Sharpie Design Build Sail The Designing

In this video I discuss and show how I designed my 7 meter (23ft) design based on the Sharpie concept of yachts. You can follow the steps from deciding the length, working with Paulownia Timber in the design, developing the lines, calculating the righting moments required and much more.
Next video is about the rig, which is based on the Sharpie Cat Rig but using the Ljungström two ply sail which furls on the rotating mast. Find out if I go for one or two masts!

[@brendendelaney267]

Looks great, look forward to seeing the progress.

[@KarlFullerNZ]

Thank you! Yes, I'm looking forward to the progress too and trying not to miss out on another summers sailing.

[@bentucker5009]

Looks like a good design. Keen to see how it all works out. I am interested in your NIS 23 numbers. I've weighed my NIS23, including the ballast. The ballast is about 340 of lead ingots inside, and another 60 kg or so on the centreboard. Total weight is very close to 1000 kg empty. So the ballast ratio is probably close to 40% unless you include the 25mm thick plywood hull bottom. I need to measure the waterline length. At rest and light, the knuckle of the bow is just clear, as is the stern. But I very much doubt it's anywhere near a meter of overhang. The waterline beam is very narrow, and the max beam doesn't really help much until about 30 or 40 degrees of heel, where she tends to stiffen up significantly. It would be interesting to compare the design hull shapes. I was interested in your software. Is that the Orca add on to rhino?

[@KarlFullerNZ]

Good to hear you have a NIS 23, I was seriously considering to build one and if one had come up for sale in NZ, I might be an owner of one now. I think there is possibly only 1 in NZ. It's interesting to see what you have determined as the numbers for your Sharpie. My design certainly departs from some aspects that typify a Sharpie, I certainly have more draft and the ballast deeper which has plus's and minus's. Rodger Martin gave a very good explanation of why ballast in the bilge can work so well, being that the ballast is more in line with the forces that resist the hull so can give less pitching and because the sail area is lower, the sail moves less fore and aft, so reducing the 'angle of attack' constant change. Having the ballast as part of the bottom is good, having the dual purpose of making the hull extra strong and of course, being part of the ballast. I just did a rough calculation and you could easily have over 200kgs of plywood in the bottom of your boat, adding to the ballast. Having a narrow WL has it's merits. I only have rough details of the NIS 23 but just having a look at my drawings, I have the NIS 23 having a WL Beam of 1890mm and my boat is about 1647 at the same place in the middle of the yacht but my max beam is a bit aft of that, coming in at 1787 a meter aft of the middle. I was a bit surprised by that, I thought I remembered my yacht had a little more, it certainly does at the deck level, being 2450. Yes, I use Rhino CAD and really like it, it's so intuitive to use I find. I used to have Rhino Marine which became Orca and hadn't had it that long when they dropped support and became Orca and I wasn't prepared to pay for the new software which if I remember correctly is a lot more than Rhino itself! It's great you touched base considering the yacht you have and I too am interested in the comparisons. I presume you're in Aus, there are so many NIS yacht there? I really enjoyed seeing the NIS yacht sailing in Sailing Kate and Louise.

[@bentucker5009]

@KarlFullerNZ interesting. I would have thought your design would have had a wider waterline beam. I guess that's the advantage of the radius to the sides. A while ago I did some 3d modelling on freeship to see what happened if the NIS had another topside chine, it drastically improved the initial stability. It's probably a worthwhile improvement, I think. I could probably send you the files, but they are a bit tricky to import into Rhino. The inside ballast has the big benefit of being easily removable. This makes it much easier to tow the boat, and manhandle it ashore. The bare hull is probably close to 650kg, which I can slide on and off the trailer ashore and roll it over on my own pretty easily. The NIS 23 rides very well in a seaway, i wonder if this is due to the inside ballast and lack of form stability. It feels like a much larger boat, though it rolls a bit downwind, and heels over much further than we are used to these days. Another nice thing about having the majority of the ballast inside is that the boats stability isn't much less with the centreboard raised. I used to sail a ross 780, which was very unstable until we got the centreboard down. I quite like the waterballast idea. I'd be keen to add a bit to my sharpie. Especially handy if I could somehow use them for fresh water storage on longer trips... Yes I am in aussie, down in Tasmania. Its a nice place to sail. I'll be interested to hear how the rig experiments turn out. I've come to really like the yawl rig. The little mizzen makes heaving too simple, and prevents lee helm when deeply reefed, without cluttering the cockpit. I am almost tempted to experiment with a smaller mizzen on the NIS23.

[@rcralphpfister]

Interesting stuff 😁

[@KarlFullerNZ]

Thanks Ralph. I'm glad to hear your sail to Fiji went so well, your average speed was good, and you got 12knots from a 50ft steel yacht! I'll never forget the night I was getting a steady 14, peaking up to 17 on her, on our way to Tonga. Plenty of time to beat the record 😉

[@Cptnbond]

Wow, that's interesting. I liked that you took the time to discuss your thoughts and share your knowledge. Keep up the excellent work. What is the title of Gerr's book? Can you share the information to find more recommendations by YDE that you refer to in your spreadsheets? I subscribed immediately. Skip the music, this is fantastic material without it. Cheers.

[@KarlFullerNZ]

Thanks for the encouraging comments! The Gerr book is Called Elements of Boat Strength. It's quite comprehensive and covers pretty much all boat building. This is the website where I got the YDE Scantling guidelines www.macnaughtongroup.com/default.htm and the email for Thomas McNaughton is [e-mail] He sends a the formulae as PFD but they need putting into a spreadsheet which I can't supply sorry because they do charger a little for the info.

[@Cptnbond]

@@KarlFullerNZ Thanks Karl, I appreciate your quick answers. Cheers.

[@gilray1977]

What are you using for a design program ?

[@KarlFullerNZ]

I use the Rhinoceros CAD Program which is not dedicated marine hull design software but does have some great tools. I used to have plugin Rhinomarine which was great but they folded and became I think Orcra3D