Winds of good fortune blew in this week bearing a shipment from Florida. TJ and I sifted through the boxes marked with the Prisma emblem like kids in a candy store. These boxes contain the new skin and bones for the Mako-
"Check out these stringers," (eight 4' sections.)
"Here's hull the smaller hull stiffeners with the carbon cloth top," (four 4' sections.)
"Two beefy looking 3" panels, possibly for knees." And a boatload of cloth. This will be be a stout little boat.
The Fiberglass included a roll of Quadraxial. The specs on the cloth:
- 36 oz per square yard
- 4 layers of alternating weave (0°/90°/±45°)
- non-woven polyester Trevira™ backing
We're excited about the strength of this quadrax though we've yet to work with it. It's thick! 36 ounces per yard means fast strength build with a fraction of the labor. Quad means there are 4 layers of fibers, each oriented in opposing directions. It adds stability in all directions, (0°, 90°, +45°, -45°) and the polyester Trevira (aka T-mat) backing conforms to the hull shape and prevents peeling away. Once T-mat is bonded to a hull, there is no risk of delam. Only a grinder will take this stuff off.
We started with the complex curves of the keel. We rolled it out and cut it to length.
We cut a second strip to size it up. We're looking for a 3-5" overlap on the sides of each strip.
This center strip spans from just under the stem up forward back to the transom.
We tackled the most complex run first, the keel. The gradual inward and upward sweep of the bow (deadrise and shear), forced the cloth to buckle. To tame it, we split the strip where the curve steepens, about 5 feet or so to the end. We criss-crossed theses strips so each lay flush.
The surface has already been sanded, so no prep is needed. We're ready to wet out. Next choice, Polyester or Epoxy resins. Either will work, but several reasons shouted epoxy. First thought is the bond; we used epoxy on the transom and chine fillets. Polyester makes a strong mechanical bond to itself, but doesn't play well with epoxy. Epoxy on the other hand bonds to most surfaces. Secondly, the smell indoors. Our workshop here at Jamestown Distributors abuts retail, warehouse and office space. Polyester gives off an overpowering styrene smell. We're indoors and our coworkers would not be happy. Epoxy smell is mild in comparison. Lastly, performance; epoxy results in better strength and stiffness per weight. If you're choosing, either works; more economical polyester will bond to old polyester hulls- so long as no Poly over Epoxy, it's fine the other way around.
The resin of choice? Epoxy dujour- West System 105 since we have an abundance of it on hand. A dedicated laminating resin like MAS low viscosity or System Three clear coat is nice, it wets out easier and quicker, especially on thick cloth applications. We tried standard 105 resin and had no trouble in the 50-60° workshop. If you're working in hot temps or in large scale the quick wetout is great, but moderate temps gave us a long window and no problems.
Lots of mixing! Polyester can be mixed in bigger batches, but because epoxy is exothermic, the batches have to be kept small. Big epoxy batches cook quick. TJ volunteered as designated mixer and I climbed in, Tyveked to the max. A helpful tip for large layups is taping off the sleeve cuffs or better yet, double up with some tyvek sleeves over the coveralls. Otherwise your wrists pop out with every reach. Also layer on the gloves. You can peel them off as needed.
We used West System 105 with 206 slow hardener to extend our working time. We grabbed a foam roller and roller tray, and rolled out unthickened epoxy underneath.
We dropped the cloth over and wet out til no dry spots remained. The longest part of the whole process? Bubble busting the entire run, a span from the stem on the bow to a few inches up the transom. We chased any bubbles out the sides with laminating rollers and squeegees.
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