Shot Blasting, Is it required for Plating?

[sueanddaren]

We need a bit of over plating on the base. Just the last 6 foot, basically the bit under the swim. I have got a quote but the yard are very keen on shot blasting this area and this adds another £1000 to what is already a big quote. So the question is is it realy required? What do yards that don't have these facilities do and is it as good?

 

Daren

 

[b0atman]

Check with martin at Kedian engineering

[Boat&Bikes]

£1000 for blasting 40 square footish of steel?

[Paul C]

Did you get more than one quote for the whole job?

[sueanddaren]

£1000 for blasting 40 square footish of steel?

The £1000 was for shot blasting just the back 6 foot, so yes about 40 square foot if you ignore the fact that its even less as its almost a triangular shape.

Did you get more than one quote for the whole job?

Not yet, but do I need shot blasting? As Im not sure every yard that does plating can do shot blasting.

[Paul C]

 

Not yet, but do I need shot blasting? As Im not sure every yard that does plating can do shot blasting.

 

I don't know, I've not seen the boat. The boatyard has, and are undertaking the job. I'd trust their judgement in this case, in their saying its needed - I think they're doing you a favour by doing it. If it were not done, then the plate is at least going to entrap the original corrosion which rendered the overplating necessary, and probably won't neatly fit over it if its volume is too great to accommodate. Is the boat actually holed, or just thin enough to need overplating?

[sueanddaren]

 

I don't know, I've not seen the boat. The boatyard has, and are undertaking the job. I'd trust their judgement in this case, in their saying its needed - I think they're doing you a favour by doing it. If it were not done, then the plate is at least going to entrap the original corrosion which rendered the overplating necessary, and probably won't neatly fit over it if its volume is too great to accommodate. Is the boat actually holed, or just thin enough to need overplating?

Good point, but the boatyard hasn't seen the boat out of the water they just say that shot blasting has to be done one way or another. Would grinding or scrabling not be as good? The base in this area is down to 4mm in a few spots but not bad for a 34 year old boat with only 6mm when built.

[bigste]

Unless it is for comprehensive insurance I'd have thought 4mm was ample thickness.

[Paul C]

Good point, but the boatyard hasn't seen the boat out of the water they just say that shot blasting has to be done one way or another. Would grinding or scrabling not be as good? The base in this area is down to 4mm in a few spots but not bad for a 34 year old boat with only 6mm when built.

 

I think they're covering their back because shotblasting may be needed. Probably better that way than giving you a £1000 surprise once its out and the clock is ticking and you're committed to the dry dock/slip fees by that point. Did you see the boat out the water, I presume your keen-ness on getting it overplated came from a survey, were you able to look at the boat etc?

[BD3Bill]

Unless it is for comprehensive insurance I'd have thought 4mm was ample thickness.

Agreed.

 

Sounds a bit rum altogether this story.

 

How on earth can the yard quote when they haven't seen the job?

 

Who has told the OP the base is down to 4mm?

 

Sounds like the yard are preparing to stitch the OP right up.

 

Different job I know, but we only paid £1200 + vat to have the boat craned out, sides+uxter blasted, two pack to the sides+uxter of hull on a 45ft boat. I'm pretty sure it broke down as 400/400/400.

[John V]

I'm puzzled by the "needs to be shot blasted".....

 

We certainly didn't shot blast Sabina before doing the major steelwork which included both cut out and replace and doubling.

Yes we needle gunned/ wire brushed the areas to be doubled, cut holes to allow welding from inside, and primed the area before welding on the doubler etc.

You certainly need to take some precautions to prevent rust forming between the new and old plate but shot blasting ? seems excessive.

I eventually had Sabina grit blasted a few years later but that was purely before changing to 2 pack from conventional paint schemes

[sueanddaren]

 

I think they're covering their back because shotblasting may be needed. Probably better that way than giving you a £1000 surprise once its out and the clock is ticking and you're committed to the dry dock/slip fees by that point. Did you see the boat out the water, I presume your keen-ness on getting it overplated came from a survey, were you able to look at the boat etc?

Every time we pull the boat out of the water (every 2 years) for blacking Ive used an ultrasonic gauge in about 40 places to monitor the hull. When we bought it 10 years ago the back end was 4.5mm as measured by the surveyer and its slowly been getting thinner over the years. So before it gets desperate I thought get it done. The rest of the boat is between 6 and 5.9mm so no problem there.

[David Mack]

So you have identified the need for plating, not your surveyor or insurance company?

 

Before spending "a big quote" and another £1000, you might want to consider getting a second opinion. It doesn't sound to me as if this is urgent, so you could simply wait until the boat is next out of water for blacking, and then get a hull survey done, and any necessary plating and the reblacking all done in one docking.

 

According to his website Martin Kedian will replate hull and sides to above the waterline and reblack for £135 per foot (plus cranage/transport), so just doing the bottom plate for a 6 ft length should cost well under £1000 for the actual plating. Sounds to me like your yard is ripping you off, and you should seek some other quotes.

[DHutch]

Hard to know, and I have skimmed the thread, but for 40sqft of baseplate, for a grand, I would much rather get under there with a 9" grinder and knock 60% of it off and slap some blacking on.

 

If the boat way brand new, and you where doing it perfectly, then fairly enough. But assuming the plates of good thickness its likely to outlast the boat anyway.

 

The other option is 'picked steel' or just to knock the scale off the area before the plates welded on to avoid working upside down!

 

 

Daniel

[ditchcrawler]

 

Not yet, but do I need shot blasting? As Im not sure every yard that does plating can do shot blasting.

Maybe that answers your question

[Martin Kedian]

I would be happy to chat through the subject of over plating with the op if it helps

 

Martin.

Kedian engineering ltd

[waterworks]

I can't see what purpose the blasting is for if they are going to over plate it. The scale will come off with a pressure washer, and its only a small area, probably half of 6 'x 6' 10 " once its over plated there is no oxygen between the plates to feed corrosion. No oxygen, no oxides. An hours work with a grinder would do the same job of cleaning it up.

[X Alan W]

If the plate in question is 4mm, that is 1or so mm thicker than Springer base plate as built, so I wouldn't panic, as by your own checking it has only lost half a mm in 10 years The 10mm base plates are a modern trend & some commercial craft were only built with 1/4" = 6.3 mm plate but it's your's to decide but I would certainly ask around as that seems (as the Tesco advert says) the price quoted is rather steep.