Filling fine cracks on deck.

[eddystone]

I think the time has come for a more systematic refurbishment of the deck. The major part is non-slip which is relatively straightforward as I'll be using Kiwi Grip. The problem areas are the fine cracks which occur mainly in the vicinity of right angles or curves. I have used Magic Ezy in the past without much success The larger ones I aim to open out with a Dremel and fill but this is impractical in small areas where there is a mass of ultra fine lines. I thought about sanding back a bit and then skimming over with flowcoat. Trouble is I don't know how to make flowcoat. What does one mix with gelcoat to give it the required viscosity?

The other problem is brown stains from bird droppings. I've tried most things including oxalic acid (Y10) without success.

 

[C08]

The best thing I have come across for brown marks from bird droppings is starbrite rust removal spray. Although designed for rust stains itworks better in my experience than oxalic acid or Y10 and half a dozen other potions that did not work as well

 

[PaulRainbow]

If you want flowcoat, buy flowcoat, not gelcoat. Adding wax to gelcoat makes it into flowcoat, but it thins it too.

 

[Bobc]

Before going too mad, just try opening a few out a tad with a dremmel, then scrape some gelcoat filler into them and then rub it back flat with some 600 grit.

 

[jwilson]

IMHO unless you reinforce and stiffen the whole area (normally from underneath) dremelling out fine gelcoat cracks and filling is a waste of time - they will recur, as stress cracks near edges/sharp curves are inherent in the nature of the composite with more flexible glass/resin and more brittle gelcoat.

If it is a one-off star crack or similar from single impact damage it should work.

 

[TQA]

IMHO unless you reinforce and stiffen the whole area (normally from underneath) dremelling out fine gelcoat cracks and filling is a waste of time - they will recur, as stress cracks near edges/sharp curves are inherent in the nature of the composite with more flexible glass/resin and more brittle gelcoat.

If it is a one-off star crack or similar from single impact damage it should work.

+ 1

 

[eddystone]

Thanks for replies and tip on starbrite rust remover.
I only intend to dremel out a few that are a bit wider, mainly in the curve of the coaming to side deck and coaming to cockpit seat; also in those areas the matching (it won't!) isn't too important. None of them are impact cracks, they are all stress lines.
I think rather than flowcoat (is that a separate product?) I just need to thin out gelcoat so that I can skim it like domestic fine surface filler - as I understand it you can do this by adding wax although Plastic padding gelcoat filler already has wax added so that it cures in air and that is too thick/sticky.

 

[PCUK]

The amount of wax required will not make much difference to the thickness. Warm the resin before adding hardener and wax as this will thin it, then apply it very rapidly as the warmth will speed the cure.

 

[PaulRainbow]

Gelcoat is thickened so that you can apply a decent thickness coat. Thinning it, adding wax and thinning it, heating it to thin it is daft. It'll have consistency of piss and be about as much use.

Flowcoat of the correct thickness can be applied thicker and as it takes time to cure it will flow out. Thinned stuff will be somewhere other than the place you want it before it half cures.

Flowcoating over stress cracks is a waste of time. In fact, filling over any cracks is a waste of time. Dremelling cracks slightly wider is a waste of time. Most will come back, all will be ugly and colour mismatched. You need to sand an area of gel off and taper the edges.

 

[jwilson]

snipped - Flowcoating over stress cracks is a waste of time. In fact, filling over any cracks is a waste of time. Dremelling cracks slightly wider is a waste of time. Most will come back, all will be ugly and colour mismatched. You need to sand an area of gel off and taper the edges.

And reinforce the structure substantially so in that area it doesn't flex - it's the flexing that causes the cracks. You can't easily do this from the top...... Or accept the cracks. It's a very rare or very new GRP boat that doesn't have some stress cracks near corners/sharp curves.

 

[eddystone]

And reinforce the structure substantially so in that area it doesn't flex - it's the flexing that causes the cracks. You can't easily do this from the top...... Or accept the cracks. It's a very rare or very new GRP boat that doesn't have some stress cracks near corners/sharp curves.

TBH its not the cosmetic aspects that worry me just the possibility of moisture getting into the boundary between the gelcoat and underlying laminate. Perhaps the answer is to leave as is until there is an area worth grinding back and filling. I will carry out experiments on my wife's Comet hull which has large areas of star cracking/spider cracks on the underside due to her landing technique.

 

[Poey50]

TBH its not the cosmetic aspects that worry me just the possibility of moisture getting into the boundary between the gelcoat and underlying laminate. Perhaps the answer is to leave as is until there is an area worth grinding back and filling. I will carry out experiments on my wife's Comet hull which has large areas of star cracking/spider cracks on the underside due to her landing technique.

Keep us posted eddystone as I'm pondering the same issues for a deck repaint in Feb / March.