Stability curves for 25D

[Martinhilldpo]

Does anyone have stability curves for a 25D? Would love to see them if anyone has them.

[mgphl52]

The old 'Performance Statistics Compared' link is no longer valid.
However you can still get the same data here.

Comparing 'Capsize Ratio' (lower is better) and 'Motion Comfort' (higher is better) between CD25D vs CD25, CD26, CD27 & CD28 was quite surprising. All 4 had a better (some only slightly) 'Capsize Ratio' than the CD25D and only the CD25 had a lower (slightly) 'Motion Comfort.'

[Martinhilldpo]

The old 'Performance Statistics Compared' link is no longer valid.
However you can still get the same data here.

Comparing 'Capsize Ratio' (lower is better) and 'Motion Comfort' (higher is better) between CD25D vs CD25, CD26, CD27 & CD28 was quite surprising. All 4 had a better (some only slightly) 'Capsize Ratio' than the CD25D and only the CD25 had a lower (slightly) 'Motion Comfort.'

Thank you for that. Not so much the comfort index, I am interested in the angles of maximum GZ and angle of vanishing stability. I would really like to see the GZ curve if anyone has them. It would be nice to know how much she will take. Does anyone know the angles?

[Steve Laume]

I am curious as to how you intend to use these numbers if indeed you find them.

It has been repeatedly said and I believe we can all agree that our boats will take far more than we care to. I have had Raven out in some pretty rough conditions. Sudden squalls when I have gotten caught with too much sail up resulted in excessive healing but I never felt I was in danger of capsizing. I did get slapped broadside by a breaking wave, while down below in my bunk, one time that I had some doubts about how far things were going to go. I have no idea exactly how far over she went but it was definitely pasted 45*. It was a reality check but the boat popped right back up and it didn't happen again.

I just don't know what having numbers would do to change these situations or put your mind at ease before you encountered one. There is a certain point where you have to have some faith and trust in your boat and her designer. I don't believe that trust will ever be betrayed while sailing your Cape Dory, Steve.

[Martinhilldpo]

I am naturally curious as I am a mariner with a fairly comprehensive understanding of stability. I certainly have no intention of getting knocked over past 90 degrees just to see what happens but its always good to know how your vessel will react in an emergency.

I would love to see the curve if any one has it. If not, angles of max righting moment and vanishing stability will give some indication of the vessels ability to self right after a capsize, assuming no progressive downflooding of course. I anticipate the numbers being quite good for my boat. Its a shame the curve was not included in the owners manual.

[Martinhilldpo]

Perhaps I should approach this question from a different angle.

If the CD 25D was sold in Europe it would have to have a CE classification A, B, C or D. Does anyone know what class this boat might fall under, A or B?

Alternatively there is a STIX number which is calculated on a number of factors. Does anyone know what is the STIX number for a 25D?

[David van den Burgh]

Perhaps I should approach this question from a different angle.

If the CD 25D was sold in Europe it would have to have a CE classification A, B, C or D. Does anyone know what class this boat might fall under, A or B?

Alternatively there is a STIX number which is calculated on a number of factors. Does anyone know what is the STIX number for a 25D?

You know, John Vigor might get a kick out of this - or he might have the information you're looking for. Perhaps you could ask him via his blog: http://johnvigor.blogspot.com/

[tjr818]

Sadly, John has stopped posting to his blogspot. He just might still be looking at it though.

[Martinhilldpo]

A little more research suggests that this boat is probably a ce class B Offshore. Class A Ocean requires a minimum displacement of 3 tons.

Cat B requires minimum mass of 1.5 tons and avs not less than (130-(mass x 1.5) and not less than 95.

But, I would still love to see the stability curve if anyone has it

[Martinhilldpo]

Sadly, John has stopped posting to his blogspot. He just might still be looking at it though.

John Vigors excellent book Seaworthy Offshore Sailboats includes a very informative discussion of stability requirements for offshore vessels. His description of inverted stability is very relevant to the shape of the gz curve. Great book highly recommended.