14ft Racing Dinghy - Comments Please

The surprising thing about the singlehanded Northie is that it doesn't seem to go anywhere as well as most of us would think it should. The yardstick is about the same as a Laser. While that may be an unreliable measure (the 1-up Northie is a tiny class and our yardsticks aren't very reliable IMHO) at least one of the top NS14 designers had noted the same thing some years ago, and said that it's probably because the standard hull just doesn't work well when it's sailing well above its lines - too much windage and volume and insufficient form stability. I used to race a Tasar singlehanded against a group of singlehanded NS14s. I was greatly surprised to find that there wasn't a great deal of difference, since the Tasar is far from a good singlehander and I expected a lot more from the NS.

 

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Pi, I'm probably having brain fade again but what to you mean by this? The "rake" of the bow appears to be the same for both plans as I understand it. What am I missing?
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Picture below is what I understand to be a "raked bow"; your bow appears to be a vertical or plumb bow and the bow on my boat is a reverse bow(as I understand it).

 

Bugger, I must have posted the wrong thing!

 

THIS is what I meant to post - the version with the raked bow.

 

Ahh---looks good...

 

Reminds me of Dudley Dix's paper Dart, also the Puerto Rico Chalenas

http://dixdesign.com/pjvideo.htm
http://www.woodenboat-digital.com/woodenboat/20070102/?pg=48
http://www.boatdesign.net/forums/wooden-boat-building-restoration/getting-started-19402.html

 

you mean the paper JET from dudley dix - do you?
http://www.dixdesign.com/paperjet.htm

edit:
sure... haven't clicked on your link...

 

Hey Pi, can we see a Sail Plan or sketch?

 

Now go build & post pictures

 

All in good time! I want to get the cockpit design sorted. I am toting with going quite radical there, taking cues from car design re different materials and instrumentation displays. The rig will be a carbon NS14 wing mast (but 30cm longer) with square head main and self tacking jib similar to a 29er. The assy kite will be about 12m^2, so smaller than most. The Bethwaites seem to try to shove as large a kite as possible on their boats, but I have a firm conviction that most weekend sailors like them to be as small as possible.

 

Worth thinking about ... larger masthead asymmetrical kites are much easier to gybe than smaller fractional ones that are closer to the forestay. Smaller fractional kites get caught up and wrap around the forestay, where masthead versions "float" through the much larger "hole" much easier.

My singlehander has a fractional asymmetrical 29er sized spinnaker, and you have to be very careful about the sheeting and attachments to avoid the sheets binding on the forestay during transitions. I've gone with a little spliced tail in the sheet to attach to the clew, with no knots to impede the sheet movement on the forestay.

Given that asymmetricals pretty much dictate apparent wind sailing and preclude DDW soaking, the increased area of a masthead kite isn't as problematic as you might think. You do have to adjust your reactions to gusts - heading downwind instead of up, and choking flow via sheeting in instead of letting the kite flap.

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Bill

 

I understand what you are saying Bistros, but that's only half the story. I've been sailing assymetrics since '93 and I understand that the gap to gybe the kite through is bigger, but they also take more hoisting and dropping effort. A trawled drop can easily lead to a swim, and that's not what this boat is about.

Most fractional kites are still very easy. I strongly believe that the RS200 is so popular here (UK) because it has the easiest kite in all the world. There's no good 'sailing' reason the 200 should have an assy, but it has made the boat a success. I want to be able to carry the kite comfortably, not on the edge.

On the spreadsheet I posted on page 2 you can divide the Sail Carrying Power (SCP) by the downwind sail area for each boat. This is effectively how powered up on a reach each of the boats is. I have a much larger spreadsheet with many more classes on it and it is noticable that boats with good allround performance score in the region of 0.5-0.6 on this metric. Boats with a value higher than 0.6 tend to be underpowered downwind (such as kiteless boats), whilst boats with a value less than 0.5 tend to have a reputation for only being able to sail windward/leeward, which is no good for most UK club courses.

Even a small mast head kite would have an area of 16sqm, which would give a reachability score of 0.44, which is too low for what I want from this boat. At 12sqm, the Volant scores 0.52.

Quite apart from that, my proposed mast is too soft to take a masthead kite. I wouldn't want to stiffen the mast because then it would lose its gust response capabilty, so a fractional is the only way to go.

Wow, that turned into a longer reply than I expected! I still welcome all comments - its good to challenge all design decisions and I love discussing the finer points of design. There is so much to learn!

 

masthead kites on an unsupported rotating NS mast would indeed be quite a challenge. You could try to put some uppers on it but I don't know if they would be effective or just contort the mast into unpredictable shapes.
That said, avoiding beefing up the mast out of concern for gust response might be overly cautious. I designed and built northy sails for a few years and what I think I learned is that I don't think gust response in the NS rig comes in quite the same fashion as other skiffs. The masts are so stiff fore and aft that there is very limited bend available and I think depowering is more about sheet trim than flattening. The sails for these wing rigs are already very flat so there isn't the same need as arises in other skiffs that rely on varying the mainsail camber through mast bend.

 

I dunno, PI Design's shape incorporates most of the developments in fast dinghy and skiff design in the last 25 years. These developments made for boats with less wetted surface area, more dynamic lift, narrower waterlines, less form drag, and (all in all) higher speeds.

The Paper Dart looks like something from 1970. In some ways, that's fine - I just had a lovely day of one design racing in a class (Tasar) that is similar in some respects, although the Tasar was a product of years of development by world-class designers. And the older flat hard-chine shapes have a lot of good points when it comes to speed with stability.

There's no real disrespect to the PD's designer, but the fact is that (as far as pure speed goes) the boat ignores most of the lessons learned by the world's best dinghy designers over the last couple of decades. The modern U-shaped hulls like PI's are simply faster in most conditions.

 

Dudley Dix' Paper Jet (so called for it's folded Paper Airplane feel) was designed for low-skilled homebuilders using plywood - hence it's flat panels and straight edges. It was clearly not designed to be as fast as possible - it's mandate was to have three rig options allowing everyone from 80 pound junior to 200 pound dad to sail the same hull.

In it's top end configuration it is still pretty far from current in rig design. It does have a trap, and it does have a large roach main, but it isn't close to a MPS, RS700, 29er or my Falco in terms of design.

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Bill