Prepping and root ribs
... and figgering out the wing mounting
Updated Jan
11 '03 -- added pic of the aileron horn hard point
and a link to the page on sheeting the wings
As promised, the next step is to make and prepare the root ribs,
They're cut from 1/8 lite ply. They'll be lightened, the anti-rotation (wing adjuster)
points will be reinforced with one additional thickness of lite ply, and the
maple block wing mount reinforcements will be installed.
Then the ribs and cores are prepared for a zero-gap fit with the fuselage
Finally, the ribs and fuse are drilled for anti-rotation pins (wing adjusters)
and mounting system.
So here we go...
The left root rib is shown here, aligned at 0 incidence relative to the tail,
and tack-glued to the side of the fuse.
The
Nov 23 pics showed it roughed, and with the wing tube hole cut. Now it's been
lightened, and reinforcing points (1/8 lite ply) have been added 7" forward of
the wing tube center, and 9" aft of it. These reinforcements are where the wind
adjusters will go.
** The decision on where to put the wing adjusters went
like this:
Option 1 was to put them equidistant from the wing tube center so that
they'd get turned an equal amount when changing the wing incidence..
Option 2 was to place the adjusters as close to the leading / trailing
edges of the fuse as possible, to increase their effective moment arm / reduce
stress on them and the other components. Downside is that when setting the
incidence, the front adjuster (7" moment arm) will need to be turned a little
less than the back one (9" moment arm) for a given incidence change.
** I chose option 2 as the better engineering solution.
The next job after tacking the ribs is to fit them to the
wing cores. Turns out the fuse sides are curved, not flat, through the wing root
area - so it's necessary to add material somewhere to make the wings exactly
match the curvature of the fuse.
-- The wing cores meet the fuse at the wing tube, but the fuse curves away both
forward and aft (and one side, has a LITTLE bit more vertical slope up toward
the canopy than the other... so before sheeting the wing I'll add light balsa
shims to the wing-core side of the root rib, then fill the remaining gap with
epoxy and micro balloons. The intent is to keep the remaining space between core
and root to less than 1/32".
This
shows the left rib with the required reinforcements and balsa fillers in place,
and with the wing adjusters temporarily fitted. The left side took a max of
3/32" of balsa shims.
This is the right-side root rib in place - it needed more material on the upper surface than the lower, and about 3/16 at the trailing edge in order to meet the ding core.
Here's the final fit of one of the root ribs -
less than 1/32 gap throughout.
The pics also show a small maple block mounted to the wing-side
of the root rib near the wing tube. This is part of the wing mounting/ securing
mechanism - with thanks to Dick Hanson who (I think) designed it, and to Bob
Pastorello, who installed this setup on my dear, departed EMC... So here's
the deal -
There'll be a 6-32 socket head bolt threaded and epoxied into the block in
the wing root. The
head will stick out of the wing root. When mounting the wing, the bolt will go
into another maple block mounted inside the fuse, and a 4-40 will be screwed
down thru the fuse block to trap the head of the 6-32 wing bolt, holding the
wing on.
Here's
the inside of the fuse showing the interior blocks epoxied to the fuse side and
the wing tube, and the 4-40's accessible through the canopy opening. In the left
(upper) block, you can barely see the head of the 6-32 wing bolt in the
hole in the side of the fuselage-mounted block.
( This pic also shows some of the initial work in the fuse interior. Since I'm using a different anti-rotation pin arrangement than the original builder had planned, I removed both of the supports from the inside of the plane. The lighter area in the photo above is where the rear pin and supporting structure was originally.)
Locating the adjusters and the mounting bolts.
The following was all done while the ribs were tacked to the fuse
sides The results are already shown in the pics above, but after the
balsa shims had been fitted, I also drilled the locating holes for the wing
adjusters and the mounting bolts. I used my drill press, and drilled #1 holes
(slightly less than 1/4") for the adjusters and #36 for the 6-32 wing mounting
bolt. Then I popped the ribs off the fuse sides, tapped the root rib hole for a
6-32 bolt, and enlarged the mounting bolt hole in the fuse side so that the head
of the 6-32 bolt would fit.
Finally, I made the hole for the 4-40 wing securing bolt. With a #43 bit,
I drilled down into the fuse-mounted maple block (needed the Dremel flex
extension for this since there wasn't enough lateral clearance for the chuck of
a regular drill or a Dremel tool in there) then tapped the hole 4-40.
And there it was - the wing roots are now accurately aligned to the fuse, and
the wing mount system is in place and functional.
And....
While all this was going on, I've been doing final work on the wing
cores - not a lot that'll show in photos, but...
balsa caps on the lite ply intermediate ribs
detail sanding
Capping the ailerons
Installing the aileron control horn hard points -- 1"x1" end
grain balsa blocks in the ailerons that will receive 5/8" dowels where the 6-32
threaded rod control horns will be epoxied.
What's next
-Planning the Interior design on the fuse for the landing gear, tank, radio,
etc
-Installing the adjusters in the fuse
--mounting them to lit ply plates
--enlarging the fuse holes to allow for vertical movement
-- epoxying the adjusters in place
- Final wing prep and sheeting
-- Actually mounting the wing roots to the wing cores
-- Final light overall sanding so everything matches
--Accurate templates showing where all the 'stuff' is
--aileron edges, servo locations, control horn locations, etc so I can find them
after the sheeting is epoxied on
-- Routing the wing for the span wise upper and lower carbon
fiber strip spars
Jan 11 - This is all documented at
Sheeting_The_Wings
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Building a Hybrid Pattern Plane
