Doesn't surprise me the specs don't show much diff.
I switched from FP to C/S in my BD4 and honestly wasn't impressed and never really thought it was worth the money.
Climb rate for instance isn't about just the prop, it is determined by Ps (specific excess power) for a given airspeed, which is a function of the THP (thrust horse power) delivered by the prop and the Pr (power required) at that airspeed. As you know power required depends on a lot of factors. All things being equal and assuming most -8's are closely configured the biggest factors will be Gross weight and CG. Of course somebody who has gone to extreme measures to reduce the drag polar will have a better climb rate
So in a nut shell - take the same plane, under similar environmental test conditions and fly an ACCURATE performance profile in climb and cruise with both a FP and C/S I don't think you'll see significant differences in performance. But the word SIGNIFICANT means different things to different people.
If it were ALL about maximizing performance the the real discussion shouldn't be FP vs C/S but Recip vs Gas Turbine!
If you live & fly in the flat lands at sea-level, or fly BD-4's, your thoughts may vary from mine.
L.Adamson --- RV6A Lyc 0360, Hartzell C/S
Since I am on the budget plan for owning an airplane, I will put the extra $6k in avgas and still have a blast! I can fly along with a C/S RV with ease, yeah it might pull away slightly in the climb but I will never loose sight of it. Slowing a F/P RV down is easy if you use the correct technique and all the tools at your disposal.
Your oft-repeated partisan bias is well known among members of this forum. At long last Larry, you finally seem willing to concede at least one highly significant point. Good on you. Not everybody flies out of a high altitude environment. Around much, if not most of the country elevations are not nearly as extreme as the environment you operate from. But when anyone is given to issuing blanket statements, in this case a C/S is superior to a F/P without qualifying it in any way, they are bound to be challenged. One more thing, at my airport with its pattern altitude of 1400' MSL, I have ZERO trouble slowing down my Sensenich equipped RV from cruise speed to landing speed while in the pattern. Those RV'ers who operate out of a similar environment yet *think* one has to start slowing down a F/P equipped RV some miles from the airport may benefit from some additional dual instruction.
If all I wanted was 1000'/minute I could fly a spam can.
Oh really......
Personally, I'd been flying C/S props before I had the notion to build an RV. I knew the difference then, and the difference now. So being polite, I'll put it is way, ...around here................it is NOT well proven that there just isn't much of a performace gain between F/P & C/S.
One of my subtle points in the discussion of Ps was that you CANNOT use two different airplanes to make the analysis..this is a fundamental Flight Test process foul. If all -8's were built to the same standard and configuration then yes it would be ok.. but this is not the case. One of the benefits of the FP is in most cases is it will be over 30lbs lighter, maybe not true for some of the lighter composite c/s props tho?. Does anyone have Climb Rate vs. Gross Weight and CG data?
The other thing I hear a lot of is the efficiency gained with a C/S prop..yet I can never get anyone to agree what efficiency they are talking about. I had the Hartzel software while I was doin a lot of test work that predicted the prop efficiency of the 76666 blade (I think thats the number??)..and depending on the DA, RPM, and A/S and prop diameter the efficiency (in this case the ratio of THP/SHP) varied from as low as 78% to as high as 86%. Comparing that with some of the more common FP props that often have efficiencies in the mid/low 80's you can see that depending on the flight regime the FP can and will have a higher efficiency.
Efficiency can be measured however you choose to measure it..
How about MPH/Fuel Rate? Or MPH/Total Acquisition cost?
Oooh I like that one... So if my max speed is say 200MPH with a FP and it cost me $50,000 total to "build" my plane I have an efficiency of .4% (200/50,000) *100)
If I put a C/S on and I now get 210MPH at $56000 my efficiency is .375% !
Its not hard to devise definitions to PROVE your point
Also, if I match my my airplane, engine, FP climb prop correctly it will do as well as an C/S in climb...but will certainly suffer in cruise.
But you might say yeah but I get to my destination faster..ok so maybe there is a benefit over the long haul for fuel savings. But with a 30lbs lighter plane I might be able to bring ALL of my wife's shoes, purses and hair products with me saving me that money at the destination end of the trip!!
BTW I had a guy with a 200hp RV-8 challenge me to a race in my 180hp BD-4. I told him no way he could possibly win and I was right...I kicked his butt!!! Actually he backed out...which is an even better win.
I told him the race was from St. Mary's, MD (2W6) to Ocean City straight line of about 70 miles...his plane cruised at 220 Mph mine was 180 Mph. He backed out cause the race was to see who could get their family of 4 from St. Marys to Ocean city with all their beach gear in the quickest time..HA!
Even SPEED needs to be defined to show one is "faster" than the other...
Honestly...this is not an effort to prove one is better than another...because I KNOW it cannot be done..because the criteria (as I've just shown above) can be tailored to fit your personal objectives... This is just for fun
But to make it really fun why don't those of you with flying RV-8 create a CAFE style fly-off
Oh really......
Personally, I'd been flying C/S props before I had the notion to build an RV. I knew the difference then, and the difference now. So being polite, I'll put it is way, ...around here................it is NOT well proven that there just isn't much of a performace gain between F/P & C/S.
One of my subtle points in the discussion of Ps was that you CANNOT use two different airplanes to make the analysis..this is a fundamental Flight Test process foul. If all -8's were built to the same standard and configuration then yes it would be ok.. but this is not the case. One of the benefits of the FP is in most cases is it will be over 30lbs lighter, maybe not true for some of the lighter composite c/s props tho?. Does anyone have Climb Rate vs. Gross Weight and CG data?
The other thing I hear a lot of is the efficiency gained with a C/S prop..yet I can never get anyone to agree what efficiency they are talking about. I had the Hartzel software while I was doin a lot of test work that predicted the prop efficiency of the 76666 blade (I think thats the number??)..and depending on the DA, RPM, and A/S and prop diameter the efficiency (in this case the ratio of THP/SHP) varied from as low as 78% to as high as 86%. Comparing that with some of the more common FP props that often have efficiencies in the mid/low 80's you can see that depending on the flight regime the FP can and will have a higher efficiency.
Efficiency can be measured however you choose to measure it..
How about MPH/Fuel Rate? Or MPH/Total Acquisition cost?
Oooh I like that one... So if my max speed is say 200MPH with a FP and it cost me $50,000 total to "build" my plane I have an efficiency of .4% (200/50,000) *100)
If I put a C/S on and I now get 210MPH at $56000 my efficiency is .375% !
Its not hard to devise definitions to PROVE your point
Also, if I match my my airplane, engine, FP climb prop correctly it will do as well as an C/S in climb...but will certainly suffer in cruise.
But you might say yeah but I get to my destination faster..ok so maybe there is a benefit over the long haul for fuel savings. But with a 30lbs lighter plane I might be able to bring ALL of my wife's shoes, purses and hair products with me saving me that money at the destination end of the trip!!
BTW I had a guy with a 200hp RV-8 challenge me to a race in my 180hp BD-4. I told him no way he could possibly win and I was right...I kicked his butt!!! Actually he backed out...which is an even better win.
I told him the race was from St. Mary's, MD (2W6) to Ocean City straight line of about 70 miles...his plane cruised at 220 Mph mine was 180 Mph. He backed out cause the race was to see who could get their family of 4 from St. Marys to Ocean city with all their beach gear in the quickest time..HA!
Even SPEED needs to be defined to show one is "faster" than the other...
Honestly...this is not an effort to prove one is better than another...because I KNOW it cannot be done..because the criteria (as I've just shown above) can be tailored to fit your personal objectives... This is just for fun
But to make it really fun why don't those of you with flying RV-8 create a CAFE style fly-off
I've read everything you've wrote.....................and just have to say "so what..." But I'll even place a smiley here ....
As Rick has mentioned; yes I do fly out of a 4200' msl airport, and most flights are in the 8500 - 10500' range. No matter how you look at it, from dollars to weight, the C/S will outshine the F/P everytime in performance from takeoffs to landing. Pilots from around here will simply look at all your figures and say "bah". We are going from RV experience; not what we think might happen.
As you've said, the only way a fixed pitch is going to better perform on an RV over a C/S is to have one that's either pitched for climb or cruise. With a lighter plane, you might win in either climb or cruise, but never both....
And of course, the reality is, that most F/P's are compromised between climb and cruise. That is fact, as the owner is never quite content with just one or the other.
So fine, fly at sea-level with your wooden prop RV8, and I'll happily continue with my C/S. You said that you wouldn't have a top line C/S if it was given to you. Most F/P pilots around here could only wish for a top line C/S. They'd take it in a second if their engine allowed for it. And I'm not making this up. I've flown in many F/P equipped RV's in the last 15 years. I know exactly what these pilot/owners have said. But then............yes, we live in the mountains...
L.Adamson --- RV6A
Good luck with that one on RV fuel burn rates!
or my GF).. they are simply impressed that you can fly an airplane. The fuel burn difference is not enough to cause anybody to bounce a check to the FBO. The maintenance cost as well as the initial cost will be more than a FP. Usually there is a weight penalty of some sort with the CS... but if you did some yardwork every night then you could lose 30 lbs couldn't you? I was 250... now I'm 230... from doing yard work. 195 here I come. So if I may quote some non-descript redneck, "RUN WHACHA BRUNG" and be happy. And if it counts for anything... my helicopter has a CS 
There's no question to me about the performance advantage of the CS. I am on the fence though if it is worth the extra $$. Of course convincing my wife that we need to climb 200 fpm more and cruise 4 kts faster all for the bargain price of $10,000 is the real challenge.
