Fiber Glass Sanding

[jorgefife]

My boat was damaged from Ike especially on the roof top, which I had repaired
The man who did it did a great job, but is very busy to finish off, so I thought I could finish it myself
My question: what kind of sandpaper do I use? I'm in the business of wood doors and I am familiar with the work, so do I use the same?
There is not much to do, but it does not feel right, a few small bumps here and there
Then I want to paint the top, using all the tips I got from this forum, on what to do
I suppose I need a block of wood, what a pity I was not there to see what he did...

 

[Ed Schenck]

From the picture that you posted previously the area is rounded, the top radius of the cabin roof. I have one of those sanding blocks with the handle and the rubber base. I would start with 80#, then work up to a wet sand with 600#. Still think a light coat of a primer after the 120# will show up the imperfections. Then continue sanding.

You could start with a power sander if it can be slowed sufficiently. I love my Dewald orbital but it is too agressive so I always sand fine finishes by hand. http://www.alibaba.com/product-gs/260211006/Sanding_block_with_ABS_foam_handle.html

 

[sandpiper10471]

If you are painting over, I think 320 grit would be fine and no wet sanding necessary, especially if you are going to prime first and are using a random orbital sander.

I like to use a long 3M flexible fairing board. However, those boards are expensive and the abrasives even worse. The coach roof seems to be fairly flat fore to aft on the 33 and the 37 so I suggest taking a perfectly straight 2X2, about 36" long, and glueing to it some really aggressive paper - like 40. (I use sticky discs from my 8" sander) Then keeping the sanding board fore and aft and just enough pressure to scratch the surface, you will find all the bumps and hollows. Bumps can be sanded down (this is where I like my 8" disc sander for rough work (keeps it level) and the 5" random orbital for finishing)
and hollows filled.

WEAR A GOOD MASK AND COVER UP ALL EXPOSED SKIN or you will be scratching for months. I use a paper suit and tape the sleeves to the gloves.

 

[rardiH36]

Hi Jorge:

Just in case you haven't discovered this sandpaper product yet, I've had great success with Norton's 3X's brand. Since I first started using it about 7-8 years ago, I've haven't bought anything else. (Except for the black wet/dry paper for wet sanding.) The 3X's stays sharp for an incredibly long period of time and resists buildup. Buy it in the JobPack size of 20 sheets. Instead of heading off to the hardware store for sandpaper at the beginning of each project, I find one job pack can keep me going for a year or two. And I use sand paper for lots of things. I use 100 grit (which cuts as fast and last longer than most 80's), 150 and 220. Left over pieces often carry-over from task-to-task.

Maybe other manufacturers have similar products, but with my long time appreciation of 3X's, I haven't felt the need to look/try.

Home Depot carries 3X. Here's a link to the Norton 3X web page:

http://www.nortonconsumer.com/SheetsDIY-3X.aspx

 

[jorgefife]

Thank you Ed; just the answer I needed
Rardi and Sandpiper: thank you also for fine advice.
I happen to be very proud of the work I did over the almost 2 years I have had this boat
Please refer to my posting a couple of weeks ago under " Non-skid" ( not the " non-skid paint", I forgot to continue with the same topic!
There you will see tha damaged area, after being repaired
I have since painted that area in white, but like the idea of applying some primer between sanding, to show uo the imperfection
I wanted to point out to these pictures to show that the area is a rounded area, and not the flat part ( not much flat, at least)
I have work to do, thanks to you I will do it well!

 

[jorgefife]

Sandpiper
Just noticed the last bit " ...or you will be scratching for months..."
I have not stopped laughing for quite a while, I am good at immagining me scratching non-stop... for months
Thanks for that .
I needed a good laugh

 

[jorgefife]

Rardi,
If that Nortons works for you, I will go for it: in South Africa,, where I lived for 25 years, Norton Abrasives was the best in the business, and I used to buy their products for restoring cars ( a hobby I once had with 59 Cadillacs: had 5 in 25 years, all coupe de ville)
Will use the same.
I assume the pack you mentioned has all the different grits in the same pack...

 

[sandpiper10471]

For random orbitals, my preference is hook and loop by Klingspor. When the tooth is gone, I save the discs for wet sanding. The velcro type back keeps the paper from falling apart. I tend to do wet sanding work down below and on bottom paint in order to reduce dust issues.