Since the post on the Ruffy with a Fox 35 got a good response, here's another:

I have a current model B40 in a Brodak Stinger for OTS. I have tried the TT 11x4.5 and APC 10.5x4.5. I have available a load of 10x5 and 10x6 wood including the RSM 10x6, plus APC 11x4. Any suggestions about what prop this motor wants on a model this size? The model is supposed to be flown fast with a clean 2-stoke run.

Since the post on the Ruffy with a Fox 35 got a good response, here's another:

I have a current model B40 in a Brodak Stinger for OTS. I have tried the TT 11x4.5 and APC 10.5x4.5. I have available a load of 10x5 and 10x6 wood including the RSM 10x6, plus APC 11x4. Any suggestions about what prop this motor wants on a model this size? The model is supposed to be flown fast with a clean 2-stoke run.

Hi
The cyclone 11 x 4.5  prop  works  very well on the  B-40

Randy

Hi Mike, actually I'm looking for a ceramic gila monster to mount on a rock I have in the front yard.  I hope to make it down for Golden State.  Prop wise - when in Sacramento I like the TT/Cyclone 11x4.5 but at Tucson or NM I go with the APC because I get faster lap times with that prop. This is necessary at the higher DA of those flying sites. Sorry 'bout the tail heavy condition, that's a tough one. 

Thanks Bob. Coming from "Mr. Stinger" that is most helpful. I am reluctant to admit that mine already weighs 41 oz (including 2 oz nose weight) and I don't see anywhere to put Buzz on a diet without major surgery. Still, I would hardly call its flight qualities mushy or sluggish; actually it was very quick and turns extremely tight, maybe 15 foot loops, way too tight for scored OTS competition. I really like the uniqueness of the model and will continue experimenting with it, maybe add another 2 oz and just accept it will be wiggly on the landing glide. Better still, build another one but change the construction/design of the fuse and tail, including use of RC motor mount (ie delete the ply formers and hardwood bearers entirely) and built up tail with lighter fuse sides and top. My local design team is already discussing the options!

Actually, I got the info from Dale when he called me about the Stinger. Apparently, it was the first one that he had seen in competition for a while. He mentioned lightness being important due to the thin wing - BUT, it's likely that yours flies well at the 41 ounce weight because of the extra power of the B-40. In any case, as long as it flies to your satisfaction, don't change anything! It's really quite a fine OTS bird and I'm surprised that there are not more seen at contests. I've only seen one besides my own.
My only complaint is the after run behavior. Mine does not like to glide. The slightest breeze will toss it around, making for some scary landings.

Bob Z.

We should probably move this to "OTS" so the other OTS enthusiasts will be aware of the discussion.

Doc, if you build the Brodak kit with stock (excellent) wood it probably will come out tail heavy like mine. The laser cut kit is really good with very good wood selection, but there is a lot of it. I would use thinner sheet for at least the rear fuse and a built up tail section as Bob Z describes. I covered mine with silkspan and used cloth hinges and an all dope finish to stick with the vintage theme, but if doing it again I would use lighter materials and maybe Ultracote to cover. The wing is a D-box structure so doesn't need a lot of "stressed skin" strength from the covering.

I moved the engine as far forward as the bearers would allow because I could sense a W&B problem coming. Maybe we could (heresy) extend the nose by an inch. Wonder if Dale Kirn ever built one like that in the OTS period that would legitimize doing so?

Actually, another member of my club has a Brodak kit nearly framed up. He has seen mine fly and is aware now of the balance issue. We will discuss changes on his. On mine I intend to just add some weight to get it to glide safely and go with that. I too have had some scary glides. Oh, and a free-flight over the top last Sunday in the wind.

While still on the subject of design changes, the soldered-together forked pushrod to the two elevators imparted a force tending to push the elevators to full "down" at rest. Not good. So after fully built I opened the belly sheeting to re-desgn the pushrods with a pivoting ball link where the pushrods split to the elevators. Better but still a little unnerving. If starting from a kit I would use two independent carbon rod pushrods (Tom Morris) from either the bellcrank or maybe a slave pivot at the wing TE as if it was a flapped model but without the flaps. This could also reduce the elevator movement. This model needs very little elevator movement.

All in all a very cool plane that should be built by more people. A half-dozen at VSC would be a sight to see.