Porthandbuoy
Well-Known Member
The question is: Do I have to take the deck back to bare wood, or is it okay to simply sand back to a firm base? I've got pigment and non-slip beads, so it's not as if I'm using it like varnish.
Coelan; surface preparation
- Thread starter Porthandbuoy
- Start date
Mirelle
N/A
I recommend going back to bare wood.
The Coelan will bond well to the paint - but how well is the paint bonded to the wood?
Since Coelan moves with the wood much more readily than paint does, there is a very real risk of the paint detaching as the wood moves, over time, and thus taking the Coelan off with it.
Given the cost, and the durability, of Coelan, you hope to only do this job once, so its worth taking the extra time.
The Coelan will bond well to the paint - but how well is the paint bonded to the wood?
Since Coelan moves with the wood much more readily than paint does, there is a very real risk of the paint detaching as the wood moves, over time, and thus taking the Coelan off with it.
Given the cost, and the durability, of Coelan, you hope to only do this job once, so its worth taking the extra time.
Porthandbuoy
Well-Known Member
I thought that would be the case, so went out and bought a belt sander.
oakum
Well-Known Member
Take it back and change it for a random orbit palm sander - belt sander will chew up wood
Porthandbuoy
Well-Known Member
Umpteen layers of paint chewed up my random orbital palm sandpaper. Also took far FAR too long to get down to the wood. The belt sander has done a great job on the coachroof today; tomorrow the deck.
oakum
Well-Known Member
sorry - meant for final smoothing
Porthandbuoy
Well-Known Member
And the day after tomorrow, the orbital sander.
oldharry
Well-Known Member
[ QUOTE ]
Umpteen layers of paint chewed up my random orbital palm sandpaper. Also took far FAR too long to get down to the wood.
[/ QUOTE ]
Thats because its the wrong tool for the job. Strip the paint off either chemically or with a hot air gun (doesnt char the timber like a blowtorch), and stripping knife - THEN use a decent sized random orbital sander. Those little palm jobbies are rubbish for anything but finishing off corners that the bigger ones cant reach. Its a bit like trying to paint your boat with an artists brush. Takes forever, and you will never get a good finish. Trying to strip paint off using just sandpaper is a mugs game. Fine paper just clogs up in seconds, and if the paper is coarse enough to remove paint, then it is almost impossible to stop it cutting into the wood and damaging it, digging hollows, and tearing the fibres.
Belt sanders area bit dodgy too unless you are working on a flat surface. They are meant to work flat to flat, and if your coachroof is curved, you may well find you no longer have a true curve on it, but it is full of humps and hollows where the pressure has varied as you worked across the curve.
Umpteen layers of paint chewed up my random orbital palm sandpaper. Also took far FAR too long to get down to the wood.
[/ QUOTE ]
Thats because its the wrong tool for the job. Strip the paint off either chemically or with a hot air gun (doesnt char the timber like a blowtorch), and stripping knife - THEN use a decent sized random orbital sander. Those little palm jobbies are rubbish for anything but finishing off corners that the bigger ones cant reach. Its a bit like trying to paint your boat with an artists brush. Takes forever, and you will never get a good finish. Trying to strip paint off using just sandpaper is a mugs game. Fine paper just clogs up in seconds, and if the paper is coarse enough to remove paint, then it is almost impossible to stop it cutting into the wood and damaging it, digging hollows, and tearing the fibres.
Belt sanders area bit dodgy too unless you are working on a flat surface. They are meant to work flat to flat, and if your coachroof is curved, you may well find you no longer have a true curve on it, but it is full of humps and hollows where the pressure has varied as you worked across the curve.
Mirelle
N/A
In defence of Mariposa\'s use of a belt sander...
If the paint on the decks is chlorinated rubber, as it may well be (Blakes' deck paint, for instance, is a chlorinated rubber) it won't respond at all well to a hot air gun, and gallons of stripper would be needed, but a belt sander will soon shift it.
If the paint on the decks is chlorinated rubber, as it may well be (Blakes' deck paint, for instance, is a chlorinated rubber) it won't respond at all well to a hot air gun, and gallons of stripper would be needed, but a belt sander will soon shift it.
Porthandbuoy
Well-Known Member
Re: In defence of Mariposa\'s use of a belt sander...
Thank you M'lud.
There's at least 6, possibly 7 different coloured coats. Include the probability of multiple coats of the same colour I shudder to think how many coats there are in all. One of them at least seems to be a high-build, somewhat chalky, paint which doesn't respond to heat at all. The belt sander may be vicious, but by God it gets the job done. Perhaps I should just sand back until I find a colour I like.
Thank you M'lud.
There's at least 6, possibly 7 different coloured coats. Include the probability of multiple coats of the same colour I shudder to think how many coats there are in all. One of them at least seems to be a high-build, somewhat chalky, paint which doesn't respond to heat at all. The belt sander may be vicious, but by God it gets the job done. Perhaps I should just sand back until I find a colour I like.
oakum
Well-Known Member
Re: In defence of Mariposa\'s use of a belt sander...
I been using a electrical vibrating scraper made by Bos-h last couple of days shifting antifoul - seems very effective - no dust either but got to be careful not to gouge.
I been using a electrical vibrating scraper made by Bos-h last couple of days shifting antifoul - seems very effective - no dust either but got to be careful not to gouge.
Captain Coochie
Well-Known Member
I agree , belt sander then R.O.S. The belt sander is great for getting the crap off if you know how to use one then the R.O.S for finishing .
Porthandbuoy
Well-Known Member
Thanks everyone for the advice. I'm waiting on the rain stopping before I can finish the job. The best result is definitely as Seaspray says; belt sander followed by randon orbital.
Captain Coochie
Well-Known Member
I know i have to do it with my dodgy joinery /forums/images/graemlins/blush.gif
Kristal
Well-Known Member
So, to continue this surface preparation thing (as I'm about to do it too)...
I'm going to use hot air to get the old varnish off. I need suggestions on:
1. How to protect the topside paint from the heat gun around the toe-rail (perhaps some sort of metallic sticky tape?)
2. Once the varnish is off, which level of wet & dry to use (I can't remember what the technical term is for how rough the paper is)
I'm going to use hot air to get the old varnish off. I need suggestions on:
1. How to protect the topside paint from the heat gun around the toe-rail (perhaps some sort of metallic sticky tape?)
2. Once the varnish is off, which level of wet & dry to use (I can't remember what the technical term is for how rough the paper is)
Peterduck
Well-Known Member
You'll only be working on a short section of the toerail at any one time, and it should be possible to hold a sheet of aluminium foil about a couple of feet long in place with a tab of masking tape at each end and move it as you move along. You could fold it lengthwise into two or three thicknesses if you think that a single thickness would be insufficient.
As to which grade of sandpaper, this will depend a bit upon which kind of sanding machine you intend to use. Some are more aggressive than others. Sandpaper is graded by the size of the grit used; 80 being coarse, going through 100 & 180 to 220 being fine.
Peter.
As to which grade of sandpaper, this will depend a bit upon which kind of sanding machine you intend to use. Some are more aggressive than others. Sandpaper is graded by the size of the grit used; 80 being coarse, going through 100 & 180 to 220 being fine.
Peter.
tcm
...
good idea.
Though i wd look for finer and then much finer grades than 220.
Though i wd look for finer and then much finer grades than 220.
Kristal
Well-Known Member
I was planning on getting one of those palm sanders for doing fine work like the toe rail, cabin sides etc. and a big orbital jobby for sanding back the topsides prior to repainting (with Owatrol in the mix, after the abysmal job I made last time with Blakes).
/<
/<
Peterduck
Well-Known Member
Consider one of the delta sanders such as the Fein for detail work. They are absolutely brilliant! Surprisingly aggressive, so that you quickly move on to the next patch to be sanded. Orbital sanders, however, are very gentle as they are intended for finishing work only, so if you have a large area ahead of you, you can afford to have a grade coarser than you would expect. Beginning with sandpaper which is too fine will slow the work up and leave you frustrated with the lack of progress. It will make the job seem much bigger than it has to be. If you are only taking the gloss off the last coat, then I would start at 220 grit. If you are actually removing paint, then I'd start at 100. This will remove paint well, and hopefully avoid any tendency to clog. By the way, if you do get any clogging, borrow some talc from 'er indoors and dust it onto the sheet before beginning again. Clogged paint is best removed by sanding crepe rubber, and good tool suppliers should have sticks of this in stock. Before I found a stick I used the sole of an old shoe. This was back in the sixties when crepe-soled shoes were all the go.
Peter.
Peter.
Porthandbuoy
Well-Known Member
Sanding crepe to remove clogging! That's a new one on me. Time to dig out those blue suede shoes I haven't worn for years.