DIY soda blasting for antifoul removal

[John the kiwi]

.
Has anyone tried this? This soda pot is only £70 and £16 for 10kg of soda

Does anyone know

a) How much soda would be required for a long-keel 27-footer

b) An easy way to set up tenting to contain the spray?


I also see ALDI do an 1800W compressor that appears to be powerful enough to run it.

The soda pot says
Air Consumption 8.5cfm @ 90psi
Working Pressure 35-90psi

The ALDI compressor says
Air displacement: 262 l/min, 9.3 CFM
Operating pressure approx. 8 bar


- W

The soda pot says 8.5cfm at 90 psi
Compressors are usually rated as cfm FAD which is free air delivery. ie. atmospheric pressure or displacemnet as mentioned.
To run soda pot you would need a compressor of about 55 cfm FAD which is significantly bigger than the aldi unit.
actually 90/14.3 = 6.3 times bigger. look up Boyles law...

 

[lw395]

I always thought air tools were rated in the same way as compressors...

 

[John the kiwi]

Yeah well. If you are selling a compressor, the free air delivery looks like a big number, whereas if selling a tool, air volume consumption stated at pressure makes it look economical.....
As always caveat emptor!

 

[lw395]

Never trust anything in imperial units!

90psi is seven and a bit times the air at atmospheric pressure BTW.
Assuming it's cooled anyway.

Just asked my mechy colleague about compressors, apparently what you need is lots of HP and a decent sized tank. And duty cycle.

 

[Daydream believer]

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I've been quoted £1250 + VAT, so it looks like it's back to scraping or hire a more powerful compressor.
- W

How many quotes to get to that? there are quite a lot of firms that do that type of work & many are used to traveling, so that should not be an issue. It would only be seen as a day's work wherever they come from. The actual job will take no more than 2 hours if there is no awkward sheeting up required. Allow 1.5 hours traveling each way & it is a 5-6 hour job. No time for any other jobs so they will charge an 8 hour day's rate.
£ 250 for the operator. £150 for the equipment contribution, £ 150 for the blasting medium (guess), £200 for the owner comes to £ 750
So I would expect a quote around £ 800+ VAT in your area, if you live in the wilds. However, if you do, then work is possibly scarce, so the price might come down to £ 700 if the bloke is an owner/operator. Probably would not be VAT registered & happy for a cash deal. Not that I would ever suggest such a thing:disgust:

 

[earlybird]

All air consumption values will be FAD/min, but to blast a hull in a sensible time will require a compressor of say10-15hp absolute minimum, probably considerably bigger. This rules out a portable electric power. A diesel powered machine is needed, the yard blasting I've seen has used machines towed behind a van. Tenting up is also a big job, together with personal protection. Also, like many tasks, there's probably more skill required than meets the eye. I wouldn't like to practice on my own boat.

 

[Daydream believer]

. I wouldn't like to practice on my own boat.

You would start with the keel. That should give you all the "practice" that you need

 

[webcraft]

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Well, I bought one of these second hand off Ebay

Will report back when I have used it.


- W

 

[Elessar]

.
Well, I bought one of these second hand off Ebay

Will report back when I have used it.


- W

Good call I reckon.
Get lots of blades.
Get good PPE.
Good luck!!

then..........

Do you have epoxy on your hull? If not it's a good time to add it. 6 coats of a solvented epoxy, green grey green grey green grey and antifoul over the top.

Personally once stripped I'd coppercoat it, but it's too late in the year now anyway so that's a pointless debate I won't start!!!!!

 

[DownWest]

.
Well, I bought one of these second hand off Ebay

Will report back when I have used it.


- W

That does look useful. No flying dust with compressed air and gets it off at a decent rate.

 

[webcraft]

Good call I reckon.
Get lots of blades.
Get good PPE.
Good luck!!

then..........

Do you have epoxy on your hull? If not it's a good time to add it. 6 coats of a solvented epoxy, green grey green grey green grey and antifoul over the top.

Personally once stripped I'd coppercoat it, but it's too late in the year now anyway so that's a pointless debate I won't start!!!!!

It was epoxied back in 2006 the last time it was stripped right back.

Is there any point in another couple of coats?

Why is it too late to coppercoat? (Not that I can afford it . . . )


- W

 

[Amulet]

Nick, I emailed you about this. I have a guy coming for this purpose.

 

[Birdseye]

Re: DIY soda blasting

You’re good at websites and can earn money faster doing that than pros will charge to blast your boat.

Now that is a really sensible answer.I have had two boats blasted by pros and in both cases its still been damn hard filthy work to get good results, a lot of medim was needed and I ended up thinking to myself "I'm glad I paid someone else". And I have installed engines myself, made up standing rigging, installed heaters and waste tanks and ssb etc. In fact I have never had a yard do a job except hull blasting and in one case copper coating. So I am not a skiver but I would still employ a yard if I had to blast a hull.

 

[Graham376]

.
Well, I bought one of these second hand off Ebay Will report back when I have used it.

Remember to grind the corners off the blade or you're likely to get some deep scratches into the gel. I used one of those 9 years ago but found it quicker with less damage last winter to use a 2 handed Bahco type scraper.

 

[webcraft]

Remember to grind the corners off the blade or you're likely to get some deep scratches into the gel. I used one of those 9 years ago but found it quicker with less damage last winter to use a 2 handed Bahco type scraper.

Yep, going to grind the corners off. Will also get a Bahco as a backup.


- W

 

[Elessar]

It was epoxied back in 2006 the last time it was stripped right back.

Is there any point in another couple of coats?

Why is it too late to coppercoat? (Not that I can afford it . . . )


- W

Epoxy.

If you used gel shield 200 then you will have probably 5 layers of green grey. Dry film thickness of each is about 40 microns. If you don’t damage it when you strip then you don’t need to overcoat - 200 microns of epoxy is waterproof. But the great thing is where you do damage it, the layers allow you to see how deep the damage is. Just touch up any damaged bits would be my recommendation. It has an infinite overcoating window so you don’t have to worry about adhesion.

If you used a solvent free epoxy like gel shield plus then the above is completely wrong. Repost if that’s the case.

Coppercoat - it will be very hard to find a weather window now until after the winter. You need warm and dry. It’s water soluble until cured. Condensation or rain will ruin it. North of Watford even harder.

 

[AntarcticPilot]

he's using sand.

Sandblasing works by the grains splitting and releasing energy when they hit the hard surface. You cannot us sand for sandblasting despite the name.

The free silica in split sand is as bad as asbestos fibres. It can give you and everyone in the yard around you silicosis.

He has saved a few £ and almost certainly shortened his life, and those of others. Oh and a mask is no protection.

It's wet blasting; no dust and much safer than air blasting.

 

[zoidberg]

In response to your original question, I have soda-blast DIY stripped multiple layers of old a/f from a Cutlass 27. I tried the Bahco scraper approach and found it too stressful...!
I was able to borrow a 5-6 cu.ft. compressor ( I paid £250 nominal to a friend ) and bought his bags of soda medium from him. That was a mistake. My experience was that it is essential to buy fresh, very dry medium. Otherwise, the pot/mixer chambers and the nozzles clog up quickly, and one spends significant time cleaning them out.

The process was effective, and easy to learn. A deeply-experienced tech rep from Jotun Paints checked the result, pronounced it good and sound, and sold me some suitable Jotun product! I was happy with that.

I didn't bother with 'tenting', but laid tarps on the ground around so the residues could be swept up. It is, of course, contaminated with antifoul paint particles and therefore toxic.

One warning! The controllable nozzles I had initially were worn through by the abrasive medium, and that jetted out at serious velocity onto my adjacent hand. I was then rather thankful I'd bothered with stout gauntlets..... I tracked down and retro-fitted much more robust nozzles, and had no more trouble.

Several local builders' merchants rent out compressors.

I'd use that process again....

 

[AntarcticPilot]

he's using sand.

Sandblasing works by the grains splitting and releasing energy when they hit the hard surface. You cannot us sand for sandblasting despite the name.

The free silica in split sand is as bad as asbestos fibres. It can give you and everyone in the yard around you silicosis.

He has saved a few £ and almost certainly shortened his life, and those of others. Oh and a mask is no protection.

Dry silica is, of course, very dangerous and a killer in trades such as mining and building where workers are likely to be exposed to silica dust. Silicosis is the medical term.

I had Capricious blasted professionally prior to applying Coppercoat, and at the time I looked into various DIY routes to do it. After seeing the equipment that the professional used and his PPE, I'm glad I didn't try. First of all, I looked at the Karcher wet blasting system and although it is the most amenable to use by a DIYer, being much safer, it is also relatively slow. The guy here is using a much more capable petrol driven pressure washer to power the Karcher accessory; a domestic Karcher pressure washer will probably do the job but VERY slowly. It isn't fast even with the kit the guy in the video uses. I'd also worry about a higher powered pressure washer eroding the nozzle of the Karcher kit; some revuew mention that the nozzle erodes even with domestic pressure washers.

Then I looked into hiring more capable wet blasting kit. This looked sort of possible - but the saving was small!

I never considered DIY dry blasting for safety reasons, and when the guy did mine, I realized I'd made a good decision. He was kitted up in stuff that looked like he was going to Mars! Positive pressure mask, full body cover; you name it, he had it. And after standing a bit too close to see how it went, I think he needed every bit of it. Futher, his equipment was MASSIVE. A towable compressor, some sort of air pressure regulation system and hopper and a fully controllable nozzle arrangement - and, no doubt, lots more that I missed.

But the real clincher that I'd done the right thing was that the level of skill required to get good results was far beyond anything I could bring to bear, or expect to learn over the length of one job. He used olivine as the blasting medium, and was able to vary the pressure etc. so that he could achieve a good result on both the GRP hull and the cast-iron keel. The latter needed a LOT of skill, as one side of the casting was very porous and rough; he was ably to remove all the pockets of rust/slag and achieve a good, grey-metal finish for putting epoxy on.

The other reason I'm glad I went for a professional was that the quantity of blasting medium used was enormous. He seemed to be tipping a new sack into the hopper every few minutes.

 

[Elessar]

It's wet blasting; no dust and much safer than air blasting.

You’ve never seen it happen then? The dust may not go as far that’s all.