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Old 03-06-2011, 06:05   #16
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Re: Making a Reflective Bimini

I was showing my son the differing properties of materials in relation to sunshine, heat and reflection. His thought was that silver would be cooler than white because it is more reflective. We went out to the yard where we had white, silver, and black cars. The white was coolest by far.

Now the interesting thing was that we took a wall mirror out and laid it on a couple of sawhorses. That would be so that the heat under it would not affect the temperature. The white paint was still way ccooler than the mirror. This was all measured with a handheld pyrometer and I kept the angle consistent on all readings.

I guess what you're going to try would not work as well as you would hope. Maybe a white cover with some reflective insulation laminated under it would probably work but I believe that white is the coolest.

If you ever watch them mix paint, (automotive finishes), you would be surprised how many colors go into white. I've seen red, blue and black all put into a gallon of white base. The temperature of a pure white would probably have to be cooler. Good luck, don't take my word for it and try a few things out. Harbor freight has a digital pyrometer really cheap that would serve your needs. Stay cool, enjoy life and question everything.

Failure is most often times a temporary condition........
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Old 03-06-2011, 06:16   #17
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Re: Making a Reflective Bimini

Just curious, did you build in a water catchment system by adding edges to the bimini?........i2f

Imagine2frolic--No, I didn't make a catchment system, I considered that and made provisions for insalling one later, if I decided my cruising grounds would justify the effort. Right now, I'm just cruising Cheas. Bay and don't need that ability.

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Old 03-06-2011, 06:17   #18
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Re: Making a Reflective Bimini

I cut up a survival blanket and taped a portion to my forward hatch. I was seriously amazed at the instant heat reduction inside. And it's still see thru. Basically like mirror sunglasses.

I searched for the silvery reflective material that some car covers are made out of. I'm not so good at searching I guess. But I did run across a guy in Mexico who was making car covers with the stuff that has the soft underside to protect the car finish from scratching. Had him make a shade for me, but the material is heavy and bulky. Then when I got to Indonesia again, I saw that all car covers were made out of a lightweight reflective material. I made a local connection and bought about 23 meters of it, which is waiting for me to make another shade with.

This stuff is not so durable for long term use, as in making a bimini out of it. But it's great putting up when you get to an anchorage. It's basically a reflective coating that is applied to the material. Read-not gonna stand up to day in day out weather.
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Old 03-06-2011, 06:20   #19
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Re: Making a Reflective Bimini

Southern Drawl, I was wondering about your bimini build as well. Do you remember what brand urethane foam you used and are you sure it was urethane. The reason I asked is that I have heard about the succesful use of commonly available extruded polystyrene foam commonly called blueboard but it's also can be pink for use as a core when laminating fiberglass. The trick seems to be to rough up the surface by sanding with course sandpaper. FYI the extruded polystyrene is the smooth stuff, the expanded polystyrene is the beaded stuff and both can be found for a fraction of the cost of Core Cell and like products at any home improvement store. BOB
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Old 03-06-2011, 06:31   #20
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Re: Making a reflective Bimini

Originally Posted by James S View Post
I'm now in the process of designing my Bimini and although the rest of my "canvas" work is dark blue, I was figuring on white.
Seems like a reflective surface on the top would be the cats ass.
I wonder what materials are available for such an application.
I did experiments between our chosen "Forrest Green" Sunbrella and white. Took temperature readings under each... IF there is air flow, like under an awning or a bimini NOT currently connected to the CLOSED dodger, then the dark = opaque green, is much cooler than the translucent white. This is again, IF there is air flow, and measured at least 10" from the fabric, not right next to it. White is too translucent!

White provides limited shade to your sails as well, so with light colors, you need a liner for UV protection.

For our dodger covers, we made them white on the outside and a layer of green inside. (Opaque to protect the Lexan). This was the best... reflective AND totally opaque. It would not be advisable to double layer the bimini, however, because it would trap water between layers and be too hard to accomplish.

Good luck with it,

BTW... The same principle applies to paint. If you paint your hull with opaque GREY primer then white topcoat, it will be a couple of degrees COOLER inside than if you paint it with translucent WHITE primer, then white top coat. I made samples of each and measured the temps...
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Old 03-06-2011, 08:00   #21
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Re: Making a Reflective Bimini

In terms of sunbrella, I've gone from navy blue to a light gray, and the difference is significant.

I would worry about going to an absolute white because of concerns about stains from bird droppings. They seem to aim for my canvass these days.

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