Tip-up canopy glass gap

[Pmerems]

I am currently working on my tip-up canopy and fitting the Plexiglas. I have drilled the front and rear glass and doing some final trimming.

The plans call out a 1/32" gap between the front and rear glass, but I wanted a little more clearance then that. So I decided 1/16" gap would work well.

The canopy bow was clamped the roll frame per the instructions and I used the roll frame as my reference for my measurements. My roll frame is 1.5" +/-.005 in width (yes I made very accurate space blocks and clamped the frames very precisely when making the roll frame). Since the roll frame was very consistent in width, it makes a good reference for marking the canopy glass (both front and rear glass).

I used a dozen quick clamps to hold everything in position. However you can only clamp either the front or rear glass at a time not both. This is because you need access to the roll frame for the clamp to grip.

I carefully positioned the rear glass (after final trimming) so that front edge was was 1/32" aft of the center line of the roll frame. Then I drilled it in position. I then removed it.

I carefully positioned the front glass (after final trimming) so that aft edge was was 1/32" forward of the center line of the roll frame. Then I drilled it in position.

With the front glass in position I released the 8 quick clamps holding the canopy bow frame to the roll frame. As I released the clamps I notice the roll frame flex aft a little (about 1/16"). This was a little disturbing because I have the the roll frame and components aft clecoed in position (aft top skin was clecoed as well).

I reinstalled the rear glass and now have an 1/8" gap instead of the 1/16" gap I was striving for.

Rather disappointing.

What are the gaps other builders are achieving?

Paul

 

[az_gila]

Targa Strip

Paul.... no problem if you make a nice fibreglass Targa strip.

Mold it in place with saran wrap (or thin packing tape), then remove it, clean up the edges and just run the front portion mounting screws through it...

It needs to be thick enough to stand up to handling and occasional edge on hits...

I can show you how I did mine if you come over...

gil in Tucson

 

[rv72004]

I had a 1/16 gap or less on a cold day. When things get really hot the plexi expands and the gap gets smaller . In my case it touched so I had to enlarge the gap.
The gap you have could be a good thing in that you can now put a "P" rubber strip between the front and back glass . The P will push up between the gap and give a perfect seal. I will probably do this when it starts raining.

I have seen it done and must say it does look reak neat. The targa strip is also a solution for a good seal . If you like the looks of it.

 

[Pmerems]

Gap update

Gents,

I haven't completed the canopy installation but I have placed and removed the canopy glass several times while working on the side skins. In addition I removed all the roll frame/canopy bow spacer blocks and removed the clamps holding the canopy frame to the cockpit sill.

The gap has decreased to about .090". Every time I temporarily install the glass the gap changes slightly. The temperature in my shop has remained fairly consistent (~88 F)

So from the looks of things right now the gap is very close to where I hope it would be (~.060").

Until I rivet the canopy top skin on and side skins I won't know if things might change again.

Paul

 

[Pmerems]

Gap update! Gas springs----

I just installed the gas springs and expected the canopy to move a little forward (per other builders posts). With everything cleco'd together and the fuselage front top skin in position the glass gap increased to .170-.190" between the front and rear canopy. The gap between the canopy top skin and the fuselage top skin decreased to about .015" (from .045")n along the sides but the center remained the same about .045".

I am frustrated with the glass gap. I measured and cut for 1/16" and ended up with 3/16". The gap is straight and only varies about .015" in width. But is much wider then I wanted. It looks good just too wide.

Maybe as I rivet the canopy top skin in position the gap might decrease (wishful thinking). It isn't a show stopper just rather depressing.

BTW the gas spring forces the canopy frame outboard. It has increased the width of the canopy frame by about 1/16" at the forward gas spring attache point. I will be taking a bar clamp and prebending the frame so that once the canopy is fully assembled (with the gas springs) the canopy frame will be the correct width.

Any suggestions would be appreciated.

Paul

 

[TX7A]

Gap & Order of Attachment

I'm getting close to starting work on the canopy and have been trying to "study-up" before taking the leap.

In reading through this thread with the issue of the gap between the front & rear canopy pieces...

After the big cut, would it be practical / possible to do all the work on the front before the attachment holes for the rear piece were drilled? Seems like doing all the fitment, attaching the gas springs, etc. slightly changes the intended gap. By holding-off on the rear window attchment, it could be fit to match the front canopy once it was complete.

Would this work? ...

Thanks,
Sam

 

[Radomir]

Sam, yes -- that would be a preferred approach. There's so much dynamics in that whole front frame that you'd probably be best off finishing it completely before attacking the rear window. Once the front is completed, it won't move any more...

 

[zkvii]

Agreed it all moves around - everytime you get close the next step changes things a bit. We have cut and finished the rear window - so it can be installed, but have left the tip up section 'long' until the front skin is attached. Then we will sand the aft edge of the canopy down to the 'right' place.... Well that is the plan

Carl