Proafile v5.0 | Updated: Jan 04, 2009

Portfolio

Changeup

Posted by on 09/05 at 06:51 PM
The slider is the best pitch in baseball. --Ted Williams

Changeup is a riff on Ray Aldridge's brilliant beach cruising cat, Slider. I hesitated to publish these drawings at first, since they are an obvious take-off on Ray's design, but imitation is the sincerest form of flattery, so I hope Ray takes them in the spirit intended, which is one of respectful admiration.

Slider answers almost every single desire of my beach cruiser fantasy: Twin hulls, shoal draft, simplicity, dock-like stability, ease of launching, usable space, cargo capacity, sailorman rig, and an aesthetic that reaches deeper than the latest multihull fad. The only problem - and this is ONLY a problem for my testosterone/adrenalin driven ego - is that it tops out at 7 knots.

OK, I admit I want it all - a beach cruiser that will outshine the Mona Lisa and outpace the Enterprise. But given my economic and scientific station, breaking warp (knot) 12 would suffice. The only way I can see to break that barrier is to get the whole crew behind the initiative, so when the breeze kicks up, all hands to windward!

Changeup is designed to accommodate both crew in the windward hull, when conditions merit. The idea is that sailing in light air (the predominant condition in my sailing range) will see each of the twin crew within their respective hulls. But if and when the need for speed arises, then both bodies may be accommodated in the windward cockpit, thus providing the potential energy required.

The rig is the sliding gunter w/ curved gaff, a scaled-down version of Manu Kai. Mast height is a manageable 19', and the 190 sq. ft. rig may contain up to three reef points.

The hulls are asymmetrical, and happily do without boards. Leeway resistance is provided by the hard chines, enhanced by chine-runners (see Matt Layden's Paradox and Bernard Kohler's KD860). The asymmetrical hulls position the buoyancy as far outboard as possible, gaining a few more inches of righting moment, and with a beam limited catamaran, every inch counts.

Changeup is 8'-6" wide, which is the only choice for a small boat that expects to be kept on a trailer - and used often. That said, I might be tempted to make a pair of 10' beams to fit when the boat goes for a cruise of a week or more. The extra trouble would be worth it.

Comments

  • Hey… I love it!

    Good looking boat.  I don’t know why you think it will top out at 7 knots, though.  Slider only has 140 sq. ft. of sail, and has hit 8.4 knots, and could probably go quite a bit faster than that in the right conditions.  Changeup ought to be a lot faster, and the gunter main seems an excellent choice.

    You should build it.  We’ll start a movement.

    Ray

    Posted by Ray Aldridge  on  09/11  at  07:36 AM
  • Oops.  I just realized that you were talking about Slider when you mentioned 7 knots.

    Changeup would definitely have 12 knot potential.

    Sorry.

    Ray

    Posted by Ray Aldridge  on  09/11  at  07:39 AM
  • Hi Ray, thanks for the comment. I was reading on your site and got the impression that 7 was about top end for Slider, so thanks for clarifying. Glad you like the rig, I’m a huge fan of the older rigs - they have much to offer small cruising boats, where cost and hassle factor are at least as important as speed to windward.

    Cheers, Michael

    Posted by  on  09/11  at  08:40 AM
  • It’s true, and I’m not sure you have to give up any windward ability, at least with some of the older rigs.  Gunter ought to be just as effective as any modern rig.

    It’s funny, but I came pretty close to putting a bigger rig on Slider, and using a sliding beam arrangement to give Slider 12 feet of beam-- something like Mike Leneman’s L-7.  I finally decided against it, on the basis of weight and complexity, but I think it would have worked okay.

    Ray

    Posted by Ray Aldridge  on  09/11  at  01:38 PM
  • Ray and Michael,

    Nice look!  I’m a big fan of both boats.  Michael, what does the asym. sides gove the boat in your view?  I love the chine runner concept for a boat like this.  One could add a dagger if they weren’t satisfied, but the thought of shallow draft is so appealing.  I’m in the midst of doing something similar on a slightly longer waterline.  Do you think that this craft could be righted like a beachcat?  Would the enclosed volume allow floating high enough to actually bail out the cockpits?  Mine will have self bailing footwells and crew will sit on deck rather than in the hulls.  What is the length of your version?  I’m looking for 20-21’.  Chris Ostlind has been drawing some hulls for me to adapt to a H18 rig and parts.  I really do like the Manu Kai look and Changeup as the “retro” rig and Pacific flavor adds so much to a boat that is not an all out racer.

    Dan

    Posted by  on  09/17  at  04:27 AM
  • Hi Dan, thanks for the comment. The asymmetrical hulls will help a bit to windward, and Choy always claimed they also helped tracking in following seas, and they also place the center of buoyancy a bit further outboard, which creates a bit more righting moment. But honestly, I just like the look of asymmetrical hulls.

    Good question about righting - I doubt it. That is a question that Ray probably has a better handle on than I do. The hull length is 18’. Will your boat have extended side decks or racks? That is the only way I can figure out to have footwells in skinny catamaran hulls.

    Glad you like the rig, I like in for the style, but mainly because the mast is shorter, and so easier to rig.

    Cheers, Michael

    Posted by  on  09/17  at  10:03 AM
  • Love the boat! Your design has nailed it size-simplicity-cost-beauty & function-wise...for me anyway! I built a 20’ cat very much like Oslind’s Fat Cat 21 with a hard deck in Hawaii years ago using asymetrical Piver ama hulls - she performed really well. Only thing I should have added for safety and comfort would have been extended side decks or racks as you mention. Michael, can we talk plans? I don’t need comprehensive step-by-step detail, but would like to build it as conceived dimension-wise. Let me know, thanks - Eric

    Posted by  on  11/15  at  09:27 PM

Post a New Comment

Name:

Email:

URL:

Smileys

Remember my personal information

Notify me of follow-up comments?

Submit the word you see below: