The Murphy Builders Site

Hi Folks

We have been working on the wing structure and have a question about the leading
edge spar and how it affects installation of the leading edge skin. Our kit is
an Elite but this should apply to any high gross Rebel and probably any Rebel
except the SR. I believe the wing structure at the leading edge is the same.

Looking at the leading edge ribs and front spar, it looks like when the skin is
installed it will need to pull the flanges of the front spar out to meet the
skin (as if the spar was not wide enough). I say this because when I wrap a
strip of sheet metal formed to the shape of the skin around the ribs it clears
the spar flanges by a significant amount. It looks like the spar would have to
be pulled out to match the profile of the skin. Is this normal? Does the thick
high gross skin pull the spar out to match it and not leave funny dimples when
the skin is riveted in place?

As a check of my method, what is the distance (in the horizontal plane) from the
front face of the spar to the most forward point of the leading edge skin on the
inside of the skin (the inside face of the skin fartherst from the spar)? I get
15/16" (.937").

As a follow on question, if the ribs and the front spar are not perfectly
aligned (spar to rib, vertically) does the skin pull the spar in place nicely
and not affect the profile of the leading edge skin?

Thanks

Dave R.
Elite 583


--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8





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Hi David

My leading edge extends approx. 0.95" forward of the fwd spar about like
yours and fits just fine. It also fit fine prior to riveting as long as
there was a cleco in most every hole.

If the rib protrudes farther than the leading edge spar (vertically) it
will leave a bump in the leading edge at each rib after riveting so you
may wish to correct this if you can. It doesn't seem to matter much if
the spar flange is a little higher than the rib though. I was very picky
about bending the flanges of the ribs to match the leading edge as best
I could but I did not bend the forward spar flanges at all.

Ken

David Ricker wrote:

Hi Folks

We have been working on the wing structure and have a question about the leading
edge spar and how it affects installation of the leading edge skin. Our kit is
an Elite but this should apply to any high gross Rebel and probably any Rebel
except the SR. I believe the wing structure at the leading edge is the same.

Looking at the leading edge ribs and front spar, it looks like when the skin is
installed it will need to pull the flanges of the front spar out to meet the
skin (as if the spar was not wide enough). I say this because when I wrap a
strip of sheet metal formed to the shape of the skin around the ribs it clears
the spar flanges by a significant amount. It looks like the spar would have to
be pulled out to match the profile of the skin. Is this normal? Does the thick
high gross skin pull the spar out to match it and not leave funny dimples when
the skin is riveted in place?

As a check of my method, what is the distance (in the horizontal plane) from the
front face of the spar to the most forward point of the leading edge skin on the
inside of the skin (the inside face of the skin fartherst from the spar)? I get
15/16" (.937").

As a follow on question, if the ribs and the front spar are not perfectly
aligned (spar to rib, vertically) does the skin pull the spar in place nicely
and not affect the profile of the leading edge skin?

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Thanks Ken

The bumps are exactly what I am concerned about or vice versa dips along the front
spar line where the skin would be trying to pull it up in place since the front spar
doesn't seem wide enough (vertically). I am concerned that it would be necessary to
re-shape the ribs to meet the spar, it would seem to me that they should be right
straight from the factory.

Has any one else come across this issue and how did you deal with it or is it a
problem at all? Wayne, is this something you have seen in the bunch of wings you have
built?

Thanks

Dave R.

klehman@albedo.net wrote:

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Hi David

My leading edge extends approx. 0.95" forward of the fwd spar about like
yours and fits just fine. It also fit fine prior to riveting as long as
there was a cleco in most every hole.

If the rib protrudes farther than the leading edge spar (vertically) it
will leave a bump in the leading edge at each rib after riveting so you
may wish to correct this if you can. It doesn't seem to matter much if
the spar flange is a little higher than the rib though. I was very picky
about bending the flanges of the ribs to match the leading edge as best
I could but I did not bend the forward spar flanges at all.

Ken

David Ricker wrote:

Hi Folks

We have been working on the wing structure and have a question about the leading
edge spar and how it affects installation of the leading edge skin. Our kit is
an Elite but this should apply to any high gross Rebel and probably any Rebel
except the SR. I believe the wing structure at the leading edge is the same.

Looking at the leading edge ribs and front spar, it looks like when the skin is
installed it will need to pull the flanges of the front spar out to meet the
skin (as if the spar was not wide enough). I say this because when I wrap a
strip of sheet metal formed to the shape of the skin around the ribs it clears
the spar flanges by a significant amount. It looks like the spar would have to
be pulled out to match the profile of the skin. Is this normal? Does the thick
high gross skin pull the spar out to match it and not leave funny dimples when
the skin is riveted in place?

As a check of my method, what is the distance (in the horizontal plane) from the
front face of the spar to the most forward point of the leading edge skin on the
inside of the skin (the inside face of the skin fartherst from the spar)? I get
15/16" (.937").

As a follow on question, if the ribs and the front spar are not perfectly
aligned (spar to rib, vertically) does the skin pull the spar in place nicely
and not affect the profile of the leading edge skin?

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--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada




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----- Original Message -----
From: "Wayne G. O'Shea" <oifa@irishfield.on.ca>
To: "David Ricker" <ricker@dbis.ns.ca>
Sent: Monday, May 07, 2001 10:31 PM
Subject: Re: Wing Leading Edge Question

Dave, the first thing of course is to make sure the rib is fitted properly
to the front spar. It only takes a little bit of misplacement to get that
hump in the skin (of course if they are already drilled/riveted/etc, you
will have to work with what you have). It is not so much the rib flange
being centered (due to different "approach" angles from rib to spar, top

and

bottom), as it is smooth flow to the front spar from the rib flanges. I

like

to use 2 spring clamps on each rib to align the front spar. I clip them
sideways to hold the rib flange and spar flange together for a smooth
transition top and bottom. I have found on a few wings that it was

necessary

to "caress" the forward "point" (the front corner on the bend line from

rib

face to rib flange) of the leading edge rib flanges down. I use a small
bucking bar and a small ball peen hammer to just roll the point down a bit
to smooth the transition. IF you are seeing a small stress point at each

rib

flange when you push the leading edge down over the spar, you need to peen
these points down a bit, as when riveted they only get worse! Look at most
flying Rebels and you will see these "proud points" at most of the top
leading edge rib flanges forward most location (even mine, but we learn as
we go!). Shouldn't be as much of a problem for you with the .032 leading
edge skin, as compared to the Rebel's .020 skin, although I did have to
round off (peen) a few flanges on the SR2500 wings I did to get a nice

fit!

If that doesn't work then your front spar was bent to narrow between
flanges!

Regards,
Wayne G. O'Shea
www.irishfield.on.ca

----- Original Message -----
From: "David Ricker" <ricker@dbis.ns.ca>
To: <murphy-rebel@dcsol.com>
Sent: Monday, May 07, 2001 9:53 PM
Subject: Re: Wing Leading Edge Question

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Thanks Ken

The bumps are exactly what I am concerned about or vice versa dips along

the front

spar line where the skin would be trying to pull it up in place since

the

front spar

doesn't seem wide enough (vertically). I am concerned that it would be

necessary to

re-shape the ribs to meet the spar, it would seem to me that they should

be right

straight from the factory.

Has any one else come across this issue and how did you deal with it or

is

it a

problem at all? Wayne, is this something you have seen in the bunch of

wings you have

built?

Thanks

Dave R.

klehman@albedo.net wrote:

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Hi David

My leading edge extends approx. 0.95" forward of the fwd spar about

like

yours and fits just fine. It also fit fine prior to riveting as long

as

there was a cleco in most every hole.

If the rib protrudes farther than the leading edge spar (vertically)

it

will leave a bump in the leading edge at each rib after riveting so

you

may wish to correct this if you can. It doesn't seem to matter much if
the spar flange is a little higher than the rib though. I was very

picky

about bending the flanges of the ribs to match the leading edge as

best

I could but I did not bend the forward spar flanges at all.

Ken

David Ricker wrote:

the leading

Our kit is

any Rebel

the same.

the skin is

meet the

I

wrap a

it clears

would have to

Does

the thick

dimples when

plane) from the

skin on the

spar)? I get

perfectly

place

nicely

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--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada

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Hi all,
This was touched on at least once before that I've found in the archives.

I got the slight "proud" bumps at the front of the LE ribs where they end
before the front spar, on top. I had looked for this possibility before riveting
the LE on, and tapped over a few rib flanges, but now that it is done, I can
see some bumps even so. I don't spose there is anything that can be done
(within reason) now that the LE is riveted on?
-Ben /496R



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I thought I had reformed the flanges enough to take care of that too but
nevertheless some minor bumps showed up.

I suppose it could be an excuse to add Angus's drooped leading edge STOL
kit ;)

Ken


bransom@dcsol.com wrote:

Hi all,
This was touched on at least once before that I've found in the archives.

I got the slight "proud" bumps at the front of the LE ribs where they end
before the front spar, on top. I had looked for this possibility before riveting
the LE on, and tapped over a few rib flanges, but now that it is done, I can
see some bumps even so. I don't spose there is anything that can be done
(within reason) now that the LE is riveted on?
-Ben /496R

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Ah well, yeah, mine aren't too bad either. Just seeing them as I walked by
for a couple weeks I thought I'd ask if there was any magic to make them go
away. Yes, Angus' cuffs occurred to me too. :) I even thought about
tapping one with a hammer, but I think it would take more than a tap and
lead to bad news. Time to proseal a tank I guess.
-Ben

I thought I had reformed the flanges enough to take care of that too but
nevertheless some minor bumps showed up.

I suppose it could be an excuse to add Angus's drooped leading edge STOL
kit ;)

Ken


bransom@dcsol.com wrote:

Hi all,
This was touched on at least once before that I've found in the archives.

I got the slight "proud" bumps at the front of the LE ribs where they end
before the front spar, on top. I had looked for this possibility before

riveting

the LE on, and tapped over a few rib flanges, but now that it is done, I

can

see some bumps even so. I don't spose there is anything that can be

done

(within reason) now that the LE is riveted on?
-Ben /496R

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