wind vs. thermal

[Bill72pa]

I was thinking of getting a HLG for windy days when I don't feel up to flying my powered planes, but I can't really count on rising air. So the question is, do these planes need rising air, or could they climb on wind flowing parallel to the ground?

[Fast-Forward]

What would you consider a windy day in mph?

Keep in mind that typical HLGs weigh about 12-13.5oz. So the wind can bounce them around. There can be thermals on a windy day but, they move fast downwind and you'd need to travel with that thermal to stay aloft. If you want to take advantage of a windy day then try some sloping. It's ALOT of fun!

[Sparky Paul]

I was thinking of getting a HLG for windy days.. could they climb on wind flowing parallel to the ground?
.
No.
They go downwind.
Ano only downwind.
There must be a vertical component to the air mass for a glider to go up.

[Bill72pa]

I'd consider windy 20+mph.

Ah, the vertical component. That was what I was wondering. Didn't know if the lightness and the airfoil was enough to provide vertical lift in horizontal flowing air.

[cjv]

hlgs are great for light winds, you can a slope glide a lot of the hand launch stuff out there off of house roofs, dykes, walls, terraces, etc in winds that most slope gliders never will climb on...but they will just sink if theres no bumps in the terrain.

how about a powered glider? theres just too many times in the year where the lift is out of reach for handlaunch and too many places where setting up a bungee or winch is not cool, theyre usually heavy enough to penetrate 20+ winds too, maybe that would be your thing?

[sailhigh]

Bill72
Horizontal wind component will only push your plane back downwind. You need rising air to stay up. Virtually all gliders use either Thermals or Slope lift. Best to get a hold of the local soaring club and they can tell you where all the good spots are.
Best of luck.
Sean

[Bill72pa]

Thanks for the replies. I can't picture any slopes in the area of my flying field, and fields are very scarce around here. I think I'll try and pay more attention to possible rising air at my field to see if I would be able to use a hlg in the future.

[djnibler]

You won't want to fly a HLG in 20mph winds. I don't even like to fly a 3 meter in 20mph winds. When it gets that windy, thermals are often too broken up by the wind (not always, but more often than not). A little slope soaring would be the way to go here. If I were you, I'd get a 48 or 60" slope foamie. They are cheap, indestructable and a lot of fun. A lot like flying a power plane you will find. They can be very fast and about the only thing to do with them is aerobatics.

I got my foamie here
http://www.bowmanshobbies.com/
but there are a lot of other great vendors too.

Like cjv said, you don't need much of a slope. You'd be very surprised what will make slope lift!

[RSCherry]

Bill72PA-

Not many slopes here in our area of PA, and a HLG would not be suitable for winds in the 20mph range. Some of the local guys are sloping on the Pocono ski slopes, but usually in the fall when the wind picks up.

Bob

[Bill72pa]

I guess my original question was spurred by the fact that if you imagine a plane in a wind tunnel (airflow parallel to ground; i.e. no "rising air") it can ascend vertically when it increases it's angle of attack. So couldn't a glider climb in wind that is moving parallel to the ground, with no vertical airflow component?

[RSCherry]

no, because the airfoil (or glider) in the wind tunnel has an additional force that a glider in free flight does not- it has a forward force vector supplied by the mount that holds it in the tunnel.

In a powered plane, this forward force is supplied by the prop, and in steady state, level flight the force supplied by the prop exactly offsets the drag of the aircraft.

In a glider, this forward force is supplied by tilting the glider slightly nose down, so that the wing lift vector is actually tilted slightly forward, providing just enough forward force to offset the drag of the glider in steady state flight. Since drag is essentially lost energy, the energy to continue to move forward at the same speed must come from somewhere- and it comes from height. You trade potential energy (height) for kinetic energy (speed). To keep the glider flying at the same forward speed, you trade altitude for airspeed, a little bit at a time. Hence a glider will always be gliding down through the surrounding air mass.

A glider will rise relative to the ground if the surrounding air mass has an upward vertical movement that is greater than the gliders sink rate. It's important to note that the glider is still flying downward in that air mass at its usual sink rate, but since the air is moving up faster than the glider is sinking, the glider rises relative to the ground.

Hope that helps some.

Bob

[Miami Mike]

I guess my original question was spurred by the fact that if you imagine a plane in a wind tunnel (airflow parallel to ground; i.e. no "rising air") it can ascend vertically when it increases it's angle of attack. So couldn't a glider climb in wind that is moving parallel to the ground, with no vertical airflow component?Yes, but in that case we don't call them gliders, we call them kites.

[nuevo]

I guess my original question was spurred by the fact that if you imagine a plane in a wind tunnel (airflow parallel to ground; i.e. no "rising air") it can ascend vertically when it increases it's angle of attack. So couldn't a glider climb in wind that is moving parallel to the ground, with no vertical airflow component?

sort of, but only for a short while. The plane can gain altitude, but it gives up a lot of airspeed to do so. (imagine coasting a bicycle uphill. Higher, but slower). The plane cannot climb forever with no vertical component (lift) to the air.

[wakumann]

In case nobody notice this, your just discussed some of the areodynamic basics.
Normaly such things are discussed in the gas forum where quite alot of Guys don't know why some things stay up there, jus more trottle we do it anyway, or??

Cheers

Thomas

[Bill72pa]

Some very good replies. Thank you all.

[gustabmo]

theres just too many times in the year where the lift is out of reach for handlaunch and too many places where setting up a bungee or winch is not cool

You may use different names but I call it a hi-start a device that's very similar to a winch but powered by a rubber instead of a motor (winch). And I call it a bungee a much shorter length of rubber with no or a very short line on the end.

On my parlance a hi-start attaches to a hook under the wing of the glider, close to the CG, and a bungee attaches to a hook in the nose of the glider.

With these definitions in mind, a bungee is something very small and I'm pretty sure anywhere you have space enough to land a glider, you'll have space to bungee launch it. The only requirement is to have a low drag glider capable of flying at high speed without flutter, which is exactly the case of a HLG/DLG and of most slopers.

I think a ballasted DLG bungee launched will buy you lots of fun for your windy days, Bill.

Gustavo

[rcbrust]

Bill72pa & RSCherry,

I'm in southern Lehigh County and fly hand launch almost exclusively. Do either of you know of any other hand launch flyers or general soaring going on in our area? It would be nice to fly with someone for a change.

Thanks,
Randy

[Bill72pa]

Bill72pa & RSCherry,

I'm in southern Lehigh County and fly hand launch almost exclusively. Do either of you know of any other hand launch flyers or general soaring going on in our area? It would be nice to fly with someone for a change.

Thanks,
Randy

I'm just now getting into the handlaunch scene (just received my Great Planes Fling) to try it out. I don't know of any others in my area. I know there's a club in South Jersey that has some regular handlaunch meets and zagi fun flys. But that's probably a hike for you.

[rcbrust]

Yeah, South Jersey Silent Flyers. I've been to a couple of their contests. It's about an hour and 15 minutes from here though. The best I've found is to go to Valley Forge on Sunday mornings. They only allow quiet flying until 1:00 or so and I can get there in about 40 minutes. I haven't seen anyone else flying handlaunch, but at least there's other people soaring.

Randy