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Old 10-05-2012, 09:00 AM   #81 (permalink)
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Quote:
Originally Posted by a8ksh4 View Post

Seems that I will need ~3 gallons of resin for this, given it's size. What's the best way to do the seams where sheets of cloth meet? The cloth is about 3' wide, so I'll have several seams along the shell. Should I sand the foam a little lower where the sheets meet so there isn't a rise that I have to body-fill around? That makes sense to me...
What weight is your cloth?
When I did my camper I didin't find the overlap any problem but that is with 2 or 3 layers of 6 oz cloth. With 6 oz. cloth it is hard to tell where the overlap is. If your going for a nice final finish you are probably going to skim the outside with a filler anyway.

I suppose strips of peelply or nylon fabric would help in holding the seems down if they are a problem but I would try just overlaping the cloth an inch or two first.

Also just fiberglassing the outside and not glassing the inside may be ok for some coast-down testing or whatever but I would glass both sides to get the full benefit of the foam which is just the core to separate the the 2 skins of fiberglass.

skyking started a thread I found earlier that may be helpful for glassing mostly flat areas. But I guess your project is mostly compound.
http://ecomodder.com/forum/showthrea...yup-20811.html

Thanks for posting your progress


Last edited by turbothrush; 10-05-2012 at 09:59 AM..
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Old 10-05-2012, 12:48 PM   #82 (permalink)
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Talk is cheap; doing and testing is what matters. MythBusters already proved that dimples save significant fuel on a moving vehicle. Check out episode 127.
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Old 10-05-2012, 12:52 PM   #83 (permalink)
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I would not say Mythbusters "proved" anything.

There were significant problems with their test (most of their tests). Always entertaining, but viewer advisory: skepticism is strongly advised!

Discussion - see: http://ecomodder.com/forum/showthrea...tml#post139241
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Old 10-05-2012, 01:47 PM   #84 (permalink)
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Quote:
Originally Posted by ACEV View Post
Talk is cheap; doing and testing is what matters. MythBusters already proved that dimples save significant fuel on a moving vehicle. Check out episode 127.
I first came to Ecomodder.com 3 years ago wondering how to make dimples on my truck without adding 600lbs of clay. I was wondering why it wasn't done everywhere, then I got edjumacated. Golf ball dimples don't have the desired effect on cars.

But, don't take my word for it.

Here's an article from a few years back written with Gary Eaker, a former GM & Hendrick Motorsports aerodynamicist.

You're looking for:


Quote:
Aero Stuff That Doesn't Really Matter
In addition to our list of five tricks that almost always work, here are some things A2 customers might want to try that are really a waste of time.


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.
Hot Rod Magazine - Car Aerodynamics Wind Camp Tech Theory

His talk is Very, Very, Very, expensive, feel free to try and contact him regarding his remark and explain why he's wrong.

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Old 10-05-2012, 02:54 PM   #85 (permalink)
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To make the seams reasonable cover them with strips of rip stop nylon or polyester cloth. It holds them nice and flat. I cover the entire section of composite with strips of this cloth. Once cured at least past green, peel the cloth off. Yes overlap by at least an inch or more.

I skipped how I do the layup, it goes something like this: For a wet layup we usually spray glue the composite onto the foam and then paint on the epoxy and use the peel ply.

If I were covering the inside or any underside, I would turn it upside down before starting. Let gravity be your friend.

The nice thing about peel ply is that it leaves a perfect finish to do secondary layup on without sanding.

Quote:
Originally Posted by turbothrush View Post
What weight is your cloth?
When I did my camper I didin't find the overlap any problem but that is with 2 or 3 layers of 6 oz cloth. With 6 oz. cloth it is hard to tell where the overlap is. If your going for a nice final finish you are probably going to skim the outside with a filler anyway.

I suppose strips of peelply or nylon fabric would help in holding the seems down if they are a problem but I would try just overlaping the cloth an inch or two first.

Also just fiberglassing the outside and not glassing the inside may be ok for some coast-down testing or whatever but I would glass both sides to get the full benefit of the foam which is just the core to separate the the 2 skins of fiberglass.

skyking started a thread I found earlier that may be helpful for glassing mostly flat areas. But I guess your project is mostly compound.
http://ecomodder.com/forum/showthrea...yup-20811.html

Thanks for posting your progress
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Old 10-05-2012, 06:57 PM   #86 (permalink)
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Please see update on the golf ball dimples thread. No one can argue with actual results unless they do other tests.
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Old 10-05-2012, 07:10 PM   #87 (permalink)
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Quote:
Originally Posted by ACEV View Post
Talk is cheap; doing and testing is what matters. MythBusters already proved that dimples save significant fuel on a moving vehicle. Check out episode 127.
Jamie,or the other fella on MythBusters is supposed to be a degree'd engineer.If that's so,he would have had to have passed a course in fluid mechanics.If so,he would have had to understand boundary layer theory and Reynolds number effects.
The very testing of the dimpled Taurus belies an ignorance of the fundamentals of boundary layer flow when viewed in the dimensions of a full-scale automobile.
The episode concept should have been a non-starter,as it was as revelatory as demonstrating that you can cool a burning person by pouring liquid gasoline on them.Nobody benefited from the exercise.
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Old 10-05-2012, 08:05 PM   #88 (permalink)
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What a person takes in class determines what kind of engineer they are. The assumptions given are not germain to the issue.

Actually, we have verifiable results that can be duplicated. I believe that one should attempt to duplicate them if they don't believe them to be correct.
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Old 10-05-2012, 08:33 PM   #89 (permalink)
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I would like to request that you start your own thread on dimples.

This thread IS NOT about dimples.

This thread IS NOT about your opinion on dimples.

This thread IS about someone using enginuity and fine craftsmanship in building an aerodynamic shell for the back of his truck; one without dimples.

I enjoy reading this thread and the constructive comments made by others.

Please be courteous and start a new thread about dimples rather than redirecting this thread.

I believe I understand your position on dimples. If I desire to know more about your position in dimples, I will look for your separate thread.
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Old 10-05-2012, 08:49 PM   #90 (permalink)
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I agree. It was wrong for some to take exception to simple recommendations to the project in question. This is only about the project and how to help with it. I will reiterate to those who wish to discuss dimples to simply go to the appropriate thread.

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