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Author Topic: Slingsby T.31 Tandem Tutor 1:20  (Read 3334 times)
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Prosper
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« Reply #50 on: January 02, 2015, 02:52:49 PM »

Immaculate.

Stephen.
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Rich Moore
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« Reply #51 on: January 02, 2015, 05:01:22 PM »

Hi Jon! Another fine build.
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Yak 52
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« Reply #52 on: January 02, 2015, 06:51:58 PM »

Thanks guys  Smiley

David, the full size tutor has no dihedral (except perhaps while on the winch  Undecided)
This one has about 2.5 degrees. Its not much really but I wanted to try a bit harder to see what was trimmable with this model. It should benefit from the high wing effect with that low slung fuselage. The tailplane is also slightly enlarged but the tail volume is still fairly low (0.45)

The weight will be just under a cube loading of 2 which was my target.
We'll see tomorrow I guess!
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Mark Braunlich
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« Reply #53 on: January 02, 2015, 08:22:43 PM »

Looks great Yak.  Good luck with the flying.

Idea:  make a pitot tube for at least part of the nose weight.
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Mark
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« Reply #54 on: January 03, 2015, 09:25:13 AM »

Thanks Mark, it might happen  Smiley

Well I'm a happy chappy  Grin The tutor flew really nicely today.

The wings had picked up a little warp so I had intended to fly it with rudder opposing this, in the classic 'rudder giving turn vs warp keeping wing up' trim. However there was very little roll coupling and the model just flew along happily crabwise! So I put a trim tab on the wing and left the rudder straight. This worked perfectly with the aileron control setting the turn. This was my lesson for the day - forget the rudder and use ailerons for trimming.

The tow hook was just stuck on to allow me to change its position, but I happened to get it spot on first time. Its a little ahead of the leading edge and slightly offset to the right. The really good news is that the model is totally stable and steerable on the winch line. Pulling harder makes it turn left and slackening off turns it right. The real key to realism is the finesse of the winch handling so I need to practice plenty  Smiley

In spite of the limited dihedral the model is spirally stable. It will recover from a steep turn but this takes a little height and time so the key is getting it off the top of the line in a decent attitude.

Russ helped with the launching and managed to get a few videos, this one on my phone:
http://www.youtube.com/watch?v=jJ6TEOc8erM&feature=youtu.be
Russ got a better flight on his phone.


Jon
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Re: Slingsby T.31 Tandem Tutor 1:20
Re: Slingsby T.31 Tandem Tutor 1:20
« Last Edit: January 03, 2015, 09:36:04 AM by Yak52 » Logged
Balsa Ace
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« Reply #55 on: January 03, 2015, 09:40:31 AM »

Beautiful build,Yak.

Scott
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Pete Fardell
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« Reply #56 on: January 03, 2015, 09:43:47 AM »

Sheer class, Jon! Your expert methodical approach is really looking like paying off. The glider comp is hotting up!
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« Reply #57 on: January 03, 2015, 03:01:27 PM »

Enjoyed it today Jon ... the Slingsby is showing promise.

Here's one of the other videos I took ... I zoomed in on my phone camera a little too much perhaps so the resolution is not so good.

https://www.youtube.com/watch?v=sHHiuNM5N4o&feature=youtu.be
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Yak 52
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« Reply #58 on: January 03, 2015, 03:59:59 PM »

Thanks Scott, Pete.

Thanks for your help Russ Smiley in your vid you can see the model pulling left, me bottling it, and then it going too far right!
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DavidJP
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« Reply #59 on: January 04, 2015, 06:12:54 AM »

Wow!!  That shows a lot of promise.  It just goes to show - issue a challenge and it will be met.  I cannot but think that the "Indoor" glider scene will be taking off! As Pete says.
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« Reply #60 on: January 04, 2015, 03:07:46 PM »

What a thing of beauty. The tissue finish is especially nice.
XE800 and WT901 were the ones I trained to first solo on so even though it is hardly a high performer it is always a special type for me, as for so many former air cadets.

I don't think that couple of degrees of dihedral detracts from its excellent visual impression in any way.

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« Reply #61 on: January 04, 2015, 03:57:44 PM »

Quote
The tissue finish is especially nice.

The tissue markings are on a par with the best that I have ever seen ... or in other words ... they are as good as they get  Smiley
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« Reply #62 on: January 04, 2015, 07:10:23 PM »

That is an outstanding effort Jon. unfortunately i couldn't link to your vids(probably my ol computer) buti bet it flies well. Approx how many oz/ft2 is it flying at?

John
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« Reply #63 on: January 04, 2015, 08:17:07 PM »

Thank you for all the kind words.

John, at 17g the wing loading is 1.41oz/ft2 or 0.28g/in2 in indoor speak.
This gives a cube loading of 2.15.
If anything it could be much lighter!  Embarrassed

The videos are just on youtube? I may have added a mobile link by accident but they should be searchable?
Another brief video has appeared on the PMFC site
http://www.peterboroughmfc.co.uk/Gallery2015/2015-01-BushJon/0_Bushfield_3Jan_Jon.html


I must say that indoor gliding is really addictive  Smiley I'm already planning my next one!
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« Reply #64 on: January 04, 2015, 08:31:56 PM »

Found it and thanks for the link to the pics - it flies very smooth and looks very stable. Yes indoor scale gliders do look fun - a pity about that wall Cheesy I did notice that you  had the tail propped up on its launch steady. Good idea - I remember the few times i tried a ground launch with a RC glider just how quickly it rotated - possibly due to its tail low resting postion.
happy 2015
John
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« Reply #65 on: January 05, 2015, 04:26:59 PM »

Yak52, where you have the colour demarcation between white and red tissue along the fuselage, is that red tissue laid over an existing substrate of white? Or did you pre-join sheets of tissue  along a narrow overlap? And if so, what did you use as an adhesive for the joint?
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Yak 52
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« Reply #66 on: January 05, 2015, 05:30:23 PM »

Yes, its red laid over white. I have joined tissue like that with dope and works ok but I didn't bother this time.

Jon
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« Reply #67 on: January 08, 2015, 04:56:46 AM »

After looking at the flight videos, and also considering a comment Andy S on the day, i think the climb needs 'more welly'. I felt this on the day but was tending to handle the line a bit gingerly to avoid the left pull. I was thinking that a bit more up elevator would help convert speed to height but its just struck me that the hook offset may be too much. It seems the trick is balancing hook offset against tightness of the glide turn induced by aileron.
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Tapio Linkosalo
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« Reply #68 on: January 08, 2015, 05:47:13 AM »

It does not seem to me that there is too much hook offset. Here in Finland we commonly use offset hook in (duration) gliders, especially for juniors (no moving parts required), and in those models the proper amount of offset turns the glider clearly to the left in the start of the flight, only after exceeding 45 degrees tow line angle does the reduced pull forward and increased pull down start to turn the model to the right, and ideally the model ends up just overhead of the tower, slightly banked and heading some 30+ degrees to the right from the towing direction. The hook offset is definitely too much when the model stays on the left and never crosses to the right side of the line between starting point and tower. But indeed, the pull force plays a big role, in stronger wind the towing is more difficult, as the model tends to go more to the left...
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« Reply #69 on: January 08, 2015, 07:17:44 AM »

Thanks Tapio, the model did pull into a left turn a few times, which made me a little hesitant with the winch. I think there is maybe more to be gained by fine adjustment of the aileron tab (for correct glide turn) combined with improving my launching finesse!
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« Reply #70 on: January 08, 2015, 06:02:23 PM »

Jon, I feel that it may be better to actually start moving your hook back a bit to steepen the climb rather than trying to launch it faster. The higher launch speed would make the balance between the offset hook and aileron more critical.
I had a small towline (30") glider that was launched without auto rudder or hook offset.
I had some right rudder balanced by wash in on the right wing and a fairly aft hook position. It was quite controllable and very little right rudder was needed, which gave a large glide turn.
Achieving the balance seemed easier with the slower steeper tow.

John
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« Reply #71 on: January 08, 2015, 06:22:29 PM »

Yes, of course John, I should have thought of that Smiley thanks,

Jon
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« Reply #72 on: January 11, 2015, 02:18:05 PM »

Enjoyed your article for the Peterborough MFC website Jon  Smiley ... are you going to post a link here?
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« Reply #73 on: January 11, 2015, 04:38:02 PM »

Thanks Russ, yeah its here  Smiley :
http://peterboroughmfc.co.uk/membersmodels2015/02-Tandem_Tutor.htm
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« Reply #74 on: January 30, 2015, 09:56:05 AM »

I've been tidings up this model prior to another session tomorrow, replacing the blutack with lead. I've come up with a simple solution: Cut appropriate lengths of 2mm x 2mm 'bar' from lead flashing, squidge them into 2mm 'rod' with pliars and stuff them in a drill hole (yes a 2mm bit Smiley) in the nose block. When final trim is sorted I can cover the holes.

The post-it note trim tab has been replaced with accetate.
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Re: Slingsby T.31 Tandem Tutor 1:20
Re: Slingsby T.31 Tandem Tutor 1:20
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