A beamy 23 ft sailboat idea

You could maintain the same basic shape / concept, but just make it a bit larger if 21' is too small?

Rather than your bilge keels with a central daggerboard, you could consider having twin lifting keels, like the Red Fox 200?
https://sailboatdata.com/sailboat/red-fox-200

Here is one that was for sale - lots of photos are still online :
Red Fox Red Fox 200E For Sale, 6.17m, 1995 https://poole.boatshed.com/red_fox_red_fox_200e-boat-232215.html

 

Seems like you are more interested in bragging rights than sailing. Have you been at sea for any length of time? Many people end up hating boats after their first cruise. The design is geared towards being different and getting recognition instead of fulfilling a purpose for cruising. "Far flung places" is a romantic idea, but a boat that will be ideal for shallow tropical areas would totally suck in high latitude freezing conditions.

 

It's strange to reframe pride in actually doing things with your own two hands and brain as "bragging rights"... but I suppose that's the type of world we live in now. Why do anything yourself when you can buy it off a shelf? And you can buy anything off a shelf, so just sit back and consume.

The design is towards sailing requirements. As I've said, I'm in Kansas, so if I build a boat it would need to be able to go down the Missouri and Mississippi rivers. Not the ideal situation for a large deep keeled displacement boat.

 

I did this preliminary design here attached to show some orders of magnitude that could be helpful for your project.
I started with :
- a beam limited at 3,6m for the Lhull of 7,92 m (26'),
- a DLR (Displacement Length Ratio) = 200 for the light weight fully equiped boat
- a maxi load of ~ 800 kg (>>> DLR 230 at max load)
- a lifting keel , drafts 0,6 m / 1,60 m
- a ballast limited to 630 kg, with a lead bulb bolted at the tip of a keel wing
- twin lifting rudders, vertical (more easy to connect at the rear transom)
- a headroom of ~ 1,85 m in the cabin (under the roof)
RM and waterlines at 20° and 30° heel angles are given
AVS (Angle of Vanishing Stability) with the maxi load 800 kg is ~ 111° (at this stage of the project)
Speed ~ 5 Knots upwind and ~ 6 knots downwind with 12 Knots of wind

By hoping these orders of magnitude for an "average" beamy design can be helpful for your project

 

I have imagined designing for the AiT challenge and wide would be how I would go too. However, the idea would be to create a flat bottomed planing hull rather than a pokey short displacement boat.

I think your concept could work, but I suggest looking at getting a little more simple with your bottom design. There are two basic resistance forces to consider. One is surface area, your design has more surface area than it needs to. The other one is how much water does your boat have to displace how far and how fast? A shallow flat bottomed boat doesn't have to move its displacement as far as quickly as a round bottomed hull of equal displacement. A narrow hull pushes the water to the side, while a wide hull pushes the water underneath.

 

If this boat is supposed to carry a big load, I don't think a Mini Transat is a good model. OTOH, a traditionally shaped Cape Cod catboat would probably work a lot better than many choices. A heavy load means planing is unlikely, of course.
Here is a "Martha's Vineyard" catboat, which is similar to a Cape Cod catboat, but a little less extreme. Notice that the deadwood doesn't hang down below the hull, as it does on some of the Cape Cod type. For them, it might make sense to cut back on the deadwood a bit and maybe make part of the rudder so it can swing up.
https://i0.wp.com/churbuck.com/wp-content/uploads/2021/09/MVCATCHAPELLE.jpg?resize=768,994&ssl=1
BRECK MARSHALL, Cape Cod Catboat | Mystic Seaport Ships Plans https://store.mysticseaport.org/ships-plans/breck-marshall.html
I doubt if either one of these would go to windward very well with the centerboard up.
There are probably some other traditional types that would serve your purposes well, maybe even some that are local. On a river, I should think pounding wouldn't be much of a problem except momentarily when a big barge or an idiot with a monstrous motorboat goes by. So you might look at scows and garveys.

A scow schooner, probably bigger than you need:
e7 https://www.flickr.com/photos/hallman/478537881/in/album-72157613767421231/ (Suggest you look at some of the other images Bruce Hallman has on Flickr. Lots of 3D renderings of boats, mostly Bolger designs.
Phil Bolger and Jim Michalak both have scow designs, as well a bunch of others meant for shallow draft.
http://www.coots.org/Misc/Michalak/Files/Boxtop/BoxTop.pdf
https://www.duckworksmagazine.com/r/plansindex/bolger/Scow Schooner-s.jpg (only pic of this design I found)

If you're not easily embarrassed, a SuperBrick might accomplish your mission:
Bolger’s Super Brick Sailing Shantyboat https://houseboatshantyboatbuilders.wordpress.com/2009/12/17/bolgers-super-brick-sailing-shantyboat/

If you're not a sailor already, I suggest you start with something really crude to see if you like building and sailing. For instance, a PD Racer or a Bolger Brick
.https://www.pdracer.com/articles/pictures/672-1.jpg (no, the wheels aren't part of the design)
https://sites.google.com/site/molepages/brickplans.jpg (Sails well with 4 adults. For solo use, you might want to put some extra weight on board, so it doesn't pitch forward and back too much.)
You could build something called Grout, and a second Brick, and sail around with maybe 1,800 lbs of weight without much trouble.
https://www.pdracer.com/hull-config/brick-grout/grout3.jpg

In any case, you may find it helpful to review some of Howard Chepelle's books to give you a better idea of what's gone before.

BTW, on the light displacement end of things, Mini Transats, as I recall, are restricted to 6.5 meter length and 3 meters of beam, giving the ones that take full advantage of the rules a length to beam ratio of less than 2.2/1.

There ARE scows that are pretty close to catamarans, but I think most scow racing classes prohibit any hulls that are shallower in the middle than further out away from the center. This Moth scow has a bit of a "tunnelt", but I think it's already obsolete, as they all seem to be going with hydrofoils.
https://www.sail-world.com/photos/cvdra/yysw239946.jpg

 

John Smithson.
I'm with you. Far too many espousing the line "Look at the way boats have been built the last 200 years, that's the only way to go." Yes, 200 years but in the last twenty or thirty the world of boat design has been turned upside down. Look at the IMOCA 60 hulls and they are more like dinghies from the sixties. Wide, nearly flat. They sail on the wind by heeling so the chine actually becomes the hull in the water and the heel lowers the wetted area. In the sixties we sailed our dinghies in light airs sitting on the lee side to create heel and do the same thing.
Build it light and beamy. Hang two kick up rudders off the transom with a lifting keel. If you want to be as innovative as I would like to be, install a lightweight motor at the stern with a stern drive or jet drive.

I love traditional boats but just for their beauty. Mostly under 35 feet their accommodation is awful, their cockpits are pitiful and they haven't improved their speed in the last hundred years because they are so wedded to displacement and hull speed. It's time we had a new paradigm for boat design.

 

You can build it light and beamy, but it won't be light in use if it has to carry a bunch of cargo, as per the OP's wishes. All the modern design technology in the world, won't make a heavy displacement boat go all that much faster without applications of unobtainium and gobs of power, or maybe deeper draft. It might go pretty fast if you made it a submarine with a modern shape*.... Or maybe if you made it twice as wide as it is long and used 3 skinny hulls, or some other nutty scheme.

I don't know what you think is pitiful about cockpits in, say, a Cape Cod Cat. If I'm not mistaken, the following image is of a 19 foot catboat. Does that cockpit look small to you?
https://areyspondboatyard.com/wp-content/uploads/2019/04/Fields_APBY114-600x600.jpg

If a lot of money was available to spend, I could see using hi tech materials in the hull so that more ballast could be carried, and more cargo too. Similarly, with the application of gobs of dough, expensive sails, fancy hardware, etc., it would probably be possible to make a rig that was a little more efficient.

A lot of what's seen as new tech isn't all THAT different from some of the old racing tech, and the old designs would have been closer if they'd had the same materials to work with.

For an example, look at, say, the E-scow. Does that look like an old design to you? It's been around for 98 years.
https://bloximages.newyork1.vip.tow...7d5f4a/57bb5428b0984.image.jpg?resize=800,500
The idea for the hull shape is even older. Check out this design from 1897. It should remind you of something:
https://ids.si.edu/ids/deliveryService?id=NMAH-MAH-45451A

A lot of the latest and greatest isn't necessarily the latest. If you don't know about it, that doesn't mean it never happened. Also, sometimes what we think is the latest and greatest is really the product of some racing rule. Can you say "IOR"? Building to a racing rule was, of course, nothing new. Check out this design, launched in 1903, by Nathaniel Herreshoff for a rule that restricted the length of the waterline to 90 feet:
http://www.america-scoop.com/documents/02/02994.jpg
The overall length of the boat was 201 feet! (I don't know the length on deck, I think maybe 140 or 150 feet.) The waterline length increased greatly as soon as the boat heeled. The rules were changed very quickly afterwards to prevent such extreme boats.

*The older subs would have had "modern" shapes if they hadn't had to spend so much time at the surface, recharging their batteries with diesel generators.

 

Your example of a Cape Cod cat boat is essentially a day sailor. I see very recent boats 50 or 60 ft with cockpits just 6 or 7 feet wide. No wonder cats are so popular. Sailed on a 45ft cat recently. The cockpit had room for real dining for seven or eight not climbing over each other and still had more floor space left over than those 60 footers had in their cockpit. Really good space doesn't turn up in a lot of (maybe not all) boats till you get to about 80 or 100 ft.

Sadly you are right about "Built to rule" boats. Sad but just a fact of life. Even the IMOCAs are built to rules, just not quite so distorting, (Or maybe they are and we'll see something else more radical still in the furture.)

Your scow picture is interesting. If you look they have a scow bow (so called, I will explain,) but they are not beamy. Traditionally scows were workboats of very broad beam. They had scow bows because it was cheap and easier to build and no one cared how fast they went. I first came across them in a reference to "The garbage scow," described as wide beamed, square bowed. Today the term seems to be applied to anything like the rater you showed because it is not a pointy thing!

It is easy to discount ideas if you choose exceptions or boats build for a particular narrow condition, the raters built for rivers or lakes for instance.

If I was the OP I'd build it extra beamy as a substitute for carrying loads of ballast and that would also keep it shallow as possible. Lifting board (weighted, maybe hydraulic or purchase) or some version of lifting leeboards and kick up rudders. Clearly initial stability is good and I wouldn't carry sail till I was lee rail under. All boats have their characteristics and you have to sail them accordingly

 

Incidentally, the OP did not specify cargo carrying, he mentioned it in a later post as he was "interested" in traditional, possibly "work", boats for their design (rather than because he was interested in carrying cargo. (If I am putting words in his mouth I apologise.))

 

In post 21: I'm looking for a boat that has a very shallow draft (capable of going down a river), while also having a large carrying capacity and decent living area for a single hander.
Emphasis mine. I think that, unless that carrying capacity is for styrofoam peanuts, we're talking about a bunch of weight. I suppose carrying capacity is different, at least for the boat owner, than cargo. However, physics doesn't care.
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I didn't realize catboats even got up to 45 feet. The sail and boom must be awesome, and "interesting" to handle. What's a jibe like on a catboat that large?

 

The Nonsuch catboats were built up to 40', but I cannot find any info online re the 40' version - here is a link to their 36' catboat :
1986 Nonsuch 36, Hamilton Ontario - boats.com https://www.boats.com/sailing-boats/1986-nonsuch-36-8381534/

 

I guess I was thinking a traditional cat. I imagine the Nonesuch people went to some trouble to make the sails easier to handle, and of course that boom is higher up and not as long.

 

That width is about the maximum for safety in rough weather. The trend to open interior spaces and huge cockpits are great for people that spend their time at the marina though.

 

"The trend to open interior spaces and huge cockpits are great for people that spend their time at the marina though."

That Cat I mentioned with the big cockpit has just arrived in Grenada from Australia via Indonesia, Maldives, Seychelles, Cape Town, St Helena.