CD 31 Propeller

[D Dorle]

We have a Cape Dory 31 with an original equipment 2-bladed prop and a Universal 25hp diesel. We sail on Lake Superior and occasional the chop (rarely a roll) can get fairly large (5-6+). When sailing to windward, the boat performs well, but when motoring, the forward motion can be as little as 1 knot.

A second issue, more serious: The boat will not motor to port in reverse, but rather the bow readily holds to port and even the slightest starboard breeze will cause it to slip further to port which makes navigating in a marina difficult to say the least. I have tried everything including quick bursts of the throttle combined with shifting to neutral between bursts while the wheel is cranked fully to port, but nothing seems to work. The prop, while original, is in pristine condition -- no chips, scrapes, dents -- nothing.

I did have the engine pulled and rebuilt three years ago so I have often wondered if its re-installation could have something to do with this, but I've been assured by our shop staff that all is as it should be regarding the shaft, rudder, etc.

They have said, however, that I might want to replace the 2-blade prop with a 3-blade prop -- but cannot guarantee that that will fix the problem of not being able to go to port in reverse -- so I'm reluctant to buy a new prop.

Please let me know if you have experienced this (not going to port in reverse) and whether a 3-bladed prop may help. Also, will a 3-bladed prop give me the thrust I need motoring into heavier seas and whether it will create too much strain on the engine regardless of my point of sail.

Thank you, David D.

[Frenchy]

Hi there, David. The problem of directional control in reverse is very common with our boats. Usually, it's the wind direction that
determines where the boat will go in reverse. When I pull away from a little narrow landing dock here in New Bedford, the
prevailing southwest breeze always pushes the bow away from the dock. I have to warp the boat around the dock and head out
bow first. So I wouldn't be too concerned about the reversal issue.
As for a three-bladed prop, that's a good idea, I think. It should give you more power. In strong winds and waves, though,
you will still be going slow. In Buzzard's Bay, heading into strong gusty winds and four-foot waves, I could barely make 2 knots.
A couple of years ago, I bought a Featherstream three-bladed prop which I'm pretty happy with. There's more power in
reverse, but the directional control is still not there. - Jean

[gonesail]

have you heard of the campbell sailor propellor? it is reported to reduce prop walk and have better performance.

[John Stone]

There is not a full keel boat with an attached rudder afloat that will back under complete control. Not unless it has a bow thruster and I won't even go down the path of all the reasons a bow thruster is a bad idea. Props are not the solution. You'll be disappointed if you think you'll get any useful improvement.

Anyway, my boat is even worse with the prop behind the rudder but we are learning her ways. We warped extensively when we were engineless and we do the same now.

However, there is a lot you can do using prop walk, spring lines, smart placement of fenders etc. Chapman's and some of the old pre 70's boating books have a fair amount of info and diagrams how the old timers used warping lines to gain control for getting off docks and out of narrow slips, etc. Look at it as a challenge and beat your chest when you pull it off smartly!

Happy sailing.

[jen1722terry]

We have a 3-blade prop on our 31. Seems to drive the boat well enough into head winds/seas.

As for backing down, we'll, it can be an adventure if one doesn't mind the wind and current.

Cheers

Jenn and Terry

[wikakaru]

I concur with the others who have said that you should plan all your reverse-gear maneuvering with the anticipation that the boat is going to back stern towards the wind with the bow trailing off downwind. The stronger the wind the more pronounced the effect. As others have mentioned, using warps and spring lines in tight quarters to maneuver the boat until it is pointed in the direction you want to be motoring in forward gear is the safest choice. Don't expect a different prop to make a whole lot of difference in your ability to control the boat while backing.

You will definitely get more thrust to push you through big seas with a 3-bladed prop compared to a 2-bladed prop, but the extra blade can also drastically affect sailing performance. I owned a boat that had a fixed 3-bladed propeller with "fat" blades on the prop (not the skinny sailboat prop blades), and another with a 3-bladed feathering Max-Prop. Both had great power in forward, and the Max-Prop was especially speedy under sail. The fixed-blade prop was literally and figuratively a drag. If you can afford the big bucks for the feathering prop, it is well worth it.

If you do re-prop, be especially careful about aperture tip clearance and prop pitch, which will both be different from your 2-bladed prop. Consult a good prop shop to get the numbers right, and even they make mistakes. That's one reason why a feathering prop that offers different pitch settings is nice--if the pitch is off it is a fairly easy matter to change it. One of the drawbacks of feathering props is they may require shortening the prop shaft to fit into the aperture.

Smooth sailing,

Jim

[mgphl52]

Another option for less drag is the Campbell Sailor prop which is considerably less expensive than a variable pitch prop. These are 3 bladed props but designed to cause much less drag. Before I switched, the 3 blade Michigan prop, when not allowed to free-wheel, could easily cut our speed over 1.5 knots. There is hardly any difference with the Campbell Sailor locked in reverse vs able to free-wheel in neutral. Because of that, I routinely lock in reverse to get the mono-shift out of the way now.

[sachemgfp]

We replaced our 2 blade prop with a 3 blade fixed prop. We noticed some improvement going forward against head seas. No improvement in reversing it just takes practice with the prop walk. We attended a Cape Dory gathering in Newport and a fellow owner told us to keep a line long enough to walk the boat out of a difficult slip and don't feel bad about using this technique it beats gelcoat repairs. We would lope the line around the dock cleat going it in thru the gate and use the winch to keep tension on the line while backing out. We still usr\e this technique tofay with poly line from Home Depot, it floats so no problem with snagging the prop.

At to losing speed with the engine off we put the engine in reverse thereby locking the prop so it doesn't free wheel.

Hope this helps.

Sachemgfp CD 31 # 029

[sgbernd]

When I re-powered, I went from the stock 2 blade to a modern 3 blade. While I like the smoother (less vibration) of the 3 blade, I can't say it improved the reverse performance as I had hoped. If this is your goal, I fear you will be disappointed.

Personally, I have convinced myself that I cannot control the boat in reverse under power. Consequently, I never enter any situation where I can't exit forward or control the bow direction by standing on the dock, using a boot hook, spring line, etc. For example, when exiting the slip, I start the engine, walk on the dock guiding the bowsprit, shove her off firmly with the bow pointed in the proper direction, clamber aboard and hit forward and give her some power.
(One of these days, as I age, I'll probably fall into the water and the boat will drift away without me, but it has worked well for the last 20 odd years.)

If you try to back her in/out of the slip, the bow will follow the wind and bad things happen. When dealing with difficult or unfamiliar docks, downwind slips, cross currents, etc., have your boat hook/pole handy and be prepared to fend. I think of "reverse" as a way to bleed off forward speed or set an anchor, but not something which can actually ever be used to go backwards. Once you get into this mindset, you will have fewer docking "adventures" and a lot less stress.

-Steve

[John Stone]

When I re-powered, I went from the stock 2 blade to a modern 3 blade. While I like the smoother (less vibration) of the 3 blade, I can't say it improved the reverse performance as I had hoped. If this is your goal, I fear you will be disappointed.

Personally, I have convinced myself that I cannot control the boat in reverse under power. Consequently, I never enter any situation where I can't exit forward or control the bow direction by standing on the dock, using a boot hook, spring line, etc. For example, when exiting the slip, I start the engine, walk on the dock guiding the bowsprit, shove her off firmly with the bow pointed in the proper direction, clamber aboard and hit forward and give her some power.
(One of these days, as I age, I'll probably fall into the water and the boat will drift away without me, but it has worked well for the last 20 odd years.)

If you try to back her in/out of the slip, the bow will follow the wind and bad things happen. When dealing with difficult or unfamiliar docks, downwind slips, cross currents, etc., have your boat hook/pole handy and be prepared to fend. I think of "reverse" as a way to bleed off forward speed or set an anchor, but not something which can actually ever be used to go backwards. Once you get into this mindset, you will have fewer docking "adventures" and a lot less stress.

-Steve

That's about as well said as can be stated. We subscribe to the same philosophy. We drive the Far Reach into her slip forward. When the wind is light enough we use s a long line and flip her around and back her in. We use warping lines and fenders. It's a timeless and seaman way to handle a full keel boat.