While on vehicle, not to worry.
I have a black-gold Bell Wildfire and wouldn’t worry about sun damage while car-topping it on a multi-week trip in warm climates, as I have done many times.
Storing it outside in the sun all year would be a different story.
Sunlight (the UV component, I think) will oxidize the gel coat on composite boats whatever the gel coat color, including the clear gel coat over a carbon-Kevlar layup. The oxidation will show up as a milky white, powdery coloration. This oxidation can be removed by abrasive polishing, which will gradually remove all the gel coat if repeated several times, or covered up chemically with Penetrol.
I don’t think the carbon fiber fabric itself will be damaged by heat, given that carbon is the residue of burning, but over the long term the ensaturated resin may become brittle or weaker.
I wouldn’t waste money on canoe bags for car-topping unless I had money to waste. Even then, I wouldn’t want the hassle. I do believe composite canoes should be stored inside to minimize gel coat oxidation.
You’re not making sense.
The time course of internal heating in my carbon paddle will be quite different in the two cases. In the first case, the paddle is in a hot car interior, and gains heat therefrom.
In the second case, the paddle blade gains heat from the hot interior, but it also, catastrophically, gains heat from the sunlight pouring onto and into its surface.
I avoided engineering courses at MIT, but I got A’s or B’s over 5 grueling semesters of calculus. Later, working with Georgia Tech engineering students on rehab medicine problems, I learned how totally naive they could be.
What didn’t make sense?
You don't need to explain to me what you meant. I already told you I understood what you meant.
What did I say about the relationship of heat and temperature that did not make sense to you? I gave you an example to illustrate why "ambient heat" is nonsensical terminology, and you find that confusing?
I think the ambient temperature inside a
car sitting in the sun makes adequate sense.
Incidentally, your analysis regarding the strength of a flat versus a curved blade turned out not to cover the ground. Close, I grant you, but no ceegar.
If you don’t want to get into these discussions, go write something long and lacking in paragraph structure.
Ambient temperature - yes
That makes sense, and from that figure you can immediately know what the temperature of the paddle will be in the absence of sunshine. Quantifying ambient heat in some way, even if you could do it, wouldn't tell you a thing about the resulting temperature of your paddle (that's assuming, you set aside and forget about the temperature measurement that you used when determining the amount of heat).
Is that clear enough?
Oh, and I'd be interested in your explanation of how something that is stressed in cantilever fashion can be made stronger just by making it curved, especially since you make it slightly longer in the process, providing more material to be stressed within the same original working length, and thereby increasing the total amount of flex (for example of this principle, would a wrench be stronger if the handle were not straight?)
And by the way, your curved paddle blade would definitely be stronger if curved in two directions, as that would provide a thicker "working beam" (like making a larger but thinner beam out of the same quantity of steel). Did you neglect to mention that before?
OK
Yes, I'm familiar with the difference between conductive and radiant heat transfer. If you meant that your black paddle gets hotter when it's in the sun, I think that's obvious, but I didn't get that from what you wrote. As far as the air heating the paddle, there is likely convective heat transfer as well.
If you're saying your paddle swells up because it gets hotter when it's in the sun, that doesn't really make sense to me. I don't know if a paddle is made with material that has a high enough coefficient of thermal expansion to cause that. That's why I mentioned possible water vapor contamination during the build. But I don't know that's the case, of course.
As far as engineering students being naive, I guess that's true. Med and law students are naive as well. Then they grow up, do real, professional work and gain some wisdom. Anyway, I am not an engineering student.
Ambient heat and UV rays are…
two different things.
Jack L
Yes I know
I found the statements unclear, so I missed his point.
“pours” in, does it?
And is your paddle made of the same material profile as a Bell Northstar canoe? Or do you think all marine materials are same/same?
Who's naive, again?
Well…
…I’m not a scientist and I’m no “Expert” on sun rays, heat, and the like. All I can vouch for is practical experience with a couple black boats.Having OWNED and cartopped blackgold and carbon boats over the years, they’ve spent days on the roof in 90-100 degree heat without problem. I guess a “Bag” would be nice, but I can’t imagine stuffing my boat into an oversized condom every time I used it? Maybe if you paddle a couple times a year? Not practical for me!
thermal degradation of fiberglass and pl
astics…
I took a brief online journey into the subject finding that YES, and NO but if you are rushed or a slob you may ignore a non existent problem.
The gelcoat dulls or turns milky white from clear from UV and maybe thermal degradation…heat for the argument.
Composites and on a molecular level with plastics are of different materials inside…‘like’ concrete and steel rods as an analogy. So cyclical applications of thermal degradation stress the insides at different rates of expansion/contraction/and of course chemical degradation…where the first compounding linking everything together as theorized on paper begins chemically disassociating.
Does this 'matter…make a difference…rot the hull ?
Well, we have seen rotten hulls ? So… ?
From experience, I’d go with 303…after repair !!!
For more than a month in severe UV lands for my priceless Bell…Seattle Fabrics sells a flag cloth and hardware for duplicating the common bow n stern strapped cover…maybe wrapped in spiraled shock cord…would spiral shock cord spiral a Bell hull when heated ?
Huh?
Is my brain misfiring and am I having a TIA? This makes no sense to me?
subject ?
In reply, you’re condition requires a ‘subject’ as ‘this makes no sense.’
What is meant by ‘this.’ ?
Guessing at ‘this’, composites and on a molecular level, plastics are structures composed of material with different expansion and contraction rates…like reinforced concrete.
Rates and basic degradation increase with for example, every 10 degrees rise in temperature.
As we know from past sun failures, some compounds fail others survive but all degrade thermally from square one.
Question is can the owner of a new Bell afford a cover ? ‘This’ question may or not be thermally related.
Bag Lady
will be happy to accommodate you.
You’re is a contraction of the word you are. You seem to mean the possessive “your”…
So please no critique of grammar.
typo ?
‘this’ no subject is dysfunctional trollerism. Itsnot grammar, it’s inadequate.
Interesting
Well this thread certainly spawned some interesting side discussions. I’ll be picking up my new to me boat en-route and heading out west without any worries thanks to you fine folks. After that it will be spending its life indoors between field trips to the river.
My concern came from wondering how hot a black boat would get sitting in the sun on a 100 degree day (mostly worried about burning my hands undloading) and then remembering that the way to remove handles from Zav paddles was the heat them up and then they just twist right out. Perhaps a different resin used for that very reason but enough to make me ask…and I’m glad I did.
Alan
I have a black carbon fiber
bicycle and have been riding it for years with no problems.
Wilhelm Wien; Nobel; vehicle color
Wilhelm Wien won the Nobel Prize in 1911 in large part for his theory of black body radiation. There are no historical reports on how many melted canoes he had.
Vehicle color can be crucial. If you have a white vehicle, the killer sun rays will be reflected up inside your boat, thereby almost doubling the amount of ultraviolet and infrared waves bombarding your black canoe.
On the other hand, it’s arguable that it’s best to have a black vehicle with black vinyl seats, so you can scorch yourself in the car before you even have to touch the boat. Sort of like swinging three bats before you step up to the plate.