Sika canopy frame fitting considerations?

I know there are slightly larger measurements one must use when laying out the canopy bubble cut lines, if you're going to use Sika rather than the screws to attach to the frame. Is there anything related to fitting the canopy frame itself that I should consider, or would be beneficial?

I Sika'd my canopy and windscreen. The slider part fits very well, you just have to make sure you account for the gap you need for a nice layer of Sika. Sika recommends a 1/8" minimum between the plexi and the frame so you have to pull the frame bows in a little more to account for that.

The only thing I wish I had done a little better was to narrow up the front frame bow more so when it met the windscreen it fit a little better. As it is, my windscreen fits nicely to the fuselage side but my front frame bow on the slider was a little wider causing a little bit of a hump instead of a smooth transition. I bet I measured all of that a hundred times and I still didn't quite get it right. That would have happened even if I screwed it on so it really wasn't a Sika issue.

I used this guys pictures as a guide: http://picasaweb.google.com/n622wr/GluingMySliderCanopy# Thank you "RVTACH"!

Okay, I think I'm overthinking this, but always good to check. I'm following Bret's log (http://www.flightinnovations.com/canopy.html), and it seems as if my frame is following the same pattern. Mine's so far looking to be 3/4" high at the roll bar also, like his, with minimal adjustments needed along the side tube profiles to match the side skin / longeron curves.

First question is whether or not I account for 1/8" for the Sika at the roll bar height, considering the windscreen will also be Sika'd? So instead of the 3/16" height the plans call for, would it not be only 1/16" higher than the roll bar we're aiming for at the front canopy frame? Or not, again since the windscreen is Sika'd? This will determine how much of the bottom front tubes to cut down.

Next, measuring the ideal front frame bow width, we have the fuselage width - 1/2" per plans, then another 1/8" subtracted for the Sika. Got that.

The aft bow width, the plans are confusing. Is it fuselage width - 3/8" side skirt inset, and then another 1/4" subtracted for canopy spread? Or was the 1/4" part of the side skirt 3/8"? And then I get it, another 1/8" subtracted for the Sika fillet.

Finally, same idea, the rear height should be not 1/16-1/8" below the aft top skin, but rather 3/16-1/4" when adding in the 1/8" Sika fillet.

Is this all correct?

On Question #1, the roll bar height is a fixed height and the 1/8" Sika just adds to that. The front bow of the frame will have 1/8" added so it comes out in the wash. However, my advice is to not cut the tubes at the bottom of the front bow until AFTER you have glued on both the windscreen and the canopy. I had to add a spacer after getting the measurement wrong...lesson learned. I thought I was close and had erred on the high side but was wrong.

On your second comment. Yes, you have that right but I would err on the narrow side so you don't end up with the other lesson I learned the hard way. My bow spread a little more than I expected and ended up with it being a little too wide.

On the aft bow, the 1/4" is part of the 3/8", and then add the 1/8" each side for Sika. Seems like a scary big measurement, i.e., 5/8" all together but it will be easier to pull it out a bit then have to narrow it up. I got lucky on this one and it fit perfect.

Lastly, you have it correct on the rear bow height.

On the skirts, I used the metal side skirts and fiberglassed my own rear skirt. I fussed with the metal ones for hours and finally gave up. People can do it but I decided to do it in fiberglass and have a perfect fit.

Good luck!

Hi Bruce. Thanks! Actually I cut the front tubes this past weekend. Left them about 1/8" higher than the on-paper math calculates. Looks to be about right from an eyeball-the-tape-measure perspective though.

Everything else is coming out as you describe. I'm leaving things a bit narrower than calculated, mainly because I actually overbent last night. Leaning all of my 140lbs into it wasn't overcoming the springback, so I tried bouncing my weight into it. That actually worked a little too well. Now I'm bending the frame back out. So if it's narrower than calculated by about 1/8", as it currently is, all the better.

I'm definitely going to just glass the rear skirt. I might play with the metal one for an hour, just to see if anything comes to me. But too many other builders just glass it, so I'll take that as an omen of group-think wisdom.

Thanks!

Sounds good Scott, let us know how it goes!