I am getting near to working on a couple of converted to radio Old-timers. These were originally built free flight too. I have the late model ratios from booklets, but this I think is different due to speeds and age.


The A/C have quite large area hozstabs and fins shown. Usually the areas are in the 150-250 SI area, and the main wing is in the 1200 s.i. area range. Some of the plans for A/C show the stab as lifting also. But what ratio of the overall areas ought to be set asside for elevators and for rudders? The modern booklets give a ratio, based upon main wing area, moments etc. But this always proves too small. Mainly I think due to the slow speeds here, and the piots reaction time. The old radio booklets indicate a ratio of 20% for rudder based upon overall for the fin. Then the Hoz-stab is to be about 28 to 33% of main wing area, etc.

So, what do you figure is a good ratio? I know already they use a lot of deflection in the elevators, just to get them into the wind.

Wm.

Well, if you opt for the design correct CG location then you can easily get away with 25'ish % for the elevator. These models only get doggy in pitch when good intended builders insist on using forward "normal" CG locations on models that have more than enough tail volume coefficient to work with the CG farther back. The online CG calculators will give you the real goods on this.

On my larger size sparky.60 designs I've been very happy with around 40% area for the rudder with these running about 35 degreed of deflection. They get a little snappy when flying faster but for the slow power and glide portions this size gives a response much like a nice Gentle Lady glider. And that's very nice indeed. Both of the models I've done this with kept the original dihedral angles.

On smaller size models go with a LOT less rudder area. Or be prepared to hold the rudder deflection angles down a lot. Especially if you go for the original dihedral angles. If you go with less then you'll want the bigger size split. I had a Miss Tiny 1/2A Texaco model with a 40% rudder. I had to reduce the total throw to about 1/4 inch, or somewhere around 10 degrees each side of neutral. And even at this at higher speeds it would require gentle control inputs or it would stunt itself into tossing its kidney out.

My Modelcraft Pacific Ace got damaged in tail feathers. Am going to construct new ones for it now. I used to fly it OK with a very small "Trim tab" sized aileron, .19 glow power, and used maybe 3/8" deflection on it. Too much control, but likewise used a good 1/2 inch on the rudder and it was near minimal control.

Wm.