Engine limiting factors

Thanks for all your responses. A little bit of back story to this may help to see what I am getting at.

I am using a Eprop made in France and the performance results are outstanding when you compare what we have all been using previuosly. The setup is you tie the aircraft down on the ground and pitch the prop for 5500 or 5600 at WOT. Now this is what most do here and a lot of people here in OZ use the Bolly prop. Usually on climb you can only achieve aound 5200 to 5300 max rpm and it seems to work quite well but that is sort of how its always been done for years by everyone. With the Eprop though the performance is dramatically different. If you do as said above you can usually get almost max rpm on climb.

This produces much more cruise and much better takeoff roll also much better climb performance..and not by a little...by quite a lot. We have replaced warpdrive and Sensinich etc and also got major performance difference. For example a savannah (and this has now been done on at least 4 savannahs) cruise speed has gone from the usual 85kts up to 90kts at 5000 rpm..for a savannah and its wing that is outstanding. Also climb has gone from 1200ft/min to 1500 and more. The same for a Tecnam and also Foxbat A22..A CTSW has increased also by 10kts in cruise the CT had a Nuform prop as factory fitted. The blades of a Eprop are very narrow and have a very different helix compared to most others.

So testing was done recently that used the 5800 rpm as the top RPM inflight at WOT and when several other props were setup the same there was not much difference in performance between them all. So what is different?. The Eprop is extremely light the whole assembly weighs only 2.4kg inc the spinner. The bolly setup and the extension for a savannah is almost 6.5kg. We are very shortly going to try replacing a Airmaster constant speed prop with the Eprop and see how much difference there actually is. Horsepower is horsepower and I understand what Bill is saying and have no doubt about it but the performance difference with this prop is just too far ahead of anyting else to not be something different to what we have been used to. Its not just objective observations it real numbers that have been tried nd true for a long time with the current types of props we have been using previously.

Bill, I appreciate your response, and it makes a lot of sense (as usual) but are you saying there is not any tradeoff between takeoff power and economical cruise when it comes to choosing ground-adjusted prop pitch?

I am using a Eprop made in France and the performance results are outstanding when you compare what we have all been using previously. The setup is you tie the aircraft down on the ground and pitch the prop for 5500 or 5600 at WOT. Now this is what most do here and a lot of people here in OZ use the Bolly prop. Usually on climb you can only achieve aound 5200 to 5300 max rpm and it seems to work quite well but that is sort of how its always been done for years by everyone. With the Eprop though the performance is dramatically different. If you do as said above you can usually get almost max rpm on climb.
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This is because the Bolly is being set for an OverPropped condition and the Eprop for something more nominal.
For ANY prop, the Static Ground RPM is only a starting point to get you in the ball park.
After a test flight, the prop should be re-pitched to produce ~5800 in the initial climb.
This will allow the engine to produce maximum POWER, and all the props will show very little difference.

Quoting the RPM as a reference is very misleading.  It is NOT the RPM that matters.  It is ALWAYS about POWER!
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 For example, a Savannah (and this has now been done on at least 4 savannahs) cruise speed has gone from the usual 85kts up to 90kts at 5000 rpm… for a savannah and its wing that is outstanding. Also climb has gone from 1200ft/min to 1500 and more. The same for a Tecnam and also Foxbat A22..A CTSW has increased also by 10kts in cruise the CT had a Nuform prop as factory fitted. 
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Again, comparing two props and using RPM as a reference is unsound logic.
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So testing was done recently that used the 5800 rpm as the top RPM in-flight at WOT and when several other props were setup the same there was not much difference in performance between them all. So what is different?
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This is to be expected.
If each prop is pitch so that it turns at 5800rpm at WOT, each will transfer the same POWER and produce the same results.
With small variation, any reasonably designed prop is going to produce the same results when being driven at the same power level despite what the manufacturers marketing departments promise.

There is no magic propeller design that will make your plane fly significantly better than any other prop if they are all installed and pitched properly.
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What you will not be able to outperform will be the Airmaster Variable Pitch prop.
You will be able set 5800 rpm at WOT throttle in the climb and then reduce to 5500 rpm still at WOT in cruise.
The prop will always be optimally pitched at all airspeed and all altitudes.
This has been known since the 1930's.
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If you have the ability, test each prop at the same fuel flow rate instead of RPM...  (Fuel flow ≅ Power)
You will find that your cruise speed may be higher at the same RPM with a different prop. but you will also find that the Fuel Flow rate is also higher due to actually operating at a higher power setting.
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I know I keep repeating this, But it is the core of the matter...
RPM is the easiest thing to measure and it just feels like it is proportional to Power, and it is, only as long as you do change ANYTHING related to the Prop.
Anything you change related to the prop is also going to change the RPM at identical Power settings.  
And ... It is ALWAYS about POWER!!!  Not Torque, Not RPM, POWER!!!

Totally agree with everything Bill says,

   Prop design has been a science since about 1935, the most efficient prop ever built was on the Constellation and hit about 85% effficiency in the cruise. Given modern software and CFD designing an efficient Prop is a first year engineering school exercise.

I was involved with a certain type of prop design for over 30 years....the difference between a "bad design" and a "good design" on a certified thrust rig was about 3%.

To reiterate the purpose of a Prop is turn POWER into THRUST.  RPM is a very poor analog for Power.

If you want MAX Thrust you need the match the Prop power needs to the Engine Power delivery. That means you ideally want 5800 rpm at WOT for the 5 min you are allowed and then 5500 rpm all day.

Comparing props on an Aircraft even the same aircraft is difficult changes on OAT barometric pressure etc mean that you loose/gain POWER at the engine...you need to be very precise to make comparisons. That is why certified test rigs were developed.

The bigger the diameter the prop the designer is allowed to use the more thrust for the same Power. The Wright brothers got similar thrust vs our Rotaxes with 15 hp because they used two 17' diameter geared props.

In our world we are limited in diameter because of the Airframe design there are fixes but they all have compromises too. (#Bentwing bird #Corsair).

Bill is right we set up the Bolly's wrong and do so on most props but I am past my days of being different to the rest of the crowd, I just want to fly and have fun. The local STOL group has numerous different props all set up the same, sub-optimal way. The only time we change things is for our annual National STOL comp and for the last four years that has meant pitching fine so you get 5800 on TO and one of our members has always won. Then they repitch back to "standard" for the rest of the year.

I did the same on my LSA for the Comp and T.O. reset the prop to get 5800 on Roll where as the factory setting is only 5500...big difference...same prop. After the Comp put it back to Manufacturers specs.

Havng said all of that it is alot of fun playing with settings and seeing the results so enjoy your Eprop and you have the Manufacturers permission to allow it to rev up more.

We have made "our" actually my wifes Savannah fly much better with a lot of little tweaks and with her in it it can get off very quick 40m no wind and a lot shorter with. This is of course with little fuel, no baggage and a litte lady Pilot.  When I sit in the second seat it adds another 30m....

Flying is Physics meet Fun

My prop is very coarse. It's max is 5200 RPM and I cruise at 4000-4200 RPM. The previous owner reckons this is will engine life. I tend to agree with him. Only down side is a slower cruise speed (95 mph @4200)

I fly at sea level. Originally it was used for training @5500ft amsl