Galvanic corrosion

[rusty69]

My grp uk boat is afloat all year round, it hasn't been crushed by ice so far,but is on the coast

[Alan de Enfield]

8 minutes ago, sailor mcgee said:

ice.

you can use GRP if you so wish to (but, that puts me out of a hobby..) and you MUST MUST MUST remove from the water by 1st of november  if in england - ice will crush grp if thick enough and you guys have had canals freeze over completly.

The GRP is 2" thick up to just above the waterline and 1" thick for the rest.

It has been in the water now for several years without problems, but is coming out in March for new anodes and a bottom / anti-foul inspection.

The anti-foul is called copper-coat and has a 10 year + lifespan.

 

 

http://coppercoat.com/coppercoat-info/

[Chewbacka]

8 hours ago, DandV said:

Copper sheathing wooden sea going craft was primarily a defence against toredo worm but also provided anti fouling. The copper sheathing though was vulnerable to any contact with rocks and gravel though but was easily repaired by over patching.

Coming back to the op question about copper sheeting - copper sheets were attached with copper nails sometimes brass but never iron/steel, as the iron nails rapidly corrode and the sheets fall off.  Mr Eiffel (of the tower) was well aware of this and came up with an elaborate fixing system so that the copper sheets of the Statue of Liberty ? did not touch the steel structure.

Edited December 5, 2018 by Chewbacka

[Flyboy]

29 minutes ago, Alan de Enfield said:

The Royal Navy doesn't appear to have any problems operating GRP ships at 196ft long x 32ft beam weighing 750 tonnes.

 

Why should a 40 - 50 - 60 foot long x 7 foot GRP tube be a problem (after all sewer pipes are made of plastic these days)

Isn't osmosis a big problem with GRP ?

[sailor mcgee]

1 minute ago, Alan de Enfield said:

The GRP is 2" thick up to just above the waterline and 1" thick for the rest.

It has been in the water now for several years without problems, but is coming out in March for new anodes and a bottom / anti-foul inspection.

The anti-foul is called copper-coat and has a 10 year + lifespan.

 

 

http://coppercoat.com/coppercoat-info/

most grp will crack if you have a propper layer of ice. (i am in sweden so maybe theres less ice in englandshire)

 

[Alan de Enfield]

11 minutes ago, Flyboy said:

Isn't osmosis a big problem with GRP ?

No

 

Osmosis only forms in boats that have been poorly laid up - and to quote a well known RYA surveyor "I know of no boat that has ever sunk because of Osmosis"

 

As a generalisation, it is primarily found in boats from the 70's and '80s which were built when we had little knowledge of Fibre Glass and the required manufacturing techniques, later boats do not seem to suffer the same manufacturing faults that leaves cavities within the lay-up.

Edited December 5, 2018 by Alan de Enfield

[Flyboy]

13 minutes ago, Alan de Enfield said:

No

Back in the 60's it was, so what happened to eradicate it ?   This article suggest otherwise.    https://www.makewoodgood.com/causes-of-osmosis-blistering-grp/

Edited December 5, 2018 by Flyboy

[sailor mcgee]

7 minutes ago, Flyboy said:

Isn't osmosis a big problem with GRP ?

no. it can be in salt water, but its not usually an issue in the usually fresh water of the canals. and in any event its bad when its in the core not when on the outside skin

/ grp see there is grp -t and grp 2t or 4t, the latter has a higher tensile strength, so, if you just say grp, its sort of meaningless - is it 4t or t grp? i always assume grp t as then i dont give the wrong advice re winter 4t is expensive but used by most see going craft, single skin by things like canoes and kayaks but 2 t is ckinda a midstep between the two. i have crossed the atlantic in a 4t hull  and wouldnt dream of doing so in a single skin

 

edit grp with different thicknesses of ply or sometimes other materials

Edited December 5, 2018 by sailor mcgee

[Tumshie]

9 minutes ago, Flyboy said:

Back in the 60's it was, so what happened to eradicate it ?

I have a friend who's a retired boat surveyor; I asked him about this once, and he said people often thought it was a bigger problem than it actually was. He had built several boats that went all over the world, so I trust that he know his stuff, even if I have no idea what he's talking about. ?

Edited December 5, 2018 by Tumshie

[sailor mcgee]

12 minutes ago, Alan de Enfield said:

The GRP is 2" thick up to just above the waterline and 1" thick for the rest.

It has been in the water now for several years without problems, but is coming out in March for new anodes and a bottom / anti-foul inspection.

The anti-foul is called copper-coat and has a 10 year + lifespan.

 

 

http://coppercoat.com/coppercoat-info/

i am not going to tell you what to do, but i will, if you allow me the moment to do so, share my lived experiance, i have worked for a time in a boat yard, i saw on many of the ocean going vessles we worked on that there was a need to have fresh paint or wash off every 3 years or so, the reason being that we ended up with too much crud on the bottom. the paint would last 10 years we recommended washing the underside (or doing a propper ocean crossing) year of two years and touch up every 3 to 4 years - 4 being the longest as corrosion on salt and metal would set in then on patches of exposed metal - there is often a lot of crap in a harbour and often out at sea now because people want to kill the oceans but meh thats a story for anouther time

11 minutes ago, Flyboy said:

Back in the 60's it was, so what happened to eradicate it ?

basiclly time, myfriend, time moved on.

[Alan de Enfield]

6 minutes ago, sailor mcgee said:

i am not going to tell you what to do, but i will, if you allow me the moment to do so, share my lived experiance, i have worked for a time in a boat yard, i saw on many of the ocean going vessles we worked on that there was a need to have fresh paint or wash off every 3 years or so, the reason being that we ended up with too much crud on the bottom. the paint would last 10 years we recommended washing the underside (or doing a propper ocean crossing) year of two years and touch up every 3 to 4 years - 4 being the longest as corrosion on salt and metal would set in then on patches of exposed metal - there is often a lot of crap in a harbour and often out at sea now because people want to kill the oceans but meh thats a story for anouther time

No problem I try to learn something every day.

 

The copper coat has been on for 3 years and from what can be seen (whilst in the water) there is absolutely no slime, weed or any other type of growth - that is the function of the copper.

I will know more in March.

 

On the other hand, my Category A sailing Catamaran has been in the water for 2 years and her bottom is a 'mess' she has now come out for the Winter and will be scrubbed and re-anti-fouled before going back in.

 

Awaiting Lift out at Plymouth.

 

 

[rusty69]

2 minutes ago, Alan de Enfield said:

On the other hand, my Category A sailing Catamaran has been in the water for 2 years and her bottom is a 'mess' she has now come out for the Winter and will be scrubbed and re-anti-fouled before going back in.

Well, at least your antifoul seems to keep the barnacles at bay on the hulls. We get barnacles attaching to the (unantifouled) hull after 4-5 weeks in the warmer months. Luckily a few minutes with a scraper removes them readily enough.

[Alan de Enfield]

1 minute ago, rusty69 said:

Well, at least your antifoul seems to keep the barnacles at bay on the hulls. We get barnacles attaching to the (unantifouled) hull after 4-5 weeks in the warmer months. Luckily a few minutes with a scraper removes them readily enough.

It is amazing the number an size of the Zebra mussels in the (Canal fresh water) marina our neighbours boats are covered in them, but the copper stuff has kept ours totally free of them

[sailor mcgee]

5 minutes ago, Alan de Enfield said:

No problem I try to learn something every day.

 

The copper coat has been on for 3 years and from what can be seen (whilst in the water) there is absolutely no slime, weed or any other type of growth - that is the function of the copper.

I will know more in March.

 

On the other hand, my Category A sailing Catamaran has been in the water for 2 years and her bottom is a 'mess' she has now come out for the Winter and will be scrubbed and re-anti-fouled before going back in.

 

Awaiting Lift out at Plymouth.

 

 

catamaran= lunch money for me. a lot of hot weather means sun and thus algea growth, so if you go to sea and race a little, get some speed up (if safe to do so) then it usually gets rid of the algea atleast. moloscea are harder to get shot of. only real way is a boat yard imho

its the same no matter what hull you work on.

[rusty69]

2 minutes ago, Alan de Enfield said:

It is amazing the number an size of the Zebra mussels in the (Canal fresh water) marina our neighbours boats are covered in them, but the copper stuff has kept ours totally free of them

Works on slugs too

[sailor mcgee]

2 minutes ago, rusty69 said:

Works on slugs too

you could say its bullet proof (gun joke)

[Alan de Enfield]

4 minutes ago, sailor mcgee said:

so if you go to sea

That the reason we have the Cat.

Had a nice 3000 mile trip from Croatia back to Hull, then this year have moved cruising grounds down to Plymouth, as, with a 23 foot beam there is nowhere on the East Coast capable of lifting her out..

[Mad Harold]

1 hour ago, Bee said:

How about a layer of epoxy then a layer of fibreglass matting to give it strength then more epoxy then more glass matting and so on, then take away the steel because its not needed any more. Oops, I seem to have invented GRP

Sounds like an alternative to having an old boat overplated?

[Tumshie]

5 minutes ago, sailor mcgee said:

you could say its bullet proof (gun joke)

As the Götheborg was only launched in 2003 I doubt she's seen many guns. ?

 

https://www.soic.se/ostindiefararen-gotheborg/en

[sailor mcgee]

47 minutes ago, Flyboy said:

Isn't osmosis a big problem with GRP ?

 more about the different core type fwiw its not all ply

1 minute ago, Tumshie said:

As the Götheborg was only launched in 2003 I doubt she's seen many guns. ?

 

https://www.soic.se/ostindiefararen-gotheborg/en

she has 20 working cannons on board and on her way to china was under military escort round the horn.

[Bee]

1 minute ago, Mad Harold said:

Sounds like an alternative to having an old boat overplated?

If you could guarantee the adhesion then there is no real reason why not but I think overplating is perfectly OK, its one of the advantages of steel, you can repair it easily. I might not be too happy about taking a patched up old colander out to sea though. GRP is brilliant stuff but narrowboats are mostly flat sections, GRP works best when it is moulded into shapes for strength otherwise it needs lots of framing. Both materials are good in their own way. I wonder if there will ever be recycled plastic 'planks' that could be made into 'wooden' narrowboats? No rot, no rust, tough as old boots.

[Tumshie]

9 minutes ago, sailor mcgee said:

she has 20 working cannons on board and on her way to china was under military escort round the horn.

My apologies - I knew she had done that 10 years ago, I didn't realise she was doing it again. You can't follow all the tall ships, can you. 

[sailor mcgee]

no she did it a while ago, you are right but shes always had those cannons ❤️

[Shockabilly]

1 hour ago, Tumshie said:

Then the search function is your friend, there are loads of threads on here discussing exactly this and other various forms of it. I recommend reading as many different threads as you can but don't get your self stuck in a quagmire of despair over it. 

 

 

Thanks Tumshie!

[Tumshie]

Just now, Shockabilly said:

Thanks Tumshie!

You're welcome.