Tapered Wings and North-Paw Saws

Cutting a long taper in aluminum bar or angle stock is always something
of a chore. Not because it's a chore-type chore - - the work goes
quickly enough - - but because we don't do it very often and have to
get things set up for the job.

After sawing the taper you sand away the saw marks then polish the
edge, allowing a thirty-second or so for the clean-up. Which means
your cut needs to be not only straight but accurate. Most guys probably
set up their table saw for the task, using a taper jig for short pieces
or setting up the stock off-set against a board. The board follows the
saw fence and the metal is attached to the board at the required angle
and the result is that you cut a long taper into the piece.

Bandsaw works okay too. But most folks use a table saw. Unless the
piece is too long.

Working with a table saw or bandsaw, you need a work space twice the
length of the part to be tapered, half of it behind the saw, the other
half in front. Most of us keep that in mind when we set up our shop
and provide a minimum of about sixteen feet for the table saw, allowing
us to rip a sheet of plywood. Anything longer than eight feet, you
generally have to move things around. But with a fuselage typically
being longer than a wing panel, if you're cutting longerons or
stringers, you may run out of room.

I recently took two sticks of 6061-T6 extruded angle, cut them in the
middle with the intention of tapering both flanges only to discover I
didn't have room to run them through the table saw. I've got
sixteen feet in front the saw but I had a disabled camper behind it,
limiting the length of stuff I could feed into the saw to about eight
feet. Which wasn't enough.

I could have done it on the bandsaw if I'd been twins but working
alone, I didn't think I could support the work and feed it accurately
enough.

When you can't push the work through the saw the next alternative is
to push the saw through the work, meaning you secure the work to
saw-horses or a work bench then go at it with a saber saw, portable
circular saw, a router or even a hand saw if you've really got to get
the job done.

I decided to use a method described by Mr. Ryan Young some years ago on
the Teenie Two list. His idea was to make up a clamping strip to
secure the work to the edge of a work bench. The clamping strip is
made of quarter-inch plywood with a stringer glued to one edge to act
as a fulcrum, forming a Class Three lever. The strip is fastened to
the edge of the work bench by an evenly spaced series of deck screws or
sheetmetal screws at a height that would place the flange of the
angle-stock level with the top of the work bench.

In use, the clamping strip forms a slot into which you insert the
'down' flange of the angle-stock. Tightening the deck screws
clamps the work in place with more than enough force to hold it in
place while being sawn.

To ensure a straight cut, a batten is nailed to the top of the work
bench, providing a guide for the shoe of a portable circular saw.
Aligning the individual pieces to a witness mark allows identical
tapers - - about one inch in ten feet - - to be cut with a high degree
of precision.

I already have a twelve foot work bench with a maple edge out back of
the shop so all I needed was the clamping strip. Making the clamping
strip is dead simple, assuming you have a pneumatic tacker and a jug of
urethane glue. Plus the stringer, of course. (I used several scraps of
quarter-inch square stock, rejects from the Stick Rib Factory.) Since
I wanted to hold pieces of angle-stock that were more than 8 feet long
it meant the clamping strip would have to be spliced.. Since it clamps
to the outside of the angle-stock, the clamping strip can use butt
splices and scab plates, which can be whipped out about as fast as you
can cut the pieces. Butt ugly, of course. Which is why I scarfed the
joins.

I drilled a hole every six inches to accept deck screws. Turns out,
for this job you only need one screw about every three feet, but there
you are.

Once things were set-up I positioned the batten as a saw-guide and
after measuring everything about nine times, nailed it to the bench.
The cut was made with a worm-drive Skil-saw that has a plastic plate
attached to its shoe. This saw has cut several miles of aluminum with
nary a scratch, thanks to the plastic plate. Since the angle-stock was
eighth- inch thick 6061, I used a fairly coarse-toothed blade, cutting
without lubricant at the rate of about thirty feet per minute.

As expected, the coarse-toothed blade left a pretty rough edge.
Leaving the work in the clamp, two passes with a portable belt sander
fitted with a #80 belt got rid of the saw marks and switching to a #120
belt got rid of the #80 marks, leaving a surface smooth enough to be
dressed with a Roloc pad, a task that could be done in the shop after
both flanges had been tapered.

After cutting and smoothing one flange on all four pieces, the batten
was taken up and repositioned to facilitate cutting the remaining
flange. That is, the angle-stock is flipped end-for-end. The reason
for this is that the Skil-saw is a 'right-hand' saw, meaning the
shoe and most of the weight is positioned on the right side of the
blade. Since you want the shoe to ride flat on the table and bear the
weight of the saw, all of the cuts must be made in the same direction.
In effect, the first flange was cut from the tip toward the root.
Flipped end-for-end, the second flange is cut from the root toward the
tip. The saw - - and the person using it - - remains in the same
position relative to the table, which does most of the work by holding
the work and bearing the weight of the saw, allowing it to accurately
guide on the batten.

After repositioning the batten the second flange was cut. Not counting
the time to make the clamp, it took about one hour to make the eight
cuts, most of which was spent smoothing the cuts with the belt sander.

What I'm making here are spar caps. Since the flanges are identical,
after being tapered one of them is selected as the Master and gets
about a gazillion holes drilled into it for the shear web. It is then
clamped back-to-back to another spar-cap and serves as the drilling
guide, resulting in a pair of mirror-image spar caps, one for the
upper, the other for the lower. Each of these is then used to create
ANOTHER mirror image, resulting in four identical - - but opposite - -
spar caps. All of which is pretty much Metal Shop 101 with the
exception of the nifty clamping trick, thanks to Mr. Ryan Young.

Which of course is stuff most of you guys already know. So why am I
bending your ear? I'm glad you asked...

- - - - - - - - - -

I'm not the only guy chopping spar caps out of aluminum angle and
another fellow tackling the same job had run into the same problem: Not
enough room to run the angle-stock through his table saw. In an
exchange of messages and photos I described the method I used and he
made up a similar clamping arrangement.

Total Disaster. Or sorta so.

One reason for wanting to make an accurate cut is that the cut-offs - -
those long spears of aluminum that end up on the floor - - are meant to
be salvaged and used as stiffeners on the horizontal stabilizer. But
in making his cuts the other fellow found it nearly impossible to keep
the saw against the guide. The saw would tilt just enough so that
feeding it through the aluminum tended to pull the shoe away from the
batten, resulting in a curvy cut. Repeated passes cleaned up the
flange but the cut-off ended up in several pieces making it unusable
for re-enforcing the horizontal stabilizer.

Why? Because the fellow was using a LEFT-HAND circular saw but had
copied my set-up. In doing so, he had only the narrow portion of the
shoe on the right-hand side of the blade to provide support. That
meant he not only had to guide the saw, he had to support most of its
weight. And since we're dealing with a taper that meant the
required amount of support would increase as the cut progressed.

Clear as mud? Probably :-)

I'm right-handed; a North-paw. So are my portable saws. When making
the tapered cuts the work bench is on my right hand side. To make the
cut I simply walk along beside the work bench, pushing the saw and
making sure it stays in contact with the guide. I'm not supporting
anything - - the work bench is doing that. My back is straight (or
nearly so), my weight is balanced over my hips and I can make the cut
as fast or as slow as I wish; there's no physical strain. Bottom
Line is a straight, accurate cut.

But when you have a LEFT-HAND saw, for this particular job it means the
work bench should be on your left and, ideally, you should be guiding
it with your left hand. Of course, if you happen to be right-handed,
things can get a bit awkward. Which is why they make both right- and
left-handed saws, a fact some folks were not aware of.

-R.S.Hoover

wrote in message
oups.com...

Snip lots of good stuff from our #1 common sense expert!

I'm right-handed; a North-paw. So are my portable saws. When making
the tapered cuts the work bench is on my right hand side. To make the
cut I simply walk along beside the work bench, pushing the saw and
making sure it stays in contact with the guide. I'm not supporting
anything - - the work bench is doing that. My back is straight (or
nearly so), my weight is balanced over my hips and I can make the cut
as fast or as slow as I wish; there's no physical strain. Bottom
Line is a straight, accurate cut.

But when you have a LEFT-HAND saw, for this particular job it means the
work bench should be on your left and, ideally, you should be guiding
it with your left hand. Of course, if you happen to be right-handed,
things can get a bit awkward. Which is why they make both right- and
left-handed saws, a fact some folks were not aware of.

-R.S.Hoover


Interestingly most of the old SKIL worm drive saws I have seen have been
right handed. Both of mine are.

On the other hand, the large majority of the common direct drive power saws
sold by Sears, and other such places are left handed. I have a couple of
those also and both are LEF T handed.

I have often wondered why this is so.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

Note: The 2006 P'Ville flyin is May 19, 20, and 21. Start your planning
now. Email Mary at so she will have the right groceries on
hand so we can feed you at mealtimes!

In article , "Highflyer"
wrote:

wrote in message
oups.com...

Snip lots of good stuff from our #1 common sense expert!

I'm right-handed; a North-paw. So are my portable saws. When making
the tapered cuts the work bench is on my right hand side. To make the
cut I simply walk along beside the work bench, pushing the saw and
making sure it stays in contact with the guide. I'm not supporting
anything - - the work bench is doing that. My back is straight (or
nearly so), my weight is balanced over my hips and I can make the cut
as fast or as slow as I wish; there's no physical strain. Bottom
Line is a straight, accurate cut.

But when you have a LEFT-HAND saw, for this particular job it means the
work bench should be on your left and, ideally, you should be guiding
it with your left hand. Of course, if you happen to be right-handed,
things can get a bit awkward. Which is why they make both right- and
left-handed saws, a fact some folks were not aware of.

-R.S.Hoover


Interestingly most of the old SKIL worm drive saws I have seen have been
right handed. Both of mine are.

On the other hand, the large majority of the common direct drive power saws
sold by Sears, and other such places are left handed. I have a couple of
those also and both are LEF T handed.

I have often wondered why this is so.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

Note: The 2006 P'Ville flyin is May 19, 20, and 21. Start your planning
now. Email Mary at so she will have the right groceries on
hand so we can feed you at mealtimes!

I'm not so sure that I agree with this right-hand, left-hand saw
business. What is a right hand saw for rip cuts is a left-hand saw for
cross cuts, and vice versa. Since, as Mr. Hoover himself pointed out,
most people would use a table saw for rip cuts, the handheld saw of
circular or sabre genre is generally relegated to shorter cross cuts.
For that application, it is normal for a right-handed person to support
the workpiece on sawhorses in front of him, with the "waste" end
extending to one's right. Presto chango, left-hand saw becomes
right-hand saw.

Never used the Skill for cutting aluminum, but - - ! Mine is
30-couple years old, a worm-drive model. The grips are positioned for
the right hand to hold the main grip, and to hold the switch. The other
grip is atop the housing, forward, and angled appropriately for
gripping with the left hand. The big shoe is to the LEFT. Does that
make it a north or south? Interesting, thanks.

Flash

Veeduber gives me entirely too much credit - I think it was his
suggestions that lead to the clamp setup I used, and he describes.

If you're a visual learner, here is a crummy picture of my setup:
http://25th.com/t2/viewfull.php?index=647

Lacking a portable belt sander, I used my router, running against a
guide, for prelimnary smoothing, along with a Vixen file, and an auto
body sanding board to smooth the cuts.

I too struggled with the "handedness" of my pawn shop portable saw, and
made some pretty wavey cuts, till I figure out that as long as the wide
part of the shoe was over the bench, I was OK, and I arranged my setups
accordingly. A few cuts were made with me kneeling on the top of the
bench, I seem to recall.

Ryan "Most of what I know about metal working I learned via E-Mail from
R.S. Hoover" Young

wrote:
Never used the Skill for cutting aluminum, but - - ! Mine is
30-couple years old, a worm-drive model. The grips are positioned for
the right hand to hold the main grip, and to hold the switch. The other
grip is atop the housing, forward, and angled appropriately for
gripping with the left hand. The big shoe is to the LEFT. Does that
make it a north or south? Interesting, thanks.


When using a circular saw your body should not be in line with
the blade. This is because they sometimes 'kickback' and when
that happens you do not want something like your femoral artery,
intestines, or the family jewels to be there.

So a saw is right-handed if the handle is to the left of the blade.
E.g. gripping it with the right hand puts your body to the left of
the saw with no part of your body in line with the blade, unless
you go out of your way to put it there.

--

FF