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Wings only project

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Bille
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Re: Wings only project

Postby Bille » Mon Nov 07, 2016 5:03 pm

mcfly777 wrote: ...

Re: CNC. I am strongly considering building an entry level CNC router. Cost is about US$600 plus the time to build it. If I can have a work volume of 100x50x15cm that would be enough to make wings in one piece. I could easily build cores of foam, any plastic, or wood with reasonable precision. This machine wouldn't be machinist level precision, but here I won't need that. ...

...
Building that devise, would make for a Really good Thread ; if Ya find the time !! :D

Bille

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Re: Wings only project

Postby tkettlepoint » Mon Nov 07, 2016 7:04 pm

billie here you go cheep cnc https://buildyourcnc.com/blueChickVersi ... neKit.aspx ply wood is cheep you just need the steppers and drives
but don't try to cnc alloy like I do
terrie

skyte
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Re: Wings only project

Postby skyte » Tue Nov 08, 2016 12:09 am

mcfly777 wrote:
I'm using the Eppler 817 since it's what i've seen others doing. In my software it gives me great lift/drag ratios but as I'm not proficient in the field it's hard to argue for one versus another.

As far as AOA. The front wing should be 0 degrees. The rider controls the angle of attack. Of course if you make it a different angle, the rider will have to adapt, but that's not ideal. The angle that is important is the stabilizer. It's between 2-5 degrees relative to the front wing. You'll need to play around to find what works for your setup.

Of course this comes from a person that produced exactly 0 working wings so far :)
Hmmm... now I'm confused!

I was going to go for zero AOA on the front wing but when I looked at the Coefficient of lift vs AOA curve for the Eppler 817 it seemed to show almost zero lift at zero AOA (depending on the Reynolds number and Ncrit). So that makes me think I would have to put pressure on my back foot to increase the AOA and get some lift. However, my one and only go on a foil and advice I've heard given is that you need to get your weight over your front foot. So is the rear wing (stabiliser) creating a downforce that in turn is always trying to increase the AOA on the front wing? And this is why you need to keep weight on your front foot?... to balance the upward pitching moment generated by the rear wing?

And so... is having your front wing AOA at 2 degrees and the rear stabiliser at zero AOA the same as a front wing at zero and rear wing at -2 degrees???

I guess this is the balance we are aiming for and perhaps an answer to another thread on this forum about why you wouldn't put the mast directly above the centre of lift of the front wing... you need to create a sort of balance of moments either side of the mast and if the mast is directly over the front wing then there would only be a pitching moment from the rear stabiliser.

Another thing that had got me wondering was this article by a guy who clearly understands all the XFOIL analysis much better than I do...
http://www.foils.org/hysecdes.pdf

In it he states...
Completely cavitation free operation is also not
possible above 22 knots for any of the foils, and
there is only about a one knot difference in the
cavitation speed over the design operating range
Referring to the NACA 63-209, Eppler 817 and his H105 design.

What happens when the foil cavitates? Surely people are hitting speeds over 22knots on Eppler and NACA foils out there or are the production foils using different profiles?

All this makes me think it's best not to think too hard and just try something and see what happens!

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Re: Wings only project

Postby skyte » Tue Nov 08, 2016 12:19 am

Bille wrote:
mcfly777 wrote: ...

Re: CNC. I am strongly considering building an entry level CNC router. Cost is about US$600 plus the time to build it. If I can have a work volume of 100x50x15cm that would be enough to make wings in one piece. I could easily build cores of foam, any plastic, or wood with reasonable precision. This machine wouldn't be machinist level precision, but here I won't need that. ...

...
Building that devise, would make for a Really good Thread ; if Ya find the time !! :D

Bille
I had a CNC made from MDF that used ballscrews on the X and Z axes and a chain on the Y axis. It used cheap stepper motors and drives and was controlled via a PC running the excellent Mach3 software. The spindle was a £50 hand router bolted on. It was probably £1500 worth of kit including PC and software. I called it the Firewood 2k since half of what I made turned out to be firewood but it was an excellent learning experience and was surprisingly accurate when it worked well.

I since made a new CNC router from a machine builders aluminium extrude kit called Item. Ballscrew for the Z axis and rack and pinion for the X and Y. Ballscrews would have been better but I made it big enough to take an full sized sheet (2500mm x 1250mm or 8'x4'). Just basic stepper motors and drives and same PC and Mach3 software but a 2.2kW water cooled spindle with a decent ER20 collet.
This one came to about £5k.

The more you spend one servo motors with encoders and ballscrews etc, the more the price goes up but I reckon you could do a great small machine for £2k. With all the 3d printers out there now, the cost of automating 3 axes machines is really good now.
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tkettlepoint
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Re: Wings only project

Postby tkettlepoint » Tue Nov 08, 2016 1:36 am

sweet looking cnc there brother I should of went 4x8 but only went 32 and 50 that is heavy enough to do alum moulds. But I am looking at making a board shaper this winter. 32x120 I work for a cnc company part time and can get all the rails /steppers/ racks at cost now and have enough 80/20 to build 4 machines


terrie
Last edited by tkettlepoint on Wed Nov 09, 2016 11:56 am, edited 1 time in total.

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downunder
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Re: Wings only project

Postby downunder » Wed Nov 09, 2016 3:08 am

^
jeez, you're killing me :) Awesome.

tkettlepoint
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Re: Wings only project

Postby tkettlepoint » Wed Nov 09, 2016 11:56 am

downunder will everything you build you need one LOL not a matter of want any more.

mcfly777
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Re: Wings only project

Postby mcfly777 » Thu Nov 10, 2016 3:38 am

Update: printed all parts in PETG. PLA was too brittle and ABS warped too much. I fit all 5 sections of the wing in one print job, took 24 hours to print it all. The middle part (root) alone can easily handle my entire body weight with 40% infill. PLA couldn't do that.

Now I'm gluing the sections together, then sanding it to get ready for the carbon. I had to use special glue that states that it works with PE.
2016-11-07 16.24.13.jpg
2016-11-07 16.22.48.jpg
2016-11-07 16.22.36.jpg
Capture.JPG

mcfly777
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Re: Wings only project

Postby mcfly777 » Thu Nov 10, 2016 5:47 am

I glued all the sections. There are some areas that I need to fill. What do I use to fill these parts? Bondo?
thanks

mcfly777
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Re: Wings only project

Postby mcfly777 » Thu Nov 10, 2016 9:25 pm

Everything glued. Now filling and sanding.
2016-11-10 11.33.56.jpg
2016-11-10 11.34.07.jpg


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