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DonFibonacci

Djinn vs Skyburner Fulcrum (venting designs)

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On 12/30/2019 at 11:41 PM, John Barresi said:

I placed the venting in our mid vent very specifically, so as not to lose sail pressure in the wrong places, and the vents are also a bit smaller than most mid vents with the Sync Bridle working to moderate speed surges and pull, so we didn't need as much - all this means more sail in the lower end.

@John Barresi (and other builders out there) - this is probably a separate topic, but I'm interested in the design process that goes into, for example, figuring out where and how to vent the MV.  Do you just use experience and feel, or is there any measurement/analysis going on to guide the changes you make?  How do you decide what new venting to try?  At each iteration, do you build a completely new full-size prototype?  I'd be interested in any details you're willing to share.

I enjoy building kites, but I don't know how to evolve a design to get a desired result.  I'm sort of stuck at the point where I know what behavior I'd like to improve, but not how to get there.

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Alas, I'm not much good for data because I don't "design" per se... It's more like sculpting, because I know a feeling, a look, subtle proportions, I have 30 years worth of experiential (not scientific) experience on the platform so I know what I want and can see / smell a ghost image of it in the back of my mind so it ends up being more intuitive.

But I am the exception, in many ways.

I'll sound like a jerk here, but with due respect, also remember that "recreational" fliers aside, over 99% of the hard core quad fliers in the world, even many of the "masters and experts", quad flying is still something they just do on the weekend, so even for decades on end it's not the same as a day in and day out driver who actually can DO everything they're claiming to be an expert on.

This doesn't de validate their experience or taste, but it's a very real dynamic that is rarely spoken of - proof is in the pudding.

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@DonFibonacci Great question and very worthy of its own discussion..   I spent quite a bit of personal thought into venting options.

My thoughts and the thread are here

 

All of that being said, there's a bit of science AND art to venting.. Some of it is as simple as putting a hole where the pressure has a tendency to build too heavily.. That comes with a price though as you can render a perfectly good sail almost un-flyable.

I've personally gravitated to what I call the balanced venting where pressure relief is across the entire face of the sail. While that works incredibly well for a flow type of flier like myself, it does indeed load up differently and someone that likes to really load and pop the sail would feel a delay.

All that being said, if you are venting your own design, what looks right to you will probably work for you as long as it's symmetrical between the left and right sides of the sail.. If there's a part of your sail you know get overloaded in a gust, that area is probably your target for pressure relief.

 

 

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From @John Barresi in the original thread:

Quote

Alas, I'm not much good for data because I don't "design" per se... It's more like sculpting, because I know a feeling, a look, subtle proportions, I have 30 years worth of experiential (not scientific) experience on the platform so I know what I want and can see / smell a ghost image of it in the back of my mind so it ends up being more intuitive.

But I am the exception, in many ways.

I'll sound like a jerk here, but with due respect, also remember that "recreational" fliers aside, over 99% of the hard core quad fliers in the world, even many of the "masters and experts", quad flying is still something they just do on the weekend, so even for decades on end it's not the same as a day in and day out driver who actually can DO everything they're claiming to be an expert on.

This doesn't de validate their experience or taste, but it's a very real dynamic that is rarely spoken of - proof is in the pudding.

@John Barresi Thanks for the reply!

What about the other part of the question - as you're working on a design, are you creating a full new prototype kite for each iteration, or do you try to "hack" an existing prototype as long as possible?  For example, I could imagine if you wanted to try less venting, you could tape over existing venting to a certain degree, to try it out.

Personally, I find the time and expense of building a new kite just to try an idea pretty daunting and that holds me back... but then, I'm a really slow builder, and it's definitely not my day job, either, as you point out.

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29 minutes ago, riffclown said:

I spent quite a bit of personal thought into venting options.

Thanks for splitting this off.  I'm interested in venting, but I mainly I was using it as an example. What really interests me is two things; first, are there any ways that builders "analytically" determine how to improve a design, or is it just experience and experimentation?  Like any specific testing?

Second, once you've decided to try something new, are there any techniques for seeing how well it might work without building a whole new kite?  For example, taping over existing vents?  Has anyone ever built a prototype kite specifically to be "adjustable" to make experimentation easier?

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I know of one person @Stuart McCullough that has made a convertible quad with removable vent covers. 

Adding vents to as an existing kite is pretty easy. Adding too much vent is just as easy though. Decreasing venting will require a tradeoff of additional weight to cover the vent with a fabric of some sort.  As with everything else. It's a balancing act. I bought a bunch of  cheap closeout material to experiment with.  It's what I use when trying new design elements. I usually add midnight to  the name  when I use this fabric. Failure has to be an option or you might not get past the afraid to cut fabric stage. Learn from everything yuh ou build and you will begin to see what works and what doesn't before you start your build.

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Yes to re-hacking an existing configuration, more vents or tape, but only in brief to smell if it's going the right direction... I also have no patience, but get pretty lucky with wisened cuts.

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How well does Icarex or ripstop nylon handle having a seam ripped and re-sewn?  Seems like it wouldn't work too well, like you'd just have created a nice perforation for it to tear along.

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You can go back over the same holes, but of work but totally possible - and about perforation, depends on the size of the panel, location, etc.

For vent prototypes, I just keep sewing on new layers and cutting out the old ones from behind. ;)

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