We recently accquired a 1983 CD30, and have found that the existing RH 15x10 propeller causes the boat to severly turn to
port when backing. Limiting the throttle helps a bit, but backing in a straight line or to starboard is near impossible. The gentleman who surveyed the boat at purchase suggested a 3 blade prop for improved power transmission, and a friend (tug boat captian) said a 3 blade would improve the control, but I am concerned with the impact on boat speed under sail. I would
appreciate comments from anyone who has a 3 blade prop or solved the problem some other way.
CD30 Prop Change?
Moderator: Jim Walsh
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Jon F. Larson
Re: CD30 Prop Change?
I asked Cape Dory many years ago about changing
the prop on my 1981 CD30 from the standard 2 blade
prop to the 3 bladed prop, and asked the same
questions. I was told that the impact on sailing
performance was negligable, but that the 'bite'
in reverse and in powering to windward would be
very improved. I didn't discuss with them the
tendancy (which I use when manouvering in close
quarters..you can spin this boat on a dime) for
the stern to go to port in reverse, but in
understanding how this happens, I do not think
the three bladed prop would affect that
characteristic. Indeed, much as I love this boat
and Carl Alberg's design product, I understand
that any long straight keel with keel hung rudder
is going to be squirrely when backing.
I do have a friend who put a three bladed prop
on her CD30..plus new sails, etc. and that boat
sails very nicely, but tough to know if the prop
did anything. I think her prop is underpitched,
the engine over revs when full throttle and normal
cruising speed is much lower than mine under
normal circumstances..so be sure, if you do
switch, to get the right pitch. Oh, the three
bladed prop Cape Dory did use was a special
modification...of, I think, an Columbian prop,
Columbia Prop may have some info in their files,
if my memory is correct.
Good luck, if you do it, let me know how it
works out..I've long been tempted!
Jon Larson
CD30 PERI
San Francisco Bay
jon9@ix.netcom.com
the prop on my 1981 CD30 from the standard 2 blade
prop to the 3 bladed prop, and asked the same
questions. I was told that the impact on sailing
performance was negligable, but that the 'bite'
in reverse and in powering to windward would be
very improved. I didn't discuss with them the
tendancy (which I use when manouvering in close
quarters..you can spin this boat on a dime) for
the stern to go to port in reverse, but in
understanding how this happens, I do not think
the three bladed prop would affect that
characteristic. Indeed, much as I love this boat
and Carl Alberg's design product, I understand
that any long straight keel with keel hung rudder
is going to be squirrely when backing.
I do have a friend who put a three bladed prop
on her CD30..plus new sails, etc. and that boat
sails very nicely, but tough to know if the prop
did anything. I think her prop is underpitched,
the engine over revs when full throttle and normal
cruising speed is much lower than mine under
normal circumstances..so be sure, if you do
switch, to get the right pitch. Oh, the three
bladed prop Cape Dory did use was a special
modification...of, I think, an Columbian prop,
Columbia Prop may have some info in their files,
if my memory is correct.
Good luck, if you do it, let me know how it
works out..I've long been tempted!
Jon Larson
CD30 PERI
San Francisco Bay
Steve Alarcon wrote: We recently accquired a 1983 CD30, and have found that the existing RH 15x10 propeller causes the boat to severly turn to
port when backing. Limiting the throttle helps a bit, but backing in a straight line or to starboard is near impossible. The gentleman who surveyed the boat at purchase suggested a 3 blade prop for improved power transmission, and a friend (tug boat captian) said a 3 blade would improve the control, but I am concerned with the impact on boat speed under sail. I would
appreciate comments from anyone who has a 3 blade prop or solved the problem some other way.
jon9@ix.netcom.com