Full Keel to Fin Keel.

[slap]

Had a 32 foot "full keel" boat. Designed weight: 10300 lbs., draft of 4.5 feet. Replaced it with a 32 foot (shallow draft) fin keel boat. Designed weight: 10400 lbs, draft of 4.75 feet. New boat is (according to PHRF) about a minute and a half per mile faster. New boat has about twice the interior room, sails better, maneuvers better, goes upwind and downwind better. I'd have to go into nit pick categories to find anything that the old boat had better than the new boat - almost like after a 73-0 drubbing the only thing the losing team had was better looking uniforms.

Wife loves the new boat. I tease her all the time that I've downsized because the new boat is a couple of inches shorter than the old boat.

If anyone is wondering what the two boats are, the old boat was a Pearson Vanguard. The new one is a J/32. And the new one is so much easier to sail, especially single handed.....

[Jim Cate]

There is a lot of lingering prejudice against fin keel boats for cruising, prejudice of unknown(to me) origin If I had not personally logged over 150,000 miles in fin keeled yachts I might be swayed by the rhetoric. I'm not...

Jim

[thomm225]

Originally Posted by slap

Had a 32 foot "full keel" boat. Designed weight: 10300 lbs., draft of 4.5 feet. Replaced it with a 32 foot (shallow draft) fin keel boat. Designed weight: 10400 lbs, draft of 4.75 feet. New boat is (according to PHRF) about a minute and a half per mile faster. New boat has about twice the interior room, sails better, maneuvers better, goes upwind and downwind better. I'd have to go into nit pick categories to find anything that the old boat had better than the new boat - almost like after a 73-0 drubbing the only thing the losing team had was better looking uniforms.

Wife loves the new boat. I tease her all the time that I've downsized because the new boat is a couple of inches shorter than the old boat.

If anyone is wondering what the two boats are, the old boat was a Pearson Vanguard. The new one is a J/32. And the new one is so much easier to sail, especially single handed.....

The J/32 appears to be an awesome boat, but it does have a capsize screening formula above 2.0

I thought I had read where after Fastnet 79 all the race boats at least in large sanctioned races like that had to have a capsize screening formula below 2.0

Pearson Wander Capsize Screening Formula is 1.75

I guess it all depends on what type sailing you plan to do as to which boat you buy

[malbert73]

So funny all of the myths. My family and I have owned 2 full keel and 2 fin keel boats. 1 full keel one (hinckley B40) and 1 fin keel (Tartan 40) have bolt on external ballast done very robustly. And my luders 33 had encapsulated ballast as did our 30 foot fin keeler when I was a kid.
As for hull shape tankage storage etc. has nothing to do with keel but with hull design. The full keel eta had slack bilges. Island packet has fin keel type hull with full keel. There are many slack bilged “full keel” type boats back in CCA era like Morgan’s and I think Ericson 41.
Tracking has more to do with design than keel. A short chord “full keel” which is really fin with attached rudder can actually be a handful to steer with unbalanced rudder that is well forward of stern

[malbert73]

I am sure this boat tracks better


Than this one

[double u]

...the only possible advantage of a full keel that comes to my mind is the protection of the rudder as you are sliding over a rock...
&BTW: very well put, malbert73!

[Rex Delay]

Originally Posted by malbert73

I am sure this boat tracks better
Attachment 200971

Than this one
Attachment 200972

True but the J boat is very nice on the eyes.

[wingssail]

Originally Posted by TeddyDiver

You don't mind if i chime in too? The keel is the only place where the wetted area is minimised. The flat bottom (and square transection) is to minimise weight ie displacement and maximise the hull internal volume. The minimised weight allows less weight and area with smaller keel and thus a cheaper boat per living spaces volume. The rest is marketing BS..

Teddy

Actually the displacement of two hull shapes can be equated to the area of the cross section and the wetted surface of two hull shapes can be equated to the edge of the cross sections. In the diagram below (not to scale, but approximate) you can see that hull shape A has much more displacement than hull shape B. If we reduce the draft of the hull (hull shape C) to a similar displacement as B (& D) we can see that the line around the hull is less for the fin keel shape.

The exact differences can be calculated with the geometry calculator here:

https://www.bing.com/search?q=volume...FORM=QBRE&sp=2

When you add to it the differences in the keel area (approx. 30sq ft x 2 sides=60) in the full keel to 40 (approx. 20 sq ft x 2 sides) the fin, you will see that the fin keel boat has approx. 40% less total surface area than the full keel boat.

A third shape, the modern light weight boat with flat underbody and wide sections aft (not shown) has more wetted surface than either of the other two.

You can play with the shapes and actual dimensions but the general rule holds true.

[malbert73]

Originally Posted by Rex Delay

True but the J boat is very nice on the eyes.

Yes and so is the ericson. Point is the keel and rudder don’t dictate the Hull shape, overhang, aesthetics, etc

[Tayana42]

Consider the Alerion 41 as an example of a traditional looking design with a modern underbody.

https://sailboatdata.com/sailboat/alerion-41

[TeddyDiver]

Originally Posted by wingssail

Actually the displacement of two hull shapes can be equated to the area of the cross section and the wetted surface of two hull shapes can be equated to the edge of the cross sections. In the diagram below (not to scale, but approximate) you can see that hull shape A has much more displacement than hull shape B. If we reduce the draft of the hull (hull shape C) to a similar displacement as B (& D) we can see that the line around the hull is less for the fin keel shape.

The exact differences can be calculated with the geometry calculator here:

https://www.bing.com/search?q=volume...FORM=QBRE&sp=2

When you add to it the differences in the keel area (approx. 30sq ft x 2 sides=60) in the full keel to 40 (approx. 20 sq ft x 2 sides) the fin, you will see that the fin keel boat has approx. 40% less total surface area than the full keel boat.

A third shape, the modern light weight boat with flat underbody and wide sections aft (not shown) has more wetted surface than either of the other two.

You can play with the shapes and actual dimensions but the general rule holds true.

Your shapes are a far too simple for anything but as a basic concept. What comes additionally is the that a boat with flat underbody (=less displacement) must be wider to have a way for stability as there's not as much weight in the keel as with narrower heavy displament boat. Thus the wetted surface of the hull is about the same. The only real difference being the surface area of the keel. So it's not only the shape, it's also all dimensions..

[Paul L]

Originally Posted by thomm225

The J/32 appears to be an awesome boat, but it does have a capsize screening formula above 2.0

I thought I had read where after Fastnet 79 all the race boats at least in large sanctioned races like that had to have a capsize screening formula below 2.0

Pearson Wander Capsize Screening Formula is 1.75

I guess it all depends on what type sailing you plan to do as to which boat you buy

Theorectical formulas don't tell the full story. It's interesting that you bring up the 79 Fastnet storm and J-Boats, as there were two J/30s in the storm that survived just fine; far better than many of the othet boats.
Here's their story
http://www.jboats.com/j30-articles-r...-fastnet-storm

[Paul L]

Originally Posted by jharding

The idea of a lighter faster boat with modern electronics being able to avoid storms is great. But it just doesn't work that way, you will still get caught in storms, I love my seakindly, long keel, heavy boat. It always does what it should and makes me feel comfortable and confident, I'll take that any day.

If you mean by avoid storms that they see one on the forecast, put it in high gear and run to smooth saftey, then I agree with you.
The more important issue is that a faster boat gets you far less exposure to storms. If you leave on a passage like the Tonga to New Zealand run, the first half of the forecast weather is usually pretty reliable. Each day after that it becomes more and more of a crap shoot. If a modern, fast cruiser does the trip in 7 days versus a slower, full keeler in 10 days, the slower boat is exposing itself to unforecasted weather significantly longer.

[TeddyDiver]

Originally Posted by Paul L

If you mean by avoid storms that they see one on the forecast, put it in high gear and run to smooth saftey, then I agree with you.
The more important issue is that a faster boat gets you far less exposure to storms. If you leave on a passage like the Tonga to New Zealand run, the first half of the forecast weather is usually pretty reliable. Each day after that it becomes more and more of a crap shoot. If a modern, fast cruiser does the trip in 7 days versus a slower, full keeler in 10 days, the slower boat is exposing itself to unforecasted weather significantly longer.

And what might that modern fast cruiser happen to be what's so much faster? Take two boats about the same value or size.
It's also a bit funny how many folks on "modern fast cruiser" tend to wait two months for a weather window and afterwards brag how fast they made the passage..

[double u]

“...seakindly...“
...please define this rather “elastic“ term! IMHO its BS.
Lets take a totally different approach:
If, the present boat marked, new or used, being .what it is, we we want to buy a long keeled boat our choices are extremely limited:
1. New boat: hardly a large selection, quite expensive
2. Used boat: will be quite old, more maintenance, labour & investment -wise ( which means the “comfortable seakindly motion“ will be somewhat offset by more work at anchor/in port)
So for many people (like us), there is the same lack of choice fin-full keel, wheel-tiller, saildrive-shaft, sweptback spreaders-spreaders 90* (BTW:I hate the sweptback...)