Mounting pedestal seats (fibreglass onto existing fibreglass)

[Curtisa1]

86 ProCraft floor prep - pedestal Seat

What's the best way to prep the existing fibreglass one the floor, too fibreglass the wood bases Down, like Brian 3217 has done? They look great I was planning on doing a similar idea already. I'm worried about how they are going to adhere to the already cured fibreglass floor though, should I use some sort of adhesive, and then glass them too the floor?

 

[JASinIL2006]

I expect a moderator will be along to move your question into a new thread, Curtisa1, since forum rules request you don't add to a topic that's been dormant for more than 90 days. I'll look for the new topic and reply there.

 

[Curtisa1]

Oh ok thank you, would it be best if I just started a new thread?

 

[southkogs]

Gotcha' moved and in a new topic.

 

[Curtisa1]

Hi, I want to mount some pedestal seats as well as a trim pump to the floor. I don't want to put screws into the floor and cannot get underneath because the stringers are in the way. So I've chosen to glass down extra plywood with bolts sticking up, just like Brian3217 has done in this post http://forums.iboats.com/forum/boat...-install-a-pedestal-seat-in-a-fiberglass-boat
Im Worried about how well the braces are going to glass onto the floor. My question is, what's the best way to prep the existing fibreglass to adhere to the new braces. Should I use some sort of adhesive, stick the brace down and then glass over it. Or should I just sand and glass?

 

[JASinIL2006]

I made my pedestal seat bases like that when I was rebuilding my boat. The process would be pretty much the same for you, though.

My seat bases were made of two pieces of plywood glued together (using Titebond III glue), and then cut on an angle, pretty much like those in Brain3217's post. I drilled the holes for the pedestal mounting bolts into the bases and installed heavy stainless steal T-nuts to receive the screws that hold the base of the pedestal seat. I covered the holes for the mounting screws so resin, etc., wouldnt' get in and mess up the T-nuts.)

I used thickened polyester resin (aka 'peanut butter') to glue the seat bases to floor. You want to grind away any gelcoat or paint or whatever from the deck surface, so you get down to good, clean fiberglass. I put a thick coat of thickened resin on the bases and then positioned them on the deck, weighting them down with a couple of full paint cans to insure good contact. I smoothed any resin that oozed out around the edges into fillets that would make glassing easier.

I then applied several layers of 1708 biaxial cloth over the bases and onto the deck surrounding the bases. Each layer overlapped more of the deck, until the last layer extended about 10-12" from the perimeter of the seat base. (More details about designing and installing these in my resto thread; see link in my signature. The parts that deal mostly with seat bases are in posts #99-110 and #140-151.) After glassing, I drilled out the fiberglass that covered my pre-drilled holes in the bases, and I was ready to install the seats.

These bases have been extremely solid. I'm a tall guy and I like to look over the windshield when I'm driving the boat, so I put in a tallish pedestal on the driver's side. Even with the extra leverage of the taller seat post, the pedestal base is really stable and doesn't budge. I personally would not even think about installing these kinds of bases without both a good adhesive underneath and several strong layers of fiberglass on top.

Hope this helps. If any of this doesn't make sense, let me know and I'll try to clarify.

Jim

 

[Curtisa1]

Great! Thanks for the response, so I will just use "peanut butter" to actually adhere them too the floor rather than some other kind of adhesive. And just to be clear, by peanut butter you mean fibreglass resin mixed with fibers.? I was already planning on layering mat down on top of them after, was just unsure what too use between the bases and the existing floor. The existing floor is unpainted fibreglass (mat) still. I also plan on glassing down a similar base underneath the splashwell to mount my trim pump onto.

 

[JASinIL2006]

Yes, peanut butter is polyester resin thickened with Cabosil and chopped fibers.

When you say you plan on "layering mat" on top of them, what are you actually referring to? When I read 'mat' I think Chopped Strand Mat (CSM) which I don't think is strong enough. You probably want something stronger, like 1708 which is a woven biaxial cloth with CSM stitched to one side. (The CSM helps with adhesion as you lay up multiple layers of cloth.) I would not try this with CSM alone on top of the pedestal bases.

 

[Curtisa1]

Yes I was referring to CSM, and was planning on using it as I have some left over from my floor, but I will get some cloth. Thanks for the advice, I am new too fibreglassing and still have lots too learn!

 

[JASinIL2006]

One nice thing about the 1708 is that, if you work it a bit, it really lays down nice over the corners. I like it's conformance to the underlying shape of the seat bases. Much easier to work with in that regard than CSM, in my opinion. Plus, it's really strong compared to CSM.