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Catalina/Capri 25/250 Sailor's Forums

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C25 Ratios

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Gloss
Master Marine Consultant

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USA
1916 Posts

Initially Posted - 04/10/2004 : 13:12:08

I did an archives search for the term "ratios" before I posed this question, and got nothing. So forgive me if this topic has been covered before.
I am interested in learning the ratios for our 25's. Like sail area to displacement, capsize screen, and all of the other ratios covered in the design articles, or covered in Calder's book.
Someone once told me that the righting moment for the wing keel is the same as the fin keel. Is this true?
Are there any comparisons out there of the swing, wing, or fin keel? tall, vs standard rig.
I did see some information on the Catalina owners.com site, but it didn't specify which model.
I know that this is a rather arcane issue, but we do have some pretty smart folks in this association, wish I was one of them.

Frank Gloss
Formerly 89WK/TR
85 Ericson 32-3 shoal draft "Molto Bene"

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 04/10/2004 : 15:15:39

Hmmm.. Found some stats posted for the Catalina 25 Fixed Keel. Will dig some more later...

Length 25 feet
Length on Waterline 22 feet
Displacement 4550 lbs
Sail Area 271 square feet

Results:
Capsize Ratio 1.93 anything under 2 is considered good

Sail to Displacement Ratio 15.79 a racer would be over 18, 15 is the
middle of the road for cruisers

Displacement to Length 191 a seaworthy boat should be around 200

Length to Beam 2.76 a seaworthy boat should be around 2.7

Motion Comfort 19.10 (Bluewater Westsail 32 is 43.61)

Weight required to float the boat 1 inch lower 629 lbs

Edited by - on

Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 04/10/2004 : 16:56:18

I did find some ratios on our own website in the Tech section.

Clam, where did you find your stats?

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 04/10/2004 : 19:31:20

Googled on 'C25 + Capsize" it led to some postings from a Yahoo Bluewater Cruising group... where a fellow was asking how seaworthy his C25 was... similar to the questions asked here.

Browsing the thread revealed some interesting thoughts/observations. They used a standard 'seaworthyness formula' that showed most ANY reasonably well found sailboat 25' or longer will be rated to survive in Force 8 conditions.

But some boats will become VERY uncomfortable in that situation.

Edited by - on

EricCS
1st Mate

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USA
40 Posts

Response Posted - 04/11/2004 : 08:21:33

Frank,

There's a page using JavaScript to provide a number of these formula values, and it allows comparison between two boats as well. It's at
http://www.image-ination.com/sailcalc.html.

HTH

Edited by - on

Oscar
Master Marine Consultant

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USA
2030 Posts

Response Posted - 04/11/2004 : 09:29:56

Along these lines there are some good definitions, formulas, and sample calculations to be found here:

http://www.geocities.com/Yosemite/Forest/2727/flicka_formula.html

Oscar
250WB#618 Lady Kay in Venice Inlet, Florida USA.

Edited by - Oscar on 04/11/2004 09:31:48

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 04/11/2004 : 11:33:15

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by EricCS
 
http://www.image-ination.com/sailcalc.html.

HTH
<hr height="1" noshade id="quote"></blockquote id="quote">

Awesome site. Pearson 26s are remarkably similar to our boats, just better in the heavy stuff.

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 04/11/2004 : 12:07:04

Wow...on paper, our boats rate almost exactly like... A Macgregor 26X !

Edited by - on

Doug G.
1st Mate

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USA
49 Posts

Response Posted - 04/11/2004 : 16:09:03

Neat site. Compare C25 to C27. That was a surprise to me that there is more LWL on the 25.

Edited by - on

Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 04/11/2004 : 19:04:59

Don't tell me that our boats rate like a MacGregor.

Our values will plummett faster than Nasdaq

That is a cool site though

Edited by - on

oldsalt
Admiral

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USA
578 Posts

Response Posted - 04/11/2004 : 19:29:24

I don't believe these numbers where intended to compare a true sailboat with a slab sided motorsailor like the Mac 26x which has a hull design which is more like a semi planing powerboat below the waterline and a 50 hp outboard hung off the stern.

And the numbers don't take the way a vessel is constructed into consideration either.

A more realistic comparison would be to compare the Catalina 25 with the Mac 25, and the tables do show a huge difference between the two.

To give credit where credit is due, there are two Mac 26x's in my marina and they can really haul tail under power, in fact, it's weird to see what appears from a distance to be a real sailboat, scoot along at such a clip under the iron genny, but I don't think a Mac 26x can perform under sail as well as the numbers predict since the formulae were intended for sailboats, not powerboats with masts.

Edited by - oldsalt on 04/11/2004 19:45:54

tmhansen
Captain

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USA
397 Posts

Response Posted - 04/12/2004 : 02:10:11

Frank we must read the same magazines. This topic has been on my mind as well. Last night I collected the formulas from Calder's recent article in Sail as well as some others that are used in Good Old Boat (Ted Brewer
's Comfort index). I have a spreadsheet that compares my Laguna 26, a Pacific Seacraft 25, a Catalina 25 swing short rig, a Catalina 25 swing tall rig, a Catalina 25 wing tall rig, and a Catalina 250 wing. I'd be willing to share it with everyone but how? I could email to someone with a web page. Oscar? Arlyn?

By the way I don't believe that with standard specs such as beam, LWL, displacement it is possible to determine the righting moment. That is a function of the location of the ballast, the center of gravity of the boat and so on.

Edited by - on

Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 04/12/2004 : 18:12:37

Todd,
I think it was someone with Catalina who told me about the righting moment being same for fin and wing. It is kinda hard for me to imagine that.
I know that the Macs and Cats don't compare at all. While I was in the keys I looked at a Mac docked at the marina in Bahia Honda state park, and the chainplates were pop riveted on to the deck. Be very, very, afraid.

Edited by - on

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