That looks like the dynamix carb on the Webra Race rear. A very interesting carb....
Just curious Dave, why use the 11x7 on any of these? Most of these engines work truly great on higher load and stretched pipe. Lower Rs, less fuel consumption and less wear and tear, more prop, same great handling. Calibration??
Hey Matt,
the 11x7 is not necessarily a prop of choice for flying. It is merely a reference prop that was used back in the 70's on lower powered 60's and it carried through into the 80's on the short stroke 61's. Later, as you know, folks started using step pitches as the engines became more powerful with 7.50 and 7.75" pitches being used. Otherwise, all you suggest holds true although for ballistic pattern, the short strokes unload more easily on lower pitched props and deliver higher horizontal speeds while sacrificing lugging power in up-lines.
I was actually rather surprised how "choked" the Speed/13 performed on higher load props and a standard NR pipe setup (i.e., un-lengthened). While high timed it is technically a long stroke engine and I expected it to do better on 11x10 and 11x11 props but it really seemed quite happy really hauling freight on light wood 11x8 props. But again, I emphasize this was all on a stock pipe setup which has been shown to be "short" for the larger props - as expected. In some conditions, it can perform better on a longer pipe even on the smaller props (i.e., 11x7) but I have yet to experiment with that myself. I just say this based on comments from Robert Fish in his recent installation in an EU-1A where he setup the engine with a longer than stock pipe arrangement.
Cheers, David