Stoneburner's assist build 48 1/2" body board

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doc's picture
doc
Joined: 03/18/2004

3.66

3X-1=10
add one to both sides
3X=10+1

divide both sides by three

X=11/3 or 3 2/3 or 3.6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666 infinitely repeating

And now you understand my problems. Problems plural 'cos first I had to go through such things myself for the kid and second I meant to and didn't write the original equation as

3X + 1 = 10,

senility strikes again.

doc.... 

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parthenonsurfer's picture
Joined: 02/19/2010

Doc- so does eyesight. When I looked at it on my laptop, I thought your equation read "3x plus 1 equals 10". Misread it! Damn it sucks gettin old.

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stoneburner's picture
Joined: 12/30/2007

bgreen wrote:

Regarding the current board, my initial reaction is that the tail channels look too bulky. However, having said that, it depends on what type of wave is intended to be ridden and what experience is sought. I've ridden boards people have raved about and not felt the same way. I also tend to like more curved lines (I can see how this can go wrong as I type) .

However, the only really proof is in how it rides. Great workmanship there.

Bob

Not sure what you mean by "too bulky."

Agreed the important assessment will be the qualitative comparison to what is out there.  And what you like.

The objective is low drag, improved tracking/control -- without fins.

The channel could be used in any shape.

Bill

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bgreen's picture
Joined: 10/21/2007

By bulky I mean thick. Attached is a photo looking down from the tail of my favourite board - it is number 7 in a series, refining an original design of Larry Goddard. 

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stoneburner's picture
Joined: 12/30/2007

bgreen wrote:

By bulky I mean thick. Attached is a photo looking down from the tail of my favourite board - it is number 7 in a series, refining an original design of Larry Goddard. 

What is your thickness?

Tail thickness is determined by channel depth which is not a fixed constant.  Or vice versa...

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bgreen's picture
Joined: 10/21/2007

It's hard to measure, probably 1/4" on wing and 1/2" at tail, flatter section, but it is a curve, so tricky to be exact. 

This photo is of a board from John Galera. 

I'm off to work now, happy to chat later. 

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stoneburner's picture
Joined: 12/30/2007

So far, the Galera boards I have seen use linear channels.

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bgreen's picture
Joined: 10/21/2007

Yes, like pontoons, with the foam scooped out down the centre, which is fibreglass like a spoon.

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stoneburner's picture
Joined: 12/30/2007

I suppose it would be possible to shape a ""torso/chest well" into the deck to decrease thickness overall.  And add belly to the nose for further thinning.

It is likely the channel effect will require riding weight forward to trim.

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bgreen's picture
Joined: 10/21/2007

From someone who may have never have solved a calculus problem (Doc I'll be contacting you for tuition. Your website tuition was much appreciated, only joking about the maths) I have  a simpler alternative to the grants application, though in covid times it could be problematic. A Swaylocks travel board. Another gets made, share it around and notes get taken and compared. I know Krusher likes shorter boards, 48" seems ok by me.

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doc's picture
doc
Joined: 03/18/2004

Ummmm- Bob, there's the thing: given a channel with dimensions A through Z, set in a particular board with dimensions a through z, you just learn whether or not that particular board works, and why it works or doesn't work is a whole 'nother animal, let alone whether or not the concept works. 

That's where Stonebreaker's idea of shipping precision computer cut channel; cartridges  (say that a few times fast ) comes in. You put one in anything you like, new large bodyboard-like paipo to  retrofitted klunker longboard and anything that turns your fancy, see what it does, get back to the rest of us with that . And we analyse, learn, change, adapt and go onwards, 

Oh, and being me, had a look, your coding is coming along nicely. `You're a credit to your teacher -

doc....

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bgreen's picture
Joined: 10/21/2007

Gday Doc,

I'm not sure on which web-sites I acknowledged your assistance on, but this one I did: http://home.brisnet.com.au/~bgreen/world/World.shtml

There was a guy in Australia who made boards, with removable tails. It didn't catch on as far as I know.  It might be possible to make a modular board, where you could try different rails, tail, nose etc - "bolt" on and off.   Not a commercial idea, but to test design parmaters. One for the mad scientists.

I see Krusher had some comments on hard rails - I sought to replicate my favourite board, twice. None were exact copies. Number # 2 in the series, tended to track a bit. I looked at the rails, with the shaper and they were harder. The board went better with more rounded rails (they were pretty sharp). This was on a board ridden finless. I loaned the board to a friend, and hope to get it back next year, when I do a trip down his way - he seems to have like the refined version.

I think on your advice, I got Huie to make me a 1" thick board. It was fun but I missed a few waves, because of the reduced volume. I'll drag it out again one day.

Bob

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stoneburner's picture
Joined: 12/30/2007

krusher4 wrote:

slater tried out a similar concept with Merrick, their design had a hole through to the deck to allow air from the top into the channel. 

https://www.cisurfboards.com/2010/kelly-slaters-latest-experiment-the-ch...

Looking at the Slater/CI board, I see a linear channel with what looks like concave panels forward and on either side of the channel.

The physics principle of my design is all about the curves -- in 2 dimensions.

Second drawing air into the channel would neutralize my channel's curved contour effects -- low pressure holding the tail in place.  The curves of the sidewalls create a bit of an optical illusion relative to the bottom.

Charlie's rail edge is fairly hard.  But I would say the edge has at least a 1/16" diam. round.  The rail shape I have been playing with uses top and bottom chamfers witrth a 3/4" rounded mid-section -- not that there is anything revolutionary about that shape.

Finally, it would be very difficult to hand shape this channel by peeling back the bottom surlyn/polyethylene of a standard BB, especially the channel bottom contour.

_____
The simplest way to evaluate this channel is try it in two boards of the same shape, one with and one without.  Granted the one with the channel would have slightly less volume.

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krusher4's picture
Joined: 08/16/2011

Does the physics of your design work differently than this? or any board with just a central tail concave that exits the tail?

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stoneburner's picture
Joined: 12/30/2007

krusher4 wrote:

Does the physics of your design work differently than this? or any board with just a central tail concave that exits the tail?

Based on my understanding of the physics, yes.

I stumbled across the physics behind my channel design 10 years ago.  

I made a quick beach bodyboard for the grandkids out of 3 sheets of unglassed, low density XPS housing insulation 3.5 years ago.  After that, I decided bodyboard builds were a good way to develop XPS/FG build technology.  

While trying some experimental XPS build tech, things kept going wrong, including a funeral in the midlle of a glass job.  I put that build on hold.  That's when I saw an effective way to use the physics behind the current channel design.  (Close to 2 years later, I finally salvaged that disrupted XPS bodyboard build tech project last week -- functional but no showroom piece.)

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krusher4's picture
Joined: 08/16/2011

So is the physics this: 

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thrailkill's picture
Joined: 05/07/2004

Before he became focused on hydrofoil body boards, Dr. Terry Hendricks PhD, was riding body boards at WindanSea in the early sixties, that had a similar feature on the bottom that functioned much like a NACA duct.      This ground was well plowed more than fifty years ago.

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Bill Thrailkill SHAPER SINCE 1958
stoneburner's picture
Joined: 12/30/2007

thrailkill wrote:

Before he became focused on hydrofoil body boards, Dr. Terry Hendricks PhD, was riding body boards at WindanSea in the early sixties, that had a similar feature on the bottom that functioned much like a NACA duct.      This ground was well plowed more than fifty years ago.

Dr. Hendricks was a talented individual.

Do you have pictures of the Hendricks "NACA duct?"

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krusher4's picture
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stoneburner's picture
Joined: 12/30/2007

krusher4 wrote:

NACA duct 

https://www.youtube.com/watch?v=rtEsdUzlIEk&ab_channel=TheGumoutChannel

Thanks K-4.  I am familiar with NACA ducts used for performance car air intakes.

Similar looking but a different final objective.  And I believe pressure in the standard NACA duct is high.

My design parameters are different.

Mr. T indicates Dr. Hendricks used it.  It would be nice to see Dr. Hendricks' design and application.

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bgreen's picture
Joined: 10/21/2007

You've mentioend the physics behind your design and the design parametrs being difefrent to the above photo, what is the idea behind the style of channel on the boad you've designed and what sorts of waves is it intended for? Wave type/size provides a context for understanding the theory. Thanks.

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stoneburner's picture
Joined: 12/30/2007

First, the design is intended to function as a "free-standing channel" in a fluid stream -- not connected to a fluid distribution system.  Channel dimensions will likely be affected by anticipated velocity.

Second, the channel contours are combined to produce an overall low-pressure effect under the tail.  The objective is to hold the tail in place for tracking/directional control and to allow the rails to better engage.  Perhaps too simplistic and over-generalized, the channel functions a low drag fin.  It is likely there will be other performance effects related to contours.

My original design was a for a 42" bodyboard.  The primary objective was/is to bring tracking/directional control to the standard "Boogie Board."  I have seen Bully Boards for larger riders.  So the 48" was for larger riders and/or smaller surf.

After I started designing the channel, I decided I would like to try it for a finless fish.  But it could be used for a variety of surfcraft.

The channel dimensions are intended to be dynamic rather than static -- adjusted for preference, velocity and board size.  The two current channels are the starting point for evaluation.  At this point, it is sort of like asking, "What is the best fin size and shape?"

Without testing, I can only speculate about specifics based on the physics...

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stoneburner's picture
Joined: 12/30/2007

My glassing skills with epoxy are mediocre.  The biggest challenge for me on this channel was a clean glass job on the channel's 90 degree edges and inner bottom angles.  I figured Charlie could do it without problems.

While Charlie was working on this build, I was trying to come up with a good way to hand laminate the channel.  The standard recommendation from several members has been to use spray adhesive to tack the dry cloth to the channel walls.  The biggest drawback to that method is finding a spray adhesive that won't melt EPS and that allows some small degree of re-positioning.  I tested an idea last week.

I always have a little residual epoxy from any glassing session.  I usually pour that into a paper plate so I can gauge when the mixed epoxy reaches the tack-free stage.  So, I decided the way to do this is a channel pre-seal with epoxy (which I would do anyway), basting the walls and top edge surface first.  Since I was playing around, I went for a narrow section at the bottom while I was at it.

I waited until the epoxy in the plate was still "slightly sticky" but not "tack-free."  I tested with the tip of a popsicle stick/tongue depressor (or a wood match stick).  When the wood tip still barely sticks but the resin has set up, I draped the dry cloth over the top edge and wall, holding the cloth off the bottom.  I smoothed the dry cloth onto the top first; then from top edge down the wall with a small plastic bodywork squeegee; press cloth lightly but snugly into the bottom 90 degree angle with squeegee while holding it off the bottom; then smooth cloth over a narrow section of the bottom.  

I let the resin set to tack free. Then I wetted out the dry cloth with a 2" chipping brush.  The test was done on a piece of low-grade packing EPS that formed a long 90 degree channel.  The final lamination was clean and tight.

My future approach will be to hand laminate the sidewalls independently from the channel bottom.

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parthenonsurfer's picture
Joined: 02/19/2010

Good job Bill. That looks like a very smart way to get your tight corners. The only water based contact adhesive that I could find that wouldnt eat the foam has a blue/green tint to it which might be a problem if your doing a clear layup.

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stoneburner's picture
Joined: 12/30/2007

Thanks Chris. 

3M 78 won't melt EPS/XPS and is sort of translucent.  But it has a "lace" spray pattern.  And while it says you can reposition for 45 seconds, in my experience that has not been easy to do with foam.

Bill

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krusher4's picture
Joined: 08/16/2011

when are you expecting the board to be ridden?

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stoneburner's picture
Joined: 12/30/2007

krusher4 wrote:

when are you expecting the board to be ridden?

I’m pretty much grounded for any travel until there is an effective CoVid-19 vaccine.

Regardless, I'm too old to be a credible test pilot.

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stoneburner's picture
Joined: 12/30/2007

Charlie's latest foam sculpture of my channel bottom BB arrived this afternoon.

42 X 21.75 x 2, EPS core with cork skins over and under FG.

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unclegrumpy's picture
Joined: 09/16/2006

Interesting.

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No; It's not an ironing board.

krusher4's picture
Joined: 08/16/2011

stoneburner wrote:

Charlie's latest foam sculpture of my channel bottom BB arrived this afternoon.

42 X 21.75 x 2, EPS core with cork skins over and under FG.

That design is very wide-nosed and wide point forward. You would need the same board without the channel to truly feel its effect.

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stoneburner's picture
Joined: 12/30/2007

Moved.

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fins's picture
Joined: 07/13/2012

this is great , THANKS everyone !

  "   

7 months ago

#31

sk8ment

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this build thread ans folloing dicussion is rad, make me pumped to get into the two belly boards i have half shapped in the shed, two edge railed beasts, inspired by greenough.

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@reclaim_surf formerly Skatement

(Adam) Sunshine Coast Queensland Australia  "

hiya Adam !

  just wondering if you have photos of your edge boards , please ?

  cheers !

  ben 

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*************************************************** http://www.benchipper.blogspot.com.au/

stoneburner's picture
Joined: 12/30/2007

fins wrote:

  just wondering if you have photos of your edge boards , please ?

  cheers !

  ben 

Do you mean a shot of the rails?

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stoneburner's picture
Joined: 12/30/2007

krusher4 wrote:

That design is very wide-nosed and wide point forward. You would need the same board without the channel to truly feel its effect.

The nose is 0.78" narrower than the same section in a Retro Fish (relative to the widepoint).

With board thickness being thin at the channel exit and with lower pressure under tail, riding postion should shift forward a bit.

Over the last two weeks. I have been communicating with a professional, custom bodyboard builder.  His comment about this particular bodyboard was,  "Your design looks good."

The channel effect should be fairly noticeable.  

I think I can ride it.

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