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Old 02-02-2010, 01:04 AM   #111 (permalink)
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Thumbs down Ironing Shrinkwrap = Bad Idea.

Hey Fubeca, I've finally gotten around to testing the heatshrink methods for tomorrows wrap up on my cap.

If anyone here has heard me mention using an iron to shrink the plastic, I now officially un-mention it. Bad idea, reason being, when the plastic finally gets hot enough to shrink, it is very sticky. Sticky and conductive heating do not mix. Must think touch free convection. Didn't wreck the iron, but the result was horrible, think crinkled aluminum foil finish.....hey, maybe the crinkles will act like little "vortex generators"... and when all those little vortex combine....wait ..waaaiiiiiit...

I might not need to buy this after all!!





I bet the big oil companies will pay me millions of dollars to just shut-up and go away....Never mention the crinklewrap AGAIN.

So tomorrow I'm off to get a heat gun. I was able to make a small propane torch do the trick but it was a pain to use and I need a heat gun anyhow.

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Old 02-02-2010, 10:32 AM   #112 (permalink)
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Yeah - I didn't think of that. The stickiness is nice for heat welding the plastic to itself. I had to put some pleats in mine at the front and back, and I had to stick a small piece on to cover the hole that burned through
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Old 02-02-2010, 11:18 AM   #113 (permalink)
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Thanks for mentioning that, I was wondering in my mind how to deal with the front corners as far as possibly being pleated. It would really make it easier to throw 2 pleats in the front, as opposed to leaving it baggy when I staple it up and then trying to shrink the top to fit.
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Old 02-02-2010, 11:32 AM   #114 (permalink)
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Watching this youtube video on boat shrink wrapping helped me figure it out.



The staples act as the perimeter band to keep it down, but the rest is basically the same concept.

I tied the two sides together with a board across the bottom inside because the plastic tends to compress the whole structure as it shrinks and I didn't want it to distort the frame. I don't know how much force it can put on the structure, but I wanted to be safe.
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Old 02-15-2010, 11:17 AM   #115 (permalink)
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Update:

I'm not sure this black plastic, shrunk with a heat gun is going to be a good medium-term solution when there are large temperature variations.

The weather has been pretty cold since I initially built the cover and the plastic remained tight and looked pretty good.

Last week we got some more warmth and the heat from the sun the plastic started to expand and wrinkle. I'm now pretty concerned about what it will look like after things really heat up.

I wonder if it was shrunk using the heat guns used for boats if it would have worked better as it would be a more uniform shrink.

However, this is not likely to be a great method for any type of long-term use.

I think I'm headed back to the drawing room to figure out version 2.0. I'm also considering doing some testing to determine how much difference there is between a snugtop style topper, a tonneau, and this topper for this particular truck. I may end up going a different route if there is not a significant difference.

On a positive note - I did just get my second highest tank ever at 19.04 MPG for a whole tank. I'm definitely excited to see what happens when things really warm up

Last edited by Fubeca; 02-15-2010 at 11:22 AM..
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Old 02-15-2010, 11:44 AM   #116 (permalink)
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The plastic shrink/stretch problem is an issue for people who make canvas boat tops too. One fitted in hot weather will be taut all year, but one made in the cold will be loose in the summer.

Congrats on the 2nd best tank MPG. 19.04 MPG is 9% higher than your "lifetime" cumulative MPG, which is all winter I see.
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Old 02-15-2010, 11:51 AM   #117 (permalink)
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Yeah - I bought the truck at the end of November so I really don't have a great baseline for this truck since all of my miles have been in the winter. Even last week the highs were around 34*F so I think there still may be room for improvement.
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Old 02-15-2010, 12:17 PM   #118 (permalink)
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Yeah, I just read in this article here (Pg 5....the article is real good overall though) that an extended cab truck is more aero than a regular cab. I've been wondering if the 30% aero gain and 15 -20% better mileage applies to our truck designs. The 6.5 foot bed i bet works to make the stock pick up more aero as well.

Hot Rod Magazine Aerodynamics & Wind Tunnel Article

I love this line in the Article,
"Golf-ball dimples: They do not work on cars, regardless of the scale of the dimples, unless your car is a 1.68-inch-diameter sphere spinning through the air with no ground plane."

I spray painted my aerocap black just in case I needed to dispense with the baggie wrap, Thought it would be a decent back up plan. I figure I could buy a quart of house paint too and use the existing spray as sort of a primer to put on a real good coat of preservation. Although I intend to start on my new cap in May when I finish up at the Nuc plants, I'll probably just scrap my current cap, so I probably won't bother to paint it anymore.

Something I been wondering though, what if we hit the shrink wrap on a hot day with the heat gun? I wonder if it would stay taut then?
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Old 02-15-2010, 12:31 PM   #119 (permalink)
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I was wondering the same thing. Although I wonder if there is some set amount of shrink that is possible, and once it has been shrunk, its done. However, I think that with the heat gun the shrink is not uniform, so I may be able to clean it up by shrinking the parts that bulge up. Time will tell.

The other thing I might try is to re-cover it with new plastic in the summer when the ambient temp is around 90.
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Old 02-15-2010, 01:14 PM   #120 (permalink)
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what are you talking about dimpled do work. on mythbusters they went fron 26 to 29mpgs.

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