Counter Rotating Props?

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
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ghenry
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Counter Rotating Props?

Postby ghenry » Tue Feb 17, 2009 10:54 pm

Any thoughts on counter rotating props? Advantages/disadvantages? I heard the maintainance/repair can be more frustrating with more moving parts.
18' alumitech AGI-2, 540 felber, 4 blade sensenich superwide, 2.68 stinger gearbox

mwood7800
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Re: Counter Rotating Props?

Postby mwood7800 » Tue Feb 17, 2009 11:42 pm

just ###### junk, great idea, but dumb idea

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ghenry
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Re: Counter Rotating Props?

Postby ghenry » Tue Feb 17, 2009 11:55 pm

Thanks. Not real constructive, but point taken.
18' alumitech AGI-2, 540 felber, 4 blade sensenich superwide, 2.68 stinger gearbox

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Re: Counter Rotating Props?

Postby 21DiamondB » Wed Feb 18, 2009 12:06 am

Put your money into the horsepower not the drive unit. You'll get alot more bang for your bucks!
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airduds
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Re: Counter Rotating Props?

Postby airduds » Wed Feb 18, 2009 5:07 am

mwood7800 wrote:just ###### junk, great idea, but dumb idea

Respectfully disagree.

The kewl factor is over the top, gets rid of the torque thingy when you stand on it, and for reasons I don't quite understand, doesn't make spray.

I don't have one, but sure wouldn't pass on one if everything else was right.
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Re: Counter Rotating Props?

Postby Rich Andrews » Wed Feb 18, 2009 8:16 am

I think one company in particular has them figured out.I have seen them move some big boats with ease,pretty impressive for me. The boat they had in the boat show had them and the video of it performing was pretty good. I don't think a lot of people can afford them,so the verdict is still out.
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Re: Counter Rotating Props?

Postby jessejames » Wed Feb 18, 2009 8:34 am

ghenry wrote:Any thoughts on counter rotating props? Advantages/disadvantages? I heard the maintainance/repair can be more frustrating with more moving parts.

I dont want to sound like a a$$ hole but this term is often miss used. The proper term for two propellers turning in opposite directions, driven by the same engine is called CONTRA rotating , the term counter rotating is used on twin engine airplanes when each engine turns in opposite directions. I know everyone knows what you mean , but I like to know proper term. thought you would to.............. Ive seen them work great on some huge tour boats with bbc. Not sure what kind of maintenance they have to go through , but they push really well without the torque roll.
U name it I race it !.......... I just wanna go fast ! I twist my A/C like a small block !

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Re: Counter Rotating Props?

Postby GEO » Wed Feb 18, 2009 9:45 am

Image

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Airboatcapt2
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Re: Counter Rotating Props?

Postby Airboatcapt2 » Wed Feb 18, 2009 9:53 am

Thats a great video but I want to also say I can do the same thing w/out my counter rotater. The counter rotation does have more moving parts for potential problems.
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Re: Counter Rotating Props?

Postby Atlas » Wed Feb 18, 2009 10:08 am

From what I have seen of counter rotators (that is the term that the mfgs of these units use whether it is correct on airplanes or not) I have not been terribly impressed.

I think if it didn't add all the extra weight or if somebody would put one on a hull that doesn't weigh 1000 pounds it might be different, but my Stinger works so well with so little maintanence and weighs so little that I can't see enough advantage to justify the extra expense. You've got another prop to worry about.....

Panther's gear drive counter rotator may be another animal but I've never seen one running and from what I hear you can't get one unless it's on one of their boats....

That video was pretty cool to watch though.

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Re: Counter Rotating Props?

Postby 21DiamondB » Wed Feb 18, 2009 10:39 am

What are y'alls thoughts on the gear drive counter rotators vs the belt drive. I know you Florida guys like the gearboxes but they are both different in the counter rotator in that the gear counter rotator that Panther has both turns the same ratio on the front and back with the same warp drive props and the beltdrives are two different ratios with two different props, usually a wide blade and a more narrower blade? Which one has more thrust or benefit?
-------- 16.5 x 8 Diamondback - 632ci - Oxbox 2. 55 - Sensenich 5-Blade JX---------

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Re: Counter Rotating Props?

Postby rost495 » Wed Feb 18, 2009 10:57 am

Dang that mule makes a nose heavy and nose low boat for sure!

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Re: Counter Rotating Props?

Postby shiggs » Wed Feb 18, 2009 11:10 am

I think to answer your question 21diamondB, you would have to hook both up to Felber's thrust machine to map out actual thrust curves with everything else being equal. I think anything else is subject to hearsay and potential BS. I would be very interested in a comparison of that nature. One uses relatively "soft" blades in the same ratio, vs. another that force feeds the higher velocity prop with a slower turning big blade front prop. It would be great to see the results of a comparison like that.

As far as the other question:

Most folks like myself who have owned one, did not have an identicle boat with nothing different besides the CR to compare to. Now you can see advantages in TQ Roll etc, but for thrust #'s you can get a rough idea--but it is still subjective unless you are doing exact apples to apples comparison.


They can utilize monster engine/monster power and eliminate the TQ Roll that normally comes along with those. Depending on props, they can have a sound advantage as well. Some have reported greater increase in fuel mileage compared to boats without--in tour businesses.

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Re: Counter Rotating Props?

Postby filetnrelease » Wed Feb 18, 2009 4:19 pm

If you guys do a search (type in counter rotator), you can find a bunch of info... info also regarding thrust and efficiency from those that have seen and/or done testing. This topic has come up quite a bit
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