As a break from working on moulds for my new battens, I've drawn a stub keel with 65-010 section, 150mm deep, to be cast in lead, bringing the draught to 640mm. A shade more than Annie's 2ft. I think I would want more ultimate stiffness than can be achieved with only 490mm of draught and internal ballast, for going down to Stewart I., or any other exposed passage making.

Yet having got a design drawn out, as I have now, it's remarkably easy to play "variations on a theme". You'll want considerably less displacement than Annie. No problem, I can do that. There's a thing called a "Lackenby transformation" that enables me to change the displacement, prismatic coefficient and so on.

So now we have several potential clients! Annie Hill, Peter Scandling, David Thatcher ... and for my old age, I'd like one to be magicked into existence for me, so that I could keep her in Ravenglass harbour (just the right boat for that) and use her to explore the further reaches of the Solway Firth and Morecambe Bay, where the chart gives up and almost goes as far as saying "here be dragons".

I think anything less than a meter draft is good and 640mm is getting quite shallow, and there is not that much difference between 490mm and 640mm. Probably what is more important is for the vessel to be able to take the ground easily and sit upright and that is where having no stub keel would be good in that the boat would probably sit upright on its flat bottom. With a stub keel legs might be required, or the daggerboards utilised. But I see a stub keel as desirable to get the ballast lower and would provide some protection to the hull when grounding.

Less displacement would certainly be what I am after as it has the potential for more speed for the speed freak!

The more I look at your design David the more I like it and if I am interpreting the drawings correctly the transom sits well clear of the water? I would still like to see more beam in the stern sections, maybe by utilising flare in the topsides at the stern but that would need to be married into the raised bulwark around the cockpit. If the cockpit seats/deck were extended just a little bit outboard of the hull that would make a break between the hull and the bulwark so the flared topsides could work. Also when I look at the drawings I think more crown in the deck so as to provide more headroom and maybe improve looks from the bow, would be a good thing, (for me at least). 

 

Graham Cox wrote: It is the desirability of having the top panels cut flattish for heavy weather cruising (as one might expect in occasional forays to Stewart Island) that concerns me about the Pugwash type of sail plan.  It looks like a Van Loan style of sail, and the low-angled yard seems to me to be an inefficient shape when you are down to your last couple of panels, if it is flat cut.  If you need to sail efficiently to windward in strong winds and a developed sea, I think a flattish-cut, fanned peak, with a high-angled yard is more desirable.  As I said earlier, for daysailing, when you might expect to carry full sail, the criteria would be different.

I think it's going to be "horses for courses", Graham. A basic boat with the possibility of different rigs for different skippers and different uses. Annie wants a rig with low loadings, David Thatcher wants a wing sail (so would I), and I don't see why any owner couldn't have what they fancy, within reason. 

David Webb wrote:

David Tylers response to the SIB LIM Challenge looks great and very professional in its presentation. As a slight change of pace I have posted four photos of some freehand sketches I have done of a proposal to meet the challenge in the illustrations section of the Technical Forum. I am still without a drawing board and my efforts to download and learn/use Free Ship have proved frustrating to say the least, so this is what I am able to show at the moment. Annie has told me she is not happy with some aspects of Korora which I posted earlier so Puffin is another attempt to meet the challenge!

My proposal shows a flat bottomed design with radiused chines and a box keel which contains the ballast of steel punchings and cement. Construction is of plywood on a frame and stringer framework. I have tried to incorporate as many of Annie's wishes as I can, but some have been compromised.

Comments would be welcome, especially from Annie, David Thatcher and David Tyler.  As soon as I get my drawing board set up again (after I have built the new room on to our place!) I will draw up the design accurately and re post it ( unless David Tyler can draw it for me on his computer program??)

I look forward to your feedback.

Interesting that you've gone for a "barge yacht" kind of midship section, David. This can be a seaworthy hull form, and provides a lot of volume for living space. You seem to be able to get the sleeping berth and heads further outboard than I can, but I wonder whether you can still achieve that when you start to design accurately to scale. That's what I found, anyway, when I finished sketching in 2D CAD and transferred to 3D Freeship to draw the hull properly.

How do you propose to make the radiussed chines? Double diagonal? I wanted to put on the kind of compound curvature that Tystie has below the waterline, but Annie wondered whether it might be beyond her skill level. It would certainly take longer to build, even than multichine. Radiussed chines have mostly been used in high-budget boats, and I don't think we're in that game.

Annie Hill wrote:

Graham Cox wrote:
I'm feeling a bit shy about expressing an opinion here, with only 3000 miles coastal cruising under junk rig, so take this with a grain of salt.  I think a cambered "Pugwash" sail will be very effective in light airs, if all the panels have well-developed camber.  This is the sort of sailing one mostly does when day-sailing, but I find the 3 top panels of Arion's sail, which are fanned and have a high-peaked yard, with little camber in them, very effective as a storm sail. 

Graham - you've done thousands of miles under Other Rigs and so will be very aware of what your junk rig does and doesn't do.  I quite take your point about camber.  David and I haven't yet discussed the degree of camber in the sail: his 'new' sail plan is new to me, too.  I'll post our relevant conversations about this, soon, I hope. 

However, from what I know of David and from my own preferences, we would go for graduated camber in the sail, with the greatest at the bottom to a near-flat or entirely flat top panel, as in Fantail's sail.  His new sail plan doesn't have many panels and by the time we've finished thrashing it out, it could well end up rather different from this current suggestion.  David is presently on retreat in a quiet anchorage where he can get on with working on Tystie's rig, but will no doubt address your comment when he is back on line.

It is the desirability of having the top panels cut flattish for heavy weather cruising (as one might expect in occasional forays to Stewart Island) that concerns me about the Pugwash type of sail plan.  It looks like a Van Loan style of sail, and the low-angled yard seems to me to be an inefficient shape when you are down to your last couple of panels, if it is flat cut.  If you need to sail efficiently to windward in strong winds and a developed sea, I think a flattish-cut, fanned peak, with a high-angled yard is more desirable.  As I said earlier, for daysailing, when you might expect to carry full sail, the criteria would be different.

My inclination is also for slightly higher aspect ratio.  David and I continue to discuss this.

Maybe because I am  'speed freak' I should be aiming for a David Tyler soft wing sail.