questions and ideas for rob denney

Rob. From the very beginning of your online presence it was obvious your proa fixation was not based on profit motive but on deeply held conviction. If profit was the main motive you would have gravitated eventually to cats and tris. Though I have enjoyed your thinking, I never considered a harryproa or any proa type would suit my use in my area - just too much boat traffic unfamiliar with proa shunting. But I have often thought your build methods could be applied to cats and tris to reduce build time, cost, and weight. If you were to do this, what changes to under water hull shape along with foils might you try to make one way multis more efficient?

 

Glad you enjoy my thinking. I appreciate the opportunity to share it. The difference in behaviour of a Harryproa and a conventional boat would not be noticed by most onlookers. Shunting a schooner is not the big deal it is for proas with crab claw sails or jibs. One of the advantages of shunting is that, unlike tacking and especially gybing, it can be stopped or reversed at any stage. If there is a boat passing too close, it is no problem to wait.

I am regularly asked to discuss/design cats. The cost of, and stress/hard work involved in sailing stayed rigs means my versions have unstayed masts, no headsails. They don't have daggerboards, fixed rudders or exposed props, for reasons which are obvious to anyone who has thought about sailing at speed. The increased righting moment available and ease of use in harsh conditions usually means they are shunters. The costs and inefficiencies of having 2 hulls optimised for use half the time means they usually end up as proas.

The Harryproa build techniques (Intelligent Infusion) were developed around Harryproa hull shapes. Simple, flat shapes that are laid up dry on the table and infused to provide self aligning panels requiring minimal wet laminating, filling and fairing.
To build the compound curves or double chines that most cats use under water requires complex moulds, framing or jigs before you start, time consuming laying up of the core (foam or ply), sticky, hazardous hand laminating/tabbing and even more hazardous fairing of the end result.
Infusing a cat hull would reduce some of this, but as a quality mould is required for compound curve infusion, the labour, stickiness and hazard are spent on the plug and the mould.

To answer your question (at last!). If speed of building is deemed more important than a possible small percentage of performance from compound hulls, single chine hulls are worth a look. They need to be narrow (or deep) at the bows to avoid slamming and will have more wetted surface which will reduce light air performance if everything else is equal. Which it isn't. A flat bottom hull does not need floors, the installation of which is the second shittiest job building a boat (fairing is the first), or the added topsides required to gain headroom. Both of these increase the weight of the hull, offsetting the extra wetted surface of the single chine hull shape. If length is not restricted, I'd also look at double ended, which is the best hull shape for variable loads, such as are seen by cats either from overloading or depressing the lee hull while sailing hard.

Foils for lifting are expensive, need to be kept shiny and must kick up in a collision. Not worth the effort for a cruiser.
Foils for leeway resistance and steering have a huge amount of room for safety improvements, simplification and weight loss, watch this space.