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Old 09-22-2014, 10:22 PM   #161 (permalink)
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Just came from a visit to the National Soaring Museum. Many gliders use aluminum skin over a frame of 1 in. square tubing. A number of sites have plans for free. My favorite is www.vintagesailplaner.com/Sheet1bis-9.pdf Reduce the scale to view the whole drawing of the fuselage. I cut the tail at the sixth bulkhead.


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Old 09-22-2014, 11:47 PM   #162 (permalink)
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Quote:
Originally Posted by jray3 View Post
I'd like to build a trailer shell following the template, but with flat panels that are precut to shape, zeppelin-style. Undecided on a riveted aluminum skin vs foam panels to then glass over, or soaking an inflated envelope with resin, then building it up, but am leaning towards aluminum (possibly with a spray-foam interior layer to stiffen and insulate).
So far I've struck out on finding a pattern to scale up. Closest thing is these hot air balloon panels from a crafter's blog (don't laugh if you click through).
http://prudentbaby.com/wp-content/up...ir-balloon.pdf

DIY Hot Air Balloon Mobile (Free Pattern!) | Pretty Prudent

This company gets me close, have requested a design cost estimate....
APEX Balloons - Hot Air Balloon Manufacturer, Hot Air Airships, Balloon Repair Station

Any of you design wizards already cracked this nut?
Graham, eh?
Maybe we need to get together and do some brainstorming. I too have a trailer or two stuck in my brain; my medium is probably going to be XPS foam, shaped and then glass/epoxy.
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Old 09-23-2014, 01:30 AM   #163 (permalink)
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jray3 -- Thanks for asking.

Call it a pet peeve. I'll point to posts at...

http://ecomodder.com/forum/showthrea...ted-26565.html

http://ecomodder.com/forum/showthrea...ion-23333.html

I need to gather up some scraps of PolyMetal and run them though a shear/roller/brake. Then I can demonstrate a building technique to try. Roll a 45 edge, flange that and rivet together to get a radiused corner with one riveted seam in the middle. It's like two layers of beer can with sound deadening material in the middle. With an enamelled finish, lot's faster than fiberglass.

Here is a template for a bicycle:


I prefer this design with the gores running the other way:


But wait—there's more!

To precisley control the surface you create to whatever accuracy you require, use geodesics. Specifically an octahedral symmetry 4 to 6 frequency sphere as a starting point. Some examples:




/Did you know I'm building an elecric car?

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Old 09-23-2014, 01:15 PM   #164 (permalink)
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Quote:
Originally Posted by freebeard View Post
jray3 -- Thanks for asking.

/Did you know I'm building an elecric car?

Thank you SkyKing and Freebeard!
Glad to find a local ecomodder, SkyKing. Perhaps you'd like to get breakfast or lunch one day at Thun Field?

Freebeard, I know you're in the know, but I'm very deep in the EV world, so don't hesitate to call if I can help.

I've reviewed the links, but the MOAT is still closest to what a simple hacker like me might be able to do. I'd just build two identical ends with a clamshell lift for the back end, and box in the tail floor forward until the body is wide enough for practical drop ramp.

I've got polymetal samples on my desk. Neat stuff. Not great fracture resistance though. The street sign on my corner snapped cleanly off when hit by a falling tree branch.
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Old 09-23-2014, 02:45 PM   #165 (permalink)
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Quote:
Freebeard, I know you're in the know, but I'm very deep in the EV world, so don't hesitate to call if I can help.
People keep capitalizing my handle, even when it doesn't begin a sentence. ???

So I may be self-educated through the Aerodynamics forum, but in the Fossil Free Fuel forum they go right over my head. I still wonder what an 'attiny' is; and on a broader scale I have no idea whether kilowatt-hours or Coulombs are more important.

I'm on hold until the space frees up to work in. It's supposed to happen today, again. The first question to resolve is whether a VW axleshaft will bolt right up to a Toyota flange. Wouldn't that be nice?

I'd really like to see some pictures of PolyMetal in failure modes. Do you think doubling the thickness of the skins or doubling the thickness of the core would help more? (I'd go with skins) Both are available as shipping product.

There's also swingdoor material, skinned plywood. That could make for a good deck. Just soak the cut edges in resin to completely waterproof it.

Quote:
the MOAT is still closest to what a simple hacker like me might be able to do
The Roswell has radically less seams to join. And edges to cut—but really just the same otherwise. Would you flange the edges, or capture the flat edge in an H-channel?

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Old 09-23-2014, 06:08 PM   #166 (permalink)
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I'd double the polymetal skins for rolled curves or brake bending- they can 'pop like a grape' under too much tension. But again, I haven't tried controlled bending yet.
I thought the Roswell included compound curves, so didn't look further.
Seems the MOAT could be done with curved pie cuts and creases rather than so many separate panels with seams.
If the material is thin enough, I'd try a dart rather than a full pie cut, or more easily, just slice and make an overlapping seam (dunno a term for that)...
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Last edited by jray3; 09-23-2014 at 06:22 PM..
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Old 09-23-2014, 11:10 PM   #167 (permalink)
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Shingled lap joint?

Once again I'd like to see failure modes, as in 'popped like a grape'.

I have access to an hand-operated roller/shear/brake with an 18" lever arm. I stopped on the roller at a 12" radius, but I could have kept going. Shearing was adequate. When I tried to brake a 90 angle, it popped the skin on the outside. A score or shallow saw cut on the inside is indicated. With a router I could rabbet opposing side of a join and create a half-lap. That would be awesome. Also for counterboring holes for through-fasteners but it would take more hand-waving to explain that. Needs pictures.

Back on the subject of the Template. You can un-peel those geodesics and get basically gores with darts. Also needs pictures.
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Old 07-26-2015, 10:41 PM   #168 (permalink)
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Quote:
Originally Posted by ECONORAM View Post
Yes I do, but in order to do that I need to rig up something in the garage to hold the current (drag increasing) topper. In the meantime, I plan to work on a Kammback, maybe even something that resembles one of these:http://c1gas2org.wpengine.netdna-cdn...trucktail1.jpg if the picture link does not work: Tractor Trailers with Tails Improve Fuel Efficiency by 7.5% - Gas 2 but not 6 feet long!?
Well, 2.5 years later, I was finally able to put together some saw horses to hold the topper in the garage and fab a tonneau cover for the bed. After two trips between San Antonio and Springfield IL I've determined the topper doesn't change drag significantly over a topper. There is a weight penalty, of course. So, the topper is back on! Truck looks better with it anyway... Getting some mounts figured out for the Kammback finally.
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Old 07-28-2015, 02:38 AM   #169 (permalink)
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Quote:
Originally Posted by ECONORAM View Post
I've determined the topper doesn't change drag significantly over a topper.
Will you please clarify that? Are you comparing two toppers or a topper and a tonneau cover? Thanks!
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Old 08-03-2015, 11:14 PM   #170 (permalink)
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Sorry Xist. I meant between a tonneau cover and the LEER topper I have. The topper is basically level with the roof of the cab, and the corroplast bed cover was level with the bed rails. Didn't seem to make much aero difference. Now weight difference, certainly. It was obvious when going up hills. I'd try some A-B-A testing, but with my knee that's probably not a good idea. Besides, I have to have help to get the topper on and off the saw horses I made for it...

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