Fairing the backbone



While the battens are still tacked to the molds and the stem, now is a good time to fair the backbone.  The backbone consists of the keelson, stem and transom, and all must be beveled to fit the strakes.  I started with the keelson first, since it’s the largest piece.  The keelson is rectangular, and needs a bevel cut from the centerline to where it mates with the mold.  This, and also all the other bevels, are called rolling bevels because they are not constant throughout the length.  The amount of the bevel, at say amidships, is relatively shallow, while the bevel at the stem and transom are both very steep.

Start by making a “witness” cut from the outside edge of where the first strake will be to the centerline of the keelson.  This is done at each mold.    If the mold is rounded in this span, it will need to be flattened out so that the strake will have a flat surface to lay on when it is installed.

Rule #6.  Hand tools remove wood slowly.  That’s a good thing.  Power tools remove wood much more quickly.  If you remove too much, that has to be fixed.  That only happens after the copious use of vocabulary that shouldn’t be used in front of your grandchildren or Southern Baptists.

On the keelson, I started removing the bulk of the wood using a power planer, which is really a wonderful tool.  But I stayed proud of the intended final cut, per Rule #6.  The finish work is done with a Surform rasp, which I nicknamed the “cheese grater” on account of it’s cutting surface.

To check my progress, I tacked a batten along the edge of the first plank (garboard) and then had a small stick to check my progress on the bevel.  When the stick lay flat from the edge of the keelson to the centerline, the bevel was good.  See below.

2016-04-17 Fairing the keelson.
2016-04-17 Fairing the keelson.

A similar process was used for the inner stem.  The batten was tacked to the stem, and the stick rotated around, taking small amounts off with the cheese grater until the stick lay flat on the stem.  Since the battens were still tacked on from lining off, the stem was faired for the remaining strakes.  I also cut the bevel for the first strake on the transom; the bevel was determined by following the line the batten made as it extended past the transom.

2016-04-17  The stem is faired (beveled) to accept the strakes.  The horizontal lines on the stem mark where each of the strakes will lie.
2016-04-17 The stem is faired (beveled) to accept the strakes. The horizontal lines on the stem mark where each of the strakes will lie.
2016-04-17  Fairing the stem on the port side.
2016-04-17 Fairing the stem on the port side.

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