Thursday, August 6, 2009

Carbon Booms - Outhaul Block Backing Plate

I originally rigged the booms without a backing plate on the outhaul block. After talking with several people about this, it was evident that a G10 backing plate is desirable to distribute the load and keep the block from ripping out.

To do this, I cut a rectangle piece of 1/4 inch G10 slightly larger than the size of the block's cover plate. I drilled the through-holes on the drill press and then sanded the piece to the inside profile of the boom. I then sanded the tube in preparation for bonding. With the boom upside down, the piece was bonded in with fillets using epoxy and colloidal silica. I used some fasteners sprayed with Mclube to line the plate up with the existing holes. After the epoxy had cured I then cut the through hole using the existing hole in the section as a template. The fitting was then fastened using machine screws and nylon lock nuts. This fitting is now very strong.

I do not have a picture of the completed outhaul block, but I did quickly draw up a schematic of the internal rigging. One thing you will notice is that with this setup for the flattener, it puts a lot of added load on the outhaul block when engaged. A good amount of the leach/vang tension is transfered to the outhaul block when the flattener is pulled forward. This is one of the main reasons why I think a G10 plate is desireable.

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