v-tec

[guest]

Dwain,
I'd like to clarify and elaborate on a few points you make in your post and add my comments on the subject for those who originally asked at the inception of this thread.



>Ideally on
>deployment next to a solid
>object the canopy should have
>zero forward speed (and minimal
>descent rate) until you are
>satisfied that it is pointing
>in the correct direction and
>you are ready to start
>flying forward


Yes this is ideal, but theoretically not possible. Does an aircraft wing generate lift at a stand-still? Of course not, it must move forward to generate lift. The same is true of a ram-air canopy. Rapid presssurization is a good thing but it does not mean you can be stationary on deployment.

A wing, any wing, has a given stall speed. It does not slow to 0 mph and then stall. Typical BASE 7-cells stall in the 5mph range dependent on wing loading and other factors.
Slow flight to stall is the best way to get a canopy to fly as slow as it will possibly go. On the other hand,getting a canopy to go from packed to safely flying outside it's flight envelope (i.e. 0mph) all within a second or two is a tough one to pull off.

I make this point because the pursuit of zero-momentum openings can be a dangerous one. Deployment stalls can rapidly become as big a proplem as an off-heading, if not bigger. It is possible to have a _low_ (forward) airspeed on opening and this is worth pursuing.
We will acheive lower speeds than we typically have now with slow flying canopy designs, proper wing loading and deployment brakes carefully set in accordance with the suspended load. It can get better than it is, I'll agree. But I disagree that horizontal speed on opening can be reduced by simply altering pressurization charteristics.



Regarding the development of more securely closed rigs: I don't think it is fair to condemn any manufacturer for pursuing this.

If Pin-closed rigs didn't come along when they did we would still have them now, only there would be a list of fatalities that prompted us into action rather than forethought.



>FINALLY in mid 99 Basic Research
>started taking significant steps in
>research and development towards fighting
>the demon of object strikes.
> The result was simple
>in concept (like so many
>good designs): Locate some
>of the air intake vents
>to capture airflow when forward
>speed is at a minimal.
>

As you may remember, in 1998 I showed you a prototype canopy that we had been jumping since 1994. It had meshed vents in the bottom surface.
We explored this feature not to apply to the Mojo but rather as a general research and development project. We decided if there were any negatives associated with the meshed vents we would backburner the project.

The Mojo already had a reputation for opening with very solid pressurization so we didn't feel a strong need to improve on this.

We did not introduce this feature at the time for two reasons: One, the gain in presurization performance was limited (compared to a standard Mojo) and second, our tests confirmed that air flowed back out these vents. This resulted in what I called "soft turns" and stability problems in turbulence. The inflated canopy is a high-density airmass enveloped in a nylon cover. The pressure inside the canopy is higher than that which surrounds it. If it wasn't, it wouldn't be open. As the wing moves through the air, displacing air molecules, pressure along the lower surface increases. We believe a laminar boundry exists along the lower surface, outside the vents, helping the air to stay inside the canopy. However, when airspeed drops so does the lower surface pressure, at this point the canopy is susceptible to losing air through the vents. When the pilot compresses the wing by pulling on a control toggle(s), the air inside is displaced and must move somewhere - the vent is the path of least resistance. High pressure seeks areas of lower pressure. Hence the soft turns and instability in turbulence. Accuracy jumpers had abandoned the concept of "soft-cells" for the same reasons. Airlocked canopies address the same pressure loss issues only they are focused on the leading edge inlets.

With what we continued to learn from our vented canopy, we have since moved onto yet another approach to the same end that provides additional advantages beyond initial pressurization. Time will tell.

I'm not discrediting exploration in this area or BR's introduction of a vented canopy. I'm also not passing judgement on the concept of vents.

So in answer to Chris who first posed the question about vents: Yes, vents do have some merit. My point is that having been playing with them on and off for over six years, I feel they are not without their drawbacks.

More importantly, the point I want to stress is that Tom A. is correct by taking a critical approach. After all, it is life support equipment.
Before adopting this, or any new technology, evalute it critically (not emotionally)for yourself. :-)




Adam Filippino
Consolidated Rigging
http://www.crmojo.com

[guest]

!Those who are interested in VTEC!


Referring to the previous post.
<Before adopting this, or any new technology, evalute it critically (not emotionally)for yourself.<

I don't know who was evaluating vtec emotionally, but for myself and everyother vtec jumper I've spoken to, who has cirticized/ assessed/evaluated the vtec on an EXPERIENTIAL (not emotional) level, has given only positive results/outcomes. I have never heard a negative word about jumping the vtec. If you get a chance, jump it, make your own critical evaluation, and give your report.

<Yes this is ideal, but theoretically not possible.
Does an aircraft wing generate lift at a stand-still?
Of course not, it must move forward to generate lift. The same is true of a ram-air canopy. Rapid presssurization is a good thing but it does not mean you can be stationary on deployment.>

These statements are true, but minimizing forward movement is very helpful, and at this point in the development stage, is the best you can do with a ram air canopy. The vtec helps to minimize forward movement and provid a solid steerable wing through rapid pressurization - in the time a ram air canopy is struggling to inflate. That's my theory. But, theory is limited and can only tell you so much. For myself, I prefer practical application for my own critical evaluation, which is what I will be doing later this evening on a nice little building in my backyard...

JJ

[guest]

may be you didn't make the same Vtec on the mojo that's why it didn't work well
i saw a lot of people in Europe, specially in france, who doesn't like the mojo because of the forward speed at the opening.
i spoke with the 4 very experienced base jumpers who made the jump for the next patrick passe's movie, they were very unhappy because of this problem. some strike the cliff, some have opening problem...they made a very bad advertising fo the mojo
the opening of the mojo is very solid, yes, but with a lot of forward speed at the opening, it's a dangerous canopy

[guest]

"it's a dangerous canopy"

As my MUM will atest "All Canopies Are Dangerous"...just depends on the lad(lass)'s ability to understand that edge....and then respect it...

up your bum ladies

[guest]

Sorry Goggle, but in defense of Adam's canopies (Mojo), apart from when my own body position was questionable (either intentionally or unintentionally) my Mojo smacks me on heading always.

I would question the very experience or skill of your "4 very experienced friends".

Too much forward speed - ask your friends to check their brake settings. Cliff strikes - ask your friends to check their response/reaction times to off headings, their body positions, their choice of cliffs (too underhung??).

A good tradesman does not blame his tools!!!!!!!!!!

[guest]

Some info:

Vtec is BR's adaptation of an old idea. Ask any very experienced accuracy jumper about bottom skin vents!!!!

I finally started jumping Vtec this week. Picture a 300ft chimney surrounded by 60 foot trees, lots of turbulence and cross winds (yes, silly jumping weather). Landing area is either a lake full of toxic waste or a 10x10m area surrounded by the 60ft trees and directly below the exit point (no room for full glide flight).

Nice delay, rapid opening above trees, went into deep brakes asap, vertical descent into landing area through the turbulence.

Hardly any flare required - beautiful landing. Wouldn't have done it without the Vtec Fox.

Disadvantages raised by others in this thread:

Cost - $250 is a lot less than a medical bill or a few weeks off work!!! One weekend off the juice or a few less parties this year and your body will be thanking you for the softer landings!!

Tearing the mesh - It is the same chance as tearing canopy material only the damage may be slightly greater because mesh creates a greater snag point!!!

Vents acting as pressure outlets - if it is too windy or too turbulent you shouldn't be jumping (therefore, this is a pilot error fault and not a canopy design fault!!!).

Advantages:

Professionally built, excellent quality control, great for tight landing areas (Australian tight rating) , rapid inflation after line stretch, etc.

We've tried it - you should buy it..

more info at www.basicresearch.com