Installment 29 of Mako Restoration
Day two of the Prisma visit, and we're ready to finish up - this post we're installing the stringers. The previous day we completed the stiffener installation, and it cured hard by the time we returned the next morning.
Those stiffeners installed fairly easy since it lay higher in the hull on the flats. Installing the stringers is more challenging; the stringers are closer to the keel, and span complex angles and turns up forward. Getting a flush fit can be a head scratcher. But we have a plan of attack. 
Having Scott and Mike from Prisma onboard for this stage was an incredible boost. Their experience and expertise guided us easily through the process without sweating insignificant details. Together we dry fit the stringers to the hull.
The upsweep in the bow was problematic; it caused the stringers to bridge. For a perfect fit we'd need to shave the underside through trial and error, or trowel out some thickened bedding compound. Either option would eat up valuable time. But Scott reminded us the load is actually carried through the fiberglass not the foam. The foam core simply secures the fiberlass laminate shape from deflection, thus giving it exponentially more strength. A simple relief wedge cut out of each stringer gave a sufficient fit. It worked for this boat because the deck floats above the stringers not on them. The relief cut hinged the stringer with the bend to achieve adequate hull contact (though not perfectly flush.) We laid it out and everything looked shipshape. Mike hopped in the boat and TJ and I suited up to work the laminating table.
We're again using epoxy to glass in the stringers since the earlier stages were completed with epoxy also. (Polyester resin is the common go-to for this, but should only be used when bonding to a polyester based hull.) With temps in the 60° range, we're going with 105/206 slow mix to get the desirable work time.
We passed the first sections into Mike and he set them in the hull. Notice the index marks on the transom for alignment. Mike kept a tape measure onhand to assure alignment.
This job is best done with several sets of hands. We wet out on the table, making sure the spun polyester backing (aka Trevira™ or Duraspun™) is completely saturated and the quadraxial cloth has a translucent soak of epoxy.
We fed Mike a steady supply of epoxy so he could complete the wet out. He kept a laminating roller and chip brush on-hand, along with a healthy layer of gloves to peel away as needed.
Where the stringers butt together, Mike covered the joint with 6" wide strips of quadraxial cloth.
Wood strapping and some old fashioned gravity helped tack these stringers in place while curing. Be sure to add a poly sheeting barrier to keep the wood from bonding to the stingers. We sat heavy 5 gallon pails atop the wood for pressure.
Where the deadrise (V) is steep, Mike drilled some drywall screws through the spacing planks into the stringer to keep them from sliding down.
With all the stringers set in and wet out, Mike stepped out of the Mako and hung the "do not disturb" as we stepped away. A few tie in strips to the transom will finish the job up. (included in next post)
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