Blow torch - Osmosis treatment

[30boat]

Thats good info, thanks, can you say what temp you had your "heating thing" running at though?
I'm thinking underfloor heating mat, but it seems to max out at about 40degrees, so I'm just wondering if this is enough or if it needs something more powerful.
Although I suppose it would depend on the amount of vacuum reached i.e.

• greater vacuum = lower boiling point = less heat required
• lower vacuum = higher boiling point = more heat required

Makes sense in my head anyway

It was hot enough to lightly scorch the laminate.The amount of vacuum I got from that litte pump was astonishing.Providing the edges of the pads were well sealed with tape it was impossible to pull the vinil fabric away from the hull with my fingers.The only problem with such a small pump is that sealing must be perfect or it can't compensate for any leaks not matter how small.

 

[SailingEcosse]

It was hot enough to lightly scorch the laminate.The amount of vacuum I got from that litte pump was astonishing.Providing the edges of the pads were well sealed with tape it was impossible to pull the vinil fabric away from the hull with my fingers.The only problem with such a small pump is that sealing must be perfect or it can't compensate for any leaks not matter how small.

Hot enough to scorch the laminate is pretty hot (I'm thinking 70-80 degrees under vacuum?), and certainly more than I'll get from floor heating

So unless I can source a serious hi vac pump (like Downwests )

Some figures for my larger pump.
1.5kw motor
1100 lt/min of free air

I'll might need to be able to generate a bit more heat.

Anyway it looks like the best way to find out will be to try it and see, so, pump, heat mat, vinyl/polythene and some tape required


PS
And this was the exact story that started it

I saw a reasonably big yacht being done by this method umpty years ago in Mallaig of all places.
quite scary when you saw the guff that came out of the hull,
the treatment comprised of the "torching" of the hull scraping off the brown oooze that came out of the laminate then grinding and finally four coats of I believe hot applied epoxy coating.
not sure about the last part as didnt see the coating application but the company doing the job had the equipment with them. I believe it was a Scandinavian company who carried out the work.

 

[30boat]

Hot enough to scorch the laminate is pretty hot (I'm thinking 70-80 degrees under vacuum?), and certainly more than I'll get from floor heating

So unless I can source a serious hi vac pump (like Downwests )

I'll might need to be able to generate a bit more heat.

Anyway it looks like the best way to find out will be to try it and see, so, pump, heat mat, vinyl/polythene and some tape required


PS
And this was the exact story that started it

I used something like this.I bought it by the meter and cut as needed.I'm sure you can find some easily.http://www.nphheaters.com/quote/flexible_heating-tapes/fht_09.pdf

 

[DownWest]

Rather than finding something like my stuff ( could lend/sell one if transport not too steep) there are venturi cheapies that run off a normal compressor. Might be enough for smaller areas of laminate. Basicly the output from the compressor blows through a a small venturi box, which provides the 'suck' for the vacuum job. Quite common in smaller applications, as around $50 bucks. Google them.
A

Another source of pumps is/are air conditioning units. The quiet compressors used by artists for airbrushes are actually fridge units. Aircon ones are a lot more powerful and cheap/free if you look around. They act as vac pumps very well.
This also a question of time/cost. A DIY cheap solution may take more time, if you have it(sounds like) Fancy(expensive) pumps are faster and need much more other materials to cover the bigger area.
Dinner calls.. Hope this makes sense.
A

 

[capetown]

Any news?

Hi Guys,

Wonder if there is any news/progress.

If you need any calcs done, I've got the ears of a couple of Chemical Engineers, they both like beer

Via PM.

 

[SailingEcosse]

If you need any calcs done, I've got the ears of a couple of Chemical Engineers, they both like beer

Not sure what I would do with a chemical engineer TBH, but I also like beer

 

[SailingEcosse]

Update

Work and holidays delayed this a fair bit, but my hull drying attempts are now in full swing, so I thought I would post this pic for anyone interested.

As suggested here I tried just vacuum bagging sections of the hull, but after several days on a single area the moisture readings were little different from where they started (although I do suspect it's not actually moisture that it's reporting on) so I decided to make up a hotvac style pad, with a heated silicon blanket, to see what difference it made immediate improvement, 2-3 hrs has been enough on several areas tried to drop the moisture readings right into the green (tramex skipper, setting 2), which everything from washing, to heat lamps, and steam treaments have completely failed to achieve.

So it's back to the yard tomorrow and get some more done, and all being well now, I might even get some epoxy applied this side of xmas

 

[capetown]

It's looking good.

Thanks for the update.

Questions.

Where did you get the large silicone sheet from?

What temperature does your element reach?

What vacuum pump are you using and finally what vacuum are you pulling?

 

[KristiferColumbus]

Not seen that but have seen someone drill out individual blisters, dry, fill etc. year after year.......

OK if you have the time...

(& no money)

I did the blisters on my boat seven or eight years ago using that method although I actually chiseled them out using a plane blade & it has been very successful.
Completely unnecessary to do them every year that is a myth.

 

[Searush]

I did the blisters on my boat seven or eight years ago using that method although I actually chiseled them out using a plane blade & it has been very successful.
Completely unnecessary to do them every year that is a myth.

I don't think people were meaning redo the same blisters each year but rather treat the new blisters that crop up each year (or three). But that depends on whether the problem is localised to a few blisters & once they are done it stops, or if the problem remains & keeps popping up in fresh places.

 

[KellysEye]

>It is based on heated vacuum mats

Yes, seen that used in Portugal. I dread to think what a blow torch might do.

 

[KristiferColumbus]

I don't think people were meaning redo the same blisters each year but rather treat the new blisters that crop up each year (or three). But that depends on whether the problem is localised to a few blisters & once they are done it stops, or if the problem remains & keeps popping up in fresh places.

In my experience they don't pop up like mushrooms every year searush

I did all the significant ones on the bottom of my boat (a few dozen) several years ago & for the last couple of seasons I have noticed one or two that I should get round to doing something about.A job that will probably take about an hour & can be fitted in with all the other stuff I have to do.I don't really worry about them greatly.

 

[Bosun Higgs]

Hotvac I have seen and had priced but the boat just isn't worth the cost i.e. £4k (although this did include the epoxy treatment as well) but it's twice what I paid for the boat (26ft colvic).

With a boat worth that little , why bother with an osmosis cure at all. Just wait til it falls to bits, likely a fairly long time.

P.S. Ever seen grp burn? One of the dafter members of our club when laying new grp on a wooden coach roof used a blowlamp to help it go off and go off it did. Spectacular flames and smoke.

 

[SailingEcosse]

Where did you get the large silicone sheet from?

What temperature does your element reach?

What vacuum pump are you using and finally what vacuum are you pulling?

If you mean the heat mat, it was a lucky buy on ebay (brand new and unused), made by Gotherm and it is rated at 2kw.
I was quoted £400+ from Gotherm

I'm using a thin rubber (epdm) sheet to hold it in place and to create the seal to the hull though.

Not sure what ultimate temperature it will actually reach although I'd guess at something like 200-300 degrees, but it's held in check with a thermostatic controller.

The vacuum pump is a Javac 2stage 1.5cfm which is rated at 25microns (?), according to the gauge though it manages just over 28hg.


Hope that helps, but if you need any more info let me know.

 

[SailingEcosse]

With a boat worth that little , why bother with an osmosis cure at all. Just wait til it falls to bits, likely a fairly long time.

Yes, fair point, but I like to know about these things, and given the boat came pretty cheap I figured it was worth the time and cost to find out what is actually under a blistered hull

P.S. Ever seen grp burn? One of the dafter members of our club when laying new grp on a wooden coach roof used a blowlamp to help it go off and go off it did. Spectacular flames and smoke.

I haven't, although as per the title of the thread I was temped to give the blow torch route a go, happy I managed to steer myself away from it now though, definitely a dangerous option


As a slight aside, I would also say that I doubt that I would ever go down the route of epoxy on top of gelcoat (blisters or not), as from what I now understand of osmosis blisters and epoxy (and I think I've read every article, web page and document ever written about it now) it just doesn't seem like a good way to go.

 

[Lakesailor]

I used a blowtorch to test grp sheets to destruction when deciding if they would be safe as a splashback near a commercial cooker.
The sheets were made by a commercial frp producer with a 6" tile pattern on the gelcoat face.
20 seconds was enough to catch fire at 6" distance.

The integrity of the layup was destroyed, even before igntion.

Naked flames not a good idea, in my opinion.

 

[lw395]

Isn't steam cleaning the normal way to heat the laminate to 100degC?

 

[Grajan]

Saw this "Osmosis repair" method being carried out in the yard at Mallaig, looked highly dangerous with brown gloop bubbling out from the laminate which occasionally ignited.
the scandinavian operative explained to me that this brown stuff was the "badness" coming out of the hull, unfortunately didnt see the finished job but I believe the vessel was being brought up to standard for charter

 

[SailingEcosse]

Isn't steam cleaning the normal way to heat the laminate to 100degC?

Yeh tried that as well, and spoke to Adrian Baker at advanced osmosis (top guy actually, well worth a chat with if dealing with a blistered boat) at length on it, and he reckoned the gelplane job didn't go deep enough for the steam washing to work effectively
Although how much laminate would actually need to be removed for it to be effective was my concern here!

Also, as I (now) understand it, the 100deg mark isn't enough to remove glycol residues which need temperatures of something like 190 deg, and without heat and vacuum this temp just isn't possible without damaging the laminate.

So while the steam wash technique has it's merits, the hotvac route would appear to offer a more effective solution to removing the deeper effects of osmotic (hydrolysis/hydrolytic) activity.

Which incidently (back to my original title again, and Grajan's mallaig story) is why the blow torch method works, because it reaches very high, but localised temperatures (and presuming you manage not to ignite your hull of course )

Hows that for a long answer to a short question

 

[Steviecracknell]

Hot air gun

I used a hot air gun (paint stripper) on the hull of my laser dinghy to speed up the removal of paint, bad idea. The paint was easily removed, but if your hot air application was slow over that area, you run the risk of the gelcoat bubble up and delaminating, this happened a few times!!
Just wondering if the same thing happened to the boat in Mallaig.

Stevie.