Sylmar Hang Gliding Association

This Saturday we are going to make some minor changes to the launch. The first will be to flatten the top section somewhat to make it easier for a nose wire person to hold the wires while the pilot is out into the main airflow.

The plan is also to move some dirt such that the launch run is raised slightly making it easier for wire people to move around and under the wings when retreating. We will have a pow-wow on the summit Saturday and I hope we will reach a consensus on how this should be done.

There has been some question as to whether the tendency has been for the right or left wing to be lifted in blown or near-blown launches in the last few months. I'm aware of two, Marshall's posted in this forum, and Lynn's in which both had right wings lifted. What has been the experience of others?

2 out 3 launches from the new ramp for me had my glider suddenly roll and yaw to my left even though the wind in my face had not changed. I witnessed numerous sudden yaw-rolls to the left on other gliders but none to the right. Before I wound up on the I-D List I had switched to the PG saddle anyway.

From over 200 launches from the old ramp in five years under ll kinds of conditions I never had a wing rise without an accompanying switch to the wind in my face. Careful viewing of old videos an frame stills showed that the old ramp was a hemispherical knob.

I know it's not possible to satisfy everyone but I'd love to have the old ramp back as much as possible by the time I'm back in 2017......

I often experience ramp suck. Most pilots probably don't feel it but I have heard of others who do.

Neon Jon wrote: Careful viewing of old videos an frame stills showed that the old ramp was a hemispherical knob.

Careful viewing of that second still shows that the whole world is a hemispherical knob.

A comment relating to Lisa's post about ramp suck, and the earlier post about making the top flat:

Flat tops with sloping ramps are often what makes ramp suck. Suck is frequently caused by the push from the rotor generated by the sudden change of ramp slope. The smoother the change in slope, the less likely you will have suck. Suck is common on cliff launches for that very reason, and rare on slope launches for the opposite one.

For whatever it's worth. I haven't flown the new ramp but a couple of times, so I haven't got much to say about it, except for the theory.

I wonder if the drop off behind the ramp to the set-up area isn't part of the issue? It amplifies the ramp slope change. Just a thought. I cannot be there this weekend to help. Sorry. Have fun!

George is almost always right, but I've got to disagree with him this time. I think that the "ramp suck" is just the forward tilting of the wing's lift vector that results from the upslope flow.

I do not know much about this on a mathematic level and I know my blown launch was my fault entirely,point in case. Pilot error. Im going with Jon on liking the old ramp better but both are fine. Ill be there tomorrow to help sculpt it into whatever shape you want. If you got some dynamite we might make a nice cliff launch,haha

Greg Kendall wrote:George is almost always right, but I've got to disagree with him this time. I think that the "ramp suck" is just the forward tilting of the wing's lift vector that results from the upslope flow.

I've seen measurements done on ramps back east. (Streamers moved around to test the flow.) If the ramp is shaped with significant direction change in the flow, the wind blows from the back of the glider and "pushes" it off. I'm not saying that Greg's explanation isn't right. I am sure that he is right. But what I was talking about was the stuff I've seen even standing on the top of the ramp, with the lift vector pointing close to straight up (or even slightly backwards). That is caused by ramp shape - assuming it isn't actually blowing down...

I'd never argue with Greg about aerodynamics. He knows far more than me on that subject. But I suspect we were talking past each other here. Having lived where ramp suck is common (as is Greg's forward component issue), I can see how we could be talking about two different things, that appear at first glance to be the same thing. (And to the pilot in command, feel nearly identical.) Both are real effects. Whether the ramp shape issue is/was there at Kagel is another matter - I suspect it was a bit, but not very much.

Of course, I have no idea where Lisa was standing, or her glider's nose attitude at the time to which she was referring. If she was on top with the nose not lowered, I doubt it was Greg's explanation. If she was forward and ready to launch, I doubt it was mine.

Cheers.

My understanding is what Greg may be describing could be when the glider is fully onto a steep ramp in the free airflow coming up the ramp, the glider is trying to fly away from the ramp. That's not what I call ramp suck. That's just a flying glider still on the ramp.

I have experienced ramp suck and it takes places anywhere that there's rotor kicked off the lip. I have experienced ramp suck 20' back from the lip of certain ramps when the wind is the right velocity. I have top landed on the bluff at Casco Township, Michigan only to get lifted up from in back and blown right off the edge of the bluff into a 25mph breeze and soared away having to land elsewhere. That to me is ramp suck. It seems to crop up wherever the wind rotors off the lip of a ramp. That rotor can migrate fore and aft too. When you have a steep ramp with a sharp lip you can get ramp rotor (ramp suck).

There's also another phenomenon. Let's call it ramp thermal. Towers is notorious for ramp thermals that come tearing up the face of the mountainside and then grab one wing or the other and make your glider want to pull a ground loop, turtle or even lift off while there's no wind. I'm sure Kagel get ramp thermals. I recall some Jerry Garcia-looking, ham operating, Saturn pilot getting hallway turtled while walking behind the old Kagel ramp. If I ever see him do that again I will be sure he signs my waiver before I offer assistance.

I have seen a video of at least one pilot who did not make an aggressive launch run and a ramp thermal picked him up and sent him face-first back into the top of the plateau. His whole body crunched up on impact. Scary to watch but he did get a free helicopter ride for his troubles. This happened long before the ramp was reconfigured. I think it wa just a hazard of thermic conditions.

I suppose there's no reason you can't have a calm day and the setup area heats up beyond the lapse rate. When a breeze comes along and kicks a little bitty ramp rotor that kicks off a gnarly dust devil in the setup or walk-up area. Next thing you know your glider is lifting up hard before you even reach the ramp threshold (lip).

Architects have software and wind tunnels to test for mechanical aspects of wind phenomenon. Buildings do shake and make tenants nauseous or accelerate the prevailing breezes into a nasty venturi or a series of eddy currents. Lot's of stuff going on out there. It's not always so cut and dried.

My 2p worth

The rotor push vs tilted lift vector question can easily be answered with some flow visualization, like streamers, soap bubbles, or just kicking some dirt.

Could there be a rotor or other turbulence on the ramp, caused by the sharp transition of the retaining wall? Just wondering...

I think I still have a line on a professional-grade smoke machine, if anyone is interested. Or I can make some bubble solution for the hardy pilot who wants to stand below launch. And, if Jonathan has the appropriate waivers, maybe he'll record it from the side.

Jim wrote:....Or I can make some bubble solution for the hardy pilot who wants to stand below launch. And, if Jonathan has the appropriate waivers...

Is my bubble waiver appropriate?

I think not. She's cute but shorter than the retainer. I'm afraid it's got to be you. Don't worry, I can notify Camp 9 to have the heli crew ready for you, just in case. No one else will touch you, especially, if you have self-diagnosed, internal organ injury from this project. But you need to sign the waiver for me, anyway.

$16.99 at Toy Czar US, Jim. Waiver not required.

Jim wrote:...No one else will touch you, especially, if you have self-diagnosed, internal organ injury from this project. But you need to sign the waiver for me, anyway.

Jim,

I know you have a great dry wit and I appreciate it a great deal. You are a gem in the club. But all kidding aside for a moment, I hope pilots take the possibility of unchecked internal bleeding or organ damage seriously.

A few years ago we had a pilot at Crestline fly XC then badly blow an out-landing on Hwy 330 below the ranger station. He insisted on breaking his glider down before doing anything about the way he was feeling and the fact he'd slammed in hard. Another pilot had to talk him into walking up to the ranger station to seek help. He was immediately transported to Loma Linda where they did emergency surgery that evening for a ruptured organ.

It's great to keep things whimsical and light so we don't fall into the rut of taking ourselves too seriously. We can get injured and call for help while keeping our sense of humor. It's much easier on the rescuers that way. At least that's what they tell me. I certainly wouldn't know from first-hand expereince.

Jonathan! You sly devil.

And, seriously, what's everyone's take on the forward lip of the ramp and the effect of the bushes in front of the saddle? Empirically, it would seem that there isn't much or there would be many more complaints. Or is it that the wind velocity is not great enough?

Jim wrote:....And, seriously, what's everyone's take on the forward lip of the ramp and the effect of the bushes in front of the saddle? Empirically, it would seem that there isn't much or there would be many more complaints. Or is it that the wind velocity is not great enough?

I hope I get well enough to get back out and launch the new ramp before plate tectonics realign the continents back into Pangaea, if you get my drift. So much for my earth shaking wit. Maybe I should stick to logic or would that be an act of Vulcanism? My mom always told me I was a Spock baby. Don't forget to tip your driver. I'm here all week. I'm not trying to give you any lip mind you but it is topical to the discussion.

The saddle is a pretty unforgiving place to launch. It requires a straight in 8 to 20 mph breeze and the launch run needs to start back far enough to get good momentum going. having seen Ken M's photos of the work done to the main ramp I am optimistic that it will be better for more pilots.

Honesty, there's no telling how the main ramp will work in gusty, switchy or thermic conditions until pilots launch it enough times. I really did like the soap bubbles idea. Higher quality machine are available on ebay for $35.00. These can be run with an inverter and 12V battery. It may be worth a try. After that we can have Polka night at Rob's annual pool party. Uh one, and uh two.....