yachtorion
Well-Known Member
Just wondering if I'm the only person stupid enough to use a 1/3sheet electric sander loaded with wet'n'dry paper on a well dampened (with a spray bottle, not soaked) substrate?
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Wet and Dry meet Electric Sander
- Thread starter yachtorion
- Start date
savageseadog
Well-Known Member
You will only get the odd tingle, I've done it.
Seriously it can be dangerous, if 240V an RCD or certified isolation transformer is a must, 110V tools and transformer is better.
Seriously it can be dangerous, if 240V an RCD or certified isolation transformer is a must, 110V tools and transformer is better.
LittleShip
Well-Known Member
Why not just use it dry, connecting to a vacuum will leave you with as good a surface for painting as trying to use Wet and Dry with 240v. Far to dangerous IMO.
If you feel that you really have to use W&D then invest in a small compressor and a purpose made air sander.
Tom.
If you feel that you really have to use W&D then invest in a small compressor and a purpose made air sander.
Tom.
jerrytug
N/A
Why would it be dangerous? How would using wet sandpaper give you a shock? What possible difference could it make?
seanfoster
Well-Known Member
Or even better an air powered sander with a compressor.
yachtorion
Well-Known Member
That was the calculation I made before I did it. The tool is plastic bodied, and there are no holes in the sandpaper to allow water through into the tool. On top of which, it's going through to a generator which is a closed circuit (not earthed to ground or the boat) anyway, and there is an RCD in the line. I'm also not drenching the material - just making sure it's nice and damp.
All of which means it's very hard for me to see how I'm likely to get a shock at all, certainly beyond a momentary one across a finger which even if the RCD didn't trip shouldn't do much harm - I've been zapped that way before buy an old laser printer. IIRC it's across the chest to worry about - and it's hard to see how that would end up being a circuit.
I suppose it might not do the tool much good because some moisture will inevitably get in there, but that said it is constantly blowing air through the motor and one assumes the dust path doesn't go through the motor and is well sealed from it to prevent wear.
The reason behind it is I have just never found anything anywhere near as good on gelcoat as straight forward old Wet'N'Dry used wet.
That said, I will look into the air equivalent.
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Pye_End
Well-Known Member
Mesh wet and dry tends not to clog up, and so much easier than the usual wet and dry. Whether using a sander or by hand, it takes plenty of water (ie not just a spray in a bottle) to keep the sandpaper clear. Hose plus mesh works well.
Edit - had assumed this was an antifouling question, but see now that it is not.
Edit - had assumed this was an antifouling question, but see now that it is not.
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savageseadog
Well-Known Member
The water will eventually bridge through the joins in the plastic body and come into contact with live circuits and your hands. Sure an RCD will probably protect you, the shock may be localised but it really isn't acceptable to take chances, I'm no H&S freak by the way.
yachtorion
Well-Known Member
Yeah you are of course all correct. I think I'll buy an air compressor for next time.
Marine Reflections
Well-Known Member
I use a Mirca electric DA with Trizact foam backed discs (wet n dry)
The machine is stepped down to 18v, but even when I've added way too much water, there has never been an issue in the last ten years I've had it.
Just to add, if you use pure H2o rather than tap water, as pure H2o doesn't conduct electricity.
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bendyone
Well-Known Member
Dont do it Electricity kills.
John the kiwi
Well-Known Member
Being a daredevil fool, I did it too! At 240 volts no less.
Oh the humanity etc...
But:
Trusted and tested RCD and also Double insulated sander.
Carefully controlled the water flow so as not to splash the tool or the power lead - you only need a steady dribble to keep the wet an dry from clogging and suspending the powerlaed from an overhead point with a bungee is not only safer but make the job easier.
Not really different to using a cake mixer in a water based sauce when you think about it?
Biggest downside is that water did get to the shielded but not sealed bearing on the platen of the sander and next time i tried to use it it had seized up.
Cost me NZ$12 to replace the bearing iirc.
Was this wise and would i recommend it? Probably not!
If you plan to do a lot of this kind of thing then a compressor and pneumatic sander will stop you wondering "Am i going to die any second now?"
Takes some of the fun out of it though.
Cheers
Oh the humanity etc...
But:
Trusted and tested RCD and also Double insulated sander.
Carefully controlled the water flow so as not to splash the tool or the power lead - you only need a steady dribble to keep the wet an dry from clogging and suspending the powerlaed from an overhead point with a bungee is not only safer but make the job easier.
Not really different to using a cake mixer in a water based sauce when you think about it?
Biggest downside is that water did get to the shielded but not sealed bearing on the platen of the sander and next time i tried to use it it had seized up.
Cost me NZ$12 to replace the bearing iirc.
Was this wise and would i recommend it? Probably not!
If you plan to do a lot of this kind of thing then a compressor and pneumatic sander will stop you wondering "Am i going to die any second now?"
Takes some of the fun out of it though.
Cheers
savageseadog
Well-Known Member
Problem with air tools is moving around a compressor big enough to supply an air sander, otherwise a great idea
Marine Reflections
Well-Known Member
Very short video of surface correction.
At 1:21 you can see the Mirca DA in action, using a 4000 grit.
At 1:21 you can see the Mirca DA in action, using a 4000 grit.
BERT T
Well-Known Member
Why not use Dry Cut as most of the car body shops now do, no water required and it does not clog up.
Marine Reflections
Well-Known Member
Really it boils down to grit level, or how much surface you are planning on removing. The dry cut type work very well, but really only in the coarser grit types, then for them to really be clog free you have extraction to consider. No extraction and they will clog.
For dry cutting I use Abralon dry cut discs, either the 77mm or the 150mm, but only up to 1000 grit, past this (finer) the particles are less accurate in their size.
Imagine using a 1000 grit to fine sand, but the particles size isn't 100% equal, it may be peppered with 500grit particles.
This won't be noticeable on surfaces like wood, but it will stand out a mile on gel coat.
When you are correcting a surface like gel coat, removing scratches or very heavy oxidation etc, you are only really going into the gel depth 1 or 2%, to do this requires a constant particle size on the disc or you will be creating more work than you are correcting in the first place.
Above 1000 grit I always cut wet.
Again Abralon do some really good foam backed discs, but they don't compare to 3M's Trizact range (1500, 3000 and 5000 grit) as they are the same particle size throughout the whole disc.
£45.00 for 15 discs though, but worth it as they correct in a uniformed and controlled manner.
Marine Reflections
Well-Known Member
After reading your blog ( very interesting) and looking at the gel coat I can see you will indeed need to paper prior to polishing.
I would suggest though that it would probably be just as fast and safer for your gel coat to prep by hand.
I would oxalic first, then acetone and continue to use the wet n dry method by hand. A firm foam, flexible backing pad would help and also adding a few drop of detergent into the water to assist slip.
As you probably know already, just listen out for any grit caught under the paper.
lw395
Well-Known Member
Just don't drop the sander in the bucket of water as I did.
The bearings failed about 2 years later....
Seriously, use a well tested RCD and it's Ok.
But I'm not convinced it's much quicker than doing it by hand.
And it's messy.
The bearings failed about 2 years later....
Seriously, use a well tested RCD and it's Ok.
But I'm not convinced it's much quicker than doing it by hand.
And it's messy.
mickywillis
Well-Known Member
RCD and generator not earthed eh? Won't work as the RCD relies on the earth path to operate correctly and protect the user.
if you do use the generator with an RCD, make sure you ground the external metalwork of the genny via the (usually supplied) grounding point on the frame.
BTW, nearly all (with few exceptions) of sanders, drills, etc are double insulated (look for the square within a square logo on the manufacturers plate) so don't rely on an earth path anyway, so in theory, you should be OK.
if you do use the generator with an RCD, make sure you ground the external metalwork of the genny via the (usually supplied) grounding point on the frame.
BTW, nearly all (with few exceptions) of sanders, drills, etc are double insulated (look for the square within a square logo on the manufacturers plate) so don't rely on an earth path anyway, so in theory, you should be OK.
