Gelcoat hairlines

[Grehan]

I've got a few places - almost all where there's a change in surface direction - where the gel coat has developed a small group of hairline 'cracks' (although they're hardly that).
Like this -

In spite of the fact that the photo shows a stanchion base I don't think they're physical stress related, but possibly more to do with technique when the GRP/gel was originally laid up and/or summer heat/winter cold cycles.
I'd welcome any thoughts about them - cause? - but more importantly how to deal with them. I don't really think they warrant time-consuming extensive scraping back and re-gelling (with a potential colour match problem) and painting doesn't seem like a good idea either.
Thanks in advance.

 

[oldsaltoz]

They look more like stress cracks to me.

 

[30boat]

They look like stress cracks to me but I wouldn't worry.If the aestethics don't bother you leave it alone.Fitting a better pad underneath bedded in epoxy putty could stop the cracks from spreading.

 

[Grehan]

Stress cracks, eh? The stanchion base you can see is part of a guard rail 'balustrade' that gets almost no use/action. Could expanding and contracting of the whole be at fault then?
And as noted, there are some other similar surface hairlines that are merely at change of surface direction - 90deg etc.
There is absolutely no indication of the GRP itself failing - very solid.

 

[30boat]

Stress cracks, eh? The stanchion base you can see is part of a guard rail 'balustrade' that gets almost no use/action. Could expanding and contracting of the whole be at fault then?
And as noted, there are some other similar surface hairlines that are merely at change of surface direction - 90deg etc.
There is absolutely no indication of the GRP itself failing - very solid.

As I said, leave it alone.If the laminate is sound and the fitting is well backed it's only a cosmetic problem.

 

[johnlilley]

Most likely hard spot cracks. Perhaps the underlying pad ends at the point of the longitudinal cracks & the stanchion has been flexed but the deck flexes or hinges at the "hard spot" of the pad edge.
Hammer testing the area will pick up any hard spot quite easily, just note the change in sound. It can also be the hard spot created by the cored deck (if fitted) as the outside of the deck goes into a single skin & any flexing occurs along the core edge like a hinge point.


John Lilley.

 

[Grehan]

. . and the best (easiest, most straightforward) way to deal with the cosmetic problem might be . . . ?

 

[johnlilley]

Firstly if it is a one off incident that caused the damage, then you might have to grind the gel coat away over the area & overlay a couple of thin laminates of epoxy resin & glass cloth, surface & carefully match in with two pot acrylic or similar. Not as difficult as you night imagine. Filling with gel coat filler is ok with singular cracks of no structural consequence but flexed areas will usually crack almost immediately & make the previous time & work wasted. The thin laminates over the cracks prevent the new finishes cracking.

Sometimes it can be due to lightweight construction if there are cracks in many places not subject to one off incidents & that needs a different repair ultimately.

There are some PDF articles & photos of SURVEY problems on my website exploring these problems in more detail if it helps.

John

 

[rivonia]

They are 100% stress cracks. Do not worry about them at all. Every single GRP yacht will get similar cracks eventually.

We had ours all proffessionaly repaired- Sanded down afilled and then sanded and eventually new gelcoat. Now looks like new.

Good luck.

Peter

 

[Medusa25]

I have seen these polished out with polishing compound I said he would not be able to do it 2 min's later he shouted me over and they were gone. They were caused by ramming into a jetty while docking and looked like a spiders web and were pretty bad.

 

[capsco]

They usually return once a little dirt gets back in.
IF NOT please let me know the make of the compound used.

 

[Egbod]

"Stress Cracks"

I was told a different cause-

Some cracks are from manufacture. The maker uses a big rubber hammer to help release the moulding from the mould. Some damage occurs. A white coating is applied (polish?). A year or two later- when out of guarantee- the cracks reappear.

Has anyone else heard this story? Is it true?

 

[Avocet]

I'd say they were stress cracks too. although that particular stanchion might not have seen any load, another one might have done. As the guardrail wires get pushed outwards, they can transmit the loads to the other stanchions in peculiar ways!

Also, they can take several months after the application of the original load to appear.

As has been said, reinforcing the laminate underneath, then grinding out and filling with pigmented gel would be the way to go, but getting a good colour match will be very tricky.

 

[Old Troll]

Wee cracks in the gelcoat

Please do not be hasty and dig too deep. On purchase survey of my present yacht there was great weepin and wailin and nashing of teeth about stress cracks etc. An estimate from the experts to carry out the work came to over £1000 so the surveyor said to ask for £2000 off the purchase which the seller finally agreed to. The wee cracks turned out to be shallow and cosmetic being gently sanded out by myself, a wee touch of gelcoat and paint to match. The total cost was about £10 plus the effort. Ordinary bath tile grout also takes out these wee cracks. What could be stressed about a stanchion unless you are towing the boat by it ? Go canny man and sand softly before the grinding and filling.

 

[Grehan]

No - with sincere thanks and respect to the 'stressers' I'm not stressed at all. I'm a lapsed architect and I know that this stainless steel 'balustrade' (it's not a stanchion plus life-lines yacht thing) is a very strong 3D shape bolted securely to some 'rock solid' GRP. Prompted this morning's postings I went out and gave it a bloody good shake - the whole thing moved not a miniscule millimetre.
I have been responsible for a few hull scrapes, but ain't never ploughed into anything head-first. Yet.
This is just a slightly irritating surface appearance thing - when I actually notice it !
I do however have a suspicion that age, plus shape, place original lay-up procedure, plus it being blinking hot here last summer and freezing cold last winter has affected the gel coat in a few (3 or 4) vulnerable places.
So there's no way I'm doing big job surface grinding or re-coating.
Would be nice to do a bit of 'touching up' making good though, just for vanity I guess.