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Old Aug 03, 2011, 04:00 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,897 Posts
Hey Paul

I just draw you wing in ACAD and made the Model in XFLR5, best CoG 410mm 409mm to fly very slow

Honestly said the wing does not perform as well as other of your designs I had modeled, at the given CoG the glide ratio is less than optimal, and the trim speed is higher than the optimal speed for best glide ratio, this can make a good slope wing but it will make a less efficient thermal wing.

I tried several combinations of washout being the best

X= 0mm 0°
X= 850mm 1.5°
X= 1360mm 2°
X= 1630mm 2.5°

What I have found lately is that the variable washout works best with non FW profiles, or at least in combination of profiles through the wing, in my case I used two series of Drela profiles AG and HT.

I think a wing like your design will be overly complicated to build and at least the predictions from XFLR5 are not too encouraging, still you have already proven me wrong with the EH profiles so you will have to follow your gut

Finally I would recommend you the design I send you some weeks ago, it is simpler to build having linear wash out and only two chords. Moreover, the predictions are much better for it.

Have fun

with kind regards

EZ
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Old Aug 03, 2011, 05:10 AM
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miniphase's Avatar
Kent, UK
Joined Nov 2004
870 Posts
Quote:
Originally Posted by Edwinzea View Post
I think a wing like your design will be overly complicated to build and at least the predictions from XFLR5 are not too encouraging, still you have already proven me wrong with the EH profiles so you will have to follow your gut


EZ
Thanks for taking the time to do this for me Edwin...shall I plough ahead and see how it performs?

I'd find a constant chord 'wing easier and simpler build than a tapered planform, and I'd have to cut each semi-span in three parts anyway so that lends itself perfectly to the 3 stage washout.....unless you feel the linear washout would be better?

This would then mean the model will be a 3.2m version of my 2.4m 'wing. This 'wing stays up with Alulas and DLGs in marginal conditions so I'd have faith in its soaring ability, and afterall I'm not planning to compete with it.....
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Old Aug 03, 2011, 06:14 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,897 Posts
No problem, I enjoy helping around :P I think the clue here is to have a soft taper and to keep the thickness of the wing along the span, which means having higher thickness percent in the tip as in the root. From this perspective the linear washout works well. This is very similar to what one will get from a constant chord wing but it seems that the taper helps in the glide ratio in general and reduces the trim speed which is positive for the thermaling application, still we need to build, fly and test

I am thinking in building a bigger cutting bow in that way I can cut the panels at once, but I have to decide.

I am attaching a file to calculate the composite structure of your wing is very cool and you can check several combinations. I just ordered the Skynavigation system to test my wings more "scientifically" (NERD) and with the dollar so cheap I could not resist it

regards

EZ
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Old Aug 03, 2011, 06:27 AM
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miniphase's Avatar
Kent, UK
Joined Nov 2004
870 Posts
Thanks Edwin, I apreciate your help. I just haven't got the time to invest in learning XLFR5 at the moment, but I can see what a powerful tool it is.
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Old Aug 03, 2011, 07:29 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,897 Posts
well I think it simply help us avoiding un interesting mistakes, so we can go and make the interesting ones the XLS file calculates the skins you will need for your composite construction, I think for the 3m wing you might need to use some cap spars

Regards

EZ
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Old Aug 05, 2011, 06:53 PM
a wing is enough
Tail Saw's Avatar
Germany
Joined Aug 2010
98 Posts
Quote:
Originally Posted by DT56 View Post
Here's one for inspiration!

http://www.rc-network.de/forum/showt...%28-Kr%E4he%29

The text isn't English, but lots of photos.
Hey, thats funny, itīs me

This plank was made for slope fun with a little bit of thermal suitability. I had a little accident at the rubber launch with it long ago. The Plank is repaired, bud at present no servo is in the wing, so the testing was not completed.

I have designed a follower, but not yet built.
Everything has its time...now itīs time to go to bed with dream-

Uwe.
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Old Aug 05, 2011, 10:15 PM
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Originally Posted by Tail Saw View Post
Hey, thats funny, itīs me

This plank was made for slope fun with a little bit of thermal suitability. I had a little accident at the rubber launch with it long ago. The Plank is repaired, bud at present no servo is in the wing, so the testing was not completed.

I have designed a follower, but not yet built.
Everything has its time...now itīs time to go to bed with dream-

Uwe.
Uwe, thanks for posting the great build thread on that other website!!! There's a lot of good information there for other builders! It looked like it flew very well.
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Old Aug 13, 2011, 06:09 AM
Will work for foam
wingnutt's Avatar
United States, WI, Muskego
Joined Apr 2005
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miniphase - This is a great build. I am following with interest. Are you going to go with a tractor or pusher config for the motor? Also, what made you go with your choice?
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Old Aug 21, 2011, 01:10 PM
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Louisiana
Joined Oct 2005
1,196 Posts
Bump for updates.
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Old Aug 21, 2011, 03:43 PM
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Kent, UK
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Originally Posted by wingnutt View Post
miniphase - This is a great build. I am following with interest. Are you going to go with a tractor or pusher config for the motor? Also, what made you go with your choice?
Hi Wingnutt, I know it's inefficient and hand choppy, but I love the aesthetics of a pusher prop so I'll be aiming for that in the first instance.
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Old Aug 21, 2011, 03:51 PM
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Kent, UK
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Originally Posted by sawman View Post
Bump for updates.
Sorry sawman, I've been undergoing a protracted period of procrastination and indecision.

The original layout I was thinking of is so close to a wing I've already built, I'm thinking I should invest the time in something new and have been thinking about Edwin's design which he feels would be a better performer.

Edwin, have you still got any of the details to hand? maybe you could share them with us and summersie the benefits.

Regards

Paul
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Old Aug 22, 2011, 03:09 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,897 Posts
Well I am a bit away from wings now :P I am building a new set of wings for one of my F5J planes :P I have the supplies but my time is more limited than ever :P Moreover, I am having problems with the electrified versions of the wings, it has been very challenging for me to adjust the trust angles in the motor :P while they fly very well in the slope.

From the XFLR predictions the wings benefits from the constant thickness and the swept produces by the reduction in the chord. The profile HS 520 seems to give no great pitching attitude with flaps deployed, which is good. With a big cutting bow one could cut the wing in one go, which is in my future plans, it is also possible to cut it on three piece. I think i send you the CAD file with all the details, just let me know if I forgot to do it :P

I have ordered a power set up but i still need to decide where I am going to put it. The advantage of a 3m wing is that one can have a longer nose and a longer prop without affecting too much the CoG. Furthermore, I really don't want a 17x11 prop spinning behind my valuable hands :P a tractor set up will require a long fuse which helps to visualize the wing's attitude in the distance while thermaling

Regards

EZ
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Old Aug 22, 2011, 03:35 AM
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Kent, UK
Joined Nov 2004
870 Posts
Hi Edwin

Yes, I still have the file thanks....so it's the HS 520 but modified so that the wing has the same thickness from root to tip.

Shall we go with that then? Would you be happy for me to build your design Edwin? As I mentioned earlier I'd prefer to try something new, rather than just build a bigger version of my previous 'wing.
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Old Aug 22, 2011, 06:00 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,897 Posts
Hi Paul,

well I will be honored if you build it it somehow got very low in my todo list, so I will be more than happy to it flying. and yes the thickness of the HS520 changes from root(6.8%) to tip(8.1%) -3° washout -2° dihedral. I still need to calculate the tips but that does not take lots of time

regards

Edwin
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Old Aug 23, 2011, 01:55 PM
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Kent, UK
Joined Nov 2004
870 Posts
Right then Edwin, I'm in your hands! I hope no one reading the thread will feel short changed when they get to the end and realise the finished model is only 3m span!

I have plotted the wing sections and washout today and attach the screen grabs. I have thinned the HS520 progressively toward the root so the tip is at the original thickness and the wing thickness itself is constant.

I have also modified the templates so I can pin them to the foam at 90 deg to the leading edge, the section will then come true when I trim the tip and root for sweep.

I'll cut each semi-span in 3 sections governed by the size of my bow and my supply of raw materials.

That root section will end up mighty thin Edwin...hope I won't be selling myself short on lift. Mind you I suppose the flaps will allow me to dial in some camber.....
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