Van's Air Force
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Whew! Made the big cut!
- Thread starter bret
- Start date
lorne green
Well Known Member
You know the two tabs on the front of a tip up canopy frame - left and right? DON't push agressively against the tab with the plexi in between
just to get it to lay flatter (with sika). I ended up with a small crack ... stop drilled. Not a huge issue but next time, I won't push as hard.
Others have had a lot worse problems.
Oh ya, after cutting the canopy with an air zip tool and then sanding the edge with say...100 grit sanding paper,
don't agressively move, flex, bounce your canopy until completely sanded smooth. I checked out the canopy edge with what amounts to a jewelers loop only to discover
minute checks or fine, fine cracks within the edge of the canopy. Don't be a flexin' the loose canopy!!
just to get it to lay flatter (with sika). I ended up with a small crack ... stop drilled. Not a huge issue but next time, I won't push as hard.
Others have had a lot worse problems.
Oh ya, after cutting the canopy with an air zip tool and then sanding the edge with say...100 grit sanding paper,
don't agressively move, flex, bounce your canopy until completely sanded smooth. I checked out the canopy edge with what amounts to a jewelers loop only to discover
minute checks or fine, fine cracks within the edge of the canopy. Don't be a flexin' the loose canopy!!
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Cracks
Cracks often start as the drill bit breaks through the far side of the plexi. It's hard to control the pressure as the bit reaches this point, but going very slowly certainly helps. Practice a lot on scrap to get a feel for things. It's a good idea to initially drill the holes undersize. It's harder to control larger bits, and they can do more damage. Special plexi bits are very helpful. One good trick after drilling the initial undersize hole is to countersink the back (drill exit) side to a diameter just slightly larger than your final hole. This makes it very difficult to cause an exit crack. Freehand single flute countersinks come highly recommended for this, although I actually slightly prefer six flute countersinks. Again, practice, practice, practice!
Cracks often start as the drill bit breaks through the far side of the plexi. It's hard to control the pressure as the bit reaches this point, but going very slowly certainly helps. Practice a lot on scrap to get a feel for things. It's a good idea to initially drill the holes undersize. It's harder to control larger bits, and they can do more damage. Special plexi bits are very helpful. One good trick after drilling the initial undersize hole is to countersink the back (drill exit) side to a diameter just slightly larger than your final hole. This makes it very difficult to cause an exit crack. Freehand single flute countersinks come highly recommended for this, although I actually slightly prefer six flute countersinks. Again, practice, practice, practice!
RV3bpilot
Well Known Member
Temper control while working on Canopy
Keep your work area hot when you work on your canopy. I would pre-heat my canopy using a large refrigerator box and a space heater,"great way to catch things on fire so keep an eye on it". I let the canopy soak up heat for about one hour then I would move it to the work table also about 80 degrees. I had no problem cutting or drilling but I did use bits that were designed just for cutting plexiglass and I sanded the edges before test fitting.
Keep your work area hot when you work on your canopy. I would pre-heat my canopy using a large refrigerator box and a space heater,"great way to catch things on fire so keep an eye on it". I let the canopy soak up heat for about one hour then I would move it to the work table also about 80 degrees. I had no problem cutting or drilling but I did use bits that were designed just for cutting plexiglass and I sanded the edges before test fitting.
I used #40 normal twist drill bits to drill initial holes in both canopies I have done. On these I was always drilling through the plexi and into the steel tube immediately underneath. I never had any problems with drilling this way - the trick was to make sure there was no gap between the plexi and the steel tube AND that the plexi was warm (80-90 degrees). I enlarged the holes later - never attempt to enlarge a hole in the plexi with a regular twist drill. This is very likely to cause a crack. A Unibit works great for this purpose!
Plexiglass bits work great but are useless for drilling through anything - such as the steel canopy support tubes - on the other side of the plexi. In fact I found that if the plexi was up against the steel tubing the Plexi bit would not completely drill through the plastic.
I managed to crack a scrap piece of Plexi by enlarging a hole using a Plexi bit. So while these bits are much less likely to cause a crack - be careful, it's still possible.
Plexiglass bits work great but are useless for drilling through anything - such as the steel canopy support tubes - on the other side of the plexi. In fact I found that if the plexi was up against the steel tubing the Plexi bit would not completely drill through the plastic.
I managed to crack a scrap piece of Plexi by enlarging a hole using a Plexi bit. So while these bits are much less likely to cause a crack - be careful, it's still possible.
RV7Guy
Well Known Member
Nice Work
Good job. The big cut is kind of a non event once done.
On my first 7, tip up, I got a crack on the last hole I drilled. I should have changed bits and didn't.
The new 7 is a slider and I'll be using Sika. I have not heard of crack using Sika. There is a lot of work to get it ready but when done, done it is done. I think the Sika finished canopy looks great.
Good luck, keep everyone posted.
Good job. The big cut is kind of a non event once done.
On my first 7, tip up, I got a crack on the last hole I drilled. I should have changed bits and didn't.
The new 7 is a slider and I'll be using Sika. I have not heard of crack using Sika. There is a lot of work to get it ready but when done, done it is done. I think the Sika finished canopy looks great.
Good luck, keep everyone posted.
bret
Well Known Member
Ok , I'll up date my build site on mon or tue, so, today was an awesome day to cut up the canopy, 90 Deg in the garage! I don't want to curse my self, i want to be humble, I'm sure I had help from above today, did all the frame to canopy heights set up and did all the trimming, no issues. This was a lot easier than I thought, all the whore stories of cracking this expensive piece of plastic, it is just plastic right? Why so expensive? Can't wait to get past this nerve racking stage in the build.
Sounds like you've got a handle on it now, but the key here is to NOT put any kind of bending stress on the plexi until you've sanded the edges smooth enough to not catch the fibers on a cotton ball.
OK - maybe a slight exaggeration - but not much.
Seriously, don't do a blooming thing, don't touch it, don't breathe on it - until you've sanded and smoothed the edges. If you can catch a fingernail in it, it's too big. If it's cooler than 75 degrees, walk away and pray for sunshine tomorrow.
OK - maybe a slight exaggeration - but not much.
Seriously, don't do a blooming thing, don't touch it, don't breathe on it - until you've sanded and smoothed the edges. If you can catch a fingernail in it, it's too big. If it's cooler than 75 degrees, walk away and pray for sunshine tomorrow.
lorne green
Well Known Member
And don't sand your canopy by hand...that's way too much work. Use
an air driven RA (random orbit) sander. ez-pz.
an air driven RA (random orbit) sander. ez-pz.
bret
Well Known Member
Spent hrs sanding the edges smooth, my first pass was with a belt sander, and yes, I was very carefull not to move it until it was sanded. And it was 90 deg yesterday. So far so good, but it looks like I will need to retrim the lower edges of the windshield, the front settled after trimming the front contour?
lorne green
Well Known Member
Big cut, sand, trim, sand, trim, sand...now you've got it!!
lorne green
Well Known Member
Brett, I see you are building a slider but using sika instead of rivets can net a nice smooth skirt. No paint on my unfinished tipper yet, but this will give you an idea of the potential outcome.
https://plus.google.com/photos/1068...5829407058686260226&oid=106834625031269905364
https://plus.google.com/photos/1068...5829407058686260226&oid=106834625031269905364
Smilin' Jack
Well Known Member
Amen to what Robbie said... I too had little electric heaters blowing up both sides of the canopy, plus it was already 80 here in Georgia.
Jack
Jack
