Sikaflex Prep Question - roughing up the plexi - view from the top

Snoho3 · #1 10-20-2017, 06:49 PM

Greetings - (Still) getting ready to glue my tip-up canopy to the frame on my -9A. I'm close! I've got great advice and encouragement from several of you off-line for which I am grateful, but I thought I'd throw this out there to the hive mind as I haven't seen it addressed anywhere...

I plan to use black Sikaflex primer on the underside of the aft edge of the canopy. This is the approximately aft two inches that rest on top of the roll bar. Only about 3/4 of an inch will actually be glued to the canopy frame in this area - the rest of the primer application is really just to have a consistent primer/black color on the underside of this aft edge. It will be visible from the top/outside of the canopy.

Question - if I rough up the underside of the canopy here to help with adhesion, will the roughness, i.e. tiny scratches, be visible from the top/outside of the canopy after I apply the Sika Aktivator and primer? Obviously I want the outside of the canopy to look shiny and black, and not be looking through the plexi to a scratched and cloudy surface.

Does the question make sense? Basically I don't want to rough up the aft 2 inches of the underside of the canopy until I know what it will look like from the top side after I apply the Sika. For those that went before - what did you do in this area and how did it turn out?

TIA for any guidance here.

RVRC · #2 10-20-2017, 07:06 PM

My wife and I used the primer to enhance the look. We think it came out great. Roughed up just as you mentioned. Take a look. You may also go to the link at the bottom of my signature, click on canopy and you can see more pics of how we did it and what it looked liked scuffed and primed.

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CJ in EP · #3 10-20-2017, 08:26 PM

The overhanging portion of the canopy will be scuffed and primed, as will the portion which bonds to the frame arch, the appearance will be the same, a consistent black stripe.

On mine it looks black and shiny through the plexi with no evidence of the scratches underneath.

Test it out with one of your trimmings to be certain.

Chris

Lars · #4 10-20-2017, 11:24 PM

Bluntly, no. Not even barely kinda sorta. Having done many. Mask carefully to get a crisp line. It'll look great.

mike newall · #5 10-21-2017, 04:24 AM

Ditto,

We have done a couple now - the scratches get filled with primer, you get a great outside finish and quite a durable inside finish as well.

DaleB · #6 10-21-2017, 07:51 AM

What they said. It looks GREAT.

cajunwings · #7 10-21-2017, 08:13 AM

This is another area where a ?Test? before proceeding will tell you exactly what you need to know. On a small piece of scrap (say 1x4?) sand with 4 different grits from fine to extreme and prime it just as you would the canopy and see what it looks like. You will also get a feel for how runny the Primer is and what brushes work good and not so good. Scrap is the place to train for the main event.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Lars · #8 10-21-2017, 09:46 AM

Quote:

Originally Posted by cajunwings

This is another area where a ?Test? before proceeding will tell you exactly what you need to know. On a small piece of scrap (say 1x4?) sand with 4 different grits from fine to extreme and prime it just as you would the canopy and see what it looks like. You will also get a feel for how runny the Primer is and what brushes work good and not so good. Scrap is the place to train for the main event.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Don makes a great point: practice first. I did that too, and as the result of my experiments learned that Sika primer also works great to improve the bond between the acrylic canopy and West Systems epoxy. For example, when you are laying up the windshield surround.

bruceh · #9 10-21-2017, 10:07 AM

I know I didn't do any excessive sanding of the surface before applying the primer. Pretty sure I just scuffed lightly with a maroon scotchbrite pad. You shouldn't need much scuffing, since the primer chemically bonds to the plexi.

DaleB · #10 10-21-2017, 10:08 AM

It's also very thin, runs easily, destroys foam brushes in a couple of minutes, and will eat through paint pretty much instantly - long before you can wipe it up. If you're using it inside the airplane (like for a rear window), mask well.