Kyle Boatright
Well Known Member
Aymar Demuth went out when the owner died.
Van's Air Force
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Prop delamination, RV-6 stuck on cross country, HELP!
- Thread starter kismet
- Start date
Aymar Demuth went out when the owner died.
rv7charlie
Well Known Member
You guys are *young*. 
Bernie Warnke was KING long before those guys made a name for themselves. In fact, I'm pretty sure one of them was Bernie's apprentice before he died. If you ask Catto, I bet he'd say that Bernie was the greatest carver ever.
I think that's the reason all these brands are disappearing; the owner is also the craftsman, and when he (or she, in the case of Bernie's daughter) retires or dies, the company goes with him.
Charlie
Bernie Warnke was KING long before those guys made a name for themselves. In fact, I'm pretty sure one of them was Bernie's apprentice before he died. If you ask Catto, I bet he'd say that Bernie was the greatest carver ever.I think that's the reason all these brands are disappearing; the owner is also the craftsman, and when he (or she, in the case of Bernie's daughter) retires or dies, the company goes with him.
Charlie
You guys are *young*.
I think that's the reason all these brands are disappearing; the owner is also the craftsman, and when he (or she, in the case of Bernie's daughter) retires or dies, the company goes with him.
Also Colin Walker, Ted Hendricks, etc. etc...
Boyd Birchler
Well Known Member
Of the fixed pitch wood props I have flown behind the Pacesetter was absolutely the best. It got off the ground nearly as well as a CS and cruised quite well. Once you get a spinner on, it will load the blades better and give you a bit more performance.
gmcjetpilot
Well Known Member
As other said or implied these prop makers were one man shows, hand made
props by an individual, not a corporation, typically an older gentlemen who
retired and/or passed away.
The other factor was big corporations entering the market, providing props
specifically for experimental aircraft,Whirlwind, Harttzel, Sensenich. At one
point experimental aircraft were persona non grata with the big legacy companies.
Then they realized more experimental amateur built planes were being certified
every year than certified piston prop planes.
gmcjetpilot
Well Known Member
Not doubting what you are saying Sam; maybe you have some personal experience,
but the spinner is not that super critical for one reason. The blade shape near the hub,
just outside the spinner, is a big hunk, not aerodynamic at all, spinner or no spinner.
As he has found the spinner made little difference in performance. There is little to no
thrust coming from the root of the prop blade.
This blunt prop blade root shape just beats the air to death, and most of the
air entering the inlet is at the outboard edges, where the prop blade airfoil
is develop. Even with a spinner, you can block the inner edges of cowl inlet
an inch or two, and it will make little to difference in cooling. The inner part
of the inlet is basically wasted and even detrimental, as it allows reverse air flow.
The above is not opinion but shown in the Mississippi State 1970's cooling of
horizontal cooled aircraft engine studies.
https://ntrs.nasa.gov/search.jsp?R=19810013485
From this study Lopresti came up with his STC's to retrofit cowls with round
engine cooling inlets on Mooney's and other certified planes. Experimental
kit plane designers also caught on, like Lancair and others who followed suit.
Why did Van not follow suit. The standard design works fine if quality of
workmanship is high. But that extra few MPH can be had with reduced
cooling drag (cooling that does no cooling but causes needless drag).
Look at Reno or Dave Anders... there is science behind this. You don't
get a 244 MPH RV-4 with the standard cooling. Of course he has a monster
engine, but cooling drag is a big factor in speed.
Notice the round inlets are placed away from the prop blade root and spinner...
Look at the Sam James cowl... The inner few inches of cowl near the spinner,
are blank, not open.
The ROUND inlet is only part of the secret. Cooling inlet must have not only
proper size (area), it must have good placement (away from spinner), proper inlet
radius AND the inlet has an internal airfoil shape. I knew guy at airport who cut crude
round inlets into his Grumman Yankee's cowl (yes not legal) with blunt edges and no
sealing to a cooling pressure plenum. He cooked his engine big time... He was kind
of an idiot and would listen to me. I was not happy he cooked his engine, but told
him not to do it.
Most important the "round inlet" must be sealed to a cooling plenum that
does not leak past the cylinders without doing cooling. Van's set up is good,
with soft seals rubbing the cowl. However if builder does not seal the inlet to
the cowl well it will cause more drag. I have seen some clever talaanted builders
keep the semi rectangular inlet and seal it to a pressure plenum. That helps,
but again that inner edge is doing you no favors and air actually comes back out.
This low speed air mixes with high speed air and causes interference drag. Again
we are talking a few MPH. The spinner is a small factor, but not super critical.
However on a jet engine the fan spinner is so critical any damage to it grounds the
airplane. The turbine blades are airfoil shaped right at root. They are also made of
titanium and exotic nickle metal alloys. They are held into the hub by slotted "tree".
Why don't prop manufactures make an airfoil shape right at hub? Well strength.
With wood props it's just not possible. Metal constant speed props the shank or
blade root has to be round. Metal fixed pitch is probably the best at getting to
an airfoil shape closest to hub. Also it matters little on a tractor engine prop plane,
as the cowl is indeed blocking a lot of the thrust. However it does effect the cooling.
Therefore the spinner DOES MATTER, but not that much. Spinner is better for looks.
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I agree that lack of a spinner probably doesn't have a significant effect on speed performance but I bet it does on cooling performance. This may not be a factor this time of year in regions with much cooler temps but it certainly could in other situations.
The as designed engine cooling system works because of a pressure delta between the top of the engine and the lower cowl area. With no spinner or back plate installed, the center nose portion of the cowl has been converted to a large inlet routing air directly into the lower portion of the cowl. This likely has a very measurable influence on the pressure delta across the cylinders. It may even have some influence on how clean the airflow is going into each cooling air inlet, further influencing the problem. Successful flight may have been because of cool temperatures. If the airplane gets flown towards warmer temps, CHT's and OT may become a problem.
