Trimming a Ringmster

[Lyle Spiegel]

Would like recommendation - how much elevator deflection is needed/ recommended?
Where should the CG be located>
Engine options: OS35S  or FP20?

[Dan McEntee]

  Elevator deflection in the 20 to 25 degree range. Balance point near the high point of the air foil. Either engine will do fine. OS MAX.35S for old school run, the FP-20 for more modern high RPM type run.
  Type at you later,
  Dan McEntee

[Brett Buck]

  Elevator deflection in the 20 to 25 degree range. Balance point near the high point of the air foil. Either engine will do fine. OS MAX.35S for old school run, the FP-20 for more modern high RPM type run.
  Type at you later,
  Dan McEntee

   20-25 degrees  is probably too much, and in any case, the total travel is less important than the rate being very very slow. That is, full hand motion to get maybe +-20 degrees, not the normal speed and a block or limits. It should also be adjustable so you can speed it up until you can *just* stall it with full hand motion, or slow it down until you can *just* stall it with full hand motion.

    The rate/"travel" will need to be much less if you use a vintage engine, because it will be much more prone to stalling. 20FP is going to go like a bat out of hell when it is set correctly, under 4 seconds/lap, but it's going to be much more difficult to stall.

    Please refer to very extensive previous threads about this, there's been a good half million of these things made, there is not a lot new about it.

    Brett

     

[Dan Berry]

I would bet that the best ever Ringmaster has no more than 15 degrees available and it likely balances about 15%. I know that it has a Brodak 25.  Almost certain it’s ac9/4 APC prop. 

[Lyle Spiegel]

Thx everyone. Brett, I will search forum for the many older posts. I'm not looking for a bat out of hell. The Ring I want to trim is a swap meet purchase. This is first Ring I've flown since my only other Ring that I built when starting in this hobby as a 14 year old.  Back then, didnt know much about trim other than CG balance near the leading edge. i was happy that it flew!  I destroyed it trying to learn inside loops. The current Ring has way more than 20-25 degrees. I can't be certain of how Bcrank is set up. Hopefully 3 inch using inner hole. Push rod is positioned on outer most hole #4  on an RC style horn. I use 3  1/2 inch handle spacing.
To move the horn higher I'm thinking of adding one or two plywood shims under the mounting surface.
 If raising the horn doesn't cut down deflection, next step is to add stops. 

[Paul Smith]

Stops on the airplane are always a BAD idea.  You end up hanging by one line and putting all the stress on the stop.

It's best to get rid of excess travel with a smaller handle and/or a taller control horn.

[Ken Culbertson]

Stops on the airplane are always a BAD idea.  You end up hanging by one line and putting all the stress on the stop.

It's best to get rid of excess travel with a smaller handle and/or a taller control horn.

I would like to disagree (gently!).  Allowing a bellcrank arm to rotate more than 90 degrees in one direction is dangerous.  There are places where the placement of the bellcrank and the leadouts will permit that with no stops.  The amount of effective movement past 60 degrees is almost zero and there is a strong likelihood you have hit "the wall" and are effectively on one line already.  Where it matters is on slack line situations where you loose tension and regain it rapidly.  If the bellcrank can over center, it will, and you will have about .5 seconds to figure out what happened and it won't matter what your handle settings are or how tall your flap horn is. I simply make the spar cutout on the inboard side shorter than the bellcrank arm.  Personally, I like it to stop the movement at about 60-70 degrees.  I also use logarithmic controls and allowing them to "bottom out" puts a lot of stress on the control box.  Without "stops" all of the force of a one line situation is on the flap horn and hinges.  I have seen too many planes where the obsession with tight hinge lines has made flap movement the limiting factor in the control system.   So my advice is to use "stops" if your furthest forward or rear leadout position makes it *possible* to over center the bellcrank.  You might be surprised how many will with some of the extreme positions.

When you design the plane check if the aft leadout can be ahead of the bellcrank pivot with the leadouts full forward or the forward one behind the bellcrank pivot with the leadouts full aft.  If that is the case you *can* over center.  I missed the warning signs on one of my recent planes.  On the top of the hourglass, where line tension is at a low point I was over turning severely and couldn't figure out why.  A few flights later I found out why when I forgot to tighten my lines on a last minute trim flight to test a new leadout position.  The plane flipped on takeoff and broke off the nose.

Ken

[Dan McEntee]

Thx everyone. Brett, I will search forum for the many older posts. I'm not looking for a bat out of hell. The Ring I want to trim is a swap meet purchase. This is first Ring I've flown since my only other Ring that I built when starting in this hobby as a 14 year old.  Back then, didnt know much about trim other than CG balance near the leading edge. i was happy that it flew!  I destroyed it trying to learn inside loops. The current Ring has way more than 20-25 degrees. I can't be certain of how Bcrank is set up. Hopefully 3 inch using inner hole. Push rod is positioned on outer most hole #4  on an RC style horn. I use 3  1/2 inch handle spacing.
To move the horn higher I'm thinking of adding one or two plywood shims under the mounting surface.
 If raising the horn doesn't cut down deflection, next step is to add stops.

   I have rescued several Ringmasters, some with the originally installed 2" perfect bell crank. The elevator horn length needs to be increased to anywhere from 1" to 1 1/4" from the surface to slow down the speed along with the narrow line spacing you now have, which may have to get a little closer to 3", but the airplanes do fly much better. Make yourself a new control horn if you have to. I have even just bolted on a 1/4" wide strip of metal to the existing horn to get to where I wanted to go. I had to recover the oldest one after it got caught in a hail storm, and in that process I was able to verify it was a kit built Ringmaster with 2" bell crank and was assembled with Ambroid glue, of which all the joints were still intact and solid. Of the three Ringmasters I had out last weekend, I think it's the best flying of the three, and I'm working on bringing the other two up to it's level of trim. These are all in the 30 ounce weight range.
  Type at you later,
   Dan McEntee

[Dave Moritz]

Am going to follow Brett’s advice on a pair of Cox-powered Baby Flite Streaks. I’ve taken a teen boy under my wing and he’s developing an interest in C/L flying. The BFSs are very twitchy, so I’ll go with longer control horns and an adjustable handle.

Thanks for the discussion, gents. My Ringmaster will also benefit from the good words here.

Dave Mo…

PS: The lad’s first flight on a little Skyray went (almost) flawlessly. He didn’t crash and got the feel of it in a lap or so! I write “almost” because I hadn’t told him how to land, figuring that he’d crash before fuel ran out.

D…

[Dan McEntee]

Am going to follow Brett’s advice on a pair of Cox-powered Baby Flite Streaks. I’ve taken a teen boy under my wing and he’s developing an interest in C/L flying. The BFSs are very twitchy, so I’ll go with longer control horns and an adjustable handle.

Thanks for the discussion, gents. My Ringmaster will also benefit from the good words here.

Dave Mo…

PS: The lad’s first flight on a little Skyray went (almost) flawlessly. He didn’t crash and got the feel of it in a lap or so! I write “almost” because I hadn’t told him how to land, figuring that he’d crash before fuel ran out.

D…

    Get those Cox engines humming and let the lines out to beyond 30 feet. Lap times will be slower and the slower controls will help a lot. i fly a baby Clown ARF on lines over 40 feet with a Medallion .049 on the nose and it could probably go out a bit farther. The new , lighter fishing line for flying lines help a lot also.
  Type at you later,
   Dan McEntee

[Dave Moritz]

Thanks, Dan for confirming our setup. These are powered with dual-ported Golden Bees, and we are using 42 feet of fishing line. Glad to hear that you agree with the slower controls that I've got in mind.

Dave Mo...