Those Whacky RC DS guys

Holy Cow! I hadn't checked YouTube for a while. I'm amazed at the
speeds they're getting.
http://www.youtube.com/watch?v=WaQB16ZaNI4

On 17 Apr, 01:32, Uncle Fuzzy wrote:
Holy Cow! *I hadn't checked YouTube for a while. *I'm amazed at the
speeds they're getting.http://www.youtube.com/watch?v=WaQB16ZaNI4

Thanks - astonishing. 391mph model glider that only weight
a few pounds.

I had a couple of thoughts.

1. I don't believe it - since got over that one, I do believe it now.

2. I wonder how many g they are pulling.

Does 35g seem reasonable?

From video:-

24 secs for 8 laps at say 370mph - max was 375 on that run.

close to 3 secs per lap

370mph = 165m/s

http://www.ajdesigner.com/phpcircula...n_equation.php

T is period

a = v^2 / r

r = vT / 2pi
= 165 * 3 / 2pi
= 78m

a = 165 * 165 / 78
= 349 m/s/s or 35g

This seems like quite a lot but is plausible.

I was expecting a big number since I recall
seeing a jet fighter do a reported 5g turn at
400mph ish and it took a LOT longer than
3 secs per orbit

On Apr 19, 4:50*pm, bod43 wrote:
On 17 Apr, 01:32, Uncle Fuzzy wrote:

Holy Cow! *I hadn't checked YouTube for a while. *I'm amazed at the
speeds they're getting.http://www.youtube.com/watch?v=WaQB16ZaNI4

Thanks - astonishing. 391mph model glider that only weight
a few pounds.

I had a couple of thoughts.

1. I don't believe it - since got over that one, I do believe it now.

2. I wonder how many g they are pulling.

Does 35g seem reasonable?

From video:-

24 secs for 8 laps at say 370mph - max was 375 on that run.

close to 3 secs per lap

370mph = 165m/s

http://www.ajdesigner.com/phpcircula..._acceleration_...

T is period

a = v^2 / r

r = vT / 2pi
* = 165 * 3 / 2pi
* = 78m

a = 165 * 165 / 78
* = 349 m/s/s or 35g

This seems like quite a lot but is plausible.

I was expecting a big number since I recall
seeing a jet fighter do a reported 5g turn at
400mph ish and it took a LOT longer than
3 secs per orbit

I know that modern all CF molded F3B planes snap in short order.
There was a group of guys in Oregon that were on the leading edge of
RC DS'ing. They tried the above mentioned F3B model first, then
designed their own, testing it to 50G's. It folded. I would love to
know just how many G's they're pulling now.

On Apr 19, 8:22*pm, Uncle Fuzzy wrote:
On Apr 19, 4:50*pm, bod43 wrote:



On 17 Apr, 01:32, Uncle Fuzzy wrote:

Holy Cow! *I hadn't checked YouTube for a while. *I'm amazed at the
speeds they're getting.http://www.youtube.com/watch?v=WaQB16ZaNI4

Thanks - astonishing. 391mph model glider that only weight
a few pounds.

I had a couple of thoughts.

1. I don't believe it - since got over that one, I do believe it now.

2. I wonder how many g they are pulling.

Does 35g seem reasonable?

From video:-

24 secs for 8 laps at say 370mph - max was 375 on that run.

close to 3 secs per lap

370mph = 165m/s

http://www.ajdesigner.com/phpcircula..._acceleration_...

T is period

a = v^2 / r

r = vT / 2pi
* = 165 * 3 / 2pi
* = 78m

a = 165 * 165 / 78
* = 349 m/s/s or 35g

This seems like quite a lot but is plausible.

I was expecting a big number since I recall
seeing a jet fighter do a reported 5g turn at
400mph ish and it took a LOT longer than
3 secs per orbit

I know that modern all CF molded F3B planes snap in short order.
There was a group of guys in Oregon that were on the leading edge of
RC DS'ing. *They tried the above mentioned F3B model first, then
designed their own, testing it to 50G's. *It folded. *I would love to
know just how many G's they're pulling now.

Thermal F3B planes snap at 100 mph or so. You do that in the dive-in.

Slope F3F models snap at 200 mph, or a couple of laps.

One production plane has gone over 370 mph. It cost $3 to $4 grand for
the airframe only. Anything faster is custom-made in home workshops
often sing Skunk Works-sourced airfoil profiles and CAD designed CNC
cut wing molds. These guys take this very seriously.

The problem is not continuous g as it makes a lap, it is peak g as the
plane passes the shear layers, a rather violent event. 35 g is a low
estimate.

Consider the D-160" model, which will likely break 400 mph next Santa
Ana season. It weighs 50 pounds and the spar is designed to withstand
over 4000 lbf. So it can over 100g when you consider the wing make
over half the weight of the plane.

In any case, strength is relatively easy to resolve and proper DS
ships rarely clap their wings. A far bigger challenge is in
controlling flutter. One recent design is using mass balancing on the
ailerons and multiple giant scale servos on the ailerons.

Joe Wurts calculated the maximum DS speed to be around 450 mph. The
progress to date has been astounding considering that 200 mph was a
record only 5 years ago.

I can attest that this form of flying it is VERY addicting!

/Adam

Adam wrote:


Consider the D-160" model, which will likely break 400 mph next Santa
Ana season. It weighs 50 pounds and the spar is designed to withstand
over 4000 lbf. So it can over 100g when you consider the wing make
over half the weight of the plane.

50 pounds moving at 400 mph could cause multiple fatalities if it plowed
into some bystanders. How do they make these models safe to fly? Do they
have insurance? How big/heavy can a "model" be before it becomes a UAV,
and perhaps regulated by the FAA?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Apr 20, 12:47*pm, Eric Greenwell wrote:
Adam wrote:

Consider the D-160" model, which will likely break 400 mph next Santa
Ana season. It weighs 50 pounds and the spar is designed to withstand
over 4000 lbf. So it can over 100g when you consider the wing make
over half the weight of the plane.

50 pounds moving at 400 mph could cause multiple fatalities if it plowed
into some bystanders. How do they make these models safe to fly? Do they
have insurance? How big/heavy can a "model" be before it becomes a UAV,
and perhaps regulated by the FAA?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes"http://tinyurl.com/y739x4
* * * Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

Good point, but even a 1 pound plane could kill you at that speed.
Back in the stone age, when I was slope racing RC gliders, I think the
AMA imposed weight limit was 10 pounds.