on the 30 lbs boat....
the project began with a 30 lb goal based on some blogs on the guillemot kayak forum.
the project then moved to research related to weight vs strength trade-offs. Pages 36 thru 46 of Nick Schade's "The Strip-Built Sea Kayak" provided the basic facts and figures of different boat laminate recipes and weight and strength projections. in this section are tables of various thicknesses of core material coated by various weights of cloth and finished weight of a reference boat. this section established that a 30 lb boat was acheivable if you use 3/16 core of western red cedar and 4 oz cloth (and careful epoxy work). (note...you really can't find a recipe for this boat that can be executed sub 30 lbs with a 1/4 inch core) i also started several threads on the guillemot site to confirm with other builders that what i wanted to do was reasonable and not going to create a boat that was fragile.
when that all checked out...it was really then about execution and careful work and paying attention to the weight implication of each step/component.
the first trick was getting 3/16 strips. in the end, i acquired 1/4 western red cedar bead/cove strips from CLC and ran them through a thickness planer to take them down to 3/16. a couple wasted strips while i sorted out how to use the thickness planer....but after a bit i was comfortable with the tool and the 'strip conversion' process was pretty straight-forward.
probably most important element after that was tight workmanship with the strips (no gaps) and paying extra attention to gettng fair surfaces so that you did not try to correct hollows or voids with epoxy....which is the real enemy in managing weight. i also used techniques like seal coats to minimize epoxy absorption by the core.
other weight saving techniques that accumulated some good savings or gave some superior strength included:
- kelar seam tape
- s-glass was substituted for e-glass improving strength for same weight.
- exclusive use of cedar core and not using any plywood (which is heavy)
- a rigging system that does not use bolts/nuts/washers (see redfish kayaks websites for a description of 'softpadeyes')
- using micro-balloon putty for non-structural fillets which is light compared to a comparable wood flour-based fillet
last night i put all the parts in the cockpit and weighed it again and i am at 29.8 lbs (seat, footbraces, seat back and all the rigging bits). i also realize if i wanted to save some weight relative to my current approach, i can execute closer to 26/27 lbs.
to do that....
- eliminate retractable skeg (1 lbs)
- use foam blocks for foot brace and not Keepers adjustable foot braces (1 lbs)
- pad out the cockpit with foam and eliminate solid cheek plates ( 6 oz)
- a more elemental rigging layout relative to my current plan (8 oz)
at the end of the day, the boat's weight is the sum of its parts....all the data is relatively available to sort out the approach.
fwiw....it feels really sweet and easy to pick up a 30 lbs boat :)
