Converting from sloop to cat-ketch

[QCHOTMIX]

Hello all,

I've been lurking around the forum for some time now but have never posted so here goes.

I was given a very neglected Sailstar 17 hull. It's basically the same as an O'day daysailer. I like the hull but would like to convert it from a sloop rig to a cat-ketch like the cs17. What aspects of this conversion would be considered "must do"? All suggestions would be greatly appreciated.

Johnny Turner

[PAR]

Balance the proposed sail plan over the existing CLP. If I have the correct boat, it's a 1950's era centerboard craft and you'll have some latitude in rig placement, but only within a small window, fore and aft, which is typical of most centerboard designs. Next is the total area and distribution of this area on the masts. Now on paper you have an idea of where and how much, the how to part will get interesting.

Structural considerations will include transferring the loaded rig (sails in use) energy to the hull, without breaking anything. You'll likely need a bulkhead or two, maybe a couple of thwarts well tabbed in, but the hull will want to twist, buckle and distort under these loads. The mast step/partner arrangements will need to be pretty stout, as well as engineered to spread the rig load over as wide an area as you can get.

A few short paragraphs can't begin to tell you the issues and difficulties awaiting the novice, but a well versed sailor, with a good understanding of the principles can hack their way through eventually. Getting real nice balance will likely take some help or adjustable mast steps.

[QCHOTMIX]

Par,

Thanks for the reply.

I think you have the right boat in mind. I'm not sure about the boat being built in the 50's however they were built through the 60's into the early 70's. It is a fiberglass hull almost identical to the Oday Daysailor. It is 17' in length with a 6' beam and with a retractable centerboard.

As you have suggeted, I have planned on installing a couple of bulkheads, new seating, decking etc..

Placement of the masts is my biggest concern. Obviously I would like to use the existing centerboard and trunk without modifing them however I'm not sure that I can and achieve balance.

I've looked at rig placement on a couple of other 17' boat plans. It appears that the Main sail placement is the same within an inch, however the mizzen varies considerably. Both sets of plans use the same sail area

Any books, video, internet sites that might shed some light concerning this aspect?

Thanks

[PAR]

I can tell you the SailStar 17 is not as similar to the ODay as it would appear. There are many boats in this displacement range, in fact, it is one of the most popular "class" of sailboat around. It's only natural many boats will have similar sail area, LWL, beam/length ratios, etc. as they all are 15' to 16' LWL craft, subject to the same physical laws. The shape and dynamics of yacht design dictate one can go only so far, before you've scurried well out onto the preverbal design limb and are risking a fall (failure or worse) from the skinny branches holding up your concepts. This is also the very reason most boats have similar shapes, rigs, layout, etc. It's difficult to fool with things that work, particularly on a whim that it might catch on, become a fad or develop a following.

More importantly, to accurately make rig changes you suggest, a hull and sail plan profile is necessary, as well as the vital information. You need this to make the calculations and to get reasonably close balance. Without a lot of time and money, it's very difficult to nail down the balance on paper. I've gotten to a point where I can look at a sail plan and guess within a couple of percent where the CE will be, but that's what experience does for you. I'll still do the geometry, but my guess is often so close it makes me wonder why I troubled.

You will need to have a pro look over your ideas, so you can get a reasonable result from your efforts. Succumbing to the less then scientific method of installing an adjustable mast step, can save a lot of bother and isn't as uncommon as you might think.

[JeffM]

Johnny, how about posting some photos of your hull (maybe some from above as well as profiles) so the would-be naval architects among us can get a better appreciation of what you're up against?

[QCHOTMIX]

To all,

Time permitting, I'll try to get some pictures of the boat up this week.

I really appreciate your comments and help with this project. I could have just restored it back to the original sloop configuration but that would have been too easy!

The adjustable mast step sounds interesting. Any links to examples that I can look at?

Thanks again