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  1. #1
    GallopingGhostler's Avatar
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    YS Muffler on a Series 21 McCoy .40 Black Head Engine

    I've got a Testors Series 21 McCoy .40 Black Head engine that I plan to put in a 42 inches (1067 mm) wingspan Sterling Kit S-46 Profile Hellcat. It has about the same proportions as the Sterling S-1 Ringmaster. I had a spare YS muffler, so I did a few modifications to make it work for the engine.

    Attached are photos of my modifications. The only thing lacking is JB Weld epoxy filling of the original engine mount holes. Although I don't have a weight scale, the muffler seems to be about the same weight as the Tatone Peace Pipe muffler I was going to use.

    With the muffler's larger chamber, I'm thinking that it shouldn't slow it down or overheat it. Most of the time, manufacturers put on compact mufflers, because they are easy to pack in the box and cheaper to make. The slightly narrower muffler inlet is about the width of the cylinder sleeve. On other engines like OS and Enya, the side of the exhaust outlet contains the mounting bolt area. The muffler inlet height is slightly greater than the McCoy's exhaust outlet.

    I'll know more, when I test the engine, but I'm just wondering what you folks think.
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    George Hostler
    Clovis MADS AMA Club, Vintage R/C Society (VRCS)
    And we know love by this, that He laid down His life for us, and we ought to lay down our lives for the brethren. 1 John 3:16

  2. #2

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    RE: YS Muffler on a Series 21 McCoy .40 Black Head Engine

    I have built some mufflers and measured the backpressure of a factory muffler to establish a baseline. Three OS engines and a TT all showed approximately 16 inches column of glow fuel in a manometer. Is this a magic number??? I don't know, but if you test your setup and get a similar number, I bet you'll be OK. I used a three line setup to the tank: muffler pressure, fuel to carb, and another line with a clunk to a long piece of tubing attached to a yardstick.
    Chuck

  3. #3
    GallopingGhostler's Avatar
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    RE: YS Muffler on a Series 21 McCoy .40 Black Head Engine

    10 hours into curing of the generic JB Weld type epoxy sealing of the original muffler holes, while still soft, I filed the epoxy on the muffler's engine mounting surface true and flat. Today I ran the engine, she really spins a wooden Rev-Up 12x5 prop with authority, but was very happy with the Master Airscrew 10x5 prop. The motor runs fine with the YS muffler, didn't even overheat. With the 3/8 in (9.5 mm) muffler exit hole, it is a little louder. Rather than cap and drill a 1/4 to 5/16 in (6 - 8 mm) hole, I might use a silicon "exhaust off" pipe, which should deaden it if required.

    It looks like I have a winner. Now I just need to build a plane to house it. Still vacillating a little, but still have the Sterling F6F Profile Hellcat in mind.
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    George Hostler
    Clovis MADS AMA Club, Vintage R/C Society (VRCS)
    And we know love by this, that He laid down His life for us, and we ought to lay down our lives for the brethren. 1 John 3:16

  4. #4

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    RE: YS Muffler on a Series 21 McCoy .40 Black Head Engine

    George,

    A lot depends on what kind of flying you have in mind...

    The McCoy Series 21s were at least an ounce heavier than other engines of like displacement, unmuffled.

    As you mention, the Sterling profile F6F isn't much larger than a Ringmaster, so weight may be important. For just bashing the sky around - pure sporty flying - your combo should be fine. It might not stunt too well, and the kit isn't eligible for Old Time Stunt. It was introduced long after the event's "cut-off" eligibility date (31 Dec 1952 or earlier.)

    Might be an idea to drill up through the fuselage and leading edge to epoxy in a 3/16" dowel to reinforce the wing-fuse joint, too.

    Just for the uncomplicated joy of CL flight, it looks good. The weight might make it glide "a bit steeper."

    Enjoy!

    \\BEST\\LOU
    Lou Crane, Sierra Vista, AZ

  5. #5
    Hossfly's Avatar
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    RE: YS Muffler on a Series 21 McCoy .40 Black Head Engine


    ORIGINAL: GallopingGhostler

    I've got a Testors Series 21 McCoy .40 Black Head engine that I plan to put in a 42 inches (1067 mm) wingspan Sterling Kit S-46 Profile Hellcat. It has about the same proportions as the Sterling S-1 Ringmaster. I had a spare YS muffler, so I did a few modifications to make it work for the engine.
    XXXX

    I'll know more, when I test the engine, but I'm just wondering what you folks think.
    Well here are some facts and that which I THINK.

    First let me state several points. 1. I owned a Hobby Shop in Mt. Pospect, IL right on NW Highway, from 1970 to about '77 when I no longer needed the tax write-offs.
    2. At that time Iwas a pretty good CL Stunt Competitor, winning most of the CL Contests around Chicago Land for a number of years, not all but most.
    3. Testor's Corp. in Rockford, IL. who owned the McCoy line of engines at that time was, in 1971, about to introduce the line of engines that you have. After much plea bargaining I said OK and I will fly your new protype at the 1971 Glenview NAS NATS. I got a few flights on it (After removing my most faithful G.Aldrich rebuilt Super Tigre .40, a truly fantastic stunt engine.) I never got to really get the McCoy Series 21 (IIRC) 40 dialed in. However I had several fair to good flights the day before the Open Stunt. The first official and it looked like I had a golden touch. I could not believe it until I finished the 3rd loop in the 4-leaf clover and that SOB went into Rat Race LEAN for some 12 minutes total. No Pattern Points, No landing points and those other maneuver scores of 35+ did not get me anywhere. Next official I tweaked it a tad richer. Within about 6-7 laps it seemed it was drowning in fuel but I suppose that was my teardrops. [&o] Needless to say that I missed my last chance to ever qualify for the top 10 in the NATS CL Stunt.

    Afterwards I played with the McCoy .40 but never liked it. I did have very good results with a McCoy same series but a .19 in sport RC. However it wore out the Dyles ring after about 12+/- hours flying time.

    Your engine's insides are a direct replica of the of the K&B Series 71 (hope that is right #) which was a powerful & excellent FF engine. Won several major FF events with that engine on a Starduster to include 1968 Class C at the 4-Star annual event by Chicago's big FF club. However the timing for FF and Rat Race is very different than Scale and Stunt CL. As L.Crane stated if you just want to do strictly Sport you might have a ball. You might want a starter as the engine is strong and fast but doesn't like slow such as a stunter needs. It did not take mine long to quit wanting to finger start.

    Hope you the best with your project.
    Horrace Cain AMA L-93

    “Peace is the brief glorious moment in history when everyone stands around reloading.\" T. Jefferson

  6. #6
    GallopingGhostler's Avatar
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    RE: YS Muffler on a Series 21 McCoy .40 Black Head Engine

    Lou Crane and Horrace Cain, I appreciate your inputs. Yes, what you have to say has a lot of validity. I've been listening to inputs from the experienced CL fliers in the Ringmaster Brotherhood, who have given me excellent tips on what I am dealing with. They have advised me on kit wood versus hand selection, what to expect with results and etc.

    I am a relatively newcomer to large CL. I only had one large plane back in the 1970's, a Sterling P-51 Profile with Testors McCoy .19 Red Head. For me it was a sport flyer, but it was a world of difference from the half-A's that I flew. Now that I am older, I want to revisit CL again.

    (Edit - I guess my bad memory is catching up with me. Back in the 1990's I did revisit with a Sterling Ringmaster Junior and OS .15FP-S muffled engine. Just repaired it from toddler and storage rash. Boy I'm not thinking .... [&:] )

    This will be my first truly large CL airplane, and I gather it is not large by any comparison. I have a profile CL Supermarine Spitfire plan with a 50" wingspan, I'm thinking the .40 would probably be better off in it. However at this point I'm just looking to bore holes in the sky. If I like it, I may spend more time in doing scratch building of something that really stunts well and with the engine properly matched to the airframe.

    I do have one option, and that is to use the McCoy .19 Red Head instead in the Hellcat. I've been advised to run it full bore, go with something like a 9x5 prop. Watch the weight on the kit wood. Then, I am also at a 4,300 feet elevation.

    Meanwhile I'm completing a couple RC kits and ARF I started but not finished, repairing the damaged to flight worthiness. It gives me time to kick around ideas, before I gel on a building direction.

    Thanks again for the inputs.
    George Hostler
    Clovis MADS AMA Club, Vintage R/C Society (VRCS)
    And we know love by this, that He laid down His life for us, and we ought to lay down our lives for the brethren. 1 John 3:16


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