# Shoal Draft vs. Deep Keel



## labatt (Jul 31, 2006)

OK... still trying to make the decision regarding the purchase of a Hallberg-Rassy 53. MOST (read: not all) bluewater boats of this size all seem to be within a foot of the 7'6" draft of the HR53.

On the other hand, you can get a shoal draft version of many boats. IN GENERAL, are you sacrificing righting moment or other safety when you move to a shoal draft keel vs. a "standard" length? I know you are sacrificing several degrees of pointing ability, but safety? It's my understanding that the change in righting moment is negligible, but please correct me on this and other points!

We're trying to analyze the trade-offs between a shorter (safer?) passage with a deep draft vs. safe harbor flexibility and shorter dinghy rides from anchor with a shoal draft keel. We'll be at anchor much more than on passages, but with two kids on board that I'd sacrifice my life for, I don't want to sacrifice safety for convenience.

Thanks!


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## bonnelaine (Sep 18, 2007)

*lake champlain*

beautiful sail,the only shortcoming is you will run out of lake.
bonnelaine
lake ontario


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## labatt (Jul 31, 2006)

Bonnelaine - Right now we're on Champlain, but the HR53 (or other boat) would be used for a trip up the St. Lawrence, around Nova Scotia, down the east coast of the US and then somewhere, and then to Panama and beyond. Right now we're talking about 1.5-2 years, but the possibility for longer exists


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## GySgt (Jun 11, 2007)

My 2 cents: Depends on the boat and what type of sailing you do. You could argue that a shoal draft will have more inside ballast, but really in the conditions that your keel would come off, will normally cause you to turtle anyway. I think you could argue, and I am sure it has here, all day with tons of data and it still comes down to boat design and type of sailing and personal preference.

As far as safety, know your boat, know and define your and your crews abilities and always have a plan B.

P.S. I would take my family to sea in a seaworthy HR or Caliber anytime, but then again...I like HR and Caliber


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## bonnelaine (Sep 18, 2007)

god bless you and good luck .
if it was me i would look into min depths for the icw as it would be nice and good sense to have the option .good luck to you


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## JohnRPollard (Mar 26, 2007)

Labatt,

The shoal draft version normally should have the same righting moment -- usually achieved by adding additional ballast. So I would not worry about the question of righting moment vis a vis safety. And on all but the hard legs to windward, you probably would not even notice any performance difference between the standard (deep) and shoal draft variants in a boat of this size. You might even see an advantage in the shoal downwind (a friend with a shoal J42 claims his boat is faster off the wind than the standard draft versions). A lot of open ocean sailing is with the trades, so you could conceivably make faster passages with the shoal variant. But all-in-all, I'd call it a wash with perhaps a slight edge to the standard draft.

I agree, it is hard to find a boat in this size range that is REALLY shoal draft and still has good windward performance. The exception is those fitted with centerboards or full keels, which you seem to be steering clear of. So generally you are choosing between 6.5' and 7.5-8.5'. In your place, I would try to keep it under 7' if possible. But if you end up with a deeper draft boat, you'll just have to accept some modest limitations on where you can go -- there's plenty of deep water on this blue planet. Also consider re-sale -- you might want ot finish that trip on the US West coast where shallow draft is much less of an issue, or back in the Med/Scandinavia.


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## PBzeer (Nov 11, 2002)

Face it Chris, you're smitten. You want the HR, so just go ahead and get it, then get to the other side of the US as quick as you can


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## labatt (Jul 31, 2006)

John - It's killing me! I'm actually not completely smitten... a little bit of my logical side is peeking through, mostly when I'm talking to the loan broker.


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## RandyonR3 (Oct 2, 2005)

I own a FIRST 42 with a tall rig and a deep fin keel, (about 8 feet) and I find you really have to watch your water. At the present, we're up in the California Delta, about 60 miles from the pacific and we find we often have to detour a number of miles to sometimes get where we want to go.
As for the righting of the boat, I would'nt think there would be much difference as when the boat heels, the further over it goes, the more wind it takes to push it over due to the sails dumping the wind, so at 15 degrees of heel, it may take twice the wind to push it another 5 degrees. What you may find is the boat might be a little more tender in movement with a shoal keel.
What I've found, my boat becomes more stable as the boat speed increases.. This very well could be a result of the deep fin keel.


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## camaraderie (May 22, 2002)

I'll continue to be the contrarian here Chris...I agree with John that there is NO safety issue with a shoal draft. 
I would not buy a boat with a 7' draft for all the reasons discussed earlier + if you ever want to sell her...you will have a difficult time on the East coast. 
That said...if you do it...you will still have a wonderful time and it is a wonderful boat.


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## Rockter (Sep 11, 2006)

Well, when you do buy the ship, come to Loch Ness. 
We have 750 ft of water there, and plenty in the canal, so your deep fin (or shoal) will not run aground.
I'll charge my batteries so's I can run the fridge and give you a beer, or five.


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## nolatom (Jun 29, 2005)

camaraderie said:


> I'll continue to be the contrarian here Chris...I agree with John that there is NO safety issue with a shoal draft.
> I would not buy a boat with a 7' draft for all the reasons discussed earlier + if you ever want to sell her...you will have a difficult time on the East coast.
> That said...if you do it...you will still have a wonderful time and it is a wonderful boat.


Ditto for Gulf Coast.


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## Valiente (Jun 16, 2006)

You seem to understand the pluses and minuses already. I notice a large difference between sailing a 40-odd foot steel cutter and my 33 foot fin keeler that go beyond the fact that the boat that is one-third the displacement has about six inches more keel (grin). Working to windward is the prime difference...the cutter is more modest in this regard, and will make a bit more leeway. My helming has changed, as well, because I've got vastly more windage, but also a rudder the size of a dining room table.

The trade off is in "sea kindliness", something that can be mathematically determined, but really has to be experienced. The modified full keel is surprisingly tender when the boat is unballasted, but when properly on her lines, is very stable, even bashing into the wind. The "roll" is less snappy and the "rise" more gradual. I can tell, even in Lake Ontario, that it will be possible to sleep on passage. This would be very hard on the fast but "trembling" deep fin keel.

On the other hand, if I was doing coastal and didn't anticipate low water, the deeper, the better for performance.


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## labatt (Jul 31, 2006)

Kind of funny... the ballast on the Hallberg-Rassy 53 we're looking at is within a couple of thousand pounds of my entire Passport 40!


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## JohnRPollard (Mar 26, 2007)

Labatt,

It may sound preposterous, but it's not unheard of to swap keels. I don't know if it can be done on an HR53, but if this is your dream boat and you are struggling with the draft issue, it might be worth inquiring. Obviously there's expense, but you should be able to get a credit for the old keel (that's a heck of a chunk of lead). Also, I have heard of owners swapping keels. You might ask the factory if they know of a shoal boat that has asked about getting the standard keel....


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## labatt (Jul 31, 2006)

I believe the shoal is only 6" less, so it's kind of a moot point. I considered hiring a naval architect to design a new keel for her, but I'm concerned about damaging the resale value significantly.


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## Gramp34 (Oct 5, 2006)

I'd suggest contacting HR directly and asking for stability plots and polar plots for the regular- and shallow-draft versions. 

They provide the polar plot for the regular draft version on their website. The stability calculations are necessary for their CE approval, so they know these numbers.

Which ever version you pick, this data will also help answer questions when it comes time to sell the boat.

Cheers,

Tim


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## kennya (Jul 10, 2006)

*To get a warm fuzzy*

To get a warm fuzzy on the boats you are looking at try using the "Angle of vanishing Stability Calculator In the US sailing Keelboat course http://www.sailingusa.info/cal__avs.htm


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## TSOJOURNER (Dec 16, 1999)

> I believe the shoal is only 6" less, so it's kind of a moot point. I considered hiring a naval architect to design a new keel for her, but I'm concerned about damaging the resale value significantly.


Might affect resale, but then agaion it might make it easier to resell. The market for large boats is not the same as for the smaller ones. There aren't a lot of 50 footers out doing the PHRF one Tuesday nights. Buyers tend to evaluate each boat on its own merits.

If you decide to explore the Keel-swapping thing, there is a company called Mars http://www.marsmetal.com/newpages/keelhome17.html that has a lot of experience in this area. They can probably provide you with some good input.


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## Valiente (Jun 16, 2006)

Mars are great. They make all sorts of international keels, and cast the keel for _The Spirit of Canada_, the Open 60 that's just left for trials in Brazil to qualify for the 2008 Vendee Globe. I've met the skipper several times now...he is a _very _focused individual.


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## tommyt (Sep 21, 2002)

OK, I am certainly not a naval architect, but I don't get it.

You are thinking of buying a new, or almost new, HR53, most likely closing in on a million dollars. And now, because you think you may want a shoal keel, but are not sure, people are suggesting that you switch out the keel???????
Come on guys, HR is one of the most respected BW boats made, their shoal keel, according to Labatt, is about 6" less than the deep draft. Are we all nuts, or what?

First, the cost of replacing the keel on this puppy will probably be somewhere between $50K and $100K MINIMUM. When you get done, you will have a one of a kind. In this case that is NOT a good thing. How many buyers do you think you will find down the road for this one off? HR builds it one way and because you are not sure you switch to your own design and a future buyer just decides you were right and not HR? A buyer in your price bracket does not come along every day. A buyer of an HR, that is no longer an HR, at that price range is a one in a million. I almost said a one in a million idiot, but I know this is tearing you up and you have not made the decision yet.....so forgive me. So, you invest $100K plus in the keel change out, and then the boat is worth what, $300-400K less than it should be because of the change?

Labatt, you are a lucky man. Probably worked your ass off for that luck, but you have a chance to live your dream. Decide WHERE you want to go and buy a boat to go THERE. Or, buy the BOAT you want and go where you 
CAN and be happy with the boat. You will be making a compromise whatever.

In this size range and quality of boat, you should not worry if it is shoal or deep unless you are racing and worrying about that extra couple of degrees of pointing ability. However, I think that cruising is your dream and going to weather a few extra degrees is probably not an issue.

NOW, if you buy new, and HR says sure we can design this with a shorter shoal draft that will be just fine, then you have your boat, HR designed it that way, and you get what you want.

Now, if you really think about replacing a keel on one of these beauties, call a friend to hit you up side the head!


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## CBinRI (May 17, 2004)

camaraderie said:


> I'll continue to be the contrarian here Chris...I agree with John that there is NO safety issue with a shoal draft.
> I would not buy a boat with a 7' draft for all the reasons discussed earlier + if you ever want to sell her...you will have a difficult time on the East coast.
> That said...if you do it...you will still have a wonderful time and it is a wonderful boat.


"East Coast" may be overstating it. I'm in the Newport area. It is virtually all deep around here and many people are much more concerned with performance than they are with gunkholing or shallow water cruising options.


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## camaraderie (May 22, 2002)

CB...you're right of course about the NE coast. But if you want to cruise the East Coast as Labatt does...then you need to be concerned about the whole coast...as does anyone who would buy the boat in the future. Not too many people buy 50'+ boats to stay put in their home cruising grounds unless it is a racing boat.


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## chucklesR (Sep 17, 2007)

Shoal draft is usually refered to as 4 to 4.5 feet, calling 6.5 feet shoal draft is silly as hell.
I draw all of 20 inches board up and motor down, and I've run around or popped rudders twice this season - imagine what you are going to have to do with 6.5 feet of keel dragging around down the ICW?

Go catamaran and get over it


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## TSOJOURNER (Dec 16, 1999)

Buy it and move the West Coast around Seattle; cheaper than swapping out the keel, and much better sailing area. For free, I'll throw in the BC coast and Alaska coastal areas.


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## SVAuspicious (Oct 31, 2006)

My "shoal" draft HR40 draws 11" less than the standard keel. I'd be surprised if the shoal draft HR53 doesn't provide a similar reduction.

Talk to HR -- if you really feel strongly about reducing draft, perhaps you can get a factory shoal keel and replace the one on the boat you are considering. Note that if the tank arrangement is anything like mine, you'll have to pull two or three tanks to reach the keel bolts. Readily done, but potentially messy.

I don't think I'd do it. If you like the boat then buy her. Put some of the modification money into a good set of davits and fast comfortable dink. You'll do fine in most of the cruising locations of the U.S. East Coast. The ICW is more limited by your mast height than draft. The difference between 7.5' and 6.5' in the Bahamas probably isn't significant -- you would still have to be very careful. Solution? Head down island sooner.

I don't think you'll regret owning an HR.

By the way, there is a very nice 48 for sale in Annapolis. I've sailed her, and sailed alongside her. She's great.

The biggest difference between deep and shoal drafts is how close to shore you are when you run aground. <grin>


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## TSOJOURNER (Dec 16, 1999)

There are plenty of boats with 5 foot drafts. I have gunk-holded in the calif delta with no problems. Get a full keel and your worries about sailing any points will disappear.


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## TSOJOURNER (Dec 16, 1999)

*Deep Keel vs. Shallow Draft*

You are looking at a great boat. I sail the great lakes and have been to New York and the East Coast in my Catalina 36 and I bought the boat to do the intracoastal, Keys, and great lakes. No question I needed the shoal draft. I see no difference in sailing which detracts from the pleasure. Look to where you wish to go. If staying east coast, Bahamas, and keys, consider the shoal draft. You will not be able to do the intracoastal but you have a bluewater craft so that is where you take her. Otherwise fair winds and great adventures


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## JohnRPollard (Mar 26, 2007)

Good advice all around. 

The OP (Labatt) has indicated in other threads that he has put a contract in on the standard draft HR53. So I think he got what he needed from this thread. We are all waiting to hear whether the deal goes through, especially those of us in the Annapolis area who all want a ride on it.


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## TSOJOURNER (Dec 16, 1999)

*7 + Ft Draft will deter some fun*

Greetings from Miami

Reading this thread I am reminded of a friend who purchased a deep draft vessel against all advice and found himself in trouble with his wife and kids - mostly because they had to anchor far from shore, bypassed the Bahamas and Florida Keys, and beacme obsesive with "good anchoring grounds" - he sold the boat, put his money back into the bank and got himself (against my advice) a Morgan 51 that needed some TLC - this is an ugly boat but fit his needs and the space and confort his wife wanted - I guess is good for the caribbean but I will never dream it for a round the world passage

Although passage making has a thrilling alure for many captains - the reality is that the crew rather spend their time island hop - and there is where a deep draft rob you from flexibility.

Most live aboards get their feet wet traveling down the east coast and later jumping to the bahamas and caribbean - rough weather can be avoided at any time by accessing the ICW - but draft and mast height can complicate things. I believe if you are set in purchasing a monohull, you should consider your options at full keel vessels (they track better) and keep the draft under 6ft if possible. Iwill argue that a ketch has more flexibility for all around weather and sail plan.

With the kind of money you are expected to lay - I would thing a Cabo Rico as an option - or refit any of the many ketches out there in the Caribbean for sale - Trinidad has very good yards and you can start your cruise with the good weather and beautiful island to get your crew used to their sea legs - see this Nautical 56 ketch for sale in St Marteen - draft 5 ft to 9 ft with the centerboard down. you can google at yatchworld.com under 56' NAUTICAL CENTREBOARD KETCH

With the kind of money you will be spending I would get a catamaran - better resale value in the event you grow tired of cruising


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## karnak (Jul 25, 2000)

*Shoal vs deep*

It sounds like you are more worried about stability and safety than running close hauled to weather. Since you are not racing, but looking to do some shallow water cruising, I would recommend something like a 48' Island Packet 485. New, it will run $700K plus another $75-100K to outfit as you want, and then you basically have a custom blue water boat. 
LOA is 52', LWL is 43' draft is 5'3" AND the displacement is 44,150 #'s with 16,000 in the keel. This boat will go anywhere, quite roomy and almost bulletproof. You also have the self-tacking staysail for when the bad weather hits and you need a good heavy weather headsail. It may be a full keel, but picking up lobster pots in the N.E is less of a headache with the attached rudder.
Besides, you are saving @$200k for the kitty  What's not to like?


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## TSOJOURNER (Dec 16, 1999)

*Deep is safer*

All things being equal, ballast that is located deeper will produce a greater righting moment. To compensate for that, many designers increase the ballast weight (and therefore total displacement) of their shoal draft versions. However, I believe the ballast moment computation still favors the deep version in most cases. No less of an authority then Olin Stephens, who has designed many successful shoal draft boats (Carlton Mitchell's Finisterre comes immediately to mind), has stated that, unless the sailor's predominate cruising grounds dictated shoal draft, he would much prefer deep draft when heading offshore. fficeffice" /><O></O>
<O></O>
"Vanishing Angle of Stability" (AVS) is a useful comparator. A tool for that computation is found on the US Sailing website: sailingusa. 
An angle of 120 Degrees is considered a minimum for offshore work. Back in the CCA rule era, AVS numbers in the 140-170 degree range were the norm. After the Fastnet race disaster of 1979, tank testing showed that boats of "classic" proportions (narrow beam, high AVS) were very hard to capsize and would always self-right very quickly. AVS will decrease as weight is added to the rig (roller furling), so if 120 degrees is the starting point for a production boat, you may end up with an unsafe number once fully equipped for cruising. <O></O>
<O></O>
Given the time and money you are planning to expend, I think it might be a wise investment to pay a Naval Architect to comment on the boats you are considering. Also, get a copy of Heavy Weather Sailing - 13th Anniversary Edition, and read the first four chapters. Among other things, you'll find that stability increases with size. So the 53-boat boat you are considering, with shoal draft, may have more ultimate stability than a 40-foot boat with a deep keel.<O></O>
<O></O>
In the end, you'll be stuck with the same trade off many of us have struggled with: Safer offshore (deep keel) or more access to thin water areas (shoal draft).<O></O>
<O></O>
Though rather wide, I have always admired HR boats and think you will likely end up confirming your original preference.<O></O>
<O></O>
Dave Hanson<O></O>


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## TSOJOURNER (Dec 16, 1999)

*Go Shoal*

Hi. I've owned a 30' with a wing keel and have spent weeks at a time on a 35' C&C with a deep keel. My wing keel was great for pulling up to sandy beaches and that's important with kids (they like to get places not just travel). But, first: make sure the shoal keel drops below the rudder! If not, your rudder is at risk. The pro's of a wing/shoal keel: great down wind performance; you can go just about anywhere; and tides, tides, tides. The con's: I'm certain that there is more motion when at anchor (it puts me to sleep), you lose some upwind comfort when underway because there isn't as much "drag". I've thought this one up and down, and I wouldn't buy a boat with a deep water keel.


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## labatt (Jul 31, 2006)

We talked to a friend of ours who has been a charter captain (on his own boat) for 10+ years. He summers in New England and winters between the Bahamas and the VI's. His boat has a 7' draft. We talked with him at length about the limitations of a deep draft boat, and we're comfortable in what they are. What's the phrase? "Eyes wide open". 

This thread was about the inherent differences in safety and performance between a deep draft and a shoal draft boat. When you take a boat that has a deep fin (or other) keel, chop it off and change how low the ballast goes - what effect does that have? Is the boat less safe? Does the performance have a noticeable difference? It seems like there should be SOME difference... 

I have a couple of other threads around here debating whether deep draft boats should be selected as cruising boats. The information on this thread and others has been invaluable.

Ultimately, I've put an offer on the HR53 (and would be happy to host a Sailnet party on it if we get it!). I will be happy if we get it, I won't be terribly unhappy if we don't.


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## TSOJOURNER (Dec 16, 1999)

This one is so easy. If you are planning the Bahamas, shoal draft will make it a much less tense experience. Same with many points beyond.


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## tommyt (Sep 21, 2002)

Labatt,

Good decision, because it is your decision! Hope the deal works out to your and your families best interest. Good Luck with a great boat.


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## sailingdog (Mar 19, 2006)

Congrats Labatt...  Good luck with the survey and sea trial.


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## TSOJOURNER (Dec 16, 1999)

1st Good Luck Labatt! Bigger balls than me - I wouldn't plan 1-2 years at sea with my family.

2nd - Deep keels, Righting moment and pointing capabilities.

I'm an "ultralight sailor" I have a 12M 3500 lb sailboat (a Screamer) and there were two keel options, and I have a third, custom designed keel.

As I blast past full keeled and deep keeled boats I always think about how paradigms cause design, but ultimately everything is a series of compromises. My boat has about 24" of freeboard, no "down below" and thats how it saved weight. 

Now of cruising boats and keels and pointing - as a guy who's raced A LOT one thing I notice when I get on an average cruising boat is that forestay tension is not what it should be, the streamstay/rollerfurler track tends to curve off dramatically to leward when sailing close hauled.

This causes several problems:
the boat won't point as well
the boat won't sail a straight course (tends to crab-off to leward more)
its DAMN SLOW

Now couple that with the fact that most people believe that more jib is better (which isn't true upwind) and you get poor upwind performance compared to "optimal" i.e. these points were addressed.

What am I saying? before you worry how 12" of keel will help you perform up wind, explore the variables that you can more easily control, jib size, forestay tension (if you can, if you can't you should make it so you can!) and see how that works - you're gonna surprise yourself 

PS - I run a full main and self tacking 85% Blade in 12 knots apparent and see 10 knots (planing) COG on a close reach (50 degrees apparent wind angle) - yes I need apparent due to speed vs wind speed ratios


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## Jeff_H (Feb 26, 2000)

One minor point on headstay sag, most cruising boats operate at far less headstay tension than high performance boats. Sailmakers seem to understand that and cut the leading edges of cruising jibs for that headstay sag. The result is a sail that actually points well despite the sag in the headstay.

The reality is that the windward ability of most cruising boats is limited by their underwater configuration such that no matter what you do with new sails and tuning, the ultimate VMG is limited by the drag of the hull and the inefficiencies of a shoal draft keel. 

Which is not to say that cruising boat performance can't be improved by having well cut sails set properly, a clean bottom, and proper rig tuning. Its just that the impact is far less than might be experienced on something like a Screamer or other higher performance boat.

Jeff


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## captmikem (Feb 28, 2004)

*Keels.*

It really depends on what you honestly want to do.
I had an HR42 on Lake Champlain, I sailed it down the east coast and the <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-comffice:smarttags" /><st1lace w:st="on">Caribbean</st1lace>. The only real problem I had was on the lake a few times, and on <st1lace w:st="on">Chesapeake Bay</st1lace>. That said, I also sailed around the on a custom boat drawing 11 feet. I never regretted having that much keel under me, (other than one time trying to get into <st1:City w:st="on"><st1lace w:st="on">Brisbane</st1lace></st1:City>).
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o> </o>
My suggestion is that if you are going to coastal cruise, like the <st1:country-region w:st="on">Bahamas</st1:country-region>, and <st1lace w:st="on">Caribbean</st1lace>, then go with the shoal draft. Your mast height on the 52 will probably keep you off the intracoastal anyway.

So be really honest with yourself and what you want to do. Then decide.


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## Diva27 (Nov 2, 2007)

*stability myths*

There's a lot of fuzzy thinking about sailboat stability out there. As coauthor of Yacht Design Explained (shameless plug: buy it, read it, memorize it), I'll touch on the basics. 
Keel draft matters with respect to how it affects how deep the boat's centre of gravity is located. It's important because as a boat heels, its stability depends on the horizontal separation between the centre of buoyancy and the centre of gravity. That separation is the lever arm that describes the righting moment. Generally speaking, the deeper a keel is, the lower the boat's centre of gravity becomes, and you can achieve the same righting moment in the same hull with a shallower but heavier keel. Keel draft is critical to windward performance. Deep and narrow is more efficient than short and long. So with a shoal draft, you're generally accepting reduced windward performance in pointing ability, as well as an overall heavier (and slower) boat. But draft is critical to determining where you can anchor, of course. I have a vintage C&C 27 that draws 4 feet 3 inches, and I'm glad, given water levels on Georgian Bay in recent years.
Bottom line is that a shoal draft design can be as stable as a deeper draft design, provided the designer has done his/her homework. Where it's a matter of putting a different keel on the same hull, the shallow draft keel is going to need enough volume to hold more ballast, or else the additional ballast has to be placed in a much less efficient location, up in the bilge. Shortening the rig also helps in this case, as this lowers the centre of sail force. The distance between the centre of sail force and centre of keel lift, measured down through the mast and keel, determines the heeling arm. The longer the heeling arm is, the greater the potential heeling moment (force times distance), and that requires a larger righting moment to oppose. I've been grossly simple here, but maybe you get the idea of what's involved.


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## Tartan34C (Nov 21, 2006)

Diva27 said:


> I've been grossly simple here, but maybe you get the idea of what's involved.


Nice short and concise description. But because the distance term in the polar moment of inertia is squared and the distance term in righting moment is liner the amount of energy to flip a shoal draft boat that has the same righting moment as a deep draft boat is less. Also as the draft increases the horizontal separation between the center of buoyancy and gravity increases more rapidly at a greater draft for a given heel ((depth of CG )X(sign of heel)) so you really need a higher righting moment on the shoal draft boat to get a similar feel as the deep draft boat. Look at an ice skater in a spin to see the effect of changing the polar moment of inertia. Bringing in the arms increases the speed of rotation. Everything is a tradeoff and nothing is straight forward.
All the best,
Robert Gainer


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## JohnRPollard (Mar 26, 2007)

This has been a good thread. I hope no one will object, but I took the liberty of beginning a "Part II" over in the "Sailboat Design and Construction" forum:

http://www.sailnet.com/forums/showthread.php?t=38171


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## camaraderie (May 22, 2002)

If you guys would like this entire thread moved to "design and construction" drop me a PM
*EDIT:* OOPS...never mind...John moved the relevant posts already. 
. Welcome aboard Diva. good start!!


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## JohnRPollard (Mar 26, 2007)

Thanks Camaraderie.

To clarify a bit further, if you would like to discuss the pros and cons of shoal draft vis a vis getting through the Intracoastal Waterway, or cruising the Bahamas, or visiting certain Pacific atolls with your family and the implications thereof, etc, continue to post to this thread.

If you would like to discuss in a more technical respect the effects of shoal draft on boat performance and other characteristics, head over to the Part II thread.


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## Diva27 (Nov 2, 2007)

I'm a civilian, not a designer. My coauthor on Yacht Design Explained, Steve Killing, is the one with the certified brains. He's done 4 America's Cup campaigns, worked at C&C for 7 years, and just won the C-class worlds (multi-element wing foiled cats) on his first try. He usually makes me sit down before I hurt myself when discussing this stuff. We're working on a new book on the physics of sailing, called The Science of Sailing, which will be out next year with Int'l Marine. 
My longwinded point here is that what useful knowledge I've absorbed from being in close proximity to Steve reminds me that stability in a sailboat, especially dynamic stability (how it changes as the boat changes attitude) is fiendishly complicated. The centre of buoyancy moves fore and aft as well as outboard, and true stability can only be determined by knowing what the entire hull volume is doing. Also, the point of rotation is this slightly mystical thing called the metacentre, which is always directly above the centre of buoyancy and is always changing. Steve has told me time and again that most designers don't really understand the metacenter, and he's generally reluctant to even bring it up when discussing stability.
Again, I'll keep things grossly simple. On p103 of Yacht Design Explained, we compared two different draft configurations on the same 39-foot hull at 20 degrees of heel. The deep draft version with a bulb was 8.6 ft deep. The shoal draft was 5 ft. Deep draft disp is 9600 lbs, ballast 3800 lbs. Shoal draft disp is 11,400 lbs, ballast 5,600 lbs. Their righting moment at 20 degrees is the same: 14,020 ft-lbs, and the deep draft version overall is 1,800 lbs lighter. We used this discussion in part to show why throwing around ballast-disp ratio numbers in comparing boats is pretty useless when it comes to stability, unless you know the keel configuration as well as the hull form (which affects the movement of centre of buoyancy as the boat heels).
All for now. Nice chatting.


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## Tartan34C (Nov 21, 2006)

It’s nice of you to join us Diva27 and I think you will enjoy some of the conversations here. They range from somewhat technical to just plain fun. I am also looking forward to the publication of you and your friends work, The Science of Sailing. It’s a subject that I enjoy reading about. 

As you said the dynamic stability is, to use your words, fiendishly complicated. But you may have mistyped when you described the metacenter as the rotation point of the underwater volume of a vessel. The metacenter is a point on the heeled center line which is directly above the center of heeled buoyancy and it is labeled M in naval architecture. The vessel rotates about a moving point which is the center of buoyancy (B). As the boat heels the center of buoyancy moves outboard, more or less depending on the shape of the hull so the hull is always rotating around a point that is itself moving. The all important GZ is the horizontal distance between the center of gravity (G) and the center of buoyancy at the level of G and is measured on the construction line from B to M and that measurement point is called Z. This value (GZ) is popularly called the righting arm. The metacentric height is the distance between G and M and it is called GM and is important because the righting force is proportional to the metacentric height (GM) times the sine of the angle of heel. GM also has a direct relationship to a boat's rolling period in seconds.

As you said most people misunderstand how to use the ballast displacement ratio. It is best used to compare similar boats so that the ratio has some meaning. Different hull shapes do better with different ballast displacement ratios so making a comparison between different types or shapes of boats is misleading. If you just use it to compare similar hull types you can make some statement about the relative stability of two boats.
All the best,
Robert Gainer


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## Diva27 (Nov 2, 2007)

*metameta-ing*

You see, this is why Steve never lets me talk about the metacenter. I'm sitting down now.


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## Tartan34C (Nov 21, 2006)

camaraderie said:


> If you guys would like this entire thread moved to "design and construction" drop me a PM
> *EDIT:* OOPS...never mind...John moved the relevant posts already.
> . Welcome aboard Diva. good start!!


Cam,
This thread seems to be going in two places at the same time? Can you merge the two and place the result in the design forum?
Thanks and all the best,
Robert Gainer


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## camaraderie (May 22, 2002)

*ALL ...this thread is for GENERAL discussion and questions about shoal draft vs. keel including questions like...I'm thinking about this centerboard boat...what do you guys think of it?

Technical discussions about DESIGN of shoal draft and keel boats are over on the design subforum on this thread:
http://www.sailnet.com/forums/showthread.php?t=38171

Please try to make your comments/questions in the apropriate thread. *


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## Trekka (Jul 16, 2006)

Artwerke said:


> All I know is shoal draft= sailing in the bay, while deep keel means motoring 2-3 hours, out the channel past the jetty. 38' Irwin 3' keel with 6'CB.Art.


I'm with you on this. I would just modify it to say _"shoal draft= sailing in the bay, and up many more tributaries, while never worring about shoaling at various 'narrows', nor finding the skinny channel into _[xxx_] port that is best run at high tides..." _& etc.

All this discussion seems detached from the real world. The issue is not whether a deep draft boat is more resistant to capsize, it is _"how much is needed"_?

I sailed the Chesapeake for almost 25 years with a shoal draft (3ft) twin keeled boat and never, ever, feared capsizing. In fact my boat was very much more stiff compared to most similar sized single keel deeper draft boats.

If you are in a survival storm your concerns are greater in many other areas than draft.


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## Tartan34C (Nov 21, 2006)

Trekka said:


> All this discussion seems detached from the real world. The issue is not whether a deep draft boat is more resistant to capsize, it is _"how much is needed"_?
> 
> snip
> 
> If you are in a survival storm your concerns are greater in many other areas than draft.


Its not that the current discussion doesn't relate to the real world but instead it's drifting into a more technical discussion about the how and why of stability at the design level instead of a discussion from the end users point of view. But I do assure you that stability does exist in the real world and understanding how it works is worthwhile for both the sailor and designer. This thread has also been split and the technical discussion is intended to be done in the copy in the design and construction section.

The amount of stability you need is more related to the boats use and operating area and not if she is a centerboard boat or a keel boat or even a multi-hull. It also matters very much how much stability you need to feel comfortable while sailing. How you define or describe the amount of stability you have is necessarily a technical issue unless you want to define it as either enough or not enough and leave it at that.

The amount of draft you have is important but it is one and only one of the factors you take into account while forming you storm plan. You don't sail in storm conditions all the time so you may be able to justify a draft that even you would say is not ideal but is survivable in the worst weather you could reasonably expect on your route. Again, how to define and describe all of this is difficult without some standard or measurement system as a gauge.

I sail a centerboard boat right now and don't think I am at too much of a disadvantage compared to a deep draft boat in survival conditions. But my storm tactics and plan book are very different for my Tartan 34C then for some other deep draft boats that I have sailed offshore in the past. Shoal draft by itself doesn't disqualify a boat for storm conditions.
All the best,
Robert Gainer.


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## bestfriend (Sep 26, 2006)

Labatts original posts touches on both areas, no?


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## kengoodings (May 23, 2003)

Deep keel + great pointing ability but you'll greatly reduce your sailing grounds. The Great Lakes are very low these daze and the Bahamas are shallow too. If travelling abroad you'll have to anchor WAY OUT in less protected waters. You can't do the european canals either.
Out Niagara 35 draught is 5'4" but the Ontario 32 can get into more places with only 4'10" of keel


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## labatt (Jul 31, 2006)

It's kind of funny... as the original poster, I actually originally had two different posts. The first post was - what will my limitations be if I buy a deep draft boat like a Hallberg-Rassy 53 (7.5ft draft) if I'm looking to cruise along the east coast of the US, the Bahamas, then south to the VI's, Panama and beyond. This was the second post - what differences (performance and safety) can I expect for the same boat - one with a deep draft and one with a shoal keel. If people want my permission, take this thread in either direction!


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## saltybob2 (Mar 27, 2001)

Ok. I'm confused with your intentions. My wife and I lust after any Passport 40 we see. How is yours not asdequate for your intended voyage?


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## labatt (Jul 31, 2006)

Saltybob - be more than happy to sell you mine! She's actually an incredible boat and we'll be sorry to see her go. We've had her for less than a year but we've grown quite attached. Read this link for more info on the why... http://www.sailnet.com/forums/showpost.php?p=204240&postcount=29


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## sailor37 (Nov 2, 2001)

A friend of mine is currently removing his 8' draft keel and having a new keel cast which will give him 6' draft. This at considerable expense. I vote for shoal draft with centerboard.


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## SkipperSteve (Nov 23, 2007)

Not popular in the USA but invaluable in European waters is the Bilge [Twin] keel probably not an option with HR but never the less terrific alternative. you do lose a little when pointing. but when healed over the windward keel gives righting moment where the leward keel is now vertical below the boat compensating for windage. 
If your looking for advice : Buy the boat because you like it


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## sailingdog (Mar 19, 2006)

Steve-

IIRC, the problem with the twin keels is they present additional wetted surface...so are a bit slower than a boat with a fin keel of the same righting moment. However, they are very valuable in areas where the moorings dry out at low tide, as is common in England from what I understand.


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## Giulietta (Nov 14, 2006)

They sail like S**T....

But in some areas is the only way to be able to sail...an I rathe be sailing in s**t than no sail att all...

This thread boils down to the fact that if Labatt does not know the answer to his question by now.....


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## mtboat (Oct 14, 2007)

This thread has caught me. I'm buying and refitting the interior of a 1974', 24ft Buccaneer. I allready know they don't sail upwind well. I'm intrested in the matter of keels. All my previous experience is on small cats, this will be my first boat. I am a member of a couple of Buccaneer chats,and looking for other boaters opinion. This boat has a draft of 30 inches. I've read some posts that say they couldn't tip it over, because it turns into the wind. Can any body give me the simple version,why? Also I've read posts of these boats sailing 75 miles off Florida, as well as a post stating 50kt and 7 ft waves. Given all that, I would appreciate any comments on cruising the Carribean or Gulf with this boat.


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## Tartan34C (Nov 21, 2006)

They round up because the rudder isn’t very deep and when they heel the rudder comes up and almost out of the water and looses its grip on the water. Not a sign of good design but not fatal unless you are in rough conditions and don’t want to lose control of the boat.

As far as being suitable for being 50 miles offshore in 50 knots of wind, well it wouldn’t be me out there but its your neck not mine.
All the best,
Robert Gainer


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## camaraderie (May 22, 2002)

The Buc24 is a very lightly built 24 footer that has no business offshore in heavy weather and I sure wouldn't attempt to get to the Caribe on one. BUT...in fair, calm weather you CAN get to the bahamas and quite happily cruise around there in safety for months.


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## mtboat (Oct 14, 2007)

Thanks, I'm not the guy to sail like that But one guy said he encountered those conditions. My experience is so small, I'll be happy on Flathead Lake. I do however dream of warm places with warm water.


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## saltydog75 (Nov 22, 2007)

When on the Pacific coast I thought anything less than 30 ft. was shallow! Now on the Atlantic side I know different! When cruising full-time, Oui Si's draft was 6 ft. I now covet a catamaran with 1.5-3 ft. draft.


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## speciald (Mar 27, 2007)

With the 53 you won't be the intercostal anyway - the mast is too high.


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## sailingdog (Mar 19, 2006)

Umm.. 7' waves seem awfully small for 50 knot winds last I checked. I've been out in 7' waves with only 25 knots blowing, and 9-10' waves with 35 knots blowing...but I think the waves would be a wee bit higher than 7' if the 50 knots were blowing for any period of time....and a Bucc 24' is not a boat I'd be out there in...


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## JohnRPollard (Mar 26, 2007)

sailingdog said:


> Umm.. 7' waves seem awfully small for 50 knot winds last I checked. I've been out in 7' waves with only 25 knots blowing, and 9-10' waves with 35 knots blowing...but I think the waves would be a wee bit higher than 7' if the 50 knots were blowing for any period of time....and a Bucc 24' is not a boat I'd be out there in...


MTBoat said "I've read posts of these boats sailing 75 miles off Florida, as well as a post stating 50kt and 7 ft waves." I took from that that he was describing two different scenarios, not 7' seas in 50 knots of wind 75 miles off the coast of Florida.

The height of the waves depends as much on length of fetch as it does on windspeed. You could easily experience only 7' waves with 50 knots of wind if there was not much fetch (e.g., in near coastal sailing where the wind is blowing off the land), as was likely the case in the latter scenario.


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## hellosailor (Apr 11, 2006)

Labatt-
At this late point...May I suggest contacing MARS METALS? 
4130 Morris Drive
Burlington, Ontario, Canada L7L 5L6
905-637-3862; 1-800-381-KEEL
fax 905-637-8841
[email protected]

Probably the largest actual source of keels in North America, experienced in modifications, shoes, torpedos, bulbs, etc. as well. I've often wondered about the practical side of removing several "cores" from a lead keel and slipping in replacements poured from tungsten--which is twice as dense and rather more expensive.

But at a certain point I would think it becomes eminently practical to slice a foot off a deep keel, add the tungsten sabots into it, and "voila!" restore all the benefits of high mass low down, without the original keel depth.


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## sailingdog (Mar 19, 2006)

Hellosailor-

Again... Tungsten is not twice as dense as lead... 

Lead has a density of 11.34 g/cc
Tungsten has a density of 19.25 g/cc
Osmium has a density of 22.61 g/cc.

While tungsten is significantly denser than lead... it is not twice as dense. Osmium, is very close to twice as dense, but significantly more difficult to get. However, osmium is probably significantly more expensive than tungsten, and generally only used in alloyed forms, which are far less dense than the pure metal.


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## mtboat (Oct 14, 2007)

The reference I quoted is from a site called 48 degrees north, in an article titled Beleagured Bayliners. by Jeff Stewart Spokan Wash. Did I misread? The reference to 75 miles off the Florida Panhandle was in another blog called "more input" at [email protected] http://www.48north.com/mar2001/letters.htm


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## hellosailor (Apr 11, 2006)

Thanks, SD, I appear to have been mislead. Still, tungsten should make a good cost-effective alternative for shifting mass. Civilian market, readily available, less toxic than spent uranium.

And for all those years, we could have been saving up light bulb filaments but no, we just threw them away as trash.<G>


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## sailingdog (Mar 19, 2006)

Osmium isn't spent uranium... it's in the same family as platinum IIRC... and probably just as pricey.


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## Donque5 (Oct 20, 2007)

John,
Global warming will improve the deep draft, somewhat but, shoal draft considerably.....


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