Vtec

[Faber]

BR Manual point 2.4 (Use of Fox canopies)

FOX canopies with Vtec are recommended to use only the #1 (shallow) brake setting.

Why?
I just resived my first vtec canopi,before that,had i a Fox(older model),where there were 2 brakesettings,so now i wonder why vtec only have one..

I have asked BR the same Q,but belive im not the only one who wonder,so it could be nice to get the info out here aswell(ill paste it soon as i get an answer),but any thourgths?

[jason]

As I understand it, there are a couple of reasons for this.

First, it seems that a lot of jumpers out there, when faced with a severe off-heading, tend to over-amp on the rear riser corrections (if they're using the rear risers, obviously). If your brakes are set deep, that's more likely to result in you stalling your way into the object rather than turning on a dime. The rationale, as I recall, was that VTec gives you more control at an earlier point in the opening sequence and makes the DBS obsolete even in the best case, and dangerous in the situation I've mentioned. Somebody will correct me if I've screwed up their logic there.

Second, and more important to me, if you put a VTec canopy in the DBS, you'll notice that the recoil from air going in the vents and out the nose is more pronounced. I expect this contributed to a particularly ugly oscillation I experienced once, and I haven't used the DBS since. All has been well.

. . . That said, I got BR to put the DBS on my VTec Fox when I ordered it just to have the extra flexibility. I understand some people set their deep and shallow brakes for optimal slider-up and slider-down openings. Anyway, if you want them you can always add them yourself -- you should be tweaking your own brake settings regardless.

[Faber]

Thanks for the help

[Dwain]

To answer this you need to first understand why many BASE canopies have two brake settings instead of just one.

Basically 98% of the time we want our brakes set as deep as possible to minimize forward speed on deployment (and therefore reduce the chance of an object strike). See details about avoiding an object strike here -> [a href="http://www.blincmagazine.com/cgi-bin/forum/dcboard.cgi?az=show_thread&om=163&forum=DCForumID1 7"]Read me![/a]

However the ideal brake setting for slider down will often result in a stall for slider up: Basically you should have two settings: The deepest one you use for slider down, and the shallower one you use for slider up. (in actual fact you should have three settings, as you can set the brakes a little deeper for sub terminal slider up deployments than you can for when deploying in a hard track at terminal). These settings are highly dependent on many other things besides deployment airspeed such as the canopy type, size, wing-loading and air density but that’s another long topic.

To summarize, basically you have a shallower setting because you can’t use the deepest one for slider up. If, in fact, you can use the deepest one for slider up then that is a good indication that your deepest setting isn’t as deep as it should be. (Note: Many non-vented canopies have factory set DBS that can be used for sub terminal slider up as the factory DBS are often very conservative).

However with the introduction of the Vtec on the FOX canopy things changed (in many different ways). Due to the changes in pressure waves inside the cells during slider down deployments, the optimum slider down brake setting became slightly shallower compared to a regular FOX. What was subsequently discovered during testing with the Vtec (early 2000 from memory) was that the Vtec slider down brake setting didn’t result in a stall at terminal slider up. So there was no point of putting a second shallower setting on the line as it would only result in increased forward speed on deployment and a greater chance of object strike. Thus the reason why a new Vtec FOX has only one brake setting by default.

For FOX’s modified with the Vtec, their brake lines already had two settings. For many people their deeper brake setting was too deep and resulted in backward surge (on Non-Vtec canopies this backward surge would have actually resulted in a deployment stall). Therefore Basic Research recommended that people not use the old FOX factory set deeper brake settings. The FOX factory set brake setting for a new Vtec is about midway between the factory shallow and deep setting on a non-Vtec FOX. (However you shouldn’t ever have factory set brake settings on your canopies because everybody knows to customize their own brake settings – correct?)

I personally customize all my bottom skin vented/valved canopies with two brake settings (2 custom FOX’s, a FLiK and a Troll). However my preferred slider down brake setting (which does result in a stall slider up) is probably too deep for most jumpers comfort margin (however I’m probably more paranoid about object strike than most).

BTW: The term “Deep Brake Setting” is misleading and shouldn’t be used in BASE. “Deeper Brake Setting” is much better. Same for “Shallow Brake Setting”.

Note: For those with Vtec FOX I recommended getting valves fitted (myself and others have been jumping Vtec with valves for over a year with great results). I also recommend a fifth upper control line if your wingloading is low. Australian BASE jumpers discovered the benefits of modifying their BASE canopies with a fifth upper control line to get a better flare in the late 80’s and it’s only in the last couple of years that US and Slovenian BASE canopy manufacturers have finally started to catch on. Note that by adding a fifth upper control line you’ll probably have to change your brake settings again (more fun!).

[Mike]

Dwain-

I am assuming that the 5th upper control line you mentioned would fill the gap between the existing third and fourth lines (counting from the outside in)...correct?

Also: You seemed to imply that a Vtec could be retrofitted with a valve system (by BR?). Is this this same valve system on the flik? Speaking of the flik...what's going on? When are they planning on putting this contraption on the market?

Sorry to bombard you with so many questions, but BR won't respond to my emails...

Thanks

[imported_Tom Aiello]

>...a Vtec could be retrofitted with a valve system (by BR?).

I believe BR offers a valve system as an option on new canopies (FOX or Flik), or as a retrofit to existing BR canopies.

>Speaking of the flik...what's going on?

BR announced the release of the Flik at Bridge Day this year. I assume that means you can order one now. Last I heard, they were manufacturing the demos, but since that was a while ago, I bet they're done (or nearly so) by now.

--Tom Aiello
tbaiello@mac.com

[Dwain]

>I am assuming that the 5th upper control line
>you mentioned would fill the gap between the
>existing third and fourth lines (counting from
>the outside in)...correct?

No, the 5th upper control line attaches to one seam closer to the center cell.

If you look at the tail of a 7-cell canopy there are 15 seams or ribs.
Currently on a FOX or Mojo the upper control lines attach to seams 1,2,3 and 5 (counting from the end cells towards the center). The mod I am talking about attaches to seam 6. You should finger trap the extra line into the most inboard control line several inches above the cascade. You shouldn't attach the 5th line at the cascade junction because it makes the cascade junction pretty bulky. It’s a pretty easy and quick mod for any rigger to do. I've had this mod done to FOX's and Mojo's (as well as a bunch of other canopies) with good results.

Another 5-upper-control-line setup that works attaches to seams 1,2,3,4 and 6.

If you perform this mod and you find your stall point is too high then you may need to lengthen your lower control line slightly (rare that people need to do this).

Basically the mod improves flare performance because you are pulling down a total of 5 cells when you flare instead of just 4.


>Also: You seemed to imply that a Vtec could be
>retrofitted with a valve system (by BR?). Is
>this this same valve system on the flik?

Yes.
Also the new vented Troll has an excellent valve system. If anybody has a non-vented Troll, then I strongly recommend getting it modified with bottom skin vents and valves (if the retrofit option is available).

>Speaking of the flik...what's going on? When
>are they planning on putting this contraption on
>the market?

I have no idea. I don't work for BR. Try calling them - that always works better than email.

[imported_Tom Aiello]

>Also the new vented Troll has an excellent valve
>system. If anybody has a non-vented Troll, then
>I strongly recommend getting it modified with
>bottom skin vents and valves (if the retrofit
>option is available).

The retrofit option is definitely available. I can't remember the pricing, but I'm sure you can get the Mono Directional Valves retrofitted. The MDV's are, in my opinion, clearly the best valves on the market.

--Tom Aiello
tbaiello@mac.com

[Eddy]

Couple of questions from this thread - to anyone who knows or has a view...

What advantages are gained by the addition of these valves to a vTec Fox?

Dwain, you mention the 5th line mod for "lower loadings", why specifically lower loaded canopies?

Cheers

Seasons Greetings to those who celebrate.

Eddy
Team Crank

[Dwain]

>The MDV's are, in my opinion, clearly the best
>valves on the market.

Tom while I respect your opinion, on what experience are you actually basing this statement on? How many different valves systems have you actually jumped and/or tested?

I'm currently jumping 3 different types of valves (and tested a number of other designs that had varying degrees of success). While the MDV's are, in my opinion, excellent, I wouldn't make a blanket statement about them clearly being the best. In my experience each different type of valve has it's own pros and cons. Often the theory behind a valve doesn't prove 100% true in application.

So far I'd tentatively say that the Flik and Troll valves are the best two available on the market, each with it's own specific pro's and con's depending on the application.

Eddy: I mentioned the 5th line mod for lower wing loadings simply because I've never had much experience with it above a wingloading of 0.75. I know other people in Australia have used it with Pegasus and Fury canopies with much higher wingloadings with good results. I suspect you may have to lengthen the lower control lines if your canopy is highly loaded.

[3ringheathen]

>Basically you should have two settings: The
>deepest one you can use for slider down, and the
>deepest one you can use for slider up.

C: Who's on first?
A: You might want to change deepest to shallowest.
C: Which one?
A: The deeper one.
C: The deeper one is really shallower?
A: Yes.
C(getting frustrated): That doesn't make sense!
A: Sure it does: the higher you are, the shallower you are.

Ah screw it, I'm to tired to do a good Abott and Costello right now.
Dwain, you've got a typo to edit.

Happy Holidays,
I hope everyone's getting more jumps in than me.
Shouldn't be too hard lately.:'(
-Josh

[Dwain]

>If anybody has a non-vented Troll, then
>I strongly recommend getting it modified with
>bottom skin vents and valves (if the retrofit
>option is available).

Basically I'd recommend this mod to ANY non-bottom skin vented BASE canopy. This is purely because avoiding object strike (via rear riser correction) with a bottom skin vented canopy is much easier than with a non-vented canopy. Object strike continues to hurt or kill jumpers with a degree of regularity even when they haven't made a gross error.
Well designed valves replace most of the loss in glide ratio and flare performance (from full flight) associated with bottom skin venting so it's a purely win-win situation (except for the co$ts involved).

I've heard some rather weak arguments against bottom skin vents for beginners but I strongly disagree with this. If a certain canopy isn't suitable for a beginner then that is due to the canopy as a whole, not solely the bottom skin vents.

Anyone who has seen a low experience jumper heading towards a wall repeatedly yank widely on a rear riser as the canopy fails to respond and then subsequently smack the wall repeatedly, finally bottom out and then lie there screaming as their bones protrude outside of their body, would agree as to the benefits of bottom skin venting for beginners.

[imported_Tom Aiello]

>How many different valves systems have you actually jumped and/or tested?

Three. I have way more experience with the CR pac valves than with any other system. I don't really have enough jumps (less than 20) on either of the other two major systems (BR and MDV) to make comments based on jump tests.

>on what experience are you actually basing this statement on?

Mostly based on airflow inside the cells, compared to the design/construction of the valve systems. I believe that there is a "reverse rotor" (difficult to explain in words, but easy to draw a diagram) sitting right over the valve location on most of the canopies. This means that the airflow along the bottom skin (interior) is moving from the back, toward the front of the canopy at most times.

In order to avoid leakage (outflow), a valve must seal well against airflow from both inside directions (particularly the rear). In my opinion, the only valve system capable of approaching a full seal over the vent inlet is the MDV. I also believe that the upward directed "duck bill" of the MDV will allow cleaner inflow (less valve fabric in the path of air inflow) than either of the major competing systems.

Also, I speculate that the reverse rotor airflow is necessary to achieve full "flying" pressurization. This means that a valve which directs inflow with the canopies natural internal airflow will help create a "full flight" situation quicker. A valve which directs airflow counter to the equilibrium airflow (so, against the primary nose counter-rotor) may actually inhibit the canopy's inflation (as compared to a better valve or a vent--it'll still be noticeably faster than a canopy without secondary inlets).

In short, I think the MDV has done the best job of taking into account the internal airflow of the canopy in flight (or, at least our limited knowledge of it).

--Tom Aiello
tbaiello@mac.com

[Faber]

Hi evrybody
Have been whithout net for some days,so i havent readed them all before now.Thanks for more insigth in this.