Basejumper.com - archive

Just wondering if anyone who owns a (Fox xs) or (OSP), (because they both incorporate 5 vents and shorter line sets) Have actually physically or visually noticed a difference in either opening alt. or earlier controllability of the wing?

I understand both concepts of adding the (5th C. cell vent addition) and (shortening the line sets) to make the wing better for jumping the Basement, and I like the idea of both of these additions very much. But has it been proven that these additions to a standard 4 vented canopy would make it perform better.

Considering all of the elements of the jump are the same except for the canopies, can you successfully jump an OSP off something that you could not successfully jump a TrollMDV?

Anyone pounding in on an object with there FOX/4vtec that their tip-toeing in with the FOXxs?

I have an OSP 265 and BJ260CUS and another guy in the crew has a Troll dw 245 and OSP 245. I am about 180 lbs and he is about 175. We both have our DBS tuned well. On one of our shorter walls that we do handheld go 'n throws (both with unvented zp 46" PCs) we open at almost the same exact altitude every time. Granted, I do have a few more square feet of canopy on my OSP but my BJ260CUS also opens at the same place.

Another low A that we jump yields the same results. If there is a difference, I feel that it is within the normal variability of opening times and none of the canopies seem to be significantly higher every time. Of course +\- 10 ft can make a big difference when in the basement. I would trust the OSP more on the dirty low stuff (but it is also my bigger canopy so softer landings).

I personally think that the the OSP is an awesome canopy and it does fly much more stable in deep brakes and sinks better than my BJ. The BJ and Troll both out glide the OSP by, I would guess, somewhere around 10 to 20 percent. The OSP is absolutely my choice for tight/technical & very close to the object LZs. Here in the PNW we don't have a lot of big fields to land in.

I have about 125 jumps on my BJ and about 65 on the OSP. I think JP has about the same on his Troll and OSP respectively, not sure though. I imagine he will chime in on this as well.

I think the OSP nose slats are a lot more important than the extra vents or the line length.

FWIW
About a week ago I watched TheSchrundy fly his OSP backwards for about 15" on opening from 250" and the canopy was totally solid! Super impressive pressurization characteristics!

Get off the internet cripple!

ft’

in"

haha, oops

I have an OSP and TROLL MDV and I don't notice much of a difference in opening. The glide ratio is less with the OSP than the troll, but how far you do you have to go on average? Does it matter? Some jumps In Washington, I prefer my troll just because of the long distance flight after opening. The Biggest difference i notice is coming straight down and sinking it in. The extra stabilizers prevent the canopy to surge side to side when coming straight down. My troll comes down just as well, but is not as stable. My troll seems to rock side to side more than the osp does. The nose vents help keep solid pressurization during the straight down sinking process. I have about 120 jumps on each, taken both terminal a bunch of times, slider down a bunch, and those are the differences I notice.

-JP

I too would say that the benefits of the OSP go a lot further than just opening heights. As other people said the OSP is probably the most stable canopy on the market for deep brake approaches. It also has more flare power from this configuration than a lot of canopies too.

 

The OSP was designed and built with slider off jumps and slow flight characteristics in mind. The Fox Xs is just a dirty old Fox that has been retro fitted. Or in other words, A knee jerk response to the release of the OSP. Either way it is a pitiful attempt at appearing progressive.

So the incorporation of the SLAT on the OSP has made a noticeable difference in performance in regards to pressurization of the wing and its stability while in deep brake approach.

But so far it seems that the incorporation of the extra vent and shorter line set has not made a noticeable benefit to performance in regards to allowing a jumper to successfully jump lower then other standard 4vented canopies.

I think that they have to make some kind of positive advantage in earlier altitude opening or controllability, but is the extra benifit that they provide large enough that we, the pilots, can even notice????

If we can see or feel the advantages of these newer mods., then we would be more confident to further expand the lower limit, which is definitely a goal of mine, and many other jumpers as well.

Keep it coming if ya have adequate experience in these regards!

What about the FOXxs????

What about venting all 7 cells? Of course this would be for sub 200 FF use, but would that make a positive difference, or could end-cell vents effect heading performance??

Just to be clear. The slat does nothing to pressurize the canopy. It helps prevent stall onset by venting air onto the top skin to help maintain airflow in deep brake approaches. Also the additional stabilizers contribute a lot to the OSPs stability.

Again just to be clear. The Troll DW always had 5 vents. The OSP has oversized vents.


The end cells of your canopy don't provide as much lift as other cells so the benefit of venting them wouldn't be that great either. Also the tail of the outside cells is already about the highest pressure zone of the canopy on opening. I would think adding vents would increase that pressure too much.
And of course the heading performance would likely suffer.

That's not true.

The original concept that became the FOX XS predated the OSP by several years. It was a one off project canopy built for Greeny-UK, who wanted to do some very low freefall jumps.

It was later revived and released as the "XS" with some changes from the original. That release may have been a response to the OSP, but the original design was definitely not--I'd guess that if the OSP had been on the market then, Greeny would have simply bought one instead of working with Apex to create his customized low freefall canopy.

I am aware of the history of Greeny's jumps and canopy. But really lets face it. His proto type was still based on an ancient airfoil that was retro fitted with shorter lines. The truth to Greeny's success was from his constant experimentation of techniques and his slow progression to lower altitudes.
The OSP on the other hand has multiple modifications to improve pressurization, slow flight characteristics, deep brake stability and flare power.
Unless I am mistaken the Fox Xs is still a dirty old Fox with some big vents and short lines.

As I understand it his deployment techniques were probably a larger defining factor than his canopy. Didn't he even have to use a shorter bridle for his deployment style?

Lay your innovative new airfoil OSP out on top of a dirty old Mojo some time and tell me about "based on an ancient airfoil."

The only new airfoil brought to BASE since 2000 (Flik and Blackjack) was the Se7en. Aside from that everything has just been adding new features to existing airfoils. Some of those features (like the nose slats) are pretty revolutionary, but they do not involve changes to the underlying airfoil.

Nope. You can choose without vents or with vents on 1,3 or 5 cells. Just ask to JNO

You miss understand my post.

So with the shorter line sets on either canopy, I understand the purpose to be that the wing will reach line stretch quicker, which enables all other characteristics in the sequence after line stretch to begin sooner as well??? This is the concept right?

If so, are they just using 1 size smaller line sets? Like a line set from a 240 and put it on a 260? Or are they specifically using a new measurement for the lines?

What are the cons of this?

Well said tom.

I have never posted here before but i'm an avid supporter of the OSP so this got me inspired. Just about all my jumps have been on an OSP (Overall Superior Canopy) .
Technically speaking i don't know if the 5th vent makes a huge difference although it has no downsides either. larger vents, additional stabilisers and slat technology in fact make sense.

The shorter line set, i thought was for;

A- less distance travelled to opening &
B- less pendulum under the canopy helping to prevent off headings and help with stability.

70% of my jumps have been slider down in AUS & US, the remaining 30% in Europe/Malaysia slider up with no problems, using a big mesh slider and no slider control.

I have no problems sinking into to tight landing areas and do not land heavy although sometimes it's what you have to do for accuracy. My mates jump Fox, Trolls and have no problems either. i personally would only fly either an OSP or Fox canopy for tight landings areas and dirty low jumps, I don't know anyone jumping a FOX xs but i would think it would be only an improvement in the basement so to speak.

My preference for sub 150ft would be OSP over Troll MDV & an assumption for the FOX xs over the FOX

thats just my biased 02c


OSP info
http://www.basetroll.com/products_5.html

I think there is a little more to it than that :-) Also the shorter lines improve stability of the canopy and does alter the controls slightly too.
No clue. But I would think that simply stepping down a line set would leave the cascades in the wrong place. Maybe it's close enough to not matter.

The cons are if you get the lineset wrong you are fucked :-) But as they say, BASE jumpers are test jumpers.

What is your basis for comparison?

If all your jumps had been on a Mojo, would you be saying that the you would personally only fly a Mojo?

I often see people who are very devoted to some piece of gear because they've never tried anything else. This seems to me a somewhat odd reason to be devoted to something.

I cant mentally picture this in regards to improved stability. Can you explain more?

Also, in what way does it change flight controls? More control, less? Or same amount of flight control, just everything is at a different place in the control stroke?

Thanks, I appreciate this disscussion.

The lines on the xs are 10% shorter for the base line length on the line chart (much shorter than one size canopy difference) and the other measurements are unchanged to maintain the overall trim of the canopy for the given size.

Not really :-) Im an anonymous internet identity not an aerodynamics engineer :-) But I believe it is the relationship between the airfoil and the suspended load (pendulum will com into play here too). Any canopy that is relied upon for is stable flight characteristics will have shorter lines ie. BASE, Reserves, CRW. With the line sets being longer on general purpose canopies, the longest will be the most high performance canopies (mostly to encourage dive).


It will most likely physically change the control envelope very little. But they will probably feel more responsive. Generally a canopy with shorter lines feels like it gives more feed back to the pilot with "a seat of your pants feel". This is of course if the pilot was ever aware of his canopy in the first place.
Disclaimer: This is based on skydiving canopies. But a canopy is a canopy.

Longer lines = longer moment arm. Another way to look at it, although it isnt really applicable, technically: tie a heavy washer to a 3 ft piece of string, and walk around your house, the washer will swing all over the place. Tie the same washer to a 3 inch piece of string, and naturally it will be more under your control.

I'm no physicist, but I think Colm is pretty close. However, I think he has it kind of backwards scientifically. Disclaimer: I COULD BE FORGETTING ONE, TWO, OR ALL THREE OF THE LAWS OF MOTION

The scientific property that comes to mind is isochronism. In this case, it simply refers to the fact that the body in motion at the end of the pendulum will complete one full period in the same amount of time whether or not it has a high amplitude or low amplitude (high swing or low swing). By reducing the line length you will decrease the time needed to complete one period, but increase the speed of the oscillation.

Where this would be a benefit in canopy design is that the energy used to create the oscillations (in this case, velocity and acceleration from side to side) would be spent quicker in the shorter line-set, and fall into a predetermined equilibrium faster (as opposed to a static equilibrium which should be equal).

You could try this at home to prove it if you wanted. Tie a washer to a short string, and the same size washer to a long string. Drop them both from the pivot point with a taunt string, and you will see that the shorter string will find a predetermined equilibrium before the long string. However, you will also notice that the shorter string will complete each period quicker than the long string.

You could argue that I am wrong, which I probably am, but I wont listen.
Someone hit me with some Newton here.



Edited to add: There are lots of other controllable variables such as canopy size and design, weight shifts, and toggle input.

You really shouldn't take a model and apply it out of context like that.

Why? Feel free to explain how I am out of context, oh wise one. I'm all ears. Like I said in my post, I'd like to know if I am off, but your post is useless to me if you don't explain why you feel the way you do.

Cheers!

Edited to add this chick, who obviously cares less than I do.

Apples doesn't taste like oranges, even though both apples and oranges are fruits.

I'm a big fan, picture man.

congratulations, your post helps me to identify 3 fruits.

All insults aside, what does that have to do with the advantages/disadvantages of shorter line sets?

Im confused. What was the 3rd fruit again?

I am :) Muahaha.

What I mean is that you can't really apply the model of a pendulum and the property of isochronism (now that's a hard word, I wonder if I spelled it correctly?) to a parachute arbitrarily to explain the consequences of design choices, because a parachute system is very complex. You are applying a model that does not relate fully to the system you apply it to. There's a lot of variables affecting the sum. I am just making words up. Some canopies might benefit from from a longer line set, simply because it makes for a better airfoil. As an example.

So, picture man, I do not mean to insult. I am not sorry if I did, that' would be gay. But I do feel the need to explain myself. And maybe, I did not provide a good enough explanation to start with. But I would never admit that. Again, that would be gay.

Makes sense. Especially since line length has a lot to do with how the canopy is trimmed.

I was purely speculating on what one benefit could be in response to a post stating why longer lines could be a stability benefit. My buddy who relined a canopy for low jumps did it just to get to line stretch faster. Thats probably a more likely reason for them.

And I did not feel insulted, fruit guy, so no need to be gay or whatever. But clever insults are always appreciated.