Bonding to acrylic

[Andy Lamborn]

Can anybody suggest an adhesive and preparation technique for bonding fiberglass to plexiglass (acrylic)?

I cast the combing around the front of my canopy and removed it for trimming and and sanding. I assume its more traditional to lay it up in place and leave it, but I couldn't think of a way to do that and get a nice finished edge around the part.

I plan to bond and rivet it in place. I'm wondering whether Proseal or a resin/flox slurry will bond well to the plexiglass.

Thanks,

Andy

[OneTwoSierra]

Originally Posted by Andy Lamborn

I assume its more traditional to lay it up in place and leave it, but I couldn't think of a way to do that and get a nice finished edge around the part.

The 9A plans describe a method that works great - using several layers of electrical tape and sanding down to them, leaving the fiberglass in place.

If you're attaching a pre-formed/pre-cast part, I'd be concerned about gaps between it and the plexi. You'd have to use something that would seal up that edge really well. I would think fuel tank sealant would work (then you could wipe a nice, clean edge before it set.) You'd have to rough the plexi to keep it from de-bonding.

Good Luck!

[BruceMe]

Glass to plexy is pretty easy; just scuff everything up nice and epoxy. Glass or plexy to aluminum is the tough one (because of expansion). The tape method keep everything nice and clean. There are plenty of good sources on this.

[Mel]

Be sure NOT to use polyester resin. It will attack the plexiglas.

[Andy Lamborn]

BruceMe,

Can you elaborate on dealing with the effects of expansion or suggest a source?

Thanks,
Andy

[RV8N]

I used pro-seal to bond the fiberglass down to both the plexi and the aluminum. It's been there almost 4 years and it ain't coming off! I wouldn't change a thing.

Karl

[BruceMe]

Originally Posted by Andy Lamborn

BruceMe,

Can you elaborate on dealing with the effects of expansion or suggest a source?

Thanks,
Andy

Easy... Sika! This is "the new way" to do canopies. Todd's Canopy has a good write up on how it's done.

http://www.toddscanopies.com/bondrv8.htm

I did it, works awesome and there's no reason it shouldn't last as long as the plexy.

Enjoy,

-Bruce

[Charles Wilhite]

Bonding anything to acrylic is difficult. It is not very receptive. Polyester should be avoided. Fuel sealants such as proseal are not menat to be used as an adhesive. They are sticky and will seal. And they do stay in place. But a strong bond from epoxy adhesives works best.

IF you choose to use the Sika adhesive, a urethane, you must read and follow the instructions exactly. I recently took a windscreen off that had been bonded using this technique. The builder was very precise and still there were significant areas where the bond was very weak and ealily pealed away.

Bonding epoxy to aluminum or acrylic requires some specific techniques as well. Everything must be very clean. I avoid strong solvents as they may interfear with the bond if not completely evaporated. I use an alcohol and water cleaner as the last wipe. Sand the acrylic with 80 to 180 grit paper, after cleaning. Sand the aluminum at the last moment. Exposed aluminum starts to oxydize in seconds, so I sand it one last time after I mix the epoxy. Then brush on a coat of resin to seal it from oxygen.

Your technique of making the part over a tape then bonding it after sanding a nice edge works well, if the part is formed well. You should dry fit it and tape the edge so your bonding adhesive that squeezes out can be easily wiped off. Then mix epoxy, and for this West is a good choice because it has a rather high flexibility and will easily absorb the minor expansion differences in materials. Use flox as a filler to make a past sort of like peanut butter or just a little thinner. Paint a coat of pure epoxy on all surfaces, spread the flox mixture and squeeze it all together. Wipe off the excess that came out. If you didn't squeeze some out, check if you used enough. Have tape ready to hold it all down while curing. I use a lot of stretch wrap for this as well. Just wrap the whole front of the plane.

Hope this helps.

Charles