canopy - how fragile really?

[prkaye]

Another canopy question. The main reason I'm not enjoying the canopy work is that I'm terrified every tiem i go out there to work. Terrified that it will break and cost me a fortune to replace. I've read all these warnings about how easily they can crack, so I feel like I'm working with an eggshell.
On the other hand, I tried to break a leftover piece that I had trimmed off, and it bent very far without breaking (was very hard to get it to break).
So, my question... how fragile is the canopy really? What's the biggest risk factor for cracking it?

[rv9av8tr]

Having recently finished my tipup canopy (and it cracking during construction), I have come to think of the canopy material like clear shipping tape. It can be strong as all get out, but nick it in the wrong way and it tears like toilet paper!

Like you, I could hardly break a trimmed off scrap by folding it in half! But I accidently drilled a couple holes with a standard #30 drill instead of a plexiglass drill.... and BOTH of those holes developed a 4" crack about 10 min after drilling!!!!

Keep the canopy over 80 deg F when drilling/cutting,
ONLY use plexiglass drill bits,
Jig capture the parts so they don't move around when cutting,
Sand all cut edges so a crack doesn't propagate,
Use a 100 Deg grinding stone after cutting countersinks,
Take your time!!

It's not a difficult task... just tedious.

You can see my canopy pics at: http://picasaweb.google.com/mikerv9a/Canopy

[prkaye]

yikes... what are you gonig to do about the cracks??

ONLY use plexiglass drill bits,

I've read this only applies when enlarging holes, taht a regular twist drill can be used for the initial #40 hole. Did your cracks happen by enlarging, or initial drilling?

[Mel]

I've built quite a few RV canopies and have never used a plexi-drill bit. Not to say they aren't great. Just that they are not necessary. Be very careful drilling plexiglas. Use high speed and virtually no pressure. I've not had a canopy crack. Mine has been flying for over 15 years. Of course now that I've said that, I will probably go out and find a crack.
RV canopies are not that fragile IF HANDLED CAREFULLY.

[JCN247DE]

Phil,

Before I started my Tip up canopy... I used to think that I would have to do the following things to be successful:

- Read to the canopy at night time.
- Rub it with a Plexus soaked diaper while singing old Barry White tunes to it.
- Make a blood offering to the canopy from my already air-drilled, aluminum mangled fingers.
- Work on it only in a clean room environment with the temp set to at least 121.5 degrees F.
- Threaten the canopy by saying that you'll have Captain Avgas and GMC jetpilot over to enforce their supreme intellect upon it if it does not cooperate.

I worked on my -7a canopy in the middle of an Ohio summer so I had that going for me.... Nice and toasty back in 2004.

During some die grinder trimming (you'll do a bunch of it...) ... I accidently knocked the entire canopy off of the saw horses with the air hose and it bounced! Bounced that sucker right off of the concrete floor of the garage. No chips, or cracks. It was like watching a car crash in slow motion as I could not get to the canopy fast enough to grab it! Should I have been more careful?... Yes! Did it happen anyway?.... Yes!

The scream that was released by me during the event is still hanging over Lake Erie somewhere to this day.

Having done this, I would not try to reproduce it as it takes a few years off of your life to witness. However, it did demonstrate how tough these things are as a complete structure.

My opinion of what would produce the dreaded crack? What's the most dangerous thing to do around the canopy to tempt fate? To me it is more of a local problem than the complete structure.

#1...using non-plexiglass drill bits to drill your holes. Get the required size plexi bits to do your drilling. I practiced on scrap pieces with both styles of bits. The plexi bit was more forgiving with an operator induced bad drill angle and forcing the bit through the material. The std bits chipped the edge of the holes and "grabbed" the plexi producing cracks around the test holes at times. Go slow here with plexi bits and back the plexi up with a wood drill block as you drill.

#2...forcing the canopy to conform to a canopy frame shape that doesn't look quite right.... then screwing it down in this pre-stressed condition. If you have monster gaps between the frame and plexi... take a minute to re-evaluate the fit and go slow with the trimming.

If the above doesn't work and you end up cracking it, take a big glob of Pro Seal and give yourself a "Dirty Sanchez" Mustache with it! I guarantee that nothing worse will happen to you and your canopy while in the shop.

Jeff -7A 440 hrs. of RV flying bliss...

[rv6ejguy]

Like Mel, never used plexi drills, never cracked mine and still no cracks after 5 years. Don't do plexi work in cold temperatures, use light pressure.

I was paranoid also when I started mine but it proved to be no problem. Time consuming and probably the worst job on the airplane but like all other jobs, it eventually gets done.

I would be careful enlarging holes as the drill can climb in too fast.

[prkaye]

For those initial holes they have to be match-drilled through the plexi and the canopy frame (right?). Do those plexiglass drill bits like going through steel??

[cjensen]

I did all kinds of testing on the pieces that were initially trimmed off to find out what I could and couldn't do. I drilled several different sized holes, with plexi bits, regular bits, and a unibit. I used light pressure, hard pressure, FORCEFULLY drilling it slowly, quickly, and everything in between. I couldn't get the dang thing to crack by doing any of that. I did get some light chipping with the countersink two flute cutter.

I tried several different ways to get it to crack without using drill bits or the like. A hammer would not crack it while hitting a piece on a carpeted table. However, put it on the cement floor, and it cracked after three blows in the same spot (the first two blows did nothing but scratch it).

To the extreme, I took a pair of snips to an finished and unfinished edges, and that snapped the plexi like plate glass.

Just my experiences...

[Steve A]

I approached my sliding canopy with a fair amount of respect. I did use the plexi drills as an added precaution. To me the varible is temperature. I built my canopy in an non air conditioned garage in south Louisiana. My canopy in the summer heat and humidity was a supple and pliable as a rubber mat. After I finished, I took left over pieces and dropped them on the concrete, bent them double, I tried to break them. Again in a cold temp, the plexi becomes very brittle.

Bottomline: get your shop as warm as possible. Work on the canopy when it is uncomfortable for you especially when you get those plexi crumbs down your shirt but the canopy loves it.

Steve Anderson
RV 7A H-6
Finished Waiting on Mike Stewart
Lafayette, La.

[Chappyd]

Yesterday I finished all the drilling of my canopy, including the windshield. I drilled all the initial holes with regular drills into both the plexi and the steel tubes beneath, no problems at all. To enlarge the exsisting holes I used reamers with straight flutes. Absolutely a piece of cake with no tendency to grab at all. I would never use a regular drill bit to enlarge the hole, I would screw it up for sure. I tried some practice pieces and everything going fine, then that bit would grab and screw itself into the hole faster than I could react. instant crack. Mel, you must have the "touch". I've had the canopy clecoed on and off making adjustments, and am suprised by how durable it appears to be. Good time of year for it