[Webmaster edit: Where Erik writes 'Berry' he means Barry Stellricht'.]
The Ketch looks like a Schooner….
Well, after reading comments, getting a better understanding of the recommended sheeting angles, and continuously struggling with Dmin, I’ve dropped the requirement of having identical main and mizzen sails and the sail plan has “evolved” into a schooner. Aesthetically just fine by me. I have posted two versions along with some of the technical details that Berry’s Excel sheets so easily calculates. A BIG THANKS TO BERRY FOR PUTTING IT TOGETHER. The worksheets are a very easy way to try out different configurations, although some knowledge or willingness to learn Excel is required.
The little sailing we’ve done with the boat has shown it to be underpowered in less than 12 to 15 knots. If the sails were not blown out, she should handle the nominally 790 sq ft in 20 to 25 knots, although it would not be comfortable cruising at that upper range. So there is a need for more sail area and I’ve been shooting for +1000 sq. ft.
I’ve come up with two schooner designs, the major difference being seven or eight panels, and an increase in sail area on the latter from 1000 to 1143 sq ft. I’m guessing if we would do the larger sail plan, we would be sailing with two reefs 50% of the time in the SF Bay. It is also a different sheeting setup and steeper angles. (I should note that we have a 18 hp Sabb diesel with a pitching prop – truly and auxiliary engine).
So, unless there is a lot of encouragement, maybe 7 panels is OK. Some general specifications of the present design are:
Main Batten and Panel Dimensions (ft)
|
|
|
Len
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Luff
|
Leech
|
Boom (12 deg angle)
|
15
|
|
|
Batten 2
|
15
|
4.0
|
4.0
|
Batten 3
|
15
|
4.5
|
4.5
|
Batten 4
|
15
|
5.0
|
5.0
|
Batten 5
|
15
|
5.0
|
5.0
|
Batten 6
|
15
|
5.0
|
5.0
|
Batten 7
|
15
|
0.5
|
7.0
|
Yard
|
15
|
0.5
|
7.0
|
|
|
|
|
Yard Angle
|
|
62.9 deg
|
|
Sling Point (%aft)
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45%
|
|
P/B Ratio
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0.27
|
|
Sail Area
|
453 sq ft
|
|
Mizzen Batten and Panel Dimensions (ft)
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|
|
|
|
|
|
|
Len
|
Luff
|
Leech
|
|
Boom (12 deg angle)
|
17.5
|
|
|
|
Batten 2
|
17.5
|
4.0
|
4.0
|
|
Batten 3
|
17.5
|
4.5
|
4.5
|
|
Batten 4
|
17.5
|
5.0
|
5.0
|
|
Batten 5
|
17.5
|
5.0
|
5.0
|
|
Batten 6
|
17.5
|
5.0
|
5.0
|
|
Batten 7
|
17.5
|
0.5
|
8.1
|
|
Yard
|
17.5
|
0.5
|
8.1
|
|
Yard Angle
|
62.9 deg
|
|
|
Sling Point (%aft)
|
|
45%
|
Aspect Ratio
|
|
2.24
|
P/B Ratio
|
|
0.23
|
Sail Area
|
|
547.0
|
Brian - thanks for all the technical specifications. They will be helpful. Question - looking at the photo of your sail, it appears it has some luff hollow?! If true, do you know the purpose?
Kurt - thanks for checking in and the references. I'll study both those sail plans. As you can see, the lower panels are smaller in order to take advantage of your sheeting setup. And then I do increase to P = 5ft for the upper ones. Is that too large? I was wondering - in PJR for the Fig 4.28 sheeting arrangement, it seems like one can either have the lower sheet at 2P and the upper at 2.5P or the flip. Angles change slightly, but the final length is shorter if the upper is at 2P and the lower at 2.5P. Any thoughts?
Also, how do you stow your sheets while sailing or not in use? Coils?
Annie - thanks for the welcome and the pep talk. :) I am concerned about handling and performance... Where we are presently day sailing, being able to point is important.
And I would love to take the boat on a couple of the more friendly races we have here.
Some more technical questions - Yard loads: I was surprised to read that some people experience "sideways" bending of the yard rather than "vertical bending". Hope that is clear. Without any sheets attached to it, can somebody explain the loading in that direction.
If one is going the route of Aluminum battens - round is easier to obtain, but wouldn't a rectangular profile be more efficient - i.e. similar to the yard above - aren't the forces in the vertical plane larger - such as sheet loads, HHP, THP?
OK, cheers from sunny California.
Erik