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Micro-simmons-spoon-twin-keel-paipo/kneeboard thingy!
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surffoils



Joined: 12 May 2007
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Location: Gold Coast, (finally), Australia

PostPosted: Thu Mar 03, 2011 3:50 am    Post subject: Reply with quote

Those pics show what a nice shape you got going there ! Lovin it.
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global ernie



Joined: 09 Oct 2008
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Location: northern nsw

PostPosted: Thu Mar 03, 2011 5:14 am    Post subject: frank zappa: its a fillmore isnt it, futuristic i dig the... Reply with quote

that just looks fast, do you think you could reduce the fin size further? i think simmons was quoted that the faster your going the less fin size you need. what is the toe in and cant angles? have you surfed a finless version of this board? and how deep is the concave and how far does it run up into the board? 500 words or less or we could discuss it over 3 million beers!
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kid



Joined: 11 Jan 2010
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Location: Bells Beach

PostPosted: Thu Mar 03, 2011 6:18 am    Post subject: Reply with quote

DISCUSS OVER BEERS!!!!! Ok, I have a beer, so....Yes I reckon the fins could be smaller. I recall from "Jonathan Livingstone Seagull", that wings, and thusly fins, have a greater effect at a higher speed, thereforely, I might find that as the board moves faster (due to the lower drag from smaller fins) the fins might be just as, if not more effective, if smaller, but with a deeper foil. The concave is only 15mm deep, and runs up about a third of the board length from the tail. The fins have no cant, but they are toed in to a point around 6 inches past the nose of the board, on the virtual centre line. I am torn now between making another, slightly longer and wider version, or just cutting the fins off this one entirely to see how it works. My guess is that it will still be fast, but that the vertical hold will be compromised somewhat! Thoughts?
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global ernie



Joined: 09 Oct 2008
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Location: northern nsw

PostPosted: Thu Mar 03, 2011 7:10 am    Post subject: Reply with quote

I would rather a bottle in front of me than a frontal lobotomy.
have you considered installing FCS style plugs, there is a generic brand on the market now, much cheaper and as good a quality. nor a great puzzle to fit them into a solid timber/ply board but you would have to glue some blocks on the deck (rounded/smoothed down unless your a masochist) to give enough depth for the engineering specs. FCS is a pretty straight forward installation, you can use polyester or epoxy. the tooling cost is not to expensive if you already own a good electric drill.
there are some finmakers that will do fibreglass fins to fit FCS. dont quote me but i think fluid foils at ballina might, you can send him some templates and money and he will knock em up for you. this system would enable you to do some mix and match R&D. i could film a vid of a thruster or quad installation if you like and post it to you or you might know a local board builder who could take you through the process.
send me a pm if you like and i will get you the toolings specs and fill you in on the nuances if required.
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Uncle Grumpy



Joined: 15 Jan 2007
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Location: San Clemente

PostPosted: Thu Mar 03, 2011 10:54 am    Post subject: Reply with quote

Quote:
i think simmons was quoted that the faster your going the less fin size you need.

For Bob Simmons, surfing was about down the line speed. Turning was secondary.
I've seen original Simmons boards that are 8'-10' long with fins the size of those on Kid's board in this thread.
A friend of mine rides a Simmons(ish) wide tailed longboard with a keel fin of his design that is about a one foot long at the base but only an inch or so high and he raves about it.
Somethin' to think about. Wink
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ccsurf



Joined: 11 Feb 2011
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PostPosted: Tue Mar 08, 2011 11:51 am    Post subject: Reply with quote

Did you take this thing out yet? how did it go?
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puurri



Joined: 26 Oct 2009
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Location: sydney, OZ

PostPosted: Wed Mar 09, 2011 5:54 am    Post subject: Reply with quote

FWIW my take is that cant and toe in only work at specific hull speeds and wave shapes. Root chord of fins and parabolic rails are probably the more important parameters; plus fin rake (no more than 57 degrees) over the range of potential speeds.
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rodndtube
Dolphin Glider


Joined: 06 Jan 2004
Posts: 690
Location: USA, MD, Baltimore

PostPosted: Wed Mar 09, 2011 1:02 pm    Post subject: Reply with quote

puurri wrote:
FWIW my take is that cant and toe in only work at specific hull speeds and wave shapes. Root chord of fins and parabolic rails are probably the more important parameters; plus fin rake (no more than 57 degrees) over the range of potential speeds.


Help me out here, purri. And a few others I am sure. What is root chord of fins and how do you define rake. Does length or rake of any importance other than angle? Thanks!
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puurri



Joined: 26 Oct 2009
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Location: sydney, OZ

PostPosted: Thu Mar 10, 2011 8:52 pm    Post subject: Reply with quote

Root chord is an aeronautical term referring to the transition area from wing to body (fin to hull). It appears that unless there is a "fillet" or transition piece then turbulence (drag) is the result. Some glassed in fins used to have some form in order to brace the fin against side and torsional forces. Root chord contributes to lift and diminishes drag.

Perhaps a filet of Sikaflex might help boxed fin systems.

I posit that there is a relationship between fin length vs drag and consequential vortex shedding due to several factors. Aeronautical manuals and a quick google on Swaylocks gives a variety of elipses to choose from. I favour equally shaped fins sides over a wing profile and don't favour cant or toe in as it only works to optimum in a certain speed range. Cant is probably what adjustable canards do in for aircraft control systems.

I believe that the 57 degree is the optimum longest single length over the leading edge of the fin but a wiki on aeronautics would be a good idea. FWIW I don't favour excessive rake and extended trailing surfaces past the fin base's mid point (just my thoughts).
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bgreen



Joined: 20 Feb 2004
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Location: Qld. Oz

PostPosted: Sun Mar 13, 2011 2:35 pm    Post subject: Reply with quote

Those with an interest in fins might find something of interest here:

http://www.4wfs.com/knowledge/general-knowledge/

Bob
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rodndtube
Dolphin Glider


Joined: 06 Jan 2004
Posts: 690
Location: USA, MD, Baltimore

PostPosted: Fri Mar 18, 2011 8:43 am    Post subject: Reply with quote

Try the root URL and then browse around in the Knowledge section:
http://www.4wfs.com/
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