Finding center on canopy

Just about to draw the center line down the middle of the tipup canopy. My question is are the black marker lines provided on the front and back of the canopy meant to show where the center line should be?? I have pictures but couldnt figure out how to send them.

It was probably overkill, but I used a laser:

http://www.rv7blog.com/2007/03/29/marked-canopy-centerline/

I marked the endpoints of the centerline, leveled the canopy as best I could, and shot my laser line from one to the other. By rotating the laser on my makeshift tripod and watching the reflections on the ceiling, I was able to get the plane of the projected line to be perpendicular to the top surface of the canopy. I drew a sharpie mark along that and had a perfectly straight centerline.

This measurement is pretty important for the slider canopy, since that's how you locate the center tube of the canopy frame. Accuracy here may be of less importance for the tip-up, I don't know for sure.

mcb

If I remember correctly I used the black marks plus a little eye-balling. Everything worked perfectly fine on the slider portion, but if I look really closely from the front of the plane, my windscreen is not perfectly symmetrical from left side to right side. No big deal deal but, as with any imperfection, it bothered me for a while. I have no idea how exactly to find the true center front to back, but Matt's approach seems to have worked for him.

The canopy's not as bad as its reputation, but you do just have to be patient and go slow. I'd highly recommend looking at Matt's website for the canopy. He has, by far IMHO, the best slider canopy website.

Good luck.

Finding center

Thanks guys for the feedback, Matt I was allready following some of your website items but failed to look recently at this question. I like the use of the laser, I did find center via sting and some eyeballing but its not to late to double check using a laser. By the way the black marks from the factory must be roughly in the center and ment to used for this purpose.

I used a laser

I bought one of those craftsman lasers for putting up pictures on the wall and such a while back. So when it came time to draw a line down my 8 canopy, I measured a few of places to find the center of my canopy along the top of the bubble, stuck the laser behind the plane and lined up the marks supplies by vans with the marks I made myself and had a perfect line which I drew by freehand. Was fast, easy and very accurate.

Randy
8A finishing, FWF

Using a laser does not help you find the centerline of the canopy. It my help you MARK a straight (planar) centerline, but even with the use of a laser there are an infinite number of planes which pass through the center points that are marked on the front and rear of the canopy. (Mine had no center marks, so I split the difference between the tooling "grip" marks on either side - but who knows if these are even).

Bottom line is that the centerline that you're marking is not really used, and if it's off probably 1/4 or 3/8 inch either way it doesn't matter.

Noah said:

Using a laser does not help you find the centerline of the canopy. It my help you MARK a straight (planar) centerline, but even with the use of a laser there are an infinite number of planes which pass through the center points that are marked on the front and rear of the canopy.

Click to expand...

Well, I agree with you up to a point... the laser definitely lets you mark a straight line easier than using a string. However, I found that I could also find the actual center of the canopy by watching the reflections from the laser off the canopy projected on the ceiling. Hard to describe but easy to do if you just turn out the lights in the garage and go for it. If the canopy is uniform (which you have to assume), the beam is passing through the measured center points at the leading and trailing edges of the bubble, and the plane projected from the laser is perpendicular to the canopy, you've pretty much found the true center line. Or close enough for our purposes.

There are plenty of ways to do this I'm sure, I just know this one worked well for me.

cheers,
mcb

Its nice to know

how much more you have taken off one side than the other. I will admit, I didn't use the centerline much, but it sure was nice to see if I was cutting off too much on one side or the other.

Randy

The canopy is NOT symmetric, but don't worry about it

An accurate center line of the raw canopy does not exist, because the canopy is measurably not quite symmetric, not quite uniform, by a significant amount. At least that's what I found with mine, so don't assume that yours is perfectly symmetric because it probably isn't.

Anyway, an accurate center line of the canopy is not really needed, at least not for the tip-up configuration. This initial "center line" is mostly just useful as an unmoving reference mark for the many iterations of trimming, but it does not determine the ultimate center line of the trimmed canopy.

I initially found the approximate center line essentially as Noah described. That's as good as anything (a laser line would be more straight, but that makes no difference here). But anyhow, ultimately I positioned and trimmed the canopy to find the best fit, which is what we really care about, regardless of this previously marked line.

If I had to do it again, I would forget about this center line exercise altogether. Just take the uncut canopy and place it roughly in position over the fuselage. Move it around to find the most symmetric best possible fit, and then mark your "center line" reference on the canopy to match the center line of the fuselage with the canopy in that position. That's still just a starting point, as you may want to shift things around a bit as you progressively trim the canopy to achieve the best fit. But as a starting point, that's probably more relevant and more useful than trying to measure the canopy's center line in isolation.

Tip-up centerline

I agree with the previous comment that the exact centerline is not that critical on the tip up. There will be some room to adjust if need be. If you are within 0.25 inch, you'll be OK. Once you mark it, be consistent. You can even drill a little hole near the leading edge to mark your midline, and put a rivet in it later to to hold your fiberglass fairing down to the windscreen.

I measured up from the tooling marks and found the mid-point and marked that.

By the way....use an air drill with your cut-off wheel instead of a die grinder to make your cuts and to trim your canopy down to near final size.

The air drill will give much better control, and much less vaporized plastic.

Dan Babenco
QB RV 7A
"Last 10%"