My prop is a 74/43 with the 65. Static is 2150 rpm. 40-60 climb out runs at 2250. 70 mph hits 2300 rpm. Flat out in my doggy plane it will hit 100 at 2500 rpm. Usually cruise it at 85 mph and 2300 rpm. The airspeed is gps correct and tach has been optical checked accurate.
Dusty: Sounds like you are over pitched. Not all props will perform the same , even though the pitch and dia are the same. Generally wood will not give the same thrust or rpm as a metal due to the thicker profile which creates more drag.
I would class the 74/43 as a combo prop. It will do niether climb or cruise well, or if you are an optimist, it's reasonably good at both.
Ron
7AC Prop
props
Before you believe anything I say, check with two more people. If they agree, I must be right.
I got an e-mail from PropWorks, Inc today and the $2575 price includes a bolt kit. They state that the 74/43 is a "standard" prop and that McCauley does not offer a 74/41. So----it appears that the 74/43 is standard and that one would have to have it twisted to something less for a climb prop.
Still there are nothing but good reports from 7AC folks regarding the 74/43 pitch. It is hard to understand how the metal 74/43 could do better than the 72/42 wood. The only thing I think of is that the neck of the wood prop near the hub is thicker and is not as effective as the thinner metal. Must create more drag as one of the posts say.
Still there are nothing but good reports from 7AC folks regarding the 74/43 pitch. It is hard to understand how the metal 74/43 could do better than the 72/42 wood. The only thing I think of is that the neck of the wood prop near the hub is thicker and is not as effective as the thinner metal. Must create more drag as one of the posts say.
Ron,
I thought 2300rpm was redline for a 65hp??
gell,
You pretty much summed up the reason metal is more efficient. You have a very good point on windmilling, the wood prop sure will stop sooner.
I prefer wood even with the loss of efficiency. They just look classy and supposedly smooth out the engine somewhat. They are harder to prop because of the lesser density and flywheel effect but they are also easier on the fingers-so goods and bads for both.
Some metal prop/airframe combinations have rpm range restrictions because of harmful vibrations. The problem is that these restrictions are usually right in the middle of approach rpms, a real pain.
I thought 2300rpm was redline for a 65hp??
gell,
You pretty much summed up the reason metal is more efficient. You have a very good point on windmilling, the wood prop sure will stop sooner.
I prefer wood even with the loss of efficiency. They just look classy and supposedly smooth out the engine somewhat. They are harder to prop because of the lesser density and flywheel effect but they are also easier on the fingers-so goods and bads for both.
Some metal prop/airframe combinations have rpm range restrictions because of harmful vibrations. The problem is that these restrictions are usually right in the middle of approach rpms, a real pain.
Gus Causbie
Ash Flat, AR
N83564, 7AC-2235, A65-8
Ash Flat, AR
N83564, 7AC-2235, A65-8
prop
gusc: Having run the 65 close to 3000 rpm in gyro copters with minimal cooling, and never having one blow up, 2300 rpm is not going to hurt it in a Champ much. They are much more capable then you think.
Ron
Ron
Before you believe anything I say, check with two more people. If they agree, I must be right.
-
Oliver Barth
- Posts: 50
- Joined: Mon Jan 30, 2006 16:56
- Location: Mannheim, Germany
- Contact:
>My airplane is a 7 DC conv. with the C-85-8 and a McCauley 7043.
>I see: 2400 - 2450 static, 2450 - 2500 at 60mph during climb with 500-750 feet/min
>depending on OAT, cruise is 87-93 mph on 2400 rpm. (I think my airspeed indicator is some 3 -5 mph too fast)
>
>All figures are at ca. 1150 lbs, fuel consumption is 18,5 litres.
>
>It looks to me, that this prop is a climb prop. Take off performance is
>very good, especially yesterday at -5°C...
After all I read I would always opt for the standard prop and if climb is not good enough have it repitched to a finer pitch.
Oliver from Germany waiting for better weather
>I see: 2400 - 2450 static, 2450 - 2500 at 60mph during climb with 500-750 feet/min
>depending on OAT, cruise is 87-93 mph on 2400 rpm. (I think my airspeed indicator is some 3 -5 mph too fast)
>
>All figures are at ca. 1150 lbs, fuel consumption is 18,5 litres.
>
>It looks to me, that this prop is a climb prop. Take off performance is
>very good, especially yesterday at -5°C...
After all I read I would always opt for the standard prop and if climb is not good enough have it repitched to a finer pitch.
Oliver from Germany waiting for better weather