I am building the Ringmaster to get in on the Ringmaster Day. I built one 50 years ago what are some tips to have a good flight with it. I am planning on a Fox 35 in keeping with the nostalgic theme...….

John,
I have a Ringmaster that I built 20 plus years ago and it is still solid and winning it's share of contests. Things that worked: run the motor mounts back past the leading edge, mine go 1" past. Use 1/16" plywood, run it back past the leading edge and 3/4" pass the end of the motor mounts (assuming you run the mounts past the wing leading edge). Use long setting epoxy to install the fuse/wing joint. Use 1/2oz/sqyd. fiberglass to reinforce the fuse/wing joint 1 1/2" pass the leading edge apply with long set epoxy.

Controls: Use a 4" bellcrank with cable leadout.  Set the pushrod up on the inside hole with a medium size tail horn. Controls should deflect no more than 25 degrees ish. Use adjustable leadout guide, initial setup center of lines exit 3/8" behind the CG. CG should be set about 15% back from the leading edge at the fuse/wing joint. Use a 1/8" diameter carbon fiber push rod.

Tank: Get a snub nose uniflow (no pressure) 3 3/4 - 4 oz tank, mount it to have the back corner kicked out at least 1/4. Use adjustable slide tab mounts (I use two on top, one on the bottom of the tank with 1/4" slots, Brodak has these made up).  Initial setting for the Fox 35 is to have the tank pickup tube lined up to the top first fin on the head (about 1/8" above the glow plug), the Fox likes this for even upright and inverted consistent runs. Most important is to run the uniflow vent line to a free air stream vent tab off the back engine bolt (see picture). This is the single thing that gets the Fox to hold a consistent setting, you take a 3/16" wide strip of shim brass or tin and make a half loop at the end, solder a piece of 3/32" tubing to it, set the height to be 1/4" above the fuse, drill a hole and install it under the head of the back engine mount bolt. Connect the uniflow vent from the tank with fuel tube.

Engine: Run simple fuel 10% nitro, 27% oil (50/50 castor/syn). I get 10% Brodak all castor 29% and 10% Brodak 22% syn and mix equal parts, has worked very well in my Fox). I like to use a Randy Smith FoxPA needle valve, it has the same reduced center diameter as the Fox NVA without the leaks, gives a reliable run. If you use the FoxNVA make sure to use a piece of fuel tubing between the indexing wheel and spraybar to seal the threads. With the FoxNVA check to make sure that the holes are both across the venturi and set so when you look straight down the bore of the venturi you can't see either of them.

Prop/muffler: As long as the uniflow vent is in the free air stream the Fox 35 will turn a 10x6 prop (it really likes the RMS prop) and run a muffler with no overheating problems (as long as you use good fuel, ie no RC stuff). Set the engine to run a rich 2 cycle and have fun. If you develop the burb on the outside corners let us know and we can send the stick in the bypass mod info.

Best,   DennisT

I am building the Ringmaster to get in on the Ringmaster Day. I built one 50 years ago what are some tips to have a good flight with it. I am planning on a Fox 35 in keeping with the nostalgic theme...….

    Far and away the most important thing is what Doc mentioned - make sure that the control rates are *slow*, that is, that the elevator horn is very long so that full handle movement only gives you a relatively small deflection of the elevator, like maybe 3/4" each way with your hand moved all the way to "up" or "down".   For vintage engines you can tolerate less movement, for modern engines or electric, you can tolerate more movement, but the stock arrangement, where it act like a +-45 degree flipper is completely unacceptable, and why the airplane is considered such a dog. Fix that, and it is at least possible to fly reliably.

    Pop the elevator up to 45 degrees or more, and that wing will stall almost immediately. Almost all of them, built from the kit, and flown with Hot Rock or similar large handles, were nearly impossible to control without stalling, which is why they tended to fly so poorly - it would just progress from stall to stall.

    A modern engine (like a 15FP, 20FP, Veco 19, etc) helps tremendously, too, but, not nearly as much as making sure the elevator moves *slowly*. A bigger vintage engine is not nearly as beneficial as a smaller modern engine.

     Saving weight is much less important, although it helps, but carries the danger of overdoing it, and having the wing break off.

    Brett