Gelcoat Sanding

So after attending Uncle Hank's presentation at the convention I have been
inspired to sand out the crazing in my gel coat. I am planning on the
600-1000-1200-1500 wet sanding process and then buffing out the finish.

I understand the basics, but does anyone have a good primer on the process?

Thanks

Peter

hi Peter, here's the finish sanding process I use on every glider we refinish. first let me say there are many ways to arrive at the same result. i'm the blonde guy hank called on near the end who was standing against the side wall.

i take sections of wing and draw a line with pencil from leading edge to trailing edge every 18 inches or so. then, with 800 (you can use 600) you'll sand two sections at a time using spanwise strokes, working from leading edge to trailing edge. each time you finish two sections, move up 1 section, so you are overlapping and hitting each section two times as you move down the wing. repeat the process for each grit. truth be told, i do 800, 1000, and 1500. change paper alot, it goes dead quickly. especially with old hard gel-coat.

now, for the literal coup de grâce: after doing sections of 1500, wet the whole wing down, and walk back and forth, root to tip, doing single strokes that last the whole wingspan using spent 1500. you won't be sorry. if you do a ton of that at the end, the wing will look buffed before it's buffed, and it will also shine up much easier.

if you want more detailed explanation on the actual process, email me: brayera at gmail dot com and i'll give you my number so we can talk. if your wing is crazed, don't wait to do this. the longer you wait, the worse off you are. sometimes, if you catch crazing **early**, you can save the finish. no matter what stage your crazing is at, polish hard and often from now on and you'll squeeze some extra years out of your finish.

-Andy

On Thursday, March 24, 2016 at 4:20:54 PM UTC-4, vontresc wrote:
So after attending Uncle Hank's presentation at the convention I have been
inspired to sand out the crazing in my gel coat. I am planning on the
600-1000-1200-1500 wet sanding process and then buffing out the finish.

I understand the basics, but does anyone have a good primer on the process?

Thanks

Peter

i take sections of wing and draw a line with pencil from leading edge
to
tr=
ailing edge every 18 inches or so. then, with 800 (you can use 600)
you'll
=
sand two sections at a time using spanwise strokes, working from
leading
ed=
ge to trailing edge.

Did you really mean spanwise and not chordwise??? When I worked at
S-H, we NEVER sanded spanwise. It was either chordwise or
alternating 45 degrees off chordwise. FWIW......

i really mean spanwise, when i worked at schempp-hirth 6 years ago they always sanded spanwise for finish sanding. and i have been doing it that way at a nationally known glider refinishing company for 12 years.

On Thursday, March 24, 2016 at 5:30:06 PM UTC-4, Michael Opitz wrote:
i take sections of wing and draw a line with pencil from leading edge
to
tr=
ailing edge every 18 inches or so. then, with 800 (you can use 600)
you'll
=
sand two sections at a time using spanwise strokes, working from
leading
ed=
ge to trailing edge.

Did you really mean spanwise and not chordwise??? When I worked at
S-H, we NEVER sanded spanwise. It was either chordwise or
alternating 45 degrees off chordwise. FWIW......

also, for the process i describe, you'll want to use a soft finish sanding block. like the one in the attached link:

http://homefixated.flashpointstudio....lock-Round.jpg



On Thursday, March 24, 2016 at 5:05:14 PM UTC-4, ND wrote:
hi Peter, here's the finish sanding process I use on every glider we refinish. first let me say there are many ways to arrive at the same result. i'm the blonde guy hank called on near the end who was standing against the side wall.

i take sections of wing and draw a line with pencil from leading edge to trailing edge every 18 inches or so. then, with 800 (you can use 600) you'll sand two sections at a time using spanwise strokes, working from leading edge to trailing edge. each time you finish two sections, move up 1 section, so you are overlapping and hitting each section two times as you move down the wing. repeat the process for each grit. truth be told, i do 800, 1000, and 1500. change paper alot, it goes dead quickly. especially with old hard gel-coat.

now, for the literal coup de grâce: after doing sections of 1500, wet the whole wing down, and walk back and forth, root to tip, doing single strokes that last the whole wingspan using spent 1500. you won't be sorry. if you do a ton of that at the end, the wing will look buffed before it's buffed, and it will also shine up much easier.

if you want more detailed explanation on the actual process, email me: brayera at gmail dot com and i'll give you my number so we can talk. if your wing is crazed, don't wait to do this. the longer you wait, the worse off you are. sometimes, if you catch crazing **early**, you can save the finish. no matter what stage your crazing is at, polish hard and often from now on and you'll squeeze some extra years out of your finish.

-Andy

On Thursday, March 24, 2016 at 4:20:54 PM UTC-4, vontresc wrote:
So after attending Uncle Hank's presentation at the convention I have been
inspired to sand out the crazing in my gel coat. I am planning on the
600-1000-1200-1500 wet sanding process and then buffing out the finish.

I understand the basics, but does anyone have a good primer on the process?

Thanks

Peter

I often hear that sanding is only a temporary solution, and after couple of years the gel coat will lift again and now you have a thiner gel coat layer and wider cracks. If so, why sanding unless you try to sell your glider?

Ramy

On Monday, March 28, 2016 at 12:08:22 PM UTC-4, Ramy wrote:
I often hear that sanding is only a temporary solution, and after couple of years the gel coat will lift again and now you have a thinner gel coat layer and wider cracks. If so, why sanding unless you try to sell your glider?

Ramy

So you can save up for a full refinish. A "flattening sanding" helps with the aerodynamics followed by a good wax/polish can extend the life of what you have. A full refinish is not cheap.

On Monday, March 28, 2016 at 12:20:45 PM UTC-4, Charlie M. (UH & 002 o
exactomundo.

On Monday, March 28, 2016 at 12:08:22 PM UTC-4, Ramy wrote:
I often hear that sanding is only a temporary solution, and after couple of years the gel coat will lift again and now you have a thinner gel coat layer and wider cracks. If so, why sanding unless you try to sell your glider?

Ramy

So you can save up for a full refinish. A "flattening sanding" helps with the aerodynamics followed by a good wax/polish can extend the life of what you have. A full refinish is not cheap.

Hi Ramy,

i recently read an article on you in gliding international. you are an inspiration, i can only imagines some of the beautiful scenery you must have seen!

another possible reason to sand is if you can catch crazing in it's very earliest stages you can sand away the damaged gelcoat and literally remove the crazing completely. crazing most typically begins in the existing sanding scratches on the surface of the gelcoat. that's the reason they are often chordwise, because as mike opitz indicated above, the manufacturers used to sand chordwise.

On Monday, March 28, 2016 at 12:08:22 PM UTC-4, Ramy wrote:
I often hear that sanding is only a temporary solution, and after couple of years the gel coat will lift again and now you have a thiner gel coat layer and wider cracks. If so, why sanding unless you try to sell your glider?

Ramy

On Thursday, March 24, 2016 at 4:20:54 PM UTC-4, vontresc wrote:
So after attending Uncle Hank's presentation at the convention I have been
inspired to sand out the crazing in my gel coat. I am planning on the
600-1000-1200-1500 wet sanding process and then buffing out the finish.

I understand the basics, but does anyone have a good primer on the process?

Thanks

Peter

ND gave a decent reply.

If hand sanding, start saying to yourself, "I must, I must, I must build up my bust....".
I like to say, "Sanding Gelcoat is like polishing granite with wet toilet paper".

Lot's of work.

A decent random orbital sander with disc's (going from 600 wet to 3000 wet) can make a HUGE difference. Using a block or spline board will work, but from my view, it's a LOT more work.
There's a reason a decent shop charges what they do, "they've been there, done that".

Final polish/wax also depends on the tools/wax you use.
So states the "polish guy" (job, not country..) on a number of projects.

[Someone in the shop today called me, "Buffy the dull slayer".... sorta fits.]