Forums: Skydiving Disciplines: Swooping and Canopy Control:
Using weights

 


freeflyit  (C 3714)

Feb 1, 2017, 5:50 PM
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Using weights Can't Post

I gots questions...and obviously no coach, lol.

So using weights changes wing loading BUT.... I have a feeling it is not the same as downsizing on the same model...or is it?

Let's be specific, if I have a VC90 and my exit weight is 180lb. AND I have a weight belt with 0-22lb range. Therefore, my loading could be between 2.0-2.24.

If there were no weights and I downsized the canopy only (same model), it would look like this:

VC90 @ 2.0
VC84 @ 2.14
VC79 @ 2.27
VC75 @ 2.4

So the question is...would the weight belt substitute canopy size for progression?

I have a feeling its NO, probably something to do with how big the wing is... drag factor. If you know for sure the scientific answer with the math, let me know!!! Set me straight mofos :D


skow  (D 3911)

Feb 1, 2017, 10:13 PM
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Re: [freeflyit] Using weights [In reply to] Can't Post

Yeah, it's not the same thing. When you downsize you are flying a smaller wing with less material, surface and usually shorter lines - basically it's a bit more twitchy than bigger wing at the same wingloading.

One of the reasons why competition swoopers use weight is that at some point when downsizing the wing is too small and doesn't create that much lift anymore - so even though you have more speed, the wing doesn't carry you that far


(This post was edited by skow on Feb 1, 2017, 10:16 PM)


Royreader8812

Feb 2, 2017, 10:26 AM
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Re: [skow] Using weights [In reply to] Can't Post

Yes and no.

As explained above, a smaller canopy flies different to a bigger canopy of the same wingloading. Twitchy and less forgiving.

That said, a bigger canopy loaded the same as a smaller canopy of the same type will 'easily' fly further in nil or downwind conditions and will provide a better shut down. Smaller wings have an advantage in head winds.

I say easily because Nick Batsh proved the old, 'bigger canopies of the same wingload go further' argument wrong, when he soared 20 metres past everyone on a Petra 57 in light consistent winds in comp. On another jump he came short of everyone else. So the smaller you go, the more precise you must be, to actually get the benefits.

If competition swooping is your aim, then the best thing is to add the weight now to your max allowance. Or work up to that if you are tiny and need more than 8 kg. The OP is allowed over 12kg. 12kg is a lot to add in one go, so splitting it in half and doing a few with 6kg and add 6 more later is probably a good idea. Because you are going to have to do that at some stage anyway and it is easier and better to work all that out earlier.

If swooping further after a freely jump is the aim, then get a smaller canopy. But only when you are actually ready. Not only in a safety sense, but in your ability to squeeze every bit out of your swoop consistently.

Downsizing does make a longer swoop, as does a bigger turn, but skipping the details only limits your progress in the long run.

Going back and doing a season of 90's after already being what I thought was proficient at 270's, was probably the best thing that could have happened to my progression. My 810's are better at the bottom end, because of those 90's. Even though I didn't realise that at the time. Leaning to milk everything out of your turn is key.

You are going to do both anyway, so get the weights out of the way now,If you are in fact ready.

VC75 were seldom used in comp, 79 seems to be the best size of those. After that, newer designs are needed to get more performance. Just an observation.

Be safe and swoop far.


(This post was edited by Royreader8812 on Feb 2, 2017, 10:58 AM)


skow  (D 3911)

Feb 2, 2017, 10:57 PM
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Re: [Royreader8812] Using weights [In reply to] Can't Post

Royreader8812 wrote:
That said, a bigger canopy loaded the same as a smaller canopy of the same type will 'easily' fly further in nil or downwind conditions and will provide a better shut down. Smaller wings have an advantage in head winds.

Can you explain why the difference when flying down- and upwind?


sammielu  (D 33923)

Feb 3, 2017, 1:23 AM
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Re: [skow] Using weights [In reply to] Can't Post

skow wrote:
Royreader8812 wrote:
That said, a bigger canopy loaded the same as a smaller canopy of the same type will 'easily' fly further in nil or downwind conditions and will provide a better shut down. Smaller wings have an advantage in head winds.

Can you explain why the difference when flying down- and upwind?

The bigger canopy has more surface area for the wind to push - so the wind will push farther when going with the wind and the bigger wing will resist the wind more when flying into the wind. This only applies at the same wingloading though.


Royreader8812

Feb 3, 2017, 1:24 AM
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Re: [skow] Using weights [In reply to] Can't Post

Simple,
Big parachute, more parasitic drag.

And vice versa.

Other actions are in play as well and I'm sure others will chime in with a differing position.

Personally I like to do accuracy on a smaller wing with lazier turn. Because it is easy lose speed than gain it. Others like the extra shut down of a bigger canopy and a bigger turn... either way, you have to go 70 metres to win.

There are many quite technical forces and actions at play in canopy piloting. I'm pretty sure nobody understands them all, let alone their correlations enough, to say what the absolute best way to do something is. That is why swoopers can tech talk for hours and come to different conclusions and all be right, or wrong.

This is probably the most attractive thing about the discipline. Who knows what is 'correct'. One might have a better understanding of physics, but another might be more consistent at applying their less technical approach.

At the end of the day the one that goes fastest, farthest or stands up in the box wins.

Like the old saying goes, there is more than one way to skin a cat.


(This post was edited by Royreader8812 on Feb 3, 2017, 1:33 AM)


skow  (D 3911)

Feb 6, 2017, 4:12 AM
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Re: [sammielu] Using weights [In reply to] Can't Post

I remember not long ago there was a long discussion about recovery arc in downwind/upwind situations (http://www.dropzone.com/...;;page=unread#unread) and vast majority of people agreed that wind direction doesn't matter.

So why does it matter now?


hodges  (D 108409)

Feb 6, 2017, 5:55 AM
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Re: [skow] Using weights [In reply to] Can't Post

Wing flies exactly the same but covers more ground downwind and less into wind.

Nothing to do with the wing being pushed more.


chuckakers  (D 10855)

Feb 6, 2017, 6:17 AM
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Re: [sammielu] Using weights [In reply to] Can't Post

sammielu wrote:
The bigger canopy has more surface area for the wind to push - so the wind will push farther when going with the wind and the bigger wing will resist the wind more when flying into the wind. This only applies at the same wingloading though.

I'm no rocket surgeon but that doesn't sound right.


Royreader8812

Feb 6, 2017, 7:47 AM
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Re: [chuckakers] Using weights [In reply to] Can't Post

It has more to do with parasitic drag.

If we are talking about a smaller wing of the same type and wingloading having an advantage in head wind.

The bigger wing would have more potential energy as the pilot would obviously have to be heavier than the person on the smaller wing to.have the same wingloading.

But from my observation the extra parasitic drag of the bigger surfaces seem to negate the benefits of extra potential energy.

Inversely, down wind the parasitic drag is less as the air is moving in the same direction of the canopy, reducing parasitic drag. So the potential energy of the bigger/ heavier pilot become an advantage.

I am sure there are also more forces at work.


(This post was edited by Royreader8812 on Feb 6, 2017, 7:58 AM)


chuckakers  (D 10855)

Feb 6, 2017, 9:29 AM
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Re: [Royreader8812] Using weights [In reply to] Can't Post

Royreader8812 wrote:
It has more to do with parasitic drag.

If we are talking about a smaller wing of the same type and wingloading having an advantage in head wind.

The bigger wing would have more potential energy as the pilot would obviously have to be heavier than the person on the smaller wing to.have the same wingloading.

But from my observation the extra parasitic drag of the bigger surfaces seem to negate the benefits of extra potential energy.

Inversely, down wind the parasitic drag is less as the air is moving in the same direction of the canopy, reducing parasitic drag. So the potential energy of the bigger/ heavier pilot become an advantage.

I am sure there are also more forces at work.


Your theory is flawed. A canopy in flight behaves the same way regardless of its direction relative to the wind. The only thing that changes is the speed and direction relative to the ground.

You said "down wind the parasitic drag is less as the air is moving in the same direction of the canopy". That is incorrect. The forces on the canopy are the same regardless of its direction. The canopy is an object moving within a moving mass of air. The only time the forces change is when the speed or direction of the wind changes, and then only until the change is complete.


Di0  (D 34840)

Feb 6, 2017, 10:27 AM
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Re: [Royreader8812] Using weights [In reply to] Can't Post

Royreader8812 wrote:
It has more to do with parasitic drag.

If we are talking about a smaller wing of the same type and wingloading having an advantage in head wind.

The bigger wing would have more potential energy as the pilot would obviously have to be heavier than the person on the smaller wing to.have the same wingloading.[..]

If you want to keep a discussion on energy levels alone, then there is no need to introduce other concepts like drags etc.
The potential energy of a heavy person is higher, true. But a bigger wing will have lower speeds overall, lower trim speeds, lower dive speeds etc. (also because of drag, true, but not only).
In the energy balance, speed is squared, so reducing the speed by a just a little is intuitively more effective than the small increase in weight you might have with a weightbelt.

The rest of your post is wrong, parasitic drag is a force that depends on relative airspeed, downwind or into the wind does not make much of a difference (except for some second degree effects during transition states, that I remember discussing on another topic).


(This post was edited by Di0 on Feb 6, 2017, 10:29 AM)


Royreader8812

Feb 7, 2017, 8:48 AM
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Re: [Di0] Using weights [In reply to] Can't Post

In reply to:
The rest of your post is wrong, parasitic drag is a force that depends on relative airspeed, downwind or into the wind does not make much of a difference (except for some second degree effects during transition states, that I remember discussing on another topic).

Parasitic drag is a force that depends on surfaces area, down wind or into the wind has the same effect on the surfaces, but certainly not on the ground speed and distance covered.

A bigger wing of the same wingloading as a smaller one of the same type, will have an advantage down wind, and a disadvantage into the wind.

There are other forces involved, I don't claim to understand them nor be able to explain them, but I know it to be true from experience and observation.

How about that.


(This post was edited by Royreader8812 on Feb 7, 2017, 8:59 AM)


Di0  (D 34840)

Feb 7, 2017, 9:53 AM
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Re: [Royreader8812] Using weights [In reply to] Can't Post

Royreader8812 wrote:
In reply to:
The rest of your post is wrong, parasitic drag is a force that depends on relative airspeed, downwind or into the wind does not make much of a difference (except for some second degree effects during transition states, that I remember discussing on another topic).

Parasitic drag is a force that depends on surfaces area, down wind or into the wind has the same effect on the surfaces, but certainly not on the ground speed and distance covered.

A bigger wing of the same wingloading as a smaller one of the same type, will have an advantage down wind, and a disadvantage into the wind.

There are other forces involved, I don't claim to understand them nor be able to explain them, but I know it to be true from experience and observation.

How about that.

Also wrong.
Parasitic drag is a force, you're right.
Its measured amount does not vary whether the canopy is flying downwind or upwind. Stop.
The same canopy flying through the air at the same airspeed will produce the exact same parasitic drag*, which is a function of relative airspeed. You don't get an increase in relative airspeed when going downwind, therefore you also don't get an increase in parasitic drag.

I'm not even sure what the second part of your last sentence means.

As for the "advantage" of smaller canopies into headwinds, what you're really seeing is an effect of vector composition. A smaller canopy has higher vertical and horizontal speed, so a negative speed composed against your forward speed, will affect your glide angle less than if you have a smaller forward speed (i.e. big canopy).
The same but opposite is true if you're downwind: the big canopy will "benefit" more.

Drag has absolutely NOTHING to do with this.


* and the same reasoning eventually applies to induced drag too, but passing through the lift equation.


(This post was edited by Di0 on Feb 7, 2017, 9:56 AM)


skow  (D 3911)

Feb 7, 2017, 11:42 PM
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Re: [Di0] Using weights [In reply to] Can't Post

Di0 wrote:
As for the "advantage" of smaller canopies into headwinds, what you're really seeing is an effect of vector composition. A smaller canopy has higher vertical and horizontal speed, so a negative speed composed against your forward speed, will affect your glide angle less than if you have a smaller forward speed (i.e. big canopy).
The same but opposite is true if you're downwind: the big canopy will "benefit" more.

I guess you're talking about situation that wingloading for those canopies is not the same? And the glide angle in relation to the ground?


freeflyit  (C 3714)

Feb 8, 2017, 3:15 AM
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Re: [Royreader8812] Using weights [In reply to] Can't Post

>>I know it to be true from experience and observation<<

Just curious, what is your experience?


Royreader8812

Feb 8, 2017, 7:49 AM
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Re: [Di0] Using weights [In reply to] Can't Post

Mate you are misunderstanding my words.

You just made a long winded attempt to say that a bigger canopy, Say a comp velo 90 loaded at 2.5... has the same parasitic drag as a comp velo 79.

That is incorrect.

The same canopy will have the same drag whether it is going into or down wind, sure.

But the 75 will have the advantage in head wind due to having less drag.

And the 90 will have the advantage down wind due to having more lift.

Pretty simple.


Di0  (D 34840)

Feb 8, 2017, 8:12 PM
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Re: [Royreader8812] Using weights [In reply to] Can't Post

Simple, but also wrong, because, as I said, the drag formula depends on the surface (true) but also on the square of velocity so you cannot say that a Velo 90 will have a bigger parasitic (or even total) drag than a velo 79.
Maybe.
Maybe not.

What's certainly true that drag is NOT the leading effect as to why a smaller canopy is goes farther into head wind than a bigger one. It might contribute, but it doesn't.

Your argument is a bit like saying that the car with smaller rear view mirrors will go faster because it has less drag. Ok, that's maybe true, but you're totally missing the bigger picture.

Also, since the OP is asking about using weight I'd think it would make more sense and being more helpful to talk about same canopies at different WL, rather than different canopies at same WL, that doesn't interest him as much. But yes, at different WL for the same canopy, the parasitic drag force will also increase (higher speed -> higher drag, bur roughly same efficiency L/D).


(This post was edited by Di0 on Feb 8, 2017, 8:14 PM)


Di0  (D 34840)

Feb 8, 2017, 8:16 PM
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Re: [skow] Using weights [In reply to] Can't Post

skow wrote:
I guess you're talking about situation that wingloading for those canopies is not the same? And the glide angle in relation to the ground?

Yup, right, that was assuming that the smaller canopy was "going faster", I see that might not be necessarily true - since it depends on WL. However in 0 winds, changing WL will not change the glide in relation to the ground too much. It will when considering winds, though, for the reasons I was explaining in the part you quoted. Yes, I think we're saying the same thing basically! :D


Royreader8812

Feb 9, 2017, 7:46 AM
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Re: [Di0] Using weights [In reply to] Can't Post

This hypothetical situation is assuming the same canopy type, the same wingloading, the same turn and the sane velocity through the entry gate.

At that point yes the 79 has less drag than the 90.

Also the 79 is more sensitive to inputs so will be negatively effected by incorrect inputs.

But this hypothetical situation is impossible to simulate in real life as no two.turns by one person are the same, let alone those by two different people.

All you are doing us confusing the matter by overanalyzing something you misunderstood. That is probably due to my wording. But something I have said and you are reiterating,is that there are more forces at work, they all seem to effect each other somehow or another, and this is what makes swooping so interesting.



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