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Converting carbon bar(s) to fuselage (was: AoA split)

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tegirinenashi
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Converting carbon bar(s) to fuselage (was: AoA split)

Postby tegirinenashi » Mon Oct 23, 2017 12:02 am

I'm making a fuselage from 2 former Naish carbon bars and wonder what angle of attacks should be for front wing and stab relative to fuselage. Delta hydrofoil video says the angle between wing and stab is the best around 3 degrees, but how does this number is split between each wing and the fuselage? I assume the fuselage moving below the water surface at an angle would create more drag than necessary.

The two wing sets I'm planning to use are
1. LF Rocket
2. JNJ (from aliexpress)
LF Rocket setup is no brainer, because their aluminum fuselage is a plane surface. Therefore, I just mount LF wings as they were in the original LF setup. On the other hand, JNJ is trickier because the fuse is curved. I've measured AoA for the front wing and was surprised to see that it is negative 1.5 degrees! My expectation is for the front wing be at zero (or perhaps slightly positive) angle relative to the fuselage, thus providing the lift, and stabilizer being at 0 degrees. This idea is consistent with what I have measured for LF Rocket: 0 degrees for the front wing and 0 degrees for the stab. On the other hand, everybody says that stab provides negative lift (and therefore must be at negative angle). Therefore, to repeat my question, what are the canonical numbers for the front wing and stab AoA (relative to the fuselage)?
Last edited by tegirinenashi on Tue Oct 24, 2017 11:11 pm, edited 2 times in total.

bacon2109
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Re: AoA split

Postby bacon2109 » Mon Oct 23, 2017 3:02 am

all in the coefficent of lift (CL) of the selection of wings ( front and stab ) vs speed bandwith
the front wing may have a AoA of 0 degree on the Rocket if the mesurement is read on it intrados flat surface in regard of the profile
most of the foil have(around) 1/3 of the front wing area for the stab as a thumb rule. So the profile is upside down for the stab.
Experimented like this to ease the feedback of the rider on the foil.

---Getting overboard here. go with the KISS method (kept it simple s...)

keep using 0 degree of AoA on the front wing and make ajustement on the stab.
I made my foil + board,
front wing at 0 degree, stab at -1,6 degree as a start, simple flat intrados profile for hi lift, low speed (less then 25knt, i suppose) ,
tryed it, made it try to a good foil rider to understand and have a different feedback.
Had to change mast position by 4inch back to finally not rodeo on it.
Can't write more, out of my ligue, still learning.

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tegirinenashi
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Posts: 499
Joined: Wed Aug 27, 2014 3:29 am
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Local Beach: 3rd Ave
Gear: Cabrinha CO2 9.5m, Naish x2 14m, Litewave 161
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Re: AoA split

Postby tegirinenashi » Mon Oct 23, 2017 10:05 pm

0 degrees for the front wing it is, thank you very much.

In case if people are wondering why this DYI project, let me post some photos. For the reference, LF carbon fuselage weights 510 g -- I'm not sure how they manage to get their products consistently overweight.

3 Naish bars go in:
raw materials.png
2 fuselages go out (WIP):
wip.png

Mikey
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Re: AoA split

Postby Mikey » Tue Oct 24, 2017 11:02 am

Construction technique ??

User avatar
tegirinenashi
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Posts: 499
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Local Beach: 3rd Ave
Gear: Cabrinha CO2 9.5m, Naish x2 14m, Litewave 161
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Re: AoA split

Postby tegirinenashi » Tue Oct 24, 2017 5:39 pm

Mikey wrote:
Tue Oct 24, 2017 11:02 am
Construction technique ??
The bar itself is a solid platform for a fuse, except it's little short.

Recipe:

Take 3 Naish bars circa 2004. Split one bar into the halves. Notice the bar ends opening diameter. It fits perfectly inner plastic tube from standard pump. A lighter and more rigid option is 16 mm diameter carbon tube. The major assembly step is covering the tube with epoxy and thrusting it into the bar and bar half. The first picture shows one bar after this step, and the other bar parts above it. The assembly is quite rigid by itself, but the final step is wrapping the shaped fuse into carbon sleeve adding more rigidity. The second picture shows a nose of one fuselage wrapped into a portion of the sleeve -- I'm still shaping both fuses, therefore no final wrap yet.

P.S. I'm not sure how common carbon bars are these days. Cabrinha from 2007 is alum, and I would suspect many with alum openings are alum tubes. On another afterthought, perhaps starting with 10-15 mm carbon tube of sufficient length and then wrapping it with layers of carbon strip is more straightforward project.


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