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Old May 18, 2014, 10:56 AM
Registered User
South Africa
Joined Feb 2010
1,095 Posts
I have a feeling we are talking past each other, wing depth ie chord is 21cm and at wing tip the chord is 17cm.
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Old May 18, 2014, 12:18 PM
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Extreme Sports's Avatar
South Africa, GP, Johannesburg
Joined May 2012
441 Posts
Quote:
Originally Posted by Axefly View Post
I have a feeling we are talking past each other, wing depth ie chord is 21cm and at wing tip the chord is 17cm.
Don't think so. By depth I am not referring to the chord (or breadth)...depth (or thickness) is the thickest part of the wing if you cut a slice of it and look at it end on so that you see the airfoil profile...usually approximately the thickness of the spar plus the thickness of the wing skins. My understanding is that for your design it is 15mm. This is the dimension that can be made thicker to give the wing more bending strength....but at the expense of drag. Likewise if its too thin no material in the world will be strong enough (think of a 1mm steel wire or CF rod...very easy to bend).

Given the relatively rough properties of correx, are you sure that you will see the benefits from such a thin wing?...IMHO there too many other sources of drag that will outweigh the marginal drag reduction of a thinner profile. Is there any reason why you cannot use a thicker profile? After all, aircraft are all about compromises and very often compromises have to be made to get the required structural strength.

Yup, its definitely going to be hard to make such a long, thin wing rigid enough for high speed flight....but I guess that's why you started this thread. I'll definitely continue to watch with interest, and good luck
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Old May 18, 2014, 01:42 PM
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South Africa
Joined Feb 2010
1,095 Posts
spar will be 15mm high so with the 2mm correx i guess the depth is 19mm.

like mentioned i have done this with a 1.7m wing and flown it, for some reason it was just unstable not because of flexibility, it was as stiff as a 1.2m wing with the same depth that i currently fly very successfully but rather it was most likely unbalanced span and chordwise.

Greater depth wings tend to create too much drag with regards to my experience in building faster wings and flying them . Besides so far the 19mm depth has worked on 1.2m wings i made without breaking up.

The 1.7m wing i could not thoroughly test because it was very unstable in the air, i still think it was due to one of the doublers placed more aft of the wing instead of right up against the spar and the wing felt a bit heavy leaned towards one side when checking the balance, however it was as stiff as the smaller wings i made. also had 2 more servos,control rods as i added flaps so made it more heavy, the covering also was reflective covering heavier than the normal vinyl)

I'll post my results when done, still going to be a while because i am moving to a new place, and i wanted it to be done already by next weekend... !
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Old May 19, 2014, 08:17 AM
Crash Test Dummy
Brunei, Brunei-Muara, Masin
Joined Nov 2013
130 Posts
Hey Axe, I just bought a bunch of CF tubes and strips form this bloke, and he's pretty cheap, even with FedEx shipping: http://www.aliexpress.com/store/prod...695755627.html

Actually, don't believe the shipping cost - mine, which included about 10x 1mmx5mmx1000mm CF strips, 30 CF tubes and some other stuff, only came to US$30.

He has all sorts of sizes - including ones that aren't on his list - I suggest using the online chat function - nice guy, very responsive.
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