Hull Stability

[Brad Meilink]

I'm looking for some information on the hull stability for my CD32 sloop. Info on the 31, 33 or 330 would be good enough. Reasonable opinions are also welcome.

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the ride. Yes, I need to be more considerate of the comfort level of the crew (wife, kids 7&8 who all love the boat), but some number as to where the risk significantly increases has been requested and would give them all great comfort. (Is it 40deg, 50, more, etc)

To those who will surely point out that heel exceeding 25 deg or so is detrimental to speed, yes I know. We reef down when the wind pipes up and stays there, trimming the sails accordingly. It is the gusts that cause short periods of excessive heeling that are creating the issues at this time.

Thanks for your input.

(Catherine - Any special words of wisdom from a fellow CD32 sailor?)

Brad

CD32 #4
Magdelana



bmeilink@shentel.net

[Steve Alarcon]

Brad,

A naval arch. by the name of John Holtrop has put together an Excel spreadsheet that calculates stability, hull speed and stuff like that, and also applys some "fuzzy logic" principles in ascertaining which designs are the best for cruising. He has calculations for about 700 boats, as I recall. There are one or two minor errors in specifications, but they are easily corrected. While this may not specifically address your question, it will give you a starting point for comparison with other CD's (the various models seem to have fairly significant different handling characteristics which by the way).

You can get the apreadsheet via www.iwvisp.com/download/pub/spreadsheet/saildata.xls

Steve Alarcon
CD30 Temerity
Seattle



alarcon@internetMCI.com

[Duane Yoslov]

Brad,

Recently, we took our 330 fairly close to the limit unintentionaly. We were heading out of Sausalito into the SF Bay in literally 0 kts of wind. I could see that there was plenty of wind on the main bay so I conservatively put up a single reefed main and a staysail. As we poked our nose into 'Hurricane Gultch' we were blasted with a 45 kt. gust. I can hear the groans of all of those who believe this must be an exageration but I've confirmed with a couple of other boats that were out that day. Anyway - it's the closest to a knockdown that I ever had. I immediately tried to head up but the heel increased so quickly that the rudder lost its bite. Standing on the side of the cockpit combing - I could see that the ports were under water and the cockpit had water rushing in. The blast of air left as quickly as it had come and we sailed on our merry way in the steady 28kt. breeze.

In a way this account could be used to comfort your crew. As a boat begins to heel - more and more air is being dumped from the sails and eventually the boat will begin to right itself unless the wind does not relent - in which case it's time to reduce sail. When I have lesser experienced crew, I like to sail a little more conservative and reef ahead of time so that they don't get nervous and we can enjoy the sail and still make relatively good headway.

I've owned 3 Alberg designed boats and all of them had a relatively tender initial moment but then they dig in and charge ahead. Rest assured, your crew is sailing on one of the finest, sturdiest sailboats ever designed.

Duane Yoslov
CD330 #142
Mystic

I'm looking for some information on the hull stability for my CD32 sloop. Info on the 31, 33 or 330 would be good enough. Reasonable opinions are also welcome.

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the ride. Yes, I need to be more considerate of the comfort level of the crew (wife, kids 7&8 who all love the boat), but some number as to where the risk significantly increases has been requested and would give them all great comfort. (Is it 40deg, 50, more, etc)

To those who will surely point out that heel exceeding 25 deg or so is detrimental to speed, yes I know. We reef down when the wind pipes up and stays there, trimming the sails accordingly. It is the gusts that cause short periods of excessive heeling that are creating the issues at this time.

Thanks for your input.

(Catherine - Any special words of wisdom from a fellow CD32 sailor?)

Brad

CD32 #4
Magdelana

yoslov@aol.com

[Catherine Monaghan]

Brad,

You may want to visit <A HREF="http://eightsea.com/eightsea/boatcalc.shtml">The Eigth Sea</a> and check out their boat calculator. Here you can calculate your boat's theoretical maximum hull speed, its displacement to length ratio, its sail area/displacement ratio, and its capsize screening formula.

You can use the specifications for the Cape Dory 32 found at this site at <A HREF="http://www.toolworks.com/capedory/specs ... ifications: Cape Dory 32</A>

You'll find that your Cape Dory was overbuilt and is very seaworthy.

catherine_monaghan@merck.com
CD32 Realization
Raritan Bay

I'm looking for some information on the hull stability for my CD32 sloop. Info on the 31, 33 or 330 would be good enough. Reasonable opinions are also welcome.

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the ride. Yes, I need to be more considerate of the comfort level of the crew (wife, kids 7&8 who all love the boat), but some number as to where the risk significantly increases has been requested and would give them all great comfort. (Is it 40deg, 50, more, etc)

To those who will surely point out that heel exceeding 25 deg or so is detrimental to speed, yes I know. We reef down when the wind pipes up and stays there, trimming the sails accordingly. It is the gusts that cause short periods of excessive heeling that are creating the issues at this time.

Thanks for your input.

(Catherine - Any special words of wisdom from a fellow CD32 sailor?)

Brad

CD32 #4
Magdelana

catherine_monaghan@merck.com

[Jim Hollister]

I am interested in this post because my crew gets anxious sometimes, on Lake Michigan, because they see the skipper's anxiety! For the CD 25, what is the ideal angle of heel? What is the point beyond which I should be nervous -- or quickly reduce sail?
Jim Hollister

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the ride. Yes, I need to be more considerate of the comfort level of the crew (wife, kids 7&8 who all love the boat), but some number as to where the risk significantly increases has been requested and would give them all great comfort. (Is it 40deg, 50, more, etc)

To those who will surely point out that heel exceeding 25 deg or so is detrimental to speed, yes I know. We reef down when the wind pipes up and stays there, trimming the sails accordingly. It is the gusts that cause short periods of excessive heeling that are creating the issues at this time.

Thanks for your input.

(Catherine - Any special words of wisdom from a fellow CD32 sailor?)

Brad

CD32 #4
Magdelana

jjhollister@excel.net

[Bruce Barber]

Brad

For a quick check, take a look at the freeboard when you're heeled over by the gust. If the mean waterline is not yet at the deck edge, the boat can still absorb more heeling moment. If the deck edge is awash, it's approaching the peak of its righting arm curve. That's where "the risk [of a knockdown] significantly increases," if the wind stays at the gust level or gets stronger.

Bruce Barber

I'm looking for some information on the hull stability for my CD32 sloop. Info on the 31, 33 or 330 would be good enough. Reasonable opinions are also welcome.

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the r

bbarber38@aol.com

[Matt Cawthorne]

Brad,
There is a really excellent book called 'Seaworthiness: the forgotten factor' by C.A. Marchaj. I suggest that you read it. You will not find exact numbers on your boat, but it will help you better understand stability. It does not boil down to one single number. It will make you feel good about having bought a full keel boat.
As for the capsize screening number, it is just that. A screening number. It will keep you from buying a really bad boat, but if you are trying to consider two boats with similar screening numbers, the one with the higher screening number will not necessarily have a higher smooth water capsize threshold. One of the boats that Patricia and I were considering buying was a Tayana 37. We chose the CD-36, but it conserned me that the CD-36's capsize screening calculation was somewhat less than the Tayana 37's. I later read that the calculated range of stability (not the screening formula) was something like 129 degrees for the CD-36 and only 113 or 115 for the Tayana. Be carefull of reading too much into a single number.
For what it is worth I would suggest that you reef sooner. I don't think that you will ever capsize your boat, but if you scare your crew you may end up sailing by yourself. Also you are loading your rig very heavily for not much extra speed (if any), potentially stretching out your sails, and making it very hard for anyone to use the head.

Enjoy your boat.
Matt

I'm looking for some information on the hull stability for my CD32 sloop. Info on the 31, 33 or 330 would be good enough. Reasonable opinions are also welcome.

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the ride. Yes, I need to be more considerate of the comfort level of the crew (wife, kids 7&8 who all love the boat), but some number as to where the risk significantly increases has been requested and would give them all great comfort. (Is it 40deg, 50, more, etc)

To those who will surely point out that heel exceeding 25 deg or so is detrimental to speed, yes I know. We reef down when the wind pipes up and stays there, trimming the sails accordingly. It is the gusts that cause short periods of excessive heeling that are creating the issues at this time.

Thanks for your input.

(Catherine - Any special words of wisdom from a fellow CD32 sailor?)

Brad

CD32 #4
Magdelana

Mcawthor@bellatlantic.net

[Mike Everett]

I agree with Matt Cawthorne that C. A. Marchaj's "Seaworthiness" is an excellent book; it has the best explanation of hull stability I've ever read. I'd recommend this book to anyone who's looking for an understanding of the forces operating on a sailboat.
In fact, the reason my wife and I chose to own a Cape Dory is due to my having read "Seaworthiness" while we were looking for a sailboat. The Alberg Cape Dorys exemplify Marchaj's characteristics of ideal seaworthiness.



everett@megalink.net

[Jon Larson]

Brad,

Speaking for my three Alberg designed Cape Dorys, I don't think you have anything to worry about regarding stability for any of these boats. The non Alberg Cape Dory's may be something different regarding some end point of stability or recovery from a knockdown, but all the hulls are strongly built and the rigging and masts are above industry average for strength. In one correspondance with Larry DeMers, he told me of a squall whose initial blast literally put his spreader in the water on his Cape Dory 30, but up she came with everything standing.

It's been my experience that beamy boats such as Catalina 30's, Lancers or Newport 30s will actually slow as they heel beyond some modest point. My modest experience in these boats also causes me to believe that when a real puff does come, the rudder in a fat boat is lifted enough that the boat may round up regardless of what the skipper wants, this can be a real thrill when this happens near a jetty such as entering Coyote Point Marina! My less beamy Cape Dory 30 seems to just put her shoulder down and push when a puff comes and even with the life line stanchions plowing through the water she seems to exhibit no slowing. While the weather helm does increase, she stays in control. (For the conditions on San Francisco Bay, I have replaced all the standing rigging, by the way. There is a fatigue factor that occurs over time. I think this is recommended for all boats every 10 to 15 years).

In summary, I don't think you are going to break anything by sailing as you do, I also don't think you are going to go beyond any point of unrecoverable stability with wind alone. The chances are that if things get too extreme, the boat will round up for you and indeed protect itself, though how far you have to go in an Alberg design is unknown to me. If you enjoy sailing a bit on the wild side, do it. (I'm a cruiser here, that's not my style!) No matter what, regularly check the rigging and swages for fatigue.

Jon Larson
Cape Dory 30
San Francisco Bay

I'm looking for some information on the hull stability for my CD32 sloop. Info on the 31, 33 or 330 would be good enough. Reasonable opinions are also welcome.

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the ride. Yes, I need to be more considerate of the comfort level of the crew (wife, kids 7&8 who all love the boat), but some number as to where the risk significantly increases has been requested and would give them all great comfort. (Is it 40deg, 50, more, etc)

To those who will surely point out that heel exceeding 25 deg or so is detrimental to speed, yes I know. We reef down when the wind pipes up and stays there, trimming the sails accordingly. It is the gusts that cause short periods of excessive heeling that are creating the issues at this time.

Thanks for your input.

(Catherine - Any special words of wisdom from a fellow CD32 sailor?)

Brad

CD32 #4
Magdelana

jon9@ix.netcom.com

[JB]

I don't think that there is any question about the stability of the Cape Dories. All of them are some of the most stable boats around and provide a secure vessel to sail on. I do think that we are missing some of the point about your crew's concern. Don Casey and Lew Hackler's new book, Sensible Cruising, brings up some good points about keeping your crew happy to allow you to cruise more. Quoting from a section about you and your family aboard,specifically your wife, "If she does not want to go, you are not going at all."(pages 28-31) If you make it more enjoyable for them and let them slowly get used to the greater angle of heel, then you all will have more fun sailing together. I know from first hand experience that your cruising days, or married days, are limited if your wife is not comfortable with the style of sailing that you are doing. Good luck with a happy medium.

JB

[Brad]

To all whom have responded to my questions:

Thanks!

I really appreciate the comments, advice, and concern for myself, crew and boat. I'm working on getting a copy of the book recommended by Matt and Mike. Thank-you Catherine for your response as well. I read this list religiously and have learned a lot in a short time! (You listening Walt?)

I'm boning up on my sail trim, which should help a lot and will back off the mainsheet a little earlier (and the traveler) to ease the heel. Hopefully total harmony will return to the decks of Magdelana.

Just one comment. We are water and boat people having sailed Sun-Fish, Hobies, and 15 years of windsurfing. Our Cape Dory is a big step up from that level but not one into totally unfamiliar territory. My family is not uncomfortable with the heel of the boat. What is causing concern is "How much heel is too much for this boat?" Having some number, whatever it is, to go by would alleviate their concerns. That said, maintaining moderate heel is faster and less strenuous on both boat and crew, making for a more enjoyable experience. That's the reason we are there in the first place!

Brad

I'm looking for some information on the hull stability for my CD32 sloop. Info on the 31, 33 or 330 would be good enough. Reasonable opinions are also welcome.

Here is the issue. We sail the Chesapeake Bay near Baltimore. During the summer I fly a 150 genoa most of the time, not bothering to reef unless the wind picks up and stays up over 18-20 kts. The heel of the boat is about 20-25 degrees. When a gust comes along (+20kts) and the boat heels over 30+ degrees, my crew becomes very anxious, concerned about the possibility of a knock down. My response is to relax and enjoy the ride. Yes, I need to be more considerate of the comfort level of the crew (wife, kids 7&8 who all love the boat), but some number as to where the risk significantly increases has been requested and would give them all great comfort. (Is it 40deg, 50, more, etc)

To those who will surely point out that heel exceeding 25 deg or so is detrimental to speed, yes I know. We reef down when the wind pipes up and stays there, trimming the sails accordingly. It is the gusts that cause short periods of excessive heeling that are creating the issues at this time.

Thanks for your input.

(Catherine - Any special words of wisdom from a fellow CD32 sailor?)

Brad

CD32 #4
Magdelana

bmeilink@shentel.net

[Dana]

Brad,

I think you have answered much of your own question, i.e.

Normally:
15-20 degrees
Point of too much:
25 degrees

Now....what action to be taken for the direction of sail:

Close hauled:
Take advantage of the increased wind puff, head up further for
for the duration of the puff
Off the wind:
Relax the main for the puff duration or reef


Dana




darenius@aol.com

[Dana]

Brad,

Like you, I sail the Chesapeake. But before that time, I sailed Block Island Sound. Just wanted to share some personal observations on the stability issue with changing sea conditions.

Under fairly flat water conditions (1-3 foot, good wind conditions) CD owners probably pay a penality of additional heel as compared to a more flat, wide underbody design. Most noticeable sailing to weather and certainly at the dock. The stiffness of the wider, flatter designs comes from the strong vertical righting momment of the wider hull. That is.....as long as the seas tend to stay fairly flat (1-3 foot). If a more vertical wall of water (wave) were to approach the more modern wider, flatter bottom design boat, the boat heel would tend to follow the slope of the wave surface as the wave passed. This would "jar" the boat so that the deck of the boat was parallel to the vertical front surface of the wave.

If the shape of the wave top is sharp and narrow, the wider design is immediately heeled in the other direction as the wave passes. This is because the boat is now trying to parallel its deck to the reverse wave slope of the passing wave. The same forces which make the wider, flatter design very stiff at the dock and under moderate seas tend to make it very unstable in a steep sea.

The narrower beam design does not get most of its stability from the width of the beam. As a steep wave approaches, the hull remains more vertical as it rides up the front of the wave. As the wave peak passes, the boat still remains fairly vertical. AS the narrow design rides down the back of the wave, the boat will heel in the other direction but the degree of heeling "swing" is not as dramatic. Many people describe the narrow beam boat movement like that one would imagine for a coke bottle floating in the same conditions. It stays fairly vertical even in a rising and falling wave. It does, however, look mightly "rocky" floating in calm water.

Of course, many folks will point out the extreme sea condition where the top of the wave is breaking. Here there is a danger of the boat (both wide and narrow beam) being "thrown" horizontally with the forward force of the breaking wave. The only different between the two boat designs is the angle of heel at the time the boat is thrown. If it is heeling away from the wave (wide design) it will have a great chance of rolling the boat over when the boat hits back down into the water. If the boat is more vertical (narrow beam) when the wave hits there is less likelyhood the boat would roll over as it lands.

So in short, CD owners trade some heeling stability under flat water or moderate conditions for greater stability under steep sea conditions. It is these steep sea conditions which most of us try but can not always avoid. We may be too far out when the storm comes thru.

As many of us have pointed out, that sloped (wine glass) CD underbody finally comes into increasing the heeling stablity after a degree of heel is achieved in the flat or moderate sea conditions.

Hope I was able to get some of these thoughts and ideas across.

Dana



darenius@aol.com

[Steve Alarcon]

Brad,

Our CD30 performs best when healed no more than 20 degrees. 10-15 degrees makes it very comfortable, especially in a chop. We use the first reef point fairly often, mostly to reduce weather helm. I have the habit of sailing with all sails flying (we're cutter rigged) at up to about 20 kts, then reduce by dousing the Yankee. My friend with a CD33 seems to not be able to carry as much sail, probably because of his beam (that's just my opinion).

Steve Alarcon
CD30 Temerity
Seattle



alarcon@internetMCI.com

[Larry DeMers]

On our CD30, we hold all sail flying (140 genoa, staysail and full main) until 15-20 kts or 20 deg. heel. Then we reef the main one notch, gain about 5 deg. heeling ability, and **increase** speed by 1/4- 1/2 kt (less heeling, more sail area projected into the wind). As the wind increases into the 25-30 kt range, we trim the genoa from 140 back thru 100%, with a near-neutral helm as the sought for result. After 30 kts. we have the genoa furled, and have raised the spitfire on the *spinnaker* deck fitting/halyard/winch. This spitfire is a high clew, wire luff equipped and heavier constructed jib of about 90% J measurement, and it gives us good penetration into the waves which will be in the 5-8ft. category. This is effective up to perhaps 40 kts. At this point we take the spitfire down, dbl. reef the main and use a flat staysail. Pointing at this wind speed is not too great..and tacks are usually 120 deg. at best..frustrating.(Any ideas on how to get better pointing or penetration in these winds?). We have sailed in 50+kts, under staysail only and both dbl. reefed main and staysail, but it is not very rewarding..motoring with a very tight staysail will give better forward speed.

Hope this helps with where to change sails to limit your heeling.

Regards and good sailing,

Larry DeMers
s/v DeLaMer
Cape Dory 30 #283 ~~~~~~~Sailing Lake Superior~~~~~~~~



demers@cray.com