High wings and structural strength

[Mxsmanic]

When I look at pictures of high-wing aircraft, I don't see anything
between the wings that would provide structural strength--in some
aircraft there's even a window in the top of the cockpit between the
wings. What provides rigidity and structural strength in high-wing
aircraft? I somehow expect a sturdy metal beam across the wings on
top to withstand the stresses put upon them, but instead they seem to
be glued onto the skin of the fuselage on either side. How do such
planes hold together?

--
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[Gig 601XL Builder]

"Mxsmanic" > wrote in message
...
> When I look at pictures of high-wing aircraft, I don't see anything
> between the wings that would provide structural strength--in some
> aircraft there's even a window in the top of the cockpit between the
> wings. What provides rigidity and structural strength in high-wing
> aircraft? I somehow expect a sturdy metal beam across the wings on
> top to withstand the stresses put upon them, but instead they seem to
> be glued onto the skin of the fuselage on either side. How do such
> planes hold together?
>

Come on Anthony your mister research. Look it up.

[Dylan Smith]

On 2006-11-22, Mxsmanic > wrote:
> When I look at pictures of high-wing aircraft, I don't see anything
> between the wings that would provide structural strength--in some
> aircraft there's even a window in the top of the cockpit between the
> wings. What provides rigidity and structural strength in high-wing
> aircraft? I somehow expect a sturdy metal beam across the wings on
> top to withstand the stresses put upon them, but instead they seem to
> be glued onto the skin of the fuselage on either side. How do such
> planes hold together?

Funnily enough, a sturdy metal beam across the fuselage (usually two -
one at the front, where the main spar attaches, and one at the rear).
Windows can still be put in the roof. For a light aircraft 'sturdy'
doesn't mean 'massive'.

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Mxsmanic]

Dylan Smith writes:

> Funnily enough, a sturdy metal beam across the fuselage (usually two -
> one at the front, where the main spar attaches, and one at the rear).
> Windows can still be put in the roof. For a light aircraft 'sturdy'
> doesn't mean 'massive'.

It sure is hard to see anything in photos.

Are high-wing designs stronger, weaker, or about the same as low-wing
designs? Do they have cost or safety advantages/disadvantages?

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[Matt Whiting]

T o d d P a t t i s t wrote:

> Mxsmanic > wrote:
>
>
>>Are high-wing designs stronger, weaker, or about the same as low-wing
>>designs?
>
>
> About the same.

Strut-braced high wing is more weight efficient for the same strength,
however. Withstanding the bending moments in a cantilever wing requires
a pretty massive spar and/or thick skins in the center 1/3 or so of
the wing.

Matt

[Mxsmanic]

Matt Whiting writes:

> Strut-braced high wing is more weight efficient for the same strength,
> however. Withstanding the bending moments in a cantilever wing requires
> a pretty massive spar and/or thick skins in the center 1/3 or so of
> the wing.

What materials are used for the spar in GA planes? I seem to recall
that large jets use titanium for the most critical structural
elements, but I presume that's too expensive for small planes (?).

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[karl gruber[_1_]]

The landing gear springs on my Cessna are titanium.

Karl
N185KG

"Mxsmanic" > wrote in message
...
> Matt Whiting writes:
>
>> Strut-braced high wing is more weight efficient for the same strength,
>> however. Withstanding the bending moments in a cantilever wing requires
>> a pretty massive spar and/or thick skins in the center 1/3 or so of
>> the wing.
>
> What materials are used for the spar in GA planes? I seem to recall
> that large jets use titanium for the most critical structural
> elements, but I presume that's too expensive for small planes (?).
>
> --
> Transpose mxsmanic and gmail to reach me by e-mail.

[BT]

Bolts to the spar carry through structure
BT

"Mxsmanic" > wrote in message
...
> When I look at pictures of high-wing aircraft, I don't see anything
> between the wings that would provide structural strength--in some
> aircraft there's even a window in the top of the cockpit between the
> wings. What provides rigidity and structural strength in high-wing
> aircraft? I somehow expect a sturdy metal beam across the wings on
> top to withstand the stresses put upon them, but instead they seem to
> be glued onto the skin of the fuselage on either side. How do such
> planes hold together?
>
> --
> Transpose mxsmanic and gmail to reach me by e-mail.

[Kev]

karl gruber wrote:
> The landing gear springs on my Cessna are titanium.

Holy smokes, I just read that those are over $11,000 a set !! Pardon
my asking, but I just have to know why someone would spend that much on
a set of Cessna legs. Is it a bush pilot kind of thing or do you
cycle landings every few hours or ????

Thanks!
Kev

[Newps]

Kev wrote:

> karl gruber wrote:
>
>>The landing gear springs on my Cessna are titanium.
>
>
> Holy smokes, I just read that those are over $11,000 a set !! Pardon
> my asking, but I just have to know why someone would spend that much on
> a set of Cessna legs.

Nobody does. They buy used. There's lots of them around.



Is it a bush pilot kind of thing or do you
> cycle landings every few hours or ????

Cycle landings every few hours?

[karl gruber[_1_]]

"Kev" > wrote in message
oups.com...
>
> karl gruber wrote:
>> The landing gear springs on my Cessna are titanium.
>
> Holy smokes, I just read that those are over $11,000 a set !! Pardon
> my asking, but I just have to know why someone would spend that much on
> a set of Cessna legs. Is it a bush pilot kind of thing or do you
> cycle landings every few hours or ????
>
> Thanks!
> Kev
>

Well, I bought the first set. At the time they were less than half the
present price. And, I got about half the rest from the sale of the original
steel gear. The cost of raw titanium has gone through the roof since then.

Maybe more money than brains, but they did cut 25 pounds off the empty
weight of my 185. Plus they look great and next to nobody has them.

And contrary to "news," there are no used ones out there. I doubt if more
than 10 ever sold and they've only been available for the past three years.

Someday some archeologist will come upon a pile of aluminum oxide with some
weird shiny new looking titanium springs sticking out and will wonder what
the hell is THAT?

Best,
Karl
"Curator" N185KG

[Kev]

karl gruber wrote:
> "Kev" > wrote in message
> oups.com...
> >
> > karl gruber wrote:
> >> The landing gear springs on my Cessna are titanium.
> >
> > Holy smokes, I just read that those are over $11,000 a set !! [...]
>
> Well, I bought the first set. At the time they were less than half the
> present price. And, I got about half the rest from the sale of the original
> steel gear. The cost of raw titanium has gone through the roof since then.
>
> Maybe more money than brains, but they did cut 25 pounds off the empty
> weight of my 185. Plus they look great and next to nobody has them.

Hmm. So about $100 per pound lost, which isn't too bad. Especially
compared to speed mods like gap seals etc, which cost what? $1000 per
mph gained? Something like that? It's been a while since I
researched that.

> Someday some archeologist will come upon a pile of aluminum oxide with
> some weird shiny new looking titanium springs sticking out and will wonder
> what the hell is THAT?

No kidding!

Thanks for the interesting reply,
Kev

[Jay Honeck]

> Maybe more money than brains, but they did cut 25 pounds off the empty
> weight of my 185. Plus they look great and next to nobody has them.

Whoa! That's actually a good deal, then. 25 pounds is a nice pick-up
in your useful load!

Although I gained five pounds back yesterday by having my old DME
yanked out of my panel -- AND the avionics shop bought it from me for
$150 bucks!

By golly, Atlas just LEAPED off the runway after having that old tooth
pulled...

;-)

Happy Thanksgiving!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Newps]

Kev wrote:


>
> Hmm. So about $100 per pound lost, which isn't too bad. Especially
> compared to speed mods like gap seals etc, which cost what? $1000 per
> mph gained? Something like that? It's been a while since I
> researched that.

Gap seals are dirt cheap. I can get gap seals for my ailerons that are
really just tape. Around $100 for the kit. Several companies sell gap
seals for the flaps of Cessna's. Maybe $300 for a typical 182.

[karl gruber[_1_]]

News,

Where do you get the "just tape" aileron gap seals?

Karl



"Newps" > wrote in message
. ..
>
>
> Kev wrote:
>
>
>>
>> Hmm. So about $100 per pound lost, which isn't too bad. Especially
>> compared to speed mods like gap seals etc, which cost what? $1000 per
>> mph gained? Something like that? It's been a while since I
>> researched that.
>
> Gap seals are dirt cheap. I can get gap seals for my ailerons that are
> really just tape. Around $100 for the kit. Several companies sell gap
> seals for the flaps of Cessna's. Maybe $300 for a typical 182.

[Kev]

Newps wrote:
> Kev wrote:
> >
> > Hmm. So about $100 per pound lost, which isn't too bad. Especially
> > compared to speed mods like gap seals etc, which cost what? $1000 per
> > mph gained? Something like that? It's been a while since I
> > researched that.
>
> Gap seals are dirt cheap. I can get gap seals for my ailerons that are
> really just tape. Around $100 for the kit. Several companies sell gap
> seals for the flaps of Cessna's. Maybe $300 for a typical 182.

Gap seals should be dirt cheap, but I can't find any for less that
$450, with 8 hours labor (another $500 at least), for about $1000
installed. Where are you finding a $100 legal kit?

Kev

[Ron Wanttaja]

On 23 Nov 2006 09:15:40 -0800, "Kev" > wrote:

>> Gap seals are dirt cheap. I can get gap seals for my ailerons that are
>> really just tape. Around $100 for the kit. Several companies sell gap
>> seals for the flaps of Cessna's. Maybe $300 for a typical 182.
>
>Gap seals should be dirt cheap, but I can't find any for less that
>$450, with 8 hours labor (another $500 at least), for about $1000
>installed. Where are you finding a $100 legal kit?

Mine cost $5 for a lifetime supply, at Lowes Aerospace. On Experimentals, at
least, we can just use duct tape. I replace it every three years or so, if it
looks like it's starting to separate.

Doesn't improve the speed (very little WOULD, in this airplane) but it increases
the aileron effectiveness.

Ron Wanttaja

[Newps]

Not being a Cessna guy anymore I don't recall which companies sold the
tape kits. Here's a few links for gap seals.

http://www.skywagons.com/modaddress.html

http://www.wicksaircraft.com/catalog/product_cat.php/subid=6407/index.html

Get with the Cessna Pilots Assoc and they'll help you out too. There
was always a lot of talk on the web board about these gap seals.




karl gruber wrote:

> News,
>
> Where do you get the "just tape" aileron gap seals?
>
> Karl

[karl gruber[_1_]]

I didn't think you could get them. Hey, I all over the net!

Karl


"Newps" > wrote in message
. ..
> Not being a Cessna guy anymore I don't recall which companies sold the
> tape kits. Here's a few links for gap seals.
>
> http://www.skywagons.com/modaddress.html
>
> http://www.wicksaircraft.com/catalog/product_cat.php/subid=6407/index.html
>
> Get with the Cessna Pilots Assoc and they'll help you out too. There was
> always a lot of talk on the web board about these gap seals.
>
>
>
>
> karl gruber wrote:
>
>> News,
>>
>> Where do you get the "just tape" aileron gap seals?
>>
>> Karl

[Brian[_1_]]

> What materials are used for the spar in GA planes? I seem to recall
> that large jets use titanium for the most critical structural
> elements, but I presume that's too expensive for small planes (?).
>
> --


Spars are usually made of Spruce,Aluminum, and Occasionally Magnesium
in most the stuff I fly.

Also I have flown several high wing aircraft where the wing root is
attached to the fuselage by two 1/4" bolt t on each wing. Given that
much of the load is actually carried through the Struts.

Brian

[[email protected]]

Mxsmanic wrote:
> Dylan Smith writes:
>
> > Funnily enough, a sturdy metal beam across the fuselage (usually two -
> > one at the front, where the main spar attaches, and one at the rear).
> > Windows can still be put in the roof. For a light aircraft 'sturdy'
> > doesn't mean 'massive'.
>
> It sure is hard to see anything in photos.
>
> Are high-wing designs stronger, weaker, or about the same as low-wing
> designs? Do they have cost or safety advantages/disadvantages?

*** On a strut-braced high wing airplane, the wing, the strut, and the
fuselage form a triangle, which is inherently a strong shape. With a
low-wing airplane, the same
loads have to be borne by a spar inside the wing. The lift is trying
to bend the
spar.

Another advantage of high-wing airplanes is that they require less
dihedral, because the fuselage center of gravity is below the wing.

OTOH, the struts are draggy. Don't know if they're more or less
draggy than
the thick wing root that you have to have without them.

- Jerry Kaidor

[[email protected]]

wrote:

> *** On a strut-braced high wing airplane, the wing, the strut, and the
> fuselage form a triangle, which is inherently a strong shape. With a
> low-wing airplane, the same
> loads have to be borne by a spar inside the wing. The lift is trying
> to bend the
> spar.
>
> Another advantage of high-wing airplanes is that they require less
> dihedral, because the fuselage center of gravity is below the wing.
>
> OTOH, the struts are draggy. Don't know if they're more or less
> draggy than
> the thick wing root that you have to have without them.
>

The struts are draggier. The strut generates drag, and the
attachment points generate even more; that's called "interference
drag." On a strut-braced low-wing that drag can foul up the boundary
layer pretty good.
The low-wing airplane's strut has to be more massive than the
high winger's because it has to resist buckling. Even then, "jury"
struts are often employed to maintain position of the centre of the
strut to prevent buckling under load. High-wing airplanes like the Cub
and Citabria have those jury struts as well to improve the negative G
figures.
Typical strut-braced low wing airplane:
http://images.google.ca/imgres?imgurl=http://avia.russian.ee/pictures/usa/cessna_188.jpg&imgrefurl=http://avia.russian.ee/air/usa/cessna_188.html&h=201&w=422&sz=30&hl=en&start=57&tbnid=QVPLVVHVM9vrKM:&tbnh=60&tbnw=126&prev=/images%3Fq%3DCessna%2B188%26start%3D40%26ndsp%3D20 %26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN

Another one:
http://1000aircraftphotos.com/Contributions/3520L-1.jpg

The cantilever wing isn't all that thick. The structure within it is
much heavier.
http://www.aircraftdoorseals.com/images/Cessna%20210.jpg