gelcoat cracks near shroud anchors

winsbury

winsbury

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We have found some cracks in the gel coat near the shroud anchor points on an inside radius of the molding. This had been painted over by the previous owner hence I didn't notice this when I bought the boat; the paint has flaked off over the winter so they are now quite evident. While they look worrying there is no discernible flex in the deck in the area; there is a substantial amount of original strengthening below the deck to spread the load; no evidence of water penetration and the shrouds are maintaining their tension so I don't think this is structural (yet.)

My feeling is because its an old boat the gel is now quite brittle evidenced by some crazing and chips elsewhere so a combination of age , weathering and tension in this part of the deck perhaps exacerbated by the curve in the molding has caused the gel coat to crack rather than any serious breakdown in the core or skin.

I'm thinking of sanding old paint off, opening the cracks to a V shape with a dremmel then fill void with epoxy and repaint the surface rather than attempt a gel coat match.

Before I do this, does anyone have any other comments or suggestions how best to make good ?
 
A lot depends on the exact configuration of the shroud plates, but most are actually anchored to the hull or an internal bulkhead. Wher the tang pierces the deck, it is normal to have a flange bolted down over mastic to prevent ingress of water, but it has no structural strength. Unfortunately the flange is welded to the tang rather than being allowe to float freely with movement. As the rig moves, the tang flexes and can promote crazing of the gelcoat or worse. As long as you're sure that the deck is not being stressed under load, your proposed course of action should prove effective for a number of years, though it will recurr eventually.

Rob.
 
winsbury said:
We have found some cracks in the gel coat near the shroud anchor points on an inside radius of the molding. This had been painted over by the previous owner hence I didn't notice this when I bought the boat; the paint has flaked off over the winter so they are now quite evident. While they look worrying there is no discernible flex in the deck in the area; there is a substantial amount of original strengthening below the deck to spread the load; no evidence of water penetration and the shrouds are maintaining their tension so I don't think this is structural (yet.)

My feeling is because its an old boat the gel is now quite brittle evidenced by some crazing and chips elsewhere so a combination of age , weathering and tension in this part of the deck perhaps exacerbated by the curve in the molding has caused the gel coat to crack rather than any serious breakdown in the core or skin.

I'm thinking of sanding old paint off, opening the cracks to a V shape with a dremmel then fill void with epoxy and repaint the surface rather than attempt a gel coat match.

Before I do this, does anyone have any other comments or suggestions how best to make good ?
Click to expand...

To give yourself some certainty as to what is going on I would remove the gelcoat in the effected area to see what condition the GRP is in. In my experience, the cracks in gelcoat often extend into the glass beneath. If they do this then you would be wise to grind back the cracks in the glass and layer in new glass cloth. Once you have done this and worked out why this is happening and strengthened as required you would then fill and fair with an epoxy filler before painting.
If you just repair the gelcoat and you do have crackers underneath, the cracks will come back in no time
 
Vallich: that Magicezy stuff looks interesting for hairlines and hadn't come across it before; mine are a bit bigger than hairline and contaminated with paint from the previous owners attempt to hide them so not sure it would be ideal. I noticed some You tube videos say it shrinks 50% upon drying which seems counterproductive for a filler.

rob2: I think you're right and that's exactly what originally caused it : The cap shrouds are connected to a U bolt at the end of a heavy duty chain plate that is secured to the bulkhead so it doesn't rely just on the deck to support the mast. The front and rear stays are also terminated on U bolts which go through the deck to a long load spreader.

geem: clearly that's good advice but exactly the kind of repair I'm hoping to avoid, for this season at least. It would be a pig of a repair to make look good because it would affect the non-slip portion of the deck as well as several compound curvy bits hence would much prefer to do a smaller repair to see if it will work even if only for a few years.
 
Just about every boat I have had has a few small hairline cracks in the gel around the shrouds. A quick check underneath to ensure nothing is a miss then slap more paint on and forget about it. You spend along time worrying about every small defect on a boat.
 
It is very common for cracks to appear on inside radii - my boat has loads of them. It happens because when the boat is being manufactured extra layers of gelcoat are applied at these points, which in the mould are outside radii, so that it does not slump away and expose the subsequent layup. The thicker gelcoat is brittle by comparison with the GRP, so when minor flexing occurs in service it cracks. The same thing can happen on some outside radii, which in the mould are inside ones, accumulating gelcoat that slumps into them.

This may well be less of a problem with modern production methods but was common with older layups where everything was done simply.
 
A simple tip that may reassure you.
Get someone to pull horizontally the two opposing shrouds together at around head height (yup it can be done unless a very big boat, highly tuned).. And simultaneously watch the cracks and deck at the same time to note any/minimum/some /excessive distortion or flexure. If you lay a straight edge on the GRP you may ' see' any deflection..
Interpreting just what you do see though, is always somewhat subjective..

Chances are, though, you aint gonna lift the deck or shroud mounts off !

( Once you're out sailing hard on the wind, then is the time to watch the rig and hull interact, to note and mast compression or creakings and overly slack lee shrouds)

Now snap off a hacksaw blade and gouge a square groove in the cracks that offend you, aplly the filler if your choice, flatten with the edge of a cabinet scraper ( a hand sized, pliable thin bit of sharp edged, square steel )

And go sailing...
My two pees worth for an older, hand painted GRP boat
 
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