Cracked Canopy Club - one more...

Cracked Canopy Club - UPDATE

Tonight I cracked my F'ing canopy, while attempting (obviously unsuccessfully) to drill the canopy lock handle hole. I think I had a combination of marginal temperature (75F in the hangar) and a less-than-perfectly supported canopy that caused the crack, but in any case it's toast.

So my question for the other cracked canopy club members is this - a replacement from Vans, or from Todd's, or from someone else? What seems to be the best option?

On the plus side - since the canopy was already obviously toast, I grabbed a towel and wrapped my right hand and gave it a **** hard punch to see if I could break it in the case of a tipover. It broke quite easily. I might need a bunch of stitches in the case of a tipover, but I feel fairly certain I could get out. True, I was able to pick a good stance and a good punch - but adrenaline and the will to survive will go a long way too.

So - the question remains - best option for a replacement canopy with shipping to west Texas?

I'm gonna get good and drunk and sit on the couch and pout for a while.

Unless something changed, Todd was doing only tandem canopies.. no side-by-side..

On my 12, it came with the canopy lock handle hole already drilled. Saved me from joining the club!

don't waste that knowledge!

..sorry to hear about the crack, that hurts in more ways than one.

Please enlighten us on a couple things. How old was the canopy?
what kind of drill bit and technique were you using? Drill type and speed? could you hear it squeaking? Use any lube?
okay, you get the idea.

..oh, and if there's enough left, try a few tools to bust the canopy...always 'interesting'.
thanks

flyboy1963 said:

..sorry to hear about the crack, that hurts in more ways than one.

Please enlighten us on a couple things. How old was the canopy?
what kind of drill bit and technique were you using? Drill type and speed? could you hear it squeaking? Use any lube?
okay, you get the idea.

..oh, and if there's enough left, try a few tools to bust the canopy...always 'interesting'.
thanks

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He did say the temp was marginal at 75 degrees. I'd heat it, to at least 90+. Then these canopies can take quite a bit of abuse. My canopy was around 12 years old, before drilling. I used all kinds of drill bits in the scrap, and they still didn't crack. Temps were in the mid 90's.

L.Adamson

I walked away from the mess with some big chunks left, disgusted. I'll save them for tests later. Nothing bigger than about a foot square, I was pretty **** mad and kicked the everloving **** out of what was left.

Temp in hangar roughly 75F, slow speed drill with Unibit just as the directions call for, BoeLube on the unibit, light pressure, received from Van's about 6 months ago. I had the canopy upside down on a padded table as recommended but only had marginal support around the edges. I think the canopy may have been under stress from trying to "flatten out" and stretch under gravity pull. Next time I'll flip it rightside up and drill it under compression rather than tension.

Still pouting. Proceeding to get drunk, and will continue to pout. Please let me me know where I screwed up.

You could have used a die grinder or dremel with a stone instead of the bit. Try it on your scraps. Of course, it might make you feel worse.

Hey, you're taking it like a man! Throw a tantrum and get plowed, it's what I would do!

Right Side Up

airguy said:

. . . . . . . . . . Temp in hangar roughly 75F, slow speed drill with Unibit just as the directions call for, BoeLube on the unibit, light pressure, received from Van's about 6 months ago. I had the canopy upside down on a padded table as recommended but only had marginal support around the edges. I think the canopy may have been under stress from trying to "flatten out" and stretch under gravity pull. Next time I'll flip it rightside up and drill it under compression rather than tension. . . . . . . . . . . .

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I just did all my canopy cutting/drilling in the last week or so. Temps always 75-78F. I had "stops" set up on the table where the canopy sat to keep it from "spreading" when sitting upright. I drilled the canopy lock hole from the outside (upright position) using a unibit in my air drill, no lube of any kind. No problems. I suspect your analysis of the problem is correct. I think the key is to keep the stress off the canopy - particularly in the area you are cutting/drilling it.

Sorry about that, I know it has to be tough!

Consider this....

airguy said:

......I think the canopy may have been under stress from trying to "flatten out" and stretch under gravity pull.....Please let me me know where I screwed up.

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Dan Langhout said:

.....I think the key is to keep the stress off the canopy - particularly in the area you are cutting/drilling it.....

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You are not the first builder that has happened to and I suspect drilling operations or ambient temperature had little to do with it. The same thing happened to a friend of mine when he attempted the big split on his poorly supported canopy. As the cut proceeded along.....KEEERAK! It's all about stresses generated on the highly flexible Plexiglas. There are any number of ways builders use to support or immobilize the canopy while working it. My own technique was to tie twine between the two sides. When the windshield and main canopy sections finally separated, the natural tendency to flatten out was completely eliminated and nothing but the width of the kerf separated the two main pieces. Food for thought.

So sorry your canopy cracked. I guess that's what Jack Daniels is for. I used packaging tape across the bottom of my canopy to hold its shape while making the big cut with good results. I think I had 4 strips spaced out down the sides. This was a slider on a side by side canopy. I also sat a small ceramic heater under the canopy to warm it up. I was scared to death the whole time but everything worked out OK.

rv9aviator said:

I guess that's what Jack Daniels is for.

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Crown Royal in my case, and it served it's mission well last night.

Today it's time to man up and order another canopy. The shipping is going to hurt. I guess I can use the time until it shows up to run some wiring and work on lights and tip fairings.

Oh well - if it was easy they would let anybody do it.

Rick6a said:

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I like this idea - I was going along on the instructions and trimmed the excess from the edges, but I think on round two I'm going to leave that excess and use your method with the twine - it makes sense from a stress relief point of view and I won't be left with the holes since they'll be trimmed off anyway. I'm going to Sika the canopy to the frame, so the only hole I need to make is for the canopy handle. The rest will be just careful cutting. I tried a vibrating saw as well as the die grinder with a cutoff disk for cutting the plexi, I think I prefer the die grinder. It's easier for me to control and the vibrating saw had a tendency to just melt the plexi and push it around the bit and didn't make a clean cut.

Tell me more about the dremel and stone idea for cutting the hole? I have not seen that referenced before.

Greg,

I think Vans get their canopies from Airplane Plastics in Ohio. Todd doesn't make a canopy for the side-by-side models like someone else has mentioned although he does make them for Cozy's.

When I cut my canopy I used a die grinder and did the unibit thing on the handle hole. The temps were in the upper 80's and low 90's when I cut mine. I used the drill bits for the plexi on all my holes. When I cut my canopy I taped the sides together to keep it tighter but I like Rick's method better. Wish I had thought of that at the time.

If I was gonna cut another canopy now I would use a Fein MultiMaster or a better quality equivalent. You may have better control with it than a die grinder. I know the canard builders love them for trimming fiberglass. I was afraid the whole time cutting mine using the die grinder. I just tried to make light cuts over and over until I penetrated through.

Sorry your having a tough time. I hate do-overs.

Rick6a said:

My own technique was to tie twine between the two sides. When the windshield and main canopy sections finally separated, the natural tendency to flatten out was completely eliminated and nothing but the width of the kerf separated the two main pieces. Food for thought.

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I did a very low-tech version of this. I can't remember where I got it from - might've been Checkoway. But I pulled duct tape from one side to the other , pretty much where you show the lines... to keep it from changing shape and exerting any forces that might ruin my day.

I treated that darn thing like it was nitro -- I still do. I think every time I made a cut, no matter how small, I polished the edge down to 800 grit, even if I were going to cut it some more. Ridiculous overkill, but that's how scared I was of this sort of event happening, for which I have nothing but sympathy.

the 'best' technique???

well Greg, sounds like you did everything right, and it still bit you!
I'm not saying higher temps aren't a good thing, but I'll bet a majority are cut at MUCH lower temps than 75.
My only comment; drilling holes in the 'waste' skirt sounds like asking for trouble; clamps or the duct tape method would allow me to sleep at nite!
a big plug, covered with felt, inside the dome I think would go a long ways to offering support, rather than just limiting the tendency to 'squat' when pushed on.
Hey, the truth is; people have used almost every method imaginable, and either gotten away with it, or not. Not much comfort, but either is the Crown Royal ( when it wears off!)

Greg,
I've only cut 3 canopies in half and I think I did them all on the airplane. I have done a couple dozen windshields on spam cans up through turbines. You must have some cheapo mounted stones that came with your die grinder or dremel. Pink or gray, ball shape or cone shape. Stick one in your tool and try some holes on your scrap. You'll find that you can grind a certain amount without melting depending on tool speed and stone coarseness. A bit of melting is okay too, but it needs to be cleaned off afterwards. No big deal. A lot of the rag bags have trim strips with screws that go right through the plexi. You generally want them oversize so differential expansion/contraction doesn't load the screw against the sides of the holes. I've used a tiny stone to drill/melt these many times and it works slick. You just have to clean up the melting flash. You always need to smooth/polish all your edges and holes to at least 400 grit anyway. I've never had a stone grab and make a crack. I have cracked lots of plexi with bits though. I will say I've never cracked with a real plexi bit, but sometimes I still need to chase the hole wider with a stone anyway. Melting your way through can induce radial cracks if you build up a temp differential between your hole & the surrounding sheet. Just do it in stages and don't melt your way through a thick sheet in one pass. I've done $20k windshields on King Airs & such where the holes still don't line up (Wichita skilled labor). Those type windows always have oversize holes that are filled with proseal or sometimes little silicone or neoprene sleeves over the screws, then proseal. You can do amazing stuff with acrylic sheet sometimes. Then sometimes it'll crack. Like Rick Parry says....oops.

Fearless said:

Greg,

I think Vans get their canopies from Airplane Plastics in Ohio. Todd doesn't make a canopy for the side-by-side models like someone else has mentioned although he does make them for Cozy's.

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I talked to Daryl at Van's this morning, he's going to have them drop-ship a canopy to me. The canopy itself is $1115, shipping is yet to be determined. Expensive mistake.

When I broke mine a couple of years ago, I put the word out to the local RV community. I had a replacement the next day, from a guy near me who wasn't as far along as I was. When my replacement showed up, I sent it straight to him.

Something to think about, if you want to keep moving.

Lars said:

When I broke mine a couple of years ago, I put the word out to the local RV community. I had a replacement the next day, from a guy near me who wasn't as far along as I was. When my replacement showed up, I sent it straight to him.

Something to think about, if you want to keep moving.

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I thought of that, but the new one will be here right after Thanksgiving and I've got more than enough other work on the airplane to keep me busy until then. I'm ready to mount the wheels on the gear, I still need to do all the fiberglass tips, and I've got lights and a battery box to install as well as rear top skins to rivet on.

When I got the fuselage to the point of being able to work on the canopy, it felt like I was really getting close - but then I started really thinking about all the systems and components that still have to go in, and it really started to sink in just how much work there still is to get done. I had to force myself not to freak out about the rest of the task still in front of me, and just do one thing at a time. One day I'll run out of things to do, and on that day I'll fly.

airguy said:

I thought of that, but the new one will be here right after Thanksgiving and I've got more than enough other work on the airplane to keep me busy until then. I'm ready to mount the wheels on the gear, I still need to do all the fiberglass tips, and I've got lights and a battery box to install as well as rear top skins to rivet on.

When I got the fuselage to the point of being able to work on the canopy, it felt like I was really getting close - but then I started really thinking about all the systems and components that still have to go in, and it really started to sink in just how much work there still is to get done. I had to force myself not to freak out about the rest of the task still in front of me, and just do one thing at a time. One day I'll run out of things to do, and on that day I'll fly.

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You are perhaps more practical than I was. Getting a new canopy the next day and getting on with it (I used Sika as well, and can now say that I've done 2 canopies myself) was therapeutic. The first time, it took me 3 months to get through agonizing over the Big Cut, getting the canopy frame straight, figuring out the Sika process, etc. Second time around I wrapped it up in a week. Learning curve, and all that.

Good luck, perhaps there's some solace in knowing you aren't alone

Canopy cracks/ locktite

Also, keep locktite away from your canopy!

I had installed my 7a canopy and was pleased with myself for dodging the pitfalls. I thought using locktite on the roll bar screws would be a good idea....just a tiny drop. Weeks later I went into the garage and peeled back the protective plastic to see almost every hole starred out. Cracks radiating out from the holes. First I thought it was lack of clearance around the screws but I had followed the directions. Turned out the locktite caused it.
The rear canopy piece was $ 500 I recollect. And a bunch more work. Never fit quite as well as the first one.

Use Vibra-Tite on the screws instead of Locktite - this works at least as well without the danger of crazing the plastic.

Ok, so tonight I decided to do some basic research on real-world effects of drilling/enlarging holes in the plexiglass. Since I seem to suddenly be in possession of some decent-sized chunks of real canopy that are otherwise trash, I want to put them to good use. All this work below was done this evening in 56F temperature.

I started with the piece seen below, chosen to have a little curvature...


I initially drilled with just a unibit, using almost no pressure, holding both pieces by hand with no backing. I first punched a hole with a 1/4" plexi bit, then enlarged some of them with the unibit. The 1/4" bit did some minor chip/cracking, but the unibit very nicely took that out during enlarging of the hole. The one 1/4" hole where I put very light pressure (maybe half a pound) cracked noticeably.


After doing that, and noticing how nicely the holes turned out even in cold temperatures when using little or no bit pressure, I decided to run a few more. On another piece of roughly the same curvature I ran 3 sets of 6 holes. The set on the right was using a 1/4" plexi bit with about 1/2 pound of pressure on the bit and 5 of the 6 were chipped/cracked. The center set was the same bit with only barely enough pressure to keep the bit in contact with the plexi, took maybe 45-seconds to a minute to make each hole. All 6 were good. The left hand set were drilled with the same pressure as the center set but using a standard twist drill, all 6 were chipped/cracked.


On the last hole drilled I decided to drill it with the 1/4" plexi bit, using about the same pressure as I would use on a piece of aircraft skin, which was just about enough to barely visibly flex the plexi. It broke completely in less than 3 turns of the bit.


Based on this I think the stress on the plexi and the force of the bit applied to the plexi are larger factors than the temperature of the plexi. I drilled and enlarged maybe 100 other holes other than these, and I feel relatively certain I can successfully drill the canopy latch hole now, even in cooler temperatures.

Since I still have a lot of canopy material left - I'm casting the net out to the sea of other builders - what tests/experiments would you like to see done on the plexi to answer some questions? Sealants? Crazing chemicals? Cleaning agents? Paints? Fuel?

airguy said:

and I feel relatively certain I can successfully drill the canopy latch hole now, even in cooler temperatures.

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Forget the cooler temps. Warm it up, and I don't care what others say. It's easier and safer to work with, when warm.

L.Adamson

L.Adamson said:

Forget the cooler temps. Warm it up, and I don't care what others say. It's easier and safer to work with, when warm.

L.Adamson

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Agreed - and I'll certainly play it safe and warm up the second canopy - but I'm trying to figure out for others what works and what doesn't. We don't always get to have all the factors going our way, it's good to know what is relatively workable and what is a minefield.

Testing, testing 1,2,3.

airguy said:

....noticing how nicely the holes turned out even in cold temperatures when using little or no bit pressure, I decided to run a few more.....I think the stress on the plexi and the force of the bit applied to the plexi are larger factors than the temperature of the plexi.....

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I agree with your observation that the importance of temperature tends to be overstated. In fact I reported the same thing in a post where I felt confident enough to drill and countersink the series of holes through the windshield and rollbar of the slider canopy on my -6A in an unheated hangar amid an ambient temperature of 65° and as expected, the experience proved entirely successful.

http://www.vansairforce.com/community/showthread.php?t=47568&highlight=flute+bit

Some of us are more comfortable working with Plexiglas than others are simply because of past experience. I don't mean to downplay the importance of temperature and I certainly do not recommend others attempt to try what I did but the builder should be aware that other factors are at as least equally important as temperature and your casual testing tends to confirm that.

To my mind, it is far more important to use the right tools coupled with proper technique. For instance, why anyone would use a standard drill bit that has been intentionally dulled to drill through Plexiglas when dedicated bits specifically designed to be used on Plexiglas are available is beyond me. In addition, never run a standard twist drill though an existing hole in Plexiglas yet people do that all the time. That is just begging for trouble. Also, proper technique demands that solid support to avoid stressing the Plexiglas while machining it is vital as you now well know. In addition, lots and lots of canopies have been cracked because the builder used a piloted countersink bit and inadvertantly applied an unintentional side load on the countersink is yet another common and needless cause of cracks.

As far as your testing goes, try this. Drill a row of #30 holes with minimum edge distance through a piece of Plexiglas. Take a standard #30 countersink bit like Van's recommends in the builders manual and run it through those holes to produce countersinks. For testing purposes and to simulate a builder briefly losing control while countersinking, INTENTIONALLY place a side load on that piloted countersink bit and see what happens.

Greg,

I started reading this post and I really feel for ya, man. I cracked my canopy on August 4th. It's one of the biggest blunders of the whole project so far, but it's my own fault. My stupid mistake created a crack about 12" long right in front of what would have been the passengers face, on my tipup canopy for my RV-7A. Here's the ugly result:



Several weeks later, when I could write about it without getting sick to my stomach all over again, I documented my mistakes as best as I could. Anyone interested can read about it here:

August 4th Log Engry

I have since pressed on and I'm back in business, but it was a huge setback for me. It was all I could do to refrain from smashing it all to bits and drowning in a bottle, but I'm glad I did. We're having our monthly Chapter 105 meeting here at my shop in January, and we're going to test one of the canopy-cracker tools, to see how well it works! I plan on taking pictures and some video footage to share with the community. At least my stupid blunder can result in some good for everyone, and that helps lessen the pain.

I preparation, I laid a strip of fiberglass down on both sides of the plexi right over the crack to strengthen it. I want to know how well this tool really works, and a cracked canopy isn't a fair place to start, so this makes the crack stronger than the original plexi. Anyway, it should be very interesting.

I'm reading your posts about your experiments with great interest, and I applaud you for taking the time to post these things for everyone to learn from.

airguy said:

I talked to Daryl at Van's this morning, he's going to have them drop-ship a canopy to me. The canopy itself is $1115, shipping is yet to be determined. Expensive mistake.

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It is freight, see if you can give them a business address. It knocks off a big chunk (Pun intended).

I am a member of the busted canopy club. It was drop shipped from Ohio to South Alabama and shipped to a business. ~$150 two years ago. Call Airplane Plastics to arrange shipping and delivery.

AltonD said:

It is freight, see if you can give them a business address. It knocks off a big chunk (Pun intended).

I am a member of the busted canopy club. It was drop shipped from Ohio to South Alabama and shipped to a business. ~$150 two years ago. Call Airplane Plastics to arrange shipping and delivery.

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Already did that, they will deliver by truck to the local freight terminal and I'll pick it up directly. My office is just a few miles away from the terminal, works out nicely.

Support exit side of plexy!

Hello

I had damaged my landing light plexy, because I was not supporting the pexy on the exit side of the hole. 3 hole where fine, there I placed a strip of hard wood or plexy. Then on the other side I didnt support it and as the drill goes out of the material, it pulled it in! Damaged hole, part is still usable but I learned my lesson.

Also I was drilling a flat piece of plexy, supported it with a piece of hard wood, all was fine on the first hole, then on a second hole, the drill get pulled in and the hole cracked to the edge .... stupid me, I was replacing the wood exactly where I drilled allready the first hole. So as the drill bit came out od the plexy, there was for 1/8" no support (backpressure), tis was the cause the drill gets pulled in and push away material instead of cutting it.

Still have to drill my canopy soon.

Regards, Dominik

Good write up

BSwayze said:

Several weeks later, when I could write about it without getting sick to my stomach all over again, I documented my mistakes as best as I could. Anyone interested can read about it here:

August 4th Log Engry

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Thanks for taking the time to write this up.

Just FYI for everyone reading this thread..

I just got a new canopy shipped from Airplane Plastics (took advantage of my cracked canopy to get a slightly darker tint) and it cost $170 to ship from OH to Denver. I'll be picking it up from their freight terminal, so I imagine home/airport delivery would add another $150 to that price.