Fin Keel? Long Keel? Jeff?

[Jim Cate]

Originally Posted by bob perry

For my The only solution to this, and it's a partial solution, that I have found is the Max Prop. The Max Prop has syemtrical blades. They are the same shape in reverse as they are in forward so they have far beter bite in reverse than the typical asymentrical prop. I did a lot or prop testing years ago and the Max Prop was the clear winner based upon it's low speed and backing performance.

Bob,

Just curious, did you consider any of the other feathering props besides Max Prop? They all have the blade symmetry you mention...

Cheers,

Jim and Ann s/v InatiableII lying Gladstone Qld Oz

[bob perry]

Jim:
Yes, we tried a prop from Australia that was designed to compete with the Max. It was a dissaster. It had a problem with consistantly switching to the reverse mode at low rpm. It's a long story but in the end the US distributor of that prop came up and we took the boat out together. I showed him how the prop would not reverse if the rpm were less than 1000. He said just to keep the rpm's up, I thought that was a bad idea. He then postulated that there must be something odd with the hull design of my boat to kake the prop work that way. That just pissed me off. All the other props tested worked fine. We put that prop aside. A couple of months later we received drawings showing how the blades were to be modified to correct the problem. It was some time ago and I don't recall the name of the prop but it was distributed here by Martec. I'm sure the problem was corrected in time but my own experience with that prop was less than succesful.

[Jim Cate]

Bob,

Thank you for the reply. While I was really refering to the reversing performanace, your experience with the Aussie prop was interesting as well. We switched from a two blade Martec folder to a three blade Aussie Auto-stream on Insatiable I (our old PJ Standfast 36) some years ago, it being WAY cheaper than a Max Prop at that time. The only difference we noted whilst backing up was much better acceleration, not much change in directional control. The shocking thing for us was the 25% increase in fuel consumption, due I believe, to the lack of twist in the blade shape reducing the efficiency... something that must be common to all feathering props. That particular prop had no problems going into reverse mode -- perhaps it was a later model than the one that you encountered -- and was still working fine 5 years later when we sold the boat.

Incidentaly, that experience lead us to put a Flex-o-fold 3-blade folder on Insatiable II when we bought her, and this seems a good compromise to us (much cheaper, too).

Cheers from Jim and Ann s/v Insatiable II

[bob perry]

Jim:
that's very interesting. I did not check fuel consumption when I tested props.
Did the change in fuel consumption reflect a change in required rpm for a given speed?

I have heard nothing but good about that Flex-O-Fold prop.

[malbert73]

I think I read through all replies, but if this has been said already, forgive me-

One really nice advantage with a well-designed full keel (or attached rudder fin if you prefer the wording) is essentially negligible risk of fouling on lines. Seems like a minor deal, but try wrapping a line and then think again. I remember being the designated diver at least twice on our C&C 30 growing up with snagged lines. And with wind or current shifts (like with T-storms) while anchored occasionally the anchor line can get pulled up between the rudder and the keel against the hull, and be held there by the tension of the wind while the boat sits abeam to the wind.

When I sailed in Maine on a Hinckley Bermuda 40, I would hoist sail as soon as possible leaving harbor, lock the prop, and never worry about pots again. Never snagged one, but remember hearing at least 50 buoys bounce off the hull before passing astern. Even have a picture of us sailing by someone else, and if you look closely at the stern you can see a buoy surfacing from the pot we just ran over without incident. Probably could even have motored without worrying because of the aperture protecting the prop.

Same goes for my Luders 33 now on the Chesapeake, especially when nightsailing on the Western shore, where crab pots are very common. Again, for peace of mind I try to sail with a locked prop rather than motor to minimize the risk, but no need for someone on the bow with a flashlight. Have run over a pot or 2 while motoring as well and have never snagged a line.

Has anyone with a "full keel' boat ever wrapped a line on the prop while motoring?

[Amgine]

Well, sort of. I wrapped the dinghy painter while backing in the anchor. No, it wasn't polypro, and it was an exciting moment or three...

[DeepFrz]

I think a full/long keel would really pay off in the event of losing your steering. I doubt that you could balance a short keel/spade rudder boat if the rudder were lost. I think a short keel/spade rudder boat should always carry a "tried and proven" spare rudder.

[Jim Cate]

Originally Posted by bob perry

Jim:
that's very interesting. I did not check fuel consumption when I tested props.
Did the change in fuel consumption reflect a change in required rpm for a given speed?

I have heard nothing but good about that Flex-O-Fold prop.

Bob,

Not having a fuel flow meter meant that all my data was acquired using relatively long term litres/hour data, and hence didn't reflect the many changes in pitch that we went through trying to chase the cause of the loss of efficiency. It really griped me, so I gave it a good shot! And in short I didn't find that it was related to changes in cruising or maximum RPM used.

Incidentally, the extremely easy pitch changing system that the Aussies designed in made that a reasonable exercise: undo a lock nut, turn a screw, tighten the lock nut. Even a decrepit old fart like me cando it free diving!, and that was not possible with the MaxProps of that day. I think that they offer external pitch adjustment now... maybe??

Anyway, the Flexofold is now 5 years old and has performed flawlessly. Only gripe is that the button zincs on the hub must be water-soluble, 'cause they sure go away quickly. Not so with the shaft zincs, so I suspect that it may have to do with the turbulence in that area rather than some change in the boats electrical aura.

Cheers for now from

Jim and Ann s/v Insatiable II

[Wells H]

Hello Everyone,

I have found this thread very interesting. One response and one question:

To Malbert73-The previous owner of my luders 36 (my neighbor) mentioned hitting an unidentifed object causing moderate but repairable prop damage but never was fouled with the warp. The muscongus bay in midcoast maine, where this boat has seen a lot of sailing, can have an amazing number of lobster pots placed. Most/all lobster boats have cages around their prop aperture as do some recreational boats as well. I don't worry at all under sail, but try to avoid running directly over them under power. It is always an aprehesive sight watching a twin screw cruiser or sportfish blasting through the minefield!

A question about modified full keels vs. fin keels with attached rudders-FKAR. I am interested in how poor helm response and subsequent tracking off the wind of a FKAR design ie my luders, cape dorys, etc. occurs as a function of the hull shape. I understand that placing the center of effort for the rudder as far aft as possible increases turning moment and directional stability. However, when I compare elevation line drawings of say a folkboat, seawind II and your typical CCA FKAR boat, the only difference I see is the presence of a counter on the CCA boat. An extension of the rudder rake angle through this counter, cutting the stern off 4-5 feet, gives a similar hull shape to that found on full keel boats with exception to the cutaway fore foot. Since the CCA designs have their rudders positioned at the end of the waterline, why isn't the rudder response, quartering, tracking etc. similar to full keel boat of that waterline length? I realize that the weight in counter increases the polar moment and in certain condition, seas could push on the topside surface area aft of the rudder post, all combated most effectively with the rudder far aft. Maybe I answered my own question when I said you have the directional stability of a full keel boat with that waterline length, in my case a 36 ft. boat with the characteristics of a full keel boat of about 25 ft LWL? Thanks

[sneuman]

Originally Posted by bob perry

Boats like Baba 40's and 30's with the prop in a aperture are the very worse. That aperture seems to act like Cort nozzle and just direct the prop stream to one side making backing up a true adventure. The only solution to this, and it's a partial solution, that I have found is the Max Prop. The Max Prop has syemtrical blades. They are the same shape in reverse as they are in forward so they have far beter bite in reverse than the typical asymentrical prop. I did a lot or prop testing years ago and the Max Prop was the clear winner based upon it's low speed and backing performance.

I like the way my Tayana 37 goes forward, but it is a %$#!@ to back into a slip!

[camtep]

Snagged a pot while motoring a B40 two years ago. Yes,it can happen.

Originally Posted by malbert73

I think I read through all replies, but if this has been said already, forgive me-

One really nice advantage with a well-designed full keel (or attached rudder fin if you prefer the wording) is essentially negligible risk of fouling on lines. Seems like a minor deal, but try wrapping a line and then think again. I remember being the designated diver at least twice on our C&C 30 growing up with snagged lines. And with wind or current shifts (like with T-storms) while anchored occasionally the anchor line can get pulled up between the rudder and the keel against the hull, and be held there by the tension of the wind while the boat sits abeam to the wind.

When I sailed in Maine on a Hinckley Bermuda 40, I would hoist sail as soon as possible leaving harbor, lock the prop, and never worry about pots again. Never snagged one, but remember hearing at least 50 buoys bounce off the hull before passing astern. Even have a picture of us sailing by someone else, and if you look closely at the stern you can see a buoy surfacing from the pot we just ran over without incident. Probably could even have motored without worrying because of the aperture protecting the prop.

Same goes for my Luders 33 now on the Chesapeake, especially when nightsailing on the Western shore, where crab pots are very common. Again, for peace of mind I try to sail with a locked prop rather than motor to minimize the risk, but no need for someone on the bow with a flashlight. Have run over a pot or 2 while motoring as well and have never snagged a line.

Has anyone with a "full keel' boat ever wrapped a line on the prop while motoring?

[pjablon]

There is very interesting book about yacht design "Seaworthiness: The Forgotten Factor" by C.A. Marchaj.
The author discuss different aspects of hull shape and argue that long keel, narrow and heavy boats are safer in a gale. Since low aspect ratio foil doesn't stall as easy, long keels don't slip sideway at low speed or rough seas and they dump the rolling better.
I can add that way of ballast attachment is important, fully enclosed beeing my favorite.
Full keel can be quite maneuverable, my Columbia 29 has turning circle radius more or less her length, but going reverse is a nightmare.
Piotrek

[Jeff H]

The book 'Seaworthiness, the Fogotten Factor' is based on research that is now nearly 30 years old. Much of that research was based on IOR type forms which were then the standard for light weight boats and reflect issues with IOR typeforms rather more general issues related to light weight, or fin keel boats.

In the period since the book was written, a huge amount has been learned about hull and keel forms, weight and bouyancy distribution, dampening and so on, and much of that research has been incorporated into newer designs that are more seaworthy and offer better motion comfort than the boats than the IOR era. In the case of the better of these new designs, proper hull shape, keel formsm and weight distribution pretty much invalidate the advantages of a full keel in terms of seakeeping, or motion comfort in extreme conditions.

Also, for what it is worth, just to clarify the semantics on this point, Columbia never made a full keel vessel. The first generation Columbia 29 that you own, has a radically cut away foorefoot and raked rudder post. In its day, using the definitions of that era, it would have been considered a fin-keel with attached rudder. Today, it would be considered a long keel, with attached rudder. That is why (vs a full keel) it has reasonable manueverability in the forward direction with adequate speed on, albeit at a lot of drag as compared to a fin keel with a detached rudder.

Respectfully,
Jeff

[Pathfinder]

Jeff's treatise is fabulous on keels. Not much here about heaving to in a storm. The rumor is that you can't heave to effectively with a fin keel boat in a heavy gale. I suppose I'll just have to experiment.

[Amgine]

The primary thrust of Marchaj's work, if I undestood it, is that racing rules compliance and optimization directly penalize sea worthiness.

Jeff H: Are you suggesting 'modern designs' do not take into account equally modern sailboat ratings systems? It seems to me there are a fair number of flat-bottomed fat-sterned over-grown dinghies on the market. If you want to only count the boats in the past 10 years or less, I think you'd find they're just as poor a flock in the seaworthiness measures when you look at all the designs, not just a select few of particularly able boats.