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PT 1/4 scale PIK20 built up wings**

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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

PT 1/4 scale PIK20 built up wings**

Post by Peter Balcombe »

Cliff wants to be able to offer a built-up wing option for his PT model range, so this is a new wing design proving build for the first of the alternative wing designs. (The156" PT Vega wings are also in development.)

All of the built-up wings are being designed to be able to be used as direct replacements/alternative build options to the standard foam cored types. In general, they use the same hardwood LE, stock TE & aileron features, but built onto a wing core using laser cut parts and overall sheeted in 1/16" balsa.

The spruce main spars are strengthened by a full length 1/16 ply interlocking spar web. Dummy LE and TE strips also engage into rib end tabs to form an interlocking wing core structure. Two lower building tabs on each rib also assist ensure correct build alignment. The wings also employ a brass joiner tube to match that in the fuselage, thus avoiding the need to fix the steel blades into the wings as on the original design.

Finally, all wing control servos are mounted in the wings, rather than have a fuselage mounted flap servo. The option is also included to fit either servo operated airbrakes or servoless equivalents.

The wing parts go together very quickly and I managed to put the basic structure of the first wing together over the plan in an afternoon - even with the use of Aliphatic glue rather than Cyano.
The pre-built lower spar was added next, after lying the wing structure on its back. Note that the spars taper both in width and thickness from the wing taper change point in order to some "meat" is left at the tip rib to attach to.
Once the lower spar is in place, the structure is turned over again to add the root end rear spar web, which again notches into place. Note that the front & rear spar webs, together with the top & bottom spars, form a complete box around the joiner area, allowing this to be later filled with hardwood/epoxy to give a rock solid attachment to the main spars.
The dummy trailing edges will later be supplemented with 3/16" balsa to provide the same 1/4" control surface hinging thickness as on the foam wings, with the top & bottom skins going from the dummy LE to the rear of the hinging strips.
Attachments
PT 1_4 scale PIK20 built up wings.pdf
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