Sunday, January 31, 2010


I finally started building the last week of the month -- after going nearly 8 months without. In the end it became evident that there would never be a good time to restart, just like there was never really a good time to start in the beginning. It's all about inertia, and I had to turn the tide.

Instead of jumping in with rebuilding some of the flat parts for the aft cockpit, I decided to make things more interesting and finish other parts.

This included the beam mount additions (note: I have early, not updated versions).

And then I started the rudder. I followed in the footsteps of Meno and Grant. It's a technique that makes so much sense to me for making one-off versions of the rudder and, in my case, centerboard.

The cross section of the foil is given at key locations on the full size patterns. I measured the position of common thickness along the cord from the leading edge. The different thicknesses chosen are arbitrary, but should be spaced to allow setting and running the router along the resulting topographical map.

Once the points are plotted and connected, one begins to appreciate the design in a 3D fashion. (Many areas are actually quite flat, so determining, say, the exact 0.8 mm location on the trailing portion can be difficult. But when drafted out the data can be artistically averaged-out as the intent of the shape becomes obvious.)

And then I discovered that after 8 months off, you can forget all the steps. I vacuum-bagged the blank, but when I opened the package I found I had forgotten to wax the table! Wow, that stuff sticks -- I had to ruin the blank and in the end, the table.

So, the message is to review new or past techniques before wasting materials.

Once I recreated the blank, I was almost glad that I'd had trouble. I had been trying to be conservative with foam and was piecing together some odd leftovers -- in the end this technique is about knowing the exact center and having a uniform surface and thickness for the router. Using a new single sheet of foam to cut from was better towards this end.

My blank has a single layer of glass sandwiched in the middle that is not called for in the plans. The thought is that this will help the blank stay true while being shaped without its outer skin.

I cut out the parts which will be HD foam including the central core.

No comments: