Super cold and canopy

[AN23]

We're going down to 7 degrees f tonight. I don't know if my RV-8 canopy has ever seen that low of a temp. (Built in Texas, lived in Oklahoma and now SC). I'm thinking of putting an incandescent work light in a steel milk bucket in the backseat after taking the seat cushions out. Next, I'll place a blanket over the canopy. What do you think? Trying to just give it a little warmth. Good idea or bad idea.

I just don't want to come out next week to find a big crack!

 

[MacCool]

If you're going to fly it, at some point you have to unplug it and expose the canopy to ambient temps and temp changes, along with airframe flexing stresses. My 10 year old RV-9A was built in Atlanta, then lived in St. Louis for awhile. Now it lives in Minnesota and is exposed (in the hangar) to 0°F winter temps routinely, and as low as -30°F several days out of the year. Daily temp swings of 40° or more are not uncommon. I worried about cracking for awhile but finally came to the conclusion that there wasn't anything I could do about that. Might be more of an issue as the plexiglass ages, but so far, no cracks.

 

[lr172]

We're going down to 7 degrees f tonight. I don't know if my RV-8 canopy has ever seen that low of a temp. (Built in Texas, lived in Oklahoma and now SC). I'm thinking of putting an incandescent work light in a steel milk bucket in the backseat after taking the seat cushions out. Next, I'll place a blanket over the canopy. What do you think? Trying to just give it a little warmth. Good idea or bad idea.

I just don't want to come out next week to find a big crack!

Boy do I wish it would be 7 tonight Mine has seen much colder than that with no damage. It really depends how tightly it is put together, but experience tells me that if it is done right it can handle really cold temps. We had wind chills of 35 below, so with that kind of wind, I don't believe a 100 watt lamp would make any difference at all.

 

[Dan 57]

Good idea or bad idea

Probably neither nor... the canopy on RV-8s are probably more prone to cracks than other models.

I'm no specialist, but think cracks happen for different possible reasons. One can be a rapid change in temperature, such as can happen airborne when flying thru an inversion. Another can be expansion or contraction creating stress on whatever mean of holding the canopy was used, screw, rivet, or glue. Yet another obvious one is shock. Or torsion, which will probably happen in flight.

Now warming up the interior of the canopy whilst having the outside going cold does not seem a very good idea to me...

 

[riseric]

-20C / -4F

FWIW, my personal cold temperature record is -20C / -4F last winter.
This summer, I flew to above 30C / 86F.
With that temperature spread, no cracks then and since.

 

[Kyle Boatright]

We're going down to 7 degrees f tonight. I don't know if my RV-8 canopy has ever seen that low of a temp. (Built in Texas, lived in Oklahoma and now SC). I'm thinking of putting an incandescent work light in a steel milk bucket in the backseat after taking the seat cushions out. Next, I'll place a blanket over the canopy. What do you think? Trying to just give it a little warmth. Good idea or bad idea.

I just don't want to come out next week to find a big crack!

I don't think your idea will cause harm, and I can understand how it could help - by reducing the differential expansion between the 3 materials used on the canopy (plexi, fiberglass, and steel).

If this is a concern for you, go for it.

 

[Roadjunkie1]

Canopy and temperature changes....

We're going down to 7 degrees f tonight. I don't know if my RV-8 canopy has ever seen that low of a temp. (Built in Texas, lived in Oklahoma and now SC). I'm thinking of putting an incandescent work light in a steel milk bucket in the backseat after taking the seat cushions out. Next, I'll place a blanket over the canopy. What do you think? Trying to just give it a little warmth. Good idea or bad idea. I just don't want to come out next week to find a big crack!

Disclaimer: my experience is only with SuzieQ which is an RV-4. I am not familiar with how the -8 is mounted to the canopy system. When I made mine (a tilt-over) I left room in the drilled plexiglass holes to allow for expansion/contraction of the glass itself and, likely, the differences in the expansive properties of the canopy frame. I built my canopy to very tight tolerances for a good, water-tight fit and it has served that purpose well.

I have been in temperatures hot enough on the ground (Jefferson, Iowa) I couldn't get the canopy closed (again: a well-fitting canopy!) and had to 'borrow' the shade of a hangar to sit in and cool it down. I have flown in -10F degree weather and hangared her in 20F degree (for instance right NOW) and have never had problems.

My concern with heating the cockpit would be the unequal expansion of the different materials in your canopy. I would guess the plexiglass of the canopy would expand before the metal around it and that would be what you wouldn't want. I would think letting everything that makes up your canopy would be better served if it all was subjected to the same temperature changes. But, again, I am not familiar with how the -8 is built. Hopefully those that fly -8s will chime in with how they deal with Summer/Winter changes..... IMHO; again I am only familiar with my particular -4 and can only vouch for that.

 

[AN23]

Thanks for all of the ideas/input. In the end, it was a fruitless effort as I forgot you can no longer purchase incandescent bulbs! I'm certain it will be fine.

 

[Kyle Boatright]

Thanks for all of the ideas/input. In the end, it was a fruitless effort as I forgot you can no longer purchase incandescent bulbs! I'm certain it will be fine.

Probably too late for you now, but these might be something to consider in the future. You can find them in different wattages.

https://www.amazon.com/Simple-Delux...locphy=9010953&hvtargid=pla-626637556755&th=1

 

[alpinelakespilot2000]

I would not take a canopy that is warm (either because it is in a heated hangar or because you are heating it up with a light bulb) immediately into super cold OAT's. It's the rapid expansion or contraction that's going to do damage to the canopy. If it has time to slowly acclimate I think you are better off.
Not a physicist though, so take my opinion (based on 12 RV years in an environment with significant temperature differentials and no cracks in my canopy) FWIW.

 

[Mile High Relic]

Thanks for all of the ideas/input. In the end, it was a fruitless effort as I forgot you can no longer purchase incandescent bulbs! I'm certain it will be fine.

You can still get "rough service" incandescent bulbs on amazon. I only see 100W and smaller though.

 

[Roadjunkie1]

What? No stinking bulbs....??

Thanks for all of the ideas/input. In the end, it was a fruitless effort as I forgot you can no longer purchase incandescent bulbs! I'm certain it will be fine.

Sometimes fate intervenes..... I'm pretty sure you will be fine as well. This would be a hot topic if it was a common problem...

Merry Christmas/Happy Holidays and now you don't have to worry....

 

[Kyle Boatright]

You can still get "rough service" incandescent bulbs on amazon. I only see 100W and smaller though.

You can also buy ceramic heating elements like this. They come in several wattages and screw right into a bulb socket. Even better, if you're interested in heat output, they don't convert energy to visible light. Just heat.

https://www.amazon.com/Simple-Delux...ocphy=9010953&hvtargid=pla-626637556755&psc=1

 

[JonJay]

You can also buy ceramic heating elements like this. They come in several wattages and screw right into a bulb socket. Even better, if you're interested in heat output, they don't convert energy to visible light. Just heat.

https://www.amazon.com/Simple-Delux...ocphy=9010953&hvtargid=pla-626637556755&psc=1

Very cool, errrr hot!
Truth of the matter , incandescent bulbs are so inefficient at producing light, they are not much less efficient at producing heat than an IR element. That’s why they are going the way of the Dodo. A 100w incandescent produces the same heat as a 100w IR lamp, it’s just slightly less efficient at doing so.

Back on topic - 20 years ago or so, the canopy cracking issue was a hot topic. People did all kinds of things to prevent cracking, mostly during construction. Warming the hangar, heating the canopy itself with space heater, holding one’s breath…. Voodoo dolls and sacrificing to the canopy gods….
I took some canopy pieces and put then in the freezer. I drilled them with split points, whacked them with hammers, etc…. I could not induce a crack. Yet, some poor soul goes out to his hangar one day and for no reason, they have a crack that suddenly appears. Even the relatively new approach of gluing them with no drilling, and some crack.

I don’t think there is anything one can do post build.

 

[Wing nut]

Watch for rapid temperature changes

We're going down to 7 degrees f tonight. I don't know if my RV-8 canopy has ever seen that low of a temp. (Built in Texas, lived in Oklahoma and now SC). I'm thinking of putting an incandescent work light in a steel milk bucket in the backseat after taking the seat cushions out. Next, I'll place a blanket over the canopy. What do you think? Trying to just give it a little warmth. Good idea or bad idea.

I just don't want to come out next week to find a big crack!

A few years back I was flying my 8 from FL back to MN in early January. I had a 4 hour stop over in Omaha where I asked for a plug in for the Reiff heater being the temp was around “0”. They said “we can just put you in the hangar”. Well sure I say and in the maintenance hangar I went. They roll me out later for departure and off I went. When I got home I had a 4” crack at the rear of the canopy. I’m convinced it was from the thermo shock coming out of the heated hangar. I’ve flown through 11 winters now in temps as low as -10F and that’s the only time I’ve ever had an issue. I’d say avoid a rapid heat up or cool down and you should be fine.

 

[lr172]

I would not take a canopy that is warm (either because it is in a heated hangar or because you are heating it up with a light bulb) immediately into super cold OAT's. It's the rapid expansion or contraction that's going to do damage to the canopy. If it has time to slowly acclimate I think you are better off.
Not a physicist though, so take my opinion (based on 12 RV years in an environment with significant temperature differentials and no cracks in my canopy) FWIW.

While I can't confirm it, I believe there is a lot of truth to this. The canopy acrylic is directly exposed to the cold air and the metal structure it is attached to is not. Therefore, it stands to reason that the acrylic is going to get colder faster and therefore shrink faster than the material it is attached to. You are already dealing with the challenge of different rates of expansion, so cooling one faster than the other just adds to the challenge.

If the ambients are dropping a couple of degrees per hour, no big deal. But if it goes from 60 to 10 in a matter of seconds, like when exiting a heated hanger, this certainly seems to be a situation where the acrylic will cool MUCH faster due to it's direct exposure. Wind will accelerate the cooling of the acrylic.

Larry