2015-02-28

Post XXIV: Beggin' for a Skeggin'

In an effort to save a bit of weight (and to avoid buying another big expensive piece of hardwood), I decided to go with a softwood skeg for the boat that would be protected with a hardwood keel and sternpost. I think it will be considerably lighter than the equivalent thing in hardwood. Again, deviating heavily from the plans here, but it will produce a good result -- I hope. I took two of the cedar boards I had in reserve for strip-making and glued them together with an epoxy/woodflour mixture, then planed to the desired thickness of 1 3/16". It is IMPORTANT since these ar both flat-sawn boards that they 

The skeg needs to sit against the aft inner keel, which has a convex curve from the deepest point of the hull (roughly amidships) to the transom. Transferring this curve is pretty easy with a set of dividers. I didn't have dividers so I made some. 

Figure 85: My new set of dividers!


Then, knowing I wanted the top of the skeg level with the strongback (which is itself level) I temporarily hung the skeg stock above the inner keel (~1" amidships, ~5" above the transom) and leveled it. Then it's a simple matter of tracing a series of arcs on the skeg stock, holding the pointed end of the dividers against the inner keel. Do this so that the curves overlap. Then take a wood batten, and scribe a continuous line along the tops of the arcs. Magic! The process is commonly used to fit planks on carvel-planked and lapstrake boats; it's called spiling. 

Figure 86: No full photo documentation, but it shows the series of arcs that were eventually splined.


To finish the job I just beveled the edges of the skeg to match the groove on the keel and it was a perfect fit the first time. Very satisfying to have those boatbuilding classes pay off. I would have trainwrecked this if I hadn't known about spiling.

Figure 87: Finished skeg from amidships. 


Last thing today was to cut the transom for the sternpost. I know this is unorthodox, but I wanted something that tied into both the transom and the knee that will eventually be fit inside. Since the skeg is not all hardwood, durability is a concern. It might look a bit funny in the end but I don't much care. 

Figure 87: Finished skeg and transom slot from the stern.


2015-02-11

Post XXIII: How to attach the keel now?

Just a short update this time. Had to have a sit on the stool and think about this one for a good while. I did NOT do the inner keel right when I initially set it up. It should have been beveled so that the planking would come up over the top of it and meet in the middle. Time for another hackjob on the bottom. Remember again: Paint. 

The solution I came up with was to dig out the rabbet planes and cut back the planking so that an inch of inner keel would be exposed all the way along the spine of the boat. Planking on either side of this inch-wide gap was cut at approximate 45deg angles so that the outer keel and skeg would sit and align nicely in the trough while still maintaining a good width.  

It's a good idea to have a template for this type of work so you aren't constantly measuring (Figure 82). I roughed the trough out with a framing chisel and then used my Stanley 78 rabbet plane to smooth out the rough job on both sides. The result was not fantastically pretty, but I think it will work. My template now slides nicely from the transom all the way to about 24 inches from the bow, where I don't really have enough keel to continue with the inch width. Here I'll just eyeball it and then custom cut the outer stem to fit the narrower trough width as necessary. 


Figure 82: Template for cutting the trough


Figure 83: Closeup of the finished trough. Cedar strips on the sides and exposed inner ash keel underneath


Up at the stem, none of this trough business is strictly necessary. The original design called for an outer stem that sits flush with the inner stem across the end grain of the planks. Fair enough. Got out my little block plane and shaved it down to the face of the inner stem. Transition to the trough happens at about 12" back from the bow (or thereabouts).

Figure 84: No trough required up front where the outer stem goes. 


Note, this is the first time that I can actually see the true shape of the bottom without ugly odd-length ends of planks sticking out. Cue another 20 minutes of sitting on the stool and admiring my work!