Mainship Flybridge Helm Chair Fasteners

[peterg]

Hi All -
Does anyone know how Mainship (2003 430 Double Cabin) fastened the flybridge helm chair to the deck? Thru-bolted with nuts on the underside (hidden by the salon headliner)? Backing plate embedded in the deck? Lag bolts? Other?

I need to remove the chair for a repair, but I don't want to touch the headliner. Afraid if I try to loosen the bolts I will potentially lose any nuts on the underside, or the nuts will just spin.

Thanks,
Peter

 

[Comodave]

On a previous boat I fastened the second helm seat to the deck by using a hole saw in the middle of the seat base so I could put tapped aluminum backing plates in from the top. Does your seat base have a large hole in the middle? If so you might be able to drill a hole and feel what is under the deck. I used a base that bolted to the deck and then the pedestal base bolted to it.

The base plate was similar to this one except it had a large hole in the middle. You bolt the base plate to the deck and then bolt the seat pedestal to the base plate. You could cut a large hole in this base plate to be able to stick the backing plates in under the deck.

Garelick 75056-G Detachable Pedestal Plate​

I also didn’t want to mess with the headliner. I carefully used a hole saw to cut through the deck so I could slide 6 3/8” aluminum plates under the deck plate bolts. It worked well.

 

[peterg]

Yeah, that would be a smart way to do it. As far as I can tell, the seat post does not detach from the base, although perhaps they are just corroded together. I will investigate that aspect further.

 

[Comodave]

I did a search but didn’t see the exact plate that I used but it was like the one in my previous post except it had about a 3” hole in the middle. It was pretty easy to do. In case you loosen yours up and can’t get it tightened back up you could do it the way I did.

 

[SIBERNUT]

SS Toggle bolts

 

[peterg]

Comodave, Sibernut - thanks for the ideas. I'm just gonna have to open it up and see what I find.

 

[peterg]

I was happy to discover my helm chair was already installed with a base plate, as Comodave suggested. Easy to see after removing the (indoor) carpeting the PO had installed between the base plate and the chair pedestal.

 

[Migor]

It's 1/4-20 flat head bolts attached to embedded plates.
I removed standard "bench" seat with two posts, installed plate on original attachment points and put new single post chair. Now i can adjust height, rotate the chair to dining table and have a more comfortable seat when underway. Currently on the Loop and appreciate this mod.

 

[peterg]

That's a nice solution Migor, and a nice helm chair! My 430 came with the single helm chair, which I also prefer to a bench seat.