[NOTE/WARNING! - The following _is_ excruciatingly detailed on purpose,
therefore appallingly long-winded, as only I can do so well, so often.
Unless you really like to suffer and/or really want to double check the
suggested technique, if you've already done the struts successfully,
save yourself! Skip it! :-) ]
Jesse,
This is what I did the second time around. This _is_ a helluva lot of
work, especially when you're doing both struts. Miraculously, one of my
original struts somehow turned out fine the first time even though I
wasn't nearly this careful, so I only had to redo one. In hindsight,
that was pure luck -- shouldn't have happened. :-)
I'd suggest reading the whole thing through first to get the idea, then
follow it carefully as you do the job. Most of this will be obvious, but
a couple of things might not be. Those are the ones that might bite. For
me, having things described several different ways is the (only?) way I
learn. I hope it will help. Here goes:
After setting the dihedral and positioning the strut and blocks to be in
the middle of travel, both vertically along the strut, and side-to-side
in the wiggle room for each block, I clamped the lower block tight in
the strut, then drew a couple of crossing lines (do use a short straight
edge) to help check things weren't moving, then took the strut and
blocks off, then located the first hole (skinny block end) through the
top side of the strut. So far, more or less like the manual says, only
with tight clamps!
Inevitably, when you "find" this first hole, the block will be a smidgen
off from where your measurement showed it should be. That's why you have
to put the strut & blocks back on the fuse and reset everything again.
And you do have to reset the positions based on the location of this
first through-pinned hole that you've "found", because the angles
between the blocks and the strut are critical. Angle error at one end
will be magnified at the other end, and you'll end up with unacceptable
side-load or bending stresses on the attach points. So...
With the first 3/16" hole on the skinny end pinned through the top of
the strut (I used multiple 3/16" drill bits for pins) -- and still
clamped! -- I put the assembly _back_ on the fuse to recheck the block
position & angle (middle of travel). Then I tightened down the clamp
_again_. (Don't forget to triple check the wing dihedral at that point,
as well as the positioning of top block. Personally, I also checked and
re-checked my fuse leveling, fore and aft and sideways. I didn't want to
have to do this three times!) With the bottom block securely pinned in
the first hole _and_ clamped, I took the assembly off the airplane,
being careful not to bump the clamps.
I then measured for the second hole at the other end of the block. The
next point should be obvious, but I almost blew it once. Don't forget
the geometry of the block inside the strut. To keep the bolt line in the
middle of the block, the line you draw for the rest of the holes is not
parallel to the either side of the block! It splits the angle that the
sides of the block make, so be sure to draw it from the center of the
first hole on the skinny end, to the center of the block where it comes
out of the end of the strut.
With the second hole located, I drilled through the top side of the
strut to mark the second hole in the block. I think this "marking" can
be done carefully with just a steady hand drill. You're only drilling
about 3/16" of material in total -- not much room for wandering drill
chatter to happen. Then I disassembled everything and drilled the first
two 3/16" holes through the block (only) on the press -- but only after
first making darn sure the drill press setup was well clamped and square
-- before drilling each hole!
[TIP: To keep the block from rocking over/into the center hole of your
drill press vise, put a strip of scrap 1/8" aluminum bar stock under the
block to support it, then clamp the block in the vise both sideways and
top/bottom, and you can just drill into or through the bar stock, which
gives a solid footing to keep the block from rocking into the vise center.]
With the block and strut back together, I then placed a 3/16" drill bit
"pin" in both holes, through the top of the strut and the block, so the
pins rested on the inside of the bottom of the strut, then clamped
again. Remember, "clamped" means that block cannot wiggle at all.
Then I removed one of the pins and, using the 3/16" hole in the block as
a guide for the bit, let the bit slide down the existing hole, and
_carefully_ drilled down through the bottom of the strut. I just used a
hand drill. The bit isn't going to wiggle/chatter much if it's already
an inch and a half down a tight hole, and only has to go through 1/8"
more of the strut bottom. With one hole now completed all the way
through the block and strut, I bolted* that hole while keeping the clamp
also still tightly in place, then pulled the second "long pin" out, and
drilled the second hole through the bottom of the strut. Then I bolted
the second hole, and now had the two outer 3/16" holes bolted through --
tightly.
[*NOTE: Whenever "bolting" in this procedure, be sure you actually use a
washer and nut on the bolt and snug it up. It's probably a "duh" point,
but... there's a temptation to drop two bolts into the holes and think
everything is lined up and it should be enough, but... it's not. The
block will wiggle, the bolts will wiggle, and you'll be doing this a
third time. So "bolted" means it's snugged up tight enough to fully
"clamp" the strut and block together.]
Then I shallow "marked" the other three 3/16" holes from the top with
just a hand drill, took everything apart and drilled those three holes
through the block alone on the press -- but again, only after making
very certain the drill press setup was correct and secure. I then
re-bolted the _same first two holes_ that were already completely
drilled all the way through the strut, and drilled the last three
(middle) holes through the bottom of the strut. At that point I had a
complete set of (5) 3/16" holes all the way through that were straight.
From there on, I enlarged ("marked") the middle three holes with a 1/4"
bit through the top of the strut and just down about 1/8" into the block
(with the outer two 3/16" holes still bolted tight) -- just far enough
to be able to "find" and center those holes well in the press. I then
completed enlarging those three middle holes in the block to 1/4" on the
press, then bolted the outer two holes again, drilled the middle three
1/4" holes down through the strut bottom, then "marked" the two outside
holes to 1/4" size, disassembled and finished drilling the last two
holes to 1/4" on the press, then re-bolted the center holes, and
finished the outer two 1/4" holes through the bottom of the strut.
Repeat the process in detail for other blocks.
In essence, whenever you're drilling the pieces together, they must be
secured in two places, first by clamps, and then by bolts. When you get
to a point where you can always bolt at least two holes, then just
alternate the sets of holes that are bolted until you get them all done.
It will come out well that way, as long as you're careful to securely
clamp/stabilize the block whenever it's in the press, and carefully snug
up the bolts in between drill press runs. This is very time consuming,
but that's good! :-) You have to take your time and double check, triple
check the stability before you drill any of the holes -- at every stage.
I hope this is clear enough to help somebody get this done right the
first (or second) time. Please email or call me if anything isn't clear,
or if you have any questions at all.
Ron
254R
360-681-7160
Jesse Jenks wrote:
I know, it's funny that a drill bit is one of the more tricky tools to use
correctly, and not the best thing for making a good hole. I think if I end
up enlarging the holes, I will get my friend to do it with a boring tool in
a milling machine. I don't think I would make custom fittings. It would be
easier to just start over with new parts from MAM. If I do that, can you
describe the technique that you used? If you drilled/reamed the fittings in
the drill press, at what point did you drill the holes in the struts, or did
you do everything together and somehow clamp the whole strut to your drill
press?
Thanks.
Jesse
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