Originally Posted by
aspeed
Hard to believe an 8-6 prop on a .15 works. Must have been a strong motor for it's day.
This September 1967 MAN article
http://www.sceptreflight.net/Model%2...-III%20TV.html stated:
Originally Posted by Peter Chinn
As regards power, the 15-III TV did not put out the highest horsepower of any .15 R/C engine we have tested to date, but it was one of the best nevertheless. With the muffler fitted, maximum power was developed at just over 12,000 rpm where an output of nearly 0.23 bhp was indicated. When the muffler was removed, power went up to over 0.25 bhp at approximately 12,700 rpm. Typical prop speeds, without muffler fitted, included 8500 on a 10x4 Tornado nylon, 10,000 on a 9x4 Top-Flite nylon, 11,500 on an 8x6 Power-Prop, 12,600 on an 8x4 Top-Flite nylon and 14,100 on an 8x3-1/2 Top-Flite wood. Fitting the muffler reduced these figures by 100-500 rpm but, as we have previously remarked, slightly helped idle.
Not all props are alike; I found that unmuffled with a Masters 8x6 it provided the best thrust on 15% nitro and was able to keep up with the unmuffled OS Max .15FP-S with same series Masters 8x4 on the same fuel. No doubt it would have done better with the wider CL venturi.
This Aeromodeller article
http://www.sceptreflight.net/Model%2...-III%20CL.html stated:
Originally Posted by Peter Chinn
Only when props smaller than 8x4 were tried, did the Enya's starting deteriorate and, since such a prop size would take r.p.m. beyond the b.h.p. peaking speed, this is of academic interest only.
Basically as stated, there is no advantage to going to props smaller than 8x4. I found a similar truth with the smaller Enya 09-III TV. Peter similarly stated there was no advantage to using props smaller than 7x4. I found it produced thrust competitive with plain bearing sport Schneurle engines on a Top Flite 7x6 wood prop. The lower inertia wood prop also made the smaller engine easier starting by hand.