on the design of ultra slim yachts

Well my idea for a fast passagemaker is something in the way of a cat-- Tornado-class, with assymetric planing hulls and a bridgedeck just high enough to clear most chop-- with a big kite for power and easily switchable daggerboards to maximize lift to windward when needed.


That said, there's a big part of my personality that sits on the forward hatch cover, doing fiddly things with tarred hemp, checking the set of the foresail, poking at my pipe and squinting under a wool cap and generally looking wise.

Everything's a compromise; I'd probably be happy with a Hand motorsailor but thankfully I don't have to limit myself to one vessel.

 

I have a view of a boat that stays in the water rather than on it. Very low buoyancy in the ends so it just passes through waves. Like the outriggers on the fast tris.

The motion would be quite sedate in a long slnder hull compared with flying from wave crest to wave crest in a kite powered cat. And the average speed would not be a lot different I suspect.

Rick W.

 

Length to beam ratio

Rick, I'd be interested in hearing your thinking
on the length to beam ratio( at the waterline) that you're considering.
Dionysis, Have you built a model or smaller test boat?

 

Doug
I am leaning more to solar power and a small wind turbine mounted aft.

I cannot recall the exact numbers but Godzilla optimises a 1 tonne boat around 60ft and 2ft WL beam for 10knots - would be similar to a rowing 8. This is too extreme to accommodate what I want to do. It would need a ballasted keel to have the required stability.

So I am currently trying to get the best compromise between stability, accommodation and required power. My current design is 14.7m long and 1.1m WL beam with a KMT of 850mm. The hull would flare out above the waterline to give me a cabin top wide enough to accept standard 210W solar panels. However this is at an early stage.

This boat would require 2kW to do 10kts. I am yet to work out if it can all be built having the required strength, enough battery to hold 8kts continuously and carry two people in a degree of comfort. It takes 1kW to do 8kts.

I plan to do some serious on-water testing with solar power on one of my small boats before I get into detail. There are many things to work out. For example I really don't want to have tracking panels so I want to see how much the panels give in a range of sunlight through the day.

I am also keen to stick with a monohull as I prefer the motion of a ballasted monohull to a multihull and, despite what many say, I like the idea of a self-righting boat.

Rick W.