Horsepower required for level flight question...

[BllFs6]

Hi all...

Was reading about a glider the other day....

It has something like a sink rate of 125 feet per minute at a 400 pound total
wieght when its going about 35 mph...

Now given that 1foot pound/sec = .00182 HP and the glider is being powered by
gravity....

125 * 400 / 60 = 833

833 * 0.00182 = 1.5

So, are those calcs right and it would only take 1.5 horsepower to keep that
glider going in level flight at 35 mph?

If thats the case..it makes me wanna get a glider, a weed wacker with a prop on
it and do some CHEAP, long, slow flights :)

take care

Blll

[Bill Daniels]

Good observation.

Take my Nimbus 2C glider for example. The flying weight, less water
ballast, is about 1000 pounds. The Lift over Drag is 47:1 at 51 knots. (At
1440 pounds with water ballast, the L/D rises to 49:1 at 59 knots)

Divide 1000 by 47 and get 21.3 pounds of thrust needed for 51 Knot level
flight. Your weedwhacker engine would easily do that.

Gliders with small "sustainer" engines are widely available from Europe.
They call them "turbo" gliders as opposed to the "self launcher" gliders
with bigger engines. The engine can be retracted into the fuselage behind
the wing. If needed, the engine can be extended and air started with just
airflow through the tiny prop.

However, with 49:1 glide ratio, if well flown, you won't NEED the little
engine.

Bill Daniels


"BllFs6" > wrote in message
...
> Hi all...
>
> Was reading about a glider the other day....
>
> It has something like a sink rate of 125 feet per minute at a 400 pound
total
> wieght when its going about 35 mph...
>
> Now given that 1foot pound/sec = .00182 HP and the glider is being powered
by
> gravity....
>
> 125 * 400 / 60 = 833
>
> 833 * 0.00182 = 1.5
>
> So, are those calcs right and it would only take 1.5 horsepower to keep
that
> glider going in level flight at 35 mph?
>
> If thats the case..it makes me wanna get a glider, a weed wacker with a
prop on
> it and do some CHEAP, long, slow flights :)
>
> take care
>
> Blll

[Veeduber]

>
>So, are those calcs right and it would only take 1.5 horsepower to keep that
>glider going in level flight at 35 mph?
>

-------------------------------------------------------

Sounds about right but... (you KNEW there was a but, right?) :-)

You want thrust, not horsepower. Reality tends to differ from the
conversion-factor solutions due to velocity and prop losses. (Remember the NSU
'Prinz'? Ever see the little ducted-fan power pod that used the tiny Wankle?
Something like 6hp and TINY. With even a whiff of green air it could keep you
up all day after a winch launch.)

And of course the weght is no longer 400 but something more (ie, engine,
controls, fuel, mounting, etc).

But you're on the right track: Lift vs Weight, Thrust vs Drag (Notice that
horsepower is not mentioned :-) Once airborne, it doesn't take much to keep a
high-lift, light weight, aerodynamically efficient airframe flying. The tricky
bit is getting airborne to begin with :-)

(Then comes those horrible inverse equations dealing with drag (square it) and
power (cube it) any time you want to get there in a hurry.)

----------------------------------------

You did good, Bill. Your logic mirrors that of the Wright brothers which puts
you head & shoulders above 99% of the crowd.

-R.S.Hoover

[BllFs6]

>You did good, Bill. Your logic mirrors that of the Wright brothers which
>puts
>you head & shoulders above 99% of the crowd.
>
>-R.S.Hoover

Well...

I think you just insulted the Wright brothers :)

take care

Blll

[BllFs6]

Hi Guys

Thanks for the replies Bill and Vee Duber!

Given that gliders are sooo darn efficient fuel wise and that it would take a
pretty minimal engine for one to self launch (20hp is my WAG for a single
seater).....why do we not see more airplanes that a cross between a glider and
a conventional plane?

Glider pilots hate engines? Powered pilots want barrel rolls and roaring
engines? Never the twain shall meet?

Seems to me if cost and the amount of time airborne are your primary desire
drivers then a "overpowered" glider would be the ticket...

Am I right in the main disadvantage of a powered glider is long take off rolls
and lack of fancy aerobatics? Other considerations I am missing?

And another question just popped into my head...anyone ever seen a canard
glider?

take care

Blll

[Boelkowj]

Long wing spans are harder to land in a cross wind.

Larry

[Bill Daniels]

"Boelkowj" > wrote in message
...
> Long wing spans are harder to land in a cross wind.
>
> Larry

Oh, I dunno, I have landed a glider in 20+ knots x-wind. My old Archer only
had a 17 knot demonstrated x-wind. Then again, with a 35 knot touchdown
speed less 20 knot headwind, just ignore the runway and land into the
wind. - only takes about 50 feet.

Bill Daniels

[Bill Daniels]

"BllFs6" > wrote in message
...
> Hi Guys
>
> Thanks for the replies Bill and Vee Duber!
>
> Given that gliders are sooo darn efficient fuel wise and that it would
take a
> pretty minimal engine for one to self launch (20hp is my WAG for a single
> seater).....

More like 50 - 60 HP to get a decent ROC.

> why do we not see more airplanes that a cross between a glider and
> a conventional plane?

We do, they are called "Touring Motorgliders" and are widely available.
See Grob 109 or the Super Ximango. They use Rotax 912's.

>
> Glider pilots hate engines? Powered pilots want barrel rolls and roaring
> engines? Never the twain shall meet?

Aerobatic gliders are very common. Engines make aerobatics less capable
because of the weight and reduced load factors. Silent aerobatics in a
glider are a wonder to behold.

OTOH, Bob Carlson of Albuquerque has an ultralight sailplane with two model
airplane turbojets on it - goes like a scalded cat. We call it the "Dog
Whistle" behind his back. Bob has an airshow act doing aerobatics in it.

Self launch gliders are getting more popular all the time. In Europe, over
half the new gliders sold have self launch capability.

>
> Seems to me if cost and the amount of time airborne are your primary
desire
> drivers then a "overpowered" glider would be the ticket...

If you want air time and low cost, go for a pure sailplane. Most of my
buddies are out on 300 mile, 6 hour flights every weekend. 6 hours from a
$20 tow is less than $4 an hour. Pure gliders stay in the air so long they
have to be plumbed for relief tubes.

BTW, I always thought of an X-15 or the Space Shuttle as an overpowered
glider.....
>
> Am I right in the main disadvantage of a powered glider is long take off
rolls
> and lack of fancy aerobatics? Other considerations I am missing?

The disadvantage is cost, maintenance and complexity. The number of bells
and whistles in a motorglider darn near equals a twin.

>
> And another question just popped into my head...anyone ever seen a canard
> glider?

Yup, Burt Rutan's "Solitare". Probably his worst design which is why you
haven't heard of it. Canards are very inefficient at low speeds and high
AOA - they make lousy gliders.


Bill Daniels

[Darrel Toepfer]

BllFs6 wrote:

> Am I right in the main disadvantage of a powered glider is long take off rolls
> and lack of fancy aerobatics? Other considerations I am missing?

4 to 6 seat capacity comes to my mind (needs/wants)...

[Tim Ward]

"Bill Daniels" > wrote in message
...
>
> "Boelkowj" > wrote in message
> ...
> > Long wing spans are harder to land in a cross wind.
> >
> > Larry
>
> Oh, I dunno, I have landed a glider in 20+ knots x-wind. My old Archer
only
> had a 17 knot demonstrated x-wind. Then again, with a 35 knot touchdown
> speed less 20 knot headwind, just ignore the runway and land into the
> wind. - only takes about 50 feet.
>
> Bill Daniels

"That's sure a short runway".
"Yeah, but look at how _wide_ that sucker is!"

Tim Ward

[Kevin Horton]

On Sat, 27 Mar 2004 17:26:00 -0500, Bryan Martin wrote:

> in article , Darrel Toepfer
> at wrote on 3/27/04 1:49 PM:
>
>> BllFs6 wrote:
>>
>>> Am I right in the main disadvantage of a powered glider is long take
>>> off rolls
>>> and lack of fancy aerobatics? Other considerations I am missing?
>>
>> 4 to 6 seat capacity comes to my mind (needs/wants)...
>
> How about 13?
>
> http://www.wpafb.af.mil/museum/air_power/ap26.htm

Sure doesn't look like a powered glider to me.

If you are looking for a large capacity powered glider, the ME-323 is the
closest I can think of - accommodation for 120 passengers. But it would
never have shut down the engines and glided, so it doesn't really fit the
current understanding of those terms.

<http://www.warbirdsresourcegroup.org/LRG/me323.html>
<http://www.flight-history.com/plane_stats/acModelView.php?makeId=40&makeName=Messerschmitt&modelId=402>

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

[Darrel Toepfer]

Bryan Martin wrote:
> Darrel Toepfer wrote:
>>BllFs6 wrote:
>>
>>>Am I right in the main disadvantage of a powered glider is long take off
>>>rolls
>>>and lack of fancy aerobatics? Other considerations I am missing?
>>
>>4 to 6 seat capacity comes to my mind (needs/wants)...

> How about 13?
>
> http://www.wpafb.af.mil/museum/air_power/ap26.htm

Looks to be, where it belongs... Where's the motor? <g> We are
discussing motorgliders after all...

The germans put several (6 I believe) engines on their former glider, it
could carry a tank into battle. Had a row of like 9 retractable boogie
(sp?) wheels underneath it...

[Bill Daniels]

> >> 4 to 6 seat capacity comes to my mind (needs/wants)...

Nuts to that. Tell them to get their own motorglider.

Bill Daniels

[Blueskies]

>
> "That's sure a short runway".
> "Yeah, but look at how _wide_ that sucker is!"
>
> Tim Ward
>
>


Exactly!

[Darrel Toepfer]

Kevin Horton wrote:

> Sure doesn't look like a powered glider to me.
>
> If you are looking for a large capacity powered glider, the ME-323 is the
> closest I can think of - accommodation for 120 passengers. But it would
> never have shut down the engines and glided, so it doesn't really fit the
> current understanding of those terms.
>
> <http://www.warbirdsresourcegroup.org/LRG/me323.html>
> <http://www.flight-history.com/plane_stats/acModelView.php?makeId=40&makeName=Messerschmitt&modelId=402>

Thats the one I was thinking of, couldn't remember its name though.
Thanks... Before they put the engines on it, they used 3 twin engined
planes to tow that whale into the sky...

Even had rocket assisted takeoff modes:
http://www.warbirdsresourcegroup.org/LRG/me321.html

The tow plane:
http://www.warbirdsresourcegroup.org/LRG/me321.html

[Wright1902Glider]

Actually, there are several powerplant/prop harness-units commercially
available for use with hang-gliders. While their use is still contraversial
(is it an ultralight or HG?) the USHGA has ruled to include them in our bylaws.
The condition is that the powerplant is intended for climbout only, with the
primary power coming from soaring thermals.

I've also seen several self-lanuching "motorgliders", two of wich were
performing aerobatics at airshows.

As for a canard glider, I suggest you check out the photos of my Wright 1902
glider on my website. Best glide for the original was 622 1/2 ft. launching
from a 100 ft. hill... World record in 1902. Still extremely unstable, but
that's half the fun!

Harry
http://hometown.aol.com/wright1902glider/airshow.html

[Richard Lamb]

Wright1902Glider wrote:
>
> Actually, there are several powerplant/prop harness-units commercially
> available for use with hang-gliders. While their use is still contraversial
> (is it an ultralight or HG?) the USHGA has ruled to include them in our bylaws.
> The condition is that the powerplant is intended for climbout only, with the
> primary power coming from soaring thermals.
>

All right, Harry.
Now ya done gone and done it.

Who has my old Icarus biplane plans?
Cough 'em up!

Richard

[Cy Galley]

The French Cri-Cri flew very well with 2 - 6 horsepower chainsaw engines.
"Wright1902Glider" > wrote in message
...
> Actually, there are several powerplant/prop harness-units commercially
> available for use with hang-gliders. While their use is still
contraversial
> (is it an ultralight or HG?) the USHGA has ruled to include them in our
bylaws.
> The condition is that the powerplant is intended for climbout only, with
the
> primary power coming from soaring thermals.
>
> I've also seen several self-lanuching "motorgliders", two of wich were
> performing aerobatics at airshows.
>
> As for a canard glider, I suggest you check out the photos of my Wright
1902
> glider on my website. Best glide for the original was 622 1/2 ft.
launching
> from a 100 ft. hill... World record in 1902. Still extremely unstable,
but
> that's half the fun!
>
> Harry
> http://hometown.aol.com/wright1902glider/airshow.html