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Old Nov 05, 2013, 03:44 PM
Registered User
Tadley Hants England
Joined Sep 2002
315 Posts
Help!
Slingsby Skylark 1 own build

I am thinking of building a scale glider a Slingsby Skylark 1 to be precise. Reasons are I have Martin Simmons Slingsby Saleplanes book. I do not want struts as they are fiddly to rig on a cold hill. Also wanted a box fuselage as they are a lot easier and also no splicing of wing spars. Decided on scale of 1:3.182 which makes tip 48” and centre 36” for span of 169” or 4.3m.

Scaling up the fuz and wings is fine, going to use HQ3.5/14 at root thinning to HQ3.5/12 at the tip. Now how do I decide how big to make the spars for the centre panel and the tips. I was thinking of 3/8 x 1 /4) for centre panel and 3/8 x 1/8 for the tips. Ribs will be 1/8 balsa for centre and 1/16 for most of the tip ribs with sheeting 1/16. May do spar with 1/16 balsa sheeting bot sides and but the ribs on or traditional spar and ribs adding sheer webs later. Does that seem reasonable to folks with more experience than me on this? Also I have 18” of 14mm steel joiner and brass would 9” be adequate to join centre panel to tip?

I have Cliff Charlesworth’s book on scale model gliders but it does not help on strength of structure of spars.

There are a few ways to secure the wings, 2 steel bolts and captive nuts, or 4 nylon bolts with captive nuts to give in the case of heavy arrival. Thoughts?
Any help would be appreciated.

Thank you

Alistair
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Old Nov 06, 2013, 01:12 PM
Paul
Slopeangel's Avatar
Mold UK
Joined Apr 2005
123 Posts
Rob Bridson recently finished a Slingsby Skylark, with a build thread on the UK scale soaring forum http://scalesoaring.co.uk/cgi-bin/ya...1259597816/138

(in the flesh it is very nice and impressive)

It may be worth posing these questions to Rob via a PM.
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Old Nov 06, 2013, 05:01 PM
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so. cal.
Joined Jan 2006
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Alistair, I recently acquired Fred China's 1/4 scale Skylark 3, Fred made the wing very scale like, he used steel screws with brass finger "wings" brazed on to them, the center panel is set onto the fuselage and you reach inside and hand screw the bolts till they are finger tight. I can send pictures of how it looks if you like.

On the spar you might think about 1/2 inch rather than 3/8 width, better to have a little insurance rather than hope it is only good enough.

Dennis
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Old Nov 06, 2013, 07:02 PM
Vintage wood is the best!
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In a house
Joined Sep 2002
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I would do 3/4" x 1/2" for the main panel spar caps and then taper the outer panels from that size to 3/8" x 1/8"
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Last edited by SZD16; Nov 06, 2013 at 11:24 PM.
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Old Nov 06, 2013, 10:58 PM
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United States, KY, Taylorsville
Joined Mar 2010
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Make an 'I' beam spar. Decrease the density of vertical shear webbing from root to tip. The tip webbing will be the lightest employed. A little CF is always nice!
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Old Nov 10, 2013, 02:50 PM
Registered User
Tadley Hants England
Joined Sep 2002
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After measuring up found the fuselage was too long so reduced the scale to 1:4.3 for a 36" tip and a centre panel of 27" for a span of 126" 3.18M. Also a little smaller which is good for a scratch build.

Thanks for the tips on the spars going for 12mm x 4.5mm spars top and bottom with 1/16ply in the middle. Will face spars with 1/16 balsa front and back for the ribs to butt up to. Root rib is 8 3/16 (210mm) Going for 9mm x 3mm spars with 1/16ply and balsa facing for tips. Think it will be adequate and looks about right.

Alistair
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Last edited by alibodin; Nov 10, 2013 at 03:05 PM.
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