Design and build plywood fast cruiser with lifting keel, 36 feet

One more to the keel. I´m inclined to make an unsinkable hull. Because of wide hull that is not so easy to get back after capsize amd overall safety feeling. Therefore the long lighter keel makes sense for me.

 

Lifting keel: check out Jim Antrim- he did the Ultimate 20 (which we had- great keel lifting system), 24, 27, & 34- all have lifting keels. Check with him to come up with a boat design? These boats are all high performance machines in the Santa Cruz / California sense- check out the design numbers- I’ll post a link in a bit.

here- Antrim Associates Naval Architects https://www.antrimdesign.com/

 

You either design to some standard using their formulas and loads, or you define your load cases arbitrarily and do the engineering from scratch. For a keel you take a given speed then use max displacement to find the force, then you consider the keel a cantilever beam and see what structure you need, both in the foil and in the support.
DNVGL yacht rules are an example of such standards, ISO, etc.

I only brought up the czech fir because you said you chose ply for ecological and health reasons. Ply makes good boats and is a legitimate choice, but let's not greenwash. Please wear full PPE when working with epoxy and don't let kids near it, it's toxic and can damage a person for life.

Dix has a plywood design in your range, the Didi 38. https://dixdesign.com/38didi.htm There are some blogs detailing several builds, including the fabricated steel keels. He designs with a radius chine, but apart from that detail it's a typical plywood on stringers build with structural furniture and what you see can be applied to a chined hull.
I presume you will design digitally so everything can be CNC cut (or cut by hand following printed patterns) and assembled quickly, so take a look at builds using precut kits.
The slow phase begins with filleting, taping and cleaning all the joints, the total build time isn't significantly faster then other wood methods like strip planking or cold molding, the individual worker makes a bigger difference. For the modern rounded bottom/single chine aft/no flare flat topsides look that gives maximum volume for a certain size you can investigate a combination of stripped bottom with plywood topsides.

 

I think buying some already constructed keel plans to avoid corosion, unvanted movements and other problems is the way to go. I will contact designer/s after I will be sure about the sollution. The Patrick Balta keel is interesting to me because the keel gets above the boom(at least on the drawing) . If I will build such a system I want to use it to the maximum. So thanks for the links. If there are more lifting keel sources, please let me know. And thanks for explanation.

The slow fase of building such as "filleting, taping and cleaning all the joints" will be done by one of my employee, not me

Now I would like to turn back the discussion to the hull. Maybe another silly question. Is it common or possible to design the cruising hull to sail in certain (most prevailing) angle? I mean there will be different requirements for racing and for cruising boats.

Most likely I will just copy some of the already existing design. I just want to know, what is possible and what not.

 

Yes I will design everything on PC and then let cut most of the parts on CNC. It is my hobby. I can do it on evenings instead of watching TV/Youtube.

The classic "wood sringer construction" doesn´t resonate with me. First I think it is more time consuming but more important I think both sides laminated plywood joint is much stronger than gluing plywood to the wood stringer. That is the reason I choosed "big stich&glue" method. The other reason is after I will put the hull careffully together, the boring job of taping etc. will do some of my carefull employee.

The only bigger boats built this way I kow are RM yachts. If there are any other yachts or plans, please let me know. Thanks

 

Wide stern boats with flat underbodies are already biased towards reaching and downwind work. Cruisers should pay attention to beeing stable under autopilot under this conditions. You can go further down this path with fuller bows (direction scow). You pay with more pounding or increased heel upwind.

It's more efficient weightwise, gives a lighter boat with more design freedom for cabinetry. The eggcrate stiffening method as used by RM is more efficient to build using 3-axis CNC's, but since most cabinetry needs to be structural it limits interior design.

 

Take the keel from this....
Pasja 1100 - Janusz Maderski JACHTY - BUDOWA, KONSTRUKCJE

and put it on this....
Dziesiątka - Janusz Maderski JACHTY - BUDOWA, KONSTRUKCJE

Ask Januz about it first though.

 

It’s kind of old an old school approach to a keel, but if you’re going for a lighter keel, it might meet a lot of your requirements: in a general way, a Finn dinghy or 12 Metre Sharpie type metal centerboard. Probably not quite as good upwind? (Depends what tacking angles you want) Anyway, advantages would be kick up, metal (harder to ding), always fills the hull slot, simpler to build. If you could shape it to a good hydro shape, it would be better than the current flat plates. Use water ballast like Swallow Boats does for stability. There are some catamarans that use a similar shape centerboard? A couple of racing sharpie classes use them, I think. I’ll look them up. From my Finn days, a nice feel when things get sporty.
https://www.reddit.com/r/sailing/comments/1542a5e/thoughts_on_water_ballast/

Classic Design with Modern Performance Trailer Sailers - Swallow Yachts https://swallowyachts.com/

here's some CFD on Finn underwater stuff

Finn Class https://www.finnclass.org/index.php?option=com_content&view=article&id=204%3Aa-look-at-the-finn-under-the-water&Itemid=220&catid=30%3Afeatures

 

That Hunt 310, is thought provoking...


But i have always liked ULDB types.

 

Hi Petr, with you're wanting 3 cabins, and a wide hull, and not a racing boat with fine lines, you might consider something more barge shaped, with lee boards, which will free up space for cabins and access to them. Raising and lowering lee boards can be very simple, or complicated if you like; a flat -ish bottom will get you access to shallow moorings, and possibly beaching without leaning over tilted, and no reason why you can't stitch and glue one up. It doesn't have to be completely barge shaped, and you can have plenty of headroom, and a wide flat floor inside, instead of shuffling between a centrecase and your furniture. Just another thought to broaden your possibilities. There is a sea going beauty called 'Juno' which I would like to make a much smaller version of, in my pipe dreams.
How big do you want your 3 cabins, and what waters will you mostly be sailing / motoring in ? What are the worst storm conditions found on those waters. Will you be accommodating family on your boating trips, needing comfort and safety, maybe a galley, head, and shower, and various water tanks, or adventuring with experienced crew ? Will you take loads of gear, meaning bulk and weight, or mostly traveling light ?

 

Antrim scow for ex windsurfer sail designer

 

Right now an RM yacht with long lifting keel and three cabins is closest to my idea. I like the curve of cabin roof of JPK 45.
One shower and head is enough for me.
I will charter some boats to get more impression and experience. To really know what I want.

Scow bow boat will be too rough in high seas I think.

 

Let´s dream little bit

Boat I would really want to have and enjoy is some classic wooden yacht. The feeling of wood. Wooden details. That is of course immpossible because to get desired internal space one would need 70+ feet yacht. But there are Britol Channel Cutters. They offer a lot of internal space and look nice. I would like to have combination of classic lines and modern buildings methods and interior layout.

Something like Berckmeyer designs, for example BM37 http://www.berckemeyer-yacht.de/yachts/New%20Yachts/BM37_bristol.html But I lack the feeling of wooden yacht. It is just modern boat with some design curves of old Bristol Channel Cutters. The hull shape seems to me too modern/flat bottomed and large freeboard for such a boat.

On the other side there is much smaller Koalen 26 Koalen 26 https://www.vivierboats.com/albumsen/Cruising%20sailboats/koalen26/index.html There is a feeling of wooden boat (even it is more plywood boat). Wooden mast and boom, wooden details, old rig etc.

So I think there is an sollution. To make something between, not so much performance oriented but more „traditional look“ oriented. But I still want to have good sailing perfonmance. That means instead of wooden mast and boom I will make carbon mast and boom with wooden look. Long keel. Overall lighter construction with ballast lower etc.

I would make the boat little bit longer - 12 meters.

The hulll could be (flat) V shaped plywood bottom with strip planked sides. Plywood bulkheads and laminated ribs. For such a completely new design I will make a model first.

So what is your opinion to that? Do you know any other designers or designs with combination of classic and modern approach? Or modern yacht with nice wooden details?

 

Dudly Dix does a retro 29. Maybe you can talk him into doing a larger one.
Didi 29 Retro radius chine plywood boat plans (dixdesign.com)

https://dixdesign.com/did29 mierke2.png

 

I want to chime in with "circumnavigation-36feet length-fast/planing":
this will be VERY difficult to realize: even if you are a very frugal person & put up without all the "luxuries" considered indispensable on a cruising boat these days, the very light weight needed will be a challenge to achieve. Basically you will scale down a class 40 (which will only be fast of loaded lightly!) to 36', so the payload-in theory-will also be only 73% of the , already low, payload of the class 40.-If you want to achieve similar performances. Can be done, but will mean 1 T-shirt, 1 short, 5 rolls of toilet paper, 1 bicycle-multitool for toolbox,...this sort of "list".
36' & circumnavigation: imho you will have to go with "moderate cruiser/racer-type" & forget the "planing". You will still have to prioritize your "packing list" heavily. (fwiw: my "credentials" are 1 rtw on 34' Wharram cat, 2 rtw on 37' Pouvreau 11.30 & 1 France-Tahiti on Elan 410)