Quake120 0 #1 May 13, 2006 So after my first skydive last week (I have to go again!), I got to thinking about the "drogue" used in tandem. They say it is to slow you and your tandem master down, but that doesn't make any sense to me. Let me explain... (I'm sure you all know the following physics stuff, but I'm just putting it here so you know I at least have an idea of how terminal velocity works, etc) Terminal velocity is caused when the force of the air on a falling object is balanced with the force of gravity, causing something to fall at a constant rate and no longer accelerate. Weight is not a factor in this. If not for wind resistance, a feather and a bowling ball will hit the ground at exactly the same time. The more wind resistance an item has, the slower the terminal velocity. Using the above information I would think that in tandem-freefall, your terminal velocity would be SLOWER than a single person. You've got twice the amount of legs, arms, a head, a much larger parachute, etc that can cause wind resistance. So...is the drogue used for stability, or is there some other reason why you'd fall faster that I am missing? Quote Share this post Link to post Share on other sites
DZJ 0 #2 May 13, 2006 AFAI understand it, for most of a skydive the relative wind is coming vertically from underneath. With the wind coming from that direction, a tandem pair's area presented to the wind is not significantly more than a solo skydiver's (and so their resistance). Given that they have a much greater mass in relation to the wind, their terminal veloctiy is therefore higher. (I daresay this is all wrong and I will be shot down by someone more physics-savvy, but that's how I understand it at the moment) Quote Share this post Link to post Share on other sites
Yossarian 0 #3 May 13, 2006 i think thats basically right, not sure about the maths (i am but a lowly politics student) but its to do with mass and surface area, its why short stocky people fall faster than us lanky tall blokes. Quote Share this post Link to post Share on other sites
slotperfect 7 #4 May 13, 2006 My fall rate with a drogue and an average sized tandem student is about 115-120 MPH. My fall rate without a drogue (same sized passenger) is about 180 MPH. All of the surface area is concentrated in one place - one big lump of flesh hurtling toward the ground together. Arrive Safely John Quote Share this post Link to post Share on other sites
jakee 1,497 #5 May 13, 2006 QuoteTerminal velocity is caused when the force of the air on a falling object is balanced with the force of gravity, causing something to fall at a constant rate and no longer accelerate. Weight is not a factor in this. If not for wind resistance, a feather and a bowling ball will hit the ground at exactly the same time. Yes it is!! Gravity isn't the force, weight is (Mass X Gravity). Terminal velocity is reached when drag (upwards) equals weight (downwards). Consider this - a big fuzzy bowling ball (if there is such a thing) will have much higher drag coefficient than a small feather, yet will still fall much faster. In a tandem skydive you have twice the weight of an average person but only a slightly larger area exposed to the wind. To stop you from exceeding the max deployment speeds of the parachute system the drogue is needed.Do you want to have an ideagasm? Quote Share this post Link to post Share on other sites
Yossarian 0 #6 May 13, 2006 and so the camera man can keep up... Quote Share this post Link to post Share on other sites
Quake120 0 #7 May 13, 2006 I think you should probably be a science teacher of some kind... I was trying to find an argument(not that this was an argument, but rather a question about terminal velocity, etc) for the bowling ball thing, but I can't. After reading a bit online, I think you have answered my question! But...the only reason the weight affects something on earth is due to air. If you have a tandem pair, you have twice the weight, same quantity of air. On the moon you could drop a feather, and a 150,000 pound ball and they'd both hit at exactly the same time. Gravity affects everything equally. Quote Share this post Link to post Share on other sites
sundevil777 102 #8 May 13, 2006 QuoteWeight is not a factor in this. Yes it is. The weight of the object falling is the force that is balanced with drag when terminal velocity is reached. Gravity is not a force, it is an acceleration. When the acceleration of gravity is multiplied by the mass of an object, you then have the weight of the object due to gravity.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
Quake120 0 #9 May 13, 2006 QuoteQuoteWeight is not a factor in this. Yes it is. The weight of the object falling is the force that is balanced with drag when terminal velocity is reached. Gravity is not a force, it is an acceleration. When the acceleration of gravity is multiplied by the mass of an object, you then have the weight of the object due to gravity. Gravity IS a force, actually. It isin't an "acceleration", that makes no sense... The question presented in this thread was answered, though. Just took another point of view to make me understand it. Quote Share this post Link to post Share on other sites
jakee 1,497 #10 May 13, 2006 Quote I think you should probably be a science teacher of some kind Kids scare the crap out of me QuoteOn the moon you could drop a feather, and a 150,000 pound ball and they'd both hit at exactly the same time. Gravity affects everything equally. Yes, in a vacuum things will continue to accelerate at the same rate, they will also never reach terminal velocity. Gravity is expressed by acceleration, on earth it's around 9.81m/s/s. F=MA, W=Mg. Basically when the mass is greater the force is greater, but since more force is required to accelerate the greater mass acceleration due to gravity remains constant. Terminal velocity though is all about weight, air resistance and the balancing of forces.Do you want to have an ideagasm? Quote Share this post Link to post Share on other sites
sundevil777 102 #11 May 13, 2006 QuoteQuoteQuoteWeight is not a factor in this. Yes it is. The weight of the object falling is the force that is balanced with drag when terminal velocity is reached. Gravity is not a force, it is an acceleration. When the acceleration of gravity is multiplied by the mass of an object, you then have the weight of the object due to gravity. Gravity IS a force, actually. It isin't an "acceleration", that makes no sense... A common definition of gravity is: The force exerted by all objects having mass on all other objects having mass. So, yes, I was wrong to say it is not a force. However, the units of gravity are distance/time squared (same units as acceleration) when used to calculate the weight of something by the formula: weight = mass x gravity. If asked how much gravity is there on the surface of the earth, I would answer by saying what the acceleration due to gravity is. If asked what the force of gravity is on a particular object, that answer is actually the weight of the object and the answer will have the units of force only.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
MB38 0 #12 May 13, 2006 Here are two pictures from Google showing the surface area of a tandem pair from underneath. If anything they have 10-15% more surface area... but twice the mass.I really don't know what I'm talking about. Quote Share this post Link to post Share on other sites
matt1215 0 #13 May 13, 2006 That's it!! I've been trying to figure out how to take my cat skydiving. Rig her up to a tandem-drogue . Quote Share this post Link to post Share on other sites
lowpole 1 #14 May 14, 2006 I agree, in a vacume the equation is true but, in real life drogeless free fall is about a buck 80Darwin's Watching! Quote Share this post Link to post Share on other sites
teason 0 #15 May 14, 2006 I did a test jump a few months ago with a data-logger. We exited at 13500 and went drogueless until 10000. Goggles buffeting all the way. The Data logger read a max speed of 173 mph with our exit wieght of 450lbs. If memory serves, our speed in drogue fall was about 120 or so, I can't quite remember. They were using all sorts of math to calculate the amount of force exerting by the drogue (2gs or so on drogue deployment) and my eyes must have glazed over!I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet. Quote Share this post Link to post Share on other sites
jakee 1,497 #16 May 14, 2006 Quote I agree, in a vacume the equation is true but, in real life drogeless free fall is about a buck 80 Oddly enough I've seen drogueless 'atmonauti' tandems with Marco Tiezzi that stayed under 120mph the whole way. Pretty impressive.Do you want to have an ideagasm? Quote Share this post Link to post Share on other sites
JohnMitchell 16 #17 May 14, 2006 Quote[ Consider this - a big fuzzy bowling ball (if there is such a thing) will have much higher drag coefficient than a small feather, yet will still fall much faster. Nope, your math is fuzzy. The bowling ball will have more total drag than the feather, but a lower coefficient, or multiplying factor, than the feather. Kind of like the difference between heat energy and temperature. Quote Share this post Link to post Share on other sites mjosparky 4 #18 May 14, 2006 QuoteQuote I agree, in a vacume the equation is true but, in real life drogeless free fall is about a buck 80 Oddly enough I've seen drogueless 'atmonauti' tandems with Marco Tiezzi that stayed under 120mph the whole way. Pretty impressive. Maybe Professor Kallend will jump in here, but I call “bull shit”. I don’t think the laws of physics would allow this.My idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites Yossarian 0 #19 May 14, 2006 laws of physics dont allow bumblebees to fly, all they have to do is ignore them and theyre fine, maybe those atmonauti guys ignore them aswell... Quote Share this post Link to post Share on other sites bob.dino 1 #20 May 15, 2006 QuoteThat's it!! I've been trying to figure out how to take my cat skydiving. Rig her up to a tandem-drogue . Do a Search. Like most everything else, it's been discussed here before . Quote Share this post Link to post Share on other sites mjosparky 4 #21 May 15, 2006 Quotelaws of physics dont allow bumblebees to fly, all they have to do is ignore them and theyre fine, maybe those atmonauti guys ignore them aswell... Right! And if a frog had wings he wouldn't bump his ass. "You keep on thinking Butch, thats what you are good at".My idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites karlm 0 #22 May 15, 2006 My DZ is 5000ft above sea level, so on an avergae day like this wekend, the speed on my tnadems is in the region of 130mph (TAS on my Protrack). To answer the question, yes a TM uses the drougue as a speed reduction device, to lessen opening shock on the main. It is also used as a stability device, so once the pair have exited and are stable (within 12 sec) the drougue is set, and the pair fall in drogue fall. And as it is a basic "pilot-chute-in-tow" the drouge is also used to activate the main deployment. Better never to have met you in my dream than to wake and reach for hands that are not there. Quote Share this post Link to post Share on other sites Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. Paste as plain text instead Only 75 emoji are allowed. × Your link has been automatically embedded. Display as a link instead × Your previous content has been restored. Clear editor × You cannot paste images directly. Upload or insert images from URL. Insert image from URL × Desktop Tablet Phone Submit Reply 0
mjosparky 4 #18 May 14, 2006 QuoteQuote I agree, in a vacume the equation is true but, in real life drogeless free fall is about a buck 80 Oddly enough I've seen drogueless 'atmonauti' tandems with Marco Tiezzi that stayed under 120mph the whole way. Pretty impressive. Maybe Professor Kallend will jump in here, but I call “bull shit”. I don’t think the laws of physics would allow this.My idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
Yossarian 0 #19 May 14, 2006 laws of physics dont allow bumblebees to fly, all they have to do is ignore them and theyre fine, maybe those atmonauti guys ignore them aswell... Quote Share this post Link to post Share on other sites
bob.dino 1 #20 May 15, 2006 QuoteThat's it!! I've been trying to figure out how to take my cat skydiving. Rig her up to a tandem-drogue . Do a Search. Like most everything else, it's been discussed here before . Quote Share this post Link to post Share on other sites
mjosparky 4 #21 May 15, 2006 Quotelaws of physics dont allow bumblebees to fly, all they have to do is ignore them and theyre fine, maybe those atmonauti guys ignore them aswell... Right! And if a frog had wings he wouldn't bump his ass. "You keep on thinking Butch, thats what you are good at".My idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
karlm 0 #22 May 15, 2006 My DZ is 5000ft above sea level, so on an avergae day like this wekend, the speed on my tnadems is in the region of 130mph (TAS on my Protrack). To answer the question, yes a TM uses the drougue as a speed reduction device, to lessen opening shock on the main. It is also used as a stability device, so once the pair have exited and are stable (within 12 sec) the drougue is set, and the pair fall in drogue fall. And as it is a basic "pilot-chute-in-tow" the drouge is also used to activate the main deployment. Better never to have met you in my dream than to wake and reach for hands that are not there. Quote Share this post Link to post Share on other sites
