Integrity exhibit B

It’s the day before launch, or at least the day before the launch party. Putting a final coart of paint on the hulls today and perhaps a second injection on the decks. There’s a slew of parts arriving via UPS, including (theoretically) the jib from Whirlwind, just about 3 weeks late.

Work in progress images from a couple of weeks back, examples of problems solved towards getting a $400 Hobie Cat ready for the big lake. In hindsight, full documentation of the restoration would have been great, but getting the boat ready was my focus.

Simple patches and more trouble

The damaged area (blister, crack, impact) is exposed (darkish middle) along with some surrounding solid structure.  A patch of biaxial glass is cut to overlap onto the existing structure, then the patch and the solid structure are wet out with catalyzed resin. Some 406 ‘mayonnaise’ is applied to the structure, followed by the patch and finally a sheet of wax paper (brown) to facilitate removal of air bubbles and excess resin. The wax paper is removed and voila! Note the inner oval of biaxial glass doesn’t entirely cover the exposed structure, just enough to bridge the damage.
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First bow patch after the wax paper was removed. New glass is flush with the gelcoat as it overlaps the existing glass. The compound curve was a little tough to match with one layer of glass, thus we got a tiny air gap at the aft end of the patch that had to be reopened. There was plenty of practice doing bow patches.
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Late in the game, Patrick found other issues of concern on the port hull bow. Red crayon marks a suspicious crack, which turns out to be a through hull repair. Here it is opened up. Multiple layers of biaxial glass built up the curve, followed by an icing of 406 ‘peanut butter’
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Another late in the game discovery – rippling hull. We had extensively assessed the hull weeks back, but after several simple repairs our eyes became tuned in and we could spot more subtle clues. An area of weak glass and delamination, just below the delaminated deck area. Could this have been caused by stress from the weakened deck? Deck delamination ignored can eventually result in the hull snapping in half.
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A through hull repair, inner and outer skin breached

To fabricate a backing plate to heal the port breach, we needed to match the curve of the hull for a close fit. The hull provided a handy mold. First plastic is laid over a big swath of hull and stretched tight with tape. Wax paper was laid on the plastic and the hull was rotated to bring the surface closer to horizontal. Then biaxial glass was cut and wet out. Gravity insures the patches conform to the shape of the hull. We built two pieces because though the curve of the inner skin closely matches the outer skin, the inner has a ridge where the foam meets the keel. Rather than try to rig something super fancy to take the ridge into account, we just left a gap that could be bonded later.
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Here the two plates are placed inside the hull. Of course, all surfaces were sanded and cleaned with acetone first, then wetted out and 406 mayonnaise applied. Fishing line tied to the backing plates pulls them against the inner hull. Our innovation was to include wooden blocks so that the line is pulled at nearly right angles to the hull rather than to the sides. This really locks the patch in place until it cures. From the other side, note the fishing line almost wrapping around the hull. That kept tension on the line while decreasing load on the tape. The fishing line was as taught as guitar strings.
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More patches and deck injections with guest appearance.

The rudder breach was big enough for a light bulb, but not the right shape for a backing plate patch. The hole had to be expanded into a more elliptical shape so the backing plate could be slipped through. We patched most everything in two days of frenzied work.
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The injection map. The outside fiberglass skin has separated from the foam core creating a void or empty space between them, compromising strength. This can cause the hull to break in half in high winds. A pattern of holes are drilled Holes are drilled and catalyzed resin is injected to fill the voids. Unfortunately, about 30% of the holes I drilled went through the outer and inner fiberglass, both because I was a little careless and the inner skin was somewhat compromised. I drilled slightly larger inspection holes to check for cracks in the inner skin. Finding no significant cracks, I used 404 peanut butter to seal off all the inner holes in preparation for injection.
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Injecting resin into one hole forces resin out the adjacent holes. Moving from low to high points on the grid allows air to escape, theoretically filling the void. Injection complete. Extra resin has oozed out over the tape. The tape kept the cured resin from bonding to surface of the hull. James Kudlak, local windsurfing legend, stops by to survey the progress.
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