How much does a Shoal Draft Keel affect Blue water sailing?

[WingRyder]

Originally Posted by MartinR

Stable, but not very stable. In a real situation, with heavy seas, she would right herself in a relatively short time.

All of these figures are calculated, nobody tests the boat to upside down condition. Often this is verified by a heeling test to some reasonable heel. I am not sure if anybody knows how mast and rigg affect this while they are underwater. I would normally expect to loose the rigging when being rolled.
So, I always try to stay upright

Todays boats are beamy, because it gives the biggest interior room for the bucks, not the most seaworthy boat. All boats are compromises, but personally I would go for a few feet longer and moderate beam. Gives the same interior space, but a much better motion comfort factor.

I figured as much. They DO crash test cars, but boats models aren't typically built in the same quantities as cars, so such a test would be a heavy financial burden to the manufacturer. I assumed that perhaps they ran scale models in a tank or something, but it sounds like the only REAL data is limited to computer modeling... and even then, are all boats modeled equally? But often data like this doesn't scale up, so that would probably be useless. There are so many variables in a real world condition, capsizing, I wonder if the AVS data has much practical value at all.

Staying upright! That seems like the way to go!

Since I plan to sail (mostly) solo, I would like a boat that is a manageable size, so that is consideration #1 ... a boat of a size and layout that can be sailed and docked solo.

[Seabeau]

Originally Posted by boatman61

Which brings us to the Smaller is Safer arguement..
But then theres members who think a crossing to the Bahamas is ocean sailing.

Has little to do with the size of the vessel, it has to do with its draft. A shallow drafted boat, ie a pure centerboarder or lifting keel equipped boat with their appendages retracted, can move with the breaking wave rather than be struck by the wave.

[MartinR]

Originally Posted by Seabeau

Has little to do with the size of the vessel, it has to do with its draft. A shallow drafted boat, ie a pure centerboarder or lifting keel equipped boat with their appendages retracted, can move with the breaking wave rather than be struck by the wave.

Nice idea, but there is no empirical evidence for that. In this case long-keeled yachts should be more prone to knock-downs. They are not. Probably this is due to the fact that the keel also provides a lot of roll inertia.

[MartinR]

Originally Posted by WingRyder

Since I plan to sail (mostly) solo, I would like a boat that is a manageable size, so that is consideration #1 ... a boat of a size and layout that can be sailed and docked solo.

That is very much depending on personal abilities. And I can let you in on a well-kept secret. Bigger boats are easier to dock than smaller ones. Everything happens much slower Of course, the consequences of a mistake are more expensive

Actually, the sail area is a much more important factor than boat size for manageability. Big sails are heavy to handle.

[Seabeau]

Originally Posted by MartinR

Nice idea, but there is no empirical evidence for that. In this case long-keeled yachts should be more prone to knock-downs. They are not. Probably this is due to the fact that the keel also provides a lot of roll inertia.

Yes these is evidence. My internally ballasted, 18,000 lb. true centerboarder(with no keel), with the centerboard retracted has been carried by breaking waves 30 to 50ft sideways more times than I can count, with no ill effects. A deep keeled yacht, whether fin or full in breaking waves will "trip" over its own keel. My boat was designed in 1884 by Ralph Middleton Munroe of Coral Gables Florida.

[MartinR]

Originally Posted by Seabeau

Yes these is evidence. My internally ballasted, 18,000 lb. true centerboarder(with no keel), with the centerboard retracted has been carried by breaking waves 30 to 50ft sideways more times than I can count, with no ill effects. A deep keeled yacht, whether fin or full in breaking waves will "trip" over its own keel. My boat was designed in 1884 by Ralph Middleton Munroe of Coral Gables Florida.

That is evidence that you have a seaworthy boat, but not that this is superior to keel boats or that a shallow draft is safer than a deep. If you look at full keel boats from the same time, they can easily lie ahull or heave too under very bad conditions without being rolled. I have had both a Colin Archer (external ballast) and a Bristol Channel Pilot Cutter (internal ballast). I have been out in very bad weather and never experienced even close to a knock-down. There is normally no need to sail these boats actively in storm conditions as it is with modern boats. They drift sideways, create turbulence and induce the waves to break a little bit away from them. But they do not stumble over their keels. Never heard of a knockdown for any of these boats.

Modern type sailboats might do this, but there are other factors in play. With a modern boat you can go two ways, beat up under very much reduced sails, which is safe but very uncomfortable or run at the correct speed, keeping the boat stern on to the waves. Side to most modern boats are inherently unstable. Sooner or later, they will end up with their quarter to the waves, pick up speed and then the broad stern with excess buoyancy is caught by the wave and the boat is thrown side to, this speed will be partly translated into roll momentum. And then the boat would probably be better off without the keel.

This does not mean the boats are less safe, only that they need different tactics in bad weather.

[Seabeau]

Originally Posted by MartinR

That is evidence that you have a seaworthy boat, but not that this is superior to keel boats or that a shallow draft is safer than a deep. If you look at full keel boats from the same time, they can easily lie ahull or heave too under very bad conditions without being rolled. I have had both a Colin Archer (external ballast) and a Bristol Channel Pilot Cutter (internal ballast). I have been out in very bad weather and never experienced even close to a knock-down. There is normally no need to sail these boats actively in storm conditions as it is with modern boats. They drift sideways, create turbulence and induce the waves to break a little bit away from them. But they do not stumble over their keels. Never heard of a knockdown for any of these boats.

Modern type sailboats might do this, but there are other factors in play. With a modern boat you can go two ways, beat up under very much reduced sails, which is safe but very uncomfortable or run at the correct speed, keeping the boat stern on to the waves. Side to most modern boats are inherently unstable. Sooner or later, they will end up with their quarter to the waves, pick up speed and then the broad stern with excess buoyancy is caught by the wave and the boat is thrown side to, this speed will be partly translated into roll momentum. And then the boat would probably be better off without the keel.

This does not mean the boats are less safe, only that they need different tactics in bad weather.

In two publicized severe weather events in the late 1800's, one on the Solient and one off Sandy Hook in the US, further illustrate my point. In each instance several heavy constructed traditional British plank on edge boats were lost, neither they or their crews ever seen again, while the more shallow centerboard or centerplate vessels survived. Traditional lifeboats and certainly modern lifeboats with their internal ballast and no external keels, behave exactly as my boat does. And they are certainly safer in extreme conditions. As far as I'm concerned, modern naval architecture has, in its much ballyhooed quest for better windward ability has also succeeded in making sailboats less safe. PS. Pardon me for saying so, but this discussion is very much "on topic".

[MartinR]

Plank on edge is known to be a very bad configuration, as there is very little actual righting moment provided by the hull shape. Actually, these boats were an abomination. For the opposite argument you can look at the American fishing schooners, where the shallow draft - broad beamers were replaced around the end of the 19th century by deep draft relatively narrow beam boats, that were much safer. I think seaworthiness is a complicated issue, some boats are good, some bad. There are good and bad deep draft vessels, and good and bad shallow draft boats.

I also like the internal ballast configuration, mostly for the sea kindliness. And I would not hesitate a moment before buying a centerboarder, actually I was looking for one, but on this side of the Atlantic they are rare, and it is almost impossible to import boats from the US anymore, due to EU regulations. My current boat, which I bought last year to replace my pilot cutter is also shallow draft, albeit wing keel.

Then there is the additional factor of being able to beat up in bad weather if necessary. That is a point of sailing where deep draft vessels actually are better, and modern boats are actually very good at this, if the owners (and the boats) survive the pounding. If you have to beat off a lee shore, this is essential. And my Colin Archer, with more of a keel was better at this than my pilot cutter. For lying to or running the opposite was true.

I have not tried my current boat in heavier conditions, 12´significant wave height was the highest we have encountered, but she also feels very solid, the ultra light displacement offset by narrow beam, small sail area and shallow draft.

My point is more that seaworthiness is a complicated issue, and it does not come down to one item, like keel depth. Also, if you look at history, boats all over the world have developed differently, adapted to local conditions.

[jimbunyard]

If you can get ahold of a copy of 'Good Little Ship' by Vincent Gilpin, it has a lot of information on this topic, from designer Ralph Monroe, who designed and built boats right around your neck of the woods, and was a contemporary and friend of N. Herreshoff.

[WingRyder]

Originally Posted by Seabeau

... Pardon me for saying so, but this discussion is very much "on topic".

Agree! Please continue.

[john61ct]

Originally Posted by MartinR

All of these figures are calculated, nobody tests the boat to upside down condition.

Never say never

http://www.cruisersforum.com/forums/....php?p=2573991

[WingRyder]

Originally Posted by john61ct

Never say never

Bruce Schwab /Ocean Planet Energy - Cruisers & Sailing Forums

I would love to see Beneteau do that with a Yacht 62!

[robert sailor]

Originally Posted by MartinR

I agree more or less. The wing is not actually helping very much, a little maybe, but probably a bulb would have more or less the same effect. On a race course, the shallow draft boat will always loose, but in real life, that matters little.
If a sea is running, you will anyhow fall off a few degrees for comfort, and then there is little in between. And most cruising boats do not do much upwind sailing anyhow.

I was just looking at how this translates to handicap. For example Bavaria 42, full draft has a SRS of 1.0061 while the shallow draft version has 1.0043. These are partly empirical values. This translates to the shallow draft version being about 2% slower around a race course, probably you loose 4% VMG upwind and nothing downwind. This is a lot when racing, but not much when cruising, as most of the time the boat is not sailed optimal anyhow.

Nothing wrong with your thinking as if you are going upwind in reasonably strong winds offshore it's best to foot off and slow down a little so your riding over the waves rather than punching into them. A deep draft boat will have a much better vmg than a shallow draft in these conditions because when your sailing as high as you can in a shallow draft the deep keel is actually on a close reach. The shallow draft has even more leeway in these conditions so the difference between the boats is probably closer to 10 plus degrees. Yes I know gentlemen don't sail to windward but if your heading home from Hawaii you'll sail for around 5 days hard on the wind before being able to foot off. I've made that trip too many times to not know how one boat reacts compared to another. In the end everyone makes it, for some it's just easier. One other thing, shallow draft boats do their best sailing upwind as fast as they are able, this gives them their best vmg but when you slow them down as you would in the open ocean in stronger breezes they go upwind like a straw bale.
Right now we are sailing a shoal draft boat with a Scheel Keel, one of the better ones but my friend with exactly the same boat but a deep keel kills us going upwind offshore. Personally i prefer deep draft boats if you delight in sailing they just sail better but but we chose the boat by a different criteria and the keel just went with an otherwise very nice boat, we would do the same...the keel is secondary in my opinion.

[MartinR]

Originally Posted by robert sailor

Personally i prefer deep draft boats if you delight in sailing they just sail better but but we chose the boat by a different criteria and the keel just went with an otherwise very nice boat, we would do the same...the keel is secondary in my opinion.

Seems we are in about the same situation. The keel came with the boat. Also, at least my boat is very sensitive to correct trim, wind angle, helm. The wing keel stalls easily, and when it is stalled, the boat makes leeway like a dutch bathtub.

To summarise the thread for the OP:
Shallow draft boats are seaworthy
Total performance hit is about 2-3%
Upwind double this, more in a seaway
downwind, no loss of performance
For racing the boats handicap adapts to this.

The advantage of shallow draft keels is the possibility to reach places not possible for deep draft boats, but in reality, in most places there is little difference in this also.

[WingRyder]

Originally Posted by MartinR

Seems we are in about the same situation. The keel came with the boat. Also, at least my boat is very sensitive to correct trim, wind angle, helm. The wing keel stalls easily, and when it is stalled, the boat makes leeway like a dutch bathtub.

To summarise the thread for the OP:
Shallow draft boats are seaworthy
Total performance hit is about 2-3%
Upwind double this, more in a seaway
downwind, no loss of performance
For racing the boats handicap adapts to this.

The advantage of shallow draft keels is the possibility to reach places not possible for deep draft boats, but in reality, in most places there is little difference in this also.

Thanks! That is what I'm taking from this thread. I have zero interest in racing, and I am mostly concerned with a shallow keeled boat's ability to cross the Atlantic, if needed. As I have said, my 10 year plan is to coastal sail the Atlantic seaboard of the US, then once I retire, my dream is to sail to Europe and the Med. I fully intend to stay close to the US, and have no intentions (right now) of sailing around the world. I would LOVE to see the south pacific, but I think it would cheaper, for me, to rent a boat, in the few places I want to go, than take my own boat there. I am an airline employee and will have ridiculously cheap travel benefits for life. So, flying to a destination, and renting a boat, is a fairly cheap option, compared to sailing there, ... accounting for the time, effort and risk involved. [flight crew call it the '3f's rule']

I love watching this thread unfold, `for a wealth of knowledge and experience that is above my level of consideration, ... yet has given me another topic to research and understand.

I am still on the doorstep of my journey, I have my ASA 101/103 course booked for May. I have been trying to absorb as much information as I can, without a sailboat underneath me! I am here, on CF, to ask questions, but in my ignorance, I'm learning what questions are relevant to ask!

~Harrison.