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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Speed

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Dick Johnson
1st Mate

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USA
40 Posts

Initially Posted - 05/29/2006 : 18:37:48

I was taking "Lagniappe" to get her bottom cleaned and painted. On the way to Jerrett Bay we decided to run with the swing keel down and then up. Down we did 4.2 knots and up we did 5.0 knots. The wind direction, tide and motor all remained constent.

Catalina SK, # 5512

Richard Johnson

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 05/29/2006 : 19:34:00

I am guesssing you were heading downwind or at least broad reaching.

You stated the Motor remained constant, what do you mean by that?

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stampeder
Master Marine Consultant

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1608 Posts

Response Posted - 05/29/2006 : 19:37:56

This topic was covered last summer - when the survey said 'this boat is faster with the keel down'.
I think the rationale was that the boat is better balanced with the keel down. Thanx for posting your experience, I look forward to hearing the experts weigh-in.

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Lightnup
Master Marine Consultant

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USA
1016 Posts

Response Posted - 05/29/2006 : 22:14:24

It's slightly faster with the keel up because there's less weight in the boat. There's less weight in the boat because you just lost about a pound and a half of sweat cranking the *%&^#)*$ keel up. (Just my observation based on personal experience on a warm, muggy, windless day in S. Florida.)

Steve

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britinusa
Web Editor

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USA
5404 Posts

Response Posted - 05/30/2006 : 06:36:10

How 'Clean' is your keel?
If it's groty with barnicles etc. then there's the friction.
Of course, could be that the foward surface area of the keel up is significantly less then when it is down. On the 250, which has more of a blade swing keel that is about 2" thick, the forward facing surface area when raised is probably only about 10% of lowered area. that's 90% more keel to drag through the water.
Now if you want to get into the lamina flow theory.....

Paul

ps. I looked up the name of your boat... very nice!
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">“an extra or unexpected gift or benefit.” <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Edited by - britinusa on 05/30/2006 06:38:20

IndyJim
Navigator

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USA
130 Posts

Response Posted - 05/31/2006 : 20:28:04

Dick,
Since I used to live in SW Louisiana, I know exactly what the name of your boat means. I actually thought about naming my C-25 the same thing several years ago. Am I correct that Lagnippe roughly translated from Cajun to Midwest English means "A little something extra"?

I'll try the same approach the next time I'm out sailing with the keel up and down and compare speeds. I'll let you know what the results. Laissez Le Bon Temps Roulez!

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duanewolff
Master Marine Consultant

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50022 Posts

Response Posted - 05/31/2006 : 20:36:54

Be sure to measure speed over ground and also check your pointablility. Also sail on different points, a beat, a run etc.

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Derek Crawford
Master Marine Consultant

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USA
3321 Posts

Response Posted - 05/31/2006 : 22:47:09

I have no experience with a swinger C25, but used to race a swing keel C22. It was definitely faster <u>downwind</u>with the keel raised - however, only an idiot would race it to weather without the keel down (that's how we sunk it...keel down but not locked, boat broached in a 35 mph gust and turtled as the keel collapsed).
Incidentally, the reason that the swing keel and the fixed keel have the same PHRF rating, is that the swinger is faster to weather but the fixed is faster downwind. And because they have the same rating we make the swinger keep it down throughout the race.
Derek
Chairman, PHRF of the Alamo (Canyon Lake)

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stampeder
Master Marine Consultant

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1608 Posts

Response Posted - 06/01/2006 : 10:58:23

I think we need clarity from Dick. Were you motoring or sailing, on the way to Jerrett Bay?
And for the experts, does it make a difference, motoring or sailing on a run with the keel up or down. When this topic was covered previously, the discussion was based on motoring back to port to get out of a storm. The question being, is it faster to motor with the keel up or is it faster with the keel down?

Edited by - on

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 06/01/2006 : 12:23:52

I'm trying to figure out why the C25 swing keel would be any faster with the keel up than with it down. In order for the boat to be faster, you have to either remove some of the keel's wetted surface from the water, which would then reduce friction, or you have to change the orientation of the keel in a way that reduces friction or water turbulence.

If I remember correctly, when the C25's keel is cranked up, it doesn't retract into the hull very much, if at all, so, cranking it up doesn't significantly reduce the wetted surface. The only other difference is that, instead of presenting the keel's long, fair, leading edge to the water flow, you are presenting the keel's blunt stub end to the water flow. I don't think either of these changes would account for a .8 kt speed difference, which is fairly substantial.

Also, years ago a friend and I checked the speed of his C25 swinger up and down, and we couldn't find any significant difference on an inland lake with no significant current.

I can't understand why you were able to measure a difference of .8 kt, which would be a larger differentiation than the orientation of the keel would suggest. If you were checking the speeds at substantially different water depths, that might have accounted for a considerable difference in the speed of the tidal current.

Edited by - on

Dick Johnson
1st Mate

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USA
40 Posts

Response Posted - 06/01/2006 : 20:08:00

Thanks for all of the responses. Yes, Langiappe does mean a little something extra. You are very wise. It's very seldom seen. An example of a langniappe is when the owner of a restaurant gives dessert with a meal.

We were motoring and the boat was grungy. I mean very grungy. Since we are off the ocean, we do have brackish water. Growth on the swing keel should not be a factor since it's there when the board is up or down. The difference is up or down.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 06/01/2006 : 20:44:19

From past topics, it appears that the position of the swing keel significantly affects the orientation of the boat as it sits on her lines. With the keel down, the bow sinks deeper in the water, causing water to collect in the forward part of the cockpit and the scumline to be a few inches higher than normal at the bow. Maybe this somehow plays into the equation.

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KYD516
Deckhand

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USA
24 Posts

Response Posted - 06/02/2006 : 08:48:55

I have fixed keel with a clean bottom, non-balanced rudder. I was sailing close-hauled with a 155 genoa, full main, moderate tension on the backstay in about a 12k breeze and was doing about 5 to 5.2knots. Does that sound about right?

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 06/02/2006 : 14:40:54

If you close reach in those conditions you ought to be at hull speed, close hauled... I suppose, but I would think they would be a bit higher.

Edited by - on

Gary B.
Admiral

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USA
969 Posts

Response Posted - 06/05/2006 : 00:39:35

I have tried this experiment, too, motoring on my swinger against strong current in the Columbia River. It seemed to me to make NO difference one way or the other in terms of the GPS speed over ground.

One thought I had was: where is your knotmeter impeller? Seems to me that FLOW of water past it might differ if it was somewhere AFT of the keel pivot. Mine is just aft of where the keel lives when UP, and it's off to one side a bit. I think the water flow over the impeller changes some when the keel is up or down...or even on different tacks. The GPS measurement that tells you what you are doing over ground might well give different
results.....

Gary B.
s/v Encore! #685 SK/SR

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jlguthri
1st Mate

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USA
93 Posts

Response Posted - 06/08/2006 : 15:03:54

Jarrett Bay? I just got mine pulled up at Bock's. Are they cheaper? I'd probably stick with Bock if I can, as my Grandfather used to work there for a long time...

You keep your boat on base?

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