Forums: Skydiving: Gear and Rigging:
Questions about the Cobalt

 


Jimbo  (D License)

Jul 31, 2001, 8:38 PM
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Questions about the Cobalt Can't Post

The Cobalt has managed to get quite a bit of attention around here, certainly enough to make me curious. That said, I've got a few questions...

We've often heard that the Cobalt is suitable as a beginner canopy when loaded between 1.2 and 1.4. Since the conventional wisdom (maybe outdated, maybe not) is that an elliptical canopy at this loading is not suitable for a beginner, I have to ask what makes the Cobalt different.

How does the Cobalt differ in design and handling from a Stilleto, Crossfire, or other 'high performance' canopies?

What is it about the Cobalt that makes it a suitable canopy for beginners that isn't present in the Stilleto or Crossfire?

How is the forward speed on Cobalt? Is it fast, slow, in between?

I'm thinking of demoing a 170 which I'll load at just a hair over 1.4 and just trying to get all the facts before I make my decision.





<FONT SIZE=-1><EM>Edited by Jimbo on 7/31/01 10:21 PM.</EM></FONT>


aufreefly  (A 35174)

Aug 1, 2001, 12:09 AM
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Re: Questions about the Cobalt [In reply to] Can't Post

For what it is worth I started jumping a cobalt 150 at ~1.5 from my 90th jump. I now have over 220 and have nothing but good things to say about my cobalt (once I figured out that the canopy really opens better when pro-packed, I would'nt recommend the psycho pack). If you are comfortable under canopy then 1.3to 1.4 probably is not too high of a loading. The only other canopy that I have jumped is the stiletto and the cobalt seems to have a bit more flare. I hope that this helps.




cobaltdan  (D License)

Aug 1, 2001, 8:39 AM
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Re: Questions about the Cobalt [In reply to] Can't Post

the cobalt uses a different airfoil than the stilletto, crossfire, saftir,fx,vx, etc...actually all of those canopies use the exact same airfoil. all of those canopies were based on a stilletto.

different airfoils have different pressure distributions on the top side. this pressure graph combined with many of other vartiables ie. planform, alpha, cg, cl, etc..will determine the performance characteristics of your canopy. by just being elliptical all that means is that it can be a more efficient wing.

a stilletto airfoil/planform is such that to reduce excessively high riser pressure the jumper must be weighted under the nose. this has the advantage of decreasing riser pressure but makes the canopy twitchy and with twists keeps the canopy spining.

the cobalt uses a new airfoil. the jumper is suspended back towards the wings center of gravity. this makes for a stable, non twitchy flyer that if twisted up can fly straight.

other major differences include our tensioning technology. the reason cross bracing increases efficiency of a wing is because it reduces the airfoil distortion on the top skin by pulling down distorting billowing fabric closer in line to the shape modeled. this is not the only way to skin the cat. atair has developed pat. pending technology for inducind a specific strain pattern into the nose and top skin. this reduces the distortion without the negative opening charicteristics of x bracing.

tensioning works as is evidenced by the fact that even conservative flyers fly cobalts 20sq' smaller than a stilletto or sabre/ we have landed cobalts at up to 3.6#/sq' / set the current world record for the smallest 9 cell: the cobalt 65 (tony canant has been jumping it constantly at about 2.7#). how many people think it would be possible to safely fly and land a stilletto or sabre 65? it wouldn't be possible as the wing does not have the efficiency required.

openings are very different. the cobalts are designed to limit conductance of inflation air from the center cell towards the outer cells, creating a distinct 2 staged opening. the competition cobalts have a multistaged opening (ie 3-5-7-9 cells). this makes for safer higher speed deployments. we have recorded data from live test jumping deploying at speeds up to 228mph. head down deployments to 180mph. at 180mph a premature deployment on most canopies would either seriously injure you or kill you.

beginners: canopy is very stable, not twitchy, docile, staged openings create on heading openings (on a stilletto spinning on opening is common because the entire canopy inflates before the slider moves, the leading edge can not fit in a straight line until the slider is down, this creates a violent snaking motion of the leading edge, this can easilly be seen by videoing a stilletto deployment and watching in slow motion). cobalts are predictable and responsive without being too fast. because of the high efficiency the foward speed is low. for equal foward speed to a stilletto or sabre you will be loading a cobalt heavier. this added efficiency wing also translates into a huge flare available in the low end (where you do not have it on a stilletto).

hope the above was helpful, i had to pen it in a hurry..
if you have any further question feel free to call me at our office 718-596-8641

sincerely,

dan
atair
www.extremefly.com





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