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Old Oct 31, 2011, 05:55 PM
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XXlite

hi all,

this thread will be about my new dlg project, it's not a helios succesor but a project beside it.

i wanted to experiment with a high ar wing , so i got my old wing and fuse mould back on the machine and cut out these part's....

root chord of the wing is only 135mm and it has the zone v2 foil's
because of the extreme thin wing , no servo's can be fit into, so all 4 will go in the fuselage

even tough the nose of the fuselage is shortend to 175mm , 4 servo's can be fitted and the "big" helios ballast system can be integrated too
canopy is on the bottom of the fuse now , so the aileron linkage can be done quite easely.

target weight is 200gr or maybe a little more , i plan to use 2 ds 285's on the ailerons

her you go...
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Old Oct 31, 2011, 09:03 PM
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Looks cool as usual!

Hope it exceeds all your expectations.

Send one to Kyle so I can see it up close! Haaaa

All the best,
Eric
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Old Oct 31, 2011, 09:54 PM
G_T
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I'm looking forward to seeing how this works out!

Gerald
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Old Nov 01, 2011, 06:15 AM
Hey was that a Thermal ????
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This is looking cool, I am hoping it flies as light as it looks.

luaP
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Old Nov 01, 2011, 06:30 AM
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Interesting, will watch closely!
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Old Nov 01, 2011, 07:20 AM
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Only 135mm chord! Will be very interesting!
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Old Nov 01, 2011, 07:51 AM
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Good luck!
It will be very interesting to hear your experiences from this high AR design.

Some older threads on the same subject

Regards
Mattias

http://www.rcgroups.com/forums/showp...72&postcount=2
http://www.rcgroups.com/forums/showp...1&postcount=69
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Old Nov 01, 2011, 08:11 AM
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hi mattias,

it seems i can't find the thread these post's came out off , does it still excist's?

from looking at the pictures the wing area is somewhere around 15 dmē is that correct? mine is 17.17dmē with a target weight of 200gr , weight will be very important on such a plane i supose.

thanks for you're input

-kristof-

edit: found the thread

Quote:
Originally Posted by Oystmyr View Post
Good luck!
It will be very interesting to hear your experiences from this high AR design.

Some older threads on the same subject

Regards
Mattias

http://www.rcgroups.com/forums/showp...72&postcount=2
http://www.rcgroups.com/forums/showp...1&postcount=69
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Old Nov 01, 2011, 08:37 AM
Aurora Builder
United States, MD, Lusby
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Looking good Kristof, I find it interesting that some are going high AR (better L/D) and some have gone low AR (better Reynolds numbers). Perhaps time will tell which is better, everything is a compromise!
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Old Nov 01, 2011, 09:37 AM
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certainly a very interesting project.
Disadvantage is that airfoils optimised for lower Reynoldsnumbers are thinner and therefore have a lower Clmax. It might be interesting to desing an airfoil for these lower Reynoldsnumbers with a wider Cl range . This might be achieved by using a turbulator on the upper site of the airfoil just in front of the hinge line.

Bas
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Old Nov 01, 2011, 10:03 AM
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Originally Posted by samc99us View Post
Looking good Kristof, I find it interesting that some are going high AR (better L/D) and some have gone low AR (better Reynolds numbers). Perhaps time will tell which is better, everything is a compromise!
sam,

i don't expect to be an allround plane , when it get's turbulent and windy it won't be the better choise i supose..

-kristof-
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Old Nov 01, 2011, 10:10 AM
Aurora Builder
United States, MD, Lusby
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Yes, I assume this aircraft would be best suited for smooth air and attempting to maximize launch and minimize sink? My question was more in design theory. For example, with a lower aspect ratio wing, one can beef up the structural stiffness quite readily, and the airfoils operate at higher reynolds numbers, which tend to be more forgiving. But higher aspect ratio provides lower induced drag for a given amount of lift. Where is the dividing line?

I am excited to see you build an airplane optimized for the 220g range, of course I hope this doesn't start a war where we need 4 or 5 airplanes to cover all flight regimes, but it looks like it is heading that way!
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Old Nov 01, 2011, 01:35 PM
Oleg Golovidov
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Quote:
Originally Posted by samc99us View Post
But higher aspect ratio provides lower induced drag for a given amount of lift.
Sam, if you did not add the second part to your sentence, it could be true. A higher aspect ratio wing CAN have lower induced drag if the span was increased. But, if the amount of lift is fixed and the span is fixed, the induced drag is fixed, or rather is determined by the speed.
What DOES allow us to reduce the induced drag in this case, is a lower weight of the model. At the expense of some increase in the profile drag and lower stiffness/strength, as you mentioned.
Sorry, this can get the thread off track, but it is kinda related.
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Old Nov 01, 2011, 04:44 PM
Aurora Builder
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Well, I think we are arguing technicalities but at the end of the day you are right. For a given wing span AND wing area, then yes induced drag may be the same for high AR and low AR, however, airfoil choice has something to say about lift! If you ignore wing area and drive for high AR, then induced drag is lowered at the same speed needed to generate the same amount of lift. This speed may not be optimal and in our case is driven by weight. That is why this airplane will need to be built light, but it is clear that Kristof is a pro and can hit the target weight quite readily!
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Old Nov 01, 2011, 05:05 PM
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sam,

yes i don't think it will be far off..., i calculated wing volume and area an i know what the helios part's weigh so i came just under 200 gr rudderless, but i would like to have a moving rudder so i expect it to be a few grams above 200

i also hope to be able to have the helios tailgroup a few cm shorter to the wing on it(gonna make a seperate horizontal pylon mould , the last few cm of the boom is not conical so it can be fitted anywhere on that last section.

on my lightest helios i was able to move the vertical a few cm more to the front , no bad effect on launch noticed , that's because of light tailset and gear in the nose (not so much needed to damp out after launch)

-kristof-


Quote:
Originally Posted by samc99us View Post
Well, I think we are arguing technicalities but at the end of the day you are right. For a given wing span AND wing area, then yes induced drag may be the same for high AR and low AR, however, airfoil choice has something to say about lift! If you ignore wing area and drive for high AR, then induced drag is lowered at the same speed needed to generate the same amount of lift. This speed may not be optimal and in our case is driven by weight. That is why this airplane will need to be built light, but it is clear that Kristof is a pro and can hit the target weight quite readily!
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