My pedestal install idea - will it work?

[Sunsetrider]

I intend to replace my driver side lounge seat with a pedestal/capt. seat and i've bought the pedestal with rotating top. It's 14-20 inch swivl-eze with a 9-inch base. I've yet to choose a seat. I hope it isn't too tall but after testing it in the boat (with a jump seat cushion) I think it'll work out fine.

Biggest concern will be the mounting method, and I am challenged there because of my unfamiliarity with boat construction. The dwgs below show (2) the 9-in. base with 6 bolt holes and in blue, the 3.5 in. hole I will cut in the floor, (1) the aluminum plate I will have made up to secure beneath the sole I messed up the upload order), and (3) the 2 superimposed. The idea is to place the plate in position through the 3.5 in. hole, then use epoxy or marine sealant to place a nut under each hole in the plate (lined up with the holes in the ped base).

Or am I going too far and should just use fender washers at each nut position? Will there be 9 inches clearance between stringers (the ped is to be placed in the center of the stringers which are used to anchor the lounge)?

This method seems to me superior to glassing more plywood on top of the deck as some suggest. And avoids the mess of glassing which I want to avoid.

Opinions sought! here are the "design pics":

 

[bouttime007]

Re: My pedestal install idea - will it work?

There was a post I was reading a week ago about these T nut fasteners that I think WoodGlass was suggesting to a poster.

Those would be a good idea in your case.

 

[Woodonglass]

Re: My pedestal install idea - will it work?

I never think it's a good idea to put holes in the deck. That's why I always recommend laminating a platform to the deck with stainless steel T-nuts on the underside and then using Stanless steel bolts to attach the pedestal. Something like this...

(Click the Pic to Enlarge)

 

[proshine43]

Re: My pedestal install idea - will it work?

I agree with woodonglass, i did that same setup with the t nuts. Worked perfect. I glued 2 sheets of 3/4" ply together, cut 45 degree angles, glued to deck, laminated all and it works great. I dont plan on putting any holes in the deck.

 

[Grandad]

Re: My pedestal install idea - will it work?

Just a note of caution using T-nuts. I used new 1/4"-20 stainless steel T-nuts in a refurb project for the seats on my Starcraft. They were concealed inside the seat structure where I could no longer access them. One of them galled badly when I inserted a new stainless steel bolt. The threads locked together so securely that I had to cut off the bolt head and dismantle the seat to get the nut out. Curious, I put the stud in my bench vise and used a pipe wrench to turn the nut. I twisted the stud off. It was virtually welded in the nut. Now whenever I thread stainless fittings together, I apply some good lube first. Grandad

 

[Woodonglass]

Re: My pedestal install idea - will it work?

Grandad makes a good point. Use a little 3M 4200 on em and you'll never have to worry.

 

[jigngrub]

Re: My pedestal install idea - will it work?

WOGs method looks like a good install... just curious as to what kind of adhesive y'all would use for that application? What would you do if carpet or vinyl was already installed, cut it out the size of the wood base and run a bead of 5200 around it after the install?

If you never put a hole in a glassed it deck it'll last a very long time.

 

[Woodonglass]

Re: My pedestal install idea - will it work?

If it's already got vinyl or carpet then you would have to cut out and grind to fresh glass, wood and then laminate the base to the deck.

 

[oops!]

Re: My pedestal install idea - will it work?

an alum plate under the carpet.....at least 12 inches behind the mounting plate....the stress is for and aft on a pedistal seat.

 

[Sunsetrider]

Re: My pedestal install idea - will it work?

. That's why I always recommend laminating a platform to the deck with stainless steel T-nuts on the underside and then using Stanless steel bolts to attach the pedestal. Something like this...

That looks very good - except it would be nice to avoid the additional height - but I wish I could get more detail on it.

 

[Woodonglass]

Re: My pedestal install idea - will it work?

What kind of detail are you looking for?

 

[Sunsetrider]

Re: My pedestal install idea - will it work?

I'd like to know:

- the method and materials to laminate the platform to the deck;
- is the platform made of marine-grade fir 1SG plywood? 3/4 inch? is 12" square sufficient area?
- what product might be used to coat the platform?

I am convinced that I should avoid penetrating the deck.

 

[Sunsetrider]

Re: My pedestal install idea - will it work?

Did a little more research into the dreaded fiberglass subject. So . . . proposal is to cut a 12x12 3/4 plywood, bevel the edges with belt sander, drill 6 holes for the T-nuts. Secure the platform to the fiberglass surface of the deck (after removing a 12x12 section of carpet) with epoxy using this method - http://www.westsystem.com/ss/bonding-gluing-clamping/ -
Now . . . it is then recommended to laminate the platform to the deck with fiberglass . . . but why not simply apply several coats of varnish or similar to the platform? Surely that is enough to protect the material from the splashing of wet bathers or a few raindrops? And after all, how difficult to replace after many years of use? Varnished wooden boats seem to stand up well enough.

What am I missing?

 

[jigngrub]

Re: My pedestal install idea - will it work?

proposal is to cut a 12x12 3/4 plywood, bevel the edges with belt sander, drill 6 holes for the T-nuts.
What am I missing?

The plywood base is actually 1 1/2" thick with 2 pieces of 3/4" ply laminated together.

I would put the 45* bevel on the ply with the skill saw after the 2 pieces have been laminated together.

 

[Sunsetrider]

Re: My pedestal install idea - will it work?

The plywood base is actually 1 1/2" thick with 2 pieces of 3/4" ply laminated together.

I would put the 45* bevel on the ply with the skill saw after the 2 pieces have been laminated together.

Sure, skil saw makes sense . . . but why 2 layers of plywood? Would one not be enough with the T-nuts? I am concerned about every increase in height since my pedestal is already a bit higher than I would like for the low position.

And further look into the West System seems to suggest that since I have the epoxy going for bonding I might as well use it for the purpose of a barrier on top as well.

 

[jigngrub]

Re: My pedestal install idea - will it work?

but why 2 layers of plywood? Would one not be enough with the T-nuts? I am concerned about every increase in height since my pedestal is already a bit higher than I would like for the low position.
.

I'm pretty sure the pad thickness is for strength and to help with flexing.

A pair of shoes like these should help with any seat height issues you may have.

 

[Woodonglass]

Re: My pedestal install idea - will it work?

Or you could make the Pedestal 3" tall and not even use your pedestal. Just mount the seat directly to the wooden pedestal. I would highly recommend using glass to tab the pedestal to the hull and not rely only on the epoxy to seal it to the deck. Rustoleum Oil Base paint with Hardener added is a very durable finish coating.