fins forward

What works and what doesn't. Share design ideas, references and contacts for paipo board builders.
karuhi
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fins forward

Unread post by karuhi » Thu Jun 12, 2014 4:52 pm

airboy808 asked an interesting question on soulgliders thread about his board, that i'm wondering if any of you wise ones out there read.
"Thinking bumping quad fronts to 14.5" for fronts. Rears not sure yet. Figure moving quads up like Ozzie kneeboards will loosen it up at the rear".
I've since looking at knee boards been wondering something along the same lines - would it help? or even work? has anyone tried it?

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Re: fins forward

Unread post by nomastomas » Fri Jun 13, 2014 5:08 pm

When riding on a wave, the location of kneelo rider's center-of-mass is different than a prone rider's. Its further forward. That is why the fins are pushed up and why the outline curve on most non-fish kneeboards begins to accelerate at this point. I've found that in general, on multi-finned prone boards, the more curve in in the last third of a prone board's outline, the further up from the tail the fins should go. The flatter the outline curve, the further back the rail fins should be placed. Ideally, front fins should be placed just behind the "hip" in the outline. -tp
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Re: fins forward

Unread post by GeoffreyLevens » Fri Jun 13, 2014 5:11 pm

In addition to outline curve, I would think fin placement also would vary w/ riding style; if you use more hands/arms to turn vs more hip pressure fins might go better a bit further forward of back.

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Re: fins forward

Unread post by nomastomas » Fri Jun 13, 2014 6:14 pm

Rail fins accomplish two basic functions: (1) They create drag and (2) they create hold. The drag helps the surfcraft to turn, much like dragging a paddle while kayaking. The foil of the fin creates lift in the direction of the rail, pushing/pulling the rail into the wave face. You want the drag/hold to occur at the spot on the rail with the most water contact while turning. That would be the hip. True, dragging an arm or swim fin adds additional drag. But if your finned board is set up properly, you shouldn't have to add additional drag to turn properly. Now, if you're dragging hands, arms, knees, etc, to stall for a tube, that is a different story. If your "style" has evolved to where you're consistently dragging appendages to turn, it may be that your board doesn't have the proper fin set-up, i.e. fin location, toe-in, fin size, etc. and you've developed a creative way to compensate for this. Just a thought....
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Re: fins forward

Unread post by soulglider » Sun Jun 15, 2014 8:53 am

when i was using jeff mccallum to shape my boards we used to hot glue the fins in place so they could be popped off and moved until we found the right placement.
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Re: fins forward

Unread post by GeoffreyLevens » Sun Jun 15, 2014 10:09 am

soulglider wrote:when i was using jeff mccallum to shape my boards we used to hot glue the fins in place so they could be popped off and moved until we found the right placement.
I I have mostly hot glued them in place to hold while applying glass lay-up for permanent placement;would not have thought that hot glue would hold under that amount of pressure/leverage!

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Re: fins forward

Unread post by soulglider » Mon Jun 16, 2014 9:10 am

just dont bump them and they would last a full go out...
deathbedpaipo.blogspot.com

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Re: fins forward

Unread post by krusher74 » Thu Jun 26, 2014 3:26 am

I'm working on designing a version of "The spud" as a prone board for the endeavour surf company 8-)

How would you describe the fin placement on this stand up board (for 3 tab keel fins)

I wanted to move to more toe for better turning and a prone only 2 tab fin placement, I don't know where the "hip" is on this outline :?
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Re: fins forward

Unread post by GeoffreyLevens » Thu Jun 26, 2014 6:35 am

"Hip" at least to my mind is where the outline "line" breaks more sharply in direction as headed towards the tail.Per the picture there really isn't a hip I would say. If someone held a gun to my head and said, "Point to the hip or die and if you say there isn't one that will be the last thing you ever say!" then I would probably call it a the wide point.

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bgreen
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Re: fins forward

Unread post by bgreen » Fri Jun 27, 2014 11:01 am

Krusher,

If they are going to spend money on a prototype why don't you get one of those fin systems installed where you can vary toe-in and cant. Then you can experiment for yourself and be more certain that what you recommend will work.


Bob

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krusher74
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Re: fins forward

Unread post by krusher74 » Sun Jun 29, 2014 9:33 am

bgreen wrote:Krusher,

If they are going to spend money on a prototype why don't you get one of those fin systems installed where you can vary toe-in and cant. Then you can experiment for yourself and be more certain that what you recommend will work.


Bob
I will look into that, i did not know they existed :shock:

On the few finned boards I have tried, I have had to move back over the fins to get them to turn,I want to try to avoid that on this prototype. :?

Did you mean these http://www.4wfs.com/knowledge/general-k ... s-it-work/

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Re: fins forward

Unread post by airboy808 » Sun Jun 29, 2014 11:28 am

4ws boxes are super adjustable but fin selection and sourcing fins maybe a bear.

Look into probox, gearbox, and soon to be released gearbox II fin boxes. They allow for fore aft adjustment, fcs fins fit without any adaptors, and cant can be adjusted (with adaptors on probox).

With fins forward and prone my guess you will need to lean forward to engage the forward rail and then pivot of fins forward placement versus lean back at the hip to turn.

Tried riding prone on a few waves yesterday on my Ozzie fins forward thruster parkes kneeboard. Sensation felt like to turn you had to lean forward and apply pressure via elbows to turn. Of course kneeboard is 5'9" so a little long compared to what a foam paipo would be.

Research continues

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bgreen
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Re: fins forward

Unread post by bgreen » Sun Jun 29, 2014 12:41 pm

Krusher,

That is the system I know of - as Airboy suggests there may be others. Probox Larry posts on Swaylocks.

Bob

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krusher74
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Re: fins forward

Unread post by krusher74 » Mon Jun 30, 2014 2:34 am

airboy808 wrote:4ws boxes are super adjustable but fin selection and sourcing fins maybe a bear.

Look into probox, gearbox, and soon to be released gearbox II fin boxes. They allow for fore aft adjustment, fcs fins fit without any adaptors, and cant can be adjusted (with adaptors on probox).

With fins forward and prone my guess you will need to lean forward to engage the forward rail and then pivot of fins forward placement versus lean back at the hip to turn.

Tried riding prone on a few waves yesterday on my Ozzie fins forward thruster parkes kneeboard. Sensation felt like to turn you had to lean forward and apply pressure via elbows to turn. Of course kneeboard is 5'9" so a little long compared to what a foam paipo would be.

Research continues
That's interesting, as a bodyboarder of 20 years I drive the rail through my elbow and hip bones, don't know if that's what I turn off though, but good tohear that it possible even on a 5.9 to have to apply pressure forward to turn.

I will look at the systems you have mentioned, thanks :D

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