A Bush C150? With Leading Edge Slats?

[[email protected]]

Hello, I have a long term goal of making a small bush plane: 450lbs
useful load, 35mph clean stall, 600 ft clear 50ft. I know there are
quite a few designs out there, PA-11 Cub, Bushcaddy, Zenith CH701 to
name a few that I'm kind of familiar. But here, I'm looking into the
possiblity of working it out on a c150.

First of all, I want to say that this C150 will have a much lower
gross when used for bush flying, I know it'll be 1400# with no mods
but I like to see if I could push it down to 1300#. And now I want to
tackle on one aspect this time, how to improve the wings to
significantly reduce the stall speed.

First a question, anyone knows how far away the C150 wings is from an
ideal high lift design, i.e., if you would design it again (keep the
area and weigh the same and also conventional shape etc) how much can
you lower the stall speed?

I'm guessing for a certain design the stall speed is proportional to
the square root of the wingloading. The stock C150 is 10lb/ft^2 and
stalls at 48mph, while, for example, it is 8.9 and 30mph for the
Bushcaddy R120. So if I trust the number, the wings for the Bushcaddy
must be way more more efficient than that of the C150. What's the deal
here?

Now the CH701 is interesting that it has a leading edge slats. I'm
wondering how much improvement you can make if you put one set on the
C150 wings? As far as I know, there is noboby working on that. (I'm
aware of the Dakota slotted wing for the Cubs.) But it does not look
like too difficult. Any slats expert here?

Oh, let's not worry about the FAA part for now. :)

Thanks,

Jizhong

[Kevin Horton]

On Sat, 22 May 2004 19:38:56 -0700, jizhonghe wrote:

> I'm guessing for a certain design the stall speed is proportional to the
> square root of the wingloading. The stock C150 is 10lb/ft^2 and stalls at
> 48mph, while, for example, it is 8.9 and 30mph for the Bushcaddy R120. So
> if I trust the number, the wings for the Bushcaddy must be way more more
> efficient than that of the C150. What's the deal here?

The airspeed of interest for this calculation is equivalent airspeed,
although that is almost exactly the same as calibrated airspeed at low
speeds and altitudes. But the BushCaddy stall speeds are almost certainly
indicated airspeeds, as kit aircraft companies rarely have the resources
to determine the airspeed position error. Indicated stall speeds are
almost always lower than calibrated stall speeds, so they like to quote
the lower number.

Bottomline - the BushCaddy might very well have an indicated stall speed
near 30 mph (there web site claims 32 mph, but it isn't clear whether this
is power off or power on), but the calibrated stall speed would almost
certainly be higher than that.

For example, the C182Q POH that I am looking at shows a full flap, power
off stall speeds of 38 kt IAS which equals 50 kt CAS. With flaps up, the
error is even larger - 41 kt IAS = 56 kt CAS.

Don't pay too much attention to quoted stall speeds unless you have
proof that they are calibrated airspeeds.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[[email protected]]

Great. Thanks for the clarificaiton. I always thought they just give
you a low number. Now I know at least they are honest albeit
misleading. So I looked up the C152 POH and the CAS stall clean is
actually 47kts (54mph). I should re-adjust my goal. I think a CAS of
40mph should be quite respectable for a little bush plane. And the
square of (54/40)^2=1.83 with the light weight should be able to
reduce the T/O run by half.

Anyone know what's the calibrated clean stall for a PA-11 Cub?

Jizhong
On Sun, 23 May 2004 02:01:56 GMT, Kevin Horton > wrote:

>On Sat, 22 May 2004 19:38:56 -0700, jizhonghe wrote:
>
>> I'm guessing for a certain design the stall speed is proportional to the
>> square root of the wingloading. The stock C150 is 10lb/ft^2 and stalls at
>> 48mph, while, for example, it is 8.9 and 30mph for the Bushcaddy R120. So
>> if I trust the number, the wings for the Bushcaddy must be way more more
>> efficient than that of the C150. What's the deal here?
>
>The airspeed of interest for this calculation is equivalent airspeed,
>although that is almost exactly the same as calibrated airspeed at low
>speeds and altitudes. But the BushCaddy stall speeds are almost certainly
>indicated airspeeds, as kit aircraft companies rarely have the resources
>to determine the airspeed position error. Indicated stall speeds are
>almost always lower than calibrated stall speeds, so they like to quote
>the lower number.
>
>Bottomline - the BushCaddy might very well have an indicated stall speed
>near 30 mph (there web site claims 32 mph, but it isn't clear whether this
>is power off or power on), but the calibrated stall speed would almost
>certainly be higher than that.
>
>For example, the C182Q POH that I am looking at shows a full flap, power
>off stall speeds of 38 kt IAS which equals 50 kt CAS. With flaps up, the
>error is even larger - 41 kt IAS = 56 kt CAS.
>
>Don't pay too much attention to quoted stall speeds unless you have
>proof that they are calibrated airspeeds.

[Bushy]

Go and get a "Texas Taildragger" C 150 conversion. Maybe even an aerobatic
one.....

You don't really want a C150 nosewheel to hit a rabbit hole.....

Hope this helps,
Peter

[[email protected]]

Oh yes that's for sure (and big fat tires). Like I said, for now, I
just want to focus on the wing. Do you know if I'm going to save some
weight with the conversion?

Jizhong
On Sun, 23 May 2004 13:45:19 +1000, "Bushy" >
wrote:

>Go and get a "Texas Taildragger" C 150 conversion. Maybe even an aerobatic
>one.....
>
>You don't really want a C150 nosewheel to hit a rabbit hole.....
>
>Hope this helps,
>Peter
>

[Richard Lamb]

wrote:
>
> Oh yes that's for sure (and big fat tires). Like I said, for now, I
> just want to focus on the wing. Do you know if I'm going to save some
> weight with the conversion?
>
> Jizhong

A better starting question might be "do you know what you are doing"?

[Morgans]

"Richard Lamb" > wrote in message
...
> wrote:
> >
> > Oh yes that's for sure (and big fat tires). Like I said, for now, I
> > just want to focus on the wing. Do you know if I'm going to save some
> > weight with the conversion?
> >
> > Jizhong
>
> A better starting question might be "do you know what you are doing"?

I didn't want to ask that first, but now that you did....

Conventional wisdom says that adding any extra systems, such as slats, will
not save any weight, but rather, add weight. You were talking about taking
away some substantial weight, right? Where is that coming from?

Doubtful that the airfoil would be the right one to take full advantage of
slats, either. It is also likely even more weight would have to be added to
the wing structure to handle the extra lift, if you got the slats to work.

You dismissed the getting around the FAA, like it was of little consequence.
It is not, and might be the greatest hurdle to jump.

Things that make you go "hummm."
--
Jim in NC


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
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[Richard Riley]

On Sun, 23 May 2004 11:21:43 -0400, "Morgans"
> wrote:

:
:"Richard Lamb" > wrote in message
...
:> wrote:
:> >
:> > Oh yes that's for sure (and big fat tires). Like I said, for now, I
:> > just want to focus on the wing. Do you know if I'm going to save some
:> > weight with the conversion?
:> >
:> > Jizhong
:>
:> A better starting question might be "do you know what you are doing"?
:
:I didn't want to ask that first, but now that you did....
:
:Conventional wisdom says that adding any extra systems, such as slats, will
:not save any weight, but rather, add weight. You were talking about taking
:away some substantial weight, right? Where is that coming from?

Yep.
:
:Doubtful that the airfoil would be the right one to take full advantage of
:slats, either. It is also likely even more weight would have to be added to
:the wing structure to handle the extra lift, if you got the slats to work.
:
:You dismissed the getting around the FAA, like it was of little consequence.
:It is not, and might be the greatest hurdle to jump.

If he's not doing it in the US, FAA would be of no consequence.
Though in most areas, the local authority makes dealing with FAA look
like a walk in the park.

I'd think it'd be better to look at STOL wing tips and vortex
generators. Or look at one of these http://tinyurl.com/37tws

[[email protected]]

On Sun, 23 May 2004 15:07:11 GMT, Richard Lamb >
wrote:

wrote:
>>
>> Oh yes that's for sure (and big fat tires). Like I said, for now, I
>> just want to focus on the wing. Do you know if I'm going to save some
>> weight with the conversion?
>>
>> Jizhong
>
>A better starting question might be "do you know what you are doing"?

I know what I'm asking. :) It's a difference between starting doing
something and discussing something.

[[email protected]]

On Sun, 23 May 2004 11:21:43 -0400, "Morgans"
> wrote:

>
>"Richard Lamb" > wrote in message
...
>> wrote:
>> >
>> > Oh yes that's for sure (and big fat tires). Like I said, for now, I
>> > just want to focus on the wing. Do you know if I'm going to save some
>> > weight with the conversion?
>> >
>> > Jizhong
>>
>> A better starting question might be "do you know what you are doing"?
>
>I didn't want to ask that first, but now that you did....
>
>Conventional wisdom says that adding any extra systems, such as slats, will
>not save any weight, but rather, add weight. You were talking about taking
>away some substantial weight, right? Where is that coming from?
>

I was asking what the tailwheel conversion would do to the weight.
This has been done a lot and I think someone here might know.

>Doubtful that the airfoil would be the right one to take full advantage of
>slats, either. It is also likely even more weight would have to be added to
>the wing structure to handle the extra lift, if you got the slats to work.
>
>You dismissed the getting around the FAA, like it was of little consequence.
>It is not, and might be the greatest hurdle to jump.
>
>Things that make you go "hummm."

[[email protected]]

On Sun, 23 May 2004 08:42:50 -0700, Richard Riley
> wrote:

>On Sun, 23 May 2004 11:21:43 -0400, "Morgans"
> wrote:
>
>:
>:"Richard Lamb" > wrote in message
...
>:> wrote:
>:> >
>:> > Oh yes that's for sure (and big fat tires). Like I said, for now, I
>:> > just want to focus on the wing. Do you know if I'm going to save some
>:> > weight with the conversion?
>:> >
>:> > Jizhong
>:>
>:> A better starting question might be "do you know what you are doing"?
>:
>:I didn't want to ask that first, but now that you did....
>:
>:Conventional wisdom says that adding any extra systems, such as slats, will
>:not save any weight, but rather, add weight. You were talking about taking
>:away some substantial weight, right? Where is that coming from?
>
>Yep.
>:
>:Doubtful that the airfoil would be the right one to take full advantage of
>:slats, either. It is also likely even more weight would have to be added to
>:the wing structure to handle the extra lift, if you got the slats to work.
>:
>:You dismissed the getting around the FAA, like it was of little consequence.
>:It is not, and might be the greatest hurdle to jump.
>
>If he's not doing it in the US, FAA would be of no consequence.
>Though in most areas, the local authority makes dealing with FAA look
>like a walk in the park.
>

Yes, the "doing" will definitely not be in the US. By the way, I
thought I'm in the R.A.H. Where is the "spirit"?

>I'd think it'd be better to look at STOL wing tips and vortex
>generators. Or look at one of these http://tinyurl.com/37tws

I'm really asking about the possibility of a slats'd wing. I guess
nobody is working on that. But really nobody else interested in a bush
150?

[Kevin Horton]

On Sat, 22 May 2004 21:04:20 -0700, jizhonghe wrote:

> Great. Thanks for the clarificaiton. I always thought they just give you a
> low number. Now I know at least they are honest albeit misleading. So I
> looked up the C152 POH and the CAS stall clean is actually 47kts (54mph).
> I should re-adjust my goal. I think a CAS of 40mph should be quite
> respectable for a little bush plane. And the square of (54/40)^2=1.83 with
> the light weight should be able to reduce the T/O run by half.
>

The stall speed basically depends on the wing loading and the maximum
coefficient of lift that is achieved.

The stall speed in equivalent airspeed (which can be considered to be the
same as calibrated airspeed for low speed and low altitude) is:

VS = 0.8379 * sqrt(wing loading/CLmax)

VS is in knots,
Wing loading is in lb/sq. ft

I don't have data for the C150 at hand, but looking at the C182Q POH for
an example, I get wing loading of 2950/174 = 16.95 lb/sq ft. The forward
CG stall speed at 2950 lb is 54 kt CAS. This requires a CLmax of 1.72,
which is about what I would expect for a flapped wing with no leading edge
devices.

Several references indicate a well designed slat might give about an extra
1.0 CLmax, so you might be able to get the C182 CLmax to about 2.7. This
would give a stall speed of about 43 kt CAS, or about 80% of the original
value. You think you can get the C150 stall speed from 54 mph to 40 mph,
which would be a reduction to 74% of the original value. This seems
unlikely from just adding slats. You would need to also make a big
improvement to the flaps. These mods add weight, and they would require a
lot of knowledge of aerodynamics and structural engineering to actually
achieve the predicted performance, and to have a strong structure.

References:

Fluid Dynamic Lift, Hoerner
Theory of Wing Sections, Abbott and Doenhoff

Good luck.

[[email protected]]

Kevin,

There must be some typo in your formular. I looked up my book (Design
for Fly) and is something like:

V=16.2*sqrt(WL/Cl)

The book also states that the Cl for a Fowler flap could be 2.8
compared with 1.4 of no flap. So if I take your number of +1.0 for the
LES(leading edge slats), I think a Cl of 3.0 seems reasonable with
some flap.

Also remember my gross is reduced by almost 20% (not considering the
increase due to the additional slats because I don't how much more
weight) and the increase of the wing area by about 10%. For stock
C150, the wing loading is almost exactly 10 and V stall clean is
47kts. This will give a Cl of only about 1.2. Oh well. Anyway if we
use Cl=3 and wing loading of 7 let's see what we get:

V=16.2*sqrt(7/3)= 24.7 kts

Wow. Geez! I'm sure at 30mph the formula might break (or Cl will
change) but anyway, I still think 40mph is not that unreachable.

Jizhong

On Sun, 23 May 2004 16:58:25 GMT, Kevin Horton > wrote:

>On Sat, 22 May 2004 21:04:20 -0700, jizhonghe wrote:
>
>> Great. Thanks for the clarificaiton. I always thought they just give you a
>> low number. Now I know at least they are honest albeit misleading. So I
>> looked up the C152 POH and the CAS stall clean is actually 47kts (54mph).
>> I should re-adjust my goal. I think a CAS of 40mph should be quite
>> respectable for a little bush plane. And the square of (54/40)^2=1.83 with
>> the light weight should be able to reduce the T/O run by half.
>>
>
>The stall speed basically depends on the wing loading and the maximum
>coefficient of lift that is achieved.
>
>The stall speed in equivalent airspeed (which can be considered to be the
>same as calibrated airspeed for low speed and low altitude) is:
>
>VS = 0.8379 * sqrt(wing loading/CLmax)
>
>VS is in knots,
>Wing loading is in lb/sq. ft
>
>I don't have data for the C150 at hand, but looking at the C182Q POH for
>an example, I get wing loading of 2950/174 = 16.95 lb/sq ft. The forward
>CG stall speed at 2950 lb is 54 kt CAS. This requires a CLmax of 1.72,
>which is about what I would expect for a flapped wing with no leading edge
>devices.
>
>Several references indicate a well designed slat might give about an extra
>1.0 CLmax, so you might be able to get the C182 CLmax to about 2.7. This
>would give a stall speed of about 43 kt CAS, or about 80% of the original
>value. You think you can get the C150 stall speed from 54 mph to 40 mph,
>which would be a reduction to 74% of the original value. This seems
>unlikely from just adding slats. You would need to also make a big
>improvement to the flaps. These mods add weight, and they would require a
>lot of knowledge of aerodynamics and structural engineering to actually
>achieve the predicted performance, and to have a strong structure.
>
>References:
>
>Fluid Dynamic Lift, Hoerner
>Theory of Wing Sections, Abbott and Doenhoff
>
>Good luck.

[[email protected]]

I know I might get rediculous drag:

the induced drag C_Di = C_L^2/(Pi*AR)

On Sun, 23 May 2004 10:51:27 -0700, wrote:

>
>Kevin,
>
>There must be some typo in your formular. I looked up my book (Design
>for Fly) and is something like:
>
>V=16.2*sqrt(WL/Cl)
>
>The book also states that the Cl for a Fowler flap could be 2.8
>compared with 1.4 of no flap. So if I take your number of +1.0 for the
>LES(leading edge slats), I think a Cl of 3.0 seems reasonable with
>some flap.
>
>Also remember my gross is reduced by almost 20% (not considering the
>increase due to the additional slats because I don't how much more
>weight) and the increase of the wing area by about 10%. For stock
>C150, the wing loading is almost exactly 10 and V stall clean is
>47kts. This will give a Cl of only about 1.2. Oh well. Anyway if we
>use Cl=3 and wing loading of 7 let's see what we get:
>
>V=16.2*sqrt(7/3)= 24.7 kts
>
>Wow. Geez! I'm sure at 30mph the formula might break (or Cl will
>change) but anyway, I still think 40mph is not that unreachable.
>
>Jizhong
>
>On Sun, 23 May 2004 16:58:25 GMT, Kevin Horton > wrote:
>
>>On Sat, 22 May 2004 21:04:20 -0700, jizhonghe wrote:
>>
>>> Great. Thanks for the clarificaiton. I always thought they just give you a
>>> low number. Now I know at least they are honest albeit misleading. So I
>>> looked up the C152 POH and the CAS stall clean is actually 47kts (54mph).
>>> I should re-adjust my goal. I think a CAS of 40mph should be quite
>>> respectable for a little bush plane. And the square of (54/40)^2=1.83 with
>>> the light weight should be able to reduce the T/O run by half.
>>>
>>
>>The stall speed basically depends on the wing loading and the maximum
>>coefficient of lift that is achieved.
>>
>>The stall speed in equivalent airspeed (which can be considered to be the
>>same as calibrated airspeed for low speed and low altitude) is:
>>
>>VS = 0.8379 * sqrt(wing loading/CLmax)
>>
>>VS is in knots,
>>Wing loading is in lb/sq. ft
>>
>>I don't have data for the C150 at hand, but looking at the C182Q POH for
>>an example, I get wing loading of 2950/174 = 16.95 lb/sq ft. The forward
>>CG stall speed at 2950 lb is 54 kt CAS. This requires a CLmax of 1.72,
>>which is about what I would expect for a flapped wing with no leading edge
>>devices.
>>
>>Several references indicate a well designed slat might give about an extra
>>1.0 CLmax, so you might be able to get the C182 CLmax to about 2.7. This
>>would give a stall speed of about 43 kt CAS, or about 80% of the original
>>value. You think you can get the C150 stall speed from 54 mph to 40 mph,
>>which would be a reduction to 74% of the original value. This seems
>>unlikely from just adding slats. You would need to also make a big
>>improvement to the flaps. These mods add weight, and they would require a
>>lot of knowledge of aerodynamics and structural engineering to actually
>>achieve the predicted performance, and to have a strong structure.
>>
>>References:
>>
>>Fluid Dynamic Lift, Hoerner
>>Theory of Wing Sections, Abbott and Doenhoff
>>
>>Good luck.

[Kevin Horton]

On Sun, 23 May 2004 11:51:27 -0700, jizhonghe wrote:

>
> Kevin,
>
> There must be some typo in your formular. I looked up my book (Design for
> Fly) and is something like:
>
> V=16.2*sqrt(WL/Cl)

Whoops, I accidentally left the sea level density out of that conversion
factor. Once I move the sea level density inside the conversion factor, I
get:

VS = 17.18*sqrt(WL/CLmax)

Thanks for pointing that out.

Are you sure your book says 16.2 and not 17.2? Otherwise I'm not sure
where the difference is.

>
> The book also states that the Cl for a Fowler flap could be 2.8 compared
> with 1.4 of no flap. So if I take your number of +1.0 for the LES(leading
> edge slats), I think a Cl of 3.0 seems reasonable with some flap.

A Clmax of 3 is achievable with complex, multi-sloted flaps and slats.
But you likely won't achieve such a CL unless you have the means to do
lots of wind tunnel and/or development flight te$ting.

See:

http://adg.stanford.edu/aa241/highlift/highliftintro.html

>
> Also remember my gross is reduced by almost 20% (not considering the
> increase due to the additional slats because I don't how much more
> weight) and the increase of the wing area by about 10%.

A basic C150 doesn't have very much useful load at the stock gross weight.
What useful load do you require for your mission? Exactly how do you
plan to reduce the empty weight, while increasing wing area and adding
slats and complex multi-slotted flaps?

> For stock C150,
> the wing loading is almost exactly 10 and V stall clean is 47kts. This
> will give a Cl of only about 1.2. Oh well. Anyway if we use Cl=3 and
> wing loading of 7 let's see what we get:
>
> V=16.2*sqrt(7/3)= 24.7 kts
>
> Wow. Geez! I'm sure at 30mph the formula might break (or Cl will change)
> but anyway, I still think 40mph is not that unreachable.

Let me know when you've got some credible flight test results, showing
calibrated airspeeds at the stall of 40 mph at a useful gross weight.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[Richard Isakson]

> wrote ...
> I'm really asking about the possibility of a slats'd wing. I guess
> nobody is working on that. But really nobody else interested in a bush
> 150?

Slats work by increasing the maximum angle of attack that the wing will
achieve before the wing stalls. On the ground the Cessna 150 is
geometrically limited to it's current max AOA. For your project to work it
would need Storch-like maingear but you'll lose all of your forward
visibility.

Rich

[Blueskies]

Unless you set up a variable AOA wing...

--
Dan D.
http://www.ameritech.net/users/ddevillers/start.html


..
"Richard Isakson" > wrote in message ...
> > wrote ...
> > I'm really asking about the possibility of a slats'd wing. I guess
> > nobody is working on that. But really nobody else interested in a bush
> > 150?
>
> Slats work by increasing the maximum angle of attack that the wing will
> achieve before the wing stalls. On the ground the Cessna 150 is
> geometrically limited to it's current max AOA. For your project to work it
> would need Storch-like maingear but you'll lose all of your forward
> visibility.
>
> Rich
>
>

[[email protected]]

I've mentioned tailwheel conversion, right?

On Sun, 23 May 2004 11:39:03 -0700, "Richard Isakson"
> wrote:

> wrote ...
>> I'm really asking about the possibility of a slats'd wing. I guess
>> nobody is working on that. But really nobody else interested in a bush
>> 150?
>
>Slats work by increasing the maximum angle of attack that the wing will
>achieve before the wing stalls. On the ground the Cessna 150 is
>geometrically limited to it's current max AOA. For your project to work it
>would need Storch-like maingear but you'll lose all of your forward
>visibility.
>
>Rich
>

[Dan Thomas]

A C150 isn't much of an airplane. We used to joke that we used ours
for taxi trainers. On hot days at our 3000' airport elevation there
were times that they wouldn't climb past 4000' when at gross. They're
a draggy design; the earlier straightbacked models were lighter,
faster and probably climbed better, too.
If you look at the 150's wing and then at a Super Cub's or some
other STOL airplane's you will see a big difference in camber and
leading edge treatment, both of which have a lot to do with low-speed
performance. I once flew a Super Cub that had vortex generators
installed on the wing, and it would approach at 30 knots. You'd never
get a 150 anywhere near numbers like that, even if you got slats to
work. The whole airplane needs to be purpose-designed, and the 150 was
designed to be a simple, strong, cheap airplane for training pilots,
not for flying into tiny unimproved strips.
I also have a few hours in a 90-hp Alon Aircoupe, the last
iteration of the venerable Ercoupe. It had factory rudder pedals in it
and a slide-back canopy, but the rest of the airplane was pretty much
the old design. It grossed 150 lbs less that the C150. Those 90 horses
outpulled the O-200's 100 hp by a wide margin; the airplane took off
shorter, climbed much better and cruised 20 mph faster than the 150.
It led me to believe that the O-200 is a bit over-rated, or that the
150 is a lousy design, or both. At any rate, we no longer run 150s in
our school.

Dan

[[email protected]]

We probably did the same thing by converting the air density etc. I
could be wrong because I used 5600 ft/mile, and I did not re-check
etc. So I'll say your number is correct.

I was hoping for a 450 useful. The stock empty is 950#. Someone
mentioned that tail wheel conv. will save some weight (but I doubt if
he really knows). And avionics and gyro will also go. So I said 900
empty as a ball park number. At 1350#, that's about 20% less.

Right now it's all hanger flying. No need for wind tunnel data. :)

Jizhong
On Sun, 23 May 2004 18:18:19 GMT, Kevin Horton > wrote:

>On Sun, 23 May 2004 11:51:27 -0700, jizhonghe wrote:
>
>>
>> Kevin,
>>
>> There must be some typo in your formular. I looked up my book (Design for
>> Fly) and is something like:
>>
>> V=16.2*sqrt(WL/Cl)
>
>Whoops, I accidentally left the sea level density out of that conversion
>factor. Once I move the sea level density inside the conversion factor, I
>get:
>
>VS = 17.18*sqrt(WL/CLmax)
>
>Thanks for pointing that out.
>
>Are you sure your book says 16.2 and not 17.2? Otherwise I'm not sure
>where the difference is.
>
>>
>> The book also states that the Cl for a Fowler flap could be 2.8 compared
>> with 1.4 of no flap. So if I take your number of +1.0 for the LES(leading
>> edge slats), I think a Cl of 3.0 seems reasonable with some flap.
>
>A Clmax of 3 is achievable with complex, multi-sloted flaps and slats.
>But you likely won't achieve such a CL unless you have the means to do
>lots of wind tunnel and/or development flight te$ting.
>
>See:
>
>http://adg.stanford.edu/aa241/highlift/highliftintro.html
>
>>
>> Also remember my gross is reduced by almost 20% (not considering the
>> increase due to the additional slats because I don't how much more
>> weight) and the increase of the wing area by about 10%.
>
>A basic C150 doesn't have very much useful load at the stock gross weight.
>What useful load do you require for your mission? Exactly how do you
>plan to reduce the empty weight, while increasing wing area and adding
>slats and complex multi-slotted flaps?
>
>> For stock C150,
>> the wing loading is almost exactly 10 and V stall clean is 47kts. This
>> will give a Cl of only about 1.2. Oh well. Anyway if we use Cl=3 and
>> wing loading of 7 let's see what we get:
>>
>> V=16.2*sqrt(7/3)= 24.7 kts
>>
>> Wow. Geez! I'm sure at 30mph the formula might break (or Cl will change)
>> but anyway, I still think 40mph is not that unreachable.
>
>Let me know when you've got some credible flight test results, showing
>calibrated airspeeds at the stall of 40 mph at a useful gross weight.

[Richard Isakson]

> wrote ...
> I've mentioned tailwheel conversion, right?

If you haven't scraped the tail tiedown ring on a 150 then you're not trying
very hard. Have you flown a 150 before? A tailwheel conversion with the
existing gear moved forward would make the wing max angle of attack lower.

Rich

[Richard Isakson]

"Blueskies" wrote ...
> Unless you set up a variable AOA wing...

But that drives the complexity (and the weight) way up.

Rich

[Blueskies]

Yes...

--
Dan D.
http://www.ameritech.net/users/ddevillers/start.html


..
"Richard Isakson" > wrote in message ...
> "Blueskies" wrote ...
> > Unless you set up a variable AOA wing...
>
> But that drives the complexity (and the weight) way up.
>
> Rich
>
>

[[email protected]]

Rich,

Very good point and I see now.

What is that angle and what's the critical AOA?

On the other hand, once the wheels lift off the plane will not subject
to the limitation that you mentioned, right.

Jizhong

On Sun, 23 May 2004 18:39:31 -0700, "Richard Isakson"
> wrote:

> wrote ...
>> I've mentioned tailwheel conversion, right?
>
>If you haven't scraped the tail tiedown ring on a 150 then you're not trying
>very hard. Have you flown a 150 before? A tailwheel conversion with the
>existing gear moved forward would make the wing max angle of attack lower.
>
>Rich
>

[Richard Isakson]

> wrote ...
> What is that angle and what's the critical AOA?

Ah, that's for the designer (you) to work out. It depends on the overall
design decisions.

> On the other hand, once the wheels lift off the plane will not subject
> to the limitation that you mentioned, right.

That's true but you no longer need the slow speed either.

Rich

[[email protected]]

OK,

That's fair. At least you raised a good point.

Now I need to remind you that to clear 50ft, you more or less double
your ground run. So you do need the slow speed (read Vx).

Jizhong
On Sun, 23 May 2004 19:45:09 -0700, "Richard Isakson"
> wrote:

> wrote ...
>> What is that angle and what's the critical AOA?
>
> Ah, that's for the designer (you) to work out. It depends on the overall
>design decisions.
>
>> On the other hand, once the wheels lift off the plane will not subject
>> to the limitation that you mentioned, right.
>
>That's true but you no longer need the slow speed either.
>
>Rich
>

[Richard Isakson]

> wrote ...
> OK,
>
> That's fair. At least you raised a good point.
>
> Now I need to remind you that to clear 50ft, you more or less double
> your ground run. So you do need the slow speed (read Vx).

You've got those draggy leading edge devices hanging out and now you want to
clear an obstacle? HA! Time for a bigger engine. (and the design grows and
the weights go up and ...)

By the way, have you looked at stability and control yet? You're going much
slower now, do you have any rudder control left? Fact is you need bigger
feathers all the way around. Isn't design fun?

Rich

[[email protected]]

Rich,

I see your point. Thank you very much. This is indeed very very
important. You really taugh me something.

Maybe I should know that too much change is not a good thing if I want
preserve the balance of the original design. Maybe I was just trying
to concentrate on the stall speed alone for now. :)

Still I think the flying quality would be much better at 60mph if the
stall speed (and stall speed alone) is reduced from 54 to 40 mph.

Jizhong
On Sun, 23 May 2004 21:36:00 -0700, "Richard Isakson"
> wrote:

> wrote ...
>> OK,
>>
>> That's fair. At least you raised a good point.
>>
>> Now I need to remind you that to clear 50ft, you more or less double
>> your ground run. So you do need the slow speed (read Vx).
>
>You've got those draggy leading edge devices hanging out and now you want to
>clear an obstacle? HA! Time for a bigger engine. (and the design grows and
>the weights go up and ...)
>
>By the way, have you looked at stability and control yet? You're going much
>slower now, do you have any rudder control left? Fact is you need bigger
>feathers all the way around. Isn't design fun?
>
>Rich
>

[[email protected]]

On Sat, 22 May 2004 18:38:56 -0700, wrote:

>Hello, I have a long term goal of making a small bush plane: 450lbs
>useful load, 35mph clean stall, 600 ft clear 50ft. I know there are
>quite a few designs out there, PA-11 Cub, Bushcaddy, Zenith CH701 to
>name a few that I'm kind of familiar. But here, I'm looking into the
>possiblity of working it out on a c150.
>
>First of all, I want to say that this C150 will have a much lower
>gross when used for bush flying, I know it'll be 1400# with no mods
>but I like to see if I could push it down to 1300#. And now I want to
>tackle on one aspect this time, how to improve the wings to
>significantly reduce the stall speed.

If you just want to play, I think this type of project will keep you
occupied for a long long time.

Alternatively, there are many Cubs modified for the bush with 180 hp
engines that have a better performance than what you are looking for.

There is also the Arctic Tern <http://www.interstateaircraft.com/>

Corky Scott

[Carl Ellis]

If you want to go cheap and experimental, get yourself a cheap basket case
Taylocraft BC-12, do a rebuild converting it to a Model 19, then put in a
C-90 or O-200. Give that engine high compression pistons, do some porting,
polishing and exhaust work and you're good to go. Some vortex generators
will lower your stall speed about 8mph to about 35mph. You'll have an
airplane that has around a 600 lbs load capacity and climbs like scalded
ape.

Put in patrol doors, a skylight, and no headliner and you'll take care of
some of the space issue.

Of course you'll need to deal with the certificated to experimental issue
but if you start early enough with the FSDO and work in enough rebuild
and/or modifications you should qualify for the 51% requirement.

It's not the project you described but it will give you the performance you
want in the same size airplane.

- Carl -

[[email protected]]

Corky and Carl,

Yes, I'm aware of the T-craft and the cub. Like I said, for now, I'm
concentrated on and exploring the c150 only. With the discussion so
far, I already learned something. Although, I still could not find
someone who really knows about slats. The problem with VG is that, it
does not increase the Cl at the same angle. It might increase a little
bit of the critical AOA though.

Jizhong
On Tue, 25 May 2004 09:24:34 -0500, Carl Ellis
> wrote:

>If you want to go cheap and experimental, get yourself a cheap basket case
>Taylocraft BC-12, do a rebuild converting it to a Model 19, then put in a
>C-90 or O-200. Give that engine high compression pistons, do some porting,
>polishing and exhaust work and you're good to go. Some vortex generators
>will lower your stall speed about 8mph to about 35mph. You'll have an
>airplane that has around a 600 lbs load capacity and climbs like scalded
>ape.
>
>Put in patrol doors, a skylight, and no headliner and you'll take care of
>some of the space issue.
>
>Of course you'll need to deal with the certificated to experimental issue
>but if you start early enough with the FSDO and work in enough rebuild
>and/or modifications you should qualify for the 51% requirement.
>
>It's not the project you described but it will give you the performance you
>want in the same size airplane.
>
>- Carl -

[Richard Lamb]

"Two months in the lab will save you three days in the library -
every time".

Check back issues of Sport Aviation.
They published an article about just such a project.

I don't remember all the details off hand, but seems like it was
done by a preacher fellow up north (north of Dallas?)

Extensive use of turbulators on the wing and tail and a fancy
"flow thru" wing tip. Maybe did some changes to the flaps and
ailerons too?

Asking about something on the internet is NOT research...

But sometimes it can help.


Richard Lamb

[[email protected]]

Richard,

You're right that you can not do research by searching the web.

Could you be a little bit more specific about the Sport Aviation
article? Year and page?

Jizhong
On Wed, 26 May 2004 15:26:49 GMT, Richard Lamb >
wrote:

>"Two months in the lab will save you three days in the library -
>every time".
>
>Check back issues of Sport Aviation.
>They published an article about just such a project.
>
>I don't remember all the details off hand, but seems like it was
>done by a preacher fellow up north (north of Dallas?)
>
>Extensive use of turbulators on the wing and tail and a fancy
>"flow thru" wing tip. Maybe did some changes to the flaps and
>ailerons too?
>
>Asking about something on the internet is NOT research...
>
>But sometimes it can help.
>
>
>Richard Lamb

[Richard Lamb]

wrote:
>
> Richard,
>
> You're right that you can not do research by searching the web.
>
> Could you be a little bit more specific about the Sport Aviation
> article? Year and page?
>
> Jizhong
> On Wed, 26 May 2004 15:26:49 GMT, Richard Lamb >
> wrote:
>
> >"Two months in the lab will save you three days in the library -
> >every time".
> >
>

Sorry, I've been packing stuff up getting ready to move.
Somebody here have the latest Sport Aviation index handy?

Richard