[Suneagle]

Thanks for the thought Ian. I guess a better way for me to imagine it is to go the extreme in a more real way. Rather than 100 feet below, what if the glider was remote control and the weight shift was a weight inside the wing that moves forward or backward along the keel.

What is the air doing to make a glider tumble? (Plenty of other posts on this subject here and elsewhere that I've seen).

So... a big model, don't worry about roll, imagine setting up a big wind tunnel that can produce wind shear sufficient to pitch a glider over to a tumble, then test it.

I'd love to see someone in the know do some graphics showing force vectors on a HG wing in flight with variations for the pitching moment based on the distance of the pilot from the hang point.

Perhaps there is NO difference?? Normally I can figure these things out logically but this query of mine is genuine and the answer still evades me. A poll is just a bunch of equally ignorant people taking a guess.

I'd like to hear from any pilot who has a great knowledge of theory who can prove mathematically or diagrammatically what the real answer is.

IT'S A CHALLENGE TO ALL THE EXPERTS ON THIS FORUM...

Does hanging lower make the glider less prone to tumble, more prone, or no difference?

[ian9toes]

How about thinking of it this way, which is perfect for you being bi-wingal. In a paraglider the pilot is susspended way lower than in a hang glider. What are more known for tumbles paragliders or hang gliders?

[Suneagle]

Ian, I think you are comparing apples with oranges.
Paragliders have a frontal collapses.
Hang gliders go 'over the falls'.
Although similar air may cause both, there is little else to compare.

[bobknop]

Hi Jerry,
The proof is in eating the pudding.
Four weeks ago i crashed my supine ( legs under bar) perfex while step towing.
Remember i made a remark on your spreaderbar?Read on.
I am preparing an article in our Deltamagazine,but think what happed gives a idea on tumbles,
and supine safety in general.
As you know i fly this way; http://youtu.be/-PANAxzQdkY
I was flying back away from the cable,and making a turn towards the cable at 119 meters AGL.
After the turn the cable pushed against my left cable and then my wheel.
I went into a left bank and nosed way up.When flying planes they taught me to ;Freeze the problem,
and fly the plain…I never had a chance to pull my reserve,which is on my back,to be grabbed with
left or right hand,but since the unusual attitude i quickly released the cable and did not want to loose
hold of the BB, scared to get disoriented.
We have week links they work fine if you have the right grade and enough speed, while flying away
from the winch.In my opinion a week link does not protect against lockout.
I do not know if the tips where still flying,but i instinctly pulled all the way in;,which is easy because
your legs are like a counter weight in front of you. I think protection against a tumble is simply: copy
a dart ,or :make sure all your weight is far forward and stay there! even when past vertical.(Relative wind)
I then tried to get a level attitude after doing that.
The glider will let you know when it is most efficient to pull out of the dive,by pressure.
Remember ,close to terrain,when your speed doubles,the space required is four times as much.
So, when doing 25 kmpu and you need , say 15 meters,you need 60 meters when doing 50kmpu.
To pull up. Young pilots cut off chimneys of girlfriends houses that way…..
My wing might break when over 60kmpu when diving,in turbulance.Below that speed
it should stall first ,a wing can stall at any speed.
I crashed in a two metre high cornfield,not a bad place.The wing was totalled five failures in the
mainframe and all battens crushe ,many holes in the sail .The sail was ripped from nose to tail.
Also the hook connecting the crossbar to the keel was straightened out.The wing took it all.
I cant prove if crashing supine is safer,all i can prove is the height i was at when it started,i
have no film of the crash,unfortunately.
The spreaderbar is made of the same stuff as a bottembar ( you have one ) and broke in two when crashing.
It must have absorbed lots of energy,no marks or dirt on it.I think it should at least hold to 4.5 G force.
I did not have one scratch or bruise! All i had was a sore spot on my ribcage,where the radio is situated.
The next few days i was very stiff,i must say.High energy traumas can harm you badly from a height of
2-3 times body length.You can break your neck flying prone,or break your vertebrae flying supine.
Yes,i ride a flevobike racer recumbent bicyckle, legs up front too, ,lots of wind in Holland.
So no signific proof,fair dinkum mate!Lost all my aussy slang,used to work in Hallscreek,great sandy dessert.
Coincidece,should get my funfex next week,ordered it tweo months ago.
Why get a slick wing?,All you get is a litle more penatration,we fly slow,remember if you are draggy,increasing speed makes drag quadruple (Disregard all spelling mistakes,highschool only)

http://youtu.be/-PANAxzQdkY
http://youtu.be/Ktpg0dkV44Q

Regards (sitting) Bob Knop.

[Suneagle]

Thanks for the accident report Bob.
Very glad to hear that you are ok. Sorry to hear that you wrote your glider off.

I've a few questions:
1/ Did you have a big stall when you released? Then dive and recover only you hit the ground before your wing would pull up?
2/ Your wing is single surface? Not easy to tumble.
3/ How did you impact? Nose, base bar, legs?

In regards to flying slow and lots of drag in supine at speed I'd have to agree, especially on a single surface wing.

On the other hand, with my harness and flying a Rev I can comfortably reach 90 kph which is the limit set by the bar reaching harness when I pull in fully. My glide is still good and I don't thinking I'm sacrificing much overall performance.

Paragliders could fly rings around my Malibu on an XC, but the Rev leaves them for dead, as it should.

[AIRTHUG]

[bobknop]

Hi Jerry,
It went so fast,i have to relay on people on the ground to tell if i really stalled,but i did go vertical. No tumble
My basebar hit the crops, not enough space,otherwise i would have been able to put it down in a more gracious way.
Its a finsterwalder perfex SS ,supine config off factory,15.9 m2
For reflex it relies on lufflines or reflex bridles,very safe,and i think that saved my life.
I can not determine exactly where my body first contacted the ground,but i had a sore rib,and nothing else
Cant remember that my feet touched the ground first. I regret not having any video on this.
Regards Bob

[bobknop]

[KrunoDr]

Yes I saw that harness, I thought you got it at Charly-F.
When I looked at the website I could not find it, and when I order a spreader bar from them I got advice to get a paraglider harness because beginer one they have listed is not comfy after prolong flights.


I think it would be great for dunes.Ill try to find it.
How comftorable is it after longer flights?

[bobknop]

[Suneagle]

Thanks Ryan. Logically makes sense. The factors that I'm interested in might be outside the parameters of theory. To be specific:
1/ Is a tumble most on the cards when we "go over the falls?"
2/ If so, then going over the falls is when we go momentarily weightless. So either our weightlessness (slack hang strap) has no effect or the complete opposite, the slack hang strap leaves the glider to it's own devices and hence the tumble.
3/ Ryan, you do loops, so you know the importance of keeping positive G's on the wing (hang strap) all the way through. Could it be that the lack of hang strap pressure on a nose down glider will contribute to the tumble?
4/ Or it is simply all about momentum, the glider pitching about the pilot which in turn requires the pilot to be exerting a force through the hang strap?

I hope that my questions are illuminating the point I'm curious about. Tumbling and what causes it? What prevents it? We know that washout/sprog settings are vital... (I'd guess 9/10) so, how important (from 1 to 10) is our height below the wing in preventing it?

One final question (I'm sure many pilots are interested in tumble prevention, so I'll risk being a nuisance). A glider is much less likely to tumble if it is banked up. Right? If a thermal is strong and rough I personally prefer to be cranked over to work it. Am I doing the right thing here? Ooops that was 2 questions

Thanks to Ryan and everyone else in advance for taking the time to answer. I'm here to learn (and stay safe).

......................

Bob, sounds like you almost pulled up in time. Perhaps the very same 2m crop field that cushioned your impact was also the cause of your impact? If I had to crash, I think a lush crop would be choice number one!

I noticed in your towing video that the tow strap hit your wheel as you turned to do each step, so it seems to be a predicable event. How was it different this time to cause you to release? I still think step towing is very risky and you need a very good controller on the winch, not to mention good piloting skills to make it work. Perhaps you can convince your club to invest in a Dragonfly and aerotow instead?

[ian9toes]

[dave hopkins]

[AIRTHUG]

[seabird]

Hi Jerry, as a 4000hr PG pilot that now hang glides I am very interested in your harness solution. Did you choose to hang lower because of greater control or just to be able to have your cross bar in front of you instead of below you? Would it not be simpler to just hang above the bar and use the down tubes for control? Are there any disadvantages to this position? I would like to try a PG harness but I would prefer to hang in a position that the glider designer had expected me to be in.
Regards

[Suneagle]

Just back from another great fly today.

Ryan, thank you very much. Your answers make sense and are food for thought.
Now I'm thinking about going above my bar and seeing how that works.
Might try it first in my Malibu and if I'm feeling confident try in the Rev.

I've been told (by those who have tried) that flying a HG above the bar in suprone is very frightening in rough air.
I've been told that roll input is slow to respond, so turbulence is f**king awful.

I'm not sure that getting the boot of a PG race harness over the bar will be simple either, but I suspect it is doable.

The plus side would be hanging higher so landings would be easier.
Perhaps the other plus is less prone to tumble and the full use of the bar so that the glider can be flown to top speed.

I know the (powered) doodlebug is above the bar, helped in part by the extra weight. Since I fly my wings at the top of the weight range I might be able to fly above the bar too.

Alternatively I could use my 'old' system to raise and lower myself in-flight; to pick which one is most suitable... definitely not KISS.

The trick is to test things out without killing yourself along the way.

Big thanks to everyone for contributing to this thread, especially Ryan.

[ian9toes]

[bobknop]

[AIRTHUG]

[danmoser]