Deck joint-Who, What and When

[ebb]

OK, so when you look at the photos,
the lips coming together wasn't where the separation occured.
In this case it tore apart at the angle where the deck flange turned. Easy to see that it was the
flange turn that zippered. Probably because the deck is not as strongly laminated as the hull.

So can we agree... the weakness in the join is not where the two flanges come together -
but where the two flanges are forced to make hard right turns.
One thing we know is that fibeglass doesn't like point loads and doesn't like sudden changes
in thickness. The glass fibers in the apex of thse tight turns might be broken.
If this is correct, then the sudden out turn of the deck and hull flanges are a weak construct.
The way the boat came apart is the clue.

So is there maybe a fix for this?


Get some 1/2" polyethylene sheet and cut it into 3/4" wide strips. Epoxy doesn't stick to this, so you'll use the strips as dams,
using double sided carpet tape as a stickum.
Maybe you put them on the boat about 3/4" above and below the pursed lips.
Intent is to increase the overall width across the flanges to say 1 1/2" (or a little more) and about as 'deep' as the lips stick out.
This might create the width needed to drive 1/4" holes thru the toerail and the hull for bolts.

How does this tie the lid onto the jug?
Puttty knife a fairly stiff mix of epoxy/cabosil/chopped-strand into the grooves on either side of the lips
Let it set, remove the dams. Round over the new edges, maybe 1/4" - 3/8".
Tape on a skirt of masking paper.
The area above and below the new 1 1/2 + composite now might be filleted with epoxy gel.
With a gererous curve you still can make very economical use of filler and a end up with a
nice clean coved transition between 90 degree surfaces. A lot of fudging at the stern and bow.
This also will probably have to set. It'll get a medium grit sanding to smoothe and even it out.

What's going to tie this together?
Measure (with a strip of paper) a length from the top of the toerail to below the new cove at the bottom.
Make this the width of the first run of some fiberglass TAPE. Tape is great, it has one continuous width and selveged edges.
(Extra thickness built up on the toerail seems a good idea...per our ghastly example of treacherously thin laminate).
Maybe some 4" wide and 3". A series of widths to amalgamate this sculpture together.

Then drill 1/4" holes thru into the toerail and into the hull, maybe in offset pairs. Probably counterbore the heads flush with the top.
Placing these holes is going to be a PITA, every hole will have to be planed.
The tapes you are using create the line and limit of the sheer on the hull. This could be emphasized or
could be faired away by grinding after set. Remember this expanded structure will make shadows that might show hiccups.
Layer different widths on top of each other. Always keeping them in line. Some suggest pasting narrower tapes on first, and gradually wider.
Others say the other way. Experiment, it depends on your technique and the tapes you use.
How many layers? Depends on weight of cloth...3 - 4 - maybe 5 ?
The tapes might be applied in say five foot strips that are wet out first on the work table. Subsequent layers staggered at joins.

After set, grind and sand, fill and fair til it appears to be part of the original boat
If the hull is painted, why bother to imitate gelcoat? Prime and fill with white epoxy primer & paint. Finish the new standoff with hull paint.

Depending how well it comes out,
screw on a nice rail of mahogany or teak. Rout out the back of the rail a bit so that the wood hugs the standoff and doesn't get peeled off
when you're rail down. Drill some small vertical drain holes close behind the wood , not too close to the hull. Flat or rounded, varnished or plain, it'll be gorgeous and strong.

This is merely a bunch of ideas, not a plan of attack.
I agree that if a 50 year old production boat is planed for a voyage, and if it is known to have problems in any major structural area, the
problem has to be taken care of. Ideas lead to other ideas and so forth. No exuses for BSing!