Rib Stitching: Ho Ho Ho :-)

To A Few:

Yes, I think what you're doing is funny, as in worth a laugh. Not in
the building nor the rib-stitching but in that part of rib-stitching
that you are finding so difficult.

It's funny because IT ISN'T IMPORTANT. And you would know that for
yourself if you'll just back away from it for a moment and think about
it.

The Load appears in the fabric. Okay so far.

The load is transferred INTO the ribs by the stitching, for which it
appears you have used a section of Anchor Cable good for about 60psi,
or thereabouts. Which is where I started to smile. But the amount of
load 'seen' by an individual rib-stitch is relatively small, and
that's where I started to chuckle because you've failed to work-out
that amount for yourself. So let's do that before you loose your kewl
entirely and start sending Nasty Grams to guys like me who are really
trying to HELP you, even if that does not appear to be the case. So
here we go, working out the load as 'seen' by your stitches:

First off, there's several ways to work it out. I'm interested in
seeing which method you use but we can IGNORE any load that appears in
the leading edge because for all practical purposes that particular
load never makes it past the SPAR. I see a span of about 24 feet and
a chord of about four feet, with very generous 'abouts' because the
center-section has a nice big cut-out so you can get into the cockpit
without surgery, and because your tips are not square. But for the
purpose of this example let's call the span 24 feet. Using a 4-foot
chord is fairly safe but here again, it is NOT precise becuase of the
cut-out & curvey bits previously mentioned.

And you want to pull SIX G's.

Lemme ask you something... Have you ever done that? Seriously; have
you ever strapped yourself into a flying machine and gone out and
ACTUALLY PULLED SIX GEE's? Okay, I didn't think so. So let's come
back to that later.

Right now let's take your twenty-four feet of span and multiply it by
four feet of chord and come up with our mythical 96 square feet of
lifting surface. (Yeah, I know. Just work with me here for a
minute.)

Now lets take that mythical 800 pounds of gross weight and divide it
by those 96 square feet and come up with the 8.33 pounds per square
foot... which you'll note is about the same thing you got in your
first message, okay?

Now lets 'fit' that weight to one of your rib-bays. First off, we
know that most of the lift -- about 65% of it -- is generated by the
first third of the airfoil. Yeah, pitch has a lot to do with it but
here again, let's just fiddle with the numbers for a while.

See that 14" rib bay? The one between the 16" bay and the 12" bay?
Let's use that one.

Fourteen inches is 1.16 FEET, so we know that section of the wing
'sees' 8.33 pounds times 1.16 feet, or about 9.66 pounds. Now this is
where I started to laugh, so follow me through here.

All of the loads picked up by this rib bay get coupled into the
spars. The leading edge -- the first ten inches of the chord-wise
slice through your wing -- go directly into the main spar. The
fourteen or so inches that extend beyond the rear spar will appear in
that spar. The tricky bit is what happens to the loads that appear
BETWEEN the two spars -- the two feet (24 inches) where you start rib-
stitching. And keep right ON rib-stitching, all the way back to the
trailing edge.

Where you went astray, and the reason I got to laughing at those
pictures -- is because the loads are INSIDE OF THE SPARS. You've no
reason to start using that 80 lb braided fishing line. The load(s)
that appear in the skins of your wings are ALWAYS about the same from
root to tip. They don't get added together until they get INSIDE of
your spars.

So I hope you'll agree that it was a pretty good joke, seeing you
graduate from regular rib-stitch cord to something heavier... and then
heavier still.

So how heavy a cord do you need? I think the stuff I use runs about
forty pounds but it's awful heavy stuff. I 'm sure I could get with
something of lighter weight. But I bought a whole spool of the stuff
during the Eisenhower administration and it looks like I'll be using
it until the cows come home.

-R.S.Hoover

wrote in message
...
To A Few:

Yes, I think what you're doing is funny, as in worth a laugh. Not in
the building nor the rib-stitching but in that part of rib-stitching
that you are finding so difficult.

It's funny because IT ISN'T IMPORTANT. And you would know that for
yourself if you'll just back away from it for a moment and think about
it.

The Load appears in the fabric. Okay so far.

(Much snipped)

What he says.
German aircraft prior to V-E Day used sewing thread to stitch the fabric to
fabric wrapped around or doped to the ribs. Even on the rocket-powered
Me163.

Bob

On Dec 27, 8:23*pm, " wrote:
To A Few:

Now lets take that mythical 800 pounds of gross weight and divide it
by those 96 square feet and come up with the 8.33 pounds per square
foot... which you'll note is about the same thing you got in your
first message, okay?

8.33 lbs = weight of one gallon of water.

Your plane will float upside down.

Mark
Starfleet Inspector

Yo, Starfleet Inspector...

I STILL got yelled at, privately and in Excellent Grammar, properly
spelled (rather than spelt) for my laughter at Another's Expense, but
only because I failled to mention TAPES, which is where the load
actually goes, rather than fabric, and he's right, in a way, but so am
I and we both know he's just picking at an old, hard scab 'cause he
was wrong once before on a correction and I sent him a zzinger and he
had to admit he meant to say X instead of Y and thank you very much
and what a Swell Fellow I was for not doing so publicly and I found
the pre-packaged msg that sed 90% (mebbe more) of my mail is like that
(which is still true) but now that I'm sort of dying-off, I've been
making it sort of public/private because when you're feeling like S**t
and your best Physician is not quite as old as your best pair of
boots, it sort of changes your view of things and you become less of a
Kind and Gentle Man and become more of the mean sonofabitch type who
will light up a good cigar in front of a Bad painting because I know
the difference even if I haven't had my ticket punched by one of those
Ivy Leage schools (or any school at all, come to think of it...
although one was very nice about offering me something for saying nice
things about... I forget what... something they did... and 'ol Bucky
Brewster was already dead and they tend to like his dry blood-letting
as compared to my Riding into Town, reins in my teeth, shooting right
& left and actually HITTING something, unlike Bucky, who didn't (and
didn't believe I could until I showed him how).

But seriously, after paying all tht money for that insignificant piece
of paper to hang on their wall, you really owe it to them to find
someone else to Bless them on their Way. (And besides, I've already
got a D.Phil. and was sorta hoping for something more grandiose. )

Bob Hoover (No, I'm STILL the other one. And will always be.)

On Sun, 28 Dec 2008 10:18:49 -0800 (PST), "
wrote:

Yo, Starfleet Inspector...

I STILL got yelled at, privately and in Excellent Grammar, properly
spelled (rather than spelt) for my laughter at Another's Expense, but
only because I failled to mention TAPES, which is where the load
actually goes, rather than fabric, and he's right, in a way, but so am
I and we both know he's just picking at an old, hard scab 'cause he
was wrong once before on a correction and I sent him a zzinger and he
had to admit he meant to say X instead of Y and thank you very much
and what a Swell Fellow I was for not doing so publicly and I found
the pre-packaged msg that sed 90% (mebbe more) of my mail is like that
(which is still true) but now that I'm sort of dying-off, I've been
making it sort of public/private because when you're feeling like S**t
and your best Physician is not quite as old as your best pair of
boots, it sort of changes your view of things and you become less of a
Kind and Gentle Man and become more of the mean sonofabitch type who
will light up a good cigar in front of a Bad painting because I know
the difference even if I haven't had my ticket punched by one of those
Ivy Leage schools (or any school at all, come to think of it...
although one was very nice about offering me something for saying nice
things about... I forget what... something they did... and 'ol Bucky
Brewster was already dead and they tend to like his dry blood-letting
as compared to my Riding into Town, reins in my teeth, shooting right
& left and actually HITTING something, unlike Bucky, who didn't (and
didn't believe I could until I showed him how).

But seriously, after paying all tht money for that insignificant piece
of paper to hang on their wall, you really owe it to them to find
someone else to Bless them on their Way. (And besides, I've already
got a D.Phil. and was sorta hoping for something more grandiose. )

Bob Hoover (No, I'm STILL the other one. And will always be.)


I'm one of the few people in the world with a tractor but no PhD.

I can see that you've made a mistake there.

If you have a PhD I'd normally defer to your wisdom but my mate who
has two PhD's is a bit insistent that I speaque up.

you are correct that the rib stitching just sees the local air
pressures and that the air pressures arent additive, the effect of
their combined moments in the spars is accumulatve as you mention.

where you come unstuque is that you have neglected the increased
airflow in the slipstream behind the prop. this area doesnt need
thicker rib stitching. the technique is to use the same rib stich
string but make the loops closer together. in other words use more
loops per foot of rib. ac43-13 has some good guidance and a table that
gives the rib stitch distance as related to airpeed. you can find
ac43-13 as a free download on the web.

why did I use speaque instead of speak, unstuque instead of unstuck?
I didnt want to be that hard nosed in correcting him :-)
keep up the good work bob.

oh PhD's make you so authoritative that you should strive for one.

PhD = post hole digger. they go really well on the power takeoff of
your average tractor :-) why my mate has two post hole diggers I'll
never know. :-)
Stealth Pilot

"Stealth Pilot" wrote

PhD = post hole digger. they go really well on the power takeoff of
your average tractor :-) why my mate has two post hole diggers I'll
never know. :-)

You need two of them, for when one is at the doctor's office.

You know, the PhD's office, for when it is broke! If it wasn't broke before
it went, it will be when it gets the bill! g
--
Jim in NC