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Canopy Ruined

B

bkthomps

Well Known Member
Sika Primer got past the tape and onto the glass, I believe this may be removable but the odd part is the white portion here, it appears to me that maybe sika cleaner/aktivator might have caused this, when is scrape it off it comes off very "gooey" and then there is a definite depression where this spot is, as if it has eaten into the lexan

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Thoughts? Help?
 
Damaged Canopy

Man, I feel your pain. I've spent a couple of weeks, replacing my canopy. It cracked on a very cold day, in front of Jay's RV Central. At least I got several years of flying out of it.

If your Lexan has melted, and there in an low spot in the surface, it will be weakened there, and can not be polished out. Your option will be to fly it as is with this optical defect, or replace it. Removing the Sikaflex might damage the frame's powercoat finish, and may need repainting prior to installing the new glass.

The Doll has been flying for nearly twelve years, so I'm using this experience to make some repairs. I welded up and re-drilled a few of the oversized #30 holes in the canopy frame. I have corrected a building error by extending the canopy skirt forward to match the canopy glass along the front edge. When the weather improves, the frame and skirt with get fresh paint. This repair will take me longer then the original build time.

Good luck with whatever you decide to do.
 
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Actually, I bet you can carve/sand that until you get through the milky goo. Then polish. Yes, it will be weaker there, and yes it will look distorted although clear. If it comes out too ugly all you've done is practice polishing acrylic (not lexan). Go ahead and do it so you can judge the ugliness.
As an aside, If Sika primer does that to plexi, I'm not getting it anywhere near my plexi stuff. Its no wonder it sticks if that's how it works. After seeing that, I'm actually surprised nobody is seeing crazing around the fillet edges.
 
i'm not entirely opposed to the idea that this damage existed prior to me doing the sikaflex process, i.e, from van's- merely because it follows the contour of the "wrinkled" plastic protective wrap on the inside, it just seems unlikely

I think the most plausible explanation is that the sika cleaner/activator product, which chemically preps the plastic for the primer, got under the plastic protective wrap and bad things happened, if that is not how this stuff works, someone please tell me

I am going to try to reproduce this on some scrap pieces.
 
Primer, two types

I didn't see anything on my installation that appeared to eat the plastic like that! What version of the primer were you using?
 
bkthomps said:
...as if it has eaten into the lexan...
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You have my sympathies about the bad spot on the transparency. That is really unfortunate.

But one minor point: I'm pretty sure that most of the Vans transparencies are Plexiglas or similar acrylic plastic, not Lexan or other polycarbonates.

The exception, of course, is the RV-12 aft transparency, about which some folks have complained because it seems to be susceptible to cracking when exposed to gasoline. But other than that, I think it is acrylic all the way.

Thanks, Bob K.
 
Brian

You may be okay. If the black primer surfaced was not scuffed up it may peel off. I to got some drops and smears both on the plex and the frame. After it dried I merely rubbed a thumb nail on it and they all popped off. Don't dispair yet. Try a thumb nail. Best of luck, Bill, RV-8A N288WP Forsyth, Ga.
 
Lacquer thinner will do exactly that to plexi right now. MEK will do that to Lexan. Toluene, naptha, and even MEK will not do that to plexi unless contact is prolonged (like seepage under the protective film). Once again...yuck.
 
...what aerhed said.

Sika Aktivator is almost pure isopropyl alcohol, per the MSDS. Extended contact might cause crazing, but not melting, and it's volatile enough that I doubt the gap in the protective film could contain it well enough to do the damage.

As for the primer, scrape it off with a razor blade. Have fun learning to polish acrylic. I've been using the Scratch-Off kit that Van's sells. I had one big scratch on my windshield, it worked very well. Also works great on motorcycle helmet face shields :) Looks like that's by the aft bow? If so, it may be partly covered by the canopy skirt. If not, you won't normally be looking back that far anyway. If it's up front, buy a Koger Sunshade. When it's closed you won't be able to see the damage from the inside, therefore it doesn't exist ;)
 
does anyone have any documentation that activator is just alcohol? it smells like it but this is surely due to that, if it was primer, it would be black, instead it's a white goopy substance that peels
 
new canopy on order, sorry guys, i am a perfectionist.

Keep the suggestions coming, I am going to turn this canopy into my plan B alternative
 
bkthomps said:
does anyone have any documentation that activator is just alcohol? it smells like it but this is surely due to that, if it was primer, it would be black, instead it's a white goopy substance that peels
Click to expand...

Look on Sika's site for the MSDS. It's listed there. They specify it as isopropanol, aka isopropyl alcohol. With some sort of titanium compound additive.

Found it. Here you go.
 
bkthomps said:
new canopy on order, sorry guys, i am a perfectionist.

Keep the suggestions coming, I am going to turn this canopy into my plan B alternative
Click to expand...

No apologies needed, other than to your bank account.

I suggest tearing all the protective plastic off the next one, then applying your own. A heavy grade painters clear plastic drop cloth from your favorite hardware store with lots of masking tape works well. Point being to eliminate the voids and gaps in the stuff applied by the canopy manufacturer. Been there, done that.
 
new canopy measured, trimmed, and finally cut to separate front windscreen from actual canopy part

I have been taping and masking off the glue line all day, I am going to take a rest and recoup a bit and then try to get some cosmetic things addressed, I may lay glue as soon as tomorrow or the next day....again, emphasis on patience here

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here's how i am avoiding this on the second attempt:

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okay, progress, first layer of glue is drying, i'll give it 48 or 72hrs before i come back for a cosmetic coat

the weights are to keep the rear portion of the canopy lying flat with the curvature of the frame, all of this is basically holding it in place while the adhesive cures

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Ruined canopy is in the background of this shot
 
Let me just say, 3M 471 Tape is awesome

removed the cosmetic tape lines, looks great so far, couldn't be happier- last pic is of it covered to prevent dust and what not from getting on the primer while it dries up in case i do have to add more

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