Is there anybody that's getting ready for the "big cut" on a tipper canopy?

[instructor_bill]

I'd like to know if anybody either just completed the "big cut" or is going to.

My reasoning... I decided to rivet the forward rear skin so I could paint the fusellage on a rotisserie. Having done so, I will be unable to get the canopy to rest on the bulkheads and mark the cut line against the cabin frame.

I knew this would be an issue, but wanted to forge ahead anyhow.


I've not yet ordered the finishing kit and won't have my canopy for a while, but what I wanted was some basic measurements. Every canopy is different, I get that, but every prepunched fuse is darn close to identical (humor me.)

Has anybody got a measurment of the length of the forward and aft pieces of canopy along the centerline? If not, I can fudge it.

I figure if I start a tad long and trim to fit, it won't be much different than if I had a canopy that rested roughly on the bulkhead cabin frame and forward skin when I marked the cut line.

 

[BSwayze]

Bill,
I'm getting ready to start cutting my canopy in the next few weeks. I don't have my forward rear fuse skin riveted on yet like you do, but I'm not sure I see how that makes much difference. The skin is only, what, .032" thick? Most builders I've seen have placed the canopy down on top of that skin for fitting and trimming purposes. As long as the clecos are out of the way, it's probably the way to go, isn't it?

 

[instructor_bill]

it's not the skin thickness I was concerned about.

I thought that the canopy might lay better if the skin wasn't keeping it from naturally laying on top of the 706 bulkhead and slightly below the final skin surface. Then again, I suppose everything aft of the f-706 bulkhead like the j stiffeners and f-787 would possibly be in the way of the canopy taking an unobstructed rest on the 706 bulkhead as well.

Maybe I'm looking at it the wrong way and there's no reason to make it a big deal

 

[RViter]

It's like an RV-6A, too.

I thought that the canopy might lay better if the skin wasn't keeping it from naturally laying on top of the 706 bulkhead and slightly below the final skin surface. Then again, I suppose everything aft of the f-706 bulkhead like the j stiffeners and f-787 would possibly be in the way of the canopy taking an unobstructed rest on the 706 bulkhead as well.

Maybe I'm looking at it the wrong way and there's no reason to make it a big deal

At the risk of mixing apples and oranges, I'll offer a few pix of the RV-6A QB Tip-Up canopy cutting;
http://www.mykitlog.com/users/display_log.php?user=garyc&project=757&category=5424&log=97748&row=10

Relatively little change in the design, and therefore the process of cutting the plexi. (The fwd top skin, F-675?, on the RV-6A is not pre-punched or trimmed so I actually adjusted the skin edge after the plexi.)

When you get the canopy, you'll see that the mold edges are still on the plexi, and that alone is a big trim. Once that is eliminated, you can 'start' moving the canopy into position and approximate the front & back edges. It's an iterative process. I don't think I cut more than 1" off any edge initially, and the cuts got progressively smaller. You'll know when you're in the range when the aft end slips INTO the rear window area.

The whole canopy was/is a big task, but the initial fitting and cutting (for me) was less traumatic than advertised. USE THE CUTTING wheel and materials Vans supplies. Stay 'warm' and get help lifting and moving the plexi.

I also used the cut-off wheel to dress the edges after each cut, and even scraped it with the back of a hacksaw blade as it got to the final. Just to lessen the stress crack potential. Put some extra layers of tape, (blue or your favorite) along the cutting line to avoid the inevitable 'slip'.

gary (rviter)
RV-6A QB, O-360-J2A->???
www.mykitlog.com/garyc
Mesa AZ

 

[jdeas]

Plex lip

I had my skins on before making the cut. As the lip around the edge of the canopy keeps it from conforming I saw no reason to not do so.
I trimmed the front and sides a little at a time. Once they were rough set I marked and made the big cut. In my case there was plenty of material for the back. Using a plastic putty knife I edged the back under the skins several times until the final edge cuts were made bringing the big cuts back in line.
Just be careful to note that the canopy cut will tilt slightly on the roll bar when you get the edges under the back skin. (same with the front and sides but to a lesser degree.)