Gelcoat pox (after blasting) - how to fill and fair before Penguard?

[dankilb]

If you blade smooth it over the dimpled surface there is zero shrinkage. Then put a coat of "the epoxy" over that during the overcoating window and you have you surface that doesn't need sanding with a minimum overcoating window (and no max). Quickest way to a good enough for underwater finish by far.

Yes, that's a very good point, thanks - not something that would have occurred to me otherwise.

The specified wet film for Penguard is 150-280 μm - compared to 80-150 μm dry. That's a lot of shrinkage, should I have attempted to use that as the 'fairing' coat over the pox also. I can see how this would undo any effort in 'blading' it on nice and fair in the first place.

Interestingly, studying the Gelshield Plus data sheet throws up a few other points, such as 'Contains no harmful solvents to migrate into the hull and cause reblistering'. I think I'm going to have to overlook this as I can't 'hot film' for the reasons mentioned. Plus quite a few people seem to have used Penguard (or Jotamastic) and - while I do know of at least one who had a breakout of small blisters a few years on, which could have been due to the paint (but were easily sanded back, re-painted, and are now fine) - most seem to have no issues.

I think the decision is made for me, then. I'll use West to fair the pox areas, but forgo any coat of non-solvented epoxy over the entire wetted area.

Yes, we hot coated with West with the 422 additive. There were three of us. One mixing, one rollering and one tipping off. As you said, hard work on your own. Will be interested to know how the Jotun Penguard works out for you as I have an upcoming project I could use it on.

Yup, I should imagine I'll get some assistance at various points, but just cannot rely on it - and it won't be 'skilled', meaning mixing up and roller painting the Penguard is likely to be more productive than the same with mixing, rolling and tipping 'proper' epoxy!

I do otherwise wish I could go down the West route, as the temptation to have whole sections done in a day is obviously great! West's isn't even that expensive, if you go for 30kg, and for what you get (i.e. the ability to do it properly in a day!).

I'll definitely post on here as and how it goes - once the weather and lockdown hopefully align.

 

[Elessar]

Yes, that's a very good point, thanks - not something that would have occurred to me otherwise.

The specified wet film for Penguard is 150-280 μm - compared to 80-150 μm dry. That's a lot of shrinkage, should I have attempted to use that as the 'fairing' coat over the pox also. I can see how this would undo any effort in 'blading' it on nice and fair in the first place.

Interestingly, studying the Gelshield Plus data sheet throws up a few other points, such as 'Contains no harmful solvents to migrate into the hull and cause reblistering'. I think I'm going to have to overlook this as I can't 'hot film' for the reasons mentioned. Plus quite a few people seem to have used Penguard (or Jotamastic) and - while I do know of at least one who had a breakout of small blisters a few years on, which could have been due to the paint (but were easily sanded back, re-painted, and are now fine) - most seem to have no issues.

I think the decision is made for me, then. I'll use West to fair the pox areas, but forgo any coat of non-solvented epoxy over the entire wetted area.



Yup, I should imagine I'll get some assistance at various points, but just cannot rely on it - and it won't be 'skilled', meaning mixing up and roller painting the Penguard is likely to be more productive than the same with mixing, rolling and tipping 'proper' epoxy!

I do otherwise wish I could go down the West route, as the temptation to have whole sections done in a day is obviously great! West's isn't even that expensive, if you go for 30kg, and for what you get (i.e. the ability to do it properly in a day!).

I'll definitely post on here as and how it goes - once the weather and lockdown hopefully align.

West is very viscous and very expensive. Better as a boat building adhesive or high strength area laminating epoxy IMO.
You could solvent free / blade the whole boat with gel shield + solvent free epoxy more successfully and for less.
Ps nice to have a discussion with someone who’s clever and listens even if we disagree.

 

[dankilb]

West is very viscous and very expensive. Better as a boat building adhesive or high strength area laminating epoxy IMO.
You could solvent free / blade the whole boat with gel shield + solvent free epoxy more successfully and for less.
Ps nice to have a discussion with someone who’s clever and listens even if we disagree.

Ha! Indeed, I'm all for discussions on here where expertise lead you to a different/better method. I've gone down the 'wrong' route with things like this in the past and, once you're committed, that's it - so it's a invaluable (sometimes literally!) to be able to consider and iron out any issues in advance. ?

I had good experiences with EasyComposites' 'EL2' laminating resin last summer. It's less than half the price of West's. It's noticeably less viscous. I actually used it partly to coat plywood - wish I had paid more attention to how long it took to gel/tack up, etc. (as it doesn't boast as much technical info as West's). I'd happily use this, once I can test out the timings to ensure I can get it on wet-on-tacky.

I will also seriously consider the potential of at least a few hot coats of non-solvent epoxy over the entire area. The First Mate is now well-rehearsed with epoxy work so between us I reckon we could do 1/4 sections of the hull at a time, in a day.

The cost issue is a tricky one. It isn't pure stubbornness around the cost of GelShield Plus, for instance. Funds are genuinely tight so any extra £££s spent on this can't be spent on other major jobs that need doing before re-launch.

Assuming 5L coverage for the wetted area (which I reckon is about right) and 3 coats would be:
GelShield Plus - £540
West - £450 (although unlike GelShield, West specify 5 coats, so if you did that it would be considerably more expensive)
'EL2' - £200

So a potential saving of £300+ would swing it for me - even in the knowledge that GelShield would no doubt be the best (and easiest - with all the technical/application info provided). But of course, if some money comes along or I can squeeze a margin elsewhere, I'll try. Or unless I'm radically under-estimating the coverage for GelShield, that is?