Cracking in Older Fibreglass Boats

[MikeC90]

Hey folks,

I'm chasing some feedback on what would be considered normal 'wear and tear' for an older (20+ years) fibreglass boat and what would be concerning 'damage' worthy of investigation or repair. Not so much the exterior hull but rather the internal structure showing stress cracks and the like. I gather the glass will degrade and weaken a little over time, along with the timber, and ultimately need attention, just looking to get an idea of what that line in the sand might look like.

Any personal experience/photos of examples and/or repairs would be excellent.

Thanks

[Noelm]

As a general rule (very general) cracks other than "spider web" looking cracks are a sign of structural rot/damage, even a tiny bit of softness in the floor means a big job ahead, and funny looking "plates" bolted to the transom mean suspicion, regardless of what the seller says, be wary.

[disorderly]

Talking to a local guy this week about his experience buying a bargain cruisecraft 550 sight unseen...just to be sure it was OK he paid $400 to get a full boat and motor inspection...

Soon as it arrived in FNQ from Sydney and he stepped on the floor he realized he was in trouble..it was rotten throughout and he has just finished paying for a full rebuild and new motor...

Nice boat now but the 60K plus it owes him is probably more than it originally cost...

[MikeC90]

No issue with rot in this instance, what I'm looking at it is the result of hull flex from a wave impact. The boat is 22 years old and previously had some hairline cracks in a few spots but these few things are new. You let someone else drive for 2 minutes and...

Cabin entry
IMG_2339.jpg

Side step/shelf that runs along the deck just above the floor (image sideways sorry)
IMG_2337.jpg

Cross brace in front of the fuel tank well
IMG_2348.jpg

Join between the cabin bulkhead and floor
IMG_2346.jpg

I've not been around enough old boats to know if this sort of stuff is typical wear and tear that will still look much the same in another 10 years or if it is cause for concern. My thoughts at this stage are that nothing there is going to be of consequence but I'd like some feedback from those that have seen/owned many an older glass boat.

[CT]

The cross brace and floor stuff doesn't really concern me, but how big a hit was it for the cab entry to crack!

My Cruise Craft never got much worse than that even after the stringers were mush. The transom cracking was much bigger and impossible to ignore. Some sections just had thin air behind them! I put it down to engine flex making it show more than wave action on the stringers.

[MikeC90]

It was low speed (<20km/h) but still a nasty bump... I didn't get a great look at the waves as I was putting some sunscreen on my little fella while dad had quick steer. It was the wake from a decent size cruiser in otherwise calm water (approx. 1 ft wind chop). I gather the wake must have synced with the natural waves at just the wrong moment, as the size of the hole took him by surprise when he got close enough to see over the crest of the first wave. He backed off and turned square to the wave at the last second but unfortunately that ended up being exactly the right speed to do a little jump into the face of the second wave, landing with much of the hull's surface area at once rather than nose or bum first.

I'm not 100% sure if the cabin entry crack is from the boat flexing or dad's knee/hip hitting it when we landed. Where the crack is, it would make sense for either - the top deck mould would only need to flex a few mm to 'open up' the archway and cause a tension crack in the corner where stress concentrates (it's only 3mm glass with no structure there).

The boat still felt identical to drive following the impact, no unusual creaks or groans when going through 2-3 ft swell further out.

[gazza2006au]

Cruisers here in botany bay create big wake u definatly dont wanna hit them at speed the wake is usually a good meter high with another few following it behind just idling over the wake u take some water over the bow in a 4.5m hull

If your old man hit that at 20-30kph that would be a terrible hit

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