Blind fixings for stanchions?

[greeny]

Does anyone know of a corrosion resistant (preferably SS) that I can use to fix a supporting stanchion base on my rear "bathing" platform. Very difficult to get to the underneath of the step as on one side it's behind the steering gear and on the other it's behind the fuel tank. Self tapping screws are in at the moment but are too flimsy for the job. There's lots of things for plasterboard walls etc but I can't find anything for marine/ corrosive applications.
Greeny

 

[john_morris_uk]

Is it truly a hollow behind where the stanchions need to be fitted? The bases will need some pretty solid fixings and if they end up through bolted they will need backing plates in a ideal world.

If you really can't get access, then I have seen even winches and engines mounted on studs that were cast into epoxy filled holes in a solid substrate.

Hope there's a start of an idea somewhere there?

 

[VicS]

If the grp is thick enough I would consider tapping holes to take ordinary metric machine screws.

I'd put them in with a dab of epoxy such as Araldite on the thread. If the thread is not degreased it will always be possible to unscrew them again.

Not ideal but much better than self tappers


Rubber ( or plastic) Rawl nuts may be a possible solution. Slightly counter bore or countersink the holes so that the heads sit flush with the surface.
I think though that their resilience will make for a less than secure feel to your stanchions.


No substitute IMHO to properly through bolting with backing pads and/or plates

 

[pvb]

Here's a plan. Make up a backing plate with holes matching the stanchion base, and holes either tapped or with welded-on nuts. Drill another small hole in the centre of the plate. Drill the deck where you want the stanchion bolts to go. Drill another hole in the centre of this group of stanchion bolt holes. Feed a thin piece of wire through the deck into the void, through the centre hole. With enough wiggling, you ought to be able to locate the wire via the steering gear access. Feed wire through centre hole in backing plate and secure it with Araldite. Then pull wire out from bathing platform until backing plate is under the stanchion base area. You'll then need to rotate the plate by twisting the wire until the nuts or tapped holes line up with the holes for the stanchion bolts. Insert bolts loosely, then cut wire off. Tighten bolts. Open beer.

 

[greeny]

Thanks to alll for your suggestions, I'm heading off to the boat today (in Portugal) and will investigate the possibility of threading a backing plate into position on a length of wire. Sounds feasable and gives me the secure fixing I need. Thanks to PVB.
I'll let you know how I get on.