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  #11  
Old 02-28-2010
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My biggest concern with non-fixed prop, is that it will decide to stop
feathering, requires more maintenance, and will require a haul-out if it
does fail.
Tom
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  #12  
Old 03-01-2010
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Calder on drag (MC1's Question)

Calder doesn't offer any specific formulas or numbers but says most folding and feathering props will "greatly reduce drag when under sail, so it is ironic to see their proliferation at a time when less and less time is spent under sail" (page 201).

He goes on to rank two-bladed folders as best for sailing (least drag) and worst under power; feathering props, like MaxProp, as having a bit more drag and as being almost comparable to fixed props in forward and better in reverse; and variable pitch props, like Brunstons, as having more drag than feathering but "significantly improved performance under power throughout a boat's speed range" (202).

And, to give credit where credit is due, the citations above are from Nigel Calder's Cruising Handbook, International Marine/McGraw Hill, Camden, ME, 2001.

I couldn't find anything much more specific about drag in that section of the book, but Calder's comments on the sailing side of the issue would seem to have face validity. If one looks at the underwater profiles of the props, it would seem logical as to which would create the most drag under sail.

Roger Lopata
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  #13  
Old 03-01-2010
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Thank you Roger - very nice summary, I appreciate your effort in looking it up and posting it. Nigel's writing seems in general agreement with our discussion here.
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Old 03-01-2010
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Thanks for the insight.

Thanks everyone for your advice. This has been very useful.

We are planning for extensive cruising to far away lands. So performance under sail for long legs is important. I also single hand a lot and have a tight slip, so prop walk is a concern. And occasionally I am motoring in SF Bay and the Delta, contenting with strong currents.

So in summary it appears as follows:
  • Forward thrust - performance is about the same (slight advantage with fixed)
  • Reverse thrust - less prop walk and better acceleration with feathering prop
  • Under sail - feathering prop leads (with some mixed opinions)
So I guess the biggest trade off for me is: better control in reverse or a lower maintenance prop. I'm always for simplifying a system when possible if it can be achieved without sacrificing performance or safety. So I'll get a fixed-prop, but also look into getting my Max prop fixed (great idea - only the blades are in poor condition, the hub and gears are very clean). And then take this question to sea for an experiment.

If I can live with the performance of the fixed prop, and have lower maintenance to boot, I'll go that route. If not I'll replace with the refurbished Max prop. In either case I'll have a back up prop while cruising around the world.

And I'll add Nigel Calder's Cruising Handbook to my library. Great summary, Roger, Thanks!

Thanks again for sharing your thoughts and experience.
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Old 03-01-2010
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Max Prop vs. Feathering

Everyone has an opinion on this one.

My boatyard is really anti-Max Prop. I was seriously considering going with a fixed prop as two of my buddies were. I was going this way largely because of the every 3 month zinc change and the purported better motoring. I have decided to hold off for a bit longer given the experiences of my two friends.

The first has a Tartan 40 and a Westerbeke 40+. He had the prescribed new 3 blade prop installed and he is miserable. His speed has decreased at the same rpm and his backing down is worse. He may have been stressing his engine with the Max Prop's settings he was using but he is really unhappy.

The second friend has a Moody 42 with the same engine as me, Yanmar 4jh2te. He put on the biggest fixed 3 blade prop he could. We motored on and off for 10 days together this past fall on the way to Annapolis and if anything my boat was a bit faster despite its shorter waterline and heavier displacement. I was very surprised and so was he.

So, I'm holding off a bit longer before this item hits the top of the priority list.

Roger Block
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Old 03-01-2010
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One other thing to keep in mind whether you go fixed or feathering prop is that either way, its important for the health of the engine to ensure it can reach its specified maximum RPM. Both prop diameter and pitch have an effect on this. The diesel engine forum might be a better place for a thread on this aspect though.
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PYI - Repair Costs

Just got off the phone with PYI - They can repair the Max-prop blades. $800 would be the cost on the high end. 3 new blades costs $1,550.
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Old 03-01-2010
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Quote:
Originally Posted by teejayevans View Post
My biggest concern with non-fixed prop, is that it will decide to stop
feathering, requires more maintenance, and will require a haul-out if it
does fail.
As I have stated many times in this forum, no prop, fixed, folding or feathering requires a haulout for repair or maintenance. A qualified diver can pull and reinstall any prop made while the boat is in the water, Max Prop included.
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Old 03-01-2010
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Quote:
Originally Posted by rtblock1@juno.com View Post
.....
The second friend has a Moody 42 with the same engine as me, Yanmar 4jh2te. He put on the biggest fixed 3 blade prop he could. ...
Selecting the biggest prop is insensible and a probable source of engine problems. The prop needs to be sized to the engine and boat, both in terms of size and pitch.

IMHO, going with a fixed prop on a sailboat which for most of us (except the multihullers like SD) means we have an already relatively slow boat, only makesd sense if you expect to be powering most of the time. With some sailboats, that is a reasonable assuption to make.
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Old 03-01-2010
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xort has a spectacular aura about xort has a spectacular aura about xort has a spectacular aura about
bene

If you talked with maxprop, you got good phone support.
They will tell you that you will loose a little less than 5%, under power vs. a correctly sized fixed prop. And you will loose about 15% to 20% under sail with a fixed prop vs their folder.
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