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astrbac



Joined: 02 Mar 2017
Posts: 3
Location: Zagreb, Croatia

PostPosted: Thu Mar 02, 2017 3:37 am    Post subject: Really basic question - making turns in a laminar wind Reply with quote #1   
Hi all,

as mentioned in my introductory post, I am not even a newbie (do not own any equipment nor have I tried hang gliding yet) but I have been thoroughly researchng my free-flying options . One question that comes to mind is this:

- how does one make turns into/away from the wind and manage speed in a hang-glider?

Lets say we are at the beach, Fort Funston for example. There is a nice afternoon sea breeze blowing into the ridge. Upon hitting the ridge the airflow turns upwards and provides lift - all clear. Hang gliders are going back and forth, paralell to this ridge, exploiting the lift.

Now, If I was in an airplane, this would be considered as flying in pure crosswind (coming from 90deg) and I would really have to crab a lot and fly sideways. How do hang gliders manage to fly parallel to the ridge?

Also, when they want to turn back 180, they turn either into the wind (over the sea) or away from it (into the land). In the first case - they have headwind, slower ground-speed, lots of lift, basically no problems, right? But if they turn towards the shore, then there will be lots of tailwind, ground speed will increase, making it a bit more difficult to complete the turn back into the crosswind Smile .

While initiating the turn the wing closer to the sea will be at risk of wind hitting it harder from below, possibly "turning" the glider upside down, no?

Pardon my ignorance, as I said - a complete newbie here. Cheers!
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red
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PostPosted: Thu Mar 02, 2017 4:28 am    Post subject: Really basic question - making turns in a laminar wind Reply with quote #2   
astrbac,

Too much thinking, not enough watching. Smile We have tons of videos here, and you can see almost any type of maneuvers possible with a hang glider. Short answer: A glider in good trim will fly itself at the right airspeed. You may want to gain some extra speed (not a lot extra) when turning downwind, but nothing extreme will happen if you just copy the safe turns made by other gliders at your site. Unless you are crossing over a cliff edge at very low altitude (which is never a smart move), you normally won't find air that can flip you upside down.

Watch and listen to this guy. NMErider means "No More Excuses Rider." He has lots of videos that he has narrated, and edited. You can hear his variometer beeping in lift, and see how he turns to stay in the lift and climb. You can watch this video in pieces. You do not need to watch the entire video in one sitting. Just write down the time (next to the speaker icon) where you stop, and re-start the video there later.


Link

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astrbac



Joined: 02 Mar 2017
Posts: 3
Location: Zagreb, Croatia

PostPosted: Thu Mar 02, 2017 4:32 am    Post subject: Reply with quote #3   
Thanks a lot for the reply! Sorry, I might be in an "overthinking" mode Smile indeed. I am currently all into my aerodynamics class so I try to apply what I know to all aircraft.

Will watch the videos and report later ;).

Cheers!
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blindrodie
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PostPosted: Thu Mar 02, 2017 5:42 am    Post subject: Reply with quote #4   
Keep after it. For a lot of us, overthinking our love of hang gliding is normal. Always the student!

Cool

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BubbleBoy
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PostPosted: Thu Mar 02, 2017 7:56 am    Post subject: Reply with quote #5   
Thinking about this stuff is great -- never stop.

The first thing to remember is that you don't have to do *anything* different to maintain airspeed when turning *upwind* or *downwind*. This is because with the hang glider (or any other aircraft) totally immersed in the laminar airmass, there is no "upwind" or downwind".

The thought that the glider will behave differently in an upwind vs downwind turn in smooth laminar flow is a myth.

(note: when turning steep and very close to the ground where gradients can be severe, there can be implications regarding upwind vs downwind turns that one should be aware of, but not in the basic boating around Funston ridge soaring upon which the question was asked).

JB
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TomGalvin
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PostPosted: Thu Mar 02, 2017 9:19 am    Post subject: Re: Really basic question - making turns in a laminar wind Reply with quote #6   
astrbac wrote:
Now, If I was in an airplane, this would be considered as flying in pure crosswind (coming from 90deg) and I would really have to crab a lot and fly sideways. How do hang gliders manage to fly parallel to the ridge?


We don't fly parallel in a cross wind. We crab too. Very generally, the velocity of the wind and the glider are lower on a ridge than a plane at altitude so the crab angle may not be as noticeable. When the velocity on the ridge is high enough to require a significant crab angle, it is generally a good idea to leave the glider strapped to the truck, and tell tall tales with other pilots while waiting for the winds to subside.

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RobertKesselring
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PostPosted: Thu Mar 02, 2017 10:21 am    Post subject: Re: Really basic question - making turns in a laminar wind Reply with quote #7   
TomGalvin wrote:
When the velocity on the ridge is high enough to require a significant crab angle, it is generally a good idea to leave the glider strapped to the truck...


My favorite conditions are a wind speed about half my typical air-speed. This results in a crab angle of about 30 degrees away from the mountain. I like this because getting instantly turned by 30 degrees by an invisible dragon is a regular occurrence where I fly, and I REALLY don't like being pointed at the mt. side after getting smacked by one and losing 200' of altitude.

Besides that, the stronger conditions produce a wider lift band and I can stay further away form the mt.

But don't pay too much attention to my opinions. I'm still a noob who's been flying for less then 2 years.

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TjW
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PostPosted: Thu Mar 02, 2017 7:22 pm    Post subject: Re: Really basic question - making turns in a laminar wind Reply with quote #8   
astrbac wrote:
Hi all,

as mentioned in my introductory post, I am not even a newbie (do not own any equipment nor have I tried hang gliding yet) but I have been thoroughly researchng my free-flying options . One question that comes to mind is this:

- how does one make turns into/away from the wind and manage speed in a hang-glider?

Lets say we are at the beach, Fort Funston for example. There is a nice afternoon sea breeze blowing into the ridge. Upon hitting the ridge the airflow turns upwards and provides lift - all clear. Hang gliders are going back and forth, paralell to this ridge, exploiting the lift.

Now, If I was in an airplane, this would be considered as flying in pure crosswind (coming from 90deg) and I would really have to crab a lot and fly sideways. How do hang gliders manage to fly parallel to the ridge?

Also, when they want to turn back 180, they turn either into the wind (over the sea) or away from it (into the land). In the first case - they have headwind, slower ground-speed, lots of lift, basically no problems, right? But if they turn towards the shore, then there will be lots of tailwind, ground speed will increase, making it a bit more difficult to complete the turn back into the crosswind Smile .

While initiating the turn the wing closer to the sea will be at risk of wind hitting it harder from below, possibly "turning" the glider upside down, no?

Pardon my ignorance, as I said - a complete newbie here. Cheers!


The wing doesn't know which direction the wind is blowing. As far as it's concerned, the wind always comes from the front, at the commanded angle of attack. If the wind comes from some other direction momentarily, it will try to yaw into it because it's yaw stable. Because it's also pitch stable, if the wind comes at a higher or lower than commanded AoA, it will pitch down or up to correct itself.
So turning upwind doesn't give you more lift, and turning downwind doesn't give you less. The groundspeed does change, of course, and the radius of the turn will change, so turning downwind you will need more clearance from the hill than you would need in no wind, but that's not due to a loss of lift. That's just because you really are going faster relative toward the hill than you would be in no wind.
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flybop
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PostPosted: Fri Mar 03, 2017 2:53 pm    Post subject: Reply with quote #9   
All pilots, especially those of us who often fly close to terrain, need to understand the difference between ground speed and airspeed.

Here's an example that a flight instructor used: You drive a car in a circle with a 10 mph wind from the north at a steady speed. Your ground-speed will remain constant and your airspeed will change with direction. Airspeed highest with a N heading and slowest with a S heading.

Now, if you fly an aircraft in a circle with a steady wind from the north your airspeed will remain constant and your ground speed will change throughout the turn. Slowest with a N heading and greatest with a S heading. Provided that you are flying a constant rate turn. Your track over the ground will drift with the wind.

This is crucial to understand when ridge soaring and when setting up your approach to land. Never, ever turn toward the mountain until you are safely above the top!

Good luck and keep us posted.

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Melodie Plata



Joined: 18 Mar 2017
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PostPosted: Sat Mar 18, 2017 2:24 am    Post subject: Reply with quote #10   
Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorized foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered with synthetic sailcloth[1] to form a wing. Typically the pilot is in a harness suspended from the airframe, and controls the aircraft by shifting body weight in opposition to a control frame.
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TjW
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PostPosted: Sun Mar 19, 2017 6:00 am    Post subject: Reply with quote #11   
Melodie Plata wrote:
Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorized foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered with synthetic sailcloth[1] to form a wing. Typically the pilot is in a harness suspended from the airframe, and controls the aircraft by shifting body weight in opposition to a control frame.


So where's your footnote?
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aeroexperiments
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PostPosted: Mon Mar 20, 2017 8:34 pm    Post subject: Re: Really basic question - making turns in a laminar wind Reply with quote #12   
astrbac wrote:

Now, If I was in an airplane, this would be considered as flying in pure crosswind (coming from 90deg) and I would really have to crab a lot and fly sideways. How do hang gliders manage to fly parallel to the ridge?


It's exactly the same in the hang glider as in the airplane. We often fly very sideways-- relative to the ground.

When turning to begin a new leg along the ridge, you just continue the turn as long as is needed to get the needed crab angle. In practice this means you end up turning through less than 180 degrees of heading change to do a 180 degree reversal of the ground track. But you don't really think about the crab angle or the heading change, you just think about whether or not you are getting the ground track that you want. If not, adjust your heading as needed. The nose will always be pointing somewhere between the direction of the ground track that you are achieving, and the wind direction. Since you can easily look straight down, and the nose is way up above your normal line of vision, it's often the case that you are much more aware of your ground track than the direction the nose is pointing, which is fine. If you are drifting back behind the ridgeline or moving forward out over the ocean, you'll notice it right away, and the required correction is quite instinctive-- a slight turn takes care of it and you're back on track. It's not like you are constantly thinking about what crab angle you need to set.

You aren't one of these guys who thinks that when you do the same thing in the airplane, you are flying sideways relative to the AIR, are you? That would require you to hold lots of pressure on one of the rudder pedals. I have much faith that you aren't doing that or imagining that you are doing that.

Happy hang gliding!

Steve
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