Mounting Pedestal Seats into the cored balsawood floor

[Knotcute]

I would like to add a couple pedestal style seats to my fishing area for those long days of trolling. What recommendations would anyone have to install this type of seat into the cored floor? I was thinking about over drilling the holes, wetting them out and using toggle bolts and 5200 to mount the plate. I am a little nervous about the loads the deck might see with this type of seat. What have others done? Is there a way to use a backing plate without creating a giant hole? Is there another kind of seat I should consider?

[Peter & Judy]

I have never done this on my boat, but have encountered similar problems in other projects. I suspect the biggest problem you might have is torque on a small base of the seats in the fibreglass floor. If you make that base bigger, perhaps a foot square by first mounting the seat into a marine plywood base and then mounting the base to the floor, you will spread the load and torque over a larger area. You will still need to be cautious on how you mount the screws into the floor. Just my thoughts, I hope they are helpful.

[WCF]

Peter & Judy already gave you the right idea, but I thought I'd offer some more detail.

Assuming you have the same cockpit floor as my 95 (no raised panels):

As recommended above, just bond plywood down. The floor has compound curves, but with some thickened epoxy and care you could get a nice result. Jamestown TotalBoat TotalTread Light Grey is an almost perfect match for the nonskid on my boat; after sealing the plywood with epoxy, just paint over it.

You could also do the same with HDPE (Starboard, Boatboard) bonded with G-Flex and maybe one or two fasteners (Drill-fill-drill into cockpit floor) to back it up. This is the method I and others have used to change up the fuel tank mounting on the older boats.

There are also the Garelick seats that seem sold out\no longer available that can mount to the bulkheads. You could easily find or fabricate a different seat that could mount to the bulkhead.

[thataway]

I agree that Peter's idea of the plywood (or even an aluminum plate base), which could have threaded holes for the pedestal flat head machine screws, Coosa board could also be used. Plywood is best epoxy saturated and cloth covered.

Coosa board: High-density closed-cell polyurethane foam reinforced with continuous strand fiberglass and woven roving. This is lighter than plywood, stronger than plywood, and resistant to moisture absorption and rot etc.

Do not consider the toggles. The floor of the cockpit will have about this layup:

About 1/8" of glass which faces up, and is the "cockpit floor. Then 1 1/2' end grain balsa core, and finally there will be the bottom or outside of the boat, and this should have some 24 Oz roving, mat and cloth: somewhere from 1/4 to 3/8 of an inch thick. (for a 1997 C Dory angler)

There are several ways that the plywood, or Coosa could be fixed to the inner floor. These include glassing them in, with epoxy slightly thickened on the boundary between the inner hull glass (ground to expose mostly only glass to bond to), If you wanted to put a few screws in for double assurance, skip the glassing in place, or using the aluminum plate, each place where the screw or bolt would be placed into the core (any penetration of the inner layers of glass), will require over drilling the bolt or screw hole, then under cutting, filling with thickened epoxy, (making a plug to take the load) and then drilling the pilot holes.

I would put "T" nuts in the plywood or Coosa board, and probably use 5200 or thickened epoxy between the plywood, or Coosa, and the inner layer of the hull. For the aluminum plate, I would tap it with the thread size for the flat head machine bolts, and then do the over drill, epoxy plug for the screws which will hold the aluminum plate in position, and again, use epoxy or 5200 between the plate and inner glass laminate.

All of these make the base for the seats permanent, and prevent water intrusion into the core, plus give a good amount of safety against these bases pulling out.
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[Safetythird]

[thataway]