Climb prop 7651 opinions

[buzzlatka]

I know I know this is the 100th thread on this. We are buying a overhauled 7651 from Leading edge in MT. He has overhauled it and is going to paint it before yellow tag.

Question.
1. Should I and Legally can I pitch it down to a 49 or 50 before paint.

2. Am I really going to notice a difference in t/o and climb with the 51 over the 53? Or am I just going to lose knots.

3. Has anyone done the switch from a 53 to a 51 lately and remember the results.

4. Should I just do what AR dave says and buy the seaplane prop

The reason we are going with the 7651 over our current 7653 is that we are looking for a little more climb to get out of our very short strip. I am a chicken and don't want to sacrafice to much cruise. I looked at the seaplane prop but decided I couldn't lose that much cruise for a majority of my flying.

My expectaions for a 51 are that I will lose 4 knots and gain about 75 static rpm.

Steve

[Bruce Fenstermacher]

I know I know this is the 100th thread on this. We are buying a overhauled 7651 from Leading edge in MT. He has overhauled it and is going to paint it before yellow tag.

Question.
1. Should I and Legally can I pitch it down to a 49 or 50 before paint.

First a prop can be repitched without marring the paint so that should not stop you from having it done after it's painted. I've repitched two different props on 3 occasions and you wouldn't know it looking at the paint.

The limit in pitch is not the pitch itself but the static RPM that is archived. On other words as long as your rpm is in static range per the TCDS it doesn't matter what the pitch is. Chances are though that if you flatten the pitch more that 51 you will be able to exceed the static RPM range. How do you think they came up with 51? Because a 51 pitch resulted in the max static RPM they where looking for.

2. Am I really going to notice a difference in t/o and climb with the 51 over the 53? Or am I just going to lose knots.

Yes you will notice a difference in climb and your roll should be shorter and yes you will go slower at cruise with the same RPM as you use to use.

3. Has anyone done the switch from a 53 to a 51 lately and remember the results.

4. Should I just do what AR dave says and buy the seaplane prop

The reason we are going with the 7651 over our current 7653 is that we are looking for a little more climb to get out of our very short strip. I am a chicken and don't want to sacrafice to much cruise. I looked at the seaplane prop but decided I couldn't lose that much cruise for a majority of my flying.

By seaplane prop do you mean a DM7649 or do you mean the 8043 (or 42) that ARDave has. They are two completely different props and the results will not be close. It seems you are worried about going slower. In that case you don't want the 804x prop and like I said you will probably exceed the static rpm limits for a land plane with the DM7649 and you won't like the slower speed either. BTW the 804x prop ARDave has has to be approved by some source and in this case I believe it is an STC. That STC will have new static limits ans part of its approval.

My expectaions for a 51 are that I will lose 4 knots and gain about 75 static rpm.

I think your guess is pretty close but would expect 4 MPH not knots difference.

[Showboatsix]

Which do you want? Vertical performance, or horizontal Performance.
It is not feasible to have both unless you have a constant speed prop. I have flown behind the 7651 for about 16 years, and for me since I would rather be able to clear the 50 ft obstacle than hit it, I recommend the climb prop. Western Propeller told me that the FAA/Prop tolerance is + or - 10% of a selected pitch. I chose the 51" -10%, static is just below the limit, and full throttle level flight it will just make 2700 RPM. Now as to speed I generally see 105 MPH level flight @ 2450RPM, a little less at 2400RPM but not much. I have found that if I climb up about 200ft above elected cruise altitude and then descend down to cruise altitude, I get into a better step for the plane's attitude and can see about 109-112 by doing that.

But remember this..... SPEED and 170/172 ARE NOT USED IN THE SAME SENTENCE!

I have close to 2500 hrs logged in my log book... and no "miles per hour".... regardless how fast or slow you fly.....it still takes 60 minutes to make an hour to log!
Dean

56 C-172 Taildragger

[Jr.CubBuilder]

I went from a 76/49 pitch that was on my plane when I bought it, then had it repitched to a 76/51. The 76/49 got off the ground and climbed a lot better, but it was stupid slow 85mph indicated was a realistic number for cruise and over 7000' it just didn't have enough bite. The re-pitch to 76/51 dropped the RPMs by about 200 on take off, cruise was around 100mph. My wings aren't rigged for best speed so you might see a bit more speed. I'd look at the 80" seaplane prop and see if you can talk to some people that are running it, the STC used to be held by Kenmore Air and it was only $100 but the prop itself was spendy. From what I've heard the 80" will give you better climb than a 76/51 and still cruise just over 100, but talk to someone who is using it.

[buzzlatka]

I ended up buying the 7651 prop.

Just like everyone says you can only get so much power out of the c-145. We looked hard and almost bought a 80 inch with the kenmoore stc. Now I am glad we didn't. I did not want to lose that much top end speed. I am hoping the 51 will give me a little more power on the take off and climb with out TOO BIG of a hit on speed.

The good thing is that we keep good records on performance and with the 2 props I will be able to post some good actual data between the 51 and 53 pitch props.

If we don't like the 51 you we will just put the 53 back on and sell it.