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Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Mon Jun 15, 2020 10:14 am
by mgs
Flysurfer no doubt chose fibreglass as it met with their design remit.
I cannot imagine as to what conditions the fibreglass rods would actually break. (On the basis the kite is flown and maintained as it should be.)

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Mon Jun 15, 2020 2:39 pm
by merl
Sounds like a lot of wild speculation about materials from people who maybe don't know as much as they think they do. Maybe fiberglass makes a lot of sense here. Combining composite materials is a tricky business for sure:




Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Mon Jun 15, 2020 7:55 pm
by Horst Sergio
@merl:
Yes I think it is a lost discussion as I am sure Flysurfer had to think about 1000 other factors passing this new way of construction before they started to think about to start a production for special hybrid material battens,

that maybe could save another few gramms or what else, maybe something for VMG v5 in 2030. I also added fiberglass battens in the past to FS Kites with the hope to make them better and I am sure it is 99% about where and how to place them and less than 1% about if there is a better batten composite combination. From my experience also from many month in sail and kite repair shops it is even better to have materials in one construction not to much distanced in their density and hardness as otherwise at the connection points you will see how the soft material will die over time even if protected with reinforcements. To me one important factor why soft kites build out of all around soft materials can live as long as they did, instead of tube kites with much wider spread inbetween soft ripstop and much harder part for example at the conection points and tubes.

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Mon Jun 15, 2020 10:53 pm
by Bille
bohme wrote:
Mon Jun 15, 2020 9:13 am
Bille,
...

I would be genuinely very interested if you know a fibre composite with a compression strain failure higher than S-glass.

Jacob
Dude -- are you a lawyer ; because they are really good at diverting attention .
SO
how did ultimate compression come into the conversation ? I distinctly remember talking
about mixing Carbon with other materials , to yield WAY higher strength / weight
ratios, and stiffness , than what you get with fiberglass fibers with epoxy.
AND
the flexibility, can most definitely be adjusted to fit the users needs.

Your S-glass is stiff and strong , but you pay a 20 to 30% weight penalty, for using it ; over
other more modern materials !! :bye:

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Mon Jun 15, 2020 10:54 pm
by Bille
merl wrote:
Mon Jun 15, 2020 2:39 pm
Sounds like a lot of wild speculation about materials from people who maybe don't know as much as they think they do. Maybe fiberglass makes a lot of sense here. Combining composite materials is a tricky business for sure:
...

YEP --- fiberglass is Cheap !
But
You just supplied the information needed , to prove Yourself wrong , about my
knowledge of composites ; you just didn't realize it ! :lol:

Look at relative Strength/ weight , then Stiffness/weight , in the chart below .

Here's how it works :
Carbon is WAY stiff / for it's weight, (a LOT stiffer than S-glass) ; but carbon is brittle
and breaks easy.

Kevlar is Really strong / for it's weight , (but hardly has any stiffness ) .

Watch what happens when you mix the two ... ...

When i built my fake leg ; i used a combination sandwich, of Carbon and Synthex fibers ; i
ended up with a fake leg that was 30% lighter, and near twice as strong as
any of the (8) state of the art legs, that were made for me in the past. I should
know, because i broke 7 of those legs, at a cost of $-15,000 each ; and have
bin using the one i made for 6 years now.

Bille

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Tue Jun 16, 2020 12:28 pm
by bohme
There is too much BS in this thread.

This was originally about a 2 level bridle made possible by using some FLEXIBLE battens.

I will now explain why glass fibre might be a good choice for THIS application:

Imagine you have a straight rod batten you want to curve into a closed circle. You can either use GF or CF.
T700 carbon fibre : 1200MPa break stress, 120GPa modulus, 1% break strain level
E-glass fibre : 800MPa break stress, 40GPa modulus, 2% break strain level (yes, it look bad...)

For the same battens properties (same force and diameter of the closed circle), both M (bending moment) and EI (beam stiffness) MUST to be identical.
For this to happen I (moment of inertia) need to be 3 times higher for GF. It is not looking good for GF...
The thickness of the GF rod needs to be 1.316 timers thicker. GF is looking heavy...
HOWEVER, The formula for stress My/I shows that CF has 229% higher stress level than GF, but only 50% extra strength. OOOPS

Conclusion:
Glass fibre is stronger than carbon fibre. For THIS application.

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Tue Jun 16, 2020 12:52 pm
by joriws
I think Bille on other older threads was after rigid kite, like "rigid wing hang glider" so I interpret his statements on this background that VMG2 must be rigid. And I answered in this thread for Bille on this background that what if kite design is that kite must be flexible to allow it turn properly. Also lesser point load from batten to fabric so that fabric will last longer. etc. There could be lot of other reasons than "being cheap" for selecting more flexible material.

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Tue Jun 16, 2020 1:12 pm
by jumptheshark
Are the battens in the Peak4 fiber glass? They are super flexible. Armin coils them up pretty tight in this video at 5:30. He doesn't mention their material. I would suggest that even though GF is mentioned on the VMG page, that is fairly generic term and may not be completely descriptive when it comes to proprietary kite construction materials.





As pointed out in the posts above, It may well be that rigidity is not as important as flexibility for this application. As to weight, as evidenced by the Peak4, which is full of battens, cloth would appear to be more consequential.

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Tue Jun 16, 2020 1:55 pm
by joriws
jumptheshark wrote:
Tue Jun 16, 2020 1:12 pm
Are the battens in the Peak4 fiber glass? They are super flexible.
Normal Flysurfer "rigid-LE-battens" are plastic a bit like grass trimmer line. They are sewn to pockets which makes LE more shape/rigid.

Re: Flysurfer is going to beat fishnets? (Release of VMG2)

Posted: Tue Jun 16, 2020 5:22 pm
by Bille
joriws wrote:
Tue Jun 16, 2020 12:52 pm
I think Bille on other older threads was after rigid kite, like "rigid wing hang glider" so I interpret his statements on this background that VMG2 must be rigid. And I answered in this thread for Bille on this background that what if kite design is that kite must be flexible to allow it turn properly. Also lesser point load from batten to fabric so that fabric will last longer. etc. There could be lot of other reasons than "being cheap" for selecting more flexible material.
YES -- your mostly correct on that ; but i would never start a debate
over aerodynamics , because the choices made are mostly subjective . :thumb:
Like with Hang gliders, we have weight shift control, which must be
very flexible skin airfoils or they don't work, and rigid-wing airfoils
that need devises like spoilers to turn , (I fly , and enjoy -- BOTH) !!

My original question for choice of materials for the battens, was only
meant for, (curiosity) ; it certainly wasn't meant to deliberately get people
Heated.

As you know , i build my own fake legs , so if there is a combination
of composites that are specialty used ; then it peaks my interest immediately.
Walking with 30g of extra weight , over 18 holes of disk golf ; can make the
difference between being tired , or Really tired , because i exert about 25 to
35% more energy than a guy using their stock god given legs, every time
i walk.

Bille