Understanding the Ratios

[callmecrazy]

and also to the OP. I've never head anyone advocate a triton that wouldn't also consider a Vanguard as equally seaworthy. It's just that tritons have a more prominent reputation.

[mitiempo]

crazy

The "capsize ratio" as shown on Sailboat Data is "...just a rough figure of merit and controversial as to its use." That is a direct quote from Sailboat Data.

The best way to find self righting info on a boat is a curve drawn by a designer, which is very common now as it has to be done for every boat sold in the EU for example. I do not know if there is a US regulation. The curve below is for the Malo 37 which shows positive righting to just under 130 degrees. Most offshore capable boats show positive stability to 120 degrees or more.

[mitiempo]

crazy

I agree the Vanguard is as good a choice as the Triton. The Triton have a very strong following, Plastic Classic forum, Tim Lackey's sites, and Atom's site by James Baldwin being 3 that have done a lot for the Triton's popularity.

[Adelie]

Originally Posted by mitiempo

crazy

The "capsize ratio" as shown on Sailboat Data is "...just a rough figure of merit and controversial as to its use." That is a direct quote from Sailboat Data.

The best way to find self righting info on a boat is a curve drawn by a designer, which is very common now as it has to be done for every boat sold in the EU for example. I do not know if there is a US regulation. The curve below is for the Malo 37 which shows positive righting to just under 130 degrees. Most offshore capable boats show positive stability to 120 degrees or more.

Are you referring to SailboatData.com, or some other venue? I looked on SailboatData.com and couldn't find anything.

[mitiempo]

SailboatData.com. After you compare any 2 boats and then click "go away" at the bottom you get the numbers with an explanation of each when clicked. It looks like this:

[mitiempo]

If you go to this page at US Sailing Sailboat Design and Stability
they explain all the factors that relate to stability.

Here are links to allow you to calculate both the capsize ratio and the estimated angle of vanishing stability.

Capsize Formula
Angle of Vanishing Stability

Pretty interesting site.

[Adelie]

Originally Posted by mitiempo

SailboatData.com. After you compare any 2 boats and then click "go away" at the bottom you get the numbers with an explanation of each when clicked. It looks like this:

I haven't ever seen a 'compare' function or button on SailboatData. How do I use it or find it?

I assume I will see the "Go Away" button when I figure out the 'Compare' thing.

[mitiempo]

Sorry i just realized it was Sail Calc. Sail Calculator Pro v3.53 - 2500+ boats

Apologies.
.

[Adelie]

Originally Posted by mitiempo

Sorry i just realized it was Sail Calc. Sail Calculator Pro v3.53 - 2500+ boats

Apologies.
.

No big. I wondered if it was Sailcalc, but didn't have the URL handy to check. Thanks for the URL.

I checked the AVS for the Pogo 10.5 at the USSailing link. Per their formula, the AVS is 116* and change, but the site indicates depth of keel is something not in the formula that would change the result. Given that it draws over 9' it probably breaks 120*. Given that it is a European boat it probably wouldn't be allowed offshore with an AVS below 120.

[mitiempo]

In Europe are you actually restricted from going offshore if the boat is not Category 1? Or does it just determine what the boat is sold and described as?

[swagman]

Originally Posted by s/v Beth

I think we see eye to eye b. See my second post. I am not trying to offend the production boat crowd, just saying I am going to be out (have been out) in blows, and this is what I look at...

With respect, if you only choose an offshore boat by the number you see out there 'doing it' then you're going to choose a production boat like Jeanneau / Beneteau because they would easily be in the majority who cruise safely round the globe.

Facts are (unless you aim to sail the lower Oceans) cruising routes see light favourable winds 95% of the time. Not many cruisers risk bumping into icebergs or even set out to sail in storm conditions. Knowing all that, IMHO the lighter, airier, higher load carrying, and generally better value production boats make sense. Let's face it, cruisers sailing heftier boats usually admit the truth. Its the designs that appeal to their tastes - and usually they sacrifice the advantages that come with lighter boats to satisfy their desires.

But its not a worry, thank God were all allowed to have differing tastes. An anchorage or harbour filled only with AWBs would be boring indeed. As would this forum:-)

Enjoy your choices,

John

[goboatingnow]

Originally Posted by mitiempo

In Europe are you actually restricted from going offshore if the boat is not Category 1? Or does it just determine what the boat is sold and described as?

Portugal I beleive does restrict sail area by boat design. But as a general answer is that RCD categorisation has no effect on sailing destination. It merely " attempts" to provide you with a design guide.

Dave

[goboatingnow]

Originally Posted by Adelie

No big. I wondered if it was Sailcalc, but didn't have the URL handy to check. Thanks for the URL.

I checked the AVS for the Pogo 10.5 at the USSailing link. Per their formula, the AVS is 116* and change, but the site indicates depth of keel is something not in the formula that would change the result. Given that it draws over 9' it probably breaks 120*. Given that it is a European boat it probably wouldn't be allowed offshore with an AVS below 120.

Using any single number is a fallacy. See the Stability Curve and AVS for the moody 45DS as an example.

Equally AVS for an OVNI is 110. Yet the boat is widely regarded as the 4x4 of the bluewater crowd.

Cat A does not have a specific stability number requirement. It is beginning to use STIX

Dave

[barnakiel]

Originally Posted by callmecrazy

(...) (because they) have a higher propensity to self right themselves from 180` knockdown.

I am not sure if by seaworthiness we understand (higher) ability to recover from a 180' knockdown. I would suspect, seaworthiness may have more to do with the boat's resistance to be knocked down in the first place.

A seaworthy hull is one thing but when you think of a seaworthy sailing boat one would allow for the presence of such appendages like masts and sails. Would you agree?

Cheers,
b.

[callmecrazy]

Originally Posted by Adelie

No big. I wondered if it was Sailcalc, but didn't have the URL handy to check. Thanks for the URL.

I checked the AVS for the Pogo 10.5 at the USSailing link. Per their formula, the AVS is 116* and change, but the site indicates depth of keel is something not in the formula that would change the result. Given that it draws over 9' it probably breaks 120*. Given that it is a European boat it probably wouldn't be allowed offshore with an AVS below 120.

I was refering to sail calc numbers. Which as you just pointed out, do not take certain things into consideration, like ballast depth, hull shape, keel shape (which is important for performance considerations when comparing the other ratios) etc...

They are good to use when you already know the other factors for comparison. But ultimately, they don't give enough information to make any type of decision as to the seaworthyness of a boat. They can help alot when comparing performance, but seaworthyness, where design is concerned, has many more factors than just ballast,displacement, and righting moment.