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Old Nov 01, 2005, 12:36 PM
SoarScale2 is offline
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United States, WI, Wind Lake
Joined Nov 2004
814 Posts
P61C Black Widow series (#8)

OK, so, the wings were almost done - would I have done anything differently?
Well, yes. The primary thing I would have done differently was to use fiberglass laminate for the trailing edges of the small flaps and flaperons. There are a couple of fiberglass laminates out there - G10 and Glass Ply from ACP. I had never used balsa as a sheeting material for my sailplanes - I have always used Obechi. Between the obechi and foam has always been a wet-layup of either fiberglass cloth or carbon cloth, depending on the aircraft. This created a very stiff TE that could be sanded to knife edge and preped accordingly for the finish. I didn't consider it for the P61 wings.

As it turned out, the small flaps were a non-issue and with the addition of the vellum coves in the flap area, the TE was stiff enough (see later pics). The flaperon however, was a different story. Predominantly caused by the tapering of the TE grain of the balsa at the flaperon TE, the result was fragile. I therefore decided to laminate some 0.020 Glass ply from ACP to the top surface of the TE's of both flaperons. This was done AFTER the wing was constructed. I used a dremel as a router and routed a 0.020 recess, about an inch back from the TE to the actual TE and then glued in a piece of glass ply. Not the easiest taks and you only have one chance to get it right - fortunately, I did - on both wing tips! If I had it to do again, I would laminate the glass ply into the balsa sheeting BEFORE applying it to the wing. Lesson learned!

Another item I did not mention was the hinge system for the small flaps in the center section. As I noted before, I am a big fan of removable surfaces. The Ziroli plans do not show a removable flap. Also, the flap itself is "captured" both ends by wing structure making it almost impossible to slide in a 1/16" piano hinge pin from either end. So, I made a call to go a little non-scale and drop the hinge line down below the bottom surface of the wing by about 1/8" and built two hinge systems similar to the flaperon above and used 2-56 socket head bolts and brass hinge bearings to attach. Not truely scale, but not permenantly attached to the wing either - see pics below. I have also vacuum formed a few small fairings to cover the hinges - the result is much better than just the hinges themselves.

Last item: The later versions of the P61 were fitted with four pylons for drop tanks. There are no mounting plates in the Ziroli plans for these so they need to be added. Unfortunately, I completely forgot to add them to the center wing section during construction but DID add them to the wing tip panels. Where they are located on the aircraft means that for the center section, there is nothing but the sheeting to attach them to for me. I think I will vacuum form them from a plug making them very light ang glue directly to the sheeting with perhaps some CA hardened screw holes in the sheeting. The tips are now no issue with the braces I installed between the ribs.

Fuse next!
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