Mar 1, 2004, 9:53 AM
Post #1 of 16
TM Poll: Rear riser turns
Question: Can you as the TM turn the canopy/tandem pair with the rear risers while the brakes are still set (assuming its not an Icuras w/o brake settings)? --(Explaination below)--
This is something that was brought up in a TM cert course I sat through this past week, rear risering tandems and the strength it requires.
Basically, I tend to use my rear-risers quite a bit during opening and after opening to point me where I want to be before I pop the toggles and start adjusting the student. This has become very handy when there are multipul tandems on one load.
I was discussing this with the canidates and Course Director during a break, where as the CD told me that the majority of TMs can't even do this, which really truely surprised me. That is also what prompted me to come up with the "TM workout" I posted in the General Forum.
As a side note, what do you think is the "average" pull force on the rear-risers.
Obviously that would change with suspended weight and canopy, but with my "average" student on a Sigma 370 or even the EZ-384 I'm guessing it to be about 50lbs of pull with the brakes set and about 20lbs of pull with the brakes released. That's just my guess, though.
Also, here is the link to the workout I came up with for TMs, after the conversation I had with the Course Director: Workout
Isn't "pull force" on risers simply one way of saying how much of your weight should you suspend from that riser? For example, if you weigh 150 lbs and are doing a solo under your own canopy, you can't put more than a constant 150 lb force on the rear risers. And you don't even have to be strong to do this - just strong enough to suspend your own weight from your hands (i.e. hang from a pullup bar), so that all your weight is transfered from the harness (equally distributed toward all risers) to the riser(s) you wish to displace.
I could be wrong since I haven't observed exactly what's happening when I do rear riser turns on my canopy, nor have I ever done a tandem, but I know that when newbies have a hard time pulling on their front risers, they're often told to try to pull themselves up rather than the risers down. This was always common sense to me.
Anyway, I guess I'm curious how one tandem master couldn't do a rear riser turn when another could, since it's more a matter of weight than strength. The obvious answer (to me, could be wrong) is the ones who can't aren't heavy enough...
I think you probably already took this all into account in your original post, so just ignore me, I'm just thinking out loud. No clue about tandem specifics...
My understanding is that its a combination of suspended weight as well as the design of the canopy and the size of the canopy, some canopies have heavier front riser pressure, then rear riser pressure, etc. Thus students aren't necissarily "too light" they don't have the strength to pull the canopy.
I could very well be wrong in that explaination, though, it would be nice for someone that has the "real" answer to explain that...*hint, hint*
Remember, with a tandem, its not 150lbs, its anywhere up to 500lbs of suspended weight.
I can't do rear riser turns on tandems and I'll admit that to anyone. I just don't have the arm strength to do them. I perfer to have the students help me on landings so I can have enough power left to do more then 2 or 3 jumps too.
Being 6'2", 170 pounds puts my build at somewhere between toothpick and telephone pole.
Yeh, I was just using 150lb as an arbitrary number.
And I was going to say, that I still believe it has to do with weight, but I just changed my own mind. Think about this - in order to pull down on something that required force (a greater force than your body weight), you need a force that restrains you from lifting up. You know, like those pullup machines in the gym that you sit down for. You have to hook your knees under a bar if the weight you want to lift is heavier than you. Otherwise you won't be able to move it, no matter how strong you are. In a solo canopy ride there is nothing holding you down, so as long as the force required is less than your weight and you can do a pullup, you can move the riser. But under a tandem canopy, you DO have a force pulling down on you (the student). I guess that was the bad part of my analogy. So if you and the student are each 150lbs, and there is a 200lb force required to pull down the risers (not trying to be realistic here, just making a point), you'd have to be strong enough to do a pullup with 50 lbs on your back in order to move the risers.
I'm really not doing a good job of answering your actual question, what the magnitude of the force is. Just pointing out that if the combined weight of you and your student is say 300lbs, it is physically impossible to pull down on the risers any harder than that, no matter how strong you are.
I can do rear riser turns and flares - with SET 400 canopies - depending upon the weight of the student. With petite Japanese girls on the front I can easily control the canopy with just rear risers, and could probably flare enough to survive the landing. With light-weight students, it feels like doing chin-ups with a bit more than my normal weight. All that changes with a 230 pound student on the front. Then it takes every ounce of strength to pull a riser 2 inches. Then it feels like doing chin-ups at twice my normal weight.
I'm not sure about tandem canopies, but I know that as a student, I couldn't do front riser turns on the 260. I was lifting myself up in the harness, but having no effect whatsoever on the canopy. I was basically doing a one-handed pull-up, but my full body weight wasn't enough to make it turn. Rear riser turns weren't as much a problem, though.
I use them all the time after opening, and I'd use them to land if I had to, but they do take some strength. Once when I had about 190 lbs. of puking whuffo up front, I grabbed front & rears and twisted us about 90 degrees. It took every bit of strength I had, but somehow the streaming vomit inspired me to reach down and find it in myself.
I've tried to use fronts to penetrate winds, as well. Stiffest riser pressure I've ever felt, and it didn't seem to help much with lighter cargo.
I'm gonna go with "never thought to try it." Traffic's usually pretty light at tandem altitudes, and the toggles are prety handy if you need a quick turn. I've tried to front riser some but there's a hell of a lot of pressure. I'll give the rear risera a try on my next tandem. As for the broken brake line, I'm chopping.
I have landed a few first-generation tandem mains with broken lines. The time I landed with one broken upper steering line was barely noticeable, similar to a broken D-line. However, the one time I landed a tandem with a broken A-line, it was not pretty or pleasant! And the time I broke a lower steering line, I took one look at it and started peeling the cutaway handle!