There are backing plates and there are backing plates done right. There is a backing plate under this mount:
The backing plate needs to match its job, and obviously this one does not. Water
is also getting in through the bolt holes and/or the gel coat cracks and the core is wet a good distance from this mount.
My backing plate philosophy is more along the lines of DRSanbo, however for highly stressed deck hardware
, I start with marine plywood
epoxied to the underside of the deck. This provides a large, flat bearing surface that really spreads out the load, and the epoxy
conforms to the underside of the deck perfectly so there are no hard spots.
I also (am in the process of) drill out an oversize hole and fill it with epoxy
to increase strength and prevent the two layers of fiberglass from flexing independently, which could break the sealant's bond between the fastener and deck. Also, with the epoxy plug
does get in, it comes into the cabin
instead of getting into the core. That is what my recent thread about drilling parallel holes was about - getting the holes drilled parallel so the bolt holes like up with the backing plates.
Overkill? Not on a cruising boat.
backing plates are ok for dry areas. Here is a badly corroded aluminum backing plate in the chain locker for a cleat. BTW, cosmetically, this is a beautiful boat.
Also, note the stress cracks in the fiberglass at the three bolts for the locker door hinge - a backing plate is in order here!
DRSanbo - who is drilling the holes through that stainless?