Small quay punt lines.

Jeremy, good points. there are some wind and rough days here on Long Island Sound when it would be fun sail. Most of the small day boats are just not meant to be out on days like that. What is needed is a ballasted keel boat that can handle those conditions and not work you to death. This is where I am heading, I hope. I can see that there are may subtle
variation to these boats depending on usage.

 

The itchen ferry boats are fairly chubby to carry a healthy displacement but there are also some "plank on edge" designs that a wonderful to sail in heavy conditions. Years ago I remember a particular 17 ft model in either Woodenboat or Small Boat Journal. Narrow but deep, with a lot of gaff sail and no cabin house but a raised hatch right on the deck. I wish I could remember the boat's name. I recall a figure of #4000 displacement though. A boat that would sail on her ear. Very British.

 

I remember the boat, very deep.

 

Frank,
I have nothing useful to contribute other than encouragement. I love the look of these classic work boats.

 

That looks like it, Frank. With that long bowsprit. A work of nautical art regardless of performance by modern standards.

 

You're thinking of the Cockle (lines above), designed in about 1912 by James Purdon. One was built here on Gabriola a few years back. Extensive build thread here

http://forum.woodenboat.com/showthread.php?88301-Cockle-Replica-Post-1

Her displacement is 5500 pounds of which 2850 is outside lead, she sails upright, not on her ear at all......

 

I don't know if that was Cockle I remember but simlar. Truly classic design and must feel wonderful to sail though wet to windward I'm sure. And all that ballast down low. Gotta love it.

 

Never seen such small boats needing so much water depth, pretty limiting imo.

 

Inefficient, you say? No doubt by today's standards.

 

They must have their merits, but the draft is extraordinary for such a small boat.

 

I made some changes, getting close to the idea I had in mind. The hollow turn in the bilge will probably disappear to keep the build simple. The hollow in the forward water line has to be wrung out, and forward sections filled in a bit. The shear line is getting a little cutesy for my taste.

 

I think that hollow garboard is essential for windward performance of a full keeled boat. The radius should get bigger the further aft you go, and the draft of the keel to rabbet should increase with the garboard radius. That's what I see on all these small boats. My guess as to why this is so is that the keel produces a large vortex on the windward side, and the vortex can produce a lower pressure on the entire windward side of the hull if it is allowed to run cleanly aft without getting cut up by flats and corners. So imagine a tornado along the windward side of the keel and figure out the shape that best keeps the speed of the fluid high near the hull. If you stall a moving fluid, the pressure goes up.

The hollow bows are as much a planking convenience as anything else. You can't have curvature at the ends of a plank, and you don't really want to have to draw the planks of a tiny boat in to the stem, It's easier to have a little bit of hollow at the cutwater to withstand bumps and bangs. Otherwise, the plank ends tend to wear faster than the rest of the hull. That isn't the area you want to have problems with first.

 

Phil, I think it also has to do with the plank on frame construction. If the keel member is level or raked them the aft area has to be built down to meet it or the dead wood. it also makes for a much stronger structure and distributes the side load over a greater area. In some cases it it to provide room for an engine.

I will keep the idea of reduction in vortexes in mind, That is an interesting point. The boat could be built entirely in strip with a light backbone structure but I like the idea of a keel structure that penetrates the hull and allows for the floors to be just ply epoxied on either side of it. Certainly building down the aft bilge is not much of a big deal on a boat this size .

 

getting a better idea of what I am after. Looking to keep disp. to 2500lb. forward sections not good.

I am fighting with Freeships a bit. You really have to design the net to the style of boat. Which means , anticipating its effect. I think it may be better to lay down some lines by hand and input via the background image, as the program starts to drive the design. Although once a
reliable control net has been designed for the hull type, it goes fast.