Launching a merry wherry for two

My friends Justin and Anne-Sophie have been working feverishly over the last few weeks to launch their two person Merry Wherry. They named it “Ohé Matelot”.

My daughter was particularly excited to be part of the inaugural launch. She helped roll the boat down from the Grin technologies headquarters down to the water at Hinge island park on the south shore of False Creek.

The most impressive things were the beautiful four part paint scheme of the hull and the LED lights imbedded in the hollow cedar and fir oars.    

 

walking the boat down Ontario street
 
last minute wireing for the oar LED lights
  
Hinge Island park has one of the only beach access points to the water
   

“Ohé Matelot” comes from a French song that all children learn

http://en.m.wikipedia.org/wiki/Il_était_un_petit_navire

One thing I noticed participating in the launch was that although the sea wall brings people close to the water it keeps us high above the high tide line and in most places separates people from the intertidal zone. Hinge park is one of the few places in False Creek where one has access to the water. I think there is an opportunity to provide more access to the water and opportunities to launch small watercraft on the water’s edge in False Creek.

Caledonia yawl project: final shaping the centreboard

Last night I got back out to the boatyard and spent a couple hours planing down the shape of the board to the depths I’d marked with the kerfs I made with the pull-saw. This technique is really helpful to keep tabs on the progress as I was using a power planer then a block plane and finally a random orbital sander with 60 grit paper.


 Once I got the taper cut for the leading and trailing edge I worked on rounding out the leading edge with the sander as well as the two ridges on each side.

The next step is to get ready to put some uni-directional carbon fiber on the sides and some kevlar fiber on the edges.

Caledonia yawl project: kerfs, planing and sanding

With a bit of further reading and some confidence building after my first set of kerfs on the starboard side of the centreboard I’m back to work on the port side.

 

It is slower progress but hand planing really makes you feel the wood and control the shape.
  
 

After removing the bulk of the material with the power planer, I switched to the small block plane which seemed to work better than the larger plane with the cedar and the curves. It also is pleasant to work making almost no noise and creating nice wood shavings and no dust.

For the transition to the part of the centreboard that pivots I need to use my random orbit sander with 60 grit. Ideally I’d like to use a disk sander or a belt sander.

Caledonia yawl project: shaping the centreboard foil profile

This part of the project was quite simply described by Ian Oughtred in his book “glued lapstrake boat building” as just rounding over the leading edge and shaping a taper for the trailing edge.

Knowing the density of water and the impact of good foil profiles for sailing performance I needed just a little more of a systematic approach. Something between CNC machining a NACA 0080 profile and sculpting it by eye.

I found two approaches that appealed to me. One was to map out the NACA profile in Excel and print out a template with a 40mm offset for a router bit and cut out the profile with the router using a plywood Guide.

Full instructions and a link to download the excel file here.

The problem was that in printing you need to calibrate for both the x & y axis. In my case when I got back to the boat shed I found that the y axis was off by 10% in the printouts. So I could not use it without reprinting. Additionally my centreboard tapers from the top to the bottom so I would need to cut several templates for the changing chord length.

Instead of going back and calibrating the print area, I resorted to a good system described in a paper by German epoxy company Gurit on building strongest & stiffest centreboards.

Gurit Guide to Wooden Foil Construction Figure 5
Gurit Guide to Wooden Foil Construction Figure 5
Testing the kerf method on an offcut from the centreboard.
Cutting the trailing edge kerfs on the centreboard
cutting the first leading edge kerfs on the centreboard

The method describes dividing the  chord of the centreboard into seven equal sections. Since the Caledonia Yawl centreboard tapers from 400mm to 230mm I did this at both ends for each chord length and then drew the lines to join them.  This allowed me to cut the kerfs to match the changing slope of the leading edge and the trailing edge to keep the same profile along the length of the board.

The other challenge is to kerf the taper of the maximum width of the centreboard as the chord gets shorter at the bottom.