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  #1 (permalink)  
Old 06-23-2006
Nonkjo Nonkjo is offline
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Draft minus keel depth on Cape Dory 28?

I'm interested in a Cape Dory 28. I am interested in this boat because it appears that it can do it all, even long distance cruising when I get to that point.
I was wondering if anyone out there can tell me the draft of this boat minut keel depth. I was doing some research and as I understand, a boat with an angle of vanishing stability less than 140* might not right itself if capsized. The reviews say thet the CD 28' is a rugged and seaworthy full keel boat capable of making blue water passages so I was curious as to what this number would be for it.

Thanks,
James
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Old 06-23-2006
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Jeff_H Jeff_H is offline
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The Cape Dory 28's are nice little boats. I actually like the Cape Dory 28 more than most of all of the Cape Dory line. For their day they were wholesome designs with a reasonable amount of waterline length and a nicely modeled underbody.

To me they are complex boats to classsify in a lot of ways.

I don't think of them as good daysailers or good boats to learn to sail on. I think that ideal daysailors and boats to learn to sail on are responsive so that you can feel the full richness of the sailing experience, the subtle clues to the impact of wind and water or response to small sail trim or steering changes.

I don't think of them as being very good coastal cruisers. Their excessively high weight and small sail plan do not make them very handy in the changeable conditions and lighter air typical in coastal cruising. I think that this is a personal preference thing, but I think that coastal cruisers need to accel in a wider range of conditions, and offer good enough performance to run for cover or beat off of the more frequent hazzards found inshore. In my mind, on that basis boats like the Cape Dory 28 fail my sense of a what a good coastal cruiser should be.

By the same token, my opinion of them is complex when I think about them as offshore cruisers. These are good boats in a lot of ways for offshore use. If you start out saying that you want to go offshore in a 28 footer, these boats have reasonably good tankage and a reasonably good layout for a boat that size, but small for any serious cruising. If I remember the interior correctly, it would be pretty easy to adapt the main cabin settees to good seaberth. It would take some pretty serious alterations to the interior to install more than a single burner gimballed stove or a proper navigation area. Most have an engine that is way too small for a Cape Dory that is fully loaded for cruising. But the price of the large tankage is that most of the other storage is quite high above the waterline.

While I would hate to re-ignite the discussion of the definition of a fin keel vs Full keel, which has taken place on this site many times before, I would like to touch on the comment that the Cape Dory 28 is a "full keel" boat. It is not. As I have pointed out, that the past, histroically the defintion of a fin keel was a "A keel whose length on it bottom is 50% or less of the LOA or length of sail plan which ever is longer". By that definition the Cape Dory 28 would be a fin keeled boat with an attached rudder.

As has been pointed out in prior discussions, this definition has dropped out of popular use, and to most people who have started sailing in recent decades, these boat are not fin keelers. I think that the general consensus was that boats like these were moderately long length keels. Whatever you call them, they certainly are not Full Keeled boats (I suggest that you look at the Bristol Channel Cutter or the Westsail 32 if you wish to see what a full keel actually looks like.)

In any event, whatever you call the keel on the Cape Dory 28, they have a sharply cut away forefoot, and a rudder post that is quite far forward in the boat, and an attached rudder. This results in boat that does not tarck all that well and which can develop quite a weather helm. What is nice about the Cape Dory is that you can reduce sail area and help balance the helm. But that occurs at windspeeds that would further slow the Cape Dory below newer offshore cruisers (Take a look at the Southern Cross for example) or boats with hulls and rigs that can benefit from better sail handling gear.

This brings us back to your original question. In waves large enough to roll a boat, it is generally thought that a limit of positive stability as loaded in the range of 125 degrees should be adequate. Which is not to say that there this is the only LPS that you see recommended. I have seen recommendations as high as 145 degrees, but these high limits of positive stability generally refer to LPS based on a 'dry' loading. In big boats there is comparatively little difference between an LPS based on the dry loading vs fully loaded. But in smaller boats, like most of us around here seem to sail, the vertical center of gravity rises pretty sharply when the boat is fully loaded for offshore cruising. This is especially true boats like the Cape Dory where a lot of the bulk storage is above the waterline.

If I had to guess, based on stability plots that I have seen for similar boats, I would expect the Cape Dory to have a limity of positive stability somewhere in the 120 degree range. In the CD 28's favor when it comes to LPS is a reasonablely deep draft, and high freeboard and cabin structure for a 28 footer. The ballast to weight ratio is also reasonably good for a boat of this era but would be be absolutely dismal when fully loaded for offshore use. Another negative re LPS is the Cape Dory 28's rig which is very heavy for a 28 footer and while pretty sturdy, makes a good ballast keel when inverted.

The other component of inverted stability is how stable they are inverted and the CD 28 is quite beamy and the beam is carried quite far towards the ends of the boat giving the boat a bit more inverted form stability than one might expect. This is partially offset by the large volume of the cabin structure.

Regards,
Jeff
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Old 06-24-2006
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hellosailor hellosailor is offline
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http://www.toolworks.com/cdsoa/cdinfo.html has specs on the Cape Dory boats, and points to

http://www.image-ination.com/sailcalc.html which lists the Cape Dory 28 specs for stability, etc.

Questions of seaworthy or bluewater capable...I don't know the boat but those are areas where experience, rather than numbers, will mean more to you. Figure whatever boat you start with, you may want to change at least once before taking off around the globe. Personal decisions about sail balance, seakindly motion, proper layouts and such.
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Old 06-24-2006
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I am afraid that there is nothing on Carl's Calculator http://www.image-ination.com/sailcalc.html that actually tells you anything meaningful about stability, or motion comfort.

Carl’s calculators provides a useful service but the Capsize Screen Formula and the Motion Comfort provide no useful information in evaluating a boat for either motion or stability. I know that I have explained this on this forum before but here it is again, both of these formulas were developed at a time when boats were a lot more similar to each other than they are today. These formulas have limited utility in comparing boats that otherwise are very similar.

Neither formula contains almost any of the real factors that control motion comfort or seaworthiness. Neither formula contains such factors as the vertical center of gravity or buoyancy, neither contains weight or buoyancy distribution, and neither contains any data on dampening all of which really are the major factors that control motion comfort or likelihood of capsize. Weight alone has no bearing on motion comfort and stability.

I typically give this extreme example to explain just how useless and dangerously misleading these formulas can be. If we had two boats that were virtually identical except that one had a 500 pound weight at the top of the mast. (Yes, I know that no one would install a 500 lb weight at the top of the mast but teak decks, heavy decks, wooden or steel spars or at the other end of the boat a deep bulb keel vs an equal weight fin can easily have that kind of impact.) The boat with the weight up its mast would appear to be less prone to capsize under the capsize screen formula, and would appear to be more comfortable under the Motion Comfort ratio. Nothing would be further than the truth. That is why I see these formulas as being worse than useless.

Jeff
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Old 03-09-2007
chknlips chknlips is offline
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Cape Dory 28

I am not sure but I may have more sea miles on a Cape Dory 28 than anyone I have ever chatted with... My wife and I cruised the Pacific from Astoria Oregon to Hawaii and then the South Pacific (Marquesas) and back on our Cape Dory 28.

I can't say enough good about the boat's sea kindliness.

If there are drawbacks, it is the interior size ( I am 6' 4" tall) and possibly my opinion that has formed over the years of sailing in the ocean that fiberglass is just not the medium I would choose unless you are staying in what is referred to as the 20-20 regions of the ocean. (20 degrees north to 20 degrees south latitude).

However, again, I have never sailed a production boat with such a combination of stability and agility than the Cape Dory 28. The only other boat in the line that retains the perspective of the 28 is the 36 and though I have not sailed one, I would expect it to be very similar if not better in the ocean due to sheer physical size.

The hull was stout and the rig was sufficient to survive some pretty severe weather.

Be sure if you get one to acquire a heavy weather 130 genoa and a healthy boom vang.

Sail safe,
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