Saturday, November 8, 2014

Be Sides...

Building the Side Panels of the BW

The side panels will be cut from 4-foot x 24-foot 9mm (3/8-inch) meranti.

Panel Selection

Since the BW will be finished bright (natural wood) I spent some time selecting which six 4x8 sheets will be used. I laid all ten sheets out, removed the ugly ones then tried to mate similar grain patterns and colors.
Panel selection

Scarphing and Gluing

Then, as usual, cut the scarphs. Even though the final side panels will be only 32 inches wide, I chose to scarph, glue and 'glass the full 48-inch width since I can use the excess 16 inches x 24 feet boards for other parts such as the side panel backers under the knees.

9mm sheet clamped for scarph cut



After dry fit-up of the joint and clamping the plywood sheets to the work surface so they cannot move, I placed a scrap block under one of the sheets to elevate the joint so I could access both faces of the joint for gluing.

Plywood sheet elevated for access. Pre-wet both faces of the joint
with un-thickened epoxy then apply thickened epoxy.


Then clamp them to squeeze a little thickened epoxy out everywhere to ensure that there are no voids in the joint.


Thickened epoxy oozing out.


After the excess epoxy is done oozing out, which can take
up to 30 minutes, remove the excess before it cures. That is a
lot easier than removing it after it cures.

When gluing the scarph joints, I kept the outside of the side panel up. That way, I could do my best to make the final scarph joint look nice since the finish will be bright. I can't access the other side of the scarph joint and it will probably be an ugly scarph joint. However, the ugly scarph joint will be on the inside of the boat and the inside of the boat will be so busy with knees, fuel tanks, helm, lockers, etc. that the ugly scarph joint will not be noticed.


'Glassing the Side Panels

I chose to glass the side panels now, while they are conveniently laying on my work surface. I 'glassed the full 48-inch width of one side but I 'glassed only 32 inches of the other side so that both sides of the side panels have 'glass set in epoxy. 

The extra 16-inch x 24-foot piece will have 'glass on one side only. The un-glassed side will be laminated so 'glass is not needed on both sides of the 16-inch x 24-foot piece .

Layout of 'glass using dry method. This side gets 'glass on
the full 48-inch width. The other side will get 'glass on only
32 inches of width. I use the full 50-inch width of the 'glass
and will cut the dross off after the epoxy cures. If you try to cut
the 'glass before applying epoxy, you'll get a bunch of annoying
stray 'glass strands in the epoxy.


Saturating the glass with un-thickened epoxy and being
vigilant about squeegeeing the epoxy on thin so the
'glass does not float off of the plywood.

After the epoxy cures I will remove the dross and fill the weave. 

After the epoxy cures, I use a utility knife to cut away the dross. That leaves a really sharp serrated knife edge in the 'glass/epoxy that needs to be sanded to avoid cutting yourself. I learned this the hard way long ago.

Also, do not fill the weave until after the first epoxy layer is cured. If you try to fill the weave before the first epoxy layer is cured, you will float the 'glass off of the plywood leaving ugly waves in the 
finished 'glass.



While using the overhead pulley system to flop the
4-foot by 24-foot panel, I took this photo to demonstrate
the resilience of the meranti and the strength of the scarph.
The entire panel is being held up by a single lift point at the scarph joint.

Filling the Weave

After the epoxy has cured the weave of the fiberglass is still providing relief to the surface. After filling the weave with unthickened epoxy, the weave is invisble and the surface looks like varnished natural wood.
Before filling the weave, I placed boards to mark the 32-inch
portion of the panel that will become the final side panel. There
is no need to fill the weave in the remaining 16 inches that will
end up in an unseen location.

Pour un-thickened epoxy on the surface, roughly spread it with
a squeegee, fine spread it and tip with a foam brush. Use small
batches of epoxy so it does not start to cure before tipping.


Filling the weave on the side that received fiberglass on the
32-inch portion only.


Weave filled

Let the weave-filling epoxy cure then remove the unused
16-inch width of fiberglass.



Flopping Panels

Working alone, I rigged overhead pulleys and ropes to help with lifting. Here is a sequence of photos showing flopping a 4-foot by 24-foot panel.







Cutting the Side Panels

Weave is filled and it is time to cut the side panels to the plan dimensions.

The factory edges of the plywood sheets were not aligned perfectly since I elected to align the sheets as needed for nice looking scarph joints. So I need a straight edge for the baseline.

I struck a chalk line, set a straight edge and cut a baseline.

Measure off of the baseline and cut the side panel to
its final 32-inch width.

Since this boat is a prototype, I need the stations to be permanently
marked in order to record adjustments to the plans, if needed.
So, the stations are permanently marked on the inside of one panel.


Stations and offsets for the BW side panels



Lay out offsets at each station according to the plans and use
a supple batten to draw a fair curve.

Lay the panels together, in mirror image (inside out), and cut the
curve with a jig saw. The curve will be sanded fair later.

Separate the panels and cut a 20° bevel on the bottom
edge of the panel (chine).

While the panels are separate, route a curve on the inside
 edge of the stem. Lay the panels together in their final
configuration, (inside in, pretty side out). Then the stem
is drilled and loosely stitched. The stitches are 16 gauge steel
coated with paste wax so epoxy will not stick to the stitches.

While the side panels are still atop each other,
drill the stitch holes for future stitching
at the chine.
 Store the Side Panels


Bottom and side panels suspended from the ceiling.