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Author Topic: Slingsby T.31 Tandem Tutor 1:20  (Read 3416 times)
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Yak 52
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« on: September 27, 2014, 05:51:36 AM »

I've been working on a new indoor scale glider, a Slingsby T.31 Tandem Tutor. 1:20 scale gives a wing span of 26".
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dputt7
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« Reply #1 on: September 27, 2014, 06:23:19 AM »

  Looks really nice Jon, neat set of plans as well.
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OZPAF
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« Reply #2 on: September 27, 2014, 10:52:33 AM »

I really like that rear 3/4 view Jon. If only the kids I teach could produce joints like that ;DEven the teacher has trouble as well Grin
Typical of your neat work.
John
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Yak 52
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« Reply #3 on: September 27, 2014, 11:24:02 AM »

Thanks Dave, John.

Fuselage is more or less complete. The bones weigh just under 10g which is too much! But the structure is near scale and I've not been trying very hard with the weight so I'm not surprised   Undecided
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Yak 52
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« Reply #4 on: December 03, 2014, 07:04:21 AM »

Some progress with the covering...
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dputt7
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« Reply #5 on: December 03, 2014, 07:20:23 AM »

Smoooooth Grin   Neat construction always pays off when its time to cover.
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DavidJP
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« Reply #6 on: December 03, 2014, 09:11:02 AM »

Well, it is very nice!

Bearing in mind I am naive on the indoor stuff, is it the case that eight - or rather the lack it - is crucial.  Way back when I did a bit of thermal soaring sometimes we added  "ballast" in certain conditions, but of course that was outside. For indoor then it is a case of building as light as you can?

I have the Aerographics drawing for the Kadet/Tutor. Yes the construction is a bit beefy here and there and I will make some modifications, but generally it is a case that you build as light as you can?



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Yak 52
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« Reply #7 on: December 03, 2014, 11:00:15 AM »

Thanks chaps.

David, very much so indoors: the lightest possible (consistent with strength/durability of course)
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TimWescott
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« Reply #8 on: December 03, 2014, 04:30:32 PM »

I just learned something new today.  I never had a clue that people did indoor towline glider -- at least, I assume it's towline.  I'm still trying to decide if it's totally nuts, totally cool, or both.
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DavidJP
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« Reply #9 on: December 03, 2014, 05:01:26 PM »

Tim, it seems just about every form of launching is being tried - this quite new by the way -  tow, bungee, hand launched from balcony and aero tow.  All with varying degrees of success I gather.  Things are however very much under development!  It is catching on!

Yak, thank you.  As you will know the plan shows the Tutor and the Kadet, the latter is a clipped wing version. I prefer the tapered wing of the Tutor but wondered if the aspect ratio of the Kadet might work better. The wing area is probably about the same.  Or have I simply lost the plot?
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OZPAF
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« Reply #10 on: December 03, 2014, 06:58:24 PM »

Not even a tiny wrinkle in the wing covering Jon. Shame Cheesy Really nice. The scale structure looks great.

John
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Prosper
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« Reply #11 on: December 04, 2014, 10:18:25 AM »

I agree - your usual standard of flawlessness. Nice subject too. That, or a Kadet, was the first glider I went up in. I wouldn't be surprised if your model exceeds the flight times I got in the full-size!

Stephen.
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Mark Braunlich
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« Reply #12 on: December 04, 2014, 10:54:36 AM »

I had a ride in this one once upon a time.  T'was a great experience.
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Mark
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« Reply #13 on: December 04, 2014, 05:38:31 PM »

Jon,
That is truly beautiful in concept and construction.  Devilment makes me want to ask if all those diagonals are so that you can fit a rubber  motor later but you even forestalled that by pointing out that the construction follows the full size.  As you hold all the aces I shall retire mortified and envious.
John
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John Barker UK - Will be missed by all that knew him.
Yak 52
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« Reply #14 on: December 05, 2014, 01:12:15 PM »

Thanks gents.

David, its true that low aspect ratio is a good thing for outdoor bungee launched gliders. The thinking is that it makes the most of the fixed launch energy of a bungee limited by the rules and gives good launch heights. However indoors the height is fixed by the ceiling and there are no restrictions on how you launch. Instead you need to focus on a good glide ratio, ie a nice flat long glide. This will look more scale-like for the judges. Higher aspect ratio and a lower span loading will help achieve this but also good (thin) airfoils and low parasite drag (struts, wires etc) are also important. There is a balance to be struck because high aspect ratio also means a small chord and therefore more drag from low Reynolds numbers.

I think Pete Smart has shown the way with a very light model, thin single surface airfoils and a moderate to high aspect ratio. His models fly at scale speed due to low wingloading but the glide angle is good due to low span loading and low drag.
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Russ Lister
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« Reply #15 on: December 05, 2014, 01:28:08 PM »

Looks great Jon!  Smiley

Hope to get my new launch system finished for the next Bushfield ..... they'll be queuing up for my "Lister's Glide-O-Riser"!  Tongue
(Patent appled for) ...... hope it works now I've let this cat out of the bag ......
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DavidJP
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« Reply #16 on: December 05, 2014, 05:04:57 PM »

Thank you Jon.

It does seem in some respects it is six of one and half a dozen of the other?! I am swayed by the nice lines of the long wing as the other is a bit "Kolditz"!
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Yak 52
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« Reply #17 on: December 05, 2014, 05:52:42 PM »

Cheers Russ, intriguing  Grin

David, I would expect the extra span to help, especially if there's no increase in wing loading and if the airfoils aren't too fat  Smiley
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Monz
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« Reply #18 on: December 05, 2014, 06:22:47 PM »

Thank you Jon.

It does seem in some respects it is six of one and half a dozen of the other?! I am swayed by the nice lines of the long wing as the other is a bit "Kolditz"!

You were there for Andy's talk at Impington right? Wink
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Yak 52
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« Reply #19 on: December 05, 2014, 07:00:30 PM »

I wasn't, but I've heard him give it elsewhere... Did I miss something this time?  Smiley
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Monz
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« Reply #20 on: December 05, 2014, 07:16:02 PM »

I wasn't, but I've heard him give it elsewhere... Did I miss something this time?  Smiley

I quoted David, Jon, not you Wink
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Yak 52
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« Reply #21 on: December 05, 2014, 08:42:34 PM »

Oh sorry...
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DavidJP
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« Reply #22 on: December 06, 2014, 08:18:02 AM »

Thank you Jon.

It does seem in some respects it is six of one and half a dozen of the other?! I am swayed by the nice lines of the long wing as the other is a bit "Kolditz"!

You were there for Andy's talk at Impington right? Wink

Yes M'am but I get a bit bewildered now and again being of advanced years and of a nervous disposition! Huh  Shocked

I am already formulating a few notions but will keep them to myself for the moment. But I had not appreciated that there is a very marked difference between indoor technology and "out" I suppose because I have never had to think about it! I am still at the bottom of the learning curve. 
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Russ Lister
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« Reply #23 on: December 06, 2014, 03:50:23 PM »

David,
With talk of Impington .... annoyed that I did not realise that you were there. Usually quite good at recognising people .... not saying that you have a forgettable face!  Roll Eyes
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DavidJP
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« Reply #24 on: December 06, 2014, 05:26:31 PM »

Yeah -well last time you took my photo, lounging about! Don't like my photo took Huh Wink

Sorry Jon.

As a guide please what does your T31 weigh please? I am intending to concentrate on the weight issue, which I have never really done before and  I feel I need a yardstick of some sort. The T31 looks pretty similar.

Reading Charlie Newman's article in the latest Aermodeller some of the weights achieved are daunting. For example Peter Smart's Wren weighs 5gms at 20 ins span!
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