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A Waters monohull for 2021 ?

Question:  Here’s a question you may prefer to ignore, but with your NA background, what might a Waters monohull of 9m+ look like if you were to design one today ?                                               Kasra-B,  Antalya, Turkey

Reply:   That brought a smile, as yes, its hard not to sometimes drift over that thought as monohulls DO have a few advantages over multihulls.    They are less expensive, self-righting and more compact, so easier to park in a marina.  They just heel too much and can sink ;)

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I will not go too far down this trail as my drafting days are about done and IF I could do more, it would be to detail my W32 Wanderer trimaran that I believe would be a great boat for fast cruising.

But briefly,  here’s an eye towards a 12m monohull for a few minutes. 

I’d apply the same principles that keep my boats dry, with low wave making and low pitching.   This means near vertical sides and waterlines as straight as possible with the ends asymmetrical to avoid synchronous pitching.  In my head, this results in an ‘Arrowhead’ design, so let’s call it that.    Arrowhead 40 would have a fine bow with nearly straight waterlines back to the transom, that would be close to the widest part of the boat!       We learn from motorboats at speed, that the most efficient planing surface is a wide one, about 50% of its length, which is virtually impossible to achieve on a large sailboat.  Contrarily, when in displacement mode we want the tail-end to be as fine as possible.   But, as for a modern racing dinghy,  we can achieve both these things by heeling when going upwind and staying flat when downwind, so pumpable water ballast would make sense to help achieve that.    So I’d be looking at a general form like this quick sketch.     I’d go for a deep bow, possibly with an underwater bulb up forward that would both lower drag and further reduce pitching

Of course, I can hear the ‘OMG., what ugly sections!’ .. I had that with the W17 in early days, but I’ve argued for a long time that we need to look at a hull how the water sees it.    It needs to go forward as easily as possible, but NOT sideways.  Hard straight chines can do that most effectively.    We also need the displacement as low as possible to keep the waterline as fine as possible …. box sections do that also.      With slightly higher wetted surface, I would expect her to be a bit slower than a more conventional rounded shape in winds under say 7kts but faster in winds of 10kts and above.  Large foresails in her cutter rig would help compensate in the lower winds.

Way back in the 1950’s when I was a teenager, I used to see a black flat-sided boat called Black Soo moored out on the south coast of the UK.  She looked fast and sleek. Designed to show off the strength of the then-new ‘marine plywood’, she had a boxy hull and vertical sides also and was designed by the famous Van de Stadt .. and although uncomfortable, she went like’ the bats of hell’ and proved that in a rough Fastnet Race.  In fact, I know someone who sailed on the boat.

 Whatever can be done to reduce pitching is worth it as it’s a speed killer… not only vastly modifying hull form with every wave, but also the effect it has from waving the mast and sails rapidly through the air at constantly changing angles, resulting in less drive with more resistance … the worst of both worlds.    One great advantage of length is less pitching but it’s much harder to control with boats under 10m. 

The hollowing of the bow on the centerline is a nod to my recent W-Scow design and an effort to soften the ride of the box shape, as the veed bow of Black Soo became flat when heeled and slammed brutally hard.   This version offers a kinder vee’d-shape entry when heeled .

All very rough and tongue-in-cheek, but hope this gives the reader something new to ponder ;)

mike 2021   

 

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