Wednesday, August 17

 Geoff talked about fairing in the bow stem, aft stem, keelson, planks, etc. The first tool is the 9” grinder fitted with 60 grit paper; it removes material very fast. It is important to keep your feet and the sander moving. Sanders should be started while in contact with the wood, and turned off while in contact with the wood. When you find a bump, Geoff advocated going at it “with gentle love” rather than aggressive spot sanding.

When sanding the planks, it is important not to round over the edges; clean, hard lines need to be maintained. They can be touched up later by hand if needed. Corners are initially cleaned up with shaped scrapers and heat followed by appropriately radiused sticks with sandpaper.

It was emphasized that fairing is not done in one step; it is a reiterative process. Sand, fairing putty, sand, etc.  Fairing photos start here.

We were then introduced to the two main types of fairing compounds. One is phenolic microballoons, which consists of microscopic plastic spheres. It is probably the most useful for home construction. West 407 is an example of this. The other fairing material is Quik Fair (System Three). It is a two part product that is mixed as needed in a 2:1 ratio. Whichever system is used, putty knives apply and smooth it. A flexible yellow spreader was used for larger areas. Asides: Putty knives are cleaned using the heat gun; screw holes should be smoothed from the mid-point out on each side. In filling the scarfs, only the gentlest pressure should be applied.

In fairing around stem, keel, etc., microballoon compound can be applied with a pastry bag.

We then set about fairing the entire hull. Screw holes are packed with fairing compound and then the putty knife is set at the center of the hole and pulled outward; repeat from other side of hole. On scarfs, feel for hollows. Use a wider knife or yellow spreader. Use one gentle swipe; don't keep coming back. You can further correct on subsequent rounds. Around stems, keelson, etc. compound can be applied with the pastry bag and faired with the finger tip.

Geoff then went over locating the pivot points for the CB and CB box. Points are indicated on plans, but location should be played with to get ideal location for function and adequate distance from edge for sufficient strength. Play with the patterns. On the Ness, Geoff felt that some adjustment from the plan location was called for. However, by moving the hole, it was no longer through the CB logs. Therefore, the the hole had to be reinforced from the outside of the CB box. The hole is 7/8” in trunk; CB is over-drilled to 1” diameter and filled with epoxy. The final hole through the epoxy is 1/16” larger than the pivot bolt. The pivot hole has a metal washer and neoprene washer at both ends. The neoprene is against the trunk.  Click here for photos.

In the afternoon, we addressed the outwale and inwale construction. The outwale is rounded over with a 1/2” radius on top, 3/8” on bottom; the inwale has a 1/4” radius on top and bottom; the edges of the inwale on spacer side are left square. The larger radii need to be done with multiple passes of the router.

We fitted the CB box. The slot was too small (on the keelson), so one end of the box was planed and the slot enlarged so there was congruency between box opening and slot. Quite a bit of fussing was needed to get the CB box in to the vertical plane; there are no flat areas to use true it with a square. Ultimately, sighting from bow and stern is critical.

Next, the previously cut rail and spacer blocks were epoxied in place, which required more C clamps then most people own, so at home, this will have to be done in installments.

A decision has to be made prior to epoxying the spacers. We placed them flush with the top of the sheer plank. It might be desirable to mount them (and the inwale and outwale) slightly proud of the sheer and later adding a filler strip to hide the plywood edge of the sheer plank.  Photos of the inwale/outwale/spacer blocks begin here.

On to spar making. Look at the plans and check the scale, which is sometimes different for the spars vs the rest of the boat. We'll make spars solid except for the fore (main) mast, which will be hollow. The thickness of some of the solid spars is such that two pieces of spruce need to be glued up. They pieces should be thicknesses equally (in one of our cases this was two 1 3/16^th” pieces).

Solid spars are cut to length and a centerline snapped. Half breadths are marked at stations from data on plans. A batten is used to fair out the profile. A rough cut can be made on the band saw, followed by planing. The blank is then rotated 90 degrees and the process repeated. This yields a blank that is square at all stations. The spar is created by then planing from the 4 sided structure to 8 sided, to 16 sided, to 32 sided. In going from four sided to 8 sided, an shop-built marking gauge was used. From 8 sides up, the planing is just eyeballed.

The hollow mainmast requires a different approach. Eight staves are connected using birdmouth joints on the edge of one plank connecting to the square edge on the next one. The thickness of the staves is 0.2 x max diameter (3” in our case), thus 0.6” or approximately 5/8”. This stays the same regardless of taper. The width of the staves is 40% of the diameter at any given point. This controls the taper of the spar. Only one side of the stave is tapered.  See spar making photos.

This process is fully describe in a Wooden Boat article: Bird's Mouth Hollow Spars by Aime Ontario Fraser, WB Vol. 149 (July/August 1999), pg. 31.

End of the Day Progress

All photos of the Ness Yawl 2011 class may be viewed at: http://www.flickr.com/photos/21597525@N00/collections/72157627358772597/