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 Post subject: Gong Hellvator - 1rst KBHF with both foils providng pos lift
PostPosted: Thu Oct 16, 2014 11:10 pm 
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Gong, a renowned French brand producing high quality Surfboards, SUPs + Kiteboards and kites at reasonnable prices, has just announced an evolution that sets up the KBHF standards to a new level:

They will release before Christmas a KBHF with both foils producing positive lift. So, the rear foil is not a stabilizer anymore, it is a true wing.

JS wrote:
An inverted rear foil creates negative (downward) lift which must be compensated by additional lift from the main foil, thereby resulting in additional drag. To an extent, the two foils work against each other.

To minimize drag, the most efficient layout is a positive asymmetric main and rear foil (with the whole assembly moved slightly forward relative to the board to compensate for balance). This geometry minimizes the total amount of foil required to provide a specific amount of net lift.
.


At first sight, it looks like a Sword 1 ( probably 2 )

Image

The 3 new profiles (strut + Front W + Rear W) have been designed by Jean-Jacques DEBOICHET, a windsurf fin designer/manufacturer legend.

Claimed advantages:
- less wet surface = drag decrease = better efficiency = improved speed,
- stable despite surface sensing = higher flight height,
- foot placement for beginners is easier and more forgiving,
- water touch downs is also more forgiving reducing falls drastically.

The announced price is also a revolution (if bought in France):
- Foil in high modulous carbon: 999 euros (1275 USD)
- Board : 300 eur (380 USD) for the standard model (Fiber Glass Epoxy + PVC) , 800 eur (1020 USD) for the High Performance model.


More info in French from Patrice GUENOLE, brand founder and designer, here http://www.gongsup.com/forum/viewtopic.php?f=26&t=5871 use your favourite online translator :wink:

Quote:
Hello there,

GONG foils are being produced.

This foil is technologically ultra high end. This is to avoid any criticism on the quality.
For example, the mast is 100% in prepreg carbon with 64 layers !!! It is unbendable. It's really impressive.

We have worked at 3 persons of this foil:
- Jean Jacques Deboichet: windsurf fin shaper legend with a multitude of world titles to his credit.
- Christophe Bourrat: aeronautical test pilot with unusual theoretical skills and riding perception.
- myself: renowned cuisine Chef in the GONG asian butchery.

This diabolical skill association has lead us to provide a foil that combines very high performance with ease of use.
Let's be clear: the foil practice is difficult during the first sessions, regardless of the foil. However, we have brought solutions to some of the most recurrent problems:
- Our GONG foil has a high grip quality, particularly close to the surface. When flush with the surface, it does not stall unlike many foils. Unless you make a major mistake, it won’t stall. It's revolutionary because you can allow yourself higher and therefore faster rides. The profiles we have developed are incredibly stable.
- Our foil allows a balanced stance between both feet. Unlike many foils, the rear wing has a positive lift and not a negative one. One can therefore push on both feet and float with great comfort.

The target use range is 5 to 15 knots of wind. The goal is to have the most incredible performance in these light winds.
The GONG foil points upwind like mad, shows a ultra low low-end, and points downwind without difficulty. Performance in these winds are really incredible, especially the upwind.

We also have worked a lot on maneuverability. Maneuvers with a foil are often very complicated.
We wanted to simplify this aspect by moving the mast as forward as possible to free the tail during the curves.
We have also simplified maneuvers thanks to the profiles grip quality. As we rides very stable, we can curve with confidence, knowing that the foil will unlikely stall close to the surface or at low speed. We’re not riding on eggs, we’re confident.

Mounting the GONG foil includes:
- A deep tuttle on top of the mast. A windsurf standard, it's a box that we all know, simple to mount and fix if necessary. It also makes our foil usable on a windsurf board.
- A mini box inside the fuselage that allows a quick disassembly. With 4 screws you separate the foil from the board and the mast from the fuselage: the storage takes 2 minutes!!! This mini box will also allow your fuselages evolve as you wish in the future.
- A front wing box. Many foils have wing shimming concerns. We have solved this concern by setting a box in the fuselage and in the wing, so that the two fit together perfectly without setting.
- Ditto on the rear wing which includes an assembly ensuring a perfect alignment.
The GONG foil is ultra simple to mount and unmount while ensuring perfect axes. It's really functional.

The molds are made of “special” steel. They weight more than 400kg (900 lbs). I cannot bear the fuselage mold on my own !!!
We have a huge pression in the molds. The carbon fibers are ultra compressed, pure high modulus.
These molds of the highest quality have two advantages:
- They guarantee a total accuracy in the foil reproduction. Impossible to deform.
- They can bear several tons of pressure without deformation.
Only inconvenient: the tariff and handling: :o :o :o

Note that my shimming angles and the footprints are done directly during the molding process. Therefore we don’t have wing angle lags, which is not always the case everywhere.

Technical and technological choices we have made have been guided by our priorities:
1 / robustness 2 / rigidity.
We prefer loosing half a knot with a robust and ultra stiff foil rather than taking part in the extreme low-thickness race . Our mast is 13mm thick It’s a value that allows very high performance while maintaining a crazy stiffness.

Prices:
- The GONG foil is proposed at € 999 in 100% prepreg carbon ultra premium version.
- We offer a beginner board at € 300, made of Epoxy, fiberglass and PVC. An easy and cost effective shape.
- And we have a full carbon board for maximum performance at € 800 for a XTR finish with a race and narrow shape to switch the power horses on !!!

In short:
- 1299 € with an easy board
- 1799 € with a high performance board.

The GONG foil finish is mate as shown above:




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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Fri Oct 17, 2014 1:41 am 
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Nice product.

Hate to say it but Listerfoil has had positive lift on both foils from day 1 :wink:


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Fri Oct 17, 2014 2:28 am 
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Doesn't it all just depend on angle of attack anyway, so any foil can be creating positive or negative lift?

Is this just saying that the angle of neutral lift is the same for the forward and aft foils, whereas on most foils the aft foil is 1 or 2 degrees off from the front foil?

What angle of attack is a typical foil at when riding along at cruising speed?


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Fri Oct 17, 2014 10:44 am 
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In the UK GONG doesn't have the greatest reputation

Mainly because of taking money for SUP boards and never delivering.....

Things might be different now, I do hope so.

But seriously I know it's a foreign language but if your going to write a press release do better than phrases like

"Special" steel... Really? Word is special about it?

Crazy stiff... Wow I just wanted stiff but if I can have crazy stiff I will buy a dozen!

It all reads like it was written by Mr C

Totally happy to be proved wrong!


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Fri Oct 17, 2014 12:15 pm 
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Location: Australia
he has a sense of humour

"We have worked at 3 persons of this foil:
- Jean Jacques Deboichet: windsurf fin shaper legend with a multitude of world titles to his credit.
- Christophe Bourrat: aeronautical test pilot with unusual theoretical skills and riding perception.
- myself: renowned cuisine Chef in the GONG asian butchery."


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Fri Oct 17, 2014 5:00 pm 
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Joined: Wed Mar 01, 2006 7:51 pm
Posts: 294
james wrote:
Totally happy to be proved wrong!


I've been following this guy for a couple of years now. I have never been disappointed.

I have no pretention or financial interest in sharing this news.
As Google translate was useless on this post taken from the GONG forum, I took 30 minutes to try to make him understandable and visible to the largest audience. It's not perfect and it wasn't intended to.

I really liked his approach to kitefoiling with 70m lines in sub 6 knots last June on a Sword 1 - demonstrated with videos - I just thought his own kitefoil design should diserve some focus on Kiteforum.

Patrice GUENOLE isn't just copying and pasting !
He seems to be bringing new things to the sport in terms of design, manufacturing, ease of use, performance and tariffs :o
If the guy says the strut is really stiff, I trust his perception.

As soon as available, I will update my post dedicated to the 5kg bending and torsional stiffness results with the GONG figures.

wdric wrote:
he has a sense of humour
...
- myself: renowned cuisine Chef in the GONG asian butchery."


I confirm, he has an interesting sense of humour in his posts which is not always easy to translate into English.
Board then kite and now kitefoil fine tuner !

So let's wait and see if GONG "s KBHF will set a new trend and be copied in 2015 !

My 2 cents.


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Sun Oct 19, 2014 8:03 pm 
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davesails7 wrote:
Doesn't it all just depend on angle of attack anyway, so any foil can be creating positive or negative lift?

Is this just saying that the angle of neutral lift is the same for the forward and aft foils, whereas on most foils the aft foil is 1 or 2 degrees off from the front foil?

What angle of attack is a typical foil at when riding along at cruising speed?


Yes I would like to know this as well and to be more specific say epp 817. :?:

I now know from Hawaii that said epp 817 is already at 4° positive if centerline is level so how much more to get us flying knowing that there are TON of variables (thanx PF) just an aproximate A O A would be nice.
I have my thoughts from side flying photos but do not want to say yet to not influience others.
Any takers? :?:


It would seem to me that if your attachments are all 90° and your F wing is centerline level with the tail of your board that a side photo knowing the H20 is level should provide the answer, taking into account the R wings smalll influence.

I am most interested in this because the limiting factor I feel for ultra low wind take offs is board speed, so we need as little friction under and on the water as possible!
So does it not make sense to have both wings at 0° lift when the board is level for the least drag?
R H


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Sun Oct 19, 2014 8:50 pm 
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As H so noted this is made in China, I just read this from the owner.
I really hope I get to see and test fly one soon as his claims are lofty.
R H


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Mon Oct 20, 2014 6:52 am 
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davesails7 wrote:
Doesn't it all just depend on angle of attack anyway, so any foil can be creating positive or negative lift?

Yes, but if an "inverted" asymmetrical foil operates at a sufficient angle of attack to produce positive lift, then it will produce excessive drag; very poor L/D ratio. It's not designed to normally operate that way.


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 Post subject: Re: Gong Hellvator - 1rst KBHF with both foils providng pos
PostPosted: Mon Oct 20, 2014 9:53 pm 
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Joined: Fri Nov 05, 2004 1:13 pm
Posts: 250
Location: France
I have no affiliation with GONG. They have a rather good reputation in France, I think that this stuff is serious, not another C.., for sure. Did not try their foil yet.
Do not get disturbed by the syntax errors, the French usually don't speak English well and they just don't care.


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