How far to sand exterior before painting?

[fofobraselio]

Heya,

We will be painting our boler exterior soon and understand that sanding and cleaning preperation will be the most important part of painting the trailer.

My question is, how FAR are you required to sand down the exterior?

Can you just skruff it up and leave a rough surface to prime and paint over? Or do you have to sand all the way down to the bare (brownish) fiberglass?

Thanks for your inputs

Mark

[Jim Bennett]

All you have to do is sand to a sound surface. Paint will bond well to gelcoat. Gives you a chance to fill any dings too.

[Neto]

It does not have to be a deep sanding. A clean, oil free surface and light sanding is what I would do.

[Eggcentric]

Wash the exterior very well to get rid of any wax, gel coat has wax on it, then sand to 400 grit, so there is no shine, washing with acetone is best, but not nice to use and very flamable, tsp will do quite nicely.

[rbryan]

All good advice so far. I'd say when it comes to painting anything, the smoother the surface, the better the paint job will be. Also, a few lighter coats are better than one heavy one. Will you be spraying it?

[John in Santa Cruz]

also, thats WET sand, use lots of water with 400, otherwise the sandpaper clogs up really fast. i keep a bowl of water handy, and dip the sandpaper in it a couple times a minute, and periodically rinse the whole surface.

[fofobraselio]

Originally Posted by rbryan

All good advice so far. I'd say when it comes to painting anything, the smoother the surface, the better the paint job will be. Also, a few lighter coats are better than one heavy one. Will you be spraying it?

Whew! Nice to know I won't have to get down to bare FG. I will be using the roll and tip method with at least a couple of coats.

[Delmitch2]

We used Awlgrip and simply followed the manufacturers instructions, finishing with a roll and tip paint job. Very happy with the results. I wouldn’t take any shortcuts, paint results are only as good as the prep work.

[rbryan]

Originally Posted by John in Santa Cruz

also, thats WET sand, use lots of water with 400, otherwise the sandpaper clogs up really fast. i keep a bowl of water handy, and dip the sandpaper in it a couple times a minute, and periodically rinse the whole surface.

Very good point. I use wet/dry. I'd start with 400 grit but for a really smooth surface maybe finish with 600. Since the OP intends to tip and roll instead of spraying, and the tip and roll leaves a very slight texture, I would think 600 is the finest you need to go.

[vintageracer]

Originally Posted by rbryan

Very good point. I use wet/dry. I'd start with 400 grit but for a really smooth surface maybe finish with 600. Since the OP intends to tip and roll instead of spraying, and the tip and roll leaves a very slight texture, I would think 600 is the finest you need to go.

I would not do 600 if I were you. Paint needs something to bond to and 600 is way to TOO smooth a surface for MOST paint systems to properly adhere. Do what the manufacturer of the paint system YOU CHOOSE recommends for surface preparation.

Remember this is a TRAILER and not a $50K collector car. It's a safe be that your trailer will sit OUTSIDE therefore a quality paint product that is properly applied with great UV resistance is far more important than a "Glass Like" finish that will be color sanded and buffed.

You need to specify the brand,type of paint and method of application you intend to use on your trailer to get proper advice. That will dictate the level of (tooth) or surface preparation you will need for the paint product you are using to properly adhere to your trailer and provide all the benefits the paint system you use can provide.

What Brand of Paint, Solid Color, Metallic Color and type (Epoxy, Enamel, Base/Clear, Single Stage) of paint system will you use?

Will you "Primer" the complete trailer first or just spot "Primer" over repairs as needed?

Will you be applying enamel over lacquer? Could you possibly have a paint reaction between the "New" Paint system and the "Paint" currently on the trailer?

Will you be using a "Highly Loaded" Metallic paint? This will limit your paint applications methods to spraying for the most part.

Are you spraying, rolling or brushing the paint system you choose?

Is this method of application you choose recommended by the Paint system you choose?

These are just a few of the questions you should consider before you decide how to prepare the surface of the trailer prior to painting.

As stated above PICK the paint system you intend to use, follow THEIR instructions, ask questions here as needed by providing us all the information you can and have at it!

[ststefan]

I am using interlux on our boler and the can states which grit to use before and between coats.

[David & Terry]

Got unit in 2006 (it's 1978). We cleaned unit, fixed fiberglass damage; sanded several times. Primed; then hand brushed on 2 coats of interlux marine paint, sanded in between coats. And after 12 years, it's just beginning to show cracking/blistering from heat and sun. Would benefit from being sanded and painted this year. I wish we had held up as well after 12 years !

[fofobraselio]

Originally Posted by David & Terry

Got unit in 2006 (it's 1978). We cleaned unit, fixed fiberglass damage; sanded several times. Primed; then hand brushed on 2 coats of interlux marine paint, sanded in between coats. And after 12 years, it's just beginning to show cracking/blistering from heat and sun. Would benefit from being sanded and painted this year. I wish we had held up as well after 12 years !

DUDE!

That round window, and that colour!
I feel like 12 years is not too bad for paint to last.

What paint colour / brand are you using today? Looks freaking awesome!

[David & Terry]

Painted the UNIK with Interlux Brightside Marine Enamel. Light Blue 4351
Premium Single Part Enamel