0
travisjones

Wingsuit and Electric Jetpack

Recommended Posts

photognat

Let me put it in simpler terms that even a professor can understand: At trim speed in a wingsuit your actual thrust will be 30-50% of what the EDF is rated at.



Being rude doesn't help your case.

Rated thrust wasn't the issue in question. The issue was how much thrust do you need to maintain level flight. And it most certainly is not 200lbs unless the jumper is severely obese.

And the links that you so generously provided don't seem to say what you think they do. Did you actually read any of them?
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
The thrust isn't lifting you off the ground, it's pushing you forward.

Drag increases with the square of speed right kalland? So to reach a forward speed, high enough to create aerodynamic lift wouldn't you have to overcome more than just the body weight of the jumper?

Sure, with 200lbs thrust vectored directly down, you could lift a 200lb object off the ground, but can it push a heavy inefficient high drag human anvil forward fast enough?

Share this post


Link to post
Share on other sites
nickfrey

The thrust isn't lifting you off the ground, it's pushing you forward.

Drag increases with the square of speed right kalland? So to reach a forward speed, high enough to create aerodynamic lift wouldn't you have to overcome more than just the body weight of the jumper?



No, that is not correct.

Wing lift also increases as the square of the speed. The Cl/Cd ratio is what matters. A plane like a Cessna 172 has a best Cl/Cd (it depends on angle of attack) of around 8, which means that for every 8 pounds of lift only 1 pound of thrust is required to move the plane forward in level flight. So if the plane weighs 2000 pounds, a thrust of just 250 pounds will sustain level flight. Any more and you can climb or go faster.

And think about a Harrier jet. It requires far more thrust to hover than to sustain straight and level forward flight.

It's all covered in basic aerodynamics text books.
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
And telling people that they can't do math isn't rude? I don't have a case, I'm not really trying to argue this. You're not going to find any mathematical models that will accurately tell you exactly how much thrust you're gonna need without a whole lot of horizontal wind tunnel testing.

Assuming a large suit with a very good pilot and a Flysight to finely tune your AOA and body position, 80lbs of actual thrust exiting the wingsuit while you're flying at 120MPH should suffice. In the real world that still puts you at around 200lbs of rated thrust on the ground. Or at least before you modify the exhaust for lower thrust but higher exit velocity.

And yes, rated thrust was exactly what we were talking about. Read a few comments up where we were discussing EDFs capable of 50-60lbs of static thrust, using multiple units for a total of 200lbs, which you then quoted me on.

If you still think I'm wrong, here's a design for an EDF powered plane at a very similar airspeed (97kts). Page 25 has the good parts. http://nari.arc.nasa.gov/sites/default/files/Kerho_TeDP.PhaseI.Final_.Report.ContractNNX13AB92A.pdf

Share this post


Link to post
Share on other sites
photognat

And telling people that they can't do math isn't rude?



I didn't say you couldn't do the math. I said you didn't do the math.

Quote



I don't have a case, I'm not really trying to argue this. You're not going to find any mathematical models that will accurately tell you exactly how much thrust you're gonna need without a whole lot of horizontal wind tunnel testing.

Assuming a large suit with a very good pilot and a Flysight to finely tune your AOA and body position, 80lbs of actual thrust exiting the wingsuit while you're flying at 120MPH should suffice. In the real world that still puts you at around 200lbs of rated thrust on the ground. Or at least before you modify the exhaust for lower thrust but higher exit velocity.

And yes, rated thrust was exactly what we were talking about.



No, you didn't introduce RATED thrust until your first error had been pointed out. Your post #9 in this thread does not include the word "rated".

Quote



Read a few comments up where we were discussing EDFs capable of 50-60lbs of static thrust, using multiple units for a total of 200lbs, which you then quoted me on.

If you still think I'm wrong, here's a design for an EDF powered plane at a very similar airspeed (97kts). Page 25 has the good parts. http://nari.arc.nasa.gov/sites/default/files/Kerho_TeDP.PhaseI.Final_.Report.ContractNNX13AB92A.pdf



The links you quoted previously indicated that depending on duct and fan design, the thrust can INCREASE above the static value as the speed of the machine increases, since the designs in question are optimized for forward flight.

The only value of any significance is the value at the design airspeed. The static thrust is irrelevant unless you wish to hover like a Harrier.
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
The problem is specifically with electric ducted fans since they have a low exhaust velocity (around 200mph) that does not increase with the aircraft's airspeed. So when flying at 100mph your thrust is about half of what it is on the ground. Turbines and jets don't have that problem.

Share this post


Link to post
Share on other sites
photognat

The problem is specifically with electric ducted fans since they have a low exhaust velocity (around 200mph) that does not increase with the aircraft's airspeed. So when flying at 100mph your thrust is about half of what it is on the ground. Turbines and jets don't have that problem.



An over-generalization. The change in thrust with airspeed is very dependent on the detail design of the intakes, the diameter of the exhaust tube, the pitch of the fan blades, the timing characteristics of the motor and speed controller, etc. The system is unlikely to be operating optimally when stationary.
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
Ok. Though don't we (wingsuits) fly at a comparatively high AoA (due to our shitty l/d ratio, below 1 right?) with very high induced drag? Doesn't that require much more thrust to maintain level flight? Just like the Hovering harrier whose AoA is at extreme levels during a hover and while transitioning to forward flight.

Share this post


Link to post
Share on other sites
nickfrey

Ok. Though don't we (wingsuits) fly at a comparatively high AoA (due to our shitty l/d ratio, below 1 right?) with very high induced drag? Doesn't that require much more thrust to maintain level flight? Just like the Hovering harrier whose AoA is at extreme levels during a hover and while transitioning to forward flight.



The L/D ratio is around 3:1 for a good flyer in a good suit. Maybe up to 4 for the best competition flyers.

That said, I don't think EDF is the way to go, since to achieve level flight at 100mph for a 200 pound jumper at 3:1 will still require around 20kW of power. Not sure I'd want that system atteched to my body.
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
Yeah, EDFs can be tuned for higher thrust at maneuvering speed, but you still can't cheat the fact that you're going to have 50% of the power once you reach 50% of the efflux. Not even NASA's team could.

kallend

The only value of any significance is the value at the design airspeed. The static thrust is irrelevant unless you wish to hover like a Harrier.



Spoken as a true academic. Static thrust is completely irrelevant except for the fact that it's what every EDF uses to rate its power. So yes, irrelevant until you leave the classroom and actually start building stuff like Travis.

Share this post


Link to post
Share on other sites
photognat

Yeah, EDFs can be tuned for higher thrust at maneuvering speed, but you still can't cheat the fact that you're going to have 50% of the power once you reach 50% of the efflux. Not even NASA's team could.

***The only value of any significance is the value at the design airspeed. The static thrust is irrelevant unless you wish to hover like a Harrier.



Spoken as a true academic. Static thrust is completely irrelevant except for the fact that it's what every EDF uses to rate its power. So yes, irrelevant until you leave the classroom and actually start building stuff like Travis.

What makes you think I haven't experimented with EDF?

And as the links YOU provided previously show quote clearly, the static thrust is highly dependent on the duct design, not only on the fan unit itself, so these "rated" values are rather iffy.

If you want to know what thrust you'll get at X mph, you need to measure the SYSTEM at that speed and not speculate based on some unreliable "rated" value at rest.
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
Quote

The L/D ratio is around 3:1 for a good flyer in a good suit. Maybe up to 4 for the best competition flyers.



L/D is around 2.2 to 2.5 for most good pilots. Numbers like 4 and up are a mix of wind and dive/flare used during competitions.
In no wind conditions, even the worlds best competition pilots barely reach 3:1 (and thats with a dive/flare).
JC
FlyLikeBrick
I'm an Athlete?

Share this post


Link to post
Share on other sites
I don't know why everyone is so stuck on level flight.... Strap one of these to each foot via a boot, add cutaway capabilities in case a battery goes bad (they catch fire not explode so its not like a land mine and if used within spec rarely have issues) and if it increases the glide ratio from 2:1 to 3:1 or even just 2:7 or something that would be awesome! We spend mass amount of time and money getting bigger suits and using gps to get the best glide ratio possible and this is a huge step in that endeavor! If I could afford it I would make some boots myself!

Share this post


Link to post
Share on other sites
Ion01

I don't know why everyone is so stuck on level flight.... Strap one of these to each foot via a boot, add cutaway capabilities in case a battery goes bad (they catch fire not explode so its not like a land mine and if used within spec rarely have issues)



Still not the kind of fire you'd want strapped to your body:

www.youtube.com/watch?v=fF9fhlr9S5s

Most LiPo fires are due to overcharging or to mechanical damage (like an impact).
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
mccordia

Quote

The L/D ratio is around 3:1 for a good flyer in a good suit. Maybe up to 4 for the best competition flyers.



L/D is around 2.2 to 2.5 for most good pilots. Numbers like 4 and up are a mix of wind and dive/flare used during competitions.
In no wind conditions, even the worlds best competition pilots barely reach 3:1 (and thats with a dive/flare).



I must read too much promotional material from suit manufacturers:D
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites
Boots?
Maybe not... => pilot chute in propeller nicht gut.

I´w been thinking about RC planes traveling at high speeds and how they are gaining their speed:

Made some calculations and figured that you could put a high pitch five blade propeller under your wing suit or even two contra-rotating propellers. One engine per propeller => fore motors EMAX GT4030/06 2000W)

whit one engine you can make at 1500m 3.3 kg of thrust and at 4000m it would be. 2.4 kg of thrust.

The propeller i calculated this: https://www.verticalhobby.com/kauppa/potkurinlapa-118-sg-p-3021.html

whit five blades an 15 pitch. Prob diameter would be like 30cm/11.8in

Calculations:
http://rcplanes.000webhostapp.com/calc_thrust.htm

I planed that the propellers would be behind another an that is going to reduce the maximal thrust but make it easier for the motors.

Some stuff ihaw already ordered or going to order for this project:

https://www.turbines-rc.com/en/heat-sink/1075-heat-sink-75mm-for-50mm-motor-and-ejets-jetfan-120-edf.html
http://www.goodluckbuy.com/mystery-90a-sbec-brushless-programable-electrinic-speed-control-myh-90a.html
http://www.goodluckbuy.com/emax-gt-series-420kv-outrunner-brushless-motors-type-gt4030-06-5-4kg-thrust.html
http://www.madpilot.fi/gens-ace-6200mah-222v-25c-6s1p-lipo-battery-pack-p-4381.html

I´m planing to strap the whole system to my chest area.
Whit cut away, heat protection, shrapnel protection, dead man switch

Lasse

Share this post


Link to post
Share on other sites
biggest issue with electric is how much thrust you lose at higher speeds. A 25 kg/thrust engine at 160 km/h cruising speed in a ws will provide (the numbers I was quoted) more added drag than thrust (due to the lower exhaust speed, almost no added thrust/push).

There, miniature jet turbine engines are a lot more efficient (900 km/h exhaust speed), but just shit in terms of added weight/fuel needed for longer flights.

Or so I hear...;)
JC
FlyLikeBrick
I'm an Athlete?

Share this post


Link to post
Share on other sites
You can upgrade the system:
Typhoon HET EDF 800-73 Motor 50mm 590Kv
and:
https://www.turbines-rc.com/en/50mm-brushless-motors/1425-hacker-e60-l-1y-motor-50mm-600kv.html

Propeller:
https://www.verticalhobby.com/kauppa/en/propellerblade-101-lh-p-637.html diameter 10.1IN/25.7cm

run propeller at its maximal RPM 1650

Prop tip speed 0.652 MACH

Prop's maximum Absorbed Power at 4000 meters 5742.8 watts => the motors listed above => going to heat and melt or something if that load is used.

In this concept you could change the number of blades and the Prop Pitch according to planed speed and wanted motor load.

Propeller estimated maximal flight speed 281mph, Static Pitch Speed :234.4mph

In theory you could run the motor at 16500rpm and make 5400gram push for one, 4xmotor = 21,6 kg of pusch whit optimal adjustments.

In theory if the motors dont heat/good cooling system:
whit 9.8kg of lipo batteries you could run it at maximum power at 16500rpm aprox 18000w around 50minutes.:|

If anyone finds an motor whit 10000W at 16500rpm or a similar one that would make it possible to run the propeller at maximum thrust at 4000m 5765gram, 1500m 7918 gram x4= 31,67Kg of thrust in theory.

I`m still going whit the Cheaper motors GT4030/06 cant afford: (920€ extra for better motors?) maybe in the future.

Share this post


Link to post
Share on other sites
kallend

***I don't know why everyone is so stuck on level flight.... Strap one of these to each foot via a boot, add cutaway capabilities in case a battery goes bad (they catch fire not explode so its not like a land mine and if used within spec rarely have issues)



Still not the kind of fire you'd want strapped to your body:

www.youtube.com/watch?v=fF9fhlr9S5s

Most LiPo fires are due to overcharging or to mechanical damage (like an impact).


The guy who tried to stomp out that fire in short pants, tennis shoes, and no socks, was a real trooper. ;)
Life is short ... jump often.

Share this post


Link to post
Share on other sites
Hmm

Starting to build the harness today.

I did e-mail manufacturer about the motors and they said it is fine to run them on a higher RPM if the load is OK.

Thought about landing in water.. a water tight main power and a water tight fuse for all lipo batteries.

B|
http://www.rchobby-avenues.co.uk/Hifei-Swordfish-Pro-300A-ESC-for-RC-Boat

Share this post


Link to post
Share on other sites
Got mail from Dualsky and there is on special order available a GA6000 280kv whit 8mm shaft => 15960RPM whit 14S lipo.

Static Pitch Speed : 226.7mph
Appx. Level Flight Speed (for RC plane): 272mph
Prop Diameter : 10.1 in
Prop Pitch : 15 in
calculated whit air density of 4000 meters (13123 feet)
Prop's Absorbed Power 2 blade :2495.4W
Prop's Absorbed Power 5 blade :5193.8W

In theory the system can be adjusted to wing suit speeds by changing these parameters:
Propeller Pitch and number of blades:
VARIOPROP 12C
adjustable upward gradient from
4,0'' (102 mm) to ca 15'' (381 mm)
blades 2-5

RPM 10s-14s (13160-15960rpm)
I`m getting totally exited B|

continuous 12000W/14.5Kg of Thrust

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account. It's free!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
0