3 metre slope and thermal wing - RC Groups
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Jan 19, 2012, 05:09 AM
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miniphase's Avatar

3 metre slope and thermal wing

I started thinking about a larger wing last year https://www.rcgroups.com/forums/show....php?t=1480107 but hit a patch of indecision and diy mayhem, but now's the time to revive the project.

I want to use the model on the slope and off the flat, so I'll be running with the MH45 section. I've used it in the past with mixed results, but learnt much since my early wings and feel it will serve me well on this design

my attachments keep disappearing for some reason...will try uploading them again in a few hours time
Last edited by miniphase; Jan 19, 2012 at 06:52 AM. Reason: attachement issues
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Jan 19, 2012, 05:22 AM
You know nothing....
Stuart A's Avatar
Foam cutting and setups for such are one of those subjects that always seem to raise a lot of debate when mentioned(ANOTHER one on scratch built edfs right now)So, no Q's,but lots of pics would be welcome.
Jan 19, 2012, 05:35 AM
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miniphase's Avatar
Hi Stuart

I will take plenty of fotos and feel free to fire away with any questions as we go along. It took me a long time to get consistent cores (lots of trial and error before the internet) and it was frustrating getting at best a 50% hit rate. Now with a few simple bits of knowledge I rarely ruin a cut, so I'm more than happy to pass on anything that may be of help.

Jan 19, 2012, 07:54 AM
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Vernon Hunt's Avatar

It's good to see you back on this wing idea. I'll be watching the progress.

Jan 19, 2012, 08:12 AM
Deniable plausibility
Shedofdread's Avatar
Mmmm... interesting. May one enquire what the theory behind the elevon shape is? Is it to deliberately make the tip 'draggy' to give a proverse yaw?

Jan 19, 2012, 08:27 AM
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miniphase's Avatar
Hi Shed

If I have to dial in a bit of reflex for level flight, then the taper will give an approximation of washout with more up at the tips than inboard (therfore being less draggy).

I've also found the deeper elevon chord gives better roll response, and I'm sure I read somewhere that it's more efficient to move a large surface a little rather than a little surface a lot. This was evident out on a smaller wing I built with the MH45, I had quite narrow control surfaces, and when I increased the throw to get a better roll rate, the wing would stall out and exhibit the 'zagi death spiral' at full roll input.

Jan 19, 2012, 08:33 AM
Deniable plausibility
Shedofdread's Avatar
Makes sense - I ask because I've done a little Xfoil work on profiles and found there to be an optimum location (%chord) for the flap hinge point. I suppose though that with the elegance of the tailless layout comes other compromises...?
Jan 19, 2012, 08:47 AM
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miniphase's Avatar
do mosts section have an optimum hinge line at 25%? I tend to feel that I'd rather have more aileron 'bite' and less death spiralling as a priority....I tend to follow my nose rather than crunch numbers
Jan 19, 2012, 09:13 AM
Deniable plausibility
Shedofdread's Avatar
Originally Posted by miniphase
do mosts section have an optimum hinge line at 25%? I tend to feel that I'd rather have more aileron 'bite' and less death spiralling as a priority....I tend to follow my nose rather than crunch numbers
Can't say. What I do know is that the two sections I've designed and flown have used 27 and 30 %. Mh32 uses 22%, can't remember what the HQ ones use.

Hmmm... "death spiraling" - can imagine you'd want to avoid that one...

On a serious note, the cruching of numbers has become so very much quicker of late (with Xflr et all) that with the cost of building our 'toys', it is [IMO] almost like a 'due diligence' check.
Jan 19, 2012, 10:47 AM
less is more
Knoll53's Avatar
Miniphase: I see what you mean by moving the inner flap outboard a few mm In this configuration, I'd expect that that surface would act like a flap on a conventional wing, that is near neutral in pitch. Is that your goal with this placement?

The carbon spar and D tube should be killer for flutter control. You'll need at this size. Having a plane that can handle very high speeds at the slopes is 100 times more fun.

I hope we see lots of build pics. I'm still far from 100% with my homemade foam cutter.

BTW, love your fuselage Very sleek.

I'm already jealous.

Jan 19, 2012, 11:20 AM
Retired CAD guy
birdofplay's Avatar

I was subscribed to your previous thread,
and now to this one. :-)

Go for it,

Jan 19, 2012, 11:26 AM
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miniphase's Avatar
Kent, I'll run with a carbon spar in the first instance. I'll fly the wing sheeted (but not covered) and then beef it up if needs be from there.

Yes the flaps should be pitch neutral, this will give me an extra kick of lift when thermalling and slow me down enough for those hand catches

I'm not sure of the fuz will end so sleek, I'm thinking a couple of ply cheeks that I can put a electric motor setup between (for flat field work). Maybe I'll have a lipo and esc on board all the time and have a motor that mounts on the back, in which case the pod will be thicker and will end just ahead of the cg

Shed, I'm sure I'll get round to learning Xlfr at some point, I can see the benefits of tweaking a design before the build starts...in the mean time let's cut foam!
Jan 19, 2012, 11:41 AM
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miniphase's Avatar
I'm by no means a foam cutting expert, but here's how I approach things.

I've got some right angle templates that allow me to cut two sheets of 50mm foam at once so I start off cutting the blanks I need, and by doing this from one sheet on top of another, it ensures you have identical sets of blanks for each wing.

I put the foam sheets on top of some ply or plaster board and screw the templates on to the foam. This gives me 10mm or so of template sticking below the bottom surface of the foam.

I can then run my cutter down the straight edge and not worry if I come to the bottom at one end quicker than the other...I'll still end up with nice square edges.
Jan 19, 2012, 11:50 AM
the answer 42 is
Cool Paul, nice to see you up and running, I am actually starting a build as well but a small "park flyer" EPP wing :P

God speed


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