I could venture some estimates on all three but they wouldn't be accurate but then if you didn't like them I could venture some more. Now you know how I feel about most of the advertised figures you see now and then put out by some not so clever PR guy or the sales department. If you are looking for which engine will allow you to place as high as possible in a carrier contest then use what the top drivers are using and don't waste your time on anything else. Time is your most precious commodity.  Eric

Thanks, Doc. As for the horsepower issue, I hate to answer a question with a question, but here goes. What is your purpose in asking? Is it purely academic, or are you looking to compare various engines? If you check my previous post about carrier engine testing, you can see some RPM and airspeed data, all timed on the same model. As a bit of supplemental data, my first-string 36's will top 18,000 on the ground (APC 9x6), and if the stars are aligned I can go under 19 flat in high speed. This is on open exhaust, so I don't get the big rpm gain in the air like Eric and Burt might get with their tuned mufflers. It is also not on the same airplane. On my scale class airplanes, I don't have any RPM numbers in the ol' memory bank.

Of course in carrier we don't measure RPM or horsepower, only flight performance. Lots of factors can affect high speed, and the most power doesn't guarantee the fastest airplane. It takes the right prop to convert horsepower into speed, it takes good fuel system geometry to get off the deck strong and maintain a good setting in the air, it takes a properly aligned airplane to track straight and fly smoothly... I'm not telling you anything new.

If you really want actual horsepower numbers on engines that you have in your possession, contact Frank Williams. About 20 years ago, Frank made a series of test props by cutting down various Master Airscrews,running them on a variable speed electric motor on a torque stand, and was able to derive RPM vs horsepower charts for each test prop. If you ran a series of different test props and checked their peak RPM's, you could draw your own horsepower curves. It's an interesting exercise for its own sake, but I'm not sure how much it would help your carrier plane go faster.

Many years ago Glen Dye would test motors using calibrated test props from Kavan. I recall his standard for a .65 for carrier was about 4 hp. These were open exhaust, fairly lightweight cases. This might be appropriate for the Webra Speed .61 RR that I have been running since 1975. The Rossi .65s that Bill Melton ran would produce more (at the expense of greater weight and perhaps less reliability and controllability,) and the boat motors with pipes much more. So I estimate that a 4 hp Class 2 could be competitive, but have less power than some other available engines. I have found that reliability and controllability would often make up for a little less power. If I can get close to 4hp output from an electric setup (not yet accomplished in a reasonable package) with reliability and controllability then I should be able to match my gas airplane performance. If I could get, as a guess, 5 hp, then I could match Bill Melton's Rossis.
I don't have similar thoughts about the smaller engines but might scale them by displacement. The modern engines (Nelsons with mufflers) are off the curve of the older engines I am talking about as the high speeds from Eric and Burt are showing.
Buy the way, the reliability and controllability of the electrics has not yet reached that of my old Webra, but might after a little more work.
Pete

I would think that that the E-props are more efficient due to a thinner profile and design. This could make a difference in thrust for the same spec. prop.?