Molding the windshield upper fairing lip

[PaulvS]

The plans for the sliding canopy show a fiberglass fairing that is molded directly onto the plexi windshield above the roll bar and overlapping the slider edge by 1/4" to 1/2". Obviously the fiberglass needs to bond to the windshield, but NOT to the slider. Normally I use packing tape as a bond breaker, but in this case there is a gap between the windshield and the slider and anything that is put over to bridge the gap while molding will result in the 2 parts being stuck together, forever!
How did you do the molding without gluing the two parts of the canopy together? (other than making a removable fairing and then bonding it on afterwards with Sika etc.)
Thx
Paul.

 

[Kyle Boatright]

Mask your rollbar with packing tape or your release agent of choice.. Tape a piece of thin cardboard across the top of your canopy to bridge the gap between the canopy and rollbar. Use packing tape to mask the cardboard and your canopy. Maybe add a layer of wax or other release agent on top of the canopy.

Do your layup and the cardboard should support the fiberglass while it cures.

 

[PaulvS]

Mask your rollbar with packing tape or your release agent of choice.. Tape a piece of thin cardboard across the top of your canopy to bridge the gap between the canopy and rollbar. Use packing tape to mask the cardboard and your canopy. Maybe add a layer of wax or other release agent on top of the canopy.

Do your layup and the cardboard should support the fiberglass while it cures.

Thanks Kyle. I'm not sure if I understand correctly - if there is packing tape above the rollbar then this would prevent the fiberglass from bonding to the windshield, wouldn't it?

 

[Kyle Boatright]

Thanks Kyle. I'm not sure if I understand correctly - if there is packing tape above the rollbar then this would prevent the fiberglass from bonding to the windshield, wouldn't it?

Sorry. Packing tape on the aft face of the rollbar, just in case you get a drip or run of epoxy.

 

[Desert Rat]

fyi- I looked at a couple of options to bridge the gap between the canopy and aft fuselage when I was laying up my slider faring, and finally discovered that Michaels craft store sells plastic poster board. It's only about .010" thick and a similar stiffness to a plastic milk jug. Might work for you depending on what sort of curvature you need.

 

[wirejock]

3M Heavy Packing Tape

3M Heavy Packing tape.
Mine is 1" aft of the canopy seam. Also a pocket on either side for the canopy trim to slip in.

 

[Thierry A]

Can you create a filler made of chipboard (represented in green) then use the packing tape (represented in red)...

 

[Ralph Inkster]

I have seen some folks tend to lift their canopies while sliding them forward & bashing their fiberglass fairings while closing & latching it, don't know, maybe just how they swing their arm forward I guess.
So I prefer a larger gap between the fairing & canopy, accomplished by stacking a few (4 or so) layers of duct tape on the canopy than applying a liberal amount of mould release before laying up roll bar fairing. I also make the fairing thicker/stronger to better resist damage from unknowing passengers who grab it while lifting themselves out of the seat.

 

[PaulvS]

Thanks everyone for the replies, there are some great suggestions that I hadn't considered.

Sorry. Packing tape on the aft face of the rollbar, just in case you get a drip or run of epoxy.

Ah that makes sense. I was hung up on trying to prevent any leaks by putting tape on top but I can mask inside instead!

fyi- I looked at a couple of options to bridge the gap between the canopy and aft fuselage when I was laying up my slider faring, and finally discovered that Michaels craft store sells plastic poster board. It's only about .010" thick and a similar stiffness to a plastic milk jug. Might work for you depending on what sort of curvature you need.

I can obtain something similar here, Officeworks has free offcuts of the plastic film that is used to laminate posters, it is .007" thick and reasonably rigid.

3M Heavy Packing tape.
Mine is 1" aft of the canopy seam. Also a pocket on either side for the canopy trim to slip in.

I also like 3M, it doesn't leave any residue like cheaper tapes. I will extend the lip around the side skirts also.

View attachment 51260

Can you create a filler made of chipboard (represented in green) then use the packing tape (represented in red)...

The gap between the windshield and the slider is uneven but I think that idea will work by using some self-adhesive foam tape that can compress where the gap is a bit tighter.

I have seen some folks tend to lift their canopies while sliding them forward & bashing their fiberglass fairings while closing & latching it, don't know, maybe just how they swing their arm forward I guess.
So I prefer a larger gap between the fairing & canopy, accomplished by stacking a few (4 or so) layers of duct tape on the canopy than applying a liberal amount of mould release before laying up roll bar fairing. I also make the fairing thicker/stronger to better resist damage from unknowing passengers who grab it while lifting themselves out of the seat.

Thanks, I will do this. I was concerned about water leaking in but it is probably going to leak anyway no matter how closely the lip fits to the slider.

 

[Ralph Inkster]

"Thanks, I will do this. I was concerned about water leaking in but it is probably going to leak anyway no matter how closely the lip fits to the slider.

I install a foam weatherstrip on the rollbar to seal the canopy joint, no leaks for the 4 sliders I built. & it actually reduces the noise level in flight too!

 

[Mark Curley]

Packing Tape

I used packing tape on the aft portion of canopy bridging the gap and just a little bit onto the front windscreen (maybe 1/16"). It kept any drips out of the gap. Of course it's a bugger to get the slider open the first time after the fiberglass strip sets up. I shook the slider from both sides and finnaly it came loose properly. A little sanding under the fiberglass strip to clean up debris and it looks fine.

 

[RyanWhite]

Aluminum tape and car wax

I used aluminum tape with a heavy application of car wax. I also ran ropes in from the aft part of the fuselage tied to the canopy to help pull it open. I also used a cake spreader (thin) to break the bond between the aluminum tape and the fiberglass. Go slow and be careful. This is a very critical part as you’ve outlined. I can’t stress enough to get everything taped up to prevent resin from going where you don’t want it to go.

 

[ian greenland]

Overhang

I used carbon fibre tape, it supports itself without needing plastic or cardboard strips,just tape over canopy to stop resin sticking,apply very light resin to tape and let set, then build with micro later

 

[PaulvS]

Update

This is a post-mortem update on what worked.

I used some self-adhesive closed cell foam tape 3mm thick stuck on around the back edge of the windscreen plexi in order to close the gap between the slider and the windscreen and then taped over this with clear tape. This prevented any epoxy resin from running through onto the rollbar. There was clear packaging tape applied over the slider and carnauba release wax.

After the epoxy was cured I was able to work a piece of thin hard plastic (cut up PET plastic juice jug) and get the canopy unstuck and free.

Thanks for the ideas!