Epoxying nuts to underside of deck

[oilybilge]

When I'm working on the boat by myself (ie, nearly always) I find one of the trickiest jobs is re-attaching the deck fittings after cleaning or painting. You have to screw the bolt from above and simultaneously hold the nut down below in the cabin. So I was wondering about getting some flanged serrated SS nuts and epoxying them to the underside of the deck. Then I could do everything from above.

Has anyone tried this? Are there better ways?

FWIW it's a sheathed plywood deck, and I'm talking about fairly lightweight fittings such as deck vents etc.

Cheers!

 

[Poignard]

"Big heads" would be better. The larger bonding area means less chance of them being wrenched off

 

[rogerthebodger]

I cut a piece of stainless steel and drill and tap a hole on the plate and attach it to the underside of the deck with whatever glue is available at the time

I have done this several times on my dingy and motorboat with sealed so difficult to aacces the underside of the sealed compartment

 

[geem]

Buy a wife. They come in handy

 

[Fr J Hackett]

There is nothing intrinsically wrong with what you want to do but are there backing pads insitu if not either the idea of a drilled and tapped plate stainless, mild steel or aluminium would be a good way to go.

 

[Stemar]

Buy a wife. They come in handy

Yes, but the running costs...

 

[srm]

Has anyone tried this? Are there better ways?

When fitting a new heads it was near enough impossible to tighten the four bolts with nuts under the GRP moulded shelf the WC pan was mounted on (and no room for a wife to get in there to help). I used quick setting epoxy putty to hold each nut and washer having positioned them using the bolt with lubricated thread to stop epoxy gluing up the moving parts. Come to think of it I could probably have cast the thread in a lump of epoxy putty without the nuts.

 

[geem]

Yes, but the running costs...

There are other benefits as well

 

[thinwater]

"Big heads" would be better. The larger bonding area means less chance of them being wrenched off

The down side of fixing the nut and spinning the bolt is that sealant will be spun away from the bolt, increasing the chance of leaks. Tightening only the nut is always better.

This is why thread deack inserts nearly always seize. The sealant allows water to leak down to the threads. It does not leak into the boat, because the threads are tight, but they corrode.

 

[westernman]

Yes, but the running costs...

Cheaper to rent.

 

[Fr J Hackett]

The down side of fixing the nut and spinning the bolt is that sealant will be spun away from the bolt, increasing the chance of leaks. Tightening only the nut is always better.

This is why thread deack inserts nearly always seize. The sealant allows water to leak down to the threads. It does not leak into the boat, because the threads are tight, but they corrode.

A butyl washer formed from wrapping the threads under the bolt head with butyl tape would seal it.

 

[Fr J Hackett]

Cheaper to rent.

If it Fs, Fs or Fs cheaper to rent but maybe not as satisfying.

 

[Refueler]

The old trick if you can get at the underdeck with some room to spare :

Take a long bolt ... grind the threaded end so it has two flats parallel ... to suit an open ended spanner. If needed - drill small hole through that flat for a fishing line to keep hold of ... its a trick for through hulls.

Bolt placed through deck, now apply the washer and nut ... you can now hold the bolt with spanner while tightening the nut.

Excess can be cut off - taking care where metal swarf goes ...

 

[Fr J Hackett]

The old trick if you can get at the underdeck with some room to spare :

Take a long bolt ... grind the threaded end so it has two flats parallel ... to suit an open ended spanner. If needed - drill small hole through that flat for a fishing line to keep hold of ... its a trick for through hulls.

Bolt placed through deck, now apply the washer and nut ... you can now hold the bolt with spanner while tightening the nut.

Excess can be cut off - taking care where metal swarf goes ...

Good tip you could make it easier by putting 3 nuts and the washer on the bolt then locking the last two bolts against each other and then a spanner on the bottom one and tighten the inner (first nut up.

 

[dankilb]

As others have suggested above - switching to different fastener types (big heads or those pronged nut things) to make 'captive' with epoxy doesn't seem worth the faff... Screws, nuts and washers have many inherent advantages for this application!

We're nearly through rebedding dozens of deck fittings (and 000s of fasteners) on our 41' AWB. In the end, I found my preferred solution was simply to work with over-length screws (at least 10mm too long) so that I could hold the end with mole grips while tightening. With care, that method proved sufficient to stop the head turning/squeezing out the butyl tape we predominantly used. An extra lock nut could also work as above. When done, I cut the excess off with a 'widowmaker' cut wheel on my die grinder - but a hacksaw would also work!

 

[fisherman]

I just used to put a mole grips on the nut, and string/clamp/bit of wood jammed across to somewhere/any heath robinson/screw through the handle to hold it til the nut came tight.

 

[Refueler]

Captive nuts - the ones with prongs and various other 'blind' nuts are usually of crap steel and not good for boats ... not long before rust streaks start appearing ... or staining

 

[oilybilge]

Wow, so many great replies. Thanks guys.

Yeah, I'd wondered whether turning the nut was better than turning the bolt, so I might give the extra-long bolt trick a try. Cheers!

 

[fisherman]

If it's a deck fitting you can sometimes leave a ring spanner on the bolt head on top, (bluetack helps) the fitting will stop it turning, put the nut on below.

 

[LadyInBed]

I screw the bolt down, leave it with a ring spanner attached locking it in place with a length of cord then go below, put on the nut and ratchet it tight.