Csail
N/A
I bought a tender (unfinished project) and want to get a good smooth finish on top of the carbon kevlar matting. What is the best way?
GRP surface finish
- Thread starter Csail
- Start date
Grajan
Well-Known Member
Epoxy filler applied sparingly "he who puts it on takes it off"
it can be hard work rubbing it down!!!!
Polyester car body fillers might be an option but no where near as tough /hard, and adhesion could be iffy
it can be hard work rubbing it down!!!!
Polyester car body fillers might be an option but no where near as tough /hard, and adhesion could be iffy
oldsaltoz
Well-Known Member
G'day Andy & Lisette,
Building in carbon fibre is the best way to get maximum strength and minimum weight.
It would be a shame to bog it down with heavy layers if anything, so I would suggest you mix some epoxy resin with Micro-balloons and spread it over the areas you want a mirror finish on.
If you apply a thin coat of resin and wait till it starts to tack off, then apply the resin and balloon mix using the back of an old straight back hand saw you will eliminate a lot of sanding.
Let this first layer cure for 24 hours or more, then wash with a running hose and rub with a plastic kitchen scourer, the small green square one with a yellow foam backing is good, start at the highest point and work down, rub till the water no longer forms beads, this only takes minutes and no harmful chemicals are required; this removes the residue left on the surface by the chemical curing process.
You will have some small low areas (still shiny) after sanding, refill as above and wash as above after it has cured.
The sanding must be done with a long board also known as a torture board, though the area you are looking should not be a problem at all.
The trick to using a long board is to push and pull around an imaginary figure of 8 laying on its side, and each time you get back to the start of the 8 you move to a new start point a tiny bit less than the width of the board, so each figure 8 overlaps the last. Good fun this......
To make your own board, first get some 250 grit sand paper in roll form. take note if the width, it should be close to 100mm wide, cut a bit of 3 ply 90mm wide 900mm long, making sure the grain on the top and bottom layers is running parallel to the 900mm leaving one middle layer cross grained. drill a couple of holes about 100mm from each end and countersink them, use these ti screw on two off cuts to form hand grips, 20 by 40mm is OK.
Fix the sandpaper as follows; remove the handles, put the start of the paper under one on the handles and pull around the end of the board and ensure it is aligned properly with a small overlap each side of the board, now pick up the end of the board holding by the end so the paper does not move, refit the handle screws with the paper between the handle on top of the board and the board trapping the end of the sandpaper with the screws; Now put the board down on a flat surface handle side up and pull the sandpaper around the end and just past the handle position on the top and cut it off there. Clamp the end with a good bull dog clip or vice grips; the paper must be tight when you screw the remaining handle on; if you have any trouble doing this try putting a small packer (pencil) under the board but over the paper and press both ends of the board down on the flat surface, then clamp the end and screw, the bending will shorten the board and make the paper tighter.
Make sure you wash any cured resin BEFORE you add more resin or primer etc.
When ready to start painting, apply some high build epoxy primer, give this a light sanding after it has cured and apply a good quality long chain polymer polyurethane paint that will dry so hard and smooth you will not be able to write on it with a pencil, and it will take the knocks and last for years.
Avagoodweekend......
Building in carbon fibre is the best way to get maximum strength and minimum weight.
It would be a shame to bog it down with heavy layers if anything, so I would suggest you mix some epoxy resin with Micro-balloons and spread it over the areas you want a mirror finish on.
If you apply a thin coat of resin and wait till it starts to tack off, then apply the resin and balloon mix using the back of an old straight back hand saw you will eliminate a lot of sanding.
Let this first layer cure for 24 hours or more, then wash with a running hose and rub with a plastic kitchen scourer, the small green square one with a yellow foam backing is good, start at the highest point and work down, rub till the water no longer forms beads, this only takes minutes and no harmful chemicals are required; this removes the residue left on the surface by the chemical curing process.
You will have some small low areas (still shiny) after sanding, refill as above and wash as above after it has cured.
The sanding must be done with a long board also known as a torture board, though the area you are looking should not be a problem at all.
The trick to using a long board is to push and pull around an imaginary figure of 8 laying on its side, and each time you get back to the start of the 8 you move to a new start point a tiny bit less than the width of the board, so each figure 8 overlaps the last. Good fun this......
To make your own board, first get some 250 grit sand paper in roll form. take note if the width, it should be close to 100mm wide, cut a bit of 3 ply 90mm wide 900mm long, making sure the grain on the top and bottom layers is running parallel to the 900mm leaving one middle layer cross grained. drill a couple of holes about 100mm from each end and countersink them, use these ti screw on two off cuts to form hand grips, 20 by 40mm is OK.
Fix the sandpaper as follows; remove the handles, put the start of the paper under one on the handles and pull around the end of the board and ensure it is aligned properly with a small overlap each side of the board, now pick up the end of the board holding by the end so the paper does not move, refit the handle screws with the paper between the handle on top of the board and the board trapping the end of the sandpaper with the screws; Now put the board down on a flat surface handle side up and pull the sandpaper around the end and just past the handle position on the top and cut it off there. Clamp the end with a good bull dog clip or vice grips; the paper must be tight when you screw the remaining handle on; if you have any trouble doing this try putting a small packer (pencil) under the board but over the paper and press both ends of the board down on the flat surface, then clamp the end and screw, the bending will shorten the board and make the paper tighter.
Make sure you wash any cured resin BEFORE you add more resin or primer etc.
When ready to start painting, apply some high build epoxy primer, give this a light sanding after it has cured and apply a good quality long chain polymer polyurethane paint that will dry so hard and smooth you will not be able to write on it with a pencil, and it will take the knocks and last for years.
Avagoodweekend......
Allan
Well-Known Member
Andy, I may be teaching Granny to suck eggs but! If you want a good final finish I recommend you use a trace coat. When your primer is hard enough to sand spray a light coat of black paint over the surface. We used to use spray cans. Then when you sand it with a block you can see any imperfections. If this shows up large imperfections, you can just refill with filler. If you need a compressor I have one you can borrow.
Allan
Allan