, and the calculated speed is 101.5mph.

    I have an extra backplate with a pressure tap and a pump. If I ever come across an #86 pump carb I'll see if that adds anything, but those carbs are extremely rare unless you buy the whole engine.[]

    David

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    RE: os 61sf

    Ok, I'll admit it, I think I paid a record price for a carb recently.
    Over $100.00 for a hanno special carb, 6P.
    I"m building a hanno special from parts, all new parts, in fact.
    It will be using a perry pump, and I'm port matching a standard RF block.
    And a Shadel piston/Liner. I'll try and get it together soon and post something.
    It's not really a hanno, just a fancy SF/RF ......

  24. #24
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    RE: os 61sf

    Sounds like a great project. Let us know how it progresses.

    David

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    RE: os 61sf

    I would think these old piped .60 size engines would have a hard time beating a super tiger .90 from a cost, weight and performance standpoint (at $119.00 it's lookiing pretty good in that respect).
    From a sound and nostalgia standpomt.....priceless


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