Dimple Bottoms ???

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Cpt.Caveman
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Re: Dimple Bottoms ???

Post by Cpt.Caveman » Wed Sep 28, 2011 5:23 pm

Man that looks awesome...

How much extra speed do you think you're getting, as a percentage? 10%? 20%?
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Re: Dimple Bottoms ???

Post by pridmore » Wed Sep 28, 2011 5:36 pm

hard to say but from my first 3 or 4 surfs in varied conditions, I will say a minimum of 10% but a few waves it was quite a bit more I think...I am excited about this and am trying to get my mates on them asap...they dont share my enthusiasm YET.... :lol:
I have a board in the racks fully shaped with pretty serious bottom contours but if I hadnt finished it, I definitely be doing the dimples on it too..... my son is getting one real soon too.... 8)

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Re: Dimple Bottoms ???

Post by ric_vidal » Thu Sep 29, 2011 8:56 am

Jorgo wrote:That so they can get the dimples Ric - by way of balls smacking into wicket and creating craters :oops:
Hey - there's a name for you Mark "Crater Critters" - your little pacman symbol be perfect :D
That'd be it J-Lo.

MP, consider oval dimples...

Ever had a real close look at a golf ball?

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Re: Dimple Bottoms ???

Post by pridmore » Thu Sep 29, 2011 11:26 am

yeah, but will have a closer look... I dunno if I want them to go quicker, will continue to tinker with them but it feels really good as is....but I am sure they'll morph as I ride and shape more, have a few others to trial this board as well....but next one will be a very simple shape so its easy to gauge whats doing what.....I think more dimples isnt the way to go, its got a slippery almost mildy disconnected feel coz of the layer of air which is the reason for the speed but wouldnt want to take that disconnected feel too far.....might make myself a summer small wave high volume version for the grovel so I can ride and test it alot over next months, this one is a bit under volumed so might get it to a guy who tests and trials my stuff now, Mitch Surman, hes a semi-pro l-boarder and rips and he rides everything well, keen to get his feedback.....

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Re: Dimple Bottoms ???

Post by alakaboo » Thu Sep 29, 2011 11:57 am

dimples, low volume and hard 60-40 rails was a good combo for bodyboards 20 years ago.

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Re: Dimple Bottoms ???

Post by offshore1 » Thu Sep 29, 2011 11:42 pm

ric_vidal wrote:MP, consider oval dimples...

Ever had a real close look at a golf ball?
wouldn't the oval shape be a function of the curved sphere of the golf ball?
Flatten it out to a flat plane and the ovals would round up wouldn't they?
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Re: Dimple Bottoms ???

Post by ric_vidal » Fri Sep 30, 2011 9:48 am

offshore1 wrote:
ric_vidal wrote:MP, consider oval dimples...

Ever had a real close look at a golf ball?
wouldn't the oval shape be a function of the curved sphere of the golf ball?
Flatten it out to a flat plane and the ovals would round up wouldn't they?
Golf balls, or some of the ones I have seen, are a combo of shapes. I had always thought they were uniform until I had a closer look... maybe it was just tiestlist :wink:

Golf balls spin and tumble, in my case they just start straight then veer right! They don't move, nor are they controlled like a surfboard.

Offal, it could just be a matter of form over function, but I believe oval is more suited to the whole planshape/moving in specific direction thing... I’m sure if we looked around hard enough there would be a multitude of examples designed by boffins and wind tunnel-tested that would suggest what is the most efficient. No?

Diagram below: Whilst this pertains to an object rather than a dent :D the principle might be the same for what MP is trying to achieve.

And maybe that is all an oval is, more streamlined. I wouldn’t suggest for one minute a pointed exit, god knows Mark’s glasser and sander but be shuddering every time he walks through the door.

Over to you, Offness!
sphere-airfoil-comparison.jpg
Source: http://www.aerospaceweb.org/. ../q0215.shtml

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Re: Dimple Bottoms ???

Post by pridmore » Fri Sep 30, 2011 12:55 pm

thanX RV, interesting...to be honest, I've already over achieved as far as increased speed goes, had a sesh today in really fun 2-3ft waves and felt like I was flying and now that I am starting to understand the board it means I can utilise the speed and time things much better, my mind is spinning with ideas of how and when to use this to maximise performance on certain boards...but I gotta not let my enthusiasm get the better of me.....or do I :roll: 1 wave today, I purposely kinda let myself get held up in the lip, just a tiny stall as soon as I got to my feet, then a really slight nudge and it was like I got shot out of a cannon, fair enough the waves were almost perfect peaks and very easy to read and ride but was also ideal to play with the capabilities of the board nd I learnt alot that sesh....but the speed still blows me away...makes me think you may be able to get away with smaller fins as less drive is required but then again, when ya doing turns with alot of speed, you need hold from the fins.... :D

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Re: Dimple Bottoms ???

Post by offshore1 » Fri Sep 30, 2011 1:15 pm

"The reason why golf balls have dimples is a story of natural selection. Originally, golf balls were smooth; but golfers noticed that older balls that were beat up with nicks, bumps and slices in the cover seemed to fly farther. Golfers, being golfers, naturally gravitate toward anything that gives them an advantage on the golf course, so old, beat-up balls became standard issue.

At some point, an aerodynamicist must have looked at this problem and realized that the nicks and cuts were acting as "turbulators" -- they induce turbulence in the layer of air next to the ball (the "boundary layer"). In some situations, a turbulent boundary layer reduces drag.

If you want to get deeper into the aerodynamics, there are two types of flow around an object: laminar and turbulent. Laminar flow has less drag, but it is also prone to a phenomenon called "separation." Once separation of a laminar boundary layer occurs, drag rises dramatically because of eddies that form in the gap. Turbulent flow has more drag initially but also better adhesion, and therefore is less prone to separation. Therefore, if the shape of an object is such that separation occurs easily, it is better to turbulate the boundary layer (at the slight cost of increased drag) in order to increase adhesion and reduce eddies (which means a significant reduction in drag). Dimples on golf balls turbulate the boundary layer.

The dimples on a golf ball are simply a formal, symmetrical way of creating the same turbulence in the boundary layer that nicks and cuts do."



Granted, a surfboard isn't a sphere, but,.... in a way, the wave is,... it's a cylinder anyway.

So, like on a golfball, the dimples on your board, Priddy, convert 'sticky' laminar flow into more slippery turbulent flow, which helps release the board from the sucking clutches of the water in the wave.
I reckon all the pressure dings on the bottom of my board are a good thing :lol:


hey ric, I know times are tough these days, but I haven't seen a Virginsurf paycheck in over a fortnight... :evil:
Last edited by offshore1 on Fri Sep 30, 2011 1:25 pm, edited 1 time in total.
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Re: Dimple Bottoms ???

Post by pridmore » Fri Sep 30, 2011 1:22 pm

offshore1 wrote:"The reason why golf balls have dimples is a story of natural selection. Originally, golf balls were smooth; but golfers noticed that older balls that were beat up with nicks, bumps and slices in the cover seemed to fly farther. Golfers, being golfers, naturally gravitate toward anything that gives them an advantage on the golf course, so old, beat-up balls became standard issue.

At some point, an aerodynamicist must have looked at this problem and realized that the nicks and cuts were acting as "turbulators" -- they induce turbulence in the layer of air next to the ball (the "boundary layer"). In some situations, a turbulent boundary layer reduces drag.

If you want to get deeper into the aerodynamics, there are two types of flow around an object: laminar and turbulent. Laminar flow has less drag, but it is also prone to a phenomenon called "separation." Once separation of a laminar boundary layer occurs, drag rises dramatically because of eddies that form in the gap. Turbulent flow has more drag initially but also better adhesion, and therefore is less prone to separation. Therefore, if the shape of an object is such that separation occurs easily, it is better to turbulate the boundary layer (at the slight cost of increased drag) in order to increase adhesion and reduce eddies (which means a significant reduction in drag). Dimples on golf balls turbulate the boundary layer.

The dimples on a golf ball are simply a formal, symmetrical way of creating the same turbulence in the boundary layer that nicks and cuts do."



Granted, the board isn't a sphere, but,.... in a way, the wave is,... it's a cylinder anyway.

So, like on a golfball, the dimples on your board, Priddy, convert 'sticky' laminar flow into more slippery turbulent flow, which helps release the board from the sucking clutches of the water in the wave.


hey ric, I know times are tough these days, but I haven't seen a Virginsurf paycheck in over a fortnight... :evil:

wow, great reading mate, appreicate that, it makes sense and when someone can put it in those terms, makes me realise this is really working how I think and fell it is.....where is that from ?, any chance of the reference or a link ??? :D

Image the waves I tested it out intoday, super fun and ideal for feeling out a new sled.... :)
Last edited by pridmore on Fri Sep 30, 2011 2:20 pm, edited 1 time in total.

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Re: Dimple Bottoms ???

Post by offshore1 » Fri Sep 30, 2011 1:29 pm

http://entertainment.howstuffworks.com/ ... tion37.htm
I just googled "why there are dimples on golf balls"
ah the wonders of the innarnet
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Re: Dimple Bottoms ???

Post by ric_vidal » Sat Oct 01, 2011 8:25 am

offshore1 wrote:"Laminar flow has less drag, but it is also prone to a phenomenon called "separation." Once separation of a laminar boundary layer occurs, drag rises dramatically because of eddies that form in the gap.
This is also why sanded boards are faster than polished ones.

Good stuff, comrade.

Might be a good name MP - turbulator :idea:
offshore1 wrote:hey ric, I know times are tough these days, but I haven't seen a Virginsurf paycheck in over a fortnight... :evil:
Well, it was ‘performance-based’ and quite frankly you have been a bitter disappointment. Your distribution agreement is coming up for revue at the end of the year so less time innernet, more time spreading the gospel, not seed, might be in order.

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Re: Dimple Bottoms ???

Post by Cpt.Caveman » Mon Oct 03, 2011 10:11 am

What sort of general bottom contour did you shape with it? Flat or concaved?
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Re: Dimple Bottoms ???

Post by pridmore » Mon Oct 03, 2011 11:01 am

very subtle single all the way, flat by pod...but this was shaped from a blank I had lying around so it wasnt planned out, just a creative outburst into the nearest piece of foam with ideas that have been just waiting to get out.... :roll: but I love these type of things, unplanned or even accidents can become successful or at least you can learn from them and go on another tangent which then may lead you somewhere where you would neve have been if you just did the planned and clearly thought out...I like to go with the moment sometimes, whatever makes the heart sing ...
re the bottom shape, I think the slight single feeding the dimpes works well, nuthin to compare it to but feels great to me....

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Re: Dimple Bottoms ???

Post by Cpt.Caveman » Mon Oct 03, 2011 12:15 pm

Sounds like great fun, its a tough job you have there mate :)

I wonder what a deep double with dimples lining the deepest part of the concave would do?

I guess that would decrease the number of overall dimples and potentially decrease the benefits of the dimples though...

Man, I wish I was up your way MP. I would be begging for a test run on every one of these Frankenstein creations!
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Re: Dimple Bottoms ???

Post by diggerdickson » Mon Oct 03, 2011 2:01 pm

jeez mark, wonder how these would go with the mckee set up, as they are quick as already
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Re: Dimple Bottoms ???

Post by offshore1 » Tue Oct 04, 2011 1:12 am

You're a bloody slavedriver vidal. Been playing eighteen holes a day researching this phenomenon for three weeks now and this is the thanks I get..
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Re: Dimple Bottoms ???

Post by ric_vidal » Tue Oct 04, 2011 8:52 am

offshore1 wrote:You're a bloody slavedriver vidal. Been playing eighteen holes a day researching this phenomenon for three weeks now and this is the thanks I get..
Yeah thanks, but last time I looked we weren’t selling golf hardware... here’s a hint, VirginSURF.

F*ck it’s hard to get good help. :mrgreen:

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