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Single-seat ultralight puddlejumper: the "Carbonmax"

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Hephaestus

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Mylar is DuPont's name for a polyester film. Of course there are dozens of versions with different properties based on other additives used in the process.

Polyethylene is something different.
 

autoreply

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Shall we ask guys from here Projects - Airframe & conceptual design - Nieuwenhuize Engineering

How much they want for their excel slreadsheet and some trainng ? And make a group buy.

But - i will test some pieces of mine cf for buckling resistance. Truss is are truss still.
The more the better!

Joking aside; the engineering effort that goes into it is significant. I'd happily share tips&tricks, but if it requires dozens or hundreds of hours of engineering, I'll charge a commercial rate. The fundamental issue all too often is that you can't cut corners on these kind of things, you either to a full load analysis and structural design, or you cut corners that'll get you in the end.

A further discussion about "wave shear webs" probably warrants it's own thread so we don't spoil Bob's ;-)

I am still a bit confused.

Is PE polyester or another form of polyethylene?
Both.

Polyester is a wide collection of materials, including PET and raw polyester resin.

Mylar is polyethylene terephthalate that is stretched into film. Chemically almost identical to isotropic PET (plastic bottles) and fibers (Terylene, Dacron), but structurally very different because of the orientation of the molecular chains.
 

Jay Kempf

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Same as drawing mylar only without the matte finish one side and thick. The stuff we used was 12 mil. 10 mil would be fine as well. The reason you want stiff is because it doesn't take the shape of the substrate which was raw hotwired foam. So basically you lay up the laminates onto the plastic. Then put that in the bag then put the bag in between the mold halves you hot wired. Then you weigh that so that the plastic (on the outside of the layup) gets bent into it's shape while it cures under vacuum. This takes having the tool have to hold up under vacuum out of the picture.

CNC will work as well as long as it isn't too crazy a 3D shape. I just did an experiment with some plastic sheet and packing tape believe it or not seaming the plastic sheets. Laid up over the whole thing and pull out a part that only required a little trimming and sanding in some spots. I just ordered some stretchy self adhesive film from Uline to try to do a vacuum bag over a foam tool to see if I can seal it and have it stay stuck so I can remove the vacuum to use it for infusion. Trying to lower the overall workflow hours of prep of a one to six off tool.
 
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Jay Kempf

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The big surprise was making some mods to one of my molds. Just hand carved. Sanded to 400 grit, vacuumed, put packing tape on overlapping the epoxy surface. Those are the best looking surface finish on the whole part. Go figure. They released better too.

For those who suggested leave out the wax when using PVA as a mold release. Tried it. Stuck like crazy, almost lost a mold and part. Pulled a lot of the paint off of the mold surface. PVA and wax works. Wax by itself works if the surface is perfect and fully shiny but is less reliable.

I'll be trying self adhesive stretchy film on the next mold. Doing tool paths for a 4 part mold set for a large UAV fuselage right now. Working my way up to full size.
 

Steve C

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Seems like every time I get lured into trying something other than partall + pva, it sticks. You'll hear johnson floor wax is great or hair spray. It isn't.
 

davidjgall

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This might be worth a look. The pictures aren't very telling but the text in the section called "A focus on Manufacturability" is interesting if you read between the lines:

 

davidjgall

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I'll be trying self adhesive stretchy film on the next mold. Doing tool paths for a 4 part mold set for a large UAV fuselage right now. Working my way up to full size.

I think you might be on a path to reinvent this:
 

autoreply

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This might be worth a look. The pictures aren't very telling but the text in the section called "A focus on Manufacturability" is interesting if you read between the lines:

I've been doing this for a few years with great success. Especially for big, light parts (aircraft), this saves tens of thousands of dollars on moulds that'd otherwise be necessary. Pretty easy to get a perfect outside surface with infusion, compared to one-shot infusion with sandwich cores and all.
 

dana62448

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I'm anxiously awaiting airfoil selection for the Carbon Max, and I notice that the aluminum form for the leading edge
has a substantial crease as opposed to a small radius.
Those of us forced to read tea leaves are wondering if this portents a Carbon Dragon type leading edge
as opposed to the more staided 23000xxx soft nose.
We really haven't talked airfoils for the premier 103 design
and perhaps this is destined for a separate thread,
but is the excellent performance of the CD Foil as a low Reynolds Number glider
also perfect for a puddle jumper looking for high lift and gentle stall?
 

berridos

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With reference to the foxcon picture, from wich airfoil thickness are stiffeners preferable to whole ribs? Is there a rule of thumb? Would it be convenient for a 20% airfoil to use stiffeners?
stiffeners are exclusivly for buckling why ribs are for chordwise sheerstress. Is that right?
 
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Victor Bravo

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To see Mr. Riblett really roll, mention the 43013... :)
Isn't the 43 series what Schweizer used on the 1-26 glider? Bob?

There are a whole lot of us out there that can cheerfully verify the good flying qualities and relative safety of the old 1-26. I'm not aware of any Riblett-equipped glider with any better reputation than the little 1-26. A lot of gliders go faster and further, but very few of them fly any better.
 

karmarepair

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Isn't the 43 series what Schweizer used on the 1-26 glider?
Yes it is.
From Dave Lednicer's "The Incomplete Guide To Airfoil Usage":
Airframe Root Tip
Schweizer SA 2-38 RU-38A Wortmann FX 61-163 Wortmann FX 60-126
Schweizer SGM 2-37 RG-8A Wortmann FX 61-163 Wortmann FX 60-126
Schweizer SGS 1-21 NACA 23012 NACA 23009
Schweizer SGS 1-23 NACA 43012A NACA 23009
Schweizer SGS 1-23H-15 NACA 43012A NACA 23009
Schweizer SGS 1-24 NACA 43012A NACA 23009
Schweizer SGS 1-26 TG-3 NACA 43012A NACA 43012A
Schweizer SGS 1-29 NACA 63-618 NACA 63-618
Schweizer SGS 1-34B Wortmann FX 61-163 Wortmann FX 60-126
Schweizer SGS 1-35 Wortmann FX 67-K-170 Wortmann FX 67-K-150
Schweizer SGS 1-36 Sprite Wortmann FX 61-163 Wortmann FX 60-126
Schweizer SGS 2-12 TG-3A NACA 4416 NACA 4416
Schweizer SGS 2-25 NACA 43012A NACA 43012A
Schweizer SGS 2-32 X-26A NACA 63-618 NACA 43012A
Schweizer SGS 2-33 NACA 43012A NACA 43012A
Schweizer SGS 2-8 TG-2 LSN-1 NACA 4412 NACA 4412
Schweizer SGU 1-19 NACA 43012A NACA 43012A
Schweizer SGU 1-20 NACA 43012A NACA 43012A
Schweizer SGU 1-7 NACA 2415 NACA 2415
Schweizer SGU 2-22 NACA 43012A NACA 43012A
 

Pops

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Isn't the 43 series what Schweizer used on the 1-26 glider? Bob?

There are a whole lot of us out there that can cheerfully verify the good flying qualities and relative safety of the old 1-26. I'm not aware of any Riblett-equipped glider with any better reputation than the little 1-26. A lot of gliders go faster and further, but very few of them fly any better.

Wish I still owned my 1956 kit 1-26.
 
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