Propeller clearance

[Steve Alarcon]

Well, it has taken a year to decide, but I have finally chosen to go to a three blade prop. Now I am about to order one from an outfit in B.C., Canada (Campbell Sailor is the model), and find that I don't know what the aperature (sp?)is, and my manual doesn't indicate. Also, there is a difference between what the commissioning sheet said about the prop (12x12) and what the surveyor said (15x10). Does anyone having a CD30 (or anyone else, for that matter) know what the largest size prop can/should be put on? Experience or opinion on pitch would also be accepted.

Thanks
Steve Alarcon
CD30 TEMERITY
Seattle



alarcon@internetmci.com

[Liz Robinson]

Hi Steve,

We went to a 3-bladed prop when we re-powered, and let me tell you, the extra drag induced while sailing is worth the extra bite while motoring! I am unclear about what you mean by what is your aperture, however the clearance from the tip to the wall of the aperture must be no less than fifteen percent of the diameter of the prop. We had a heck of a time finding the right prop combination and found Michigan Wheel Corporation (616) 452-6941 (fax - 619-247-0227) EXTREMELY helpful. They requested full specs (reduction ratio, et cetera) and came up with a combination that has, thus far, proven to be right on. I don't know your surveyor, but bear in mind that an outfit like Michigan are experts on this very scientific and yet artful craft. We had to enlarge the aperture by 2" due to the new engine's increased RPMs in order to instal the right prop. The 2-bladed prop on the old engine was 14 L 14 and we went with a 3-bladed 14 L 14 which caused cavitation and after only one season the tips were all pitted and eroded. We freaked out needless to say and this is where Michigan Prop set us straight. They suggested we go with a 16 L 11 (decreasing the pitch) but since we didn't want to cut into the hull we settled on 15 L 12. Thankfully, the cavitation problem is resolved. We have a Volvo 2003 engine on a CD 33.

Good luck,
Liz R.

Well, it has taken a year to decide, but I have finally chosen to go to a three blade prop. Now I am about to order one from an outfit in B.C., Canada (Campbell Sailor is the model), and find that I don't know what the aperature (sp?)is, and my manual doesn't indicate. Also, there is a difference between what the commissioning sheet said about the prop (12x12) and what the surveyor said (15x10). Does anyone having a CD30 (or anyone else, for that matter) know what the largest size prop can/should be put on? Experience or opinion on pitch would also be accepted.

Thanks
Steve Alarcon
CD30 TEMERITY
Seattle

[Tom Coons]

Well, it has taken a year to decide, but I have finally chosen to go to a three blade prop. Now I am about to order one from an outfit in B.C., Canada (Campbell Sailor is the model), and find that I don't know what the aperature (sp?)is, and my manual doesn't indicate. Also, there is a difference between what the commissioning sheet said about the prop (12x12) and what the surveyor said (15x10). Does anyone having a CD30 (or anyone else, for that matter) know what the largest size prop can/should be put on? Experience or opinion on pitch would also be accepted.

Thanks
Steve Alarcon
CD30 TEMERITY
Seattle

Steve: The first number refers to the diameter of the prop the second number refers to the pitch. If one decides they want more push (alas more drag when sailing too), you can increase the diameter of the prop, however since the prop is matched to the power of the engine you have to adjust for the increased size so you won't cause ring wear and so on in your engine. The rule of thumb is that for each inch you increase the diameter of the prop you must decrease the pitch by one as well. Thus a 12 x 12 becomes a 13 x 11 or a 14 x 10 or 15 x 9. Everyone wants to go faster under power but remember you are giving up sailing performance eachtime you increase. As far as clearance goes you have to be sure the rudder clears the prop when hard over. If you get too close to the hull with the end of the prop blades you will hear a thumping sound from the water coming off the blades and being tossed against the hull. You don't want to stress things. If your prop is the correct size you should be able to attain the rpms specified in the manual when you are in still water without the wind and current against you. If you can't you need to decrease the diameter size or take out some pitch. Remember you're not going faster than hull speed on still water no matter how much you enlarge your prop. In choppy water you won't attain hull speed. On CD30 that's about 5 or 6 knots. On my CD 31 I went from a 12 x 12 prop up to a 13 x 11 with improved performance. I haven't got the room or courage to go to a 14 x 10. I would tend to doubt the 15 inch figure that you mentioned, but you didn't menton which engine you have so it's not impossible. The size and pitch is stamped in the bronze by the prop manufacturer or you can put a tape measure across it to find the diameter. To determine the pitch you have to take it to a prop shop where they have a machine that reads it. Cape Dorys were designed to be sailing boats -- don't overload your transmission and engine in the quest for speed or push. I've already put three transmissions in mine but that's a story for another day.



taccambria@thegrid.net

[sam]

Your last statement is quite scary considering the cost of transmissions. I wonder why you had to replace yours so often. Is there something we need to 'keep an eye on' so we don't all have a similar situation??

[Tom Coons]

Well, it has taken a year to decide, but I have finally chosen to go to a three blade prop. Now I am about to order one from an outfit in B.C., Canada (Campbell Sailor is the model), and find that I don't know what the aperature (sp?)is, and my manual doesn't indicate. Also, there is a difference between what the commissioning sheet said about the prop (12x12) and what the surveyor said (15x10). Does anyone having a CD30 (or anyone else, for that matter) know what the largest size prop can/should be put on? Experience or opinion on pitch would also be accepted.

Thanks
Steve Alarcon
CD30 TEMERITY
Seattle

;Sam: It's a long story but I can give you the highlights briefly. I have a Universal 21 hp diesel with the Hurth HBW50 transmission. The engine is great and I've never had a lick of trouble with it, but when Universal did the marine conversion it wasn't done very well. The bell housing on mine wasn't lined up over the crankshaft. I had to repin it and drill out the bolt holes to get it lined up. Then the surface of the bell housing wasn't parallel to the engine. I had to have that milled off. Then the shaft of the tranny wasn't perpendicular to the face of the tranny. I had a plate machined to go between the bell housing and the tranny that tapered to correct that misalignment. The tolerances on all these are less than 5 thousandths but mine were over 10/1000s off.

When you have misaligbnments like this it seems to put pressure on the side of the tranny shaft which causes the plate in the tranny to slick up. The first sign of trouble is that the tranny hops out of gear.
You can hold it in but pretty soon it starts to slip. The flex plate between the flywheel and tranny starts to wear egg shaped holes around the springs that are designed to allow a little leeway. Mine finally came apart when I was in Mexico and the pieces flew around and jammed between the flywheel and bell housing and froze up everything so I couldn't run the engine to charge batteries etc.

There is an error in the manual which says to leave the transmission in forward gear when sailing. You can leave it in neutral or reverse, but if you leave it in forward the water on the prop tries to turn the tranny shaft and that works on the plates which also causes them to slick up. I also take it as easy as possible on the tranny. That is to say I don't put it in forward and then put the throttle down to get up to speed. I slowly work my way up to speed so there isn't too much force on the plates. When I shift gears I let the engine come down to a full idle and then quickly snap it into gear and slowly accelerate.

My first transmission was put in by an independent mechanic in Bohicket, South Carolina. He just bolted a rebuilt one on. It lasted two years. The second one was put in by the authorized dealer in San Diego -=- the A to Z yard. That one lasted less than a year. When I got home my local guy who is a machinist as well as a mechanic discovered all these things for me. So far it's been about 5 years with no trouble so I hope I've got it licked. If you have to replace a tranny check everything while you've got it apart. You have to pull the engine to get the tranny out anyway.



taccambria@thegrid.net

[Geoff Safron]

Hi, Steve;
I just took the same plunge, and received my new 13x12 from Michigan Wheel last week; I have a '78 '30 with the original Volvo MD7A (13 hp); Here in Michigan, I'm still a good six weeks from flotation, so I can't speak for its performance yet.
I second Liz' kudos for Michigan Wheel; they put some time into determining the right prop for me.
Good luck! let's trade empirical data in a few months.

Geoff



Pixel179@aol.com

[Jon Larson]

Geoff,

I'd like to ask that you guys keep the empiricals out on the board here. This question seems to come up a lot.

And, PERI will have been in the water three years this summer and surely must be due a hauling soon, and a new three bladed prop is a long over due addition. Your experience would be most appreciated.

Jon Larson
Cape Dory 30 PERI
San Francisco Bay

Hi, Steve;
I just took the same plunge, and received my new 13x12 from Michigan Wheel last week; I have a '78 '30 with the original Volvo MD7A (13 hp); Here in Michigan, I'm still a good six weeks from flotation, so I can't speak for its performance yet.
I second Liz' kudos for Michigan Wheel; they put some time into determining the right prop for me.
Good luck! let's trade empirical data in a few months.

Geoff

jon9@ix.netcom.com

[Steve Alarcon]

Geoff,

Thanks for the great info! I also have the MD7A. Do you have the WALTER V-drive also, and is your reduction 2:1? With your info, I may be able to speed the process up a bit.

Thanks
Steve Alarcon
CD30 Temerity
Seattle



alarcon@internetmci.com

[Geoff]

Steve;
Yes to V-drive; reduction...hmmm, dunno! Michigan Wheel asked for my full-throttle rev's; Just by coincidence, I also had just had a compression test and furnished those numbers to them; they seemed glad to have the data, but I got the impression that it wasn't crucial. Again, I'll know how well this works first week of June. Oh, completely unrelated question: do you have a dodger and/or bimini on your 30? I intend to build my own, and I'm looking for designs...

Jon;
You betcha, I'll share the results with the Club.



Pixel179@aol.com

[Jon Larson]

Geoff,

I've had a dodger on PERI since I've owned her. I had it made by Paul McSorley, now in the Carolina's someplace. It was made to be folded down, something I never did except in the most hot of weather when air flow was more important than shade. My local CD30 friend had one made here and it's a permanent "up" installation and when the time comes
to replace PERI's (not that far off) I'll have one made like hers. She has solid stainless steel supports for hers and stainless steel handholds on the rear of the dodger and on the sides...both great ideas.

I had an opening window in mine, I almost never opened it and all it did was leak through the zipper and it seemed to drip unerringly down the open companion way on drippy days. I had to replace the clear window recently and had the sailmaker make it a solid piece. Much better that way, I believe.

Mine doesn't extend very far back over the cockpit, next one that is non folding will come back further for better protection from spray and sun, probably as far back as the winches. Some would find that a bit far, I like the protection. You also need to watch where the sides of the dodger go, you really do wish to have a decent swing on the winch handles.

The one that Paul McSorely did is taught as a drum head, that seems to add a great deal of strength to the stainless steel support ribs, I hope you sew well!

Good luck, whatever you do, I think you'll never regret having a dodger of some kind.

And thanks for the info to come on the propellor!

Jon Larson
Cape Dory 30 PERI
San Francisco Bay

Steve;
Yes to V-drive; reduction...hmmm, dunno! Michigan Wheel asked for my full-throttle rev's; Just by coincidence, I also had just had a compression test and furnished those numbers to them; they seemed glad to have the data, but I got the impression that it wasn't crucial. Again, I'll know how well this works first week of June. Oh, completely unrelated question: do you have a dodger and/or bimini on your 30? I intend to build my own, and I'm looking for designs...

Jon;
You betcha, I'll share the results with the Club.

jon9@ix.netcom.com

[Steve Alarcon]

Geoff,

Thanks for the additional info. I'll keep you and the rest of the CCDO gang informed.

We don't have a dodger; maybe next year (I still have to install the radar I purchased at the boat show this year). Another fellow at our marina with a CD30 does; his has stainless frame, canvas/leather handles attached at the outside with the typical CD Brown Sunbrella fabric. I would not be one to suggest that you couldn't make one, but my view is that it may be a significant challange. All of the dodgers I have seen seem to have critical measurements that allow them to fit like a glove (a tight one, at that). If you choose to proceed, you might want to check out Karen S. Lipe's book THE BIG BOOK OF BOAT CANVAS, published by International Marine in 1988 ISBN 0-915160-35-8. It contains plans, material lists, directions, suggestions, hints, admonishments and consolations.

Good luck, and thanks again!

Steve Alarcon
CD30 Temerity
Seattle



alarcon@internetmci.com

[Jerry]

Well, it has taken a year to decide, but I have finally chosen to go to a three blade prop. Now I am about to order one from an outfit in B.C., Canada (Campbell Sailor is the model), and find that I don't know what the aperature (sp?)is, and my manual doesn't indicate. Also, there is a difference between what the commissioning sheet said about the prop (12x12) and what the surveyor said (15x10). Does anyone having a CD30 (or anyone else, for that matter) know what the largest size prop can/should be put on? Experience or opinion on pitch would also be accepted.

Thanks
Steve Alarcon
CD30 TEMERITY
Seattle

_____
Steve, I've got an '84 CD30 with the Universal 14hp engine. It has a 3-blade 12X11 Michigan prop and seems to be seriously under powered. Based on some of the other responses to your message, I guess I should look into possibly getting a bigger prop.