9
Fairing the molds:
We are now ready to fair the molds. Fairing is
a most important part of hull construction. Beginners tend to rush
this step and jump right into planking. Take your time and check
the fairness thoroughly. Then you won't run into problems when
you start planking.
Fairing is the process of beveling the edges of the molds so they lie
in a fair curve. Before you begin, note that molds 1, 2, and 3 are
lofted and cut to the inside of the planking and do not receive
frames while molds 4 through 15 are lofted and cut to the inside of
the frames and do receive frames. Therefore these two sections
must be treated as separate entities. That is, fair molds 1, 2, and 3
separately from the rest. It would also be reasonable to wait to fair
molds 1, 2, and 3 until after the frames are installed.
Some of the molds at the bow and stern are laser engraved with a
bevel line that was determined when the hull was lofted in CAD.
Begin by rough carving the bevels on these molds with a knife,
leaving some material to be removed by sanding. The bevel is so
slight on the rest of the molds that they are best sanded in. Note
that the bevels should be carried all the way down to the building
board. This is so the frames we will later bend on will lie properly on
the mold edges and follow the bevels. Lay a basswood batten
against the mold edges at various locations to check for fairness. This
process will show you where you need to sand in bevels that were not
pre-cut on the bulkhead edges, and where bumps and dips may need
to be corrected. Proceed slowly and carefully. If you should snag
and break a mold, that’s what glue is for. Patience is the ticket here.
Use a sanding stick that is long enough to cross at least 3 molds.
The manicure type sanding stick shown in the photo is ideal.
Otherwise glue sandpaper to a suitable backing. Note that the laser
burn on the edge of the molds gives an indication of how well you
are proceeding with the fairing process. When the laser burn is
nearly gone, you are pretty well faired. Also note that in the photo
the fairing of the molds has yet to be taken down to the building
board level. The need for this will become obvious when we begin
to bend on the frames. Molds 1, 2 and 3 require the most material
removal in the fairing process.
Fitting the keel, the keel alignment tabs:
Once you are satisfied
with your fairing, test fit the keel assembly to the jig structure.
Molds 1, 2, and 3 may require trimming a bit in way of the keel
assembly to allow it to lie directly on the center keel. Align the
frame heel notches in the keel with the molds. When all is well lay
the keel aside and let’s install the temporary keel alignment tabs as
shown on sheet 2. Spot glue these tabs in place; they will be
removed during the planking process. When dry, slip the keel
assembly between the tabs and make a final alignment and
positioning. Drill through the tabs and keel and pin the keel in
place. For the prototype, ordinary sewing straight pins were used,
see photo 7. The drill size is 0.028" dia., a #70 drill. These tabs
and pins align the keel fore and aft and also hold the keel down
while the frames are being bent in place.
Stem alignment blocks:
Glue the laser cut stem alignment blocks
to mold 1 on each side of the stem as on sheet 2 ensuring the stem
is centered. Cut a short piece of 3/32 dowel to temporarily lock the
stem head in place.
Transom horses,
installing the transom:
Glue the transom horses
to mold 15 as on sheet
2. Lay a straight edge
across the faces of the
horses and the stern
post. If necessary shave
or add material to the
horses so that the horses
and the stern post are all
in the same plane. Note
and cut the bevel in the
transom where it meets
the keel. The transom
may now be glued to the
stern post. Take care
that the transom is
centered on the stern post and is square with the world. That is
measure up from the building board (baseline) so that the transom
is at the same height on either side of the keel. Drill #70 drill
through the transom into the horses and tack nail the transom to
the horses with brass nails as in photo 9. This fixes the transom
firmly in place and readies it for fairing. Note that the transom is
also lofted to the inside
of the planking and
should not be finish
faired until the frames
are in place.
This finishes the
building jig and with
the keel, stem, sternpost
and transom in place
we are ready to start
building a boat hull.
Photo 6, fairing the molds
Photo 7, the keel alignment tabs
Photo 8, stem alignment blocks
Photo 9, affixing the transom
