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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Stability Index

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MarkV
Deckhand

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6 Posts

Initially Posted - 12/03/2014 : 13:44:49

I am looking for the stability index for the Cat. 25 with swing keel. Also the L/B ratio.

Thanks,

Mark

Edited by - on

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 12/03/2014 : 14:09:07

Not sure exactly what you're looking for, but you might find some of it here. http://www.sailingcourse.com/keelboat/design_winds.htm

Also, the formula for the stability index can be found here, in section 205.2.

http://www.boatdesign.net/forums/attachments/stability/1615d1092834311-ims-stability-index-imsbk4ge.pdf

Edited by - Steve Milby on 12/03/2014 14:21:54

Dave5041
Former Mainsheet Editor

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USA
3754 Posts

Response Posted - 12/03/2014 : 18:01:15

Good luck finding it, but remember that a swinger won't right itself from a full or nearly full inversion. Friction will keep the keel in place somewhere beyond 90º, but it will eventually come crashing into the trunk as you go farther.

Edited by - on

capelyddol
1st Mate

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USA
62 Posts

Response Posted - 12/03/2014 : 20:15:10

Which is a darn good reason for not having one.

Edited by - on

Lee Panza
Captain

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USA
465 Posts

Response Posted - 12/03/2014 : 20:50:27

quote:
Originally posted by capelyddol

Which is a darn good reason for not having one.

Or, depending on your perspective, a darn good reason not to go inverted past 90!

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 12/03/2014 : 21:12:27

quote:
Originally posted by capelyddol

Which is a darn good reason for not having one.

It'll take a lot more than almost any of us will ever see to roll a C-25 to the point the swing keel falls into the trunk. By the time that happens, a C-25 probably will be sinking due to several factors that limit it to the "coastal cruiser" category--swing, fin, or wing keel. And it has proven to be a capable coastal cruiser--meaning when an ocean storm is moving in, find or stay in port.

By various calculated indices, the C-25 should right itself from a 90+ degree knockdown--unless water enters the "dumpster", which is open to the bilge. Then it might return to upright as it sinks to the bottom. The only time I've heard of that happening was around 25 years ago when 14 (as I recall) partygoers were aboard one on a Colorado lake one night, probably all on deck and the cabintop, outweighing the ballast, and putting the C-25 on the bottom of the lake. Bad judgement, not "stability", sank that one.

Edited by - Stinkpotter on 12/03/2014 21:13:14

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 12/03/2014 : 21:12:56

Yeah. It's a good practice to avoid sailing <u>any</u> boat in conditions that might result in a roll-over.

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DavidBuoy
Admiral

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USA
707 Posts

Response Posted - 12/04/2014 : 06:03:42

quote:
Originally posted by Stinkpotter

--unless water enters the "dumpster", which is open to the bilge.

Dave,

Do you know if the dumpster was meant to be open to the bilge? Mine has been pretty sealed with the only "real" penetration at the bottom for the bilge hose which has been sealed against the edge of the hole since I've owned the boat.
When I recently installed the supersub pump and messed with the hose It finally broke the seal and now slowly leaks into the next compartment under the galley sink, which also seems to be sealed off from the bilge compartment.
I wonder where water actually comes from to get into the bilge because every single other hold on the boat seems to be separate from each other. I'm going to need like 20 more bilge pumps.[/rant]

But really I thought the dumpster was to be sealed which was why I've been hesitant about cutting a hole to install a 12v vent fan somewhere under the galley sink and installing a vent possibly in the fuel locker. The mildew in the locker has rendered it mostly unusable and I want to take it back for storage.

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 12/04/2014 : 08:19:52

quote:
Originally posted by DavidBuoy

Dave, Do you know if the dumpster was meant to be open to the bilge?...

Mine was a fin keel, and I don't have it any more so can no longer see what I'm talking about (and therefore might not know what I'm talking about...

), but here's what I remember:

1. Water that leaked from my cockpit scuppers into the area below the quarterberth on one side and the dumpster (sail locker) on the other side all migrated to the "sump"--the molded keel stub to which the lead fin keel was bolted. That's the lowest part of the bilge on the FK model.

2. While there was a plywood bulkhead between the dumpster and the quarterberth, I do not recall that it was sealed to the hull. I ran wires and did some other things down there, and no longer have a clear picture, but my impression was the dumpster was not designed to be a watertight compartment.

Even if the dumpster were water-tight, if the boat capsized to port and the locker opened, having been completely inside it, I suspect it would swallow enough water to seal the boat's doom. The companionway would probably become submerged, and down she'd go. That's why I always kept a padlock, even unlocked, on the hasp for that locker. But I never came close to the situation I'm describing. I'm convinced it would take a 6'+ breaking wave on the starboard beam to get to that point. So I stayed away from those...

(You know, "coastal cruiser".)

Edited by - on

hewebb
Admiral

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USA
761 Posts

Response Posted - 12/05/2014 : 06:35:22

I have a wing keel and was setting quite comfortable on a fairly breezy day-when all-of-a-sudden I was hanging on to the life line to stay on the boat. Not sure how far over she went but I had about 4 or 5" of water in the cockpit when things settled down and the mast pointed up again. I have been told that Catalina 25's will right themselves quite well even if the spreader gets wet.

Edited by - hewebb on 12/05/2014 06:36:04

Voyager
Master Marine Consultant

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USA
5231 Posts

Response Posted - 12/05/2014 : 19:32:59

Solution: Pin that fender locker shut with a clevis and cotter pin. Cheap insurance!

Edited by - on

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