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Hybrid 60" Plank


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Very nice work; it looks like a Gulp so should fly very well (straight LE planks always seem to turn like demons). I'm not so sure about a 3d printed fus on an EPP wing though - a model like this is likely to take a lot of hits (S.L.O.P.E = Smashed, lost or pulverised, eventuall!), but PLA is rather brittle, especially in the cold. 

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Thanks MattyB, yes we thought the 3D print would be too fragile too, but the first one outlived its wing(!). 

The fus is quite short and has 5-10% infill (circa 250g) so is surprisingly robust. The sheath nose is fragile and cracked after a very fast impact, but was easily super-glued back together. A friend has a 3D printed spit - and it is fragile. This is very tough in comparison.

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  • 1 year later...
Posted (edited)

So after a year of abuse and circa 150 flights or  so, the nose finally gave up it's attachment to the  rest of the fuselage 😮

 

image.thumb.png.414e88a876a1194ada141d66ad8583ed.png

 

It did have some pretty rough landings and the fastest I flew it in was 50mph gusting  60 with full ballast - main problem was me misjudging how far blown back it got, or deciding not to risk going round again and landing with quite a thump.

 

Things I liked:

 -  quick build and very cheap (I was try to see how cheap i could make it 😮 )

 -  wing is very tough

 -  it's light (800g) with no ballast so will fly in 8mph or so

 -  the top and bottom one-piece spars from Decathlon gave it lots of strength and stiffness

 -  given it's speed range it got taken up every Sunday 🙂 

 

Thinks I didn't like:

 -  wing looks very tatty as laminating film does not shrink well after EPS has been bashed

 -  the correx ailerons were perhaps penny-pinching cheapness carried too far(!) should of gone for reinforced balsa

 -  has yaw jitter, maybe due to short tail moment and non aerofoil  fin

 -  needs good ballast to roll quickly (or perhaps stiffer ailerons)

 -  no place for switch 

 -  nose coming off 🙂

 

 

Edited by Mike Chantler
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So plan is put holes through underside of fuselage to take a second ballast tube (and maybe do away with the wing tube if I build a second wing)

 

image.thumb.png.7d3258870904cc205666889e58880900.png

 

A lightweight carbon tube that will take 15mm slugs will fit quite far back - but main reason for fitting it is to give

strength.

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Posted (edited)

Taped old wing back and balanced at 860g which is still pretty light. All my fine ideas about refurbishing the wing, redoing the decoration etc, went out the window in the excitement of having it out again lol(!)

 

Suspect that if I used carbon/balsa ailerons the weight would shoot up quite considerably as they are way behind the CoG as is usual with a plank. However, I'm already thinking that it would be more fun if it was more streamlined and had stiffer aileron things at the expense of weight. I have cut a couple of PW51 wings to same planform and so these may go on next incarnation 🙂

 

image.thumb.png.811b98c4720b45c31a14673dfa52c380.png w

 

Tail now 60mm further back so will see if this helps the yaw jitter. The linkages could definitely be lowered a couple of holes and fairings added.

 

But very pleased with how quickly the whole thing printed and how easy it was to put together 🙂

 

We have a low going through tomorrow so may not get it up the hill for a while.

 

 

Edited by Mike Chantler
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  • 2 weeks later...

Did manage to get into the hills last Sunday - and it flew well in moderate winds with 1/3 ballast. I forgot about looking for the tail jitter, but as I didn't notice it perhaps moving the fin back has fixed it 🙂 It could do with being a little faster - it's faster than a 45" Wildthing, perhaps slightly slower than a Gulp, and definitely looks slower than a couple of streamlined moths that were up. Wing is quite tatty now - so servo covers and tidy might speed it up a bit and have cut PW51 wing for it which I may fit in a while 🙂 

 

One thing I did like was, despite the fact I like building,  was just fitting the 3D print parts together - nice simple assembly when work is eating up your evenings 🙂 🙂 

 

 

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