Friday, August 16, 2013

Classic Moth Plans: Offsetts for Zippy Design

(Update December 2013: For those who like the visual lines drawing the Zippy sections in PDF format are posted here.)

(Update February 2015: I finally have compiled and posted here the 8 station offsets which will make it easier to plot out frames.)

Plans de voiliers classiques Moth, Dériveur classique Moth.

There are two "wide-body" Classic Moth designs currently kicking around, the round-bilged Titan, an American design, which is featured in this header photo, and the French Proust design which I profiled in this post. The Proust design is a simple, v-bottom shape and should be easy to plank in plywood though Jim Young built his version in fiberglass/foam-core. If you build it with the open cockpit as Jim Young did (rather than the racing cockpit), the Proust should be more than capable in taking an adult and a young kid for a pleasant day-sail.

Jim Young named his Proust version Tippy, a misnomer since this design has more than enough stability for a Mothboat. I've taken the Proust and made some changes and in keeping with the Jim Young naming convention, I've deemed my version  Zippy.

The Jim Young Tippy at the 2008 Elizabeth City Nationals.

The original Proust had a chine log which I've eliminated to make it a true V-bottom. I changed the rocker and the sheer slightly. I have it on my list to make a model of Zippy but as my friends know, my projects take a very long, long time. If anyone out in the bloggosphere would like to make of model of Zippy, please send along photos and I'll post them.

Here are the the 8 station offsets for Zippy in metric. To print or download, click on the pop-out icon on the top-right corner. It will open the PDF in another tab where you can print or download.

Here are the offsets for Zippy for stations set at 336mm (13 inch English) which is really too many for a traditional build where you leave the frames in the boat (like the Nantais or Little Mae Moths).

And here is "Zippy the Pinhead", the cartoon star, the enigmatic master of dry wit from another dimension, a cartoon I always checked in with daily even when I didn't understand where he was going.

Where to put the mast and daggerboard in a Classic Moth?

Luckily, John Shelley's construction drawings for the Shelley Mk 1, which he used in a patent application, have now surfaced on the internet. His mast and daggerboard placement as indicated in the drawings below are good placements, though, if you went around the fleet with a measuring tape, you would find this might vary by up to 75 mm from boat to boat.

Center of mast back from stem - 695 mm.

Leading edge of daggerboard back from stem - 1453 mm.


George A said...

Rod: You can still follow Zippy the Pinhead by going to the on-line version of the Wash-Post and searching through the comics section under the "entertainment" tab at the top of the home page.

You really should consider modifying the plans for Tweezer D so that the hull stays roughly the same shape but has a touch more rocker. I still think Tweezer would go in light air if you could reduce the wetted surface a little. I know that the intention was to build a fast boat that was easier to control than a Mistral but you've stopped the experiment after just a single attempt!

Tweezerman said...


Thanks for the tip on Zippy. Didn't know that you could follow him online.

I did another version that I thought would be closer to the Mistral in speed but lost the competitive desire to really go after the top end of Gen II (it's lots easier to pick up the extra Mistrals kicking around than build another stripper).

George A said...

Careful, I just may have to sell you a Mistral hull!