Chapter 20 -
Winglets and Rudders
Start: 10/13/07
Finish: 03/17/08
Total Time: 75 Hours
Things are really starting to take shape
now. This chapter will have us build the last of the control surfaces.
As this project keeps growing in size, our garage is getting more and more
cramped. Fortunately we've managed to get a hangar at St. Cloud, where we
will base this aircraft when it's complete. Until that point we'll store
some of the bigger pieces at the hangar. As yet, though, we still have
everything in the garage. Can't take the wings up there until we have the
winglets attached. Can't take the spar up there just yet, as we're waiting
for our spot facing tools to be sharpened so we can bore the wing attach holes.
Soon though, we'll be able to free up a good amount of space in the garage.
We start this chapter off by gathering up
all the big leftover foam blocks from the wing, which are used to make the
winglet cores. We cut the upper and lower winglet, both right and left in
one afternoon, and assembled the blocks with micro. Careful attention must
be paid to which side the undercamber faces, the mailing list archives are full
of info about it, and sadly a few stories of those who didn't get so lucky on
their first attempt. Our cores came out very nice, our excitement
continues to build along with aircraft.
After the micro cured we made the top cap
for the upper winglets and rounded the lower winglets per plans. Next we
glassed the inboard side of the upper and lower winglets. Once cured, we
flipped the winglets over, installed the COM antennas, and glassed the outboard
side.
We turned our attention back to the wings
for a bit to finish the control system components in the wing roots, and then
proceeded to begin attaching the left winglet to the left wing. This
starts by trimming the bottom of the upper winglet. The plans have you use
a coping saw for this task, which didn't work well for us. It lead to the
worst mishap we've had in a while. It was difficult to keep the coping saw
perfectly perpendicular to the cut line. Worse yet, the saw cut more than
intended at the worst possible time, accidentally severing the cable for the COM
antenna. Repairing the cable was tricky. We had to carve out a bunch
of foam surrounding the cable, attach male BNC connectors to each end of the
severed cable, connecting them with a barrel connector.
After jigging the winglet into place on
the end of the wing, we carve out foam at the mating edges, and lay up bid
around the corner. The corners are then filled with foam and flox to keep
the glass free of air bubbles. A spacer block is then formed to fit the
space between the wing and winglet, and an additional layup is applied on the
outside of the mating corners. The foam block is then attached over the
top of the layup.
Yet another multi month pause in progress.
A 10 week pause beginning in November of '07 started due to work travels, then
holiday travels, and ultimately I spent most of January scratching my head
trying to determine how to install the hidden rudder bellhorns. Fresh off
my incident with the COM antenna cable, my confidence was a bit low, and trying
to figure out the proper positioning and angle of the bellhorns had me severely
questioning if I was in over my head. Christine was trying to get me
motivated, but recognized that I needed to resolve the rudder bellhorn puzzle on
my own in order to restore my confidence. In the end I turned to the Cozy
Mailing List for help. I explained what I perceived as the issues with
installing the bellhorns and how I thought it might be handled. In
response I learned angle I was fretting about (caused by the canted winglet)
really wasn't as much of an issue as I was making it out to be. I simply
needed to make sure the tip of the bellhorn ended up in line with the rudder
conduit, when the rudder was fully deployed. As is so well put on Wayne
Hicks' write up of the installation, one really just needs to get busy doing it.
After glassing the bellhorn into place,
and making the spacers for the hollow area the bellhorn will travel through, we
proceeded to carve the big foam spacer between the upper winglet and the lower
winglet. Once that was complete, we laid up the 7 ply layups on the
outboard and inboard sides of the upper winglet to wing attachment. In the
plans Nat cautions not to add additional plies to these layups as they exceed
requirements already. Admittedly, the winglet attach seemed VERY solid
after these layups cured.
The next step was to attach the lower
winglet. This is accomplished by trimming the lower winglet to position it
at W.L. 18.4" and then micro it into place and lay up the sides with 1 layer of
2" wide BID at the seams. While I realize the lower winglets are not
a high stress area, this layup schedule just simply didn't give me a warm
feeling. I widened the BID to 4" and used 2 plies. When complete
this definitely seemed like a solid connection.
Next the rudder dimensions are drawn out
on the inboard and outboard side of the winglet, and one carefully cuts through
the skin on both sides. You then slip a hacksaw blade in the cut line, and
saw through the foam to remove the rudder from the winglet. Foam is carved
out of the ends of the rudder as well as the cutout area of the winglet, and
reinforcing glass is laid up in these channels to prepare for the hinge
attachment.
To attach the rudders back to the winglets
with the hinges, we start by lining up the hinges in a straight line on the
winglet. We then clamped them in place using little c-clamps to hold them
while we drilled the holes for the click bonds. We are using click-bonds
instead of screws and rivets, just as on the ailerons. This is to allow
for a completely smooth surface with no screw or rivet heads. Once all the
holes are drilled in the winglet, we recess the head of the click bond in a thin
bed of flox on the surface, and nut the hinges in place to hold everything.
A layer of BID is then glassed over the top of the click bond.
After the winglet hinge attached has cured
we handle the rudder side. We first made little foam wedges to hold the
hinge tight up against the inside surface of the rudder. Then we placed
the rudder back into the winglet, and form the inboard side we slid the hinges
up against the inside surface, using our foam spacers to hold them tightly in
place. Then while holding the rudder perfectly in line, we drilled the
holes through the rudder skin and hinge. We then removed the hinges from
the winglet side, and repeated the click bond installation process on the rudder
side. When cured, we can attach the winglet side of the hinges back into
place with the rudder.
The last step is to install the rudder
return spring. This consists of a 1" diameter aluminum tube, with a plug
on one end and a spring attached to the plug, being embedded into the winglet.
A small hook is embedded into the forward face of the rudder, to which the other
end of the spring is attached.
Now the whole process is repeated for the
other winglet. This time we just need to be a little more careful around
the COM antenna cable.
