CG for Ringmaster S1

[Geoff Goodworth]

Where should a Ringmaster S1 balance? Mine balanced right on the LE with a Thunder Tiger GP 25 and OS E2030 muffler. I've tried a tongue muffler and the CG moved back about an inch but it's looking like 1–1 1/2" of lead may be required under the stabiliser. 

[Tim Wescott]

My plans show about 1 3/4" behind the leading edge.

How heavy is that engine?  Mine needed about half an ounce under the tail with an OS 20FP.

But remember that heavy is better than out of balance.

[Larry Fernandez]

My plans show about 1 3/4" behind the leading edge.

How heavy is that engine?  Mine needed about half an ounce under the tail with an OS 20FP.

But remember that heavy is better than out of balance.

I built a Ringmaster a few years back that weighed 19.5 oz. With an FP .15 , it balanced about 3/4 inch behind the leading edge. With a 4 inch bellcrank and VERY LITTLE deflection of that huge elevator, it was with out a doubt, the best flying Ringmaster I have ever flown. That is until a stiff breeze came up,
Then it was'nt that much fun to fly.

Larry, Buttafucco Stunt Team

[Dan McEntee]

   I would test fly it with the big muffler to feel it out. I've had and seen plenty of Ringmasters with forward balance points, especially to try and tame a twitchy turn or stall in the corner. The big thing with a Ringmaster is like Brett Buck mentioned somewhere else, and that is to start out with slow controls and don't go over board on elevator deflection. This helps avoid the dreaded stall on a hard corner and you can fine tune the balance as you go. If you are only going to sport fly the airplane, or only fly Old Time Stunt with it, then you can have a little bit of leeway with it. But a properly trimmed Ringmaster can fly a pretty respectable pattern in the right hands.
   Good luck and have fun,
    Dan McEntee

[Geoff Goodworth]

Thanks for the input guys.

Dan, The muffler option is worth using. The E-2030 muffler weighs 2.4 oz, a tongue weighs ~0.5 oz. I'm going to start with no lead and the tongue muffler and see how it works

Tim, the GP 25 is an FP 25 clone and weighs the same. The FP 20 is about 0.25 oz heavier due to the thicker liner. The model only weighs 17 oz without tank or engine so that may be a factor.

This is the GP 25 that I fitted with an LA 25 piston and liner so I have options of the GP 25, FP 20, FP 25, E-2030 muffler, tongue muffler. A few power and weight options.

Thanks again.

[John Cralley]

Geoff,

If it Balances on the leading edge, it is way nose heavy! An RM should balance between 1 and 2 inches aft of the leading edge. Go with the tongue muffler and bite the bullet with added tail weight. You can start with one inch and work back as you trim the model.

It should fly great once trimmed!

[James D. Hayes]

My S-1 is balanced 1.5" back from the leading edge, this is what the plan's call for.

Jim Hayes
AMA 988835

[Brett Buck]

My S-1 is balanced 1.5" back from the leading edge, this is what the plan's call for.

Jim Hayes
AMA 988835

   I would suggest this as nearly the maximum rear CG position. It's so tough to tame the overcontrolling that any further and the sensitivity to elevator position is so high that even tiny errors in alignment start causing inordinate problems. I have seen plenty of them with the CG near the back corner of the LE that flew fine. It certainly doesn't need to be that far aft to turn as well as it ever will.  Also, if you use the stock leadout position and a 1.5" cg you run a real chance of losing it completely on outside corners, particularly if you take out the rudder offset (which is a good idea if you have the leadouts and CG right).

   I know I sound like a broken record but the most critical trim adjustment is *making the elevator motion very slow* to avoid overcontrolling and stalling the wing.  With a 1.5" cg, a kit-weight airplane, and the typical Fox/McCoy 35, it wouldn't surprise me to find you can tolerate no more than +- 1/4"-3/8"(!) before it starts stalling. Lighter airplanes, or airplanes with better power (15FP, Veco 19, etc) can use more, but at no time can you ever get it like the classic "flipper" at +- 45. If you can keep the wing flying it is not a terrible airplane, but most of them with the teeny bellcranks and short elevator horns were frequently stalling just trying to fly them level.


 
    Brett

[Tim Wescott]

After all this talk, I'm going to try mine with a more forward CG, I think.  12-point loops would be fun if I were doing them on purpose, but when it happens because I got a bit hot on the handle, it's less so.

[Dan McEntee]

   Tim;
     Check your elevator horn length also, if loops happen way to fast for you. With a 3" bell crank, one inch long from hinge line to clevis is a good start. You can bolt on an aluminum piece to the existing horn with couple of 2-56 machine screws, and make enough holes to go out to 1 1/2" if need be. A similar airplane that needs a long horn is the Hanger-9 PT-19. I think I doubled the length of the stock horn and added 4 ounces of weight to the nose to tame that ill handling beast down. A handle with line spacing adjustment helps also.
    Good luck and have fun,
       Dan McEntee

[Tim Wescott]

Dan, I started with a Ringmaster from the Gabriele Macri' plans (http://controlline.org.uk/phpBB2/download.php?id=14119&sid=1dbdc88382a16ebeed784558422e580a), and set up the control system exactly as shown.  The plane was way too twitchy.  With the lines way together at the handle, the plane calmed down but felt very spongy.

So I put the longest horn extension on it that I could fit without digging furrows in the ground (plywood, but I'm going to replace it with aluminum or stainless).  That, plus handle spacing that's still a bit uncomfortably narrow makes the thing work.  When I do it over again, I'm going to drill a new hole in the bellcrank much closer to the pivot, or use a 4" bellcrank, or both.

[Dan McEntee]

   Tim;
     Somewhere in all my files is a layout someone did of a 4" bell crank, and it's horn movements, and over layed a 3" bell crank, and where you have to drill a hole to get similar movements. Some smaller wings just make it plane hard to get a 4" bell crank in side of it, and a 3" with a closer hole is easier. I have a lot of experience with Brett's "typical McCoy Redhead" set up and learned these lessons early on. I'm the proud recipient of the "Best Crash Award" from VSC from a crash of a pretty nice looking Ringmaster that I was going for the "most authentic look" on. All that authenticity just couldn't handle the altitude of Tucson and I pancaked it at the bottom of the third vertical eight! There were other crashes that year, but my parts went the farthest! The fuselage broke in half where they always break at and the nose went all the way over into the next circle and hit Ken Smith in the ankle!
    Good luck and have fun,
      Dan McEntee

[Brett Buck]

I have a lot of experience with Brett's "typical McCoy Redhead" set up and learned these lessons early on. I'm the proud recipient of the "Best Crash Award" from VSC from a crash of a pretty nice looking Ringmaster that I was going for the "most authentic look" on. All that authenticity just couldn't handle the altitude of Tucson and I pancaked it at the bottom of the third vertical eight! There were other crashes that year, but my parts went the farthest! The fuselage broke in half where they always break at and the nose went all the way over into the next circle and hit Ken Smith in the ankle!

   No one could say it wasn't authentic, that's pretty much how they fly when set up per the era. Fix it, and while no one is going to confuse it with an Impact, it's reasonably flyable.

   David has proven, multiple times, that no matter how light you make it and how you set it, it will fly great with a Veco 19, etc, as long as the engine keeps running. As Ted Fancher put it, once the engine quits, it turns back into a Ringmaster.

    Brett

     

[DanielGelinas]

Hi Guys,

How is the ringmaster with the FP 20? Is that too much engine for a light S-1?

Thanks,

-d

[Dan McEntee]

  No , it's no  too much engine. Between the prop, venturi size and needle setting, you can tune it to suit your comfort zone and lap time. This engine likes to be spun up and run at higher RPMs, so the usual starting prop is the APC 9-4. Start out with the lines a bit long maybe so you can trim them down if need be, but 60 feet from handle to fuselage ought to be in the neighborhood. Lots of threads over the years on different engine for the Ringmaster and you'll find all sorts of stuff if you use the search feature. read this whole thread close about control set up also and balance also.
   Good luck and have fun,
    Dan McEntee

[DanielGelinas]

Thanks Dan!
Yes, I read many S-1 threads over the years on the forums. What makes this one interesting is the topic of control throw and bellcrank.
I'll make the mods in my future S-1 build.
Regards,
-d

[Andrew Borgogna]

On the plans I have the CG is 1.75" from the leading edge.  I know this works because I just built one and it flew very well with that CG setting.
Andy

[Tim Wescott]

How is the ringmaster with the FP 20? Is that too much engine for a light S-1?

My S-1 is heavy (34 ounces) with an FP-20, and it flies very nicely on 60-foot lines (probably 62 feet handle to fuselage).

I'm playing with an OS-25S, which definitely can't handle such long lines -- it'll probably end up back on the FP-20 when I'm done messing around.

[Brett Buck]

Thanks Dan!
Yes, I read many S-1 threads over the years on the forums. What makes this one interesting is the topic of control throw and bellcrank.
I'll make the mods in my future S-1 build.
Regards,
-d

    And, just to be entirely clear, you need to get this with *slow* control response, short arm on the bellcrank or long elevator horn. Don't just limit the movement with a conventional control ratio. I think the long elevator horn (and as big a bellcrank as you can get) is better than abnormally short arm on the bellcrank, because it you only have 1/4" of movement to do a loop, the tolerance for *slop* is also very minimal. The slop is reduced by using longer arms on everything. Jim's airplane has ball links all around and that's a good way to go if you can keep the bellcrank from tilting on the shaft.

    Brett

[DanielGelinas]

Thanks for the Info Brett,

On another note, do three and a half inch bellcranks exist? And if they do, wouldn't they be a good compromise for the S-1?

-Dan

[Tim Wescott]

Bellcranks are dead easy to make if you want to go there.  There's a bazzilion pictures of them here.

I have a sheet of 1/8" phenolic that I whack bellcranks out of.  Brett makes them out of thin aluminum and balsa (with special connectors -- find a picture of one of his if you want to go there).  Or you can just make one out of thick aluminum sheet (I'm not sure how thick, but if you ask here someone will have an opinion).  Or you can get fancy and make one out of carbon fiber.  You could probably even make one out of plywood and make it work, but I wouldn't recommend that.

Just pull check it before you put it into the plane unless you like the idea of being surprised.

[Brett Buck]

Thanks for the Info Brett,

On another note, do three and a half inch bellcranks exist? And if they do, wouldn't they be a good compromise for the S-1?

-Dan

  They exist if you make one, or cut down a 4".

    Brett

[Garf]

   David has proven, multiple times, that no matter how light you make it and how you set it, it will fly great with a Veco 19, etc, as long as the engine keeps running. As Ted Fancher put it, once the engine quits, it turns back into a Ringmaster.

    Brett

     

I assume you are talking about the ball bearing Veco, not the plain bearing model.

[Brett Buck]

I assume you are talking about the ball bearing Veco, not the plain bearing model.

  I only know about the ball-bearing model.

   Brett

[Steve Fitton]

Thanks for the Info Brett,

On another note, do three and a half inch bellcranks exist? And if they do, wouldn't they be a good compromise for the S-1?

-Dan

I bought a 3.5" bellcrank from Tom Morris a few years ago.  I am sure he still makes them.

[john e. holliday]

How did we manage with the old Perfect and Veco 3 inch bellcranks?   

[DanielGelinas]

Doc, I get your drift but there is nothing wrong in making a good plane better.
-Dan

[Brett Buck]

How did we manage with the old Perfect and Veco 3 inch bellcranks?   

     We managed poorly, which is part of why the Ringmaster has such a reputation as a barking dog. And in fact many of them were built with Fox 2" bellcranks or similar and a stock elevator horn, which generates an elevator that acted more like a spoiler/speed brake than a control surface.

    Fix the controls, put on a good engine, and it's not going to win the NATs but you can fly decent full patterns with it (a pattern that was not invented until 8 years after the airplane was designed). The airplane was designed in an era where doing a loop was a pretty big deal for most people.

    Brett