rotten stringers?

[madmat99]

hello all.
after not being down the boat for a while i managed to get in and have a quick check today.
this hole has always been in the stringer since i bought her but now there is some brown water coming out very slowly.
i presume this is encusulated wood that is rotting inside.
the boat is 30 foot and was made in 79 so is very thick glass.
this is one of 8 stringers, 4 a side and is only in the back 8 foot of the boat.
as there is no real way to get into this as it goes under bulkheads does anyone think this will compromise hull strength?
i can get to the end of the stringer under one of the seats in the cockpit so could pour something in?
any help is appreciated.

Regards


Mat

 

[Deleted member 36384]

Hello Mat,

They look very similar to mine, similar age. Probably it will not effect hull strength. The stringer is made from GRP which is formed over a lightweight core, in my case foam. The foam is just to give the GRP a shape while the resin sets. The strength comes from the shape and thickness of the GRP forming the stringer, post curing.

It could indicate that at some other location on the stringer water is getting in. This could be due to a failure of the bond between the stringer and hull, or another hole. It would be worth carefully checking the whole length to see if there is any damage, as separation would be an issue that needs to be addressed.

The foam in my stringers is a darker brown but dry and hard with no stuff breaking away. This is from a couple of places where it is exposed.

Advice is to look for damage and see if the stringer is still attached the whole length. Maybe a hole had been drilled by a fixing such as a screw penetrating and allowing bilge water to enter the stringer.

Hope this helps.

BlowingOldBoots

 

[dankilb]

I've got a bit of insight into this as the previous owner of our boat (1989 Jeanneau) had all the stringers/floors glassed over as a 'repair' for the plywood core having got wet and rotted in places. This must've been a massive job involving the removal of pretty much the entire saloon (they left the area under the galley alone - thankfully!).

Anyway, my take is that the repair wasn't necessary. For a start, I'm not convinced that finding some rot means the lot is rotten. Secondly, as @BlowingOldBoots rightly says, the core - whether wood/foam - isn't really structural anyway. Just think how the modern 'grid' structure works. No core, just 'hollow' GRP. The original GRP on our stringers was pretty thick - 5mm or so upwards - and I'd assume this provides the majority of the strength. Yours is probably much thicker given the age of the boat. And thirdly, as much as it looks good on YouTube channels, I don't think these sorts of 'repairs' are as structurally-critically as the proponents make out and it's a hell of a lot of work/mess/demolition-rebuilding/etc.

Providing the GRP is sound and there are some working limber holes to allow water to drain between the stringers, I'd just make good and leave it. I doubt that a repair such as the one done on our boat has added more than a small % of strength for all the extra glass that was laid down.

But if you do decide a repair is needed, that is basically the method (grind off any paint/gelcoat and glass over until you're satisfied that the additional strength compensates for any loss of core material). A lot easier said than done though, when by definition the work is all underneath the other bits of the boat!

 

[madmat99]

thanks for the replys and advice.
I will dry it out as much as i can and seal the hole.

Cheers


Mat

 

[William_H]

I agrre the wood or foam is primarily there to provide a structure to lay the GRP on to provide that depth dimension for strength and stiffness. If you are really concerned you could just ignore the internal riot of the wood and lay up more GRP over the stringer. ol'will