Laying Down the Heavy

By our next shop session the center strip of Quadrax cured rock hard. Just stepping in the hull was noticeably stiffer. This is the way to go- quick and easy strength. Time to add some more. We're going to split this stage in two, glass the starboard side first, let it cure, then glass the port side after. Otherwise we'll be lying in wet resin, a very stick proposition! In total we estimate covering 80" x 180" of hull area .

The Quadrax is on a 15" wide roll, so we dry fit three strips in advance. For the outside run we used a roll of masking paper to make the template, simply following the chine with a sharpie.




Once the quadrax was cut, we sized it and it looks spot on.


We cut it so the fabric just curled into the chine but not up the sides. We'll come back after with some 6" wide tape to finish tying in that angle.

The cloth runs all the way aft to about 2 inches up the transom.

With everything in order, we began the mixing. Again, we went to West 105 and 206 slow.



Starting with the highest strip, we spread neat epoxy on the hull with chip brushes and roller then aligned the fabric over. We poured the resin and squeeged it out with spreader.




As the fabric wet out we worked all the air out with laminating rollers. 15" wide strips make bubble chasing manageable. We walked our way towards the keel with each layer. Keeping the cloth flush on the sharply angled bow was tricky. The best solution we found was to fold the cloth back on itself, back wet it and stick it like a postage stamp to the steep bow. We finished the wetout spreading more resin with a chip brush on top and worked out any air with gloved hands. All strips had at least a 3 inch overlap.

We're half way there.

The Buildup

Supplies! Supplies!
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.

The Rising Tide

Demolition phase 2 is complete. The Mako interior lays bare and scoured clean like fresh sand exposed at low tide. She's ready, bow out, eagerly awaiting the gurgling lift of incoming tide. This build is rushing in on the visible horizon. Next step, shore up the hull with a new schedule of fiberglass.

In stripping away the detritus, we've weakened this hull considerably. Our first order of business, stiffen her back. We want a rock solid base layer, so we consulted Prisma Composite Preforms, experts in composite construction. They've advised a new layup which will form the foundation for their preform stringers and stiffeners. Modern designs achieve a lightweight, stiff hull via a cored laminate construction. But this vintage Mako was straight fiberglass without core. Prisma engineers devised an improved schedule of fiberglass that is stiffer than original. The first application will be Quadraxial cloth, followed by 24 oz 0°x90° cloth which Prisma distributes. The Quadraxial cloth is 4 layers in one cloth, each weave alternates a different direction (0°, +45°, -45°, 90°). We'll elaborate more on this in the next post.


We had yet to get our hands on the quadrax but expected a heavy cloth where it's drapability is stiff like biax. Heavy cloth poses a challenge for hand layup - air pockets. Small voids were throughout the original build. Grinding off the old roving revealed loads of air pockets, particularly at the hard turn on the chines. In a morning coffee gam session TJ and I leaned over the transom and threw out some problem solving ideas- what if we smooth the sharp transitions with a fillet. The fillet will ease the bend in the cloth maximizing the bond.

We mixed West 105 /205 with a hefty dose of milled glass filler and filled the V in the bow. This mixture needed something more to prevent sagging, so we added enough 407 low density filler to make it stay put on the sloped sides. We also spot patched some voids in the stern with the remainder of the batch.

The gray in the bow is the milled glass mix, the shiny brown is the same mix with 407 added. Once cured we passed the sander over it with some 120 grit and faired this to a fillet-like easy curve.

This hull is clean and ready for the big show. Time to dress her up with some Quadrax!

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.

Better Limber Holes

This article from Professional BoatBuilder has excellent ideas on designing bulletproof stringers and bulkheads that will last. It talks about the issue of limber holes, those passages through bulkheads and structural components to drain water to the lowest part of the bilge. "The Humble Limber Hole" by Bruce Pfund TJ and I plan to take a few pages from Bruce's book on the new stringers we'll be installing. Check it out.

Stringer Appeal

Installment XX in the chronicles of a Mako classic restoration

We are now ready to make some progress with stringers (longitudinal reinforcing beams on the hull.) The original stringers were marine plywood covered in a heavy fiberglass woven roving cloth and wet out with polyester resin. Holes called "limber holes" were cut to allow water to drain to the bilge. These vintage limber holes are a horror show. A hole saw cut through the beam left exposed wood core. Water migrated in and rotted these areas. The rotten core shows black through the fiberglass. Notice the cracked areas.

These beams bear the brunt of force when pounding through waves. Hard spots and rotted core spell failure.


To remedy this, our task is to grind these stringers off and replace with new. Rotten core has minimal strength and must be extracted. Spot repair and/or sistering in stringers supports is the easiest route with least time and expense. We're going for the gold- grind the old stringers flush, then replace with foam core stringers. We chose these pre-fabricated stringers by Prisma. Prisma Composite Preforms come in complete sections, ready to wet out. The fiberglass fabric is already bonded to the foam. Just bed in place then wet out.







To spec out the stringers, we carefully measured and snapped extensive pictures of the current hull stringers. Measurements should include:

• angle of deadrise (angle of the hull to perpendicular)
• length of each stringer
• depth of each stringer
  

We then emailed this info on to the folks at Prisma for technical consultation.


Without stringers, this boat will be loosey goosey. One concern with the upcoming phase will be to maintain hull shape. We must support the hull prior to removing the stringers to minimize distortion. Temporary braces across the gunwales and supports under the hull should maintain hull shape as best possible.

Commonly decks rest directly on hull stringers. Notice this boat has separate reinforcements for the deck, which floats above the stringers. (see 2 remaining nubs in middle) We have the option to replicate this or just mount directly on stringers.

This perspective shows the taper of stringers meeting the rise in the bow.

Thanks for joining us, and please check back for more.