Cold weather canopy cutting

Reading other RV forums, it look like everyone is recommending 75-80 deg temps for cutting & drilling the canopy. Has anyone done any canopy work (sucessfully) at 60-65 deg-- the best I can do in the hangar right now. Looking ahead, I see lots of drilling but not much actual cutting. Am I missing something? It looks like it will be 3-4 months before I can get those kinds of temps. If the consensus is to wait for warmer weather, I'm thinking about hanging the engine, then doing the cowl/spinner work, and then the canopy/avionics.
I'd welcome input on that sequence if I can't go ahead with the canopy in a month.

Thanks

Wayne 120241

I am in the same situation as you. I can only get my Garage/Hangar up to 60 degrees. I really want to cut my canopy but know that the warmer the temps the less likelihood I will have cracks. I am trying to finish everything that I can except the canopy right now. Looks like I will have plenty to keep me busy till things warm a bit.

Halogen shop lights will heat that baby up in no time. Put a digital thermometer near it and make sure things don't get too warm too fast. I took mine from 60* to 95*F in < 1hr.

How about doing the work in a cheap camping tent with a small space heater? Or just make a 'tent' with a tarp...

Did anyone cut their canopy in with 60 degree temps? I created a "tent" with plastic and was able to improve the temps about 5 degrees. That's how I got mine to 60-65. Without the "tent" I am at around 55.

space heater

When I did this I aimed a small ceramic space heater to blow warm air under the canopy and this seemed to work fairly well.

If you like the lottery, go for it

The colder the acrylic the more likely it is to crack. When you try to heat with lamps and or heater you get uneaven heating.

Come on, you guys know the correct answer to this. Wait until it is nice and warm to work with it. Yes I know some of you will say you sucessfully did it at colder temps, but not all of you will suceed. Do you want to be one of the 5% or 10% that crack theirs?

You spent lots of $$$ on this project, do it right.

Gary Specketer
Dragonfly, Glasair III, Glastar, RV10
Tech Counselor, Flight Advisor

Ceramic heater worked for me.

You are right Gary! I will wait till August if necessary.

cutting versus drilling

from my experience the drilling is much more sensitive to colder temperature... as long as the pieces being cut with a grinding wheel are well supported the cutting itself is pretty low risk regardless of temperature. the initial cuts along the side to remove tooling marks are easy to support during the cut with duct tape, trimming slivers away during fitting is a non issue... the only cut that has any real potential for disaster is the 'big cut' from the large mass of each half... so long as each half is sufficiently supported so that they stay put during the cut there is little to fear.

drilling is another matter... test your drilling methods on scrap... try to introduce cracks and get a feel for what will cause cracks in drilling.

although i used a variety of methods i had the best results using a very dulled bit (on a scotch wheel) to bore/burn through the plexiglass for an initial pilot hole enlarged as needed with a step bit and counter sunk with a clean bit in a cage.

for the canopy work you can easily defer making holes... regardless of the temperature there is real risk in drilling that can be mitigated significantly from methods, technique, and experience.

I don't plan to do any drilling in my canopy. (SIKA). Any suggestions for air temp to make the "big" cut and trim cuts?

no magic temp...

if it is time in the build to do the canopy i would move forward. generally warmer is better but we are cutting with a grinding wheel that will rapidly heat the localized cutting area enough to melt the plexiglass and the real risk is not in the cutting itself but in introducing stress concentrations where they can propagate as a crack... this is most serious as the cut halves near independence and their mass is significantly leveraged at the shrinking connection between the pieces as the cutting is completed. if the pieces cannot move there is little risk of introducing a crack. after cutting, the edges should be dressed and polished a bit before handling to remove stress concentration points.

for the 'big cut' you can easily heat the canopy with a halogen light inside the bubble after you have it sufficiently secured for cutting.

the grinding wheels use a lot of air, unless you have a very large tank the cutting goes pretty slow with a lot of wait time for air pressure recovery...

i am not sure that there is a magic temperature but i would do whatever i could to get an overall air temp above 60, add a spot source under the bubble for the big cut, and concentrate on supporting the pieces during cutting.

RV-12

With the RV-12 tip up canopy, there is virtually no cutting. Edge trimming, a little here and there. Drill FIRST hole(s) with a slower-turning plasti-bit. ENLARGE ANY holes with a small SLOW-TURNING uni-bit. This will keep you away from most problems. Warm the area you are drilling in with lights as suggested, or other heat source. Go slow, it'll work ok.

John Bender

Canopy

I agree with Mr. Bender...no real cutting of the canopy...I was able to trim as required using a hand-held small sander, and drilled as required using the tapered reamers (not those metal remers) from StarLite Industries and did it all in an unheated hangar with temps around 25 degrees. No problem

Van's Answer

I am working on my canopy and asked this question to builder support, Gus I think. I live in the NW and due to a basement level garage I can open an access hole the house ducking and get warm air into the garage. This get the garage up to about 70 without making the house too warm. When I told Gus this he aid that would be just fine. He also said just be careful but the canopy is not an eggshell it can handle more than you are led to believe from the horror stories people tell. He also noted that after each cut dress the edges, he recommended a sanding block with 80 grit and the block should have a firm foam type backing that allow it the curve on the edges as you sand. The final dressing can be taken down to higher grits for a nice finish but the 80 grit is all that is needed between cuts as you fit the canopy.

I tried out the cutting wheel from fans on a drill and die cutter and both seem too slow, on due to my compressor (30gal). I then read about the roto tool and tried that with a metal cutting wheel and I must say it was the nicest to use, it also allowed a lot of control with the angle attachment and handle. I will be cutting this week so we will see.

Bottom line is if you are careful and keep a moderate temperature all should be well. I also plan to keep a space heater below the canopy for a few hours before cutting, when the garage is around 62 degrees which is normally where it sits the heater get the temp under the canopy to around 70 and the outside surface of the canopy is 68-80 depending on how from from the heat source, as measured with an inferred non contact gauge.

Happy cutting

Just to clarify...

The RV-12 canopy does not require any cutting / trimming during installation.
Nothing more than minor adjustments that can be done with a sanding block are required.

It does require drilling

"The RV-12 canopy does not require any cutting / trimming during installation. Nothing more than minor adjustments that can be done with a sanding block are required."

Click to expand...

The plans should make that clear. I cut the edges off that were too long. I assume that most other builders cut their canopy too. Did anyone find it unnecessary to cut the canopy? Although the plans do not actually say to cut the canopy, PAGE 34-05 Step 2: Says,

"Place the C-1201 Canopy over the WD-1219 Canopy Frame and position the canopy both fore/aft and side-to-side such that the dimensions shown in Figure 1, Section A-A, Section B-B, and Detail C are achieved."

Click to expand...

If the canopy exceeds those dimensions in every direction, then builders assume that the canopy needs to be cut smaller. Perhaps it would help to support the canopy in the center from below. I am not complaining, just trying to find out how I should have fitted the canopy without cutting it.
Joe

What I did

I just trimmed any spot that seemed a little tight. Did not cut a section off. Sanded the edges where needed, and that was about it. Hasn't cracked yet. I have been to max speed in 15 - 20 degree F weather, and it is still ok.

John Bender

Against all good advice

I cut my canopy in February last year in an my garage in the NW. I did have a space heater going, but it was still around 65F near the canopy. I agree with the other advice that cutting in cold environments is possible if done right - support the trim so that the weight of the cut pieces do not cause it to bend near the tip of the cut. When the cutter wheel goes through the canopy, you will feel hot plexigless chips hitting your hand, so at the point of cutting, the plexi is probably above 120F at least. A likely place for a crack to form is when the cut comes near the edge of the part and when stresses in the way the trim is supported, could cause it to crack.

Because of other build interruptions, I was back to final cuts on the windscreen and drilling my windscreen in January this year. This time the garage was between 55 F and 60 F - and recklessly started drilling with the 4-40 drill bits to go through the plexi and the roll bar. I upsized them with a tapered reamer drill, (http://www.vansairforce.com/community/showthread.php?t=48367&page=2&highlight=tapered+reamer+drill), and countersunk with a 3 flute countersink. No additional heating was used, and I have not yet had any problems.

Both the tapered drill reamer and the 3 flute countersink leave a smooth, nearly polished hole edge without additional rework.

This goes against the advice of many others with much more experience than I with plexiglass so consider that as well.

Just remember a new canopy is about $1,000. Two builders I know in our area have paid the price. I am not sure that temperature was related to their cracks, but if you don't have to take a chance, why do it?

Can you find other worthwhile stuff to do until the weather warms?

I cut a test piece off my canopy today. The garage temp was 52 F. I found that it was surprisingly brittle. There's no question that I will wait till I see at least 70F.

Hotter is better

IMHO cold is bad, I personally waited till summer (95 F in Ca). WIth all the bending a moving around cutting and drilling , it was much less stressful !
Peter RV6.2

Overkill

petercavallo said:

IMHO cold is bad, I personally waited till summer (95 F in Ca). WIth all the bending a moving around cutting and drilling , it was much less stressful !
Peter RV6.2

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I think waiting until the 90s is kind of overkill. I did my 8 canopy a couple of weeks ago. With a torpedo heater (30,000 BTU on sale at Ace) I was able to get the garage up to 78 degrees. This had me sweating. I turned it off and on as required to help maintain the temp closer to 72 which was perfect. I was careful but by no means did I baby the canopy, cut then sand smooth the edges before moving the canopy. I did all the moving alone, no help. Of course if you have other things you can get to without doing the canopy by all means wait until it warms up. For me, I did not want to get heavy into the wiring before I had the canopy done, so I had to get it done. Gus gave at Vans gave me good advice, 70 degrees is fine, it is not a piece of fine crystal, just be careful, smooth the edges and no side loads when you are moving it around.

At night I set the canopy on saw horses and kept a milk house heater on low, under the canopy with a bed sheet over the top. This kept the area at 68-70. I was worried due to all the hype about cracked canopies, the first thing I did in the morning was go look for cracks.

Heaters are gong on sale around here, Ace had the $135 heater on sale for $60, it will run for 14 hours on a 5 gal bottle of propane. I turned it on in the morning and ran it for an hour before going down to work.

rvbuilder2002 said:

The RV-12 canopy does not require any cutting / trimming during installation.
Nothing more than minor adjustments that can be done with a sanding block are required.

It does require drilling

Click to expand...

Maybe we can get the title of this thread changed or non-applicable messages moved.