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Old Sep 13, 2012, 01:52 PM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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So many questions on this thing.
Since Mark mentioned the MH45 foil a while ago I've done a bit of reading about it and the CO 5 wing.So-
1-would the twist be ok as the .CO5 design-I think he has 5-6* starting 1/2 along the wing-would the lack of tip fins on the Leaf mean an adjustment.
2-bearing in mind the above is there an optimum aspect ratio.If I settle on a 2m span,the centre at approximately 300mm would leave 850mm for each panel.
3-a more practical one.I'm presuming a foam wing,carbon tows to reinforce and either balsa,ply or glass,whatever you guys recommend.
In that case,what would be the best way to(possibly permanently) get a fix onto the root.I would like to resolve this so I can have a go at inserting what is necessary into the trial wing root and adjust the arc slot position accordingly.All leading I hope to a finalised drawing of the centre section mechanism.
Regards Stuart.
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Old Sep 13, 2012, 02:14 PM
Deniable plausibility
Shedofdread's Avatar
Derbyshire, UK
Joined Aug 2008
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Re the foam - look for 'square cut' or 'pin holed'. Can't help more ATM - building emergency.
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Old Sep 13, 2012, 02:55 PM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Quote:
Originally Posted by Shedofdread View Post
Re the foam - look for 'square cut' or 'pin holed'. Can't help more ATM - building emergency.
Thanks ,hope it's nothing too serious
Regards Stuart
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Old Sep 13, 2012, 04:04 PM
Herk
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Virginia USA
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Hello Stuart -- Since you are asking for more advice You know that it's worth every euro (or quid) that you are paying for it

I think we are going to need a somewhat more concrete layout before the advice will mean much. For example; If you are going to have complete control of the wing trailing edge - as in the layout of your test glider - the airfoil choice will be affected.

Also, some taper would mean that you won't have such a big awkward tip to deal with when the sweep gets toward the larger numbers.

Likewise, starting your sweep at about 20 degrees means that CofG shift is a small matter. On the other hand if you want to use "plank" as the starting point, it will indeed have to be dealt with.

In other words, you've worked out a lot of detail about the mechanism, - so what I'm saying is that the airfoil and other matters depend now a lot upon the more complete layout that you expect to start with.
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Old Sep 13, 2012, 04:20 PM
less is more
Knoll53's Avatar
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Golly, that Herk guy has got some good ideas.

Also, I'd suggest modifying the root area airfoils to 15% thick for no other reason than to increase working room and strength. You can taper down to normal thickness at 1/3rd of the way out on the halfspan.

Kent
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Old Sep 13, 2012, 05:35 PM
I don't like your altitude
Stupot46's Avatar
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Quote:
Originally Posted by Knoll53 View Post
Golly, that Herk guy has got some good ideas.

Also, I'd suggest modifying the root area airfoils to 15% thick for no other reason than to increase working room and strength. You can taper down to normal thickness at 1/3rd of the way out on the halfspan.

Kent
You took the words out of my mouth Kent.Cuts to the heart of the matter.Never mind euros,Herks advice is priceless.
And you have just answered the real point of the post that Herks replied to.
Which is how deep can I make the root.If 15% is used that will give me 21mm.
As the drawing stands the root chord is the same as the disc diameter,I think I can increase this.A bit late tonight,I'll post a sketch tomorrow.
As Herks says I need to make a decision on the amount of sweep.I'd like to try 15-40*,but if 20-45 would be more practical I'll go with that.
Regards to both Stuart
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Old Sep 14, 2012, 01:35 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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A sketch showing the root chord stretched to 180mm from 140mm.
The two other pics are from Verns Colibri thread,which I was impressed with when he first posted them.Seems a good method with a foam wing.The last pic is the ideas of Martin Lichte that Kent posted.Maybe a combination of these two?
Always in the back of my mind on this idea has been fairing the wing root into the centre,I think I have something in mind that could work for the l/e,but the trailing edge will be fun.
Regards Stuart
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Old Sep 14, 2012, 12:02 PM
less is more
Knoll53's Avatar
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Quote:
I had a thought about these (keyring size)cameras since Mark mentioned them.Along with a couple of small LEDs they would be a brilliant way to monitor the workings of the Leaf on a maiden flight.
Stuart
Are you thinking of putting a camera inside of the wing with lights to film the wing sweep motion in flight?

Kent
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Old Sep 14, 2012, 12:37 PM
I don't like your altitude
Stupot46's Avatar
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Quote:
Originally Posted by Knoll53 View Post
Are you thinking of putting a camera inside of the wing with lights to film the wing sweep motion in flight?

Kent
If it's gets that far I think it would really good to be able to see what's happening during flight.Should be able to monitor the integrity of the hinge system and drive,maybe spot any weakness before it leads to a failure.That could be done with fpv?
Regards Stuart
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Old Sep 15, 2012, 02:43 AM
I don't like your altitude
Stupot46's Avatar
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Following Herks advice on using a tapered wing,I revisited Verns Colibri and used his dimensions to come up with a possible planform.
The drawing shows the wings at 15 and 45*,also a possible outline of the centre section.

The drawing is to scale,the dimensions are-
Panel length-850mm- this from the outer edge of the disc
Root chord. -180mm-from the same point
Tip chord. -60mm
If my maths are correct this gives a wing area of 2.04sqm
The two root discs@140mm plus a 20mm spacing(this provisional,I'll put up a drawing of the drive mechanism later)gives a total straight span of 2m.
Although the final all up weight cannot be even estimated at present,my gut reaction is that this is too small.A larger wing area would not lead to a great increase in the central drive and wing roots.
This would mean detachable wings,probably best done at the transition from the 15% that Kent suggested to the "normal" airfoil.
Am I getting closer to a viable wing with this?
Regards Stuart
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Old Sep 15, 2012, 07:02 AM
Herk
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Virginia USA
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Stuart - I'll have some fun looking at this today. I have a few questions and a comment just off cuff.

1. Is this plane intended to be flown from a slope - or perhaps a hi-start launch or is it to be e-powered?

2. From the dimensions you mentioned it appears that the pivot point is to be 70mm into the wing panel, measured from the circular inboard edge of the panel - is this correct?

3. I'm assuming that this craft is to be flown without fins - please confirm.

My comment is that it's likely the weight of the center structure will be such that the model will be quite nose heavy. You will likely need to extend the structure aft a bit so that the weight of the working bits is centered well behind the pivot points.
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Old Sep 15, 2012, 08:27 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Herks,As usual thought provoking comments.
I must admit I have given too much thought to the actual flying aspect,my main concern has been a viable mechanism in a rigid structure.The aerodynamic aspects(not my strong point)have only come into consideration as I need to finalise the design.
I had presumed an unpowered bungee launch; your final comment may make a pusher prop helpful.
The 70mm is correct.
No fin,though I had thought about a temporary central one for proving flights.
Re your final comment,I'll do a 3 view drawing of my latest ideas for the drive;siting the motor as far to the rear as possible will help.
I will be interested in your ideas about the span/wing area.
Regards Stuart
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Old Sep 15, 2012, 11:37 AM
Herk
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Virginia USA
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Stuart - took a quick look at your layout full size.

Check your math on area - I get a bit over two tenths of a square meter. ~400 square inches.

The tip is pretty tiny. If you want to put any mechanics in the outer part of the wing it may be a bit too thin to work with.

More later -- Herk
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Old Sep 15, 2012, 12:02 PM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Quote:
Originally Posted by HerkS View Post
Stuart - took a quick look at your layout full size.

Check your math on area - I get a bit over two tenths of a square meter. ~400 square inches.

The tip is pretty tiny. If you want to put any mechanics in the outer part of the wing it may be a bit too thin to work with.

More later -- Herk
Definitely not paying attention on that one.204mDecimal place
Stuart
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Old Sep 15, 2012, 01:40 PM
Deniable plausibility
Shedofdread's Avatar
Derbyshire, UK
Joined Aug 2008
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Stuart,
I can't comment on the overall design (sorry, not been paying enough attention) but I would also caution against that really small tip chord. At chords that low, behaviour isn't predictable. To be safe, treat 120(ish)mm as a practical minimum. The last 10% of the semi span can go less but if you stick to 120ish, 10% in from the tip, there'll be less probs.
Richard
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