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Catalina/Capri 25/250 Sailor's Forums

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Can I make 10kts with sails and motor?

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djn
Master Marine Consultant

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USA
1561 Posts

Initially Posted - 04/20/2006 : 09:48:11

Hi All, I was just thinking about the dynamics of sailing and wondered if I was making 5kts with my sails set wing on wing, then dropped my motor and went to 3/4 thottle, would the boat do 10kts? Or would I make 6kts and burn up gas? Cheers.

Dennis
No Boat
S.E. Michigan

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 04/20/2006 : 10:05:15

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by djn
 Can I make 10kts with sails and motor? <hr height="1" noshade id="quote"></blockquote id="quote">

Not unless your are also being pushed by either hurricane winds, a tsunami, or down Niagra falls!

Without the assistance of some outside force, the displacement hull of the C25 will not get much over 6.5. (Although I did do 8.4kts once downwind in a wicked blow!)

You will probably get 10kts SOG on your trip down from Port Huron though.

Edited by - dlucier on 04/20/2006 10:17:11

existentialsailor
Master Marine Consultant

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USA
1180 Posts

Response Posted - 04/20/2006 : 10:10:04

No, you need a Capri to be able to do 10 kts, and that is without the motor!

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Ericson33
Admiral

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USA
892 Posts

Response Posted - 04/20/2006 : 10:22:21

Yep, Nothing like passing the fleet downwind, with the tiller humming, and the other boats complaining about the wake we are throwing

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 04/20/2006 : 10:26:39

Sure - what kind of knots are you thinking about....

Bowline, half hitches, reef knots...Sheep shank, that's a real good one.

There are very few instances where you will get major benefit from Motor sailing. None of them will register a speed higher than hull speed...

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 04/20/2006 : 12:12:12

I've seen 9 knots for a short time under spinnaker in strong winds while surfing down 6 foot waves. That's the only way its going to get over 6.5 - when wave action is cancelling out the natural hull wave.

Watch closely, keel sailboats and other displacement craft are sitting in a wave of their own hull length. It gets nearly impossible to climb out of this wave - you needs lots of power to push the bow up and over it. When that occurs, it is called planing. Flat bottom power boats do it and some sailing race boats with very flat bottoms and very deep narrow fin keels.

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johnsonp
Admiral

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USA
606 Posts

Response Posted - 04/20/2006 : 14:05:55

With the tide and the current.
SOG 8 knots
paulj C250 WK #719

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existentialsailor
Master Marine Consultant

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USA
1180 Posts

Response Posted - 04/20/2006 : 15:26:45

Jim,

You mean a flat bottom and keel like this?

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Ericson33
Admiral

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USA
892 Posts

Response Posted - 04/20/2006 : 16:21:43

I was reading a year ago on the Sj24 sire a couple of engineers talking about this, the faster you go the more the hull is sucked down into the water.

Rick the boat looks really smooth

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Brooke Willson
Admiral

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USA
983 Posts

Response Posted - 04/20/2006 : 16:42:09

I've done 6.7 knots indicated on the GPS on a beam reach -- but the tide was probably giving me a knot or more. So, yes, you can do 10 knots if you have a 4 knot current/tide.

Remember Dennis, in a powerboat you get there quicker. In a sailboat, you're already there.

Brooke

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djn
Master Marine Consultant

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USA
1561 Posts

Response Posted - 04/20/2006 : 17:13:15

Hi Brooke, I am not really concerned about the speed, it was just a theroetical thought.

Hi Don, yep, the St Clair river is running at about eight kts so I should see some come speed over the ground. When the boat was taken up to that marine, they spent six hours pushing through the current. Cheers.

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existentialsailor
Master Marine Consultant

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USA
1180 Posts

Response Posted - 04/20/2006 : 17:22:06

Chris,

That's the barrier coat before I put VC17 on. That was last spring, I'm worrking on a few spots I wasn't satisfied with this spring as well as having eliminated the thru hull for the sink. If I can get a puck transducer to work this summer, next spring I'll eliminate the protrusions for the depth sounder and the knot meter.

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Captain Bill
Navigator

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USA
148 Posts

Response Posted - 04/20/2006 : 19:05:11

Dennis,

When we were bringing the "Mary Joyce" home after purchase we had a good wind from starboard and the Honda 9.9 going almost full blast trying to get in before dark. The wind was from the starboard rear and we had small waves in the Pamilco. Our GPS constantly measured 6.9 to 7.1 depending where we were on wave.

Bill

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Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 04/20/2006 : 19:33:08

so what is the hull speed for the Capri?

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britinusa
Web Editor

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USA
5404 Posts

Response Posted - 04/20/2006 : 21:14:40

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Hi All, I was just thinking about the dynamics of sailing and wondered if I was making 5kts with my sails set wing on wing, then dropped my motor and went to 3/4 thottle, would the boat do 10kts? Or would I make 6kts and burn up gas? Cheers.<hr height="1" noshade id="quote"></blockquote id="quote">

Dennis,
Wing on Wing (Goose wing to some) means you are running from the wind, not the fastest point of sailing (The max speed if the boat was capable, would be the wind speed) As you approached wind speed, then the power to the sails drops (Imagine if you were powering along at 10knots (SOG) from a 5knot wind, your sails would be backing!)

Paul

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Ericson33
Admiral

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USA
892 Posts

Response Posted - 04/20/2006 : 21:25:34

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Gloss
 so what is the hull speed for the Capri?
<hr height="1" noshade id="quote"></blockquote id="quote">

Hull speed by the numbers is 5.8 knts, I have seen 8 knots with just the main sail up in 35 knot winds going dead down wind. My knot meter was off last year when we sailed the MS Regatta, but I have never felt a sailboat set up and take off like we did. LOOK at this

Here is the link to the post

http://www.catalina-capri-25s.org/forum/topic.asp?TOPIC_ID=10603

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 04/20/2006 : 23:41:36

Yes, Capri25, like that, or, like this

WIndquest, at PHRF -235, the fastest boat currently entered in Newport-Ensenada. Indiscipline, at 228, is the slowest.

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oldsalt
Admiral

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USA
578 Posts

Response Posted - 04/22/2006 : 09:51:21

Once while sailing against the tide in the narrows under the Verrazano Bridge between the upper and lower bays in New York Harbor, I was making a good 5 Knots on the knot meter and Silver Girl had a really nice "bone in her teeth".

Problem was; I was actually sailing "backwards" and losing ground against some familiar landmarks.

If I was sailing in the other direction it would appear that I was far exceeding hull speed by GPS, but not speed through the water.

So, the answer is yes, I believe you could exceed 10 knots over the bottom, but not through the water.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 04/24/2006 : 11:41:10

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Capri25
 I was reading a year ago on the Sj24 site a couple of engineers talking about this, the faster you go the more the hull is sucked down into the water.
<hr height="1" noshade id="quote"></blockquote id="quote">
Hmmm... That's one theory, I guess. The explanation I buy is essentially what Jim B. described: There's a speed at which the size, period, and angle of the bow wave makes the peak-to-peak wavelength, relative to the hull's direction, the same as the boat's LWL, and the boat is "caught" between the too peaks unless it has enough power to climb over the peak. The boat can't push through--the wave will grow and push back as hard as the boat is pushing against it, so the boat has to be able to at least becoming "semi-displacement" (bow up).

I encountered a tug one day that was apparently stuck at hull speed but was applying much more power than needed to be there. You could see that the bow wave had simply grown almost big enough to wash over his deck, and was extremely vertical. A few hundred yards away, Passage went airborne off the first peak, did about a 4' free-fall, and crashed into the second peak, with water going over our bow and cabintop. Fortunately when I saw what was coming, I had my passenger close down the forward hatch which we had left open on that windless day. There were probably some grins on the tug...

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Charlie Vick
Captain

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USA
423 Posts

Response Posted - 04/24/2006 : 20:22:41

Hit 8.4 according to gps down wind, wing on wing, (not on purpose!) by myself in 35-40kts of wind.
Scared me to death. I kept wondering how I was going to come about and get the sails down without flipping her. Had the jib to port so thats the way I turned, back up into the wind. Worked out great but I don't ever want to be in that situation again.
To go go ten k with sails up and on the iron genny I think you would need a Mac with a 50 horse motor and, we know you don't want that.

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