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Old Aug 23, 2011, 03:14 PM
CNC Cutter
birdofplay's Avatar
United States, IN, Indianapolis
Joined Dec 2005
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It is SOOOOOO nice to see someone in this forum
who is NOT interested in doing 200 mph !!!

I may take your Ribs and DO UP a Ribbed version.
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Old Aug 23, 2011, 03:23 PM
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miniphase's Avatar
Kent, UK
Joined Nov 2004
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Thanks Bob, I'll be glassing over foam cores along with some some carbon for this one. Hopefully that will keep the dreaded flutter at bay.
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Old Aug 23, 2011, 03:52 PM
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sawman's Avatar
Louisiana
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Sigh... I wish I had building skills. And flying skills.

This would be a really cool platform.
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Old Aug 23, 2011, 03:56 PM
CNC Cutter
birdofplay's Avatar
United States, IN, Indianapolis
Joined Dec 2005
8,609 Posts
I just tossed together somethign from your provided pix.
Assuming 3.2M span.

Sheeezzz that is one THIN foil section ! ! ! I get ~ .78"

or most likely about 20mm thick
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Last edited by birdofplay; Sep 21, 2011 at 06:08 PM.
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Old Aug 23, 2011, 10:40 PM
internet gadfly
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Colorado
Joined Aug 2006
2,165 Posts
Man that's a thin, skinny, center section. With that much sweep you're going to have a lot of torsion to absorb. Be ware of flutter and build stiff not just strong!

--Norm
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Old Aug 23, 2011, 11:14 PM
CNC Cutter
birdofplay's Avatar
United States, IN, Indianapolis
Joined Dec 2005
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Edwinzea and Norm:

yeah these foils looked WAY thin to me.
( might as well make a foamy ;-}

It's looks kinda DLG like to me.

But a Thermal-able Wing was the Criteria and calc's were made so ...
I'm just asking you guys to look again and see if it still makes sense at this thickness.

Bob

I took miniphase's top view drawing , scaled to 3.2 meters
Took cords and scaled the rib drawings to the derived chord .
Then placed them in position with the tapering washout still intact.

I then made surfaces at each section using the curve from the TE
by sweeping it along the two rib curves.

all in all only a few minutes of CAd time :-)

Bob
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Old Aug 23, 2011, 11:38 PM
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Quite likely take some exotic construction to build that with enough stiffness and yet maintain a low enough wingloading for thermaling.
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Old Aug 24, 2011, 05:12 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,891 Posts
well I will try to reply in order
@ Paul, the airfoil should thicken from root to tip not otherwise as you wrote. Check the ZIP I added on this thread with the composite construction, you will need some cap spars to keep the wing without flutter. and you can always edit the title of the thread :P

@Bob, the airfoils are thin in % but counting with the chords there are about 2cm think enough for good servos. Furthermore, the thinner airfoil produce enough lift for the task at low speeds and reduces the drag, which is already increased by the washout, so is a matter of compensation. if You want I have a 2m design that I can provide you. the ribbed version will need extra care on the spars to avoid flutter

@Norm, I thoght of making a three piece wing, in that way the center can be properly reinforced to absorb the torsion

Regards

EZ
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Old Aug 24, 2011, 05:15 AM
the answer 42 is
Switzerland, AG, Lenzburg
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Quote:
Originally Posted by DT56 View Post
Quite likely take some exotic construction to build that with enough stiffness and yet maintain a low enough wingloading for thermaling.
Not really you need the right material in the right place

EZ
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Old Aug 24, 2011, 05:37 AM
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Kent, UK
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Quote:
Originally Posted by Edwinzea View Post
well I will try to reply in order
@ Paul, the airfoil should thicken from root to tip not otherwise as you wrote.
Regards
I think you may have misunderstood my earlier post, we're describing the same thing but coming at it from different directions.

The tip is nearest to the original thickness of the HS520, so the section gets thinner from the tip to the root, not thicker from root to tip...sorry to be a pedant

I think with a carbon d-box and spar cappings she'll be stiff enough. I was thinking of buying 50mm carbon tape (at 200gsm) rather than cloth. I won't get the benefit of a bias weave, but it'll be easier to handle than cutting strips of cloth.

On another note of concern, will the thinned root section have undesirable stall characteristics?
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Old Aug 24, 2011, 06:14 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
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mmm good question, but in fact I followed the design principles from the Zupair wing and it seems to work nicely on their videos also seems to work very well on XFLR5, the thinner airfoils have a slightly better glide ratio and less drag though. Again this design is orientated to thermal flying, and I thought that even a slight increase was a bonus that also goes for the Lift, but we will only know when it is in the air :P

Regards

Edwin
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Old Aug 24, 2011, 06:59 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
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Quote:
Originally Posted by birdofplay View Post
It is SOOOOOO nice to see someone in this forum
who is NOT interested in doing 200 mph !!!

I may take your Ribs and DO UP a Ribbed version.
You can always build this one http://www.zanonia.de/yoda.php

EZ
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Old Aug 24, 2011, 10:47 AM
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United States, IN, Indianapolis
Joined Dec 2005
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Hey, those are some nice thermal machines.

Gotta get out my translator
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Old Aug 24, 2011, 03:57 PM
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Quote:
Originally Posted by eflightray View Post
What about the Hump ?, the plan is still available - http://www.myhobbystore.co.uk/product/15966/sf423--hump
Or the Redwing?

http://www.glide.net.au/on-the-wing4...Redwing-3A.pdf
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