What's wrong with folding props ...
- Thread starter Scott T-Bird
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Emergency Stop
An Emergency Stop is when you are tootling along in open water at 6 - 7 knots and suddenly see a half sunken log/ fishing pot/ another boat dead ahead and at point blank range.
That is when you do an emergency stop. Often the reaction is involuntary just like when driving a car.
Each prop blade is trying to pull the boat backwards against the water flow and even at full rpm, with a folder, it is not certain that the blades will remain fully opened.
Of course prop designers are well aware of this and try to build in sufficient tip weight to counteract this effect.
If only they would publish their figures so WE can make out own minds up.
For info on a practical folding and feathering prop test, including measured thrusts and prop walk, take a look at the Yachting Monthly (a major UK) magazine's prop test.
See their actual test on U-Tube as below and at 34 seconds and 4 min 22 seconds where the boat just keeps on going ahead! From memory it was either the Flexifold or the Varifold.
BTW - All the folders had less thrust astern (for pulling off sandbanks) and all had longer stopping times:-
http://www.youtube.com/watch?v=B4xwJkUfU6o
Or buy the May 2009 article from YM's web site.
An Emergency Stop is when you are tootling along in open water at 6 - 7 knots and suddenly see a half sunken log/ fishing pot/ another boat dead ahead and at point blank range.
That is when you do an emergency stop. Often the reaction is involuntary just like when driving a car.
Each prop blade is trying to pull the boat backwards against the water flow and even at full rpm, with a folder, it is not certain that the blades will remain fully opened.
Of course prop designers are well aware of this and try to build in sufficient tip weight to counteract this effect.
If only they would publish their figures so WE can make out own minds up.
For info on a practical folding and feathering prop test, including measured thrusts and prop walk, take a look at the Yachting Monthly (a major UK) magazine's prop test.
See their actual test on U-Tube as below and at 34 seconds and 4 min 22 seconds where the boat just keeps on going ahead! From memory it was either the Flexifold or the Varifold.
BTW - All the folders had less thrust astern (for pulling off sandbanks) and all had longer stopping times:-
http://www.youtube.com/watch?v=B4xwJkUfU6o
Or buy the May 2009 article from YM's web site.
It's usually best to lock the transmission in gear anyway, no matter what kind of prop you use. BTW, my 3-blade Gori poses no problems, noise, or whatever. It's also just fine in reverse.
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