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Slingsby T.50 Skylark 4

Posted: 12 Aug 2018, 13:14
by B Sharp
I felt that I was in dire need of a new balsa bashing session and was looking around for a subject I hadn’t tackled before. I wasn’t up for a large and heavy model at present; something around 4 metres and under 6 kilos, but still large enough for a good performance. I chanced upon a 1:5 scale model of the Skylark 4 by Mike Trew which seemed to fit the bill. I also decided to do this build log as I hadn’t done one for a while and I find that it helps me keep the build moving along.
Having received the plans I decided to make a few changes (as usual). These plans were drawn nearly 30 years ago and radio and techniques have moved on since then. Mike used a wing section which is not unlike the full size NACA63-620 which works out at 22% thick on the plan. I felt that using this would give a fairly narrow performance envelope so I am changing it to HQ3.5/16 at the root transitioning to HQ3.5/14 on the centre section. The tips will transition further to HQ2.5/12 at the wing tip. I will modify the wing hold-down arrangement and use Chris William’s sliding square tube method for actuating the elevator. The ailerons will have servos way out on the tip panels rather than long pushrods and bellcranks and I will install electric brakes for simplicity.
I have even picked possible schemes for the finished model and they should appear below.
Brian. :) :) :)

Re: Slingsby T.50 Skylark 4

Posted: 12 Aug 2018, 13:25
by Jolly Roger
How exciting Brian. I'll follow with interest.

I'll also photograph any Skylark 4's that turn up for Slingsby Week at the Yorkshire Gliding Club at the end of the month. Let me know if there's any specific close-ups you'd like.

Rog

Re: Slingsby T.50 Skylark 4

Posted: 12 Aug 2018, 15:04
by B Sharp
Hi Rog.
I don't know that the build is going to be all that exiting but I will do my best to inform and entertain!
Thanks for the offer of pics, the cockpit interior and instrument panel would be good.
Brian. :)

Re: Slingsby T.50 Skylark 4

Posted: 12 Aug 2018, 15:16
by chris williams
These might help, Brian... BTW, Smallpiece has come up with better solution than the sliding tubes. A small letterbox gap on a rear former allows a carbon pushrod through. A ball link on the end of the pushrod allows the elevator actuating pin to be easily inserted and with no unnecessary slop....
Much easier to set up and little fear of binding ;)

Re: Slingsby T.50 Skylark 4

Posted: 12 Aug 2018, 20:45
by B Sharp
Nice one Chris, ta.
Genius solution, but don't tell Smallpiece that!
Brian :)

Re: Slingsby T.50 Skylark 4

Posted: 12 Aug 2018, 20:51
by roo Hawkins
Hi before you start. Sarik vac forming are going to do glass fuselages for the mike trew gliders I have seen the Jantar and asw plus pl all ready. Maybe worth checking to see if they are doing the skylark also. Have a look at the Sarik visit post on this forum. Roohttp://scalesoaring.co.uk/phpBB3/download/file.php?id=12991&sid=d4ed4ec390de521822cb03bda5b902c5&mode=view

Re: Slingsby T.50 Skylark 4

Posted: 13 Aug 2018, 18:51
by Andrew Ray
Interesting Brian. I have the original MT plan for this that I have scaled up to 1/4 scale just because it kills two birds so to speak. I have started a build thread on here that needs updating. I have stuck with the plan wing section. I am looking forward to seeing yours come together.

Re: Slingsby T.50 Skylark 4

Posted: 14 Aug 2018, 17:52
by B Sharp
Thanks for the “heads up” Roo, but I really want to enjoy the build on this one so I will be building the wooden fuselage from the plan. It will take a while but just so long as it is ready to fly next spring.
Thanks for the comments Andrew, we can form a mutual appreciation society.
As tradition dictates (my tradition anyway) I am starting with the tailplane elevator and fin. I find this helps me check out how accurate the plan is and it gets my banana fingers back into the way of working. I didn’t have to look far to find my first inconsistency on the plan. The rib outline for the tailplane centre section was ok but the tip was drawn 11mm too short to fit on the plan view. Ok so we now have to measure everything twice (or even three times) before cutting.
The tailplane and elevators have gone together quite well and weigh not very much. So far so good!
Brian.

Re: Slingsby T.50 Skylark 4

Posted: 15 Aug 2018, 11:00
by RobbieB
Ahhhhhh, the tidiness is breathtaking.................

See you at Leek Brian.

Re: Slingsby T.50 Skylark 4

Posted: 15 Aug 2018, 21:17
by B Sharp
The Skylark build continues (slowly).
I have enjoyed putting the rudder together today. I haven’t had quite so much satisfaction with the fuselage formers. Each former has had to be measured against the plan, adjusted, then the notches for the stringers further adjusted accordingly. F18 and F17 (the funny little ones on the left hand end) took me over two hours to produce. They all have to be measured (twice) before any wood can be cut. Hey Ho, this is real 1980’s building.
No more posts for the next few days as I am heading off to fly toy aeroplanes this weekend.
Brian.