Advice on Arch install plan

[Tbreptiles]

Plan is to mark and tape off the area.
Use a brad point bit initially in reverse to get through the gel coat.
Drill through glass (if there's core I will remove and reinforce with epoxy).
Countersink top of hole.
Butyl tape on feet of arch and backing plates. Backing plates are stainless - is butyl tape enough? Should I add some marine plywood or G10 for extra support?
Anything to add or subtract from this plan? Thanks.

[Tbreptiles]

Originally Posted by Tbreptiles

Plan is to mark and tape off the area.
Use a brad point bit initially in reverse to get through the gel coat.
Drill through glass (if there's core I will remove and reinforce with epoxy).
Countersink top of hole.
Butyl tape on feet of arch and backing plates. Backing plates are stainless - is butyl tape enough? Should I add some marine plywood or G10 for extra support?
Anything to add or subtract from this plan? Thanks.

- also I need a hole to run cables through the arch legs into the boat. _ Would you use a holesaw in reverse? Thanks.

[Coach Shoe]

Way too many questions come to mind to give a meaningful response. Attaching arch to WHAT? What structural strength will base have? What is intended use of arch? Any mechanical loads (traveler)? Any wind loads (solar panels)? Height of arch (big lever)? Lots to consider.

[Tbreptiles]

Attaching arch to WHAT?
coaming

What structural strength will base have?
thru 1/2 fore and 1/4 aft fiberglass to 5x5 1/2" backing plate

What is intended use of arch?
mount solar (2 panels)
radar
two gps antennaes
wind gen

Any mechanical loads (traveler)?
Davits for portland pudge (130#)

Height of arch (big lever)?
7'