30' cruising catamaran repair log

Somebody asked how much this weighed and how it compared to a store bought aluminum boom. I don't know what the other booms weigh of equal size (13') and strength - possible about the same or maybe even a bit lighter, but this will be ok. At this point, I weighed it with the sheave boxes (minus sheaves) and it was at 46 lbs. With the rest of the glass and carbon and whatnot, it'll be over 50 lbs. I'll weigh it again when all finished, perhaps.

Here's a few pictures of getting the last of the full length carbon fiber and fiberglass on the boom, using a vacuum bag. Was a bit worried about vacuum bagging the whole boom in a bag as I wondered if I could crush it. I tested it first with a leaky bag - not full vacuum, and slowly closed up the leaks. It seems pretty stout, so went with it. I just use a shop vac so not sure I have the strongest vacuum anyway.

But it still laid down the fiber pretty good and sucked some excess epoxy out of the mix. I did have a few wrinkles in the carbon - not sure what I do wrong there as it was nice and smooth when I put down the peel ply. Must have been as the bag sucked up, it pulled a bit on the carbon as it sough equilibrium.

 

And here I am getting ready to set the sheave boxes. I put some Saranwrap (plastic kitchen wrap) around the base, then added some thickened epoxy under the boxes and pushed them into place, hoping the epoxy will squeeze out and create a nice little socket for the bases. The boxes will be removeable (I hope) so I want a good base that the boxes will be screwed through - the epoxy should help resist some shear force on the screws. The boxes will bear against the boom where they exit, to help resist force there, and the sheaves will be pinned through the sides of the boom to further help hold them in place. I'll reinforce the sides of the boom a bit where the tops of boxes bear against, and where the pin exits the sides.

 

Fairing and rails for the boom. Using pvc conduit for rails, to be wrapped in fiberglass and insert dowels into them for stiffness. Had to make my own dowels as store-bought ones were too small in diameter.