Sanding- Half Moon Gouges

General Discussion
1

Hey guys

Just finished sanding hot coat on my first board...yeeeeoooowwww!

it has come up not too bad for not having sanded anything before!

One query;

I was using my ryobi variable speed sander with 7" pads. I noticed that i have left some half moon shaped gouges, around 50mm or 2" long mainly on the bottom. They seem to be slightly deeper than the smooth sanded surface adjacent to them...I am wondering if I should try and 'chase them out' with the fear of going through the hot coat if I keep goping...or whether I should just consider how to avoid them next time....I have another blank ready for glassing now!

Any clues?

I have been thinking that they might be caused by the edge of the pad 'catching' the surface as I pull the sander away or change direction? Was wondering if I tried to keep a more flat contact with the board that they might be avoided...also wondered if disc speed would contribute at all?? At what grit level are they likely to be being caused?

Thanks again for ya help

Marty

2

Check your pad… there might be an irregularity in it.

3

most likely this is the result of to much pressure on one side of the pad.  It takes time to learn how to apply the right amount of pressure to effect the sanding without creating to much pressure that results in dishing.

4

hey NJ

Pads are brand new...same with the sanding discs!?

Im thinking its got something to do with letting the edge of the disc strike the surface as I lift away/change direction..as the shape of the mark is curved and fits the cruve of the pad when line up against it.

grrrrr frustrating! these marks only seem to appear when I go to the final grit (320..as per glassing 101!) but I think they might be being left by one of the lower grits?

M

5

if I may ask,

what are your sanding grit steps?

6

hey ken...of course!!

started at 80...then 120 (would have 100 but could only get 120) then 240 then 320.

Kind od followed glassing 101 by JC , think he uses 80, 100, 220,320...states that a lot of guys dont go to 320, stopping at around 220...I went to 320 just to see how all the grits went!

Marty

7

copy paste from industry thread: maybe this is your problem?

The Power Pads are superior because of the bevel....it's easy to float the sander along (even with one hand while grabbing a squeeze bottle of soapy water while wetsanding or whatnot. For a novice it's the best choice too because you are far less likely to 'dig' into your work causing sanding cuts that you will be tearing your hair out later when you gloss the board.....you will never get those cuts out once you discover them under the gloss.....just figure you will be resanding the whole damn board and reglossing. What fun. 
8

What kind of pad are you using and what desity. It sounds like the pad may be to soft with you holding the angle of the machine to great when applying presure. Mahalo,Larry

9

80 grit ??? only to knock down the big lumps

I start with 100 on a powerpad and then block it with 100 or 120 to get extra flat then gloss

if a sanded finnish 100 220 320 and maybe 400 if wanted

10

im using pads I got from SHAPERS AUSTRALIA...using both the hard version, and soft version.

Using 80 at the start, just getting bumps down and moving on to 120, 240 320 removing light scratches as I go....these moon shape gouges only seem to appear when I get to 320; im really getting a great smooth finish all over, but then these 'gouge marks' appear...they arent very deep at all, I can JUST feel their depth if I run my finger over them.

Interesting info on those power pads, might have a look at those...bevelled edge on the pad may help as the 'moon shaped gouge' fits the exact profile of the edge of the disc...I've checked disc placement on the pad and all edges of pad and nothing seems obvious there!

some good thoughts and info coming through though.....

M

11

You got a crappy sanding technique..that's all.  You must keep the pad flat.  You are digging in on an angle and thats whats making the moon divots.  Stand on one side of the board and work the other side....always! Keep the machine flat, and always keep the maching moving in a slow methodical pace.  If you need to sand contours on deck rails etc, use a softer pad!

 

It sounds like you got too hard of a pad, and your working too much in one spot...let me guess, you got the moons around the fin boxes or the nose laps?

 

If you are going to do a gloss coat, you can stop at 100 or 150 grit. The gloss needs something to bite and hold too, and the gloss will fill 100 and 150 scratches no problem, any thing higher than that is just wasting time.....and higher grits will not get wobbles out of crappy lap lines. Only good techinque, sanding flat with good strong grits will make things flat.  Higher grits will only make your wobbles really shiney.

If you are going a sanded finish.....well then you still need to shoot the sanded hot coat with something.  If it's a UPOL or a thin clear coat, then you need to sand to 320 grit. Sand anything higher will potentially lead to cracking or slabbing of the clear coat...remember the finish needs something to grip too.   If you think sanding a finish to 400 or 500, or 600 grit then glossing or spraying is good  its not.    Only sand to 500 or 600 when you are finished and trying to make it shiney.

One more thing before I crawl back under my rock. Yes you can chase those swirls out. 99.9874 of the people who sand surfboard for there first few do not sand nearly enough. You probably put a big ol thick hotcoat on that chunk of foam.  I'm betting you could sand for another 30 mins and be fine.  Sand away Salt Bush....Sand away! You will be fine.

12

hey resin

thanks for the tips mate!

yeh Im kindad going along with what you say here...technique is probably biggest factor...I rekon I was using the edge of the pad to concentrate on a few high spots and probably should avoid this. its funny but most of the 'moon gouges' are on the flats, around the centre of the board, up towards the nose....mainly on the bottom??!!

I might step down to a MEDIUM pad instead of the HARD and also use my current soft pad.

Think your right, I might try and chase them out, ill have another look and see how bad they are with chasing them out in mind!...there isnt actually heaps of them...but enough to bug me!

Everything else seemed to come up pretty good, so Im thinking the grits im using were ok, just gotta remember to keep the pad FLATTER (not use its 'edge' to concentrate on high spots)as where there isnt a gouge, there is smooth sanded finish!

Any tips on what hardness pads with which grits etc??!

Cheers again guys

Marty

13

When i started to sand my first boards, I bought a cheap variable speed sander, and pads from shapers australia, they were sold in a pack of 2 density (hard + med) for a price I found pretty cheap, I bought a soft pad also. The sander/polisher was not powerfull enough to sand in low speed, but was a good tool for the price. I made a lot of gouge on my first, and then found that and my laminating skills and my sanding technic were the biggest issues. It took me some times to get the trick, but on my 4th i started to have a pretty good polished gloss finish.

My sander fried on my 7th, so I decided to buy a new one from a brand name with new pads in smaller size. I wanted to try powerpad, but bought flexpads pads as powerpads are only 5/8 threaded and can only use glue on discs(too bad I’m in france and use velcro discs).

For some reason, I didn’t have the chance to try all of these stuffs and finish my board yet but after a closer look on my pads, I think I will have best results with flexpads.

Densities are not the same beetwin the two brands, they are not made the same way nor with same material; soft density pad from shapers au is more like the ferro supersoft and is great for rails and finishing, but not so good at taking the bumps out, I found the medium pretty stiff and the hard unbalanced (maybe my cheap weak sander was the problem).

 

So when I will be able to finish my board (sanded hotcoat), I will do this

  1. Do my best to have a good flat an smooth hotcoat to start with

0.b. Keep the sander flat all the time, and let the weight of the sander push on the surface

  1. Flexpad(/powerpad if you prefer) Hard with 80: take the bump from flat surface (ie deck, laps)

  2. Flexpad(/powerpad if you prefer) Medium with 120: take sanding marks from 80 out and lightly sand light curves

  3. Flexpad Medium(/powerpad if you prefer) with 180: same as for the 120 grit

  4. lightly hand sand rails up to 180

  5. Flexpad(/powerpad if you prefer) Soft with 240: Sand all the board (low speed on rails) and blend all the surfaces together

6 Shapers Australia pad soft with 320: Smooth all the board at pretty low speed

7 Have a shower and a cold drink!

 

I’m just a noob, a lot of guy here could probably have a better finish than mine just with 3 different grit on a soft pad, but I think it will be great.

14

I love the "Shapers AU" pads !  their OK don't blame the pad you're using , only your technic and grit.

first of all, you should learn how to apply a smooth , flat hotcoat .   when you start with a smotth hotcoat , sanding is very easy!

you should also be more aware of your disc angle and get the feell for it.    go as flat as possible.

I would recomend you strt with a hard disc on the flats , 120 grit is a good mellow start.  when you get better you try lower grits.

then go for the rails -  sand the mid rail tape line by hand 120 grit, then lightly sand the rails by hand using 120.

then grab a medium pad , 120-220 for the entire board , don't touch the rails.

you can now finish rails by eighter hand sanding 220 or if you feel confident enough , use medium/ soft pads , 220 , low rpm.

if you haven't sanded through the glass to much , go for a scuff-buff, meaning you go higher to 320 and 400 and then

polish/wax with a wool pad.

 

KEEP YOUR PAD FLAT!!!

 

KEEP IT FLATTER!!

 

THAT'S NOT FLAT DUDE!!

 COME ON....

 

KEEP IT FLAT!!

 

Aloha,

Lee

15

 

Hi Lee, no misunderstood, I like them too, and Shapers AU stuffs are really good, and guys there offer good services! I had great finishes with my Shapers AU pads and will use them until they die, but my only problem was with the big hard pad that made my sander rumble at full speed (the sander was not powerful enough to sand on low speed),  but as I said the sander was probably guilty for this. And again densities and material are not the same from a brand to the other, it’s not really a problem, just a fact.

16

hey guys...im pretty happy with shapers pads, and I'm pretty happy to blame my technique here!

as mentioned, 95% of the board top and bottom is great, just these random gouges spoil it...I gotta get my pad flatter, flatter flatter!!

Thanks for the tips on the grits versus pad stiffness and the ideas on process/order of sanding, will definitely use these on the next one....hopefully glassing this week or next.

Cheers Marty

17

I know , here on swylocks we all think of a surfboard as a form of art and do our best to have it done perfectly.

I've seen so many production boards sanded like hell,  halfmoons, arcs, spirals, sandthroughs...you name it , I've seen it.

the point is that on the bigger scale , the industry thinks of a surfboard as a functional , shortlife piece of foam,

 

don't be hard on yourselves,  having a non-perfect board doesn't mean shit about the fun you're gonna have riding it.

anyway it's gonna get dents , dings etc.....