Anyone have any experience installing a feathering two or three blade prop on a Cape Dory 28? Just got a drawing from MaxProp and it looks like it might not fit the cutout between keel and rudder. Anyone have experience with the Paul Luke prop? The boat's been repowered with an 18 hp Yanmar and should reach hull speed. Right now we can't get it over 5.0 knots (during survey and sea trial). The existing prop is a 13"x(?) 2 blade with maybe not enough pitch for the engine. Any comments would help.
Thanks
Mark Hoffman
markhoff@aol.com
Installing a 13" MaxProp-will it fit CD28 cut out?
Moderator: Jim Walsh
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Tom
Re: Installing a 13" MaxProp-will it fit CD28 cut out?
At 5 knots you were pretty close to hull speed. Your water line length is 22 ft 2.5 inches. Square root of that is 4.7. 4.7 times 1.2 is about 5.5 knots. You're only half a knot off hull speed which might be accounted for by any wind against you or wave chop unless the sea and current was absolutely flat and the wind flat as well.
No experience with maxiprop so can't help you there but if the blade gets too close to the hull you'll hear a thump thump from the prop wash. There's a formula for how close the prop can be, but I don't remember it off hand. You do need more clearance than jut barely missing though. Hope this helps.
TomCambria@mindspring.com
No experience with maxiprop so can't help you there but if the blade gets too close to the hull you'll hear a thump thump from the prop wash. There's a formula for how close the prop can be, but I don't remember it off hand. You do need more clearance than jut barely missing though. Hope this helps.
Mark Hoffman wrote: Anyone have any experience installing a feathering two or three blade prop on a Cape Dory 28? Just got a drawing from MaxProp and it looks like it might not fit the cutout between keel and rudder. Anyone have experience with the Paul Luke prop? The boat's been repowered with an 18 hp Yanmar and should reach hull speed. Right now we can't get it over 5.0 knots (during survey and sea trial). The existing prop is a 13"x(?) 2 blade with maybe not enough pitch for the engine. Any comments would help.
Thanks
Mark Hoffman
TomCambria@mindspring.com
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Ben Thomas
Re: Installing a 13" MaxProp-will it fit CD28 cut out?
Mark, This past weekend I attempted to install a 13" maxprop on my cd 30. Does not FIT! There is plenty of clearance top to bottom of aperture, the problem lies in horizontal space from cutlass to forward edge of rudder. To make the prop fit without wacking the rudder on port and starboard turns would intail removing the rudder, sculpting the forward edge through the rudder stock (metal) of the rudder, creating a big half moon affair. welding the new piece (rudder Stock) in then glassing the work over and reinstalling the rudder. wait its not over, another alternative.Mark Hoffman wrote: Anyone have any experience installing a feathering two or three blade prop on a Cape Dory 28? Just got a drawing from MaxProp and it looks like it might not fit the cutout between keel and rudder. Anyone have experience with the Paul Luke prop? The boat's been repowered with an 18 hp Yanmar and should reach hull speed. Right now we can't get it over 5.0 knots (during survey and sea trial). The existing prop is a 13"x(?) 2 blade with maybe not enough pitch for the engine. Any comments would help.
Thanks
Mark Hoffman
The prop shaft needs to be shortened, the cutlass moved forward into hull instead of protruding out which gives you maybe an inch more clearance then you still need to handle the rudder problem.
This applies to the 3blade and 2 blade max prop. 2 blade has longer tail which needs 3/4" more clearance aft.
needless to say it was a disapointment. The runway is really long and expensive. I opted to re pitch my old 2 blade the volvo md7a just couldn't make it over 1800 rpms at 3 1/2 knots.
I'am sure the same problems will be incurred with the cd 28. I'am looking forward to racing along motoring at 5 knots. Better yet sails up at 7 knots !!!
a good prop shop should be able to match a prop up for you.
Good Luck, Ben
btlandscapers@imagina.com
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Robert
Re: Installing a 13" MaxProp-will it fit CD28 cut out?
I ordered a 13" Max Prop for my 79 CD 28. It was a beautiful piece of gear. I couldn't wait to put it on and see the improved performance that everyone talked about, especially backing down. But it was not to be. After preassembling the Max Prop, measurements showed that, as mentioned in the post on the CD 30, the blades would hit the rudder when it turned. Not wanting to make any radical hull or rudder modifications, I had to return the Max Prop.
The three-blade prop I have on now (fixed of course!) does fine in forward. It's a 13x10 (13 inch diameter, 10 inch pitch). I believe the original two-blade was a 13x13. This is for the Volvo-Penta MD7A 13 hp engine.
Good Luck,
Robert,
s/v Zephyr, CD 28 #230
BobF@txas.com
The three-blade prop I have on now (fixed of course!) does fine in forward. It's a 13x10 (13 inch diameter, 10 inch pitch). I believe the original two-blade was a 13x13. This is for the Volvo-Penta MD7A 13 hp engine.
Good Luck,
Robert,
s/v Zephyr, CD 28 #230
BobF@txas.com
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Larry DeMers
Re: Installing a 13" MaxProp-will it fit CD28 cut out?
Ben,
Did you happen to check with Autoprop or PYI about their autofeathering props? I know that these are two different designs..but they might just fit.
It is disappointing that the Max prop does not fit our CD30's. I was thinking about that upgrade for next year, should I still be employed gainfully.{layoffs here..}.
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
Did you happen to check with Autoprop or PYI about their autofeathering props? I know that these are two different designs..but they might just fit.
It is disappointing that the Max prop does not fit our CD30's. I was thinking about that upgrade for next year, should I still be employed gainfully.{layoffs here..}.
Larry DeMers
s/v DeLaMer
Cape Dory 30
Ben Thomas wrote:Mark, This past weekend I attempted to install a 13" maxprop on my cd 30. Does not FIT! There is plenty of clearance top to bottom of aperture, the problem lies in horizontal space from cutlass to forward edge of rudder. To make the prop fit without wacking the rudder on port and starboard turns would intail removing the rudder, sculpting the forward edge through the rudder stock (metal) of the rudder, creating a big half moon affair. welding the new piece (rudder Stock) in then glassing the work over and reinstalling the rudder. wait its not over, another alternative.Mark Hoffman wrote: Anyone have any experience installing a feathering two or three blade prop on a Cape Dory 28? Just got a drawing from MaxProp and it looks like it might not fit the cutout between keel and rudder. Anyone have experience with the Paul Luke prop? The boat's been repowered with an 18 hp Yanmar and should reach hull speed. Right now we can't get it over 5.0 knots (during survey and sea trial). The existing prop is a 13"x(?) 2 blade with maybe not enough pitch for the engine. Any comments would help.
Thanks
Mark Hoffman
The prop shaft needs to be shortened, the cutlass moved forward into hull instead of protruding out which gives you maybe an inch more clearance then you still need to handle the rudder problem.
This applies to the 3blade and 2 blade max prop. 2 blade has longer tail which needs 3/4" more clearance aft.
needless to say it was a disapointment. The runway is really long and expensive. I opted to re pitch my old 2 blade the volvo md7a just couldn't make it over 1800 rpms at 3 1/2 knots.
I'am sure the same problems will be incurred with the cd 28. I'am looking forward to racing along motoring at 5 knots. Better yet sails up at 7 knots !!!
a good prop shop should be able to match a prop up for you.
Good Luck, Ben
demers@sgi.com