Wind Tunnel is not the same as Skydiving

[Ron 7]

Quote

Not to mention the good food and lovely weather...

]

I actually like Banngers and Mash with brown sauce.
There is a cool little Pup/Resturant near the Orlando Tunnel that Derrick Thomas (A britt) took us to a few times.

It totally changed my thoughts on English food.....

Your weather still sucks

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[Shark 0]

Quote

Your weather still sucks

Actually, it blows!!!!

[Eule 0]

Quote

Multi fan tunnels almost seem to loose lift in one or more fans at a time. (Not maybe the best
explanation...But it is how it feels).

I wonder if it could have anything to do with the relative phase of the fan blades. In other words,
when the air gets to the fan in a single-fan tunnel, all it has to deal with are the blades of that one fan
plus whatever support structure there is for the motor/engine/driveshaft. When the air gets to the
fans in a multi-fan tunnel, it not only has to deal with the support structure, but with several fan blades
that probably aren't synchronized with each other. If one fan blade has just gone by and sucked up a
lot of air, the blades on the other fan(s) that spin by that spot next won't have a lot of work to do.
This might tend to make the flow rather unevenly distributed across the diameter of the tunnel, at
least near the fans, and affect how it responds to "blockages" in the test section.

I'm pretty sure the control gear in multi-fan tunnels tries to hold all the motors at the same RPM, but
I don't think it's designed to keep the blades in phase. Even a small difference between the RPM of
two motors would allow the blades to get out of phase fairly quickly, and the control gear probably
has a tolerance of several RPM either way.

To put it another way, imagine a guy standing in the middle of a field with a bass guitar and a 100
watt amp. When he plucks a string, the time it takes for the first pressure peak to hit your ear
depends on how far away from the amp you are standing, BUT that time won't change unless you
get closer to or further from the amp. If four guys each have a bass guitar and a 25 watt amp,
and they all hit the same string at the same time, you'll still get beat notes from the guitars not
being *perfectly* in tune and not being played at *exactly* the same time. Plus, the timing of the
beats will vary as you change your position relative to the amps, even if you keep the same distance.

I dunno. I wonder how annoyed the various operators would get if the geek patrol showed up at
their tunnels with some high-speed cameras and a truck full of smoke canisters. "Hi, we're here to
Advance Science, or at least settle several beer bets!"

Eule

PLF does not stand for Please Land on Face.

[Paulipod 0]

Quote

I dunno. I wonder how annoyed the various operators would get if the geek patrol showed up at
their tunnels with some high-speed cameras and a truck full of smoke canisters. "Hi, we're here to
Advance Science, or at least settle several beer bets!"

If you are paying by the hour I dont suppose we'd care

Bodyflight Bedford
www.bodyflight.co.uk

[Ron 7]

That is the question I have. However, you wrote it SO much better than I could....Thanks.

I think there is a major difference between a single fan and multiple fans. I have always thought it had to do with the airflow and how it changes with several fans.

I can tell from exp that at Bragg (The biggest single fan tunnel I have been in, I don't count the old outside open fans of the early 90's) that I don't feel the washing around I feel in a multi fan tunnel. The only reason I can only guess that the reason is one fan loses lift and the others pick up the slack. The loss of lift on that one side is seen in how a 4way team just sitting there then all of a sudden on guy goes low.

I have actually found that the effect makes a team work even better in freefall IMO.

Now that I am flying RC helicopters I have seen how hard it is to change both speed and pitch on a single fan to keep the blades from over speeding, or lugging....I can't imagine the grief of getting more than one to work together while all have only a certain flow rate to work with.

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[Nicodemus 0]

Quote

I actually like Banngers and Mash with brown sauce.
There is a cool little Pup/Resturant near the Orlando Tunnel that Derrick Thomas (A britt) took us to a few times.

It totally changed my thoughts on English food.....

GOOD English food is really, really good. There's just a lot of bad stuff about, which gives us the bad rep. Especially in Bedford!

(Out of interest I did actually find somewhere close to the tunnel that does awesome English pub grub. Their card is pinned to our noticeboard. Best if you're not veggie, though!).

Quote

Your weather still sucks

Gorgeous outside today! Just been drinking a cuppa, out on the roof. I should really be at the DZ...

[Nicodemus 0]

Quote

Result?? The light guy on the team needs more lead to stay with his teammates. I'm sure the real situation is much more complicated than this, but I suspect this is where a bunch of the difference in "feel" is coming from. This also leads me to guess that a single belly-flier probably won't notice as much difference in the various size tunnels as would 4-way teams.

This is a convincing argument and I like the explanation.

I thought I'd mention though...

A VERY experienced freefly coach came back to visit us in Bedford recently after spending some time in S.V. tunnels.
Soon as he turned up he flew, SOLO, and left the chamber talking about how 'soft' and freefall-like the air is in Bedford. How different to S.V. air it was.
(This is not a plug. I don't mean to say 'better' or 'worse'. Just 'different').

Now, I've never flown in a S.V. tunnel, but I get to talk to a lot of people who use both theirs and ours. Their opinion seems to be the same. In both tunnels the air feels good - but ours feels, well... different. Softer. (I don't mean less responsive. Just softer somehow).

So, I don't know the reason, but, yes, your average flyer (well, Fabian isn't your average flyer but you know what I mean) does seem to be able to tell the differerence, even if flying solo with lots of space left for the air to flow around him.

Hmm...

[dirk.baumann 0]

Quote

[...] Especially in Bedford! (Out of interest I did actually find somewhere close to the tunnel that does awesome English pub grub. Their card is pinned to our noticeboard [...]

Quote

Hey,

sounds interesting, whats the name of this pub ypu speak of?

• Quote

Share this post

---

Link to post

Share on other sites

[Saturn27 0]

First to comment on the original question of this thread which I believed has been answered, but I will reinforce it. The first time I was in the tunnel to do belly flying, I had ~ 100 jumps. I was very unstable in the beginning, and it was very difficult and sometimes frustrating to realize how much you do move around. I know have ~7-8 hours of tunnel time, and I have realized that it just takes time and some good coaches. I know it costs a bit more, but you will definitely see an improvement in your skydiving skills.

On the second portion of this thread: All of my time has been in Skyventure tunnels. I would say I have about an hour in Arizona, an hour or two in Perris, and the rest in Orlando. Typically I get about 20-30 minutes of flying in an hour, and I have without a doubt noticed a difference in the air at each place. I would say that it seems much more difficult to move in the Orlando tunnel. Flying in the mantis position, my arms get tired much more quickly in Orlando, and it seems that it takes more effort. I found that flying in the Perris tunnel and at Arizona felt much more like it does in freefall - much more effortless.

[ladyhawke 0]

I was having horrible problems with my 360 turns. I would look to turn left and end up spinning the opposite direction, going backwards, floating up, totally out of control! My AFF instructors and I worked very hard on trying to correct my legs, arms & feet. I was so frustrated and discouraged with myself because I wasn't able to "get it". So, I decided to go to the wind tunnel in Eloy. For me, the tunnel was very much like freefall. It took several sessions, but the time and excellent instruction paid off. When I went for my level 5 jump, my turns were slow and I didn't spin! I'M SO HAPPY! I still have lots of work to do, my turns aren't perfect but at least I'm TURNING and not SPINNING!

I believe the tunnel helped me to finally understand how it's suppose to FEEL! Plus the tunnel was fun, fun, fun!

"It is our choices that show what we truly are far more than our abilities." - A. Dumbledore

[4wayFly 0]

Quote

That means that a 4-way team will have an area of about 12 sq. ft, which in the 12 ft tunnel represents about a 10% blockage of the tunnel, but only about a 6% blockage of the 16 ft tunnel. If the undisturbed airspeed in both tunnels was 120 MPH, then to get all that air past the tunnel fliers, the air has to pass the fliers in the 12 ft. tunnel at about 132 MPH, but only 127 MPH in the 16 ft tunnel.

Result?? The light guy on the team needs more lead to stay with his teammates.

Just to continue on from/ update this theory..I have recently flown in Eloy for the first time and definitely did not have to wear as much lead as in the 12ft SV tunnels, even with heavier people. So that would support the idea that diameter is the key factor in how it 'feels'. Meaning...uh...the smaller you are, the bigger the tunnel you need?*

* This is a *joke*. Althouh bigger tunnels for all sounds like a good idea

[Eule 0]

Quote

I think there is a major difference between a single fan and multiple fans. I have always thought it had to do with the airflow and how it changes with several fans.

Thinking about it some more, smoke would be good for showing you _where_ the airflow is, but not so good at _how fast_. What would probably work better is deploying a matrix of anemometers throughout the test section and comparing readings. Yes, the anemometers themselves will change the flow a little, but almost any type of measurement you make will do that. Also, they won't block the tunnel nearly as much as four people will, I think.

A way to see if the fans are causing it might be to put a high-speed video camera between the test section and the fans (SV-type total-loss tunnel), point it at the fans, and record it split-screen with the normal tunnel cam. Then review the video, and see if one guy going low in 4-way is reliably synchronized with a certain blade position of the fans. You could also do this on an SV-type recirculating, but you'd need two cameras with lights for the fans. (I wonder if SV Colorado behaves the same way as Eloy, Perris, or Orlando - all have multiple fans, but the recirculating ones also have two airflow paths instead of just one.)

It occurs to me that _somebody_ must have done something like this in order to build these things in the first place. I would guess that they probably built fairly large scale models and attacked them with smoke, ribbons, anemometers, etc. You probably don't get to see this data unless you've signed an agreement to build one, though. I would further guess that the first full-size version of each design was similarly attacked with measuring instruments before it was opened.

Quote

Now that I am flying RC helicopters I have seen how hard it is to change both speed and pitch on a single fan to keep the blades from over speeding, or lugging....I can't imagine the grief of getting more than one to work together while all have only a certain flow rate to work with.

I don't _think_ most of the current tunnels adjust the pitch on their blades, just the speed, but I could be wrong. I do know that the tunnels I've been to all have three or four refrigerator-size boxes for the control gear. Some of this is just to handle the electrical power levels involved, but a reasonable chunk of it is probably data acquisition and processing - they have more computrons than an RC transmitter and receiver.

Eule

(Yes, this is a late reply; I'm catching up on a backlog.)

PLF does not stand for Please Land on Face.

[Paige 0]

Quote

I would say that it seems much more difficult to move in the Orlando tunnel. Flying in the mantis position, my arms get tired much more quickly in Orlando, and it seems that it takes more effort. I found that flying in the Perris tunnel and at Arizona felt much more like it does in freefall - much more effortless.

This seems strange since the Perris tunnel is much slower than SVO (we had the upgrades a few years ago). Perris tops out at 125mph (according to 2 instructors I met in Vegas) and SVO tops out at 136mph. AZ is just a monster and super fast so that makes sense it would be easier to fly.

Interesting observation girl, great food for thought. Thanks for the post. Glad to see you are making your rounds to the tunnels. I leave for Eloy Wed. next week to fly a few hours, I can't wait!

In my post 'Tops out' isn't the fastest the fans can go just what they normally give people for freeflying.

Tunnel Pink Mafia Delegate
www.TunnelPinkMafia.com

[rehmwa 2]

Quote

Quote

I would say that it seems much more difficult to move in the Orlando tunnel. Flying in the mantis position, my arms get tired much more quickly in Orlando, and it seems that it takes more effort. I found that flying in the Perris tunnel and at Arizona felt much more like it does in freefall - much more effortless.

This seems strange since the Perris tunnel is much slower than SVO

Maybe it's more of a 'when' and 'how fit' thing for her personally, than which of the two tunnels she flew at that impacted her fatigue levels. I'd doubt any of the tunnels was maxed out for someone flying mantis.

Tired arms would be a sign of higher pressurization, not less. possible also an issue of who she was flying 'with' and maybe they were training a stronger body position in Orlando. I know if I'm flying a good mantis, I feel a LOT more pressure/force with my arms than when I'm flying a sloppy body position. (It's like doing 20 pound arm extension exercises vs 5 pound reps - maybe more)

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[Ron 7]

Quote

I don't _think_ most of the current tunnels adjust the pitch on their blades, just the speed, but I could be wrong.

A sorry my point was it is hard to run one est of blades without a poblem. I can't imagine having 4-5 trying to all run with each other with a limited intake. It seems to me that one fan might lose air to another.

I'll be in CO this weekend. It will be interesting to compare a SV recirc tunnel to an open air tunnel. And see the differences to the Bragg tunnel.

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[diablopilot 2]

Quote

This seems strange since the Perris tunnel is much slower than SVO (we had the upgrades a few years ago). Perris tops out at 125mph (according to 2 instructors I met in Vegas) and SVO tops out at 136mph.

According to what instument of measure?

I am sure Perris is able and regularly provides airspeeds higher than 125mph.

----------------------------------------------
You're not as good as you think you are. Seriously.

[Ron 7]

Quote

According to what instument of measure?

I am sure Perris is able and regularly provides airspeeds higher than 125mph.

From my personal exp, I found the Perris tunnel to be slower than Orlando. It might be due to elevation, power, or me being crazy. But I did not get the same feeling from both tunnels, and the driver told me he had it cranked up.

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[Paige 0]

Quote

Quote

This seems strange since the Perris tunnel is much slower than SVO (we had the upgrades a few years ago). Perris tops out at 125mph (according to 2 instructors I met in Vegas) and SVO tops out at 136mph.

According to what instument of measure?

I am sure Perris is able and regularly provides airspeeds higher than 125mph.

No clue, as I said before it was from the mouth of 2 instructors there and I'd assume they know what they are talking about. Maybe not.

What airspeeds are the capable of or give? I'd like to know before I go fly there. Everyone from Orlando that flies there says its SUPER SLOW.

Tunnel Pink Mafia Delegate
www.TunnelPinkMafia.com

[mattjw916 2]

Many of my friends would concur that Perris is slow(er) too. Some of them aren't too happy with the speeds in Orlando either though. Apparently it's hard(er) to get lift headdown in a tight suit for the 6ft tall male crowd... For RW though, it's not much of big deal it seems. It's been a couple years since I've been to Perris personally though (but I'll be there in a couple weeks, in theory, so I guess I'll refresh my memory).

Based on % power a tunnel has to be run at for me to freefly comfortably, Colorado is the strongest I've flown in. I freefly at about 85% power in Eloy and somewhere in the low-mid 70s in CO. The CO tunnel at 85% (which actually means 85% of 90% total power available since they have it limited) would probably pin me to the turnvanes in anything but the fastest stand I could manage without corking or at least preclude me from flying down into the glass area where the airspeed is highest.

edit: too add that the power setting in CO tunnel would be with the louvers closed, or close to it, restricting outside air from entering.

NSCR-2376, SCR-15080

[Paige 0]

So no info on Perris?

I can fly anything so the speeds don't mean all too much to me. If you are a good flyer you learn and adapt your flying style to suit your environment. Flying slow is harder than fast, I highly suggest learning to fly both fast and slow air. You will only become a better tunnel flyer and skydiver.

Tunnel Pink Mafia Delegate
www.TunnelPinkMafia.com

[mattjw916 2]

I flew so long ago in Perris that I didn't pay attention to power settings back then... I'm pretty sure from what I heard that I could just fly it maxed out now (esp in my fast VRW-style suit), but I guess I'll find out for sure soon.

As for "flying in anything" I'm pretty sure I am a _lot_ heavier than you so I'm going to need a bit more power so I don't have to "slow-fall" constantly. Besides, I like the faster air, it feels more like the sky to me. And while I can fly in a slow sit at ~115 in the tunnel, it's just more realistic to me at ~125+ since I learned how to sit-fly in the sky.

In the end, it's just personal preference.

NSCR-2376, SCR-15080

[Paige 0]

Quote

I flew so long ago in Perris that I didn't pay attention to power settings back then... I'm pretty sure from what I heard that I could just fly it maxed out now (esp in my fast VRW-style suit), but I guess I'll find out for sure soon.
Bummer, maybe someone else can help us out. I'd love to know, I want to go fly next year and I will regardless of airspeed but I'm just curious. I don't care what unit of measurement % or mph, just a rough idea would be cool other than it's slower than SVO. What is it topped out at for freeflying (the general population not w./paying for extra air speed).

***As for "flying in anything" I'm pretty sure I am a _lot_ heavier than you so I'm going to need a bit more power so I don't have to "slow-fall" constantly. Besides, I like the faster air, it feels more like the sky to me. And while I can fly in a slow sit at ~115 in the tunnel, it's just more realistic to me at ~125+ since I learned how to sit-fly in the sky.

In the end, it's just personal preference.

There is a 6 foot something instructor at SVO who isn't skinny (but is losing weight and looking good), he can fly his body and is amazing. Maybe you know him if you've visited, it's my big teddy bear Eddy!

I've flown w. heavy men who make me look like the amature I am. Eddy being only one of them. I've also had the pleasure of flying w. the owner of AAC, he's not big but he's no twig either.

No doubt it is all personal preference. That's the best part about all the tunnels popping up

Tunnel Pink Mafia Delegate
www.TunnelPinkMafia.com

[Avion 0]

Well, it seems you got quite some response on this question.

With what time I have in the tunnel, I have found it necessary to wear 20-25lbs of lead to get the same feel from the air. The reason for this is simple, my rig weighs 23lbs. Without weight, I fly at 115 in the tunnel. The air at this speed is noticably, spongier, for lack of a better word, basicaly less consistant and less firm. When I wear the weight the air feels almost exactly as it does in the sky, firm and stable. and I fly at 135 according to the readout.

Cheers,

BW