sliding wings?

wrote:


hi richard: could you possibly give me some numerical illustrations?
I am not sure where your numbers are coming from (17.2?, 295?), but
this is probably just my ignorance. obviously, going from 0 to 1 sqft
of wing is a useful weight/lift tradeoff... :-) is your point that the
current wing size (of any plane) is already the optimal weight/lift
tradeoff? strange that better materials over the last 50 years would
not have changed the optimum.

regards,

/iaw

I'll give it a try, but you owe me lunch now!


No, not trying to say that all wings are already optimal.
Especally for all missions.

Just that one must look carefully at
proposed performance gains / weight increase.

Write this down: "It's ALL about WEIGHT"

Material gains over the last 100(!) years have been amazing.
For instance, can you imagine a wooden 747
Think I'm kidding?
Check out this 600 passenger design proposal by Bel Geddess,
presented at the New Your Worlds Fair in 1940.
And it's a SPAN LOADER, too!

http://www.home.earthlink.net/~tp-1/ged.pdf




the mystery numbers?
Nothing mysterious here.
It's just arithmetic.

refer to page 25 of Aerodynamics for Naval Aviators

Anybody have a link to this?
It is an excellent starting point for basic aerodynamics.


Going back to...
L = Cl S q

This is the basic lift equasion (well, one of many forms)
Rearrange that equasion to solve for L, CL, S, or even q.

Cl is the coeffecient of lift that we are looking at.

S is Wing Surface Area is Sq Feet

q (rho) is dynamic pressure in pounds per square foot.
q = 1/2 density * velocity squared
Density in Slugs per cubic ft.
V in feet per second).

using q = (sigma V^2)/295 (V in knots, TAS)

295 is a conversion factor that converts FPS to knots

Greek leter Sigma is used for density ratio.
That's ambient pressure / standard day pressure
At sea level standard day, sigma is 1, and drops out.


L = Cl (Sigma V^2 /295) S

So if sigma is 1 then L = CL V^2 S / 295

then solving for V

V = 17.2 Sqrt(L / Cl Sigma S)

17.2 is ~ the square root of 295

Simplified for stall speed at sea level...

Vstall = 17.2 (WEIGHT / CLmax S) Since Lift = Weight

Stall speed implies Maximum Coeffeceint of Lift for a given airfoil.

We need as much lift as weight for straight and level flight,
So L = W = L (are the same)


Well, it's late and I'm bushed.
I've read that over several times, and now it doesn't make sense
to me either.

We'll do lunch another day, ok?

Richard

I couldn't find any links to an on-line copy of
"Aerodynamics for Naval Aviators".

But google did turn up a couple hundred links to
copies for sale. Prices range from about $10 to
just under $25.

("Richard Lamb" wrote)
[snip]
Material gains over the last 100(!) years have been amazing.
For instance, can you imagine a wooden 747
Think I'm kidding?
Check out this 600 passenger design proposal by Bel Geddess, presented at
the New Your Worlds Fair in 1940.
And it's a SPAN LOADER, too!


http://www.home.earthlink.net/~tp-1/ged.pdf
That's neat ...in a 1929 -1940 kind of way.


Montblack

Montblack wrote:

("Richard Lamb" wrote)
[snip]

Material gains over the last 100(!) years have been amazing.
For instance, can you imagine a wooden 747
Think I'm kidding?
Check out this 600 passenger design proposal by Bel Geddess, presented at
the New Your Worlds Fair in 1940.
And it's a SPAN LOADER, too!



http://www.home.earthlink.net/~tp-1/ged.pdf
That's neat ...in a 1929 -1940 kind of way.


Montblack

I particularly enjoyed the side by side comparison of the creature comforts.

Olde fashioned elegance New fangled jet
------------------------ ---------------

Main Lounge 36 ft high
9 decks 2 decks
3 Kitchens
13 pantries Peanuts
Library Bad movie
writing rooms
2 public dining rooms
The main dining room coverts into a dance floor for 100 couples
orchestra platform
3 private dining rooms capable of feeding 40 people
4 deck tennis courts
6 shuffle board courts
6 quoits pitches
library
writing room
1 gym with dressing rooms and showers 12 chemical toilets
1 men's Solarium w/16 couches and a masseur
1 women’s Solarium w/16 couches and a masseuse
1 children’s playroom
1 doctors office with waiting room
Barber shop
hairdressers salon
2 bars Bar cart
1 store
1 huge promenade deck
1 Veranda Cafe seats 90
18 single state rooms
81 double staterooms
24 suites w/ baths 606 seats w/ fold-down tables - 32" pitch
179 sleeping rooms
Air-conditioning Air-conditioning

"Richard Lamb" wrote

I particularly enjoyed the side by side comparison of the creature
comforts.

Being a mechanical kind of guy, I particularly enjoyed the "5 minute
inflight engine change capability," with the machine shop repairing the bad
one, and returning it to spares, (one of 6 extra) ready for return to duty.

Or how about sitting out on the sun deck for a while, during the 100 mph
flight? It would be easy to get burned, with that wind chill factor, no?
g
--
Jim in NC

I will be happy to take you to lunch when you are in RI and I am in
airport vicinity. I will even pay for the drink if you can answer the
following simple question. For 100 points and the jackpot... ;-)

An RV-10 has a span of about 32 ft, wing area of 148 sqft and a wing
loading of 18.6 lb/sqft. It cruises at around 190mph
(optimistically). It's stall speed is 57mph.

Let's presume its wings were telescopic---which of course they are not.
Let's presume that fully extended they are still what they are. Now
presume in full flight, I could take off 1/3 of the wing. For your 100
points, how does the expected stall and cruise speeds change? [For
extra credit, assume a reasonable weight increase. hmmm...how much
does an empty aluminum wing structure weigh? I guess this could even
be fabric---it would be used only during landing.]

regards,

/ivo

wrote:

I will be happy to take you to lunch when you are in RI and I am in
airport vicinity. I will even pay for the drink if you can answer the
following simple question. For 100 points and the jackpot... ;-)

An RV-10 has a span of about 32 ft, wing area of 148 sqft and a wing
loading of 18.6 lb/sqft. It cruises at around 190mph
(optimistically). It's stall speed is 57mph.

Let's presume its wings were telescopic---which of course they are not.
Let's presume that fully extended they are still what they are. Now
presume in full flight, I could take off 1/3 of the wing. For your 100
points, how does the expected stall and cruise speeds change? [For
extra credit, assume a reasonable weight increase. hmmm...how much
does an empty aluminum wing structure weigh? I guess this could even
be fabric---it would be used only during landing.]

regards,

/ivo


Grrrr.

Ok, but don't start the clock until I hit "send"?
You left out the weight. (I Tol' you to 'Write That Down!')

148 square feet on a 32 foot span implies a chord of 5.25 feet or 63 inches.

ASSUMING a gross weight of 2700 the 57 mph stall would imply a CLmax of 2.2.
(That has GOT to be flaps down!)

Removing 1/3 of the span (.666 * 32') leaves 23.3' span
23.3' span * 5.25' chord gives (111.888) call it 112 square feet.
Predicted stall speed (with these numbers) looks like 65 mph.

ADDING 1/3 to the span gives 42.6' span and 224 square feet area.
Predicted stall speed (with these numbers) looks like 46 mph.

A guess at cruise numbers would be foolish. Too many unknowns.
And no way to break the wing drag out of the overall without better info.

Would the short wing version fly faster?
Maybe - maybe NOT - because the short wing would be flying at a higher angle
of attack - with corresponding higher drag...

So - purest speculation....

Based on the above at cruise:
For the Van's wing, CL of .197. aoa ~ -1 degree. Cd ~ .0076
For the short wing, CL of .26 aoa ~ -1/2 degrees .0077
And the long wing, CL of .13 aoa ~ -1-1/3 degrees .008

And, most bizarre of all, the long wing version MIGHT even cruise FASTER!

HOwZaT?

By cruising at a higher altitude...
Up where the air is thinner and colder!



Ham and cheese on Rye, please?

Richard

Richard Lamb wrote:

wrote:

I will be happy to take you to lunch when you are in RI and I am in
airport vicinity. I will even pay for the drink if you can answer the
following simple question. For 100 points and the jackpot... ;-)

An RV-10 has a span of about 32 ft, wing area of 148 sqft and a wing
loading of 18.6 lb/sqft. It cruises at around 190mph
(optimistically). It's stall speed is 57mph.

Let's presume its wings were telescopic---which of course they are not.
Let's presume that fully extended they are still what they are. Now
presume in full flight, I could take off 1/3 of the wing. For your 100
points, how does the expected stall and cruise speeds change? [For
extra credit, assume a reasonable weight increase. hmmm...how much
does an empty aluminum wing structure weigh? I guess this could even
be fabric---it would be used only during landing.]

regards,

/ivo


Grrrr.

Ok, but don't start the clock until I hit "send"?
You left out the weight. (I Tol' you to 'Write That Down!')

148 square feet on a 32 foot span implies a chord of 5.25 feet or 63
inches.

ASSUMING a gross weight of 2700 the 57 mph stall would imply a CLmax of
2.2.
(That has GOT to be flaps down!)

Removing 1/3 of the span (.666 * 32') leaves 23.3' span
23.3' span * 5.25' chord gives (111.888) call it 112 square feet.
Predicted stall speed (with these numbers) looks like 65 mph.

ADDING 1/3 to the span gives 42.6' span and 224 square feet area.
Predicted stall speed (with these numbers) looks like 46 mph.

A guess at cruise numbers would be foolish. Too many unknowns.
And no way to break the wing drag out of the overall without better info.

Would the short wing version fly faster?
Maybe - maybe NOT - because the short wing would be flying at a higher
angle
of attack - with corresponding higher drag...

So - purest speculation....

Based on the above at cruise:
For the Van's wing, CL of .197. aoa ~ -1 degree. Cd ~ .0076
For the short wing, CL of .26 aoa ~ -1/2 degrees .0077
And the long wing, CL of .13 aoa ~ -1-1/3 degrees .008

And, most bizarre of all, the long wing version MIGHT even cruise FASTER!

HOwZaT?

By cruising at a higher altitude...
Up where the air is thinner and colder!



Ham and cheese on Rye, please?

Richard



Oh yes! As for the weight increase question...

It's still 2700 pounds gross, but it's a two seater now...


Richard

the german expression when one is not getting something is that one is
standing on the (phone) line, which is why nothing is coming in. so, I

am still trying to figure out what you were computing.

putting your posts together, if you instruct engineers, some examples
with units would be helpful. (take this from someone who teaches
financial economics for a living.)

Vstall = 17.2 (WEIGHT / CLmax S) Since Lift = Weight

I believe CLmax and S are both under the division, because more S
should give me lower stall speed. Now, your recent post tells me that
CLmax = 2.2 . hmmm, this would lead me to plug in

57mph = 50 knots =?=?= 17.2 * (2700 lbs / [2.2 * 112sqft])

(I don't know the units on 17.2 or 2.2.)

so, the clock is still ticking... ;-).