OK sanding is definately my biggest weakness. At least with everything else I feel I understand what and how it should be done, now it is just a matter of mastery, but sanding not really sure.
how do you know to stop sanding your hot coat?
is exposing a little weave in the clear coat OK?
what about in the resin tint?
Cleanlines talks about hot coat sanding starting at 80 grit and ending at 150 if gloss coating. Is this still true if doing opaque resin tints?
I have a lot of arcing marks, especially in my dark red bottom. Do I need to sand to finer grit?
Lets start with those questions. A little more background. I’m using a power sander turned down low, with an 8" Power Pad. Used the Med pad with the 80 and 100 then switched to the soft for 100 and 150. Was going to use a 120 but that put more scratches in than the 100 so I went back to 100 to clean up the little section that I started the 120 on.
Oh yeah using RR w/ 6oz glass. double 6 deck single 6 bottom. Also have rice paper lams.
sanded to 150 tonight so planning to resin pin and gloss tomorrow night and Thur so would be good to know if I should be sanding beyond 150 especially on the dark red. Oh yeah, only exposed weave on the clear part of the rails for the most part, a little on the stringer and over the lams.
Howzit?!? Slow speed with light paper works good for me with R.R. I use a fairly stiff dust brush to clean the paper frequently while it’s on the pad. It’s the dust that fills up the grit, the little gobs make the scratches. If you keep the paper clean, you can go a lot further. I sand all my laps and patches and give the glass a light scuff with a sheet of 150 before I even hot coat. A solid capful of add. F per side in the hot coat. Then I lightly sand out the few brush strokes with minimal 150, then sand the whole board with 220, 320, and 400 for a slick finish that’s as good as any p.e. For a gloss, 150 should be enough, pinline areas with a little finer paper of course. Aloha…RH
Richolt is right on da money. 1) I don’t know much about epoxy, but should work the same way. You need to do 99% of your sanding flatness before you hot coat, I take a surform to the laps, nose, and tail. Get all the drips, bumps bugs, and get the board as flat as possible. Then you can hotcoat, put the hotcoat on pretty thick, and sand it all off. Make sure you keep the sander pad flat, always flat if you start to let it ride and apply presure on one corner, thats when you get moon swirl. Hitting a little rail weave is inevitable, but thats why we gloss or seal. Hitting the weave after a gloss is a no no. A slower speed to the sander will give you more control, more bite with the paper, less clogging, and less flying dust, and your paper will last longer. Don’t move too fast over the board, let the paper and the sander pull you along, you’ll know the proper cadence for the speed and paper when it happens. Also work the opposite side of the board when stand next to it, keep the sander centered over your body, don’t let it walk out with the ol one handed, “I’m going to the nose and back trick”.Every grit has a speed and bite, like #2 setting on Big Red with 80, with medium presure. #3.5 setting with 100 grit and a soft pad, pressing pretty hard. (Poly) Hit the board with the hard pad with 60-80 grit to get it flat, then take the super soft pad (homemade with 2 in cushion foam on a med backer pad) with 100 grit and press pretty hard at a slow speed. The board should be baby butt flat and ready to gloss. If you freak about the rails, do them by hand to touch up the hotcoat overlaps.
try to stop sanding before you hit the foam…actually stop sanding when it looks good. It’s amazing that if you do a good prep job, and a decent hotcoat. When you get it sanded flat thats about the time to stop. It’s impossible to tell you when to stop via-Swaylocks, as in…stop 1/64 before the weave, but keep sanding at 1/32. Look at you sanding job in low cross lighting, this will show all the blems in the sand out. Most of your sanding will occur on the lap lines on the bottom, this is where the wobbles show up. The bottom if hot coated right should look flat from the beginning. On the bottom your just trying to loose resin weight. On resin work, any time you hit the color on the bottom you’ll get a lighter color spot. But if you hit the bottom color lam then your into the glass, and if your into the glass, then your 1/128th to the foam, and if your that close then you’ll need to patch the spot. If you are doing a rail cut lap, you shouldn’t even come close to hitting the rail color. You have a 4x4 or 6x4 wrap there, there’s no reason to dig that far into the glass…unless you had a horiffic lam and hotcoat? Then if thats the case then its a learning curve issue. And thats why I say do a heavy hotcoat. Most guys don’t sand enough, there a lot of resin that can come off of a board, and still not hit the weave too much.
Answer: sand just enough resin off to just cover the fiberglass, but not thru the fiberglass.
Answer: 100 grit is ok to stop at for gloss, it gives the resin something to hold on to. If its too smooth, and you don’t kick it hot enough, you’ll get a massive slab off…run for the hills the gloss is slabbing, look at the frickin fracture line!! It just busted off and its pulling the tape with it… RUNNNNNNN FOR YOU LIFE. If your doing pinlines, make sure the lap area is sanded to 220 grit.
Some of the best sanding advice I took away from the JC videos was the bit about the “shinies” – sand when you’ve got them, stop when they’re gone (for the lower grits at least). The rest of the sanding process is simply replacing larger scratches with smaller ones, so it really boils down to personal preference. Hitting the weave is a no no (regardless of how well you can cover it up with a gloss or a polish)… how much strength are you willing to sacrifice for cosmetic purposes?
Howzit 4est, Use your hands when sanding to feel any low or high spots and for smoothness of the rails, sometimes it's hard to see imperfections but feeling them is easier. Aloha,Kokua
For the flats, the shiny spot technique is the best. Time it so the last grit you use takes out the last shiny spots, and I have to add I love the random orbital for that.
If you feel there’s still too much resin/weight, then take your own risk at sanding more, you know the consequences. Next time try a little thinner hotcoat, but stick to removing the shiny spots. Too thin and the cloth will appear before the shiny spots disappear. The fine line of strength to weight.
The neater and tighter your glassing, combined with removing the obvious lumps and bumps, if you have any, before the hotcoat, will eventually make sanding a breeze, with little risk of sandthrough.
…dont use the harder pad (medium - up)in the deck…
…when stop?..if you ve do a good thin hot coat, you dont need to sand too much…
…dont hit the rails with the hard pad or with heavier grit sandpaper…
…if you have a variable-speed sander you should start the sanding with 100 grit not 60 or 80… ((start with 60 if youve got a bad coat…, start with 80 if youve got a non variable sander))…
…do a super sligthly sand job with the heavier grits…
…check the coat with fluorescent ligths (equal to the shape step)…
I just (sorta) taught a first timer to sand hotcoat the other day. He made a lot of arcs in the work, resulting fron poor technique. He was turning the pad on edge too much at the end of a pass across the board. Keeping the pad flatter to the board (but still at a slight angle) is important.
Pressure seems to result in faster or slower cutting.
Crap building up on the pad seems to cause fine parallel arcs. It seems to happen at the end of the life of a disc. I get this effect; I’ll have to investigate cleaning the pad or changing the disc. But I’m cheap, so for now I’ve just hand sanded them out.
I finish hot coat sanding with a quick hand pass with 220, used wet, and it hasn’t caused me problems. I think it’s more than needed, but I like the smooth finish it leaves, and it removes any tiny bits of resin that are about to break off from the machine sanding. But then I only machine with 60 grit Hermes paper, pretty rough stuff, so using a 150 disc would likely eliminate the need for 220 wet work.
Except for pinlines; as stated above ya gotta get the hotcoat nice and smooth, without touching weave, for a good pinline. 220 wet is the ticket there.
The speed you set on the sander depends on your level of control, the “feel” of the pad as you go along, whether you sander has sufficient torque to spin the pad, how hard you lean on the pad, how soft the backing is and whether it’s conforming to the curve of the board, and of course the moment-by-moment results you’re getting.
For sure you sand top of glass ! You must not see glass patern. You must do an other coat of Wax in styrène resine (they call it top coat in boat building, glass coat in surfboard building even it’s not polished) and lightly sand It.
What it looks like to me is that you used too much resin during the lam coat, causing the glass cloth to “float”, so that the glass itself is not down tight to the foam, but migrated up to the top of the too thick resin in spots. As you sand over the lower spots (where the glass is tight to the foam), you’re hitting weave on the higher spots (where it isn’t). In the end you will have to keep going until the weave doesn’t show anymore, or just write it off to the learning curve and surf it as is. Do you have any pics of the lam coat? If this is the case, next board work on using just enough resin on the lam coat to wet out, but not enough to pool and allow the glass to float up.
This thread is killing me with the awesome wording and abbreviations. Same in most households and especially in mine “I know its the GF which does the real work.” But I call her my wife now!
How does a builder offer more “dink resistance” in their construction anyhow?
…HelterSkelter, well, before to leave these threads the way is turning; in my opinion, the problem is the distance, so at some point you are taking the stuff like personal and what I tried to say about some advice from me (a person who have experience in this labor and makes a living with) turned, do not know why in a wrong perception.
-Besides that I put technical advice in your threads (plus what cloth for the inlays, etc), so do that way, however you said that there are other ways (and still you sand and sand) possibly better…then I said that s ok for me, if that s ok for you too do not know why you do not do that way and no more question asked.
Then I put that the way I do is the way of the high quality brands; because happens that there are no shortcuts there and happens that I work in that niche (included Balsa boards) so I am not guessing and tried to pass you simple yet practical way to do the stuff plus some “veteran” advice, however seemed mostly wrong for you; do not know why.
Alright, go ahead and do like that Greenlight list and the ytube clips.
I put again this: hand lay ups have 3 parts.
