Additional small hatch fixings?

[Simonpk]

I am about to fit an additional small Lewmar hatch. Can this be fixed down with self-tappers as opposed to through bolts? The reason I ask is because the hatch is to be mounted directly onto the deck, then have a backing of 18mm marine ply surround underneath the deck. I assume the deck is about 10-15mm thick, along with the surround, giving me between between 28 & 33mm to screw into.

This will be easier than cutting 11 stainless bolts to the exact length, neater & less chance of scalping yourself on protruding bolt heads.

 

[maxi]

Self-tappers, very easy for the nocturnal visitor to remove and gain access to your valuables and valuable boat, at the very least, use 'security' self-tappers.

 

[VicS]

A small hatch could probably be screwed to the GRP deck with self tappers.

I'd drill a clearance hole through the gel-coat and a generous sized pilot hole into the GRP.

Other wise a clearance hole through the deck and screw into the wooden backing pad.

Alternatively counterbore the backing pad and use bolts and recessed nuts.

(Dome nuts if there is no objection to protruding nuts but you just don't want sharp edges of bolts sticking through ordinary nuts)

 

[RAI]

my 2 cents

Boats flex more than hatches, so self tappers are unsuitable, especially if your deck is balsa filled. Even solid fibre glass does not take to self tappers very well. Drill through large, back fill the holes with epoxy and then drill again to the right size. Seal the bolts with silicon. Use domed head nuts or recess them into your backing plate as Vic suggests. Best to have large washers too.

 

[OGITD]

Yes you can.

The top section of my Fwd Houdini Hatch is held down with self tappers into the balsa core, & yes it has resulted in leaks which was quickly rectified with flowable silicone.
But don’t tell Seajet as he’ll be on my case as to the build quality & design of Newbridge boats again!

 

[Simonpk]

PS. 'tis only a small hatch for ventilation & more light. The hole is, going to be, 19 x 33cm (7.5" x 13" in old money)

 

[rob2]

You could use interscrews on the inside so that they fit flush.

Rob.

 

[VicS]

You could use interscrews on the inside so that they fit flush.

Rob.

Good idea

Available mail order from the likes of A2A4 and Sea-Screw but a limited range of sizes available

Also called "case nuts" I think you will find

 

[Simonpk]

Thanks Rob & Vic, good idea, that's the way I'll go.

 

[Seajet]

The top section of my Fwd Houdini Hatch is held down with self tappers into the balsa core, & yes it has resulted in leaks which was quickly rectified with flowable silicone.
But don’t tell Seajet as he’ll be on my case as to the build quality & design of Newbridge boats again!

Old Glow in The Deeps,

I've got just 2 words to say to you; ' Morning Cloud ' !