Recent Evolution of the Modern Beach Catamaran Hull

[@maxdurbin3033]

This is the perfect outline for someone unfamiliar with the subject. It's easy to flood people with details before they grasp the basics. Especially with history, thanks.

[@markpalmquist]

This is about comparing the evolving hull shapes since the 1960's, it is not about an overall comprehensive history. And yes it is a guess because the people who design modern catamarans do not publish why they choose the shapes they choose. I am trying to prod someone with more expertise on the subject to write a book about modern catamaran design. No one has written a book in the last 30 or so years.

[@nuorigin]

Excellent explanation. I just watched another video where an engineer try to explain it and never mentioned the other aspects of it. They actually only talked about the lighter-weight and wind resistance from less material being at the front. This makes much more sense. Thank you

[@markpalmquist]

Thanks. I agree, sometimes engineers don't explain things in a way that is easy to understand. My background is 3 years of engineering and 3 years of product design, 2 very different views of the world.

[@MilesCobbett]

Mention the cross sections of each hull and how the Asymetrical hull design of early 14 and 16 foot Hobid Cats eliminated the need for center boards

[@markpalmquist]

I've talked to a lot of naval architects regarding the effectiveness of the asymmetric hulls. The majority think it did not function as intended. Any deep v hull will resist leeway. We had a G-Cat 16 with even deeper v hulls and we usually beat the Hobbie 16 in races.

[@kauaislash5]

There’s another reason why so much rocker may have made it into the first generation HobieCats -Surfing. Surfboards use rocker to keep the board from stuffing down the curve of the face of a wave and to pop over swell during paddle out. Also makes turning easier just like the adoption of the belly volume in the Nacara hulls. If you consider the time period and popularity of Beach Cats with surfers, and the background of those who pioneered and helped “shape” the movement, it’s not surprising that the banana shape was adopted and applied to the early HobieCats. What’s interesting now in addition to the belly volume is how designers are also incorporating cross sectional volume so the more a performance boat is powered up, a greater ratio of volume is submerged with less freeboard loss.

[@markpalmquist]

I agree. Hobie was inspired by Manu Kai, a large catamaran that launched directly off the beach in Hawaii, and also the Malibu outrigger canoe which had good rocker. Both of which predated the Hobie 14. I agree, the hump just behind midship helps turning on the newer cats.

[@waterworldtrimaran544]

Nice explanation. Thankyou.

[@eduardodaquiljr9637]

Do you have 3D model?

[@markpalmquist]

Yes

[@jojojo9240]

why the reverse bow though

[@markpalmquist]

Reverse bow does 2 things, it increases the waterline length and prevents excessive pitching or hobby horsing. The sail rig is more efficient if it is not thrown forward and back by wave action.

[@jojojo9240]

@@markpalmquist interesting, I think you can also increase the waterline length by - well - increasing the waterline length so I don't like that argument by itself for the shape of the bow the anti-pitch effect is nice and increases with speed, which seems to me increases danger of "face-plant" but seems to be okay in practice I noticed the bow probably helps more easily shedding water, is this effect significant? Not bow-related but I think the wedge bow is quite interesting as it is quite short but does not help with lift / heeling. The stern goes upwards after the belly though, which should suck the water up and generate a heeling moment with incresed speed. The resulting pitch of the hull leads to lift to start planing or just decrease the wetted surface. The stern is still quite short, as you can just cut it off without much penalty to hydrodynamic drag.

[@markwalker7813]

Ummm....the Hobie was categorically NOT the first catamaran hull shape. This was the traditional Polynesian double canoe, but possibly even earlier versions form elswewhere in Australasia. Do your homework. I found articel online about Double-outrigger canoes in the Pacific. But even if we are talking 'modern' catamarans, and ignore the dead end that was Araryllis in mid-19th C NY, there were small cats being buiolt oin the Fifties that had more of the Tornado style hull but with single or double chined amas. Hobie Alter did a lot for *popularising* off the beach cats, but he was a long way short of being the first. His 'banana' hulls were actually a backward step, because they eschewed foils that were already known to be essential. His idea of the aasymetric hull, copied by Prindle, was not a great success in terms of getting cats to point well. Early Hobies were successful despite themselves, larely due to Alter's marketing skills and chutzpah!

[@markpalmquist]

The video was mostly about comparing the 3 different shapes. I should have eliminated the word history from the title and you are right Hobie was not the first. But it is interesting to compare the deep V banana shape to the tornado and the newer Nacras. I did not go into the asymmetry of the Hobies because there are still 2 camps, those that say it works and those who say it does not work. I tend to think it works somewhat. The reason it works somewhat is that the rudder on the leeward hull directs the water flowing off the trailing edge of the leeward float just as much as the float itself. So if the idea is to turn the water downwind to create an equal and opposite lift upwind then the rudder could end up eliminating the benefit of the asymmetric hulls. That is why it is better to have the deflection at the mid point of the hull using a high aspect ratio foil. But the Hobies are still fast as hell. I do believe the Hobie hull creates some upward lift when it is heeled and going fast but not as much as a lifting foil would.

[@Aaron.deRuiter]

Mate, do more research before dishing up these videos on KZbin.

[@markpalmquist]

Maybe I should have changed the title to the following “Comparing the 2 dominant cat hull forms from the beach cat explosion of the 70’s and 80’s to today’s forms” but that is too long and cumbersome of a title.

[@markpalmquist]

@Mark Archer on a 21’ catamaran 1” won’t make a noticeable difference. If it was a foot longer you would notice more speed the longer hull on the Lee. You should not worry about it.

[@jacksbackable]

He’s started a conversation, I didn’t hear say anything about being an expert!

[@markpalmquist]

@@jacksbackable Who are the experts? They work for high profile design firms and don't share their secrets. I am not an expert but I am a multihull boat designer. All the books on catamaran design are 25 years old, so I am speculating. Hopefully a new crop of multihull designers will publish a book soon so that I don't have to speculate anymore.

[@jacksbackable]

@@markpalmquist I’m not sure there’s experts, some are more experienced than others, all are going to have failures and have to move forward. How is Success, going to be gauged, and by whom? We all have personal preferences, needs and expectations.