Monday, February 08, 2021

Starting again: Another guide boat

What if I shorten my guide boat design to 14' to make it easier to transport?  What if I widen the plank keel slightly to make it more stable?  Should I increase the freeboard?  Can we reduce the weight?  Wouldn't it be neat to use all dimensional lumber with no plywood?  Perhaps I can finish it clear.  I want to use a new and stiffer material, "Ramboard", for making patterns; it should be more accurate.  So many reasons to build another boat; none of which have to do with actually using the boat.

For me, designing and building a boat is the equivalent of an artist starting a new painting. What artist only paints a few paintings?  Each painting expresses a separate vision.  Creativity proves we have control over at least part of our lives.  And with the demanding dimensions required in a boat, there is the mental challenge.  And so it begins.

The bow profile built from two scraps of 2x4 Douglas fir.  I built two of these, and they will require further modification for the changing bevel along the lower edge.  I have also roughed out the plank keel, the edge of which will also need to be modified to accept the garboard plank.

This shows a double stack, 12 frames. Two more frames need to be built; both will be bonded to the bow profiles.  Then I can start putting things together.  Of course, these frames will require further modification; notches for the stringers and sheer and further finishing.  They are half-lapped and bonded with epoxy.  Built from lumber left over from other projects; you can notice the varying grain.

The bow profiles have been bonded to the first frames.  Next, these assemblies will be bonded to the keel as the sheer is installed.  The chine and sheer curve lengths and stations have been calculated and, when installed, will force other frames into alignment; thus, eliminating the need for a strongback.

Frames trial-mounted on keel for an initial view.  The frames need to have notches cut for the sheer and two stringers before final assembly.  It is snowing outside with below zero temperatures; a great time for a project like this.

Making progress.  All the frames are in place and the sheer is in place, as well as two strakes.  Note that no strongback was required.  The measurement along the sheer for each frame has been calculated; thus, each frame can only be positioned at one exact place.

This hull will be one foot shorter that the completed hull nearby but with a wider plank keel.  Why am I building two boats so similar?  I have some new planking stock to try out; I have new pattern-making material (Ramboard) to try; and I think the shorter length may be easier to transport.  I have also planed the plank keel down to a thickness of 0.4 inches to reduce weight. 

I used an angle grinder (40 grit) to bevel the stems when fairing the overall hull frame.  All ruling lines are calculated and parallel, which made it easier to visualize the  required angles.

The edge of the plank keel has been routed to create a solid landing for the first plank.  At the ends, the plank edge is curved with a constantly changing angle.  This needed to be done carefully.

Carefully fitting 2 inch wide by 0.21-0.24 inch thick planks (not quite quarter inch).  I picked two inch wide planking because that is the thickest wood my table saw will willingly cut, and that is the widest that many of my clamps will span.  No fasteners used; only epoxy adhesive.  The planks are falling into alignment quite nicely; much better than when I used plywood.  To get the length I need, I am scarfing together shorter lengths using a 7 degree bevel on my chop saw.  Perfect results using a simple jig, and it only takes seconds.

Using real planks have given me insight into the design of the original Guideboats.  Upswept sheer in the ends of the boat facilitates easier planking.  The greater length of curve from keel to sheer spreads out the bending stresses and provides a better landing for plank ends.  That end curve had to be a conic projection in order to fulfill all requirements, although the first builders I am sure were not thinking of mathematics but instead just ease of planking.

I am enjoying the nice fair curves that the planks follow.  Relying on epoxy adhesive means that I have to let the bonds mature on each plank before I start the next row.  Slow, but I am not in a hurry. 

With this triple chine design, the hull shape appears to be that of a nicely rounded hull form.  Very pleasing.  
First coat of paint

Second coat of paint

I had a quart of red on hand, so that is the color.  It will need three coats.  Then I get back to finishing the trim, the end decks, and interior.  I built two oars recently which will need varnish as well.

More to come as I find time.


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