Ageing fibreglass hull?

[Ship'sCat]

My 23ft slop was made in 1968. I am wondering if any reader knows about the effects of time on GDP? My concern is mainly about fixings for the 6 u-bolts which attach the shrouds to the deck mouldings. The washers beneath the deck moulding (which seem original) are metal squares about an inch across. I am considering replacing them with larger and thicker versions to spread the load.

 

[lustyd]

If there are no cracks it's almost certainly fine. GRP is a very resilient material and we've yet to see boats reach the end of their service life due to GRP degradation. More often it's because owners have drilled into the GRP too many times, or done poor work on the boat, or left the boat to rot making it cost prohibitive to get back to useful.
What is it about the existing wachers you don't trust? 1968 is a very long time ago and they've held up just fine. If they're rusty then replace like for like, I can't see a reason to uprate something that's been in service for 53 years and coped with the loads.

 

[Praxinoscope]

My previous boat a 1965 Invicta 26 passed its survey at the age of 50 years with flying colours, no problems with the GRP, as long as the original construction was good there is no reason for any major problem, and as lustyd said in #2 GRP damage is much more likely to be from owners than any debatable lifetime of GRP.

 

[JumbleDuck]

The very first production GRP glider, the Bolkow Phoebus, came out in 1964. Like all aircraft they are frequently and rigorously inspected and they are still deemed airworthy. GRP lasts a looooooong time.

 

[Praxinoscope]

Further to my post #3 I would perhaps be more cautious about a GRP/Balsa sandwich construction, IMHO too many potential problems with this method.

 

[Stemar]

Is this a Snapdragon? The shroud attachment sounds the same as on my Snapdragon 24, which is just a couple of years younger. If so, the GRP is pretty much bombproof. The gelcoat had worn thin, with the layup showing through, but this has no bearing on strength. If it bothers you, a lick of paint will sort it. Almost all boats of that vintage were built similarly.

However, you do want to inspect the U bolts. If water gets in between the GRP and the U bolts, you can get crevice corrosion which you can't see until it all goes twang. It isn't likely, but it is possible. Others will know better than me what to look out for, but rust stains around the metal squares could be a symptom of problems.

 

[Refueler]

As Stemar ...

My Sunrider is of similar vintage. They will be still sailing when many of todays lighter construction will be scrapped. (I can hear the fingers itching to hit keys to argue that one with me !! ). But you cannot argue with solid GRP for hull and decks. It took 3 good hole saws to cut the hole for my Log ... I measured the plug I cut out ... solid 55mm GRP and that was not at the thickest part of the hull.

The only area that I have reservation about on my and similar - quite often stanchions are held by machine bolts into the GRP toe-rail, relying on the laminate 'thread' ..... and very difficult to remedy. I had a couple of stanchions come loose and had to sort all of them. Impossible to access up into the U of the toe-rail for all but two - I had to resort to expansion fittings - being careful to size so not to crack / split surrounding structure or Gelcoat.
But the shrouds / stays are well fastened U's with good backing under. I have no concerns for those other as Stemar mentions - check for corrosion.

 

[lustyd]

todays lighter construction will be scrapped.

Specifically which lighter constructions? The 1980's yachts which are in great condition? 1990's ones? Or do you literally mean yachts made in 2020? None of these show any signs of being weaker or wearing in any way whatsoever, perhaps you could share some examples?

 

[Refueler]

Specifically which lighter constructions? The 1980's yachts which are in great condition? 1990's ones? Or do you literally mean yachts made in 2020? None of these show any signs of being weaker or wearing in any way whatsoever, perhaps you could share some examples?

Delivered a few that I ended up seriously unimpressed ... the last boat I delivered - Match 35 shortly after delivery left her keel off the north Kolka point ... later owner said he wished he'd listened to me when I advised he should have her lifted and checked out ..

OK - I was having a dig and baiting - knowing there are those itching to start on me at any excuse ..

But I have actually checked out a few modern boats with cored decks that are well past sell-by date ... requiring extensive work to remedy. Too many were as not a result of owners / others adding items to deck and not sealing properly. But poor fitting at factory ...

 

[JumbleDuck]

Specifically which lighter constructions? The 1980's yachts which are in great condition? 1990's ones? Or do you literally mean yachts made in 2020? None of these show any signs of being weaker or wearing in any way whatsoever, perhaps you could share some examples?

I suspect that bonded grid keel attachments will not age well. As made they are perfectly good, but there are increasing reports of complex and expensive repairs needed after groundings, and as time goes by it will be harder and harder to be sure than any particular boat has not taken a clout.

 

[Refueler]

I suspect that bonded grid keel attachments will not age well. As made they are perfectly good, but there are increasing reports of complex and expensive repairs needed after groundings, and as time goes by it will be harder and harder to be sure than any particular boat has not taken a clout.

The web keel systems were nicknamed Spidersweb when I was involved in UK ...

Then of course we can all talk about Penny Washers .......

 

[lustyd]

I suspect that bonded grid keel attachments will not age well.

Not sure what you mean here. I'm aware of bonded grids, and I'm aware of keel attachments, but I'm not aware of bonded grid keel attachments. I don't disagree that yachts can suffer damage when you smack them into the land. I also don't disagree that from an engineering perspective a long stick with a small attachment point is impossible to make strong enough to prevent such issues. These are problems of fin keels though, not of "modern construction". Any long lever with force on it will damage a surface it's attached to, unless said lever breaks first.
And since the discussion is around longevity of the GRP I feel I mus point out that those boats with bonded grids which have become detatched have one thing in common - the actual GRP itself is generally immaculate!

 

[JumbleDuck]

Not sure what you mean here. I'm aware of bonded grids, and I'm aware of keel attachments, but I'm not aware of bonded grid keel attachments.

Typical modern design is to have the keel attached to a grid bonded to the inside of the hull. Hence "bonded grid keel attachment".

I don't disagree that yachts can suffer damage when you smack them into the land. I also don't disagree that from an engineering perspective a long stick with a small attachment point is impossible to make strong enough to prevent such issues. These are problems of fin keels though, not of "modern construction".

The problem is, or seems to be, that a good whack lifts the grid off the inside of the hull, and re-attaching it can be extremely complicated, not least because the grid is more-or-less the first thing to be fitted when the hull comes out of the mould. In that respect it is a construction issue, though of course other ways of attaching fin keels also have their issues.

And since the discussion is around longevity of the GRP I feel I mus point out that those boats with bonded grids which have become detatched have one thing in common - the actual GRP itself is generally immaculate!

Fair point.[/quote][/QUOTE]

 

[Deleted member 36384]

On some Rival yachts, a bit younger, early to mid 70s, have had the stainless chain plates fail, likely due to crevice corrosion. If these are original on your boat, close inspection should be considered. Another area of concern was wear in the GRP drilled holes for the chain plates, making them slightly oval and oversized, which could contribute to failure of the fitting. I only know of two Rivals that had this issue, so could be user caused damage as opposed to time related degradation of GRP, stainless.

 

[Tranona]

Typical modern design is to have the keel attached to a grid bonded to the inside of the hull. Hence "bonded grid keel attachment".



The problem is, or seems to be, that a good whack lifts the grid off the inside of the hull, and re-attaching it can be extremely complicated, not least because the grid is more-or-less the first thing to be fitted when the hull comes out of the mould. In that respect it is a construction issue, though of course other ways of attaching fin keels also have their issues.



Fair point.

[/QUOTE]
[/QUOTE]
If you look closely the point of attachment is solid GRP. The grid is to transfer the loads of the keel to the hull structure. As you say other methods of keel attachment and load spreading can also be problematic - since boats were built with externally attached keels. Almost always the weaknesses show up when keel hits bottom. When do you ever here of keel problems caused by sailing loads? Look at the standards used for keel attachments as required for the RCD and you will see the huge margins of safety. Given that the vast majority of boats NEVER hit bottom the problem is vastly overstated. As Sunsail have found out, if you discourage skippers from taking shortcuts and penalise those that do, the incidence of keel damage drops dramatically.

The so called "lightly built" boats are now up to 30 years old and do not seem to exhibit the problems the doom mongers claim. Cored deck problems way predate "modern" boats as owners of boats like early Dufours will tell you. Problems can be avoided by not attaching fittings with bolts through cored areas just as Dehler and Bavaria have been doing for 30 years or more. Many of the early problems were associated with poor adhesion between the core and the laminate, exacerbated by laminates being poorly laid up and too thin.

It is all to easy to make sweeping statements, particularly about the supposed superior characteristics of thick solid laminates compared with modern composites, but there are some pretty horrible examples of the former, particularly those where the owners have spent fortunes trying to cure the "osmosis" problems.

 

[Ship'sCat]

Thanks everyone for all the contributions so far. My boat is a Halcyon 23, and it seems to have had a quiet life so far. There is no balsa in its construction.
My interest in this topic began when I read a recent article in PBO where a boat breaker commented that old grip boats break more easily.
My boat doesn't have chain plates per se. It has u- bolts which attach to the deck and go no further. These are marked "Alpha England" and seem to be of chromed steel. They are not very worn but show rust marks here and there.

 

[Tranona]

Almost certainly they will be stainless steel. As suggested earlier, the weakness of this type of attachment is the sealer failing allowing damp to get in and cause crevice corrosion of the shanks. You only normally find out when they break although sometimes you might see rust weeping out from under the plate.

GRP is in itself not particularly strong or stiff. It gets its strength in boats partly from the shape and partly from the stiffening added (bulkheads, stringers etc.). Interested in what breaking up was "better than", although guess it would be steel first followed by wood which is difficult because a wooden boat is a web of interlocked small pieces of wood held together with a myriad of fastenings!

 

[lustyd]

[/QUOTE]
If you look closely the point of attachment is solid GRP.
[/QUOTE]
Yes this was my point, the keel usually attaches to the hull, not the grid. The grid is literally just glued to the hull for rigidity, and sometimes that glue fails under load. The GRP though is usually fine unless it's had a spectacularly hard knock.

 

[PetiteFleur]

Definitely check the U bolts - my previous boat, a Jaguar 27 was appeared to be leaking inside so I tried removing the nut and the U bolt snapped! As mentioned above, crevice corrosion, I replaced all the U bolts with Wichard which were an exact fit.

 

[JumbleDuck]

If you look closely the point of attachment is solid GRP. The grid is to transfer the loads of the keel to the hull structure.

As I said, yes. And as I said previously, over time the issue is going to be the impossibility of knowing which boats have thumped something and which haven't. Unthumped, the design is fine.