What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Sliding canopy worries...

JurgenRoeland

Well Known Member
I trimmed most of what needed to be trimmed and I feel like I'm ready to make "the big cut".

The rear bow fits really nicely using all he clamps, the center rear of the plexy needed only little encouragment to fit on the rear part of the center bar.
The rest of the center bar butts nicely in the plexi bubble without using any force.
On the front bow, I used a long bolt to pull the canopy latch tube in 5/8 hole in the canopy.

When I look from the front, there are some serious gaps when I clamp the side bows. The images illustrate my problem. On the right side in the picture, I can almost halfway put my index finger underneath.

I tried moving the frame around but couldn't find get a better match without creating big gaps under the top center bow.

I assume that once the canopy is split, it will be more flexible to comply with the front bow when I clamp it in place then it is now.
I have drawn a 3/32 line for the division with the frame being in the current state.

What I'm worrying about is the movement of the sides when you pull it in on the top. will I still get 1/16 to 3/32 spacing if the whole thing moves, that is the big question.In other words, can I trust my current 3/32 split line .
Before making the cut I thought I'd ask for some opinions here.

Here are some images to illustrate:
http://jursairplanefactory.com/images/vansairforce/20201111_152620.jpg
http://jursairplanefactory.com/images/vansairforce/20201111_152611.jpg

thanks in advance

Jurgen
 
Same here

Hello Jurgen
I have the same problem here and I plan on stress relieving it like others locally have done to try and let The plastic relax on the frame once it is cut, This procedure came from the manufacturer of the plexiglass canopies down in Ohio, may be best to call Van’s and get their phone #
I have modified my finish kit box to become an oven to Slowly take the frame and trimmed canopy up to around 180* Fahrenheit and slowly bring it back down , this has worked for them and only needs a few nylon shims placed underneath the problem areas that remain ,
Good luck , Garry
 
Jurgen - This looks just like what I saw with my canopy, so I think you will be okay. If you have a good fit everywhere except along the front of the sliding canopy frame, it should lay down and conform to the frame shape after you make the big cut. I was surprised by how much it relaxed after separating the two halves. Good luck! The big cut is an exciting milestone in the project.
 
Fully agree with the above.
Feel free to visit my place in The Netherlands if you want to see my project.
I just glued to main canopy.
 
Also in agreement, once you cut the windshield off the main canopy conforms to the frame nicely.... I did all my work including the Sika bonding my basement shop at about 68-70 degrees, I did not "add" any heat. Check my Flickr page for my photos.
 
Is Flange On

It looks like you still might have the flange on around the outside. If so, I would suggest you cut that off and the try and refit. With the flange gone and the big cut done, my canopy had no trouble flexing to meet the bows.
 
It looks like you still might have the flange on around the outside. If so, I would suggest you cut that off and the try and refit. With the flange gone and the big cut done, my canopy had no trouble flexing to meet the bows.

I was hesitating to have the side trimmed down as it's not very clear how much you can go down to still have enough plexi left to the rear sides of the windscreen section. I wanted to go as low as the bottom of the side bows but not sure if that is not too low on the windscreen side.
 
Cut and trim

I was hesitating to have the side trimmed down as it's not very clear how much you can go down to still have enough plexi left to the rear sides of the windscreen section. I wanted to go as low as the bottom of the side bows but not sure if that is not too low on the windscreen side.

Not to sound condescending, but if the hole for the latch has been drilled, you're committed to the current position. Make the big cut and trim the sides per plan. It will be fine. The sides don't overlap the bow frame. If you do, the plexi will be wider than the fuse. There is a cutaway drawing showing the parts and location of the side edge of the plexi. It's accurate.
 
In addition

Also, you need to decide how the plexi attaches to the side bows. With sikaflex, you can either us a big bead, or the side bow attach metal pieces. This makes a difference on the side trimming position. I just used a large sikaex bead and my canopy is kissing the side bows. I thought i would have 1/4” clearance but when the sika was dry, that gap disappeared.
 
"The sides don't overlap the bow frame"

on the reply of Larry :
You mentioned a cutaway drawing, on which plan can I find this or is it somthing from the vans site ?
I understood the drawing on the plan for the side bows and how the plexi attaches there. I was more worried about the depth of cutting the front side where windshield is. I couldn't find a clear indication in the plans how low the plexi comes on the side curves of the front top fuselage skin.
The plexi has these three lines in which I assume are what they refer to as the molding marks. I guess I would be safe cutting until the bottom line of that (when the canopy is laying upside down)

on the reply of PilotJohnS :
I'm going the rivet way as in the plans.
 
Last edited:
side skin

If you look at the plans. the side skin that the front windscreen sits on comes up pretty far. I don't remember how much I cut off, but if the canopy was pretty centered when you drilled the hole for the latch, I would think there is plenty of material on the windscreen sides that one could cut off the molding flange without any worry.

On my windscreen, i cut off the radius on the windscreen that transitions from the horizontal part to the sloped windscreen. I fits the fuselage top skin and will need some additional trimming to fit well, but not too much. I would advise you do not get too aggressive cutting off the lower radius on the windscreen. in fact, it is probably best to just cut off the molding flange and not trim the windscreen anymore until the big cut and final windscreen positioning after canopy is riveted to canopy frame and side tracks and rollers installed. JMHO YMMV

By the way, sikaflex was easy. almost as easy as chalking a window. Wirejock did a nice writeup and yes it is that easy.
 
"The sides don't overlap the bow frame"

on the reply of Larry :
You mentioned a cutaway drawing, on which plan can I find this or is it somthing from the vans site ?
I understood the drawing on the plan for the side bows and how the plexi attaches there. I was more worried about the depth of cutting the front side where windshield is. I couldn't find a clear indication in the plans how low the plexi comes on the side curves of the front top fuselage skin.
The plexi has these three lines in which I assume are what they refer to as the molding marks. I guess I would be safe cutting until the bottom line of that (when the canopy is laying upside down)

on the reply of PilotJohnS :
I'm going the rivet way as in the plans.

Check out DWG-43, Sectuon F-F.
It shows the bottom edge of the canopy sandwiched between F-759 and C-660. If you bond it, just apply the adhesive to F-759 and use something flat to clamp the side.

Quite a bit is cut away to get the shape of the canopy to fit the fuse top forward skin. The molding lines are a good first cut along the bottom edge. After that, the big cut to separate the two. Then you work the canopy and there's plenty for the windshield later.
 
Check out DWG-43, Sectuon F-F.
It shows the bottom edge of the canopy sandwiched between F-759 and C-660.

that part in F-F I understood indeed and it's only after the big cut that you further trim back to get so close the top of the side bow.

My initial concern was by cutting the moulding part of I could go too high on the windscreen and having fitting problems later. But I understood from your and John's comments that cutting on the moulding lines in the plexi, we still have enough left for the windscreen.

I'll start by cutting the moulding away along the long ends and then see if I get more flexibility already on matching the front bow before I make the big cut.
 
Last edited:
I made the big cut and it came out very nice.

You can see below the before image and after image.

I hope it helps other builders who are before "the thousand dollar cut" and asked Vans also to add a line in the manual to indicate that the plexi really is able to flex a lot once it is cut.
I scatched my hair for weeks about this gap and was constantly worrying I did something wrong during the fitting of the frame in the canopy.
In the end I realize now that everybody probably goes through this.

beforecanopysplit-1.jpg


aftercanopysplit-2.jpg
 
Back
Top