Keel types for transocean

[grep]

Hi wonderful people.


I'm daydreaming yachts and one day will pull the trigger.


I've found myself leaning towards long full / modified keels as I'd definitely want to be able to comfortably do a transatlantic or even transpacific crossings.


There are so many more fin keel models out there! How much of a poor decision would it be to get something like a Benteau 38 or 33?



My budget would probably be in the £40-£70k range.

[boatman61]

Having done two solo W to E Transats in Beneteau's, the first on a 321 and the second on a 331 I would say.. No reason not to, as long as its not in winter..
As long as the keel bolts and rudder are sound, along with the rest you should be fine.

[grep]

Originally Posted by boatman61

Having done two solo W to E Transats in Beneteau's, the first on a 321 and the second on a 331 I would say.. No reason not to, as long as its not in winter..
As long as the keel bolts and rudder are sound, along with the rest you should be fine.

That's amazing. You never at all wished it was on a fuller keel for stability or smoother sailing?


Out of curiosity, what would happen if you tried in winter. Would it be outright unsafe or just very uncomfortable?

[boatman61]

The first was mid July from St Martin, the second was late April also from St Martin.. no mega storms, got chased by several waterspouts but no stability issues as such.. mostly winds between 10-15kts and periods of calms so the lighter boat was more useful than a heavy displacement.
Did a solo W to E on a Hunter 37 from NC to the UK and got the ***** kicked outa me between Bermuda and the Azores, that was a May departure..
Its down to the route and season one chooses..
In winter the odds of having the ***** kicked outa you rises exponentially regardless of keel configuration.
Don't get me wrong, I like long keeled boats but fin and skeg have their pluses..

[grep]

Really appreciate the reply. Thanks ��

[Matt Johnson]

Originally Posted by grep

That's amazing. You never at all wished it was on a fuller keel for stability or smoother sailing?


Out of curiosity, what would happen if you tried in winter. Would it be outright unsafe or just very uncomfortable?

Get a out there and test a few different boats and figure out what you like before you focus one way or the other. I know I'm not in the majority, but I personally HATE the motion of a typical full keel boat's hull shape - my wife and I both become seasick with the rolling motion in downwind on those boats. We both prefer the lively feel of a sportier boat. It's worth the test before you commit.

[wholybee]

The motion of a boat is much more determined by the hull shape and other parameters than be keel type. To choose a keel type based on expected motion of the boat is just wrong.

A modern fin keel boat, that is well designed for ocean sailing and well built, will have a better motion and better handle big swells and waves than most classic full keel boats. That isn't because of the keel shape, but because of the rest of the design of the boat. And you also need to consider that many older designs were "built to a rule" such that performance and comfort were compromised so that the boat would be rated such that it can sail faster than it's rating and have a racing advantage. Newer boats don't do that.

Note that I also said "well designed for ocean sailing and well built." Not all modern fin keel boats fit that description. A boat built for the charter market in fair weather shouldn't be expected to sail well in the ocean, whether it was a charter boat from 40 years ago, or one from 5 years ago.

I will share a story. I have a classically designed yacht, with a "modified fin keel" and a skeg rudder. It sails well, and I would not describe the comfort as bad. During one passage, through the Mozambique channel from Madagascar to South Africa, the conditions were terrible. I was getting really beat up, thrown everywhere, and bruises all over my body. In a group of about 10 boats several sustained significant damage, broken shrouds, torn sails, a broken furler and a broken boom. One boat that I was friends with, a modern 50 foot fin keel, left same day as me and arrived a day earlier. On arrival when discussing the trip, 3 days earlier while I was getting thrown about and bruised, they were comfortable underway celebrating Halloween by playing dress up with their 4 year old.

[Jim Cate]

FWIW:

Ann and I have now logged well over 150,000 miles, accumulated over 40 year and in three different FIN KEELED yachts, ranging from 30 to 46 feet LOA. We have been through some pretty nasty weather during that time, and yes, it was uncomfortable. I have no reason to believe that it would have been noticeably more comfy in a full keel boat. By the time the winds reach 60+ and the seas 25 ft+ NO small boat is comfy in the real world!

As boatie implied, quality of construction and other design details are far more important than keel shape when out at sea.

Jim

[grep]

Thanks for all the replys and sharing your knowledge. I was getting some blinkers on considering only full keel. I feel like I can look at so many more boats now.

[GordMay]

Originally Posted by Matt Johnson

Get a out there and test a few different boats and figure out what you like before you focus one way or the other. I know I'm not in the majority, but I personally HATE the motion of a typical full keel boat's hull shape - my wife and I both become seasick with the rolling motion in downwind on those boats. We both prefer the lively feel of a sportier boat. It's worth the test before you commit.

Sailing [dynamic] Stability is concerned mainly with rotary motions: the roll or heel of the boat, from side to side, and the fore-aft pitching or trimming motion. The nature of these motions depends on the distribution of mass within the yacht ["moment of inertia"].

Although Roll and Slamming may be more important for SAFETY, it’s vertical Pitch and Heave that contribute most to DISCOMFORT [sea-sickness].
And, it’s, generally, the Acceleration [frequency], and exposure duration, of Pitch & Heave, that incapacitates the crew, more than amplitude.

The faster the motion, the more uncomfortable the crew.

It bears repeating: It's the period of the acceleration, that matters more than the amplitude. The human body is most sensitive, in terms of motion sickness incidence at around 10-second periods (0.1 Hz), and virtually insensitive at periods of 1-sec or thereabouts. O'Hanlon and McCauley's Motion Sickness
Incidence [MSI] curves define the sensitivity, over the whole range, as embodied in ISO Standards for Motion Sickness and Stress 2631-x[2].

Amplitude becomes important, for safety, at the extremes.

Ted Brewer summed up small boat comfort, with his "Comfort Ratio"[1], which provides a reasonable comparison between yachts, of similar type.
Higher values denote a more comfortable ride.
As the Displacement increases, the Motion Comfort Ratio [MCR] will increase. As the length and beam increases, the MCR will decrease.

MCR = Disp ÷ [(0.65 x 0.7 LWL) + (0.3 x LOA) x (B x 1.333)]

[1] “Ted Brewer Presents A Primer on Yacht Design”
Including ‘COMFORT RATIO’
➥ https://www.tedbrewer.com/yachtdesign.html

[2a] “Excerpt of ISO 2631, Seasickness and Fatigue”
➥ https://www.ittc.info/media/8073/75-02-05-041.pdf

[2b] “A review on the effects of motion characteristics on motion sickness incidence” ~ by Suzanne A.E. Nooij
➥ https://pure.mpg.de/rest/items/item_...008627/content

For those who like math’, see also: “Dynamic Stability of a Monohull in a Beam Sea” ~ by Mathew B. Marsh
➥ https://marine.marsh-design.com/cont...ohull-beam-sea