Friday, February 29, 2008

Partner Box Installed

Installed the partner box in the deck today. All went very well and I'm excited to see how it works this summer.

The box was made of G10, which is a building material made of epoxy and cloth laminate. It's quite a bit stronger than regular fiberglass, although that property is a bit of overkill in this application. Took a couple hours to design and make the box, which was then assembled using west system epoxy and 404 adhesive filler.

To install we first located the proper location for the partners. Our old oval partner hole was 3/8" offset to port, which would translate to several inches at the mast tip. It was also longer than the class allowed opening. The new partner box is centered, and at the class legal fore/aft location. Not wanting to screw this up I had my dad to help as a second pair of eyes, and we checked everything 4 or 5 times. Centerline was established using the forestay fitting, and arcs from it were made at the gunwale, which were then used to establish a series of centerline marks along the deck. Once these all agreed, a chalk line was made down the center of the foredeck. The box had it's own centerline, which let us lay it out on center. While measuring, we found that the gunwale to center measurment was off by as much as 1/16" of an inch, in the area of the chainplates. This was probably due to lateral compression of the deck caused by the shroud loads. Our centerline seemed to be the more reliable measurement, and when installed the box measured as center to within 1/32" of the gunwale.

I cut the deck using one of my favorite tools, a Bosch jigsaw. I've used a couple other brands, and nothing comes close in terms of power or control when cutting. This is a newer model and the blade change mechanism is great, to eject blades you pull a lever and the blade pops out on spring action. This way you can launch hot blades at people that come to BS while you're trying to work. Very handy.

Cutting the deck was a bit nervewracking, but the box fit just fine and matched all the marks we made.

To install the box, I first sanded and cleaned all the surfaces, and then wet out all the bonded surfaces with neat epoxy. Laid on quite a bit of epoxy thickened with 404 adhesive filler, thinking it was better to scrape off excess than to have any voids. I set the box in place, and cleaned up the epoxy that squeezed out the sides. I used one of the west system mixing sticks, as they have a rounded end that lets you make great corner fillets, and the square end makes it easy to clean up leftover epoxy on finished surfaces. This mix is hard to sand, so the better you get the surface before it cures, the easier your finish prep is! I did the same on the underside, where the partner box extends below the deck for about a 1/4". I left the overlap here so I could make a nice clean fillet joint on the bottom. If the top fillet isn't good enough, I'll use 407 fairing filler to make a better one before painting.
Under deck view of partner box, fillet around edge

The yard is pretty damn cold, so I made a small heat tent using the boats 6mil plastic cover, a space heater and a 700w work light. The temps under the deck were in the 70's around the box, and above deck the temp was 65 on the surface. I kept this up for about 4 hrs to cure, in which time the epoxy was tack free. I'll return tomorrow and heat it up again to post cure it make sure, by keeping the temp as high as possible for the entire time I'm there.

Setup And Install Partner Box 5hrs (+2hrs cure time)


While sitting around watching epoxy cure, I decided to make and fit the mounting plate for 88's spin sheet ratchet blocks. Most of the time when racing the shields, you keep the spin sheets on the winch, but rarely use the handles. In order to make a faster trimming sheet-as well as to take some weight off the boat-I removed the spin sheet winches and made plans to install Harken 57mm Carbo Ratchet blocks. I kept the winch mounting pad, as I liked the angle it made to the cockpit, but needed a way to seal off the hole for the winch spindle, as well as a way to get the block up a bit higher in order to have a fair lead over the coaming. I used 1/4" HDPE (Starboard). I cut a half circle that matched the old winch base, and then cut the inside edge of the mounting plate on an angle to match the coaming. This makes the blocks high enough, means the sheet will clear the coaming, and seals off the old winch mounting holes. They fit well, but I'm going to put a nice routed edge on them before installing, which we'll do after painting. The blocks are positioned so that the spinnaker sheet can be cleanly led forward to the jib winch if we ever need winch power for heavy air trimming of the guy. We'll see how well this works out. I'm a pretty average sized guy, and the only time (as a spin trimmer) I ever needed the winch was in 20+kts.




Spin Sheet Ratchet Block Dry Fitted

Fabricate and Fit Ratchet Block Plates 2Hrs

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