Friday, June 3, 2011

Folding propeller

Heron came equipped with a fix 3 blade propeller.
This is fine for motoring, but sailing with a fixed propeller is adding a lot of drag.
It is like dragging a large bucket behind the boat and some measurements showed that propeller contributes 40% to total boat drag.
This studies (mostly sponsored by folding prop manufacturers, of course) also suggest that replacing a fix prop with a folding or feathering prop will add almost a knot of speed to your boat.
One knot of speed does not sound like a lot, but at average boat speed of 5 knots this is a lot. This means that after full day of sailing you can land two hours earlier. This can be a difference between coming at anchorage at daylight, anchor and have a nice cocktail, have a swim, watch a sundown and then wait in the dark for your friend with identical boat and a fixed prop. You can make Atlantic crossing a few days faster.
Most manufacturers claim about 15% increase in speed.
Well, I was a little skeptical, although this study seemed a good one:
So, we bite the bullet (folding props are expensive) and we ordered a three blade flex-o-fold.

We had Heron on the hard early May and my wife and myself mounted it.
By the way - dismounting the old one is a good story for a long evening.

We also had our boat cleaned and had new antifouling - so I knew I can not expect a fair competition, but Wow!
I was impressed.
We can motor now at lower RPM and we can sail faster with less wind.
It feels like a completely new boat.
Boy, am I happy we did this improvement.
I sail only few weeks with this new folding Flexofold prop, but I am happy.
We also have less prop walk in reverse (which I kind of miss as I liked to come to the pier and with some reverse thrust I was able to move the stern to port (left).
But the boat is easier to steer in tigth quarters now.
And the true value comes when you kill the engine, put it in reverse for a second to stop the prop from spinning and then she just glides.
I really believe now in 15% increase in speed.
I now more often sail and I motor less as I can sail in very little wind.
We also have less vibrations - but that can be from havin a clean prop and hull.
I would strongly recommend a folding prop for every sailor.

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