Author Topic: shape3D guru (help please!)  (Read 3955 times)

TallDude

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Re: shape3D guru (help please!)
« Reply #15 on: August 19, 2020, 03:50:14 PM »
This is an attractive shape BTW. See attached rough copy with simplified lines. I think you can finish it from here quickly.
Looks like this...
It's not overhead to me!
8'8" L-41 ST and a whole pile of boards I rarely use.

PonoBill

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Re: shape3D guru (help please!)
« Reply #16 on: August 19, 2020, 07:25:11 PM »
Yes, I'm kind of McLoving that shape except for the bevelled tail, the tail would be great on a SUP foil board, but for winging I think i'd like a more rounded transition. Still, if I had this as a blank i'd be a happy dude.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: shape3D guru (help please!)
« Reply #17 on: August 19, 2020, 10:14:25 PM »
are you thinking to ditch the centerline V - or are you talking about rounding off the transition from flat bottom to the rear bevel?

I really puzzled over how much roundness to add to the bottom to tail transition since I saw Dwight's treatment of tail shapes.  He prefers tail C (at least according to his website)


jondrums

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Re: shape3D guru (help please!)
« Reply #18 on: August 20, 2020, 01:23:16 AM »
Thanks for all your help Burchas - working from your file got me close enough to where we can do just a bit of hand-work after the CNC cut.     Here's my shaping notes after CNC cut



Dwight (DW)

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Re: shape3D guru (help please!)
« Reply #19 on: August 20, 2020, 03:50:39 AM »
Put the handle in the bottom. You donít need one in the deck.

Dwight (DW)

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Re: shape3D guru (help please!)
« Reply #20 on: August 20, 2020, 04:02:19 AM »
Have you noticed Kalama doesnít shape his rail at all. Flat dam square, top and bottom edge sharp. That adds HUGE stability. You gave away all stability rounding your rails.

Even KT and the flyingdutchman are starting to use flat square rails on some boards showing up on instagram.



burchas

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Re: shape3D guru (help please!)
« Reply #21 on: August 20, 2020, 05:26:48 AM »
Thanks for all your help Burchas - working from your file got me close enough to where we can do just a bit of hand-work after the CNC cut.     Here's my shaping notes after CNC cut

You're welcome. Just few minutes of tweaking your file. Looking over your shaping notes, it's not hard to get there with shape3D just by adding 1 curve (between rail to apex), 1 slice  for the  rail transition in the front and two 3d layers for tail and nose. The rest is just tweaking controls to generate nice transitions. Probably an overkill with the cuts i've seen from most machines though my board required almost no touching out of the CNC.

As for the handle, having only one on the bottom did the trick for me as DW pointed out.
in progress...

PonoBill

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Re: shape3D guru (help please!)
« Reply #22 on: August 20, 2020, 06:40:09 AM »
The bottom handle works well if it's perfectly located to balance the foil. But i'd still add a top handle for those occassions you have to carry the board some distance. It's easier to carry the whole thing with the foil mast across the front of your thighs and one hand on the foil or mast. Just don't head into shorebreak that way.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: shape3D guru (help please!)
« Reply #23 on: August 20, 2020, 09:27:39 AM »
Have you noticed Kalama doesnít shape his rail at all. Flat dam square, top and bottom edge sharp. That adds HUGE stability. You gave away all stability rounding your rails.

Thanks for the tip.  Makes total sense that volume out at the edges has the biggest impact.  But "give away all stability" by having round edges?  Hard to believe that - why?

Dwight (DW)

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Re: shape3D guru (help please!)
« Reply #24 on: August 20, 2020, 09:39:13 AM »
Have you noticed Kalama doesnít shape his rail at all. Flat dam square, top and bottom edge sharp. That adds HUGE stability. You gave away all stability rounding your rails.

Thanks for the tip.  Makes total sense that volume out at the edges has the biggest impact.  But "give away all stability" by having round edges?  Hard to believe that - why?

When I first prototyped square rails a few years ago, it doubled the stability of the board. It blew my mind how much it improved.

burchas

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Re: shape3D guru (help please!)
« Reply #25 on: August 20, 2020, 01:45:32 PM »
Thanks for the tip.  Makes total sense that volume out at the edges has the biggest impact.  But "give away all stability" by having round edges?  Hard to believe that - why?

Fat square rails with sharp edges have a very good roll resistance. These are fast as well. My board at 28.5" has impressive stability in rough conditions. For the sake of my shins
and other bones I skipped the top sharp edges though. Not a good experience when remounting the board.
in progress...

jondrums

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Re: shape3D guru (help please!)
« Reply #26 on: August 20, 2020, 02:53:57 PM »
awesome advise, thank you!

I'm going to look into this a little further to see if I can understand the science behind why hard corners provide such stability improvements.  That's because I'm stubborn, and gosh its ugly so it'd better work.

jondrums

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Re: shape3D guru (help please!)
« Reply #27 on: August 20, 2020, 10:58:45 PM »
I really like the way the rounded rails look, so I wanted to be sure before I ditch them for ugly boxy rails.  So I put two cross sections into CAD with exactly the same area (would yield the same volume board) and looked at the "righting moment" versus tilt angle in the water.  The righting moment can be determined by looking at the lateral shift in center of buoyancy as the board floats at an angle.  I did this for three different submersion levels to see if that is a factor.  I'll share some of the data below to give you a sense of what I found - which is that any difference in righting moment between the two shapes is within measurement error.

Perhaps there is another effect I'm not thinking of?  I'd really like to know - this is super puzzling to me.  I don't want to discount the experience that you guys have - I am sure you know what you are feeling in the boards you've ridden!

Or perhaps the idea is that if we keep the width of the board the same, then boxy rails add a bit more volume where it counts to give extra stability?  No question, for the same volume and same stability, boxy rails allow the width to be a bit narrower.

Here's the two cross sections I studied (obviously relevant to the board I am shaping).  The three blue lines are the the three float levels I studied.


And here is the data for righting moment versus tilt angle in the water (this is for the most submerged float line - but all three sets of data were similarly identical between rounded and boxy rails).

liv2surf

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Re: shape3D guru (help please!)
« Reply #28 on: August 21, 2020, 12:12:41 AM »
Thanks for all your help Burchas - working from your file got me close enough to where we can do just a bit of hand-work after the CNC cut.     Here's my shaping notes after CNC cut

Nice. Nah, don't hand shape it. Move the current 'post CNC features' into the Shape3Dx file (so you can duplicate it, build on that shape later and share it).
6'6" CRUZ 'CIM' Wing Foil SUP (130L)
9'6" CRUZ Surf foil SUP (152L)
Cabrinha Crosswing X2 4m, 5m, 6m
Axis 1020; Axis 1150, standard fuse, 500 stab
65cm (and 90 cm) Project Cedrus carbon mast
Chinook Thrust 92 Paddle -- fixed 78" length
Me: 190 lbs, 64 yo Half Moon Bay, CA

Dwight (DW)

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Re: shape3D guru (help please!)
« Reply #29 on: August 21, 2020, 04:42:54 AM »
You didnít compare same width boards.

I continue to get feedback from people that other boards (brands with pretty rails) are less stable.

Kalama has actually gone more extreme in his squareness over the last two years. His boards are the ones I recommend people buy.

 


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