How to fill-in side by side voids in load bearing area?

Hello all - first post here. After much research with no clear answers, I'm hoping to gain the members knowledge and experience on the below.

How can the pictured rope channel void and port foot switch hole be best filled back in when they are only 1-1/2" (38mm) apart, thereby preventing the standard bevel and fibreglass patches layup approach?

This is part of a new windlass install, with an addition of a large centre cleat over the top of the old rope channel void. The cleat will need to handle significant loads.
- deck is solid polyester laminate and 3/8" (9.5mm) thick
- a large plinth and under deck load bearing pad will later be installed, covering the filled in rope channel void and switch hole
- I cut out/saved the rope channel walls, which are 5/16” (8mm) thick, there is enough left over to make a core plug for the switch hole (if recommended).

 

Whilst it is probably clear to you what the plan is here, we are all "new" to the project, but it does seem the idea would be to make a wider excision, and eliminate the hole that is 1 1/2 " from the channel, if that hole isn't required any longer. Then glass in the new piece, and use a ply backing to spread the load around.

 

My approach

Mostly ignore the holes which are to remain. Do mark their location!

Bevel and fill the go away holes.
Redrill the holes which needed to stay
Paint

 

Alternatively, leave everything there currently, and if this is a flat area, epoxy glue on to it a prepared panel made from GRP, GRP sandwich, Coosaboard etc to the desired strength, that spans the whole area. Then cut holes again from the inside. Or if it has just a gentle, simple curve, it should be possible to conform to it with enough clamps, while it sets up.

 

Thanks for the idea of laying up the above deck area first. How would you then go about eliminating/filling-in the rope channel void and switch hole.
The area is curved. The top of the deck is a max of 1-1/2" lower on the port side and a max of 1/2" on the starboard side at the borders of the expected footprint of the to be installed plinth.

To clarify for readers, I am trying to determine how to "fill-in" the port switch hole and void of the rope channel, while restoring the same properties as the solid deck laminate to avoid failures later when loaded. A plinth will then be installed above deck and a load bearing backing plate on the deck underside for a windlass and large load bearing centre cleat install.
Two marine pros looked at this separately and both stated that a minimum of a 12:1 bevel must be done to soundly fill in the rope channel and switch hole - both were stumped with it not being possible to apply a bevel, due to the deck thickness of 3/8" (9.5mm) and the holes being only 1-1/2" (38mm) apart.

 

On Mr 'E's idea of laying up a span across the whole above deck area, would this in effect create a uniform deck strength and eliminate any problems with changes in weakness from how the rope channel void and port switch are later filled?

 

Yes, cut the whole section out until you get to an area where there is space for the tapering, then redrill the holes you want to keep into the new laminate. With propper tapering of the patch, the deck will be as strong as before.

 

BoatworksToday has a few videos on patching holes.

 

Could the switch hole be laminated first using the biggest bevel possible, then the rope channel void patched afterwards with the largest bevel possible? This would mean that around half of the repaired switch hole would be grinded/beveled into. Would this cause the remaining half of the switch hole layers to separate? Has anyone tried this before?
There is also the open end of the forward section of the rope channel to address?

 

It is absolutely possible. Overlapping repairs is no problem at all. I've done it thousands of times before.

This particular project could almost be done with paper-mache. The current hole pattern reduces the structural integrity by 70-80% (imo). The planned hole pattern will reduce the structural integrity by 70-80% (imo). A thin cosmetic sheet obscuring the unwanted holes would be quick and easy with no significant loss of structure.