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Cabin Top Winch
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In June 2000 I mounted this Lewmar #8 winch on the cabin top just aft of the coaming on the port side. I intend to run some of the halyards to this winch as well as reefing lines and the asymmetric spinnaker downhaul.

I mounted the winch on a base made from West System epoxy. I drilled five 3/8" holes through the outer skin only and removed the balsa core around the holes. I used a series of Allen keys (with chisel cuts in the ends) chucked in the drill to chew away the balsa core around the holes. I cut a radius of about 1-1/4" and the holes were joined to form one large cavity with a balsa spot in the middle. I filled the cavity with West epoxy with a high density additive (404). I poured the epoxy into the inboard holes (they were higher) and it flowed into the entire cavity. Then I took the winch base and set the 1/4-20 bolts on it with washer and nuts so it stood on them like legs. I waxed the bolts and placed it on the deck with the bolts in the holes so the epoxy would set around them. I ran the spin halyard to the dock and pulled the boat over to a 5 degree heel to level the mounting spot and let the epoxy set. After it set I unscrewed the bolts. I molded a riser pad for the cabin top winch mount out of epoxy with 404 high density filler and white pigment. I mixed the epoxy to a thick peanut butter consistency and spread a 3/8" thick patch on the winch mounting spot. I waxed the winch bottom and mounting bolts and bolted it down with 3/4" bolts. I tied a halyard to a winch handle to pull the winch up a bit so it didn't squeeze out all the epoxy. I backed the screws a bit so they were not bottomed out in the holes. I cleaned up the edges as best I could and let it set. I had taped down masking around the winch.

The finished mount seems very strong. I put a fair amount of tension on the halyard when pulling up on the winch as the epoxy set. I expect it's a bit stronger with the pad and the real load on the winch will be shear. I used this mounting method based on reccomendations in the West System book "Fiberglass Boat Repair & Maintenance" (cat no 002-550). In addition to that book I looked up the holding power of fasteners in fiberglass mat in "Marine Design Manual for Fiberglass Reinforced Plastics" by Gibbs & Cox, Inc , (1960). In it there are many tables on the holding strength of various fasteners in various fiberglass laminates. For a 1/4-20 fastener in 5/8" thick mat with polyester resin the axial load capacity (along the axis of the bolt) is 2300 lbs, 2,700 lbs in 10oz cloth. The shear load capacity is 1300 lbs which I think is the strength of the bolt. I figure West System epoxy with high strength filler is at least as strong as mat. I don't know how reliable the figures in the book are but I think they are pretty good. If they are high by 2X the winch mount is still strong enough to lift the boat.

I also attached a Ronstan 5010 cam cleat at the aft edge of the cabin top to take the line coming off the winch. I drilled oversized holes, removed balsa with the Allen key in the drill and filled with epoxy/404 filler. I made a canted pad from the same thickened epoxy that I used on the winch pad. I set the cam cleat down with waxed screws in the epoxy.

This photo shows the holes cut in the cabin top. They are about 1/2" and I removed the balsa around them making one donut shaped cavity to fill.
This is the winch base with the mounting bolts fastened to it for setting in the epoxy. Mounting the bolts like this insures proper alignment in the epoxy. I waxed the bolts, filled the cavity with epoxy, then placed the winch in standing on the bolts. These bolts were longer then the ones used to mount the winch.
This shot shows the setup after the epoxy set. I waxed the entire winch base to keep any stray bits of epoxy from bonding. That turned out to be a good idea. The bolts backed right out. I ground down the excess epoxy and roughed up the surface to bond the epoxy pad. I made the pad with epoxy thickened with 404 filler and white pigment. It's about 3/8" high.
This shows the basically finished winch mount (before assembling winch) and the cam cleat I mounted at the aft end of the cabin top. I mounted the cleat in the same manner as the winch but angled it back on an epoxy pad.
Here's the finished installation. Eventually I'll run some halyards aft to a set of sheet stoppers just forward of the winch. I'll keep the cam cleat for a backup and for use with the asymmetric spinnaker downhaul.

Parts For Cabin Top Winch mounting
Lewmar #8 winch
5 1/2-20 1" flat head screws
West System epoxy with 205 hardener
West System high density filler #404
West System white pigment
Ronstan medium cam cleat