[Public-List] Deck to Hull Seam on pre-liner boats.

[Gordon Laco]

Hello Jonathan, 

Was it a pre or apres 400 boat?  I can write about the apres 400 boats hull to deck joints.

Those are made with the deck flange over the inward turned hull flange.  At the boatworks, the technique of joining the hull to the deck was to lay a strip of polyester resin wetted fibreglass cloth along the hull flange, then lay the deck onto it.  Pop rivets held the two together while the resin cured… and were left in place.  The real work of holding the deck to the hull was done by the many bolts securing the long genoa tracks in place port and starboard, the bow plate casting up forward and the backstay knee aft.

I have a schematic drawing of the joint in cross section i can send directly to you.  Here it comes. You folks on The List won’t see it because of the firewall, but if you want to see it ask me and I’ll share it.  Actually George may already have it on the site but I forget.

The joint starts to leak over the years because polyester resin is relatively brittle, and doesn’t bond to already cured glass as well as epoxy might have.  And… the pop rivets can let water through the holes in the centres of them.   

I resolved my leaks in my apres-400 boat by removing the teak cap rails, a much easier job than I thought because they were only held in place by self tapping screws (whatever bedding might have glued them was long dried up and gone)  

I wire brushed the exposed hull to deck flange (I could see the edges of the thin and brittle cloth strip that had been laid between.  I sanded the top of the deck flange to flatten the pop rivet heads, then filled all of them and the self-tapping screw holes with thickened epoxy.  I ran 3M 4200 into the edge of the flange, filling it all around the boat.  When I replaced the cap rail, I did not put self tapping screws back in.  I drilled holes right through using the old holes in the cap rail as guides (they were pretty full of varnish which I’d applied all round them, top and bottom.  I tapped threads in the fibreglass then drove in #10 machine screws.  I dipped each screw in varnish before running them in, reckoning that the varnish would both lubricate them on the way in, and form a watertight seal once it dried.  And of course I figured the machine screws would be an asset in adding to the integrity of the joint, rather than just tentatively holding the cap rail on.  I bedded the cap rail in a solid mush of 3m 4200.   

Result? No leaks last year even after sailing rail down in a hard thrash to windward.


Gordon Laco
426 Surprise




> On Nov 29, 2021, at 7:51 PM, Jonathan Bresler via Public-List <public-list at lists.alberg30.org> wrote:
> 
> Dear Albergers,
> 
> Recently, I had the opportunity to see a boat from which the stainless
> steel rail that covers the deck to hull joint had been removed.  From
> memory, it appeared that the deck is set on top of the hull inward flange
> and bolted together.  It being someone else's boat, I didn't start digging
> in there with a screwdriver or awl to determine if there is a fiberglass or
> epoxy bond or if there might be filler material.  At any rate, the seam was
> open a bit onto the flange.
> 
> What have folks done when the opportunity arises to remove and reseat the
> rubrail.  Constance has what appears to be some rust staining from the
> rubrail.  Wondering if someone trying a sealant on the rubrail and the
> sealant is now trapping water causing the stainless to become stain-more.
> Planning on removing the rail this winter to clean the stains and remove an
> sealant on the rail.   Wondering if I should take the opportunity to fill
> the seam between the deck and the hull so that its flush with the outer
> surface of the hull.
> 
> Hopefully, I've described this well enough that its possible to visualize
> the situation.
> 
> All the best,
> Jonathan
> 
> -- 
> Jonathan M Bresler
> S/V Constance Alberg 30 #262
> Annapolis/Eastport MD
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