For the real engineers here

I'm thinking of a clean glider, one that might weigh 1500 pounds and
has a glide angle of say 1 in 25. At 50 miles an hour, that would mean
in an hour's time it might descend two miles (of course scale it
reasonable numbers, I chose those for ease of calculation). That means
it's losing about 1500 * 5280 * 2, or about 16 million foot pounds of
energy an hour.

Now if I add an engine swinging an 8 foot diameter prop, maybe as a
pusher, the question is, how big an engine for cruise only? A
horsepower is 550 foot lbs a second, or about 2 million foot pounds
an hour. If all of that is correct, it suggests with a 50% efficient
prop a little 16 horsepower engine could pretty much keep this thing
at constant altitude.

It passes the reasonableness test as far as I can see. Any serious
disagreements?

For those of you who do things in metric units? I went to school a
long long time ago, and here in the US I can buy a little Briggs and
Stanton (spelling?) engine with a horsepower rating, not a kilowatt
one.

wrote in news:f21210b7-96ff-44c6-9b4b-120e489e7682@
59g2000hsb.googlegroups.com:

I'm thinking of a clean glider, one that might weigh 1500 pounds and
has a glide angle of say 1 in 25. At 50 miles an hour, that would mean
in an hour's time it might descend two miles (of course scale it
reasonable numbers, I chose those for ease of calculation). That means
it's losing about 1500 * 5280 * 2, or about 16 million foot pounds of
energy an hour.

Now if I add an engine swinging an 8 foot diameter prop, maybe as a
pusher, the question is, how big an engine for cruise only? A
horsepower is 550 foot lbs a second, or about 2 million foot pounds
an hour. If all of that is correct, it suggests with a 50% efficient
prop a little 16 horsepower engine could pretty much keep this thing
at constant altitude.

It passes the reasonableness test as far as I can see. Any serious
disagreements?

For those of you who do things in metric units? I went to school a
long long time ago, and here in the US I can buy a little Briggs and
Stanton (spelling?) engine with a horsepower rating, not a kilowatt
one.


Here ya go...

http://www.usenet.com/newsgroups/rec.../msg06267.html

On Jun 25, 2:10 pm, Bertie the Bunyip wrote:
wrote in news:f21210b7-96ff-44c6-9b4b-120e489e7682@
59g2000hsb.googlegroups.com:



I'm thinking of a clean glider, one that might weigh 1500 pounds and
has a glide angle of say 1 in 25. At 50 miles an hour, that would mean
in an hour's time it might descend two miles (of course scale it
reasonable numbers, I chose those for ease of calculation). That means
it's losing about 1500 * 5280 * 2, or about 16 million foot pounds of
energy an hour.

Now if I add an engine swinging an 8 foot diameter prop, maybe as a
pusher, the question is, how big an engine for cruise only? A
horsepower is 550 foot lbs a second, or about 2 million foot pounds
an hour. If all of that is correct, it suggests with a 50% efficient
prop a little 16 horsepower engine could pretty much keep this thing
at constant altitude.

It passes the reasonableness test as far as I can see. Any serious
disagreements?

For those of you who do things in metric units? I went to school a
long long time ago, and here in the US I can buy a little Briggs and
Stanton (spelling?) engine with a horsepower rating, not a kilowatt
one.

Here ya go...

http://www.usenet.com/newsgroups/rec.../msg06267.html

Yeah, that gives some comfort that the decimal point at least is in
the right place. Thanks

wrote in news:b6c58e3d-f0ee-4d52-842a-
:

On Jun 25, 2:10 pm, Bertie the Bunyip wrote:
wrote in news:f21210b7-96ff-44c6-9b4b-120e489e7682@
59g2000hsb.googlegroups.com:



I'm thinking of a clean glider, one that might weigh 1500 pounds
and
has a glide angle of say 1 in 25. At 50 miles an hour, that would
mean
in an hour's time it might descend two miles (of course scale it
reasonable numbers, I chose those for ease of calculation). That
means
it's losing about 1500 * 5280 * 2, or about 16 million foot pounds
of
energy an hour.

Now if I add an engine swinging an 8 foot diameter prop, maybe as a
pusher, the question is, how big an engine for cruise only? A
horsepower is 550 foot lbs a second, or about 2 million foot
pounds
an hour. If all of that is correct, it suggests with a 50%
efficient
prop a little 16 horsepower engine could pretty much keep this
thing
at constant altitude.

It passes the reasonableness test as far as I can see. Any serious
disagreements?

For those of you who do things in metric units? I went to school a
long long time ago, and here in the US I can buy a little Briggs
and
Stanton (spelling?) engine with a horsepower rating, not a kilowatt
one.

Here ya go...

http://www.usenet.com/newsgroups/rec.../msg06267.html

Yeah, that gives some comfort that the decimal point at least is in
the right place. Thanks

BTW, your glider will need to be a good bit lighter to have anythign
more than marginal perfoemance. With that much HP you should be grossing
about 700 lbs max.



Bertie

wrote in message
...

Yeah, that gives some comfort that the decimal point at least is in
the right place. Thanks

You are feeding a troll.

On Jun 25, 3:44 pm, "Maxwell" luv2^fly99@cox.^net wrote:
wrote in message

...



Yeah, that gives some comfort that the decimal point at least is in
the right place. Thanks

You are feeding a troll.

I asked for information and got it. A "thank you" was a suitable
response, and I do not consider it feeding a troll, but a polite reply
to a civil answer. Maybe one person's troll is something else
elsewhere.

In article , Maxwell says...


wrote in message
...

Yeah, that gives some comfort that the decimal point at least is in
the right place. Thanks

You are feeding a troll.

Maxine, *you* are the troll.

As everyone here realizes.

--

"Tis an ill wind that blows no minds"

You are a common liar.

Maxwell, ye tickle-brained dunce, snakes, in my heart blood warmed, that
sting my heart. Thou Judas, thrice worse than Judas, ye gurgled:

If I learn from my mistakes, I'll learn a lot today.

"Maxwell" luv2^fly99@cox.^net wrote in news:Qex8k.4702$i55.1320
@newsfe22.lga:


wrote in message
...

Yeah, that gives some comfort that the decimal point at least is in
the right place. Thanks

You are feeding a troll.



You are choking on your own stupidity.



Excellent.


Bertie