Foil Progress

Thought I'd post some photos of my foil progress, I think I'm entering the home straight!  Conveniently, we're also at the start of our summer windy season here.

Thanks to Franck for the basic design info and to Chris and JMB11 for the useful advice.

I had a question regarding placement of the mast on the board - I've currently been thinking to put it with the centre of lift of the front wing (1/4 back from leading edge?) at the centre point between the footpads?  What has been found to be a good position?

The mast and fuselage came out really well and feels pretty stiff.  Light it is not - almost solid carbon.

Cheers
Mark

Very nice!!! Looks similar with the Taaroa Sword.

Very good job...

in one shoot:bball: 
You do better than me for sure
You only have to copie the SWORD position on a board
The rear holes are at about 20cm from the back of the board
You can find so many pictures of the SWORD;that it's impossible to miss it:lol: 
VERY VERY nice
Happy to see such improvement

If you need more pictures just ask ;-))

Hi Guys

Thanks very much for the kind and encouraging words.

I've had three testing sessions so far, 1st one in terrible gusty, light wind: found the lift to be uncontrollable and got thrown off immediately. Second session in better wind with some shimming in the wings to reduce the lift, which went marginally better but still too much lift.

After this I chopped about 30mm off the ends of the main wing (main wing reduced from 650cm^2 down to about 580cm^2 projected area) and a bit off the stab, and sanded the extra profile thickness of the main wind down to the design values. Also moved the footstraps forward and spent some time reading the learning section of the forum  - which opened my eyes to what I was doing wrong!

The last session yesterday was in good conditions - pretty strong at about 20-22 knots with an 8 m kite, I finally felt like things might be coming together - I was managing short runs instead of crashing immediately, and sometimes managing to correct before crashing, also to sort of "skim" just on the water but not completely out (if that makes sense?). On the plane, it was still pretty hard to try and ride a bit off the wind - any attempt to control speed by pointing upwind just ended in the foil climbing out and ejecting me

I still think I've got too much lift so I have a couple of ideas I'd appreciate any advice out there on:

1. Reduce the angle of attack on the front wing (shim the front of the wing-according to the polar for the eppler 817 foil, the zero lift line is at about -3 degrees if I understand the graph correctly)
2. Reduce the negative angle of attack on the stab (shim the front of the rear wing - with a design value of about -2 degrees. The stab wing is mounted on top of fuselage )
3. Cut off a piece of material off the ends of the front wing and reduce the lift area.
4. Sand the top of the front wing surface thinner.
5. I was wondering if rounding the front leading edge on the main wing a bit (as opposed to a fairly sharp point might assist with making the foil less "on/off" and more progressive.

As usual any help is much appreciated!

2 degré négatif on the stab can be enough
Make the leading edge of your front wing more( """round"""not to sharped)
0 degré for the front wing
question:profil of the fins????????????????????????????????

Thanks Franck

I'll attach the "design" profiles I used at the - both are Eppler 817. The stabiliser wing came out very close to design, the front wing came out too thick, so when I sanded it may not agree completely with the profile.

I'll take your advice and round off the leading edge a bit.

Nice - looks extremely sweet. For certain, the SA of the front wing can be smaller than 58cm2 but its always a trade off between early take off or having to go much quicker to get foiling… Plus if you chop your foil down in size any more, in the early stages of learning to foil it rests unstable until you are really moving at let's say 16 to 18knts and that results in having to make your gybes and tacks at a certain speed which is more than challenging to say the least.

Before cuting and modifying anything you first have to find the right adjustment of the stab.
The problem is that adjustment is easy to do for an experimented foiler. You are beginning I guess ?

Can't you find somebody to adjust your stab first ? 2° are a lot, sometimes it is way less.

Good point Laurent - so here goes a quick explanation.

Get an old Coke or Pepsi bottle and a Squeezy Liquid bottle cut them up and using the flat plastic make some shims that you can fit under the rear bolt of the back wing. If you drill each shim you can put it into position and the bolt will then hold it in place ;-)

You use coke and or squeeze bottles as the plastic varies in thickness - guitar plectrums are an alternative but obviously more costly.

Then simply add or subtract the shims to make it a smoother ride - it's really not that complicated but on the beach it's easier if you have someone helping you as changing the shim whilst flying your kite is a bit of a nightmare - doable but dangerous.

Best of luck - it's a bit tedious but worth spending the time to do it as it can change the ride characteristics of your foil considerably.

chris_middleton a écrit:

... that you can fit under the rear bolt of the back wing.

I am a bit confused. Could you all confirm this ?
- front leg aching to compensate front wing going out of the water = too much lift > give positive angle to the back wing > fit a shrim under the rear bolt of the back wing
- back leg aching to compensate front wing going down into the water = not enough lift > give negative angle to the back wing > fit a shrim under the front bolt of the back wing

dépend if the stab is over or under the fuselage
In this case the shrim under the rear bolt of the back wing for a négative angle

Yes Frank - I was speaking specifically about this foil ;-)

Hi Mark.

Not easy for me to appreciate the mast profil at your two joined pictures. It seems to be "short" with a long plane surface at the rear edge. Is this the case?

an old topic from 2008 originaly in english for you !

https://kitefoil.forumactif.org/t128-regler-l-incidence-de-l-aileron-arriere?highlight=r%C3%A9gler#597

franckite24 a écrit:

dépend if the stab is over or under the fuselage
In this case the shrim under the rear bolt of the back wing for a négative angle

Thanks. I thought about it later but too late....  

Laurent, your post refers to a rear wing placed under the fuselage.
After a small corection due to rear wing over it, tinyE summarizes it nicely:

"For the rear wing, the closer the shiming to the strut, the "less" lift."

tinyE could have written for a foil with rear wing \"above" fuselage a écrit:

If you shim in the front of the rear wing (place the shim between the fuselage and the rear wing and screw it down tight), it will increase reduce the lift to the ski. If you place the shim between the fuselage and the trailing edge of the rear wing, it will reduce increase lift. BY moving the shim further towards the vertical strut, you increase reduce the effect the shim will have [on the lift of your hydrofoil Ed].

Hi Guys

Thank you all for the advice. Laurent as you guessed I'm a beginner - 13 years kiting, but never even seen a foil in the flesh, so any knowledge I can gain is like gold to me.

I'll take the advice to heart and see if I can tune the wing angles (and train the operator!) before I start chopping bits off.

I'll be sure to report back after my next test.

Cheers
Mark

phezulu1 a écrit:

Laurent as you guessed I'm a beginner - 13 years kiting, but never even seen a foil in the flesh, so any knowledge I can gain is like gold to me.

I'll take the advice to heart and see if I can tune the wing angles (and train the operator!) before I start chopping bits off.

I'll be sure to report back after my next test.

I have just added the possibility to write your kitesurf and or foil experience in your profile, it will help members to discuss

I have found one topic I have written not long ago in french for the stab adjustment. No time to translate it today but will do it later if no one is willing to translate it.

https://kitefoil.forumactif.org/t1560-calage-du-stabilisateur

Voici un aide-mémoire pour caler son stabilisateur (aile arrière du foil) correctement et comprendre les conséquences des modifications de réglages.


Attention à bien saisir l'influence du calage du stab selon qu'il est monté au-dessus ou en dessous du fuselage car l'effet d'une cale est inverse.

Stab monté sur le fuselage: si tu mets une cale à l'arrière, tu augmentes la portance du stab donc ton foil tend à plonger de l'arrière et donc à sortir de l'eau de l'avant et il faudra avancer sur la board pour compenser.
Stab monté sous le fuselage: si tu mets une cale à l'arrière, tu diminues la portance du stab donc ton foil tend à remonter de l'arrière et plonger du nez et il faudra reculer sur la board.

Hi Guys

I thought I'd add a quick addition to the above posts: I've probably had about 7 sessions now, lot's of crashes, but I think I've got it! Managing runs of about 500m and loving it, it's an awesome feeling and I'm hooked. Need to work on turning and how to go faster and then work on the MKII version!

Thanks once again to everyone for the information on this forum and the help and advice I received.

Cheers
Mark