Rear window flange width?

[TCONROY]

We are using the SikaFlex method of attaching our canopy and have had excellent results so far with the tip-up portion. We are now in process of fitting the rear window and I was able to rough it in under the F-774 top skin for the first time last night. Van's initially calls for a 1.25" flange width on the plexi (the width of plexi hiding under the top-skin). However, I don't see in the plans where a final dimension is called-out. It appears more plexi is removed when using the screws/rivets method since an aluminum backing strip is fabricated. What are others trimming the plexi down to? It seem the only issue would be ensuring the edge of the plexi isn't resting up against anything solid to prevent stresses in the future. The only area this could occur is the upper aft portion that would rest against the F-706 bulkhead. Suggestions?

 

[lorne green]

Trevor, I bonded the plex directly to the inside aft skin. Once my rear window was dry fitted into place I used a shapie to mark a guide line where the edge of the plexy meets the inside rear skin. Then, I drilled and dimpled holes about 3/8" of an inch from the plexy edge along that line every 3" or so. Not drilling in through the plexy, but outboard of the plexy. When I was ready to Sika bond the window, I secured the window to the inside window opening while the the Sika setup using 1" x 1" sqaure aluminum cuttings with cleakos. After a few days I removed the cleakos, filling the predimpled holes in the skins with two coats of Super-fil. I used an 1 1/2" of contact area - plexy to inside skin. My Sika lay up thickness was about 1/4 of an inch thick or less.
Good luck with yours.

 

[Taildrgr]

I just finished my canopy last week. It is not glued, just followed the standard Van's installation.
The final rear window flange width is 5/8" aft of the skin edge. The holes are drilled on a 5/16" edge distance.
The initial 1.25" dimension is just for fitting the window.

 

[bruceh]

I did the sikaflex bonding of the rear window and didn't use any screws or drill any holes. I did leave the flange wider than the plans call out, and it worked just fine. The flange does taper in under the roll bar brace and on the lower corners to the recommended 5/8" dimension. The wider flange gives you a larger surface area to glue, although I don't think it is needed. The Sikaflex sealant is amazingly strong.

I don't recall the dimension of the flange overlap, but it is at least an inch.

Lots of photos on my web site.

 

[TCONROY]

Thanks for the comments guys! Bruce, I actually have your photo library bookmarked and am going to use your idea of the plywood to keep pressure on the rear window when we Sika it in place. Thanks for that idea!

This morning I trimmed those forward ears to approx 5/8" to clear the roll bar bracket and determined there is no reason to trim the rest. Since we will have very little gap between the skin and plexi for SikaFlex, the more surface area the better. However, I don't want the top rear portion of the window resting against the baggage bulkhead, so I'm going to put a piece of 0.170 screen door spline as a cushion between the F-732F spacer and plexi. I think this will do two things: 1) Keep the plexi from butting up to the metal and possibly causing stress during thermal expansion. 2) Gives me something fairly solid to use a stop to hold the rear window against while gluing it.