Blind bolting

[Guest]

For use in doors / walls / domestic situations - you can find "Blind bolts" in steel / alloy etc. Drill a hole, push through the tubular bit .... then screw is put through item to fix and then screwed into the tubular part. That expands to lock the whole thing to the door / wall etc.

Now my question is that often there are some really bad designed blind fixing items on boats that similar could really be valuable for .... I've never found "non-corrosive" marine quality in these fixings ....

Has anyone any idea if such exists ?

 

[savageseadog]

Expanding bolts. There are some epoxy glue based systems as well. There wouldn't normally be sufficient depth for these bolts but there are some blind threaded rivet systems called Nutcert or Nut-Cert, Rivnut etc made by Avdel and others. There is a vast range of materials they are made from, including aluminium and stainless.

 

[Guest]

Areas like Toe-rails where they are moulded inverted GRP U ... you can't get up inside them with spanners etc. Great when boat is built and deck is not on hull. But later when the stanchion base pulls ...... I've used studding and pulled a nut / washer combination up on the stud and then nut outside to tighten - but it's not same as a screw head the sits flush in the fitting.

 

[Evadne]

I suppose with low loads then s/s helicoils might work?

 

[rogerthebodger]

On my GRP Tender I made a strip of stainless or ali and threaded a hole in the center for the set screwthe size of the fitting (cleat of stantion base etc) the strip was the width of the inverted U shape section and longer than wide so when it slotted up inside the inverted section it would not turm. I then used some sekaflex or panel glue on the ends of the strip away from the threaded hole and held it in place untill glue set with studding or bolt.

Once glue set removed the bolt / studding and bolted the fitting on, strip then clamped with fitting so glue not taking load.

In an area that I could not get to from the underside I cut slot width of strip in GRP at the screw hole position. I then fixed a length string through threaded hole in the strip with a stopped knot and pushed strip through slot and pulled up to underside of inverted U with string. Once glue set cut string pushed it through the threaded hole and fixed fitting as above.

It a bit fiddey but can be done

 

[Anchorite]

Drowned nuts

They exist in France and are called "écrou noyé" : main manf is BOLLHOFF...if you google you will find diagrams. Couldn't find anything in English, plenty in Deutsch. Stainless A4 (316L) passivated in 4 mm. Used a lot over here for mast fittings.

 

[PBooth]

I've use aluminium rivnuts in GRP with good results, you need to coat the insert with sealant before setting it with the tool. Also, don't clinch up the insert too tightly to avoid splitting the GRP.

Peter