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Low Wind Fish Design Feeback

here you can exchange your experience and datas about your home build boards


slightlyimperfect
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Local Beach: Slave Lake
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Low Wind Fish Design Feeback

Postby slightlyimperfect » Sun Nov 07, 2010 3:09 am

Im designing a kitesurf board to build and would like some feedback as I have never used a directional before.

Im looking to build a light wind board and one that will be use in small chop. (6ft2" 170 pounds, 10-15 knots)

This is what I have come up with so far.

6ft long
21" wide
tail width 10"
thruster fins
2 1/4 thick
double concave of 8 mm
next to no tail rocker, maybe 1/4"
perhaps slight rocker on rear board top to give slight kick feel for back foot


Volume - 35 Litres, 99 beers
Rails - unsure

Whatcha think?
Attachments
boardspecs.jpg
Low Wind Fish Version 1.0

zmax
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Joined: Thu Apr 15, 2010 10:51 pm
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Local Beach: Belmont Shores
Style: Freeride
Gear: North rebel '09 14m or 9m
homemade surfboard and twintip
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Re: Low Wind Fish Design Feeback

Postby zmax » Sun Nov 07, 2010 3:47 am

Looks pretty good. You might consider a tail rocker, as it will make it a little easier to turn. Might be a little stiff to turn with that wide of a tail , thruster fin set-up, and no tail rocker.
Is this going to be purely a light wind board or do you want to use it in surf also?
If just want a light wind, I'd consider going with the race board style design. They are great in light wind and go up wind great.
If your going to use this board for light wind days, and surf then I stick pretty close to surfboard specs. and just reduce tail and nose rocker for better light wind performance.
Check out different surfboard blanks to get an idea of surfboard rockers. The fish blanks are designed with less rocker.
http://surfblanksamerica.com/

zmax
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Posts: 42
Joined: Thu Apr 15, 2010 10:51 pm
Kiting since: 0
Local Beach: Belmont Shores
Style: Freeride
Gear: North rebel '09 14m or 9m
homemade surfboard and twintip
Brand Affiliation: None

Re: Low Wind Fish Design Feeback

Postby zmax » Sun Nov 07, 2010 3:54 am

You might also want to check out www.swaylocks.com. Endless amount of info on building surfboards. Good luck, and remember to have fun with it. Even if it doesn't come out professional looking it will still work, and that fact that you built it, will make it that much better.

slightlyimperfect
Medium Poster
Posts: 145
Joined: Thu Dec 07, 2006 7:04 pm
Kiting since: 2007
Local Beach: Slave Lake
Gear: Ocean Rodeo Rise
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Location: Slave Lake, AB Canada

Re: Low Wind Fish Design Feeback

Postby slightlyimperfect » Sun Nov 07, 2010 3:58 am

The board will be used predominantly for light wind but also in small chop waves up to 2-3 ft.
They are smaller wind driven lake waves.

I have heard that tail rocker eats up your low wind effiency, but perhaps a little could be added as well as a narrower tail. Perhaps 8 pr 9"?

thanks for your feedback, I appreciate it! :D I'll take a look at that site to.

zfennell
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Re: Low Wind Fish Design Feeback

Postby zfennell » Sun Nov 07, 2010 2:02 pm

another vote for swaylocks.
especially if you want it for surfing.

but as zmax has suggested, light wind surfing and light wind chop may have different design considerations that contradict each other.

i.e. the toe-in angle for thruster fins is good for extracting energy while riding the face of a wave.
but it's likely to be just extra drag when going straight on flat water.

you are correct about flat bottoms being the first to plane.
good for the absolute bottom end in flat water.
but waves are not flat.
even if you dont want to turn on one.

if you are looking for max speed in light wind, i think you'll find that flat bottoms are also the first to hit the wall. Excess flat limits your ability to reduce excess surface area as speed increases.
i think if you look at race directionals or formula windsurfers, you'll see signs of rocker from front to back. more in the front, continuous but decreasing to almost flat in the back.
the amout of real flat will depend on the "minimum" amount of area you think you need for top end and where you plan to stand while trimmed out.

cosmetically, the tail looks too thick,
structurally, once you have enough meat for the fins, thickness doesn't buy you much.
overall, volume is good if you think you need to suppliment the energy from the wave or the kite.
but surface area is a better way to create and control lift.
make it strongh enough for the job and if thickness is needed to help structurally, so be it.
otherwise, it may get in the way.

just the thoughts of someone who has never made anything spectacular.
but a bunch of iterations in plywood have me agreeing with Zmax again.
dont worry too much, cause in the end, everything works.

have fun,
-bill

slightlyimperfect
Medium Poster
Posts: 145
Joined: Thu Dec 07, 2006 7:04 pm
Kiting since: 2007
Local Beach: Slave Lake
Gear: Ocean Rodeo Rise
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Location: Slave Lake, AB Canada

Re: Low Wind Fish Design Feeback

Postby slightlyimperfect » Sun Nov 07, 2010 10:51 pm

Thanks for your feedback.

It makes sense that Waves and light wind are not the same and almost a contradiction.
I do not want a flat race board tho. So I guess I want more of a surfboard with some rocker.
In this newer version, I added some tail rocker, but also an inch on width. My thought is that the rocker will hurt it's low wind strength, but the width will help it out. Im not worried about being overpowered on it and because of its width not being able to keep it down, as it will be used mostly in light winds.

Here is another version of the board with some changes. changes in bold

6ft long
22" wide
tail width 10"
thruster fins
2 1/4 thick
double concave of 8 mm
tail rocker, 1 1/2"
perhaps slight rocker on rear board top to give slight kick feel for back foot


Volume - 35 Litres, 99 beers
Rails - unsure
Attachments
boardspecs1.5.jpg
Low Wind Fish v1.5

zfennell
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Location: rhode island

Re: Low Wind Fish Design Feeback

Postby zfennell » Mon Nov 08, 2010 12:54 pm

slightlyimperfect wrote:
Volume - 35 Litres, 99 beers
Rails - unsure


i like it.
the planform template (top view) is very smooth in the nose area.
the 'bit of hip' at 1ft off the tail would look nicer if the curvature was a smoother in this area.
perhaps pull in the width here just enough to make the curvature smooth and continuous.
dont let me talk you out of it if you did this intentionally. its just my personal taste.

regarding the rails:
the profile you've shown is a good start for the mid section.
traditionally folks seem to start with 50/50 round rails in the front.
as you move aft the wide point moves lower in the profile to form a bit of tuck with a sharp release edge ( like your pic)
at the tail , widest part of the profile moves to the bottom, no more tuck, just sharp edge.

overall, in light of the boards width, i would thin the rails a bit by removing material from the deck side,
but opinions will vary.this is one aspect where you can search for 1000s of different rail designs on swaylocks.

the post below is a bit off topic, but you'll be asking yourself soon enough.
http://www2.swaylocks.com/node/1018545

no worries,
-bill

slightlyimperfect
Medium Poster
Posts: 145
Joined: Thu Dec 07, 2006 7:04 pm
Kiting since: 2007
Local Beach: Slave Lake
Gear: Ocean Rodeo Rise
Brand Affiliation: None
Location: Slave Lake, AB Canada

Re: Low Wind Fish Design Feeback

Postby slightlyimperfect » Tue Nov 09, 2010 6:00 am

Thanks for the tips and the help with the rails. I will definitely implement your suggestions.

I'm going to start work soon and will update this thread with photos.


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