Blacking over Comastic with cheaper bitumin.

[casper ghost]

When I first blacked my boat I used Comastic, and have re-coated it a few times. I asked on here a while ago about over painting with bitumin and I was told that you can paint over cured comastic with bitumin but not the other way around, but I used Comastic then anyway. Now i'm goind into dock again and Comastic is getting dearer than ever. I've just asked spencer coatings whether they think I can paint their Intex 2 Bitumin over Comastic. Their response was that their Intex 2 is not suitable to paint a hull. Now i've seen this for sale at a Chandlery who are selling it as hull paint.. They also said it's not good to paint over Comastic with another paint, but maybe they would say that as Comastic is dearer.

 

They say Intex 2 is for painting steel posts etc, that are to be buried in the ground, sounds ideal for a boat hull...?

Casp'

Edited March 21, 2013 by casper ghost

[Ex- Member]

To be honest forget bitumen, it really isn't fit for purpose. And then applying it on a surface that might not accept it makes less sense still.

 

That Comastic is pricey £60 for 5 litres, I really wouldn't bother with that either when you can ge 2 pack applications for a ball park similar price with much better protection. I would go for something like Jotamastic 87 which might well cover Comastic, will need checking out though. Plenty of other 2 pack hull paints out there.

 

ETA I think Blackrose frequently uses Jotamastic 87, he'll know better than me. Or go to

 

http://www.jotun.com...55!OpenDocument

Edited March 21, 2013 by Julynian

[bizzard]

Well I'd say no! don't forget bitumen!, applied properly according to the instructions ect ect and not rushed to do the job in 2 or 3 days like a great many folk do will last pretty well actually. My boat hull for example originally had Comastic on it and on my first docking I put Rylard premium bitumen on and it took to it beautifully. Subsequent dockings I have used the same bitumen. Last docking was last August after a lapse of ''5 YEARS!!!'' and really there wasn't really any need after all that time, it would have gone another couple of years easily before any significantly wore off. My boat is used regularly summer and winter twice a week ice permitting for shopping and the odd breakdown callout and longer trips during the summer sometimes in an often fastish flowing river with plenty of debris clouting the hull. My all in DIY docking cost last August was £264.

You may even discover Julynian that your 2 pack Jotun stuff might not be fit for purpose for some reason when your boats in the water.

[Ex- Member]

Well I'd say no! don't forget bitumen!, applied properly according to the instructions ect ect and not rushed to do the job in 2 or 3 days like a great many folk do will last pretty well actually. My boat hull for example originally had Comastic on it and on my first docking I put Rylard premium bitumen on and it took to it beautifully. Subsequent dockings I have used the same bitumen. Last docking was last August after a lapse of ''5 YEARS!!!'' and really there wasn't really any need after all that time, it would have gone another couple of years easily before any significantly wore off. My boat is used regularly summer and winter twice a week ice permitting for shopping and the odd breakdown callout and longer trips during the summer sometimes in an often fastish flowing river with plenty of debris clouting the hull. My all in DIY docking cost last August was £264.

You may even discover Julynian that your 2 pack Jotun stuff might not be fit for purpose for some reason when your boats in the water.

 

Well if its good enough for international shipping it's good enough for me. My experience of bitumen on all the boats I've observed coming in to this yard over the pas 5 years it that it isn't fit for purpose. The main reason being that at the waterline where the most protection is required it the area that bitumen is at it's most vulnerable, and that is from floating fuels oils & debris. Bitumen is also soft and easily scraped and scratched.

 

When our boat was delivered new it had been applied with 2 coats of bitumen. My dear now departed dad applied another 3 coats of the stuff prior to going on the water, so this was well cured prior to launch . We wen't on the water for nearly 2 years, when the boat was removed, the majority of bitumen at the waterline was non existent and a line of rust about 2 inches either side of the waterline was clearly visible. On the bow and stern many areas of bitumen had been scraped through to metal, fortunately only minimal rust but another year in the water and it would have been a lot worse. hat was with 5 coats in total 3 of which were applied thickly by mohair roller.

 

I've seen numerous older boats come into this yard and every one painted with bitumen has suffered severe corrosion at the water line. Added to that simple jet washing disperses old bitumen only to find rust underneath it.

Edited March 21, 2013 by Julynian

[casper ghost]

Why would Spencer say their Intex 2 Bitumin isn't suitable for boat hulls?

Casp'

[bizzard]

Well if its good enough for international shipping it's good enough for me. My experience of bitumen on all the boats I've observed coming in to this yard over the pas 5 years it that it isn't fit for purpose. The main reason being that at the waterline where the most protection is required it the area that bitumen is at it's most vulnerable, and that is from floating fuels oils & debris. Bitumen is also soft and easily scraped and scratched.

 

When our boat was delivered new it had been applied with 2 coats of bitumen. My dear now departed dad applied another 3 coats of the stuff prior to going on the water, so this was well cured prior to launch . We wen't on the water for nearly 2 years, when the boat was removed, the majority of bitumen at the waterline was non existent and a line of rust about 2 inches either side of the waterline was clearly visible. On the bow and stern many areas of bitumen had been scraped through to metal, fortunately only minimal rust but another year in the water and it would have been a lot worse. hat was with 5 coats in total 3 of which were applied thickly by mohair roller.

 

I've seen numerous older boats come into this yard and every one painted with bitumen has suffered severe corrosion at the water line. Added to that simple jet washing disperses old bitumen only to find rust underneath it.

Its just your continual knocking of bitumen which is really not that bad at all. New hulls are often not de mill scaled properly or not at all before the builders slap quite often just one coat of bitumen on, its the very first coat that counts as with any painting as to whether subsequent coats of paint hold up and are durable, usually the trouble with painting anything with any paint. Bitumen is only soft if the drying times are not strictly adhered to or too many coats put on at one docking, more than three and it won't really dry throughout unless let to dry for several days before refloating.

Electrolosis I would imagine will zap and pit a 2 pack painted boat just the same as a bitumen painted boat, and depending where you moor and the extent and power of all your and other folks electrics periods between dockings with 2 pack paint could be just as regular as with bitumen paint or if only for new anodes.

[Timleech]

Why would Spencer say their Intex 2 Bitumin isn't suitable for boat hulls?

Casp'

 

No idea, but their usual recommendation for painting over weathered tar paints is Rytex.

 

Edit to add comment on julynian's post - a lot of new boats are sold with blacking directly onto the millscale, no effort having been made to remove this. They will quickly shed the blacking around the waterline, either because it doesn't hold well to the glassy surface of the millscale or because the millscale is starting to shed from the steel, or probably both processes. Boats in this category need blacking more frequently than those which have been properly prepared or are more mature.

 

I agree that bitumen is not ideal, coal tar products are generally longer lasting but they carry greater elfinsafety and environmental baggage.

 

Tim

Edited March 21, 2013 by Timleech

[Ex- Member]

Its just your continual knocking of bitumen which is really not that bad at all. New hulls are often not de mill scaled properly or not at all before the builders slap quite often just one coat of bitumen on, its the very first coat that counts as with any painting as to whether subsequent coats of paint hold up and are durable, usually the trouble with painting anything with any paint. Bitumen is only soft if the drying times are not strictly adhered to or too many coats put on at one docking, more than three and it won't really dry throughout unless let to dry for several days before refloating.

Electrolosis I would imagine will zap and pit a 2 pack painted boat just the same as a bitumen painted boat, and depending where you moor and the extent and power of all your and other folks electrics periods between dockings with 2 pack paint could be just as regular as with bitumen paint or if only for new anodes.

 

I can't see any problem in continually knocking a product that clearly isn't fit for purpose, I'm sure the OP will be able to make a choice that suits him/her but nothing I have stated is incorrect, so I don't see the problem.

 

At the end of the day as stated bitumen is at it's most vulnerable in the place where it's is needed most. On just that basis it's unfit for purpose.

 

Where the bitumen disappeared from the waterline on our boat was nothing to do with millscale, it was due to bitumen dissolving at the waterline due to floating oils, fuels & debris.

 

If a screw has no thread it isn't fit for purpose, you can still hammer it in though.

[bizzard]

No idea, but their usual recommendation for painting over weathered tar paints is Rytex.

 

Edit to add comment on julynian's post - a lot of new boats are sold with blacking directly onto the millscale, no effort having been made to remove this. They will quickly shed the blacking around the waterline, either because it doesn't hold well to the glassy surface of the millscale or because the millscale is starting to shed from the steel, or probably both processes. Boats in this category need blacking more frequently than those which have been properly prepared or are more mature.

 

I agree that bitumen is not ideal, coal tar products are generally longer lasting but they carry greater elfinsafety and environmental baggage.

 

Tim

Isn't Rytex just the dearer version of Rylards premium. I think it was Rytex I was asked to use on someones boat a few years ago, It was quite viscous and sort of plasticy to apply, I wasn't keen on it. They say it doesn't seem to last any longer than the premium. The premiums tin says on it that it contains ''Gilsonite'' whatever that is. Something to do with fishing boat net derricks ?.

[Timleech]

Isn't Rytex just the dearer version of Rylards premium. I think it was Rytex I was asked to use on someones boat a few years ago, It was quite viscous and sort of plasticy to apply, I wasn't keen on it. They say it doesn't seem to last any longer than the premium. The premiums tin says on it that it contains ''Gilsonite'' whatever that is. Something to do with fishing boat net derricks ?.

 

No, Rytex is a different product, closer to Sealex. It gives a duller finish. Premium contains 'Gilsonite' which I think is a naturally occurring product, it's supposed to give an enhanced resistance to washing off by solvents, diesel etc.

 

Tim

 

Edit - Gilsonite

Edited March 21, 2013 by Timleech

[bizzard]

No, Rytex is a different product, closer to Sealex. It gives a duller finish. Premium contains 'Gilsonite' which I think is a naturally occurring product, it's supposed to give an enhanced resistance to washing off by solvents, diesel etc.

 

Tim

 

Edit - Gilsonite

Thanks Tim. So nothing to do with fishing trawler net winches. Gilsonite mined and all the way from Utah too and used on model T Fords 100 years or so ago. The Rytex did have a sort of dark grey ''rather than pitch black'' satin finish.

[Speedwheel]

Hot pitch and tar?

[Timleech]

Hot pitch and tar?

 

I haven't bought any for some years, but I'm told that the price of painting tar has gone through the roof. Also proper pitch is not easy to get. Never tried using it on a steel boat, but I imagine it might be a struggle unless the weather is a bit warmer than this!

 

Tim

[smileypete]

When I first blacked my boat I used Comastic, and have re-coated it a few times. I asked on here a while ago about over painting with bitumin and I was told that you can paint over cured comastic with bitumin but not the other way around, but I used Comastic then anyway. Now i'm goind into dock again and Comastic is getting dearer than ever. I've just asked spencer coatings whether they think I can paint their Intex 2 Bitumin over Comastic. Their response was that their Intex 2 is not suitable to paint a hull. Now i've seen this for sale at a Chandlery who are selling it as hull paint.. They also said it's not good to paint over Comastic with another paint, but maybe they would say that as Comastic is dearer.

 

They say Intex 2 is for painting steel posts etc, that are to be buried in the ground, sounds ideal for a boat hull...?

Casp'

I'd stick to Comastic around the waterline if it has better resistance to any oil film on the water.

 

But how does the Comastic fare on the bottom? If it scrubs off just as easily as bitumen then why not use bitumen, but if it's largely sound why not leave the areas of little wear and tear and do the rest.

 

Might be useful to try a few small areas of wear with bitumen to see how it compares to Comastic next time the boat is slipped.

 

But as others say if the coating flakes due to millscale, better use something cheap and save the money toward a timely grit blast job, then use something decent.

 

cheers, Pete.

~smpt~

Edited March 22, 2013 by smileypete

[Speedwheel]

Anyone tried the MC own brand stuff?

 

http://www.midlandchandlers.co.uk/Products/PaintBoatCare/HullTankBlacking/PA292.aspx

 

ETA - It's made by Teamac so should be ok.

Edited March 22, 2013 by Speedwheel

[casper ghost]

My Dad's convinced that if you never painted the hull from new it would last just as long, but maybe not look as good. Though it would save you a small fortune over the years...

Casp'

[casper ghost]

Slightly surprised to receive another email from Spencer paints today. It says that they have now referred my query onto their technical department (who did they refer to last time?), anyway, they now say that it is fine to paint bitumin over Comastic as long as the Comastic is weathered. They also say that their Intex 2 is fine for painting boat hulls.

Looks like someone responded originally in haste without checking properly..

Casp'

[mrsmelly]

My Dad's convinced that if you never painted the hull from new it would last just as long, but maybe not look as good. Though it would save you a small fortune over the years...

Casp'

 

I bought a colecraft 65 footer a few years ago from a dead honest chap who happily informed me that he had owned it 18 years and never docked or touched the hull and never had it out the water so he expected it to need serious work. I paid a very very very good price with proper folding cash again no survey and took it away after he had seen numerous tyre kickers. I took it to johnie Pinders and the 6 mil bottom and sides at worst were down to 5.7 mill. I had it epoxied cos I had saved a fortune on its true worth. Two factors major above all other things on hull longevity theses are Quality of steel and the water its been stood in.

 

Tim

[swift1894]

I find it hard to understand why, after all the years that steel boats have been on the canals, there isn't a simple answer to the question "What's the best hull coating?" Why does this topic come up time after time?

Surely there's got to be an answer. It's either bitumasic, comastic, 2 pack or whatever else is around these days (within realistic cost restrictions ie. before someone suggests gold plating). My understanding is that 2 pack seems to be favourite for durability.

[mrsmelly]

I find it hard to understand why, after all the years that steel boats have been on the canals, there isn't a simple answer to the question "What's the best hull coating?" Why does this topic come up time after time?

Surely there's got to be an answer. It's either bitumasic, comastic, 2 pack or whatever else is around these days (within realistic cost restrictions ie. before someone suggests gold plating). My understanding is that 2 pack seems to be favourite for durability.

 

Hi

 

I dont find it hard to understand that peoples opinions differ on many subjects, that is life. As a for instance there are always threads on this site re types of heating for a boat, now most of us fully understand that the ONLY sensible form of heating that beats all others in to a cocked hat is a solid fuel stove, but on a regular basis diesel etc is thrown up as viable even though it is not. Thats the way things are.

 

Tim

[Ex- Member]

I find it hard to understand why, after all the years that steel boats have been on the canals, there isn't a simple answer to the question "What's the best hull coating?" Why does this topic come up time after time?

Surely there's got to be an answer. It's either bitumasic, comastic, 2 pack or whatever else is around these days (within realistic cost restrictions ie. before someone suggests gold plating). My understanding is that 2 pack seems to be favourite for durability.

 

Well logically and from quite a bit of investigation I've come to the conclusion 2 pack is the best. Jotun my preference. However as you might guess it's the most expensive a well, even doing the work myself the paint alone cost over £600,

 

However I'm supposed to be getting well over 10 years protection for that, in fact the application of 6 coats to boat sides and bow & stern applied to a shot blasted surface, the same applied to seagoing ships have been proven to last 14 years. So you could argue it's a cheaper option, if your next hull painting is 14 years away.

 

With all the coatings, you have to weigh op the pro's & cons. Straight bitumen though is highly unlikely to last long against coatings that repel or protect against floating fuels oils & debris, as it just disappears from the place you most need protection.

 

You can see from this photo, this is just 18 months on the water new boat with 4 coats of bitumen applied. A lot of Black has worn off due to general weathering whilst on hard standing though, but the waterline failure is clear. Fortunaely the boat was primed prior to blacking so we suffered very little rust or any pitting.

 

 

At the end of the day, just 2 or 3 coats of a good 2 pack will give you a good 5 years worry free boating, and cost around £200 in paint. Taking into account craning or docking, it will probably cost more having to do it a second time in that 5 years.

 

Taking a boat my size out the water every 2 years even 3 would be pure stupidity and costly, so £600 is probably a hell of a lot cheaper than even bitumen if you take into account, craning, dry dock etc under taken just a few times over 14 years would cost much more.

 

Like everything pro's & con's I'm afraid.