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Old Oct 31, 2005, 09:22 PM
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SoarScale
United States, WI, Wind Lake
Joined Nov 2004
814 Posts
P61C Black Widow series (#4)

Wing Tip Panels

The wing tip panels were built in a similar way to the wing center section except this time, they were built upside down. The reason for this was the need to have access to the bottom of the wing to install the spoileron mechanism. This can only be effectively done from the bottom surface. Again, foam cores were cut at the correct heights, correct anhedral and correct washout at the tips. The goal of these cores was to mate each side up to the center section, TOP surface cores, place the center section onto the center section cores and use these to align the tip panels to during construction.

The first picture shows one of the tip panel foam beds, pre-shaped top sheeting and the parts needed for the structure. Of particular note should be the assembly that is pre-built – the left most spar looking object laying on the sheeting. This is the hinge pin assembly for the spoileron. It was made with differing thickness ply laminates and the yellow internal component of a Sullivan Nyrod. The internal diameter of the yellow core is almost exactly 1/16” diameter which allows for a 1/16” piano wire hinge pin to pass through it. The slots that are precut are for the spoileron arms and allow them to pivot the required amount. Note also that some of the larger ribs have some reinforcement laminations where the spoiler blade recesses into the wing. Balsa alone at this point would make the rib very prone to damage. You’ll also note on the right hand side of the picture the beginnings of the internal structure layout and gluing of the other wing tip panel. Again, careful marking of the sheeting for spar, spoileron and ribs is important.

The second picture is of the wing assembly in the top right of the first picture photo. You’ll see the basic structure in place as well as the internal framing structure for the spoileron glued to the top surface. On this wing, I have already cut out the slots in the top surface for the spoileron arms and blade. I simply used a dressmaker pin to mark the corners of the slots while the wing was resting in the core as you see it. Flip it over, cut them out and your done.

The third picture shows a mid-stage shot in one wing tip panel construction. The foam cores are now all temporarily joined together on my flat working surface and aligned along the LE which is straight. The center section is positioned in place on the cores and weighted in position. The root rib, joiner and locator pins on the root rib are placed in position against the end rib of the center section therefore ensuring good alignment. Spars and ribs are added and when satisfied with the fit of the joiner tube, it too is glued into place.

Servo hatch rails are added between ribs where servo’s will be installed, wire tubes, LE etc.

Now, with only the top surface sheeted and the structure in place, the wing was still fairly “flimsy”. I needed to have the wing a little more rigid to support the building of the spoileron. I therefore decided to sheet the LE section to the center of the spar and accomplished the sheeting task of the bottom surface of the main wing in two parts. The forth picture shows the addition of the LE sheeting to the center of the spar. It really made a difference and provided a good base to install the spoileron. This would not have been my chosen method of applying sheeting to the bottom surface of the wing but due to the spoileron requirement, it needed to be split into two pieces – LE to spar, spar to TE.

Servo mounts and servo’s were also added at this point.
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