Le dernier Proto KT7

Un petit flash de mon dernier proto - le KT7.
Pas mal d'avance sur les derniers protos avec un niveau de stabilitie et glisse très agréable.
La temperature ce n'est pas très convivial pour le testing en ce moment mais je vous tiens au courant quand le clima deviens un petit peu plus chaud...

Le KT8 a marché tout de suite - premiere bours avec Marc Blanc (thanks dude) un petit peu de rgalage a faire et re-essaye.

hello chris, hello foil-dudes

our foils seem to get more and more alike. here is the one I used in la ciotat:

foilgaz V2


best regards
mario

Hi Mario, yes remarkably so except you have anheadral and my wings are flat (diheadral in fact). However, it's super stable but gybes over a wide arc which at this point I'm not certain how to remedy. Zeeko Nico tells me it rides AOK but I'd like it to be more playfull / manouverable.

Franky suggested adding some anheadral too but I'm not overly convinced that is the way forward - I'm on the plane of less = more in terms of drag.

Yippieeee!! I made it!!! Thanx Chris!

My frontfoil has about 8cm anhedral and is 60cm wide. It jibes with a nice radius. But my goal why i made it anhedral was actually -less drag and more stability in jibing. My thoughts:
less induced drag because of a actually wider wing (64cm)
more stability during a turn because the AoA is lower at the tip as at the root of the wing (little "flow demolition")

Le design est propre en tout cas!

les aileron avants plats ou avec peu de dièdre ou ne disposant pas de winglets(plus ou moins marqués) posent incontestablement des soucis de stabilité en lacet et de maniabilité en courbe
Ceci peu etre compensé comme beaucoup le font par des ailerons de queue verticaux ajoutant ainsi de la trainée
On gagne d'un coté ;on perd de l'autre;ceci n'est pas très important si on ne veut pas battre des records
Les ailerons plats sont tellement + simples a fabriquer
Par contre je pense qu'il est très très dommage d'avoir un foil qui jibe mal ou trop ou qui coule dès que la vitesse baisse;c'est un tel pied de se faire de belles courbes avec de l'angle

Hello all,
After I read this I feel I should relay maybe a unique interesting experience.
3 years ago I rode 4mm thick aircraft aluminum wings with only the leading and trailing edges profiled.
As I foiled in mostly gusty strong tram they were good, slow and stable.
They both had curve, down,anhedral, measuring about 6cm at center if tips on flat surface.
After many, many,many sessions they began to bend, when they first started I noticed IMMEDIATELY!
Only because I had seen an Italian foil with flat wings I decided to bend mine flat to test.

Remember these are the same wings, once curved, then made almost perfectly flat!
It must be said they were low aspect ratio with basically flat profiles.

WOW .. not stable in pitch, roll or yaw .... as hydrofoils fly I use known flying terms.
Needless to say I did not use them any more! and I knew these wings WELL!

BUT;

many airplanes have dihedral and flat wings ,but they use flaps.

sharks, whales and dolphins seem to have anhedral pectoral fins, wings.

The mentioned Italian foil seems to work if one sees the web site, or the guy is one hell of a talent, big jumps, "no board foil".

Without judgement I simply relay my findings for consideration.

David

Interesting indeed!

Sam, do you have any pictures?

Here are photos of said wings;





Sorry I do not have after bending flat pictures.

Note low aspect ratio and rear wing also curved down.
But I must say I flew with this setup a lot.
I still think lower aspect ratio wings are easier to learn with and maybe better in super gusty strong wind, and maybe waves?
chow

So simple! I think I am going to make a foil like that. Is it just flat aluminium plate with the ends rounded off and then bent?

I am looking for aluminium aero foiled hang-glider down tubes for the mast. I think it will be stiff enough.

Hello,
If you choose to make alu wings I suggest no thinner than 5mm, and that is aircraft quality!
And for a level of performance it needs to be profiled, PRO FILED to a proper shape.
And experience done, it is hard to stick epoxy, vynlester or polyester to alu without first "preping it with chemicals!
You think it has good adhesion but after time and ANY flex ,even large temperature changes,bingo delamination!
I therefore would not choose alu for wings or strut, fuselage , for that matter forget alu in foil building.
Unless... you can tig weld and have the proper chemicals and know how to prep for sticking anything.
Go ahead and win the lottery so you can buy one made by guys with loads of experience and testing time in!
Or learn to use composites wearing masks, glasses gloves!!
I looked into already made alu airfoils for foil use, never found one thin enough.
chow
see frankite posts for great foil making info!!

Thanks for the info. I have made a foil before, but it is at the bottom of the dam! I am still happy with my MHL foil, but I also like to experiment and am looking for any ideas to start making foils easily.

Hi Christoff,

in the early days, 2008 I started with MDF and cabon skinned and then went onto Aluminum wings. I've found Helicopter rotor profiles to use as the vertical section but they are ridiculously expensive and you have to purchase the hole length !!! 3K - 4K $$$.

If you use alu for the wings I opted for 8mm - it's a pain to shape but it works and as David stated providing the LE is nicely formed and the TE is shaped correctly the foils will provide a certain level of 'glisse' as they say in French.

I experimented with 4mm sheet for the rear wing but.... it always bends eventually. The very first rear wings that I used on the Carafino with wingtips back in 2008 were made from this flat sheet at Serre Ponçon. Mind you the TE were like razor blades and I'm surprised that neither Nico or myself did not sustain serious injuries from them.

If you want some Alu sheet - just drop me a PM I've got quite a bit left.

Citation :

les aileron avants plats ou avec peu de dièdre ou ne disposant pas de winglets(plus ou moins marqués) posent incontestablement des soucis de stabilité en lacet et de maniabilité en courbe

Par contre je pense qu'il est très très dommage d'avoir un foil qui jibe mal ou trop ou qui coule dès que la vitesse baisse;c'est un tel pied de se faire de belles courbes avec de l'angle

Hi Franc - demand à Marc B comment il a trouvé mon KT7 - il etait ettonait par le stabilité par contre tu as raison, le jibe ce n'est pas facile et c'est toujours ' a thorn in the side' pour moi (excusé moi pour le melange d'anglais / français). C'est sur que il y a plusure façon à pélé le poule (skin the chicken) mais quand tu as un super niveau de glisse avec les ailes plat - j'ai un peu de mal d'abondoner quelque chose qui marche bien.

as usual
On aime toujours son bébé

ça est sur et cértain Franky.

Mais on a besoin de 'let go' de toutes les choses qu'on aimes bien 'connaissance du foil' pour bien trouver les nouveaux chemins du plaisir (and yes I am talking about the foil.... :-) un petit peut d'humour anglais evidement.