Crossbeams Closed In

With the temperature now dropping below zero on a regular basis, temporary permission has been obtained to bring boat parts indoors for short periods so that the epoxy can fully cure. (In this weather, the resin will kick off and gel just fine, but the reaction slows down dramatically once it starts to solidify. Bringing the parts indoors, once there's no longer any risk of drips, solves the problem.)

Shown at left is the Starwind 860's aft port crossbeam, which has just received its top flange. The starboard crossbeam received a similar treatment a couple of weeks ago.

At the outboard end of each aft crossbeam, the electrical wiring for the outrigger bilge pumps, trolling motors and lights must join the wiring coming through the conduits from the main hull. This calls for a proper access hatch: one that's big enough to fit two hands and a tool, and still have enough room for you to see what you're doing. Failure to include such a hatch (and to clean up any sharp edges behind it) would incur the wrath of The Installer, whose addiction to Liquid Band-Aid really does not deserve further encouragement.

The front crossbeam pair is now also well underway. While it's unlikely that any readers of this blog will be building a Starwind 860 any time soon, some of the techniques are applicable elsewhere as well.

Cardboard templates are a wonderful thing. It's a lot easier and faster to fit complex shapes in-situ with scissors and a knife than it is to make many tiny adjustments to the final, wooden part.

The two cutouts in the web of the crossbeam, whose co-ordinates (like those of the crossbeam outline) are copied directly from the boat's CAD model, serve to align the strut attachment block.

The load path here should be relatively easy to visualize. Tension in the strut is transferred to the aluminum bushings, then along the loops of unidirectional fibreglass to the block cross-structure. From there, the load is transferred to the crossbeam webs, the cedar doublers, and to additional crescent-shaped cedar laminates that will go between the legs of the strut block. All of these are bonded together with the laminated flanges that close in the box beam, spreading the loads without any distinct hard spots.

Finally, here's the end clevis of the port crossbeam, which mates with a matching tenon on the starboard beam. Apart from a bit of fibreglass tape on the (still to be rounded off) seams, it's structurally complete, albeit rather lacking in the cosmetics department until we get around to fairing everything smooth.



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