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1/5 Scale Slingsby T51 Dart 17.

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John Vella
Posts: 231
Joined: 20 Mar 2017, 22:09
Location: UK

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by John Vella »

Brian, I wouldn't be concerned over the smallish tailplane on the Dart as it does have a long moment arm. The full size flew okay. I would be more concerned on keeping the back end of the Dart as light as possible for begnine handling. Regards John.

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B Sharp
Posts: 702
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp »

John, the reason that I am so concerned about the tailplane area is that the fuselage of this model is shorter than scale as was discussed way back in the first couple of posts on this thread. On my 1:3.5 version, which has a scale length, I had a tailplane half fall off in flight and still remained controllable. Knowing that the fuselage is shorter on this model I designed the tail to be 10% larger to give me a little margin of safety.
Brian. :)

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Peter Balcombe
Posts: 1041
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by Peter Balcombe »

Brian,
The Dart15 version flies well with the original size tailplane which was solid balsa in Pat’s original kit, but made as semi-open structure in the later design to reduce nose ballast & overall weight.
The extra 10% tail area you added should be fine, even with the increased span.
Peter

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B Sharp
Posts: 702
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp »

Peter, I didn't recieve any plans for a tailplane so I checked drawings and also my 1:3.5 unit and calculated a 1.5 tailplane. I then increased the volume by 10% as a rough guess. It still looks small by comparison to the wing area, but that's a Dart trait. As I said earlier my big one flew on 1/2 tailplane so If I have any major problems I can make a slightly enlarged version.
Brian. :)

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Peter Balcombe
Posts: 1041
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by Peter Balcombe »

Sorry Brian,
I now recall that when I remodelled my Dart15 tail feathers, I took the original tailplane half planform & knocked up an equivalent with what looks like a solid front (covering both joiners) with a few rear riblets to simulate the full size open rear structure.
I never got around to putting the tailplane detail down on paper, so the built up plan only covered the wing.
Each tailplane half is 275mm long, Root chord approx. 125mm, tip chord approx. 97mm
The pic below gives an idea of the internal structure.
Peter
Attachments
65CEFC26-8536-4B15-B8F6-59A065294872.jpeg

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B Sharp
Posts: 702
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp »

Peter, Your tailplane construction looks almost identical to mine although the area of mine is fractionally less than yours. It looks as though "Great minds think alike". (We will now wait for the usual response to that last comment from any number of the usual people !)
Today has been spent doing "Life" things but I will get down to work soldering up the wiring harness after tea.
Brian. :D :D :D

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B Sharp
Posts: 702
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp »

I now have two completed and covered wing halves. The wiring has been completed with Mpx plugs and sockets and the Mpx wing retainers have also been fitted in the wing roots.
The thin wing servos have been glued into the servo bays in the wings and the ailerons fitted and hinged with “Sylglas” tape. The aileron pushrods are so short that it proved a bit of a problem to make them adjustable. I usually fit two metal clevises back to back on a threaded rod however there was no room to do this on the dart. You will be able to see from the photos how I resolved the problem.
The fuselage is also nearing completion. All the radio gear is now in place with the exception of the battery and the wheel has been fitted. The battery will be fitted once I start balancing.
I am now fast approaching the point when I will have to assemble the component parts and work out the C of G. The default position will be just forward of the spar but I will use a CG calculator to find the range of settings that I want.
Brian. :)
Attachments
The competed wings.
The competed wings.
Wing root with wiring and retainer.
Wing root with wiring and retainer.
Wing servo fitting.
Wing servo fitting.
Completed aileron set-up.
Completed aileron set-up.
Almost complete fuselage.
Almost complete fuselage.

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B Sharp
Posts: 702
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp »

I have just done the CofG calks and they are very interesting (to me at any rate).
The set of drawings which Clive has recently sent me show the CofG at 57 mm back from the leading edge of the wing.
My first calculation with the static margin set at 15% (safe) has the CofG at 53mm back from the leading edge.
With the static margin re-set at 10% (which is where I will likely end up after a couple of trimming flights) the CofG comes in at 61mm from the leading edge. This gives the recommended 57mm a calculated static margin of 12.7% - not unreasonable at all under the circumstances.
It looks like I will add lead to the nose till I get 57mm then work backwards from there towards 61mm.
Brian. :D

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by Peter Balcombe »

All looks very nice Brian :)
I look forward to hearing of the successful maiden flight.

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B Sharp
Posts: 702
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp »

Thanks Peter. However, the way the weather is shaping up at the moment it may be some time before I get the Dart in the air.
Brian :)

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