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Any new take on Counter Rotating Props?

leo_081103

leo_081103

Well-known member
Does anyone have any info to the developments and actual performance of the counter rotators? Does existing units live-up to it's claims?
 
I sell a bunch of them but I am also Honest with my customers.
There is not a 30% Increase in Thrust and a 30% Decrease in Sound.

IMO there is about a 10 to 15% increase in thrust and I have not seen one hit lower marks on a DB meter.

The idea behind it being quieter could be true if you use your thrust at lower RPM'S to cruise but the CR unit makes additional noise.
 
Seems like not alot of extra thrust for only 10,000 grand, when you figure the extra prop, drive unit, longer boat, and cage
 
leo,

Works fine for me :wink:

Couldn't even imagine holding a conversation on the boat with the existing 3 blade prop. And yeah, like I knew it would my boat came alive when converting from a 3 blade to a C.R. assembly.

Yee-hah...no torque roll at all!

Techno stuff aint' cheap.

Basketcase
 
unreal-convair-pogo.jpg


Tu95ms_1.jpg
 
Jim, the big four engined aircraft ..... a Soviet Bison ? They were very long range, high altitude bombers.

olf
 
I have about 50 hours on my CR and will never go back. Diamondback told me they were almost at 2 out of 3 new boats ordering the CR.

For me it did take some getting used to at start up because it rumbles a bit until she's warmed up, and at lower RPMs. I have an 80" Sensenich Q-series feeding an 82" wide blade Sensenich. Although I can't prove this quanitatively, I am convinced that the extra thrust is somewhere in the 20-30% range.

For the applications I use it for (duck hunting on big water), it was money well spent.
 
leo,

If you haven't seen it yet...gotta see the movie "The Aviator". Documetary/story of Howard Hughes life....gives credit to him for inventing/patenting the c/r on aircraft. He crashed the same over Hollywood in the 40's and most people gave up hope on the aircraft then.

Basketcase
 
basketcase0302


yeah, i've seen that film. it was a great way to have a peek at one of the most significant part of aviation history---kinda makes you hot too! LOL

is it true that he loss the aircraft because he ran out of fuel? as if he was an airboater, if something comes up good, fuel supply tends to be secondary :D

that's why i always carry an extra tank....
 
At this point and time they are only good for applications over 18ft. One of the most impressive boats I ever saw run was a huge Classic barge with a gear counter rotator which I prefer because they are so much lighter then the belt drives. I think Classic has them down to under a 100Lbs. Anyway this boat was very quite, me and my wife were talking to each other while riding down a river this was one of only two boats I have ever been able to do this on. When he hit the ground this 20 ft plus boat ran the hill better then 95% of the air boats I have seen, needless to say it was very impressive.
 
Counter rotators will not do good in racing because of how short of a race we run. Adding 30 to 40 pounds more of gearbox and another 25lbs of prop will slow a boat down even if you add more thrust. Also to run a counter rotator you need to run at least a 16ft or longer boat so now your boat is heavier and longer. Now on paper a longer boat would be faster however due to the ramps all the sanctioning bodies are using a 16ft boat would drag on the ramp much longer and the 12ft boat would be 20ft out front before the bigger heavier and longer boat that is still dragging on the ramps. Now I know everybody say's well put a counter rotator on a shorter boat well if you do that you will have a very slow boat.
 
I put a ton of thought into running a counter rotator in a race boat. But all things considered plus the fact of who and how the ramps are set up I feel a C/R would hurt a boat at the most crucial part of the race and no matter how much better it performed every where else it couldn't compensate for it's pour hole shot off a ramp. Now if we race from a floating position it could work or if the track was 500 or 600ft it would be a no brainer.
 
The limiting factor right now is hulls. Nobody is building a hull that works with over a 1,000HP pushing it. Any hull out there now will run just as fast if not faster making 900HP then it would making 1,600HP. There are two limits width and the ability to prevent torque roll. A C/R will limit torque roll and that is why I considered it but for the distances were running I don't think it will work. And going wider you will just end up on the roof. I feel longer is the short term answer but the ramp's can be adjusted to seriously cripple a long boat.
 
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