DIY Home Made wooden Hydrofoil fins

[don pitcher]

You are amazing! Thanks for sharing.


I found this interesting.

http://www.offshorespars.com/store/airf ... er-tubing/

[Hawaiis]

You are amazing! Thanks for sharing.


I found this interesting.

http://www.offshorespars.com/store/airf ... er-tubing/

They did not provide the "T" dimension or the foil shape.
If it look any thing like their picture, it would have too much drag.

[don pitcher]

The T dimension is further down the webpage. Yes, it looks to have too much drag, but maybe they could offer another airfoil for a "reasonable" price?

[windfreak74]

hello hawaiis,
Do you think the board makes a diference?
ive seen your video with the wooden board and found it awesome!
what is more importante board size or keel location?
do you use a specific distance from the back of the board for positioning the front wing?
what would be the ideal location for the keel?
thanks
Pedro

[Bigdog]

All I can say this is an awesome thread. I am blown away with hawais wooden foil that works well and does not break. Could work H!

[don pitcher]

I agree. Well done.

This looks interesting.

http://www.rigrite.com/Spars/Kenyon_Spa ... rfoil.html

http://www.rigrite.com/Spars/MetalMast_ ... tions.html

[Hawaiis]

hello hawaiis,
Do you think the board makes a diference?
ive seen your video with the wooden board and found it awesome!
what is more importante board size or keel location?
do you use a specific distance from the back of the board for positioning the front wing?
what would be the ideal location for the keel?
thanks
Pedro

Any board that will float should work, in the beginning, you may want to start with a 5' to 6' surfboard.
The location of the Strut is very important.
Since you have a foil shape possibly with some positive lift, you might want to mount it where your rear foot position is.
Most of my wings are flat plates with zero positive lift, I will need to position my strut further forward.
Where you mount your straps will determine how well it rides too.
Carafino is the bench mark, the board is 4.5 foot long, the center of the strut is about 16 inches from the center of the board. It is more balanced than the MHL lift, which I think has a too forward stance.

[Hawaiis]

The T dimension is further down the webpage. Yes, it looks to have too much drag, but maybe they could offer another airfoil for a "reasonable" price?

Sorry my iphone could not show the bottom of the page. $450 is too much for a compromising foil.
if it is Eppler 837, I would buy it.

[zfennell]

The T dimension is further down the webpage. Yes, it looks to have too much drag, but maybe they could offer another airfoil for a "reasonable" price?

hey don,
your search is making progress.

i agree with the collective guess on drag.
but now you guys have the tools to make educated decisions
use ronnies ref
(https://www.grc.nasa.gov/www/K-12/FoilSim/index.html)

to calculate a real number to see what the penalty may really be.

the low drag guys are using chord length of 4" and area that is 70% larger than the 2.25 "offshore" spreader section. you can afford a 70% increase in drag coeff to make the problem a 'wash'
yes/no?


plus: the offshore guys and rigrite have added another number that will help your search.
area moment of inertia ( about the chord length): Ixx
the BC awning choice had Ixx= .015, which was a bit marginal
I think if you find a section with Ixx= .02 or greater you will be able to do this with aluminum.

the small offshore carbon spar lists Ixx=.025 with modulus 50% better than alum. (15ee+06psi)
structurally its a good choice.
keep lookin for those numbers
-bill

[Bille]

...
Sorry my iphone could not show the bottom of the page. $450 is too much for a compromising foil.
if it is Eppler 837, I would buy it.

The offshore one closest to 100mm , is 4", and it's 1.1" thick ; that
works out to a 27.5% thick airfoil. That is WAY too proportionally thick for
the cord length. The Eppler 837 is only 16.1% thick, and would be Easy to build strong.

The 27.5% thickness isn't what bothers me most for the profile
on the offshore one ; it;s that rounded Trailing edge that's a Deal-Breaker !!
If the TE was flat, with sharp corners, it would produce less drag than
a round one.

I wonder if a guy wouldn't be better off trying to find a wood-working shop, that
could make a wooden one from a suitable tree with the E 837 airfoil; then it
could be stiffened up for under $40. Some people don't like the messy composites, but
they make that pultruded carbon rod, that can be placed in a groove made by a
router, and glued in with ease ; take maybe a few hours to do the job, if you didn't
need to do your own shaping.

Bille

Here is a question :
Say you set up a router to cut the E837 foil with a jig, from 2" X 6" stock ---
Would you cut a pass or two on one side, then alternate cuts
to the opposite side to keep the shaft from warping ; or is that
not going to be a problem ?