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Before Gluing Canopy To Frame

WingRock

Member
I have trimmed my canopy to fit my frame and separated the windscreen and the rear of the canopy. I have also read all the threads on how to best make the canopy fit the frame, and still, It is approximately 1.25" out from the frame just ahead of the weldment. I will be gluing it on using 1/8" spacers as many of you have done. I am really hoping for a "crack free" canopy and just want opinions from those of you that have glued your canopy on and have had to pull the sides in and clamp it until the adhesive sets up.

Is 1.25" on each side (near the back.... where they all seem to crack) an excessive gap, or normal?
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Thanks for posting this Mark. I'll look forward to some of the others who may also reply.

I'm at the same point of my build, about to glue my RV8 canopy also. My canopy is pretty much the same as yours, seems like all parts of the canopy rest comfortably on the frame except the aft third. It requires a fair amount of pressure for me to get the plexiglass to conform and clamped onto the aft frame. However, I believe this is normal.

I have noticed, it helps to begin clamping aft and then move forward as you clamp.

Good luck, hoping others will chime in.

Regards,

Mike Perillo
RV8
 
Last edited:
Sika canopy to frame

I did my canopy a few months ago in the summer. I had a large gap too but it comes together nicely with clamps. I bought a whole bunch of spring clamps from Harbor Freight, the kind with the rubber tips. The rubber tips hold onto the frame on one side and the plexiglas on the other. One thing to watch out for is that once everything is glued and clamped the plexi canopy can shift to one side or other. It does it slowly if the clamps are not positioned squarely. Mine slipped around to one side by about a quarter to a half inch. I didn't realize what had happened until 24 hours later after the Sika has set up. Because I had not done a final trim, I had material to work with to even everything up, except at the very front on one side of the slider portion. The canopy slider front right edge did not transition to the fixed windscreen at that location so now I'm having to add micro to build up the edge of the windscreen. Good luck.
 
Thanks for posting this Mark. I'll look forward to some of the others who may also reply.

I'm at the same point of my build, about to glue my RV8 canopy also. My canopy is pretty much the same as yours, seems like all parts of the canopy rest comfortably on the frame except the aft third. It requires a fair amount of pressure for me to get the plexiglass to conform and clamped onto the aft frame. However, I believe this is normal.

I have noticed, it helps to begin clamping aft and then move forward as you clamp.

Good luck, hoping others will chime in.

Regards,

Mike Perillo
RV8

Mike,
Upon another experienced builders suggestion, I trimmed off (squared off) a few inches of the furthest aft part of the canopy (that will be hidden by the fiberglass skirt), hoping to make the rear section lay down easier but not sure as to how much it helped.
 
I did my canopy a few months ago in the summer. I had a large gap too but it comes together nicely with clamps. I bought a whole bunch of spring clamps from Harbor Freight, the kind with the rubber tips. The rubber tips hold onto the frame on one side and the plexiglas on the other. One thing to watch out for is that once everything is glued and clamped the plexi canopy can shift to one side or other. It does it slowly if the clamps are not positioned squarely. Mine slipped around to one side by about a quarter to a half inch. I didn't realize what had happened until 24 hours later after the Sika has set up. Because I had not done a final trim, I had material to work with to even everything up, except at the very front on one side of the slider portion. The canopy slider front right edge did not transition to the fixed windscreen at that location so now I'm having to add micro to build up the edge of the windscreen. Good luck.
Thanks for the info!
Glad to hear that it pulled in and held, reminds me that I need to go buy some more clamps.
You mentioned it slipped while it was clamped, did you clamp canopy to frame and pipe Sika in around spacers or lay a full bead and then place canopy on and clamp?
 
Frame Gap

My gap was about 1" in the back and took a fair amount of force to pull it down. I would recommend a thick Sika bond line in the back (~3/8"-1/2") transitioning to 1/8" or so as you go forward to minimize the pre-load. It will cost a little weight but think it's worth it.

Dave
RV-8A
 
Sika

I?ve sikaflexed all my canopies. As long as pressure is reasonable (and it will be at sides) your gap is fine. Sika flex is definitely hold it if applied correctly. I made a chin up bar with it years ago.

One thing I would recommend is a couple clecoes to prevent the canopy moving while drying as mentioned in another post. You can get away with 2-4 clecoes on entire canopy to hold it. Ensures perfect alignment. Put the clecoes near where you have a spacer so it doesn?t pull canopy in too close
 
I clamped up the canopy to frame and squeezed the SIKA into the gap, top-side first then the bottom-side of the gap. I taped both the frame and canopy on either side of the gap as others have done to make a nice finished edge of the SIKA. Lesson learned, don't wait until the SIKA cures before removing the tape. I did and had to trim away SIKA to get all the blue masking tape off.
 
What worked for me

You probably already know this, but here goes:

As you clamp the sizes, the top will try to go up. To not to honor your cut line as if it is a given. Keep readjusting the clamps until the canopy drops to contact the rollbar top and size, side rails, and back. When you do that, the pressure to squeeze it together is not very much at all.
 
My gap was about 1" in the back and took a fair amount of force to pull it down. I would recommend a thick Sika bond line in the back (~3/8"-1/2") transitioning to 1/8" or so as you go forward to minimize the pre-load. It will cost a little weight but think it's worth it.

Dave
RV-8A

Thanks Dave, I cut some more shims this afternoon to thicken up my transition and taper it back to 1/8".
 
I?ve sikaflexed all my canopies. As long as pressure is reasonable (and it will be at sides) your gap is fine. Sika flex is definitely hold it if applied correctly. I made a chin up bar with it years ago.

One thing I would recommend is a couple clecoes to prevent the canopy moving while drying as mentioned in another post. You can get away with 2-4 clecoes on entire canopy to hold it. Ensures perfect alignment. Put the clecoes near where you have a spacer so it doesn?t pull canopy in too close

Steve,
Thanks for the info. I will definitely use some clecos to prevent movement as I final trimmed my canopy to size already and can't afford movement.
 
You probably already know this, but here goes:

As you clamp the sizes, the top will try to go up. To not to honor your cut line as if it is a given. Keep readjusting the clamps until the canopy drops to contact the rollbar top and size, side rails, and back. When you do that, the pressure to squeeze it together is not very much at all.

Chuck,
Each time I clamp, I start with one at the top center of the frame to index the canopy to the same spot on the frame, then move to the back and clamp from the rear forward. I hope that this is achieving the same thing that you are describing, getting full contact all the way around to get down to the trim line.

Thanks for sharing your experience!
 
We had the same gap at the sides of our -8 canopy which we glued on.

Managed to do it without making holes or using clecos, just referenced centre marks at the very front and back (one clamp at the front), then clamped at the same side spots every time. The canopy settled to a natural position after that.

Also, we made a timber frame to hold the canopy while it was off the aircraft that matched the way the assembly fitted on the fuselage. The frame also had a solid back stop so the perspex ended up in the same fore/aft position each time.
 
Just a warning:
I SIKA'd my RV-8 canopy, and at about 50 hours TTAF it cracked at the base of the hoop around the back. It cracked at the weld where the two side bars come together and a single tube goes aft. This seems a common crack point, on RV-4s as well.
The crack was on the left side, so maybe the pull of the canopy latch, and a local stress riser, like a weld bump touching the plexi, or a flaw in the edge of the plexi?
The crack went straight up. I used Acrilifix, but did not remove the fiberglass skirt to glue the original point, so it cracked again, and longer, nearly to the top.
To keep flying, I used a cut-off wheel and cut the canopy straight across and down to the starboard side. I did this to prevent the crack growing forward or aft, and eliminate any built in stress.
Then I made a Targa strip, put it through a sheet metal slip-rolls for a perfect fit, and SIKA'd it on. I didn't invent this, I saw it on an RV-4.
I was going to get a Todd's canopy, but he passed on just about then...and the canopy repair has kinda grown on me...
The take away here is to know about this common crack point and try to reduce the likelihood of it happening to you. :eek:
Or, failing that, to know of acceptable repairs.
 
Just a warning:
I SIKA'd my RV-8 canopy, and at about 50 hours TTAF it cracked at the base of the hoop around the back. It cracked at the weld where the two side bars come together and a single tube goes aft. This seems a common crack point, on RV-4s as well.
The crack was on the left side, so maybe the pull of the canopy latch, and a local stress riser, like a weld bump touching the plexi, or a flaw in the edge of the plexi?
The crack went straight up. I used Acrilifix, but did not remove the fiberglass skirt to glue the original point, so it cracked again, and longer, nearly to the top.
To keep flying, I used a cut-off wheel and cut the canopy straight across and down to the starboard side. I did this to prevent the crack growing forward or aft, and eliminate any built in stress.
Then I made a Targa strip, put it through a sheet metal slip-rolls for a perfect fit, and SIKA'd it on. I didn't invent this, I saw it on an RV-4.
I was going to get a Todd's canopy, but he passed on just about then...and the canopy repair has kinda grown on me...
The take away here is to know about this common crack point and try to reduce the likelihood of it happening to you. :eek:
Or, failing that, to know of acceptable repairs.

Scott, did you use spacers to allow for gap between frame and plexi?
 
Thanks for chiming in Ed and Scott. A very mysterious part of the build for me. Were it not for this great forum, doing something like gluing on a canopy would be a lot of trial and error.
 
Spacers/crack?

Just a warning:
I SIKA'd my RV-8 canopy, and at about 50 hours TTAF it cracked at the base of the hoop around the back. It cracked at the weld where the two side bars come together and a single tube goes aft. This seems a common crack point, on RV-4s as well.
The crack was on the left side, so maybe the pull of the canopy latch, and a local stress riser, like a weld bump touching the plexi, or a flaw in the edge of the plexi?
The crack went straight up. I used Acrilifix, but did not remove the fiberglass skirt to glue the original point, so it cracked again, and longer, nearly to the top.
To keep flying, I used a cut-off wheel and cut the canopy straight across and down to the starboard side. I did this to prevent the crack growing forward or aft, and eliminate any built in stress.
Then I made a Targa strip, put it through a sheet metal slip-rolls for a perfect fit, and SIKA'd it on. I didn't invent this, I saw it on an RV-4.
I was going to get a Todd's canopy, but he passed on just about then...and the canopy repair has kinda grown on me...
The take away here is to know about this common crack point and try to reduce the likelihood of it happening to you. :eek:
Or, failing that, to know of acceptable repairs.

Scott, hoping you might share more info regarding the crack you experienced in your RV8 canopy......, wondering if you incorporated ?spacers? when gluing your canopy?

It would be helpful if you can share with us the size and type of spacers used?
Specifically for the RV8 canopy frame, the aft area of the no rivet weldment, maintaining a gap (approx. 1/8?) between the plexiglass and the frame would seem to help reduce the stress and the likehood of cracking. I?m curious to know if you used spacers and still wound up with a crack?

Thanks, Mike P
 
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