Squeaky fibreglass deck

[Mopheus]

The deck in my half cabin has two squeaky spots where I suspect the epoxy to the stringers has failed. The stringers and transom both check out as sound so far as I can tell (knock test; moisture meter; borescope under floor) and should be sound given its history.

It's been like it for years and could probably be ignored, but if I wanted to fix it should I...

1. Locate stringers, drill through deck only (not into stringers) at say 50c/c, inject epoxy.
2. Locate stringers, drill into centreline at say 100c/c, countersink, stainless steel screws w/ 5200 (not keen on this - introduces moisture ingress point).
3. Cut out the main deck area and replace giving me a chance to foam fill the hull void while I'm at it?

Or just continue to ignore it

[Fed]

Without being able to see it or hear it from here....

...could you zero in on the squeaks then locate them exactly with an electronic gizmo (there's probably a phone app for that).
Then have a little dig around keeping the damage to just a square inch or so, maybe a screw or clout has pulled?

[Mopheus]

Locating them is easy - there's about a square foot at each location where transferring weight onto and off the foot that's on that section of deck results in a squeak both up and down. I can chalk out the areas no problem.

No noticeable movement / flex of the deck though some must be happening to make the squeak. It's worse on sunny days when the floor is hot and has expanded slightly. I'll try to get some video later.

There's no question that the fasteners have let go - whether that be clouts, screws or just epoxy. The question is how best to resolve it, or do I just ignore it?

[Fed]

I'd go for your #1 choice.

1. Locate stringers, drill through deck only (not into stringers) at say 50c/c, inject epoxy.

... and I'd do it when the floor was hot & probably bowed up to fill the gap as well as gluing it.

Depends on the boat too, is it a nice one or a hack, you could always get a black texta and label the spots...

STEP HERE
SONIC FISH
ATTRACTION
DEVICE

[Mopheus]

So did some further investigating and think I've found the cause of the squeak. The construction methodology is ... interesting.

Below is a borecam photo looking along the keel stringer (just visible bottom centre) towards the bow showing the first main bulkhead with the deck over. There's another bulkhead closer to the transom but its detailing is a bit different due to the bilge pump recess in the main deck, so this one ~600mm forward of the transom is likely representative of typical detailing.

The bulkhead is arched over the keel stringer and isn't tabbed to it at all. It's also only tabbed to the hull where it sits on the strake as shown in the CAD sketch - it isn't cut to follow the hull vee down to the keel stringer with just a small chamfer cut for drainage as I'd have expected.

Crossmember-26.jpg NkKkbH5.jpg

Here's the joint between the bulkhead and the hull near the bulkhead / port side stringer junction. Just chopped strand gunned on from above with no coverage of the underside of the bulkhead. Bleugh.

Crossmember-7.jpg

So far as fixings go, what I DIDN'T notice at any point with the borecam was any evidence of resin or peanut butter squished out from floor / stringer or floor / bulkhead joints. So I grabbed the thermal imaging camera and had a squizz. Might be hard to pick out but each side of the dark blue cool section in the centre is a line of small pink dots that correspond with the main side stringer locations. They'll be the screws that hold the floor down, with glass and gelcoat applied over the top.

Floor.jpg

The squeaky bits are along the centreline of the floor and are likely movement of the bulkhead against the keel stringer below, or the floor against the bulkhead for that matter (given there are no screw fixings there and no evidence of resin bonding).

So that's the bad news. I don't like the construction methodology or the quality of fibreglassing under the deck, so I'm definitely going to pull the floor to replace the bulkheads at some point. I'll treat the stringers a layer of CSM and 2x layers of 450g DB while I'm at it and then pack it all with Neolon buoyancy foam.

The good news is that it's not urgent. There's no rot down there, nor any evidence of stringer delamination or anything nasty. The bulkhead closest to the transom (below) got the barest wave of the chopper gun near the keel stringer and has a big section of exposed timber that's still nice and sound, so hopefully that's representative of the general condition of the stringers and bulkheads.

Crossmember-4.jpg
(the black dot central is a defect in my borecam lens)

Probably won't do the floor this year as I have a bunch of projects on the go, but I'm not concerned that she'll fall apart in the meantime. The transom checked out as sound with the moisture meter, plus probing of all the various through-holes encountered only solid timber (yet to remove the motor and check those), so doesn't seem like she's affected by age and deterioration - just poor workmanship from the factory =/

[Fed]

You're a legend mate, your detective work is second to none.

Sell it & start again with better bones.

[Noelm]

It's pretty scary when you actually see how boats are made isn't it? It's also easy to see how simple (but expensive) it would be to make a high quality, very strong hull, but it would involve lots of time and hand glassing. You should cut open some of the famous/legendary boats from a few decades ago, most look like they were built in someone's back yard by a bunch of handymen.

[Mopheus]

Sell it & start again with better bones.

That'd be the sensible decision but she has sentimental value, so she's staying. Nothing there that I can't fix and she shows no ill effects from the crappy glasswork other than the deck squeak, and I've driven her pretty hard at times.

It's pretty scary when you actually see how boats are made isn't it? It's also easy to see how simple (but expensive) it would be to make a high quality, very strong hull, but it would involve lots of time and hand glassing. You should cut open some of the famous/legendary boats from a few decades ago, most look like they were built in someone's back yard by a bunch of handymen.

Yeah, I expected chopper gun finish but didn't expect there to not be biaxial cloth tabbing underneath it or even just full resin sealing. I'd like to think the bulkhead detailing was an effort to incorporate some degree of flex and resilience in the keel, but realistically it was obviously just the cheapest method of throwing it together.

[disorderly]

Those photo's are pretty dissapointing...

Out of sight, out of mind..

What make is the hull and how old is she..?

[Mopheus]

1984 Nesscraft.

They are indeed disappointing. While it's only the rear bulkhead that doesn't have full glass coverage - the stringers and fore bulkheads do as far as I could wrangle the borecam to check - the bulkhead detailing is still unusual, the absence of biaxial tabbing is poor and the floor being screwed down rather than epoxied is not ideal.

Fortunately the chopped strand on the stringers looks like it laid down pretty well so shouldn't be much work to knock it back ready for more glass.

This is her mostly stripped back ready for compounding. Excuse the grass - completely redoing the front yard is one of the projects on my aforementioned list, so fixing the stuffed front yard reticulation is not.

20210204_091421.jpg

[gazza2006au]

Use a stud finder find the stringer below drill a hole than inject a glue mix into the hole, dont step on that section for 24 hours