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[barriew]

Bunkerbarge

I had a similar problem with a hull I had coated with Isopon Resin (from Halfords) - but only in places. In fact I had problems getting the resin to harden fully - it took for ages in places, those places where the primer crackled.  When it did eventually all go off, the primer eventually 'took'.

Barrie

[Stavros]

Right Stav lot the rescue,as the lads have said there is no way you will have an easy time of it my friend,my reccccomendations are as follows
1 Wet/dry hull with 180 grit to remove ALL traces of primer
2 Go to a MOTOR factor that sells paint and but either 3M or Bodyline adhesion promoter for plastic bumpers etc
3 Whilst there but some proper car trade primer aerosol
4 use adhesion promoter first DO NOT RUB THIS PRODUCT DOWN allow to dry usually 20mins than immediately apply primer 22 light coats
5 Rub primer down when dry with 400 or 600 wet/dry
6 Reprime 2 coats.When priming DO NOT UPON PAIN OF DEATH APPLY HEAVILY or you will feel suicidal as it will crack again
7 Rub down  primer DRY YES DRY with 800 grit wet6 dry and apply colour coats 2 coats max rub down 1000 wet dry WET and apply 2 or 3 coats of topcoat but not heavy ones

The main reason for paint cracking is simple primer coats applied too thick and the previous coat has not had sufficient time to dry,reason for cracking is solvent trapping the previous coat TA TA for now Stavros

[John W E]

Hi All

Bunkerbarge, the resin you used on your hull - if it was bog standard layup resin, did you allow enough time for it to cure properly roughly about 24-48 hours to cure right off, at the correct room temperature and everything?   Also, did you rub/sand it back to give the paint a good  key??

BarrieW - the symptoms you are describing used to be quite common in full sized hulls building when you got the mix of resin to hardener wrong.   However, presumably we are dealing with a small hull, where one mix of resin and hardener would be sufficient to coat the whole hull in one go.  So, therefore, it points to two other possible causes:

1.  Your can of resin has been standing on the shop shelf for a long time and the additives in the resin has started to separate and go to the bottom of the tin (there are accelerators/thickening agents in resins) which if left for over a period of time, will settle the bottom of the can.   This is why its always adviseable to warm the resin up by putting the can in a bowl of warm water, and then shaking the can vigorously and stirring for a good 20 minutes.

THE ONE I REALLY SUSPECT THOUGH is
2.  Contamination of the timber that the hull is made from - being either grease or having oil on it, or you may have used an oily timber e.g. teak to build the hull from.   The hull should have been washed down in acetone thoroughly (not saying that you didn't do that) then straight after the acetone has evaporated off the hull, start applying your resin.

Hope that helps
aye
John E
BLUEBIRD

[sinbad]

Thanks to DickyD for your help on the supply problem.This could be a very helpfull forum.
Cheers.
Sinbad

[Bunkerbarge]

I think I have just gone through exactly what Barrie was describing in so far as the Halfords Isopon Resin does not seem to be completely cured.  It seems dry to the touch, and has now had about 6-7 days, but, if you press your finger into it you leave a fingerprint so it is obviously not completely hardened.  I only gave it a very light dusting with the Halfords primer which then proceded to split on the surface so there was obviously some reaction. 

I suspect I should have waited for as long as was required for it to completely harden then rub it with wet and dry to key the surface.

Anyway an interesting post script to the story. 

I was browsing B&Q this afternoon when I noticed a tin of wood primer that caught my eye.  It is supposed to be for external wood treatment and made all sorts of promises, as usual.  Anyway as I was looking at somehow stripping the whole lot off  the hull again I thought what the hell, lets give it a try.  When you open the tin it looks like metallic paint, although it is described as grey, and paints like a very matt silver.  Time to read the tin thoroughly!!  Apparently it contains aluminium particles to completely waterproof the wood surface ready for a top coat.  I tried it on the hull and not only did it cover the cracked surface perfectly but it also left a beautufully matt surface to key a top coat to.  I was absolutely amazed and very pleased as I have just saved myself a lot of work and I have a very nice primed finish for the top coat.  Being a wood sealant as well should lend itself to a few usefull applications in the model boat field so I will be looking forward to using it again.

[Colin Bishop]

Bunkerbarge - Isopon is polyester resin and it will always stay tacky due to exposure to the oxygen in the air. Apparently you need to add some wax to it it ensure it cures fully. I don't think epoxies suffer from this. By managing to ovecoat it with something that "sticks" without crazing it will probably go off underneath and you should be OK.

I have been using epoxy today to treat the leaky areas on my full size boat and it has cured very well - on the boat, on my hands, on my clothes, on anything I've touched..... ::)

[rats]

 Do you have the make of primer Bunkerbarge - sounds like useful stuff !

[bigfella]

Hi All

.......and I thought that the painting would be the easiest part now I find that all these pitfalls will befall me. I had visions of a stress relieving slow brush up and down and now I find I may have to find some Valium.

Regards Bigfella

[bigfella]

................................................Hey I just got a promotion to a CPO

[Colin Bishop]

I think Bunkerbarge is using standard aluminium wood primer - I've got some made by Blackfriars. It says on the tin that it is particularly useful for resinous woods which probably accounts for the success Bunkerbarge has had with it.

[DickyD]

Back in the dim distant past when I was working we used to use aluminium primer on hardwood because it was unaffected by the sap in the timber.
As you might have noticed if you leave hardwood untreated in the sun the surface will soon become covered with beads of sap. It would still happen with ordinary wood primer but not aluminium.
Probably same with resin.
Dont need it with epoxy though.

Richard

[kayem]

Bunkerbarge - Isopon is polyester resin and it will always stay tacky due to exposure to the oxygen in the air. Apparently you need to add some wax to it it ensure it cures fully. I don't think epoxies suffer from this. By managing to ovecoat it with something that "sticks" without crazing it will probably go off underneath and you should be OK.

No, that's not right at all, I'd have thought an Admiral would know better. If Isopon hasn't set fully within half an hour or less, it isn't going to. Either the stuff is well past its sell-by date, or the hardener is, or you haven't used enough of the hardener. Depending on temperature or humidity, there can be some very slight surface tackiness after it sets, but again this usually indicates old stock or more probably insufficient hardener. Never use old polyester materials of any kind, it just isn't worth the risk, they all lose their reactivity over time. If it's still soft after 6-7 days, you're just going to have to strip it all off and start again. Painting anything at all on top of unhardened Isopon, P38, Plastic Padding or any similar material, is only going to make the problem worse.

[Colin Bishop]

Kayem, you may be right up to a point but there are issues with polyester resin not surface curing by design which is why I was using epoxy on my full size boat today. I certainly accept your point about old stock and resin/harder ratio.

This is a typical result I found from Googling before I made my post which sums things up quite well:

There are two types of polyester resin to be found. Finishing resin (or waxed) and Laminating resin (unwaxed). What is the difference? - glad you asked. When you add catalyst to polyester resin, it starts a chemical reaction that generates heat. This reaction, and the heat are what causes the resin to kick (harden).

But polyester resin will not kick fully to the touch (not tacky) without some help. The finishing or waxed resin contains a small amount of wax. The heat causes the wax to raise to the surface and deprive the resin of oxygen. It is this deprivation of oxygen that causes resin to kick to the touch without a tacky feel.

This is why a finishing resin must be sanded or cleaned with an acetone wipe before painting. The wax must be removed or there will be adhesion problems.

Laminating resins on the other hand, contain no wax, and will remain tacky, but require no cleaning before you can apply something else - like more resin or fiberglass. Now,,, this is not to say that you cannot get an unwaxed resin to kick. Although I have not tried it myself, I have heard of people using cellophane to finish the kicking process. A bubble free application of cellophane over an unwaxed resin will complete the kicking process. Just peel the cellophane away and you're done.

Using this cellophane kicking method you can skip the sanding or acetone wipe to remove the wax layer - a very messy job wether you sand or use an acetone wipe.

Also, you should always strive to use fresh resin and catalyst. This stuff is cheap, so don't trust that old can that's been in the garage for years. Whether you are applying fiberglass or waterproofing wood, use fresh polyester resin and catalyst.

[HS93 (RIP)]

Granny eggs come to mind??

[Colin Bishop]

It's the wide range of opinions that make this Forum what it is!  Just pick the solution that suits you as FLJ would say.

I didn't realise until the other day that there are two types of grp cloth. One with an emulsion binder for polyester resin and one with powder binder for epoxy. I did know that you can put epoxy over polyester but not vice versa though.

[bigfella]

Hi All


I think that the more information that everyone posts and shares (even contradictory) the better for the forum. Its no use having the key to life the universe etc and not sharing it.

Regards Bigfella

[kayem]

This is a typical result I found from Googling before I made my post which sums things up quite well:

Colin, there is some truth in what you say, but you're oversimplifying the curing process. Finishing resin is nothing more than laminating resin with an additional wax additive, though usually with a slightly lower viscosity, it's quite simple to make your own, which I do all the time. In over 30 years in the reinforced plastics industry, I've never heard the 'kicking' term you refer to, but I suppose you learn something new every day. Also, most modern resins are 'Low styrene emission' by EEC edict. This means essentially that they contain quite a lot of wax to contain the styrene within the laminate during the reaction process, try walking over the cured inside of something like a modern Sunseeker hull if you don't believe me, you'll need to hold onto something to avoid going A over T. Also, in the trade, surface wax is only removed by abrasion, I've never heard of a solvent being used, partly EEC regulations again, but you wouldn't want anything more than minimal exposure to solvents on a GRP moulding that you wanted anyone to pay you for. I don't know what type your boat is, but some years ago it's possible that I could have been running the quality control department in the company that made it.

[DickyD]

Hi All


I think that the more information that everyone posts and shares (even contradictory) the better for the forum. Its no use having the key to life the universe etc and not sharing it.

Regards Bigfella

Good grief he's gone over the edge.

[Colin Bishop]

I realise that we have experts on the forum and that they can be relied upon to tell us the proper way to do things and I very much value their advice - more power to their elbow and certainly something I would normally follow. However, there are sometimes shortcuts in particular siituations and it looks like maybe Bunkerbarge has chanced on one. Logically something which "binds" to the tacky surface and gives a firm surface finish could solve his problem and maybe in this case it has done so. It may not be the "proper" way to do things but what the hell! Bunkerbarge has liost nothing by trying it. If it doesn't work then he can still revert back to plan A, albeit at considerably more effort!

[Colin Bishop]

Kayem, just seen your latest post.  I was just quoting one of a number of sources I found on the Net which say the same thing and which accord with comments I've heard from other people. I'm quite happy to bow to your superior knowledge as per my post above. What works for Bunkerbarge obviously wouldn't be appropriate on a Sunseeker. I'm afraid my boat is quite ancient, 1983, when I doubt if anyone would know what the phrase "quality control" meant. In those days they just seemed to chuck the materials in and double up for luck. So there's quite a lot of material but the finish and engineering is pretty crude by any standards (bit like my modelling really!) Full size boatbuilding today is a different kettle of fish altogether.

Do you think Bunkerbarge's solution will work or will the top finish fall off within a week or so? No doubt he will keep us posted!

[kayem]

Again, there is much truth in The Admiral's most recent post, there's often more than one way of getting a satisfactory result, and often it isn't something that would be approved of by 'experts'. We all discover our
own useful short cuts through experience, and it's rather easier to experiment on a 3 foot model than a 46
foot full size boat. I've dealt with many big names in the GRP industry over the years, and I've found that they sometimes cover themselves against possible comebacks by issuing instructions that are virtually unachievable in any real-world business that has to turn a profit to survive, and this also applies to a lot of what you might find on the Internet. Most of us do our best but we often have to make compromises. One of the largest UK GRP materials supplying operations publishes useful literature that I've often referred to over the years, but they assume a standard of perfection in things like workshop temperature, humidity control, mixing ratios etc, that cause ripples of mirth among most professionals who read them. If you phoned them with a problem of some kind, they always came out with something along the lines of, "Well, if you aren't following all our recommendations to the nth degree, we can't be held responsible, is every inch of your workshop maintained at a steady 17.5 degrees?" As Eric Morecambe might have said, "There's no answer to that".

I was touched by Colin's use of the term 'superior knowledge', but we're all modellers together here. On the other hand, I certainly wouldn't try to tell him (or anyone else for that matter) anything much about proper sailing. On boatbuilding practices generally in the full-size industry, standards are generally pretty high in anything but the smallest craft, and they have been since much earlier than 1983. Lloyds Inspectors keep a pretty close eye on most aspects of the manufacturing process, and if you didn't get a Lloyds Certificate, any vessel would be virtually impossible to insure.

I have to disagree strongly with Colin's posts on one thing though, if anything polyester, resin, filler or anything else, hasn't hardened fully in a fraction of the 6 to 7 days mentioned, you're wasting your time going any further. I'm afraid that you have no option but to strip off all the unhardened material and start again. If it's still soft after a week, that's the way it's going to stay.

[Colin Bishop]

Fair comment Kayem, and thank you. Very informative. Your comments about conditions of use will strike a chord with anyone who has been stuck under a boat in the middle of winter cursing the fact that the filler won't go off because it needs a bright sunny day which won't come before May by which time you should have been afloat for the last month! Which is why you tend to see a frenzy of crazed activity around boatyards in the last week of March! (and why I spent today epoxying given the prospect of next week's weather forecast)

[Bunkerbarge]

Thanks for all the interesting inputs gents.

I'll let you know how the process goes but so far it appears promising.

By the way the primer was B&Q's own brand, I'll get the specific name tomorrow but it seems to be an interesting product.

[bigfella]

Hi Dickyd

Down under you cant but go over the edge :-\ :-\, lets face it in Oz all you have is edge's and we are just clinging to them, what with the drought if you go inland for about  100km all you get is desert. Believe me 100km is nothing out here. Infact it has come to the stage in the drought that our State Govt has made the decision that we will be drinking our own sewerage (treated I hope).

Regards Bigfella

[HS93 (RIP)]

 bigfella

Infact it has come to the stage in the drought that our State Govt has made the decision that we will be drinking our own sewerage

We have been doing that for years over hear, Its prob the reason for some of the posts.

Peter