Do the smaller BASE canopies have more consistent on heading openings than the larger ones?

[DaveO 0]

Ok, I usually bug the piss out of Tom about this but I thought I'd put it out there to get some peoples thoughts.
I jump a 285 and a 293. The guy I jump with most of the time jumps a 205 and a 220. Other than the fact he opens higher and his canopy pressurizes faster than mine he for sure has better on heading preformance than I do. Mine is not bad but there is always room for improvement.

Sorry, I forgot to say for 1 second delays and less. More so on go and throws. Anything after say 1.5 second delay and my on heading preformance goes up.

"When it comes to BASE, I'll never give advice, only my opinion"

[nicknitro71 0]

Are the canopies the same model?

Are the containers the same model?

Is the same person packing both?

Is the PC the same?

Body position...

There are just so many variables.

Memento Audere Semper

903

[460 0]

I've always thought there was a correlation between opening speed and on-heading accuracy. The correlation being, the faster the opening the more on heading the canopy opens, limited of course by the shoulder levelness of the jumper. There is some limited data by Tim Harris of a frame by frame analysis of bridge day jumps that clearly demonstrate this phenomenon, and interestingly, highly independent of all other variables.

Smaller canopies - less fill volume - quicker opening.
Larger canopies - large fill volume - slower opening.

Therefore, if the logic holds, smaller canopies should open more on heading than larger canopies.

But this only my 2 cents.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[DaveO 0]

I'm kind of talking in general. Saying all factors are the same. Nothing specific.

"When it comes to BASE, I'll never give advice, only my opinion"

[nicknitro71 0]

I know a bigger canopy needs more air to inflate. What I don't know is if that correlates with heading.

From skydiving we know that heading and size of the canopy does not correlate: you got a model that opens right on in one size and not so good in another either bigger or smaller.

In BASE I just don't know.

Memento Audere Semper

903

[DaveO 0]

Alright, Who says my packing sucks?! You will be taken off my Christmas card list.

"When it comes to BASE, I'll never give advice, only my opinion"

[TomAiello 25]

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Smaller canopies - less fill volume - quicker opening.
Larger canopies - large fill volume - slower opening.

Therefore, if the logic holds, smaller canopies should open more on heading than larger canopies.

I agree.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[Faber 0]

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Alright, Who says my packing sucks?! You will be taken off my Christmas card list.

i did i wasnt on any way

Stay safe
Stefan Faber

[321Cya 0]

What about wingload? (just noticed that nobody has mentioned it so far...)

Having worked for one of the major canopy manufacturers and looking at what kind of openings people experience on the same model of canopy (but different wingload), I've noticed that this can strongly vary due to difference in wingloading.

Next to that I think that body position, correct pilot chute size for the type of delay and a reasonable packjob have more influence on the heading performance than size of the canopy.

my 2 cents...

J.

www.vandrunen.ch

[RayLosli 11]

I totally agree with that.... Dave
....................

Do the smaller BASE canopies have more consistent on heading openings than the larger ones?

Answer - No

[TomAiello 25]

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What about wingload?

Wingloading also matters, in my opinion.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[leroydb 0]

so back to a question I had in the past...

What are the specialized situtations where a smaller canopy will open faster since you would be W/L it more?

I guess I will also like to throw in a certain 134' cliff jump into water near me

Leroy


..I knew I was an unwanted baby when I saw my bath toys were a toaster and a radio...

[3ringheathen 0]

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What are the specialized situtations where a smaller canopy will open faster since you would be W/L it more?

I can't imagine a scenario where it'd be a factor worth considering.
You are assuming that a smaller canopy does inflate faster, which I'm not convinced is true. I asked DW about it once, he said it was a common misconception.
Further, if the jump was low enough for that to be a consideration, you probably should re-think jumping it.
Food for thought: a 260 that's say 85% inflated has more surface area to produce drag than does a 220 fully inflated. If the jump is so low that you wont have time to fly and flare, drag is all that's gonna matter, right?
-Josh

If you have time to panic, you have time to do something more productive. -Me*
*Ron has accused me of plagiarizing this quote. He attributes it to Douglas Adams.

[leroydb 0]

Good Point made

Leroy


..I knew I was an unwanted baby when I saw my bath toys were a toaster and a radio...

[Skinflicka 0]

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What about wingload?

Wingloading also matters, in my opinion.

Opinion or fact? You may be right but wingloading as a parameter hides a multitude of sins. It is calculated simply in terms of area, mass and acceleration but it's effect on canopy performance is non-linear so as an engineering coefficient it has about as much use as a chocolate condom. It gives you a flava but it provides no protection (I believe that's original. Royalties required for use.)

Also, the speed of inflation is dependant upon size (unsure if this is area or volume related for the purposes of this discussion - I guess it depends on whther you are considering bottom skin inflation or full pressurization) and rate of inflation. The rate of inflation of the bottom $kin will be proportional to airspeed raised to a power that I can't be bothered to consider right now. The pressurization rate is proportional to relative forward speed (again raised to a power - probably squared but don't quote me today. I can't be arsed to think about it), size of vents and tons of other stuff that I can't be bothered to think about.

Bottom line without thinking too hard...off heading openings due to differential inflation rates are initiated by events / conditions rather than properties so to say that a larger canopy is inherently more prone to off headings is only valid in the context of empirical data from a high level rather than from theoretical analysis (if indeed you have this data and you trust it's validity). I'd contend that fat jumpers with big canopies are just more fucking clumsy.

I'm on vacation for a coupla weeks now so I may do some analysis and try to figure this out. On the other hand I may just smoke some PCP and gnaw my own fucking leg off. Both sound pretty good.

Trust this bores the living shit out of you.

Festive cheer to one and all...

$kin.

Prizes to anyone who gets to read my posts before Mr Aiello's son, Tom deletes them.

[TomAiello 25]

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What about wingload?

Wingloading also matters, in my opinion.

Opinion or fact?

See above.

Seriously, I think the major wingloading differences only start to show themselves at very low wingloadings (say, .5 and under), and are much less important than a multitude of other factors.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[Skinflicka 0]

I think you're right, Tom (can't vouch for the 0.5 figure) but the relevant factor is related to the ability of the falling body to overcome wind resistance and thereby induce an effective relative airspeed. What the split is, I don't pretend to know. I have a gut feel (like most folks) and since this is based on empirical observation I tend to think it's fairly accurate. I wouldn't use it to predict performance where what happens in the next 30 feet matters since, as you so rightly say, other factors may have the greater contribution. Bottom line...your mileage by analysis may vary resulting in severe death and horrible dismemberment or glory and stardom. Think about that on your next sub200 footer.

My fucking leg is killing me. What's up with that?

$kin.

Prizes to anyone who gets to read my posts before Mr Aiello's son, Tom deletes them.

[base515 0]

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. On the other hand I may just smoke some PCP and gnaw my own fucking leg off. Both sound pretty good/

What? You have PCP and you ain't sharing?? You deserve to have your leg gnawed off, by rabid homosexual baboons

May we live long and die out

[Skinflicka 0]

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. On the other hand I may just smoke some PCP and gnaw my own fucking leg off. Both sound pretty good/

What? You have PCP and you ain't sharing?? You deserve to have your leg gnawed off, by rabid homosexual baboons

Too late...still have the left one...baboons had to split...address under separate cover...feeling weak...

$kin.

Prizes to anyone who gets to read my posts before Mr Aiello's son, Tom deletes them.

[blitzkrieg 0]

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I'd contend that fat jumpers with big canopies are just more fucking clumsy.

dude, you crack my $hit up!!!

while that's probably completely true... i'd be willing to bet invisible and/or unforseen wind currents are going to give you many more off heading openings than simple adjustments to WL's... and even the most perfect pack job won't prevent that. just ask the guy who went thru the window.

~E

[Skinflicka 0]

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while that's probably completely true... i'd be willing to bet invisible and/or unforseen wind currents are going to give you many more off heading openings than simple adjustments to WL's... and even the most perfect pack job won't prevent that. just ask the guy who went thru the window.

~E

I'll bet you're right, young fella m'lad...begs the question "how many 180s are voluntary"?

What exactly does a visible wind current involve?

$kin.

Prizes to anyone who gets to read my posts before Mr Aiello's son, Tom deletes them.

[blitzkrieg 0]

of course i meant "invisible" as the wind you can't see with chalk or toilet paper your letting go at the exit point.

ha, and i'm an idiot, so don't take anything i say too seriously...

~E

[leroydb 0]

someone beat me to a smart ass comment? speechless...

Leroy


..I knew I was an unwanted baby when I saw my bath toys were a toaster and a radio...

[whatever 0]

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Opinion or fact? You may be right but wingloading as a parameter hides a multitude of sins. It is calculated simply in terms of area, mass and acceleration but it's effect on canopy performance is non-linear so as an engineering coefficient it has about as much use as a chocolate condom. It gives you a flava but it provides no protection (I believe that's original. Royalties required for use.)

Also, the speed of inflation is dependant upon size (unsure if this is area or volume related for the purposes of this discussion - I guess it depends on whther you are considering bottom skin inflation or full pressurization) and rate of inflation.

OK, let me see if I have this straight:

the hypothesis is (supported by some observations apparently) that smaller canopies inflate quicker.

this makes total sense from a purely applied mathematics point of view, since:

-surface area is a 2nd order function of linear size

-volume is 3rd order function of linear size

SO,

the bigger the canopy, the smaller the surface area to volume ratio, and since all the canopies' volume has to be filled through the surface areas of it's openings, it's easy to see why a smaller canopy, assuming an exactly scaled down version of the larger design, will inflate quicker

cheers
sam

soon to be gone

[Skinflicka 0]

Quote

Quote

Opinion or fact? You may be right but wingloading as a parameter hides a multitude of sins. It is calculated simply in terms of area, mass and acceleration but it's effect on canopy performance is non-linear so as an engineering coefficient it has about as much use as a chocolate condom. It gives you a flava but it provides no protection (I believe that's original. Royalties required for use.)

Also, the speed of inflation is dependant upon size (unsure if this is area or volume related for the purposes of this discussion - I guess it depends on whther you are considering bottom skin inflation or full pressurization) and rate of inflation.

OK, let me see if I have this straight:

the hypothesis is (supported by some observations apparently) that smaller canopies inflate quicker.

this makes total sense from a purely applied mathematics point of view, since:

-surface area is a 2nd order function of linear size

-volume is 3rd order function of linear size

SO,

the bigger the canopy, the smaller the surface area to volume ratio, and since all the canopies' volume has to be filled through the surface areas of it's openings, it's easy to see why a smaller canopy, assuming an exactly scaled down version of the larger design, will inflate quicker

cheers
sam

The inflation rates will not necessarily be the same. Both canopies are subject to some constants which are independant of the canopy size (pilot weight, accn due to gravity, air properties). You said you were assuming an "exactly scaled down version". Does this not imply that due to it's larger openings that the larger canopy could accept air at an increased rate and therefore pressurize in the same time as a small one?

I doubt that the models give you identical geometry either. Why would a 220 stay the same shape in flight as a 280 with the same pilot? He gained no weight for the big canopy. Why should he dangle the same? This lends itself to Tom's wingloading discussion.
The hypthesis as stated is not supported by the observed data. It has failed to be rejected as a result of the obervations. That's a very important distinction.
This is way too heavy for this early in the morning with this big of a hangover.
Maybe I'll dabble in the numbers now that I can no longer walk.

$kin.

Prizes to anyone who gets to read my posts before Mr Aiello's son, Tom deletes them.