18" trailerable cruising dinghy based on Haven 12 1/2

Hey,

My name is Daniel. I am looking into a new project for myself.
I have built two wooden/composite sailing dinghies from plans before and am now playing with the idea of designing my own for fun, to learn about the process and with the very faint possibility to end up with a new boat building project some day.

I have a BSc in Physics and a BA in Visual Design - so I really enjoy learning about both the physical as well as the aesthetic aspects of this. I’ve read Principles of Yacht Design, all articles, discussions and videos I could find on the topic for about a year now, so I am well aware that there is a lot to it and I am not expecting that I will be able to come up with anything that’s really worth building. Nevertheless I’m hoping to enjoy the process even if it’s just an exercise in gaining even more appreciation for the work of naval architects.

I have three starting points for the design.

From an aesthetic point of view I’d like to build a slightly larger Haven 12 1/2 - halfway to a 20’ Flatfish basically.

From a practical point of view I’d like to have a boat like a Welsford Pathfinder or a Swallow Bayraider 20. Light, roomy, relatively easy to trailer and launch and the compromise between seaworthiness and speed biased towards safety and comfort maybe 60/40 or 70/30.

I have seen that Chuck Paine has designed an updated version of the Herreshoff 12 1/2 with reduced wetted surface, a fin keel and spade rudder and an unstayed carbon rig.

So I would like to see if something along those lines would be possible with the Haven - slightly larger with perhaps a flat bottom, a centreboard and a water ballast system.

To be built in cedar strip planking and fibreglassed inside and out.

The idea was to start by modelling the hulls of the Pathfinder and the Haven 12 1/2 in Maxsurf and see what the stability and speed predictions are to get a rough idea of where to start. Then to make changes to the Haven (stretch, increase beam, flatten the bottom, reduce ballast keel and add water ballast) change the rudder etc. and see how these changes affect the predictions.

Any thoughts, suggestions, input are very welcome!

Cheers,
D

 

Nice designs. You could "round" the hull sections from Pathfinder if that gets you closer to the boat you desire, they are a well proven cruising dinghy as they are and many like the aesthetics. Cant help with the computer stuff, i still use paper and build models, as I enjoy that process than learning a programme i wont make much use of (or become addicted to), so I would say, do not get too hung up on numbers a computer may spit out, for what is a dayboat. Many a fast "perfect" design is easily ruined performance wise by overweight crew, belongings and badly stowed "stuff" that may make a slippery design on computer, become a draggy dog in the real world. Not to say aiming for a goal is not worthwhile, just be realistic.

 

Thank you for your thoughts skaraborgcraft. Those are very valid points. In my case, the biggest performance handicap is certainly my sailing skills. A racing dinghy would be a complete waste on me. But I would like the boat to be able to make some headway into a decent breeze if I need to. I love a model (made three before my last built went full size) and do like to see my lines on paper. I'm hoping the CAD simulations can shed a bit of light onto how changes play out on the water and give an idea of what to expect.
As I said I definitely don't expect to end up with anything usable, but I hope to learn a bit through my wrong turns on the way.
My current build is in fact a strip planked Pathfinder and I'll certainly sail that for a couple of years to learn about my requirements before I start another built.
This design project is more like another angle to it all to get a better understanding of it.

 

Dan, Welcome to the Forums...

You say "cruising"... do you mean a tent camper like all the boats you mentioned, or do you want a cuddy, say something like a West Wright Potter?

 

Hello jehardiman,

thank you for the welcome!
Yes, I meant a mostly open boat with a short foredeck - probably more a dayboat than a cruiser. I want to add a foldable sprayhood for a bit of shelter and potentially a boom tent (so far we have not done any overnighters) but no permanent cuddy. I'm 6'4" and I don't fold well
The Potter looks cute though!

 

You already have a sound basis then. Sure, I will agree that minor adjustments made in simulations on a PC are a very fast way to see what may be beneficial, as long as you know what to adjust and why.
I only ever used a DOS based programme "plyboats", it gave all the basic numbers to be able to proceed with confidence. Building weight is probably the biggest variable as a "known", so i have always added a touch more displacement at designed waterline.

 

20 Flatfish

Wow

 

Yeah ... it's a pretty boat.

But it is too large and heavy. The ideal would be in the middle between that and the Haven (which should be feasible because it's basically a scaled up Haven)
And maybe a more modern approach to the underwater shape, keel and rudder ... I imagine if it's done by someone who knows their stuff (not me) it'd make a nice boat - lol

It's basically a York 18 but as a CB Version ... and not built by French and Webb for idk 120k?

 

"Curlew"

The first thing that comes to mind that could perhaps be considered would be to give it a Delta Wing profile like in "Curlew" and other classics

this hydrodynamic improvement (in the stability of the balance of lateral pressures) i think is not captured by most software unless it is a good CFD.

 

Cutter "Ive Green"

The second thing that comes to mind is to modernize the helm/rudder as Ed Burnett did, may this good boy, magnificent disciple of Thomas Harrison Butler, rest in peace.

 

What we could call the classic Hydrodynamic solution is magnificent;

but if a modern approach is preferred, the question would be how to save the comfort of a classic boat.

 

In my case, on my "1 ton WindSurf board for an old fogey, Thomas H. Butler in memoriam" ...

it has a solution thanks to a gigantic freeboard of more than 1 meter in height

and so i get the classic that I want both from a Hydrodynamic point of view and the comfort of the cockpit.

 

And for the frightening Aerodynamic resistance/Drag of the Hull ... (420 Newtons, 30 knots)

... the power is increased by loading 200 (!) liters of sea water to sail against the wind.

 

Gartside 191. I can almost hate Paul for drawing a boat with lines i cant find any fault in, imo, quite lovely.





Beware....proper small boat prongraphy....Paul Gartside Gaff Yawl For Sale | Wooden Ships Yacht Brokers

 

Oh yeah ... that's a very nice boat. Paul has a few that I've admired before ... I love his "Terror" from an aesthetic point (not sure about practicality) - I have quite a few of his study plans in my research folder
I know he isn't a fan of strip planking - haha but I'm not sure if I'd trust myself to get a traditional lapstrake over frames like this one watertight. And although I love the look, I think I'll need to go for a bit more freeboard.