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Anyone ever tried a constant speed prop?

Posted: Tue Mar 24, 2015 11:53 pm
by Fookz92
So yeah, has anyone ever tried a constant speed prop on their boat? On an airplane, there is the propeller governer that contains oil and with some moveable internal parts. By adjusting a level, the prop pitch is adjusted. Can this be possible setup on a boat? Has anyone ever tried it?

Re: Anyone ever tried a constant speed prop?

Posted: Wed Mar 25, 2015 4:59 am
by gyrocopter582
Fook, next time you are doing a run-up in a complex, try this for an answer to your question;
bring the RPM's to say 1700, then bring the prop lever back until you see a 100 drop.
Now advance the throttle. The rpm will stay at 1600 all the way to wide open.
The 'governor ' is doing its job, but wouldn't work well with continuous throttle changes in an airboat.
If the governor could be modified to JUST change the pitch, it would be great!

Re: Anyone ever tried a constant speed prop?

Posted: Wed Mar 25, 2015 11:40 am
by plumcrazy
we have a on the fly driver adjustable hub on our blue ligtning boat .. it worked very well, its beneficial to be able to adjust pitch on a airboat propeller .... we are currently redesigning the belt drive and the hub to make it lighter and afordable :thumbleft:

Re: Anyone ever tried a constant speed prop?

Posted: Thu Mar 26, 2015 6:26 am
by gyrocopter582
David, adjustable pitch would be fantastic on an airboat, I would like to see how your propeller is designed.

Re: Anyone ever tried a constant speed prop?

Posted: Thu Mar 26, 2015 9:09 am
by Fookz92
gyrocopter582 wrote:Fook, next time you are doing a run-up in a complex, try this for an answer to your question;
bring the RPM's to say 1700, then bring the prop lever back until you see a 100 drop.
Now advance the throttle. The rpm will stay at 1600 all the way to wide open.
The 'governor ' is doing its job, but wouldn't work well with continuous throttle changes in an airboat.
If the governor could be modified to JUST change the pitch, it would be great!
Hmmmm, you have a point..... what if the flyweights were taken out? That way it will stay at the same pitch for whichever the operator sets it at?!

Re: Anyone ever tried a constant speed prop?

Posted: Tue Sep 22, 2015 9:30 am
by Planeguy
What about an automatically adjusting prop that uses counter weights like the Aeromatic? In theory it adjusts with the engine and air load to produce the best power.

http://www.aeromatic.com/

Re: Anyone ever tried a constant speed prop?

Posted: Wed Sep 23, 2015 8:43 am
by Planeguy
gyrocopter582 wrote:Fook, next time you are doing a run-up in a complex, try this for an answer to your question;
bring the RPM's to say 1700, then bring the prop lever back until you see a 100 drop.
Now advance the throttle. The rpm will stay at 1600 all the way to wide open.
The 'governor ' is doing its job, but wouldn't work well with continuous throttle changes in an airboat.
If the governor could be modified to JUST change the pitch, it would be great!
The governor on a on a constant speed prop regulates RPM by changing JUST pitch to load the engine so the engine can't turn any faster. Its just not a direct link and the governor usually regulates the pitch in relation to RPM with oil pressure. Lugging the engine down too much like that is likely to cause bad things to happen (wasted fuel, overheat, maybe even detonation). I would think the operator would always want the prop at it's lowest pitch setting (control forward or in) to generate maximum thrust until they had somewhere to go. Then, after the boat is on step, the pitch could be increased to get maximum speed for the fuel being burned. I do agree it would be a waste of time to put a constant speed prop on an airboat unless a person does a lot of cruising at constant power setting (probably a high power setting).

Re: Anyone ever tried a constant speed prop?

Posted: Wed Sep 23, 2015 1:16 pm
by JCGator
the turbine boat that was in marsh rider a while back had a constant speed prop where throttle adjusted the prop pitch. couldnt find the article. http://www.southernairboat.com/photopos ... at/cat/500

Re: Anyone ever tried a constant speed prop?

Posted: Wed Sep 23, 2015 5:36 pm
by Planeguy
Now that is cool! I expect it is a thirsty critter to run though. Turbines are different than pistons. That little turbine most likely runs at full throttle all the time so the only way to control it would be by adjusting the prop. Some turbo-prop aircraft work the same way. Another thing, turbines are notoriously slow to spool up. It takes a few seconds to go from idle to full power so even if this one can idle, it would be much better to leave the power up and control with pitch.

According to a post under that picture, the article was in the Sep/Oct 2009 Marsh Rider.

Re: Anyone ever tried a constant speed prop?

Posted: Thu Oct 22, 2015 5:25 pm
by Grasmo
Manifold vacuum could be an input for pitch change.

Re: Anyone ever tried a constant speed prop?

Posted: Thu Oct 22, 2015 8:16 pm
by Grasmo
Manifold vacuum could be an input for pitch change.

Re: Anyone ever tried a constant speed prop?

Posted: Thu Oct 22, 2015 8:36 pm
by Gangreen
Not to be an ass but the gas peddle usually is what makes it constant. Just want to keep it simple.