Fairing my new transom

[bobm]

I have just rebuilt the transom (approx 30" by 70" biaxial cloth over plywood) of my 18 foot center console boat and need to fair it before painting with Awlgrip using the roll and tip method. My concern is to get a nice flat surface for glossy paint, smooth enough to not show a lot of imperfections.

I am using West System epoxy resin with their 407 filler and also have their 410 but have not used it on this project yet.

I usually sand with an 8 inch 3M pad on a Milwaukee sander/polisher and a Porter Cable random orbital palm sander and also by hand. I have never used a long board for sanding and wonder if it has an application here. If so, what should I get, where should I get it, and how do I use it?

Thanks

[Figment]

Yes.

Get the longboard (and rolls of sticky sandpaper) from Jamestown, or make your own.

Apply the fairing compound with a notched trowel. This cuts the effort of longboarding in half, because you're cutting down half as much surface area.
Find something (a nice straight 3/4"sq stick) to use as a fairing batten. rub some carpenter's chalk on it, then draw it across the transom. The chalk will stick to the high spots.
Take a few strokes of the longboard on those high spots, do the batten routine again, repeat repeat repeat until the chalk distributes evenly on what is then a nice fair surface.
Alternate the angles of the fairing batten and the strokes of the longboard so that you're fairing in all directions.

Once you have the troweled compound faired to your satisfaction, apply a second coat of compound to fill in the notches. Tint this application of compound with some of that white pigment that West sells. This will allow you to STOP sanding that second application when you see the color of the first application showing through.

IMHO, a dead-flat surface is much harder to fair than a curved surface, so be patient and cut yourself some slack, it's going to take several steps to get it right.

[Zach]

Deleted.

[Zach]

Edited:

I use the 3m marine boards (Not the one with aluminum plate... the plates bend if dropped...)
Mirca heavy duty sandpaper is the best for fast cutting. The green 3m production paper is junk.

I use 3m 4 1/2 gold sticking paper on home made boards, and a flexible 3m board.

I use 3m's yellow stickit inline sander for a lot of small jobs that just need a quick scuff.
*Scratch that. The last two I bought, the pad fell all to pieces and vinyl fell off. They used to be good. They really aren't long enough to make anything flat.*

I use hutchins white flexible inline for doing curved surfaces as it blends wonderfully...
http://www.jamestowndistributors.com/us ... nches+long

Here is the pneumatic inline I use. It takes a hoss of an air compressor to run successfully. They take 11.8 cfm. The pad wears out after 150 or so hours of use. Can't sand something flat with a pad that isn't. http://www.jamestowndistributors.com/us ... tal+Sander


I do like sticky paper for the small inline size, the 3m marine fairing board works better with hookit...

Hope that helps you along...

Zach

[Quetzalsailor]

I made a longboard using a piece of hickory and a couple broom handle sections for handles. Good enough for the continuously changing curved surface that I was fairing.

Adding just a smidge to the previous posts:

Try to arrange that you're fairing the same stuff across the width of the work. Harder patches of filler won't sand at the same rate as softer. And, it really shows!

I wet the surface uniformly in order to see irregularities in the reflections. Handy, and easy, if you're sanding with wet-or-dry.

Have a look at the rest of your hull and at other production 'glass boats. You'll be surprised how bad, unfair they are! You only have to approach perfection more closely than the rest of your boat. If the transom is somewhat curved, apparent perfection is more easily achieved. You only have to look at the float glass windows of most recent (30-40 years) buildings to see how hard it is to get a flat surface flat!

[bobm]

Thanks for all the feedback.

I googled making my own long board and got some ideas and made my own from some 1/2" marine plywood scrap, 22" by 4.5". I will be able to cut a single sheet of sandpaper in half and cover the board. This project is adding up in terms of dollars invested, with a long way to go. Therefore I passed on the $50 3M boards. McMaster Carr has some nice sticky backed 4.5" rolls of sandpaper, but at $30 each and needing more than one grit, I will try to make due with cutting sheets in half.

I live in NJ and have a number of weeks of 60 and 70 degree weather opportunities left. i will try to fair the transom by the end of this weekend.

[Zach]

Deleted...

[Zach]

I wanted to correct something above, as I was searching around the archives.

The faster and easier approach lies much closer to Figments method.

I've been changing my tune, and the vast majority of bulk fairing should be done in the epoxy and fairing compound and 36 grit. 1/2 inch or 3/4 plywood long enough for two pieces of sticky back paper will do the trick.

Awlgrip:

Awlquick and ultra high build have their place, and also the 2 -3 day time window of easy sanding comes back and bites your behind.

The solvent has to get out of the primer, before you do any shaping. If it still smells like solvent when you are sanding or even thinks about gumming up the paper don't mess with it.

Ultra build will cover from pink puttys 36 grit sanding scratches. It is hard, which gives you a barrier that you can't easily cross without being dumb. If it can be made straight and true with 36 grit, you can spray ultrabuild. Then awlquick will cover 80 grit in 1 coat where 545 requires 2.

Awlquick is a pin hole filler, and can be smeared into the pin holes and texture with a squeedgee. It is akin to a flow coat of filler like pirannah putty.

Brown high build takes a half a life time for the solvent to escape, and the coating thickness must be followed or it will continue to shrink as the solvent works out. It is almost impossible to roll a thin enough coating of the stuff not to have shrinkage problems a few weeks later.