Epoxy coating; the master plan!

[pcatterall]

My hull had been slurry blasted by the previous owner removing much of the gell coat and leaving many very small imperfections. I have raised various questions about the way forward on this forum and had lots of useful advice ( the usuall element of contradiction of course!!) for which many thanks.

I read between the lines, produced a master plan and have commenced preparation, I would like to run this before the panel to test my plan and will really appreciate critical appraisal ( especially if based on real world experience!!)

To date I have sanded off all the remaining patches of gell coat, I then filled ( hemples) all the small holes ( lay up imperfections) and have sanded those down. Even though I thinned the filler ( MEK) and used my best 'polyfilla' techniques. There was still quite a bit of a film of filler to be sanded back for the small volume of filler in the holes.

I now have to plan the epoxy coating.
I will probably use West epoxy ( having read all the divided opinions) Yes the 5 to 1 mix (4.5 to 1 by volume) is awkward but gell times are ok and I hope to only need 3 coats to acheive the required thickness.
I have a few litres of 105 resin and some 205 catylist so I plan to do a test area of a few square meters to test the system and our techniques. If it goes pear shaped then all is not lost!! We plan to mix small quantities (300cc by volume) and roller on and tip off ( will try foam and brush tipping) We expect to be able to apply a second coat after 2 hours or so and the third 2 hours later ( testing 'tackyness' by the fingerprint/figernail/sticky as masking tape method!!) depending on temps this may run into a second day.
We will judge the thickness achieved by calculating the amount used by are covered with 1mm as the target. Before the last coat of epoxy hardens we plan to apply a first coat of antifoul. We are expecting to apply in tems not less than 15 degrees and start late morning when hull temps have stabillised.
We will be observing the usuall precautions, will watch for amine blush etc. We will be measuring the air and hull temps as we proceed.
Are there any reservations/ recommendations guys?
I note that I can pigment the 2nd and 3rd coats of epoxy and am considering this so as to finish with a white hull ( any comments on this)
Thanks for the advice to date and any comments on the above.

 

[Bosun Higgs]

My old prout cat was epoxied with west by a well run yard. even they has a problem with amine blush that required the boat to be peeled again a year later and re epoxied. And that was in mid summer and inside a shed which they heated to do the work. Plus we had a problem with fish eyes that had to be filled after coating. Conversely I did the next boat with blakes solvent free outside during a warm march and had no problems other than the golf ball dimpled finish left by the roller. I reckon that made the boat faster.

I would definitely not use west if doing the work outside.

I would not deliberately add pigment to the west though I seem to remember that when my boat was done, west advised adding their aluminium powder to improve water resistance.

In your position I would give thought to a layer of epoxy bound woven roving since you have no way of knowing how much if any of the laminate was removed in blasting. You cant assume that gelcoat left in patches means the rest of the blasting has only removed gel coat. By its nature blasting is much more difficult to control depth

 

[oldsaltoz]

You should also monitor the humidity, one of the causes of amine blush. Do not apply epoxy with humidity above 73%.

Take great care if using foam to level the resin, most foam types will break up and leave contamination behind, this will happen long before you see the foam failing and cause major problems if left to cure in the resin.

I use West Epoxy all the time, but the climate here in Oz is better suited, apart from the high humidity. I always delay my start till after 10AM to avoid the risk and even then only after I have checked the relative humidity.

I find it best to start at the top and roll down to the centre line in 6 to 8 inch strips, lifting the roller off and pulling more down as you go to get an even distribution, also make sure you have a small overlap on the last strip; have a second person tipping off with a fine long bristle brush and just glide over the surface. any sign of pulling indicates you need to reduce the width of the strips.

If you are going to add a pigment, make sure it not permeable and can not absorb any moisture in any way.

Also ensure you take the volume added into account when adding your hardener, you will need less.

A small set of scales is the best measuring device, though I have never had a problem using the West system pumps, as long as you look after them and keep them clean they are fine.

Start on the sunny side and close the boat up so the shady side has time to warm up.

Hope this helps.

Good luck.

 

[captainscott]

Epoxy coating; the master plan

There is one person who will talk you through any problems of this nature, Tony Grimes has had 50 years experience in epoxy \ sythetic resin products and is always pleased to advise fellow boaters. His email is
info@c-guard.co.uk , his company is Benring Ltd, Quarnford, Buxton, Derbyshire. SK17 0TG Tel 01298 74026 (They are by appointment to HM the Queeen as suppliers and consultants of Sythetic and resin products so they know their stuff) Hope this helps.

 

[prv]

Keep your mixed epoxy spread out in a tray (those plastic takeaway ones are good) so that the heat can escape. Otherwise it will go off much quicker than you expect, sometimes scarily vigorously (with smoke, melting cups, etc).

I'm surprised that it's OK to apply antifoul straight onto partially-cured epoxy, although I don't have any firm knowledge on the matter.

Pete

 

[vyv_cox]

(They are by appointment to HM the Queeen as suppliers and consultants of Sythetic and resin products so they know their stuff) Hope this helps.

Who would have thought the Queen epoxied her own boat? What's she sailing these days?

 

[pcatterall]

Yes prv; I've done the melting cup business!! even a tin tray in a water tray is recommended. The antifoul direct onto 'green' epoxy comes from 'gellshield' and from other contributions on the forum. Of course this is a trial, so not the end of the world ( but of course I wont understand the long term implications from the trial)
Just a bit concerned about Bosun Higg's sorry tale ( the Prout)
but I would have thought that a competant yard would have spotted amine blush and cleaned it off before the next coat?

 

[oldsaltoz]

Keep your mixed epoxy spread out in a tray (those plastic takeaway ones are good) so that the heat can escape. Otherwise it will go off much quicker than you expect, sometimes scarily vigorously (with smoke, melting cups, etc).

I'm surprised that it's OK to apply antifoul straight onto partially-cured epoxy, although I don't have any firm knowledge on the matter.

Pete

I have often applied an epoxy primer over tacky epoxy resin, this makes for a hard surface when cleaning off antifoul at a later date.

 

[Bosun Higgs]

Blakes certainly recommend painting with primer whilst the epoxy is still green.