Electrically Powered Ultralight Aircraft

wrote)
Normally what happens when thread drift begins is that it increases at an
increasing rate such that what was originally zepplin aerodynamics becomes
the best recipe for strawberry preserves...


So you're saying zeppelins should take advantage of jam-jet propulsion
technology?

....when in season, of course


Paul-Mont
Usually needs to snow twice before I get the drift ~~~~

On Aug 11, 9:47 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
...
I've already made a cell holder for A123 Systems "A1" cells. That's the
lithium phosphate nano cathode one used in 36V DeWalt power tools. You can
buy a couple of new DeWalt 36V power packs for $50 or so on Ebay. Then,
dismantle the pack to retrieve the individual cells. My pack will be 13.8
volts and 11AH weighing 3 pounds. It will be the same size as a 7AH 12V SLA
but weigh less than half as much.

Don't forget to add a brick of lead to the bottom of your
new battery pack, to keep the CG in the right place ;-)
Best Regards, Dave "YO"

wrote)
In cars, weight matters most in acceleration and doesn't matter in any
significant amount with modern tires in cruise.


Speculate please:

1. Two 3,600 lb cars - good tires
2. Traveling 60 mph (no wind)
3. 4cly - 150 hp (Honda Accords)
3. Flat highway in North Dakota
4. Fuel flow meters hooked up to both vehicles

(Honda #1)
Driver ................ 105 lbs
Fuel .................... 15 lbs
TOTAL .............. 120 lbs (1/30th of 3,600 lb car)

(Honda #2)
Driver ................. 300 lbs
Passengers ........ 700 lbs
Luggage ............. 100 lbs
Fuel ................... 100 lbs
TOTAL ............. 1,200 lbs (1/3 of 3,600 lb car) ....BTW, BTDT! g

If both vehicles were monitored for 50 miles, would their fuel flow be
(approx) the same, in cruise?


Paul-Mont

("Charles Vincent" wrote)
According to SAE studies, aerodynamic drag accounts for 60% of the
resistance that must be overcome for highway cruise, with tires being 25%
and driveline friction making up the last 15%.


Semi:
Tires ........... 18
Footprint ..... big per tire
Weight ....... 80,000 lbs
Drag .......... HUGE!!
MPG .......... 5 (loaded)

Minivan:
Tires ........... 4
Footprint ..... smaller per tire
Weight ....... 4,000 lbs (for easy math)
Drag .......... MUCH less + no cab/trailer drag
MPG .......... 22

I've never really understood why an 800 lb motorcycle/rider gets (only) 50
mpg and a fully loaded semi can get (about) 5 mpg?

Motorcycle:
Tires ........... 2
Footprint ..... very small per tire
Weight ....... 800 lbs (with rider)
Drag .......... It's a motorcycle! g
MPG ........... 50


Paul-Mont

Montblack wrote:
("Charles Vincent" wrote)
According to SAE studies, aerodynamic drag accounts for 60% of the
resistance that must be overcome for highway cruise, with tires being 25%
and driveline friction making up the last 15%.


Semi:
Tires ........... 18
Footprint ..... big per tire
Weight ....... 80,000 lbs
Drag .......... HUGE!!
MPG .......... 5 (loaded)

Minivan:
Tires ........... 4
Footprint ..... smaller per tire
Weight ....... 4,000 lbs (for easy math)
Drag .......... MUCH less + no cab/trailer drag
MPG .......... 22

I've never really understood why an 800 lb motorcycle/rider gets (only) 50
mpg and a fully loaded semi can get (about) 5 mpg?

Motorcycle:
Tires ........... 2
Footprint ..... very small per tire
Weight ....... 800 lbs (with rider)
Drag .......... It's a motorcycle! g
MPG ........... 50

Motorcycles have a terrible coefficient of drag given their shape and
the shape of the rider. A fully faired bike is much better, but still
much worse than most cars. My K1200LT is one of the better motorcycles
and its Cd is above 0.5 with the windshield fully lowered and I believe
it is closer to 0.6 with the windshield at the highest setting.

So even with the relatively small frontal area as compared to a car
(although not as much smaller as you might think as the bike is taller
than most cars), the drag coefficient is so high that the total drag is
quite high in comparison.

Matt

Montblack wrote:

I've never really understood why an 800 lb motorcycle/rider gets (only) 50
mpg and a fully loaded semi can get (about) 5 mpg?

Motorcycle:
Tires ........... 2
Footprint ..... very small per tire
Weight ....... 800 lbs (with rider)
Drag .......... It's a motorcycle! g
MPG ........... 50


Paul-Mont

Check this: http://www.bgsoflex.com/airdragchart.html

Matt

"Montblack" wrote

So you're saying zeppelins should take advantage of jam-jet propulsion
technology?

Oh, isn't that a sweet idea?
--
Jim in NC

In rec.aviation.piloting Montblack wrote:
wrote)
In cars, weight matters most in acceleration and doesn't matter in any
significant amount with modern tires in cruise.


Speculate please:

1. Two 3,600 lb cars - good tires
2. Traveling 60 mph (no wind)
3. 4cly - 150 hp (Honda Accords)
3. Flat highway in North Dakota
4. Fuel flow meters hooked up to both vehicles

(Honda #1)
Driver ................ 105 lbs
Fuel .................... 15 lbs
TOTAL .............. 120 lbs (1/30th of 3,600 lb car)

(Honda #2)
Driver ................. 300 lbs
Passengers ........ 700 lbs
Luggage ............. 100 lbs
Fuel ................... 100 lbs
TOTAL ............. 1,200 lbs (1/3 of 3,600 lb car) ....BTW, BTDT! g

If both vehicles were monitored for 50 miles, would their fuel flow be
(approx) the same, in cruise?

A pulled out of my ass, wild assed guess is that since you are
increasing the load by 33%, then yes, you will see a difference,
and at that loading the tires will be visibly deformed.

Now, would you care to calculate the energy required to accelerate
3720 pounds to 60 mph versus accelerating 4800 pounds to 60 mph?

Assume gasoline is 45 megajoules per kilogram and the engine is 38%
efficient.

You may neglect all drag for this calculation and express the energy
in kilograms of gasoline.



--
Jim Pennino

Remove .spam.sux to reply.

In rec.aviation.piloting Montblack wrote:
("Charles Vincent" wrote)
According to SAE studies, aerodynamic drag accounts for 60% of the
resistance that must be overcome for highway cruise, with tires being 25%
and driveline friction making up the last 15%.


Semi:
Tires ........... 18
Footprint ..... big per tire
Weight ....... 80,000 lbs
Drag .......... HUGE!!
MPG .......... 5 (loaded)

Minivan:
Tires ........... 4
Footprint ..... smaller per tire
Weight ....... 4,000 lbs (for easy math)
Drag .......... MUCH less + no cab/trailer drag
MPG .......... 22

I've never really understood why an 800 lb motorcycle/rider gets (only) 50
mpg and a fully loaded semi can get (about) 5 mpg?

Motorcycle:
Tires ........... 2
Footprint ..... very small per tire
Weight ....... 800 lbs (with rider)
Drag .......... It's a motorcycle! g
MPG ........... 50


The coefficient of drag for motorcycles is usually pretty bad unless
they are faired, and it still ain't great.

The power required to overcome drag is 1/2(p*v^3*A*C)

p is the densitity of the fluid
v is the airspeed
A is the area
C is the coefficient of drag


--
Jim Pennino

Remove .spam.sux to reply.

wrote:

The coefficient of drag for motorcycles is usually pretty bad unless
they are faired, and it still ain't great.

Yes.


The power required to overcome drag is 1/2(p*v^3*A*C)

No. It is v^2 unless they have changed the physics since I was an aero
engineering student back in the 70s.

Matt