Catamaran Issues

As designers we advise against three very common practices in the catamaran industry. I invite comment and debate.
Let us look at the three.
Strip. Could anyone look at the shapes and how we built Toria (1965) and lots more, before strip came in, and say that it would be more efficient to use narrow strips instead of full size sheets. The power of advertising provided the motivation to adopt strip as standard. In doing so, the build time escalated. After 2-3 decades, we are beginning to see a trend away from strip. The total inefficiency message is getting across.
Balsa. Toria had a small ply top made in a hurry to get to the race. When modified a few months later, we cut through ply and foam. The foam was bone dry. The ply was soaked. That was when I made the rule to exclude anything that can rot from within the structure. Balsa loves water and loses strength within days, so much more vulnerable than ply. There is nothing to gain and everything to lose in using balsa. However well built, there will always be a question mark over any balsa boat structure and at some time the balsa will get wet and rot. It is sold on the basis of its higher compression and shear strength, but ignoring the very simple fact that PVC foam has met all compression and shear strength requirements on boats for more than 40 years.
The three stay rig. Look at the profile view and measure the angles. Forestay to mast will be about 18 degrees. The fixed shrouds are at 8 degrees. The big forestay load is supported by the aft shrouds in a reverse lever situation, putting much higher load on the shrouds and much higher compression in the mast. We add runners and the aft support angle goes up to 18-20-22 degrees, with good control, much lower loads on everything and no pre-tensioning. A recent explanation given to me by a sparmaker: The poor support angle ensures that the forestay could not be tight and hence the load in it was restricted and hence less compression on the mast. The load on the shroud in capsize situation becomes the criterion. The spar maker engineers the rig to the designers stay arrangement. This situation, no doubt, comes from the cruising sailor requesting the minimum number of controls, but without being given the knowledge of the compromise involved or the effectiveness and the ease of operation of runners.

Derek.

KSS Workshop in Florida

Recent discussions of boat building methods on a number of forums, have compared KSS with alternatives.
KSS is our own unique method of catamaran building, which is suitable for all builders, particularly DIY and for all catamarans.

A KSS workshop, is a hands-on demonstration over four days. The typical workshop will produce a hull for the catamaran as well as cover many other topics involved in building and sailing.

Although KSS has been around for more than 15 years, it has been considerably refined over that time but there are some misconceptions.

KSS is something that all who might consider building themselves, should know something about - other than the opinion of other designers. Attending a workshop is the ideal way to find out more and then decide if, what and how you might build your project.

The location is close to Pensacola. the dates 11th. - 14th. Sept. Look for more details on the www.kelsall.com website or register your interest with me. This is not a formal class. All go away well satisfied and we also have fun.

Derek.