Question about backing plate on winches

[Vincent]

Quick question: I am replacing my primary winches in the cockpit. Cape Dory used plywood backing with what appears to be foam looking stuff. The edges of this stuff crumbles but I had to use a hammer and wood chisel to get some of this stuff out of the way. I was trying to get access to the lock nuts so I could back the machine screws out. Anybody know what this stuff is. I am tempted to leave it and the plywood in place and just drill new holes for the bigger self tailing winches. This stuff almost needs a jackhammer to remove, and the area if difficult to get good access and leverage.
Anyone have comments or ideas?

[s2sailorlis]

If it worked well for all these years, I’d drill and fill with what’s already there, and use fender washers to finish it off. Those puny washers are way undersized, and stainless fender washers are cheap.

This assumes the deck core isn’t compromised, etc...

[robwm]

Word of caution about "fender washers" they are prone to cupping …. If using, might want to use a smaller second washer against the fender washer itself, or, get thicker standard washers to begin with. Learned about this the hard way when I redid winches on my prior boat.

[tjr818]

If you use fender washers, be sure to use the thicker type or back them up with a standard washer.
Here is a link to my go to source:
https://www.boltdepot.com/Fender_washer ... .aspx?nv=l

[John Stone]

Vince
It’s hard to tell from the photo. But looking closely right next to the nuts it look like a fiberglass mash used as both an adhesive and filler. Very hard stuff had somenon my boat. Very hard to remove.

There may be a wood core there to. Or there may be an aluminum plate buried in there. Pull the bolts out and see. Under load the bolts will be in sheer vice compression so I doubt there will be a problem but it’s not the right way to do it. At a minimum you need larger washers. We’re it me, I would use 1/4” aluminum for a backing plate or better yet 1/4”’ G10. I’d get longer bolts to accommodate the thicker backing plate. In SS they won’t be expensive. If you are going to the expense of replacing the winches you are already dropping a couple boat units into the project. What’s another $30-$40.