Suggestions for primer on Acrylic deadlights??

[Northeaster]

Any suggestions for a primer for Acrylic deadlights?

I will be using 3M VHB tape, to adhere the deadlights to the boat (gelcoat), as well as Dow Corning 795, to adhere and seal them. (no bolts / screws)

If Acrylic doesn't require primer, please let me know, as well. Per the Sexy Windows thread, I would like to paint them with some "primer" to hide the tape / Dow 795, when looking at them from outside. The article suggested auto exhaust paint, but I figured black primer, that could actually improve adhesion to the tape / Dow 795 would be better.

Should primer be used on the gelcoat as well?

[David M]

I would rough it up real well with a ScotchBrite pad for metal (the dark red one) so you get a good physical bond.

[Alan Wheeler]

Sika have a special primer for their Adhesive sealants.

[GordMay]

Sika Primer-209N is used to prime painted surfaces and plastic substrates, such as Acrylic, Polycarbonate, & ABS, etc.
Goto: http://www.sikaindustry.com/tds-ipd-...209-ind-us.pdf

[cat man do]

Originally Posted by Alan Wheeler

Sika have a special primer for their Adhesive sealants.

So does 3m for the VHB

But seriously, I think Noreaster may be worrying to much.

The bond is only as good as the paint adhesion to the hull and I have seen windows removed that just used cheap Chinese roof and gutter sealant that actually peeled the fiberglass away from a cored hull.

Dave

[GordMay]

Most substrates are best prepared by cleaning with a 50:50 mixture of isopropyl alcohol and water prior to applying 3M “VHB”Tapes; but Adhesion Prommoters” (Primer) can significantly improve initial and ultimate adhesion to many materials such as plastics and paints.

Surface Preparation for 3M VHB Tape Applications:
http://multimedia.mmm.com/mws/mediaw...GGGNJV6c2222e-

[Northeaster]

Thanks for the replies!

As stated originally, the main reason I want to paint (with primer) the portlight edges, before applying the VHB tape (and Dow 795), is to hide the "sh$thouse" look of the tape / Dow 795, when viewed form outside. I am only using light-med tint acrylic.

If I do this, I want to also better (or not make worse) the adhesion to the acrylic.

Gord - I see that 3M suggests, 3M primer 94 - the problem is I had to mail order the tape, as there is not decent 3M store, that carries their construction stuff.

Does anyone know a more commonly accesible primer, that would work well on acrylic??

[cat man do]

I really wouldnt use acrylic as it cracks and crazes too readily.

Get some shinkolite instead (good enough for the $5 mil boats cheaper than Lexan) , nice and dark, cant see the tape and all I did was give the area a light sand with 180 grit and a wipe with metho.

They were never coming off without taking some boat with it.

Dave

[GordMay]

Originally Posted by cat man do

I really wouldnt use acrylic as it cracks and crazes too readily.
Get some shinkolite instead ...
Dave

Shinkolite IS Acrylic:
Shinkolite-A is the registered tradename of Mitsubishi Rayon's cast acrylic sheet.
MITSUBISHI RAYON -SHINKOLITE-

[cat man do]

Originally Posted by GordMay

Shinkolite IS Acrylic:
Shinkolite-A is the registered tradename of Mitsubishi Rayon's cast acrylic sheet.
MITSUBISHI RAYON -SHINKOLITE-

HMMmmm, certainly not the stuff I see on most boats.

You know, the stuff that goes purple and crazes after a few years.

Dave

[GordMay]

I believe that Shinkolite also makes a protective film product, intended to act as a barrier against UV rays, staining, and discoloration.

[cat man do]

I wasnt meaning Shinko crazes and discolours

I've never had nor heard of those problems with it

I was meaning that whenever I have heard or seen someone using what they call acrylic or perspex that that goes crazed and purple in colour.

Dave

[Alan Wheeler]

Perspex is a brand name. It is an acrylic sheeting. So is Shinkolite. But not all acrylics are created equal. There can be several different additives used to change the properties of Acrylic. There is also two different methods of making a sheet of the material. Cast sheet tends to be stronger and is often the material used in aircraft windows.
The major advantage over Polycarbonate, is that PC looses considerable strength in sunlight. After 12months, PC has less strength than Acrylic.