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Boxing Clever

A micro aerobat to fit into a box!

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Tim Hooper04/01/2015 21:25:45
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2899 forum posts
2406 photos

The brief is to create a viable RC model that can be drawn on two A3 sheets of paper. Obviously I have no idea what this design is to be used for. Mine is not to reason why, etc........

Using graph paper I sketched a reduced-size plan to get an idea of the proportions.

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That done I set about sourcing the hardware, and gained this little lot....

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There's a 10 gramme 2000 kv motor, a 4x4 prop, 4 x 3.5 gramme servos, micro rx and 10A ESC.

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Here's the wing drawn full-size. A massive 22" span! The orange card contains the Profili printouts, using an E207 semi-symmetrical aerofoil. The lower wing skin is from 1/32 balsa.

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The lower skins, spars and ribs in place - all done with thin CA glue. The tips are raised to give 1/4" dihedral, and then the central joiner tubes are fitted. There's a central 3mm cf rod.

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Beneath the rod are two protruding 1/32 ply plates which will pass through the fusealge sides. These will be linked with a clip to prevent the wngs coming adrift in flight!

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The fronts of the lower skins are raised with tapered balsa wedges, prior to fitting the 1/4 leading edges.

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So far, so good....... wink 2

Chris Bott - Moderator04/01/2015 21:32:59
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6837 forum posts
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Already looks fascinating Tim thumbs up

WolstonFlyer04/01/2015 21:37:58
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2104 forum posts
189 photos

Very interesting, who set you the challenge?

Tim Hooper04/01/2015 21:55:11
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2899 forum posts
2406 photos
Posted by WolstonFlyer on 04/01/2015 21:37:58:

Very interesting, who set you the challenge?

That must remain a closely guarded secret. Let's just say the edict originated in South Essex......

All the gear weighs in at 96 grammes, leaving around 60 grammes for the airframe.

tim

ken anderson.05/01/2015 09:37:00
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8686 forum posts
808 photos

happy new year Tim to yourself and your good lady......see you pushing the boundaries again.....well done - look forward to seeing the completed model....

ken Anderson...ne....1..... TH fan club...dept.

Vecchio Austriaco05/01/2015 09:57:48
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1498 forum posts
715 photos

Hi and Happy New Year.

Looks very interesting.

Why do you have 4 servos in your hardware-pot - are you planning to use 2 servos for the ailerons?

Looking at the size of the plane the wing will be quite thin I suppose. Are you positioning them in the fuselage?

VA

IanN05/01/2015 10:11:45
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1675 forum posts
119 photos

Very interesting. Two piece wing, eh? That's an unusual complexity on a model this size - presumably to facilitate the "fit in a box" aspect?

Colin Hooper05/01/2015 10:32:51
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47 forum posts
21 photos

This looks like a holiday special. Small enough to hide in a suitcase and still have room for clothes. I could be interested!

trebor05/01/2015 10:58:50
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1930 forum posts
216 photos

Hope you don't mind me watching, I might learn something here !

Simon Chaddock05/01/2015 13:19:09
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5717 forum posts
3034 photos

Tim

Beautiful work.

What size is the 2s battery?

I presume your target is a 160g (6 oz) all up weight?

I have a sneaking suspicion that at 22" span you wont need ailerons that big. wink 2

At these extreme small sizes is an 'exact' aerofoil actually going to make much difference?

I my experience anything much below 3" chord is so relatively inefficient (Reynolds number?) that its thickness becomes the dominating factor rather than its section in determining the 'power to fly'. It almost becomes a "thinner the better" scenario hence the remarkable performance that can be achieved by a flat plate wing.

I will watch with interest.

Martian05/01/2015 13:35:56
2529 forum posts
1163 photos

watching Tim and Happy New Year

Martyn K05/01/2015 16:40:53
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5085 forum posts
3678 photos

I'll build one of those Tim.. Looks great - or do you want to start a free for all and we all do our own variant to the 2 sheets of A3 rule?

Subscribing

M

Tim Hooper05/01/2015 21:50:09
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2899 forum posts
2406 photos

Thanks all! smile

Vecchio, yes there's two aileron servos - one in each wing, which sort of answers Simon's comment about the inefficiency of such a time wing section - the wings are just there to hide the internal servos!

I have several 3S 450 packs in stock, so I'd like to utilise those if possible. If they're too heavy then I'll shell out for a smaller pack.

tim

Tim Hooper07/01/2015 21:26:46
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2899 forum posts
2406 photos

Here I've installed the tape-wrapped 3.5 gramme servos, using thin CA. Not an ideal way of doing things, but certainly the lightest!

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The servfo arms will emerge from their bays when the rx is connected and powered up.

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With the tops of the wings sanded to remove any high spots, the 1/32" tp skins are added and pinned overnight to let the PVA glue dry.

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The leading edges are radiussed and sanded smooth. I opted to fit 1/32 sheet facings over the root ribs - just to hide the exposed ends of the spars. Each panel weighs in at 21 grammes.

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The tail surfaces are cut from light 1/16 sheet, with crossgrain end pieces to prevent warping, The elevator joiner is a length of wooden cocktail stick.

Just for fun I've built a little canaliser too.....

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Vecchio Austriaco07/01/2015 21:53:11
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1498 forum posts
715 photos

looks very nice. Wonder how it will fly. My experience with very small planes is that they are rather difficult to control (for instance Multiplex Fox conversion) - but probably yours has the right size to weight ratio.

Looking forward to maiden flight

VA

Nev07/01/2015 22:06:35
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592 forum posts
221 photos

This looks fun, how big is the box ?

Can't fit in a shoe box surely, will have to make one though.

Alan Randall07/01/2015 22:36:34
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446 forum posts
108 photos

Just needs a nice carrying case to go with it Tim.

Tim Hooper07/01/2015 23:04:53
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2899 forum posts
2406 photos

Vecchio, Netty and I have been flying a pair of Hitec Zippers. These little 24" ARTFs are certainly quite rapid, but quite smooth in flight. The ailerons are positive, but not ridiculously so. The elevator does need to be treated with respect though!

You're quite right lads - I'll need to make a custom box.

tim

IanN07/01/2015 23:33:46
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1675 forum posts
119 photos

Blimey, the modelling pins alone will cost more than the build and fit out - I've never used even remotely that many on wings several times the size.  You must have needed a truckload for that 80" Quad laugh

On reflection, that could of course quite probably be where I've been going wrong all these years enlightened

Following this with interest

 

Edited By IanN on 07/01/2015 23:37:01

Edited By IanN on 07/01/2015 23:45:17

cymaz08/01/2015 06:57:35
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9255 forum posts
1196 photos

Just a thought, it might have a detachable tail section. That way it could sit in a suitcase or hand luggage.

Plane for going on Hols with ??

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