Through the Dead of Winter

Man, what a trip! With many tedious nights of hand numbing work behind us, our most recent phase of project Mako is complete. We feel excitement growing with the increasing daylight and sprouts peaking up from the ground. We've turned a major corner in our workshop, shaking off the dead of winter. We're ready to add new growth to this boat.
Our goals for this stage:

Remove the old stringers

Peel and grind away all weak laminate

Scour off any trace of foam and contaminants

First, removing the old stringers:
We sampled several different tools to get the job done, beginning with the cut off wheel. This tool works great for hogging through fiberglass. But the deadrise made sharp angles which the tool couldn't quite access. Not the best option for this job.

We opted for the teeth chattering muscle of the sabre saw next to zip the stringers off. It cut quickly, but the long range of motion risked punching through the hull with one slip, especially on the upward angle of the deadrise. We removed a few stringers with this reciprocating saw, but it left behind high nubs with the remaining core still firmly bedded in place. It still required alot of cleanup work.

The best tool for this job - the multimaster. We hooked on the high speed steel saw blade. While it cut through laminate and plywood slower, the controlled flush cut actually saved more time overall. In fact, once the fiberglass encapsulating the plywood core was cut, we were able to rock and knock the stringer out. We still needed to cut and grind all traces of the stringer away, but there was much less cleanup using the multimaster.










The stringers were surprisingly still semi-solid overall, though soaking wet through and through. That's some good wood to stand up 30+ years. We've removed a good deal of dead weight here. The cracked sections of fiberglass were the worst, the core a splintered mush as expected.

Our next step was to get down to the good stuff. Bonding new fiberglass to a delaminated layer would only peel away under stress. We needed to remove and grind away any suspect areas. Poorly bonded top layers have an opaqueness where the bond separates. This can happen to bare fiberglass over time from constant water exposure, in this case from the saturated foam. Much of the top layer of woven roving needed removal to expose good bonding surface.

We set in, grinding and cutting away the nubby remains of the stringers. We could have saved this step, because an exploratory peel of some delaminated woven roving became a wholesale removal of the top layer. TJ wedged the pry-bar under the top layer of woven roving in exposed stringer bed. It peeled off like dead skin. Peeling it away revealed the exact composition of the layup, or "schedule." Below the woven roving was a chopped strand mat layer. Below that was the first base layer of fiberglass in the mold. The peel brought most of the chopped strand mat with it. What remains is now a good pinkish hue of solid fiberglass, an excellent bonding surface for our next step.





These samples of Prisma stringers hint towards what comes next.

Before

After

Before

After

The hull now flexes under foot enough to make us squeamish. We have to mind our step. We will address this next before adding in new stringers.

Many grueling hours later we feel good about the results. We're excited to begin building up the inside of this hull.