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iGRF View Drop Down
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    Posted: 12 Apr 13 at 4:29pm
Right they're bored again, and need some more piss taking semisailingscience from the master of virtual physics.

To recap facts concerning laminates with bubbles being faster than laminates without bubbles which of course I've now proven beyond any doubt, but they are still covering their ignorance with irony over on the photo thread.

There followed an exchange about a Tv program about bubbles to which I came across with this gem.

"I hope it works I'm already fitting bubble expulsion kit to the Alto..

Years ago we tried a ram air system to stream air from the rear of chines under the hull in speed boats.

Wish we'd had laminates with bubbles in them back then, they'd have been much faster.

Oh, now I've just thought of something else, I'll copy this to the wiki, think I can get you going all over again on hygroscopy.."


So now, bubbles aside which is already proven and true now it's been on that BBC4, so what do the team think about having a laminate that used hygroscopic (not sure if that is the term there are two one meaning expels water the other meaning attracts water as per fish scales) anyway there are plastics that have this feature, I was thinking about it back in the V2 early days. There are sprays, we used them back in the water ski racing days, made hulls super skippy, probably banned in your world.

So the question is do you deny they a)Exist and b)Work to make your boat faster and if so why, or if not why not. (I know they do but could never understand exactly why).



Edited by iGRF - 12 Apr 13 at 4:30pm
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:35pm
No scratch all that, Hydrophillic is what I meant, Hygroscopic withdraws the water, Hydrophillic retains the water, so the theory is a water on water less wetted surface drag...

So how to build into a laminate alongside those bubbles and make the super slippy surface..
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Post Options Post Options   Quote alstorer Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:39pm
Substances that repel water are "Hydrophobic". An example of a Hygropscopic material woul;d be a sponge.
 
Anyway, your attention is drawn to Rule 53 from the RRS:

53 SKIN FRICTION

A boat shall not eject or release a substance, such as a polymer, or

have specially textured surfaces that could improve the character of

the flow of water inside the boundary layer.

-_
Al
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Post Options Post Options   Quote fab100 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:42pm
[QUOTE=alstorer]Substances that repel water are "Hydrophobic". An example of a Hygropscopic material would be a sponge.
 
Anyway, your attention is drawn to Rule 53 from the RRS:
[quote]

Come on Al, grf does not recognise the laws of physics here, never mind a man-made construct like the RRS


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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:44pm
I understand why Rule 53 might try to prevent the release of harmful substances, but I've never understood why it seeks to control surface texture. Isn't that a matter for individual classes?
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Post Options Post Options   Quote fab100 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:47pm
Originally posted by Peaky

I understand why Rule 53 might try to prevent the release of harmful substances, but I've never understood why it seeks to control surface texture. Isn't that a matter for individual classes?

Costs get astronomical for a pointless arms race. It's a really sensible rule IMHO
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Post Options Post Options   Quote craiggo Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:48pm
This goes back to the sharkskin tech in swimming, and sub boundary layer vortex generators. It's the argument of super smooth vs rough finish. The fluid dynamic theory indicates that a benefit is achievable when using such a device but in practice the empirical testing completed by the likes of Bethwaite for example show that it's difficult to get a benefit. This is possibly due to water/air interactions and also 6-component dynamics ie our boats don't tend to go straight through water, they pitch and yaw and accelerate fairly violently, rather than operate at a fixed condition.
Discuss...

Edited by craiggo - 12 Apr 13 at 4:50pm
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:55pm
And they're off!

So c'mon boys which is it Hygroscopic,Hydrophobic,Hydrophillic? and yes I knew it was banned after I tried to use it in the early days of windsurf racing (It was ok in offshore powerboat class racing.).
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Post Options Post Options   Quote fab100 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 4:56pm
Originally posted by craiggo

This goes back to the sharkskin tech in swimming
Discuss...

...and well before that - before even Mark Spitz in the dodgy 'tache and budgie smuggler days

I'm sure they were talking about this tech in 70s Americas Cup 12 metres and before

Mind those were the days we painted boats with graphite based paint, sanded it smooth and looked like coal-miners at the end of a shift as a consequence
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 13 at 5:01pm
Originally posted by fab100


Originally posted by Peaky

I understand why Rule 53 might try to prevent the release of harmful substances, but I've never understood why it seeks to control surface texture. Isn't that a matter for individual classes?

Costs get astronomical for a pointless arms race. It's a really sensible rule IMHO


How can you say that? Totally illogical, like the replica sail but not replica hull anathema, y'all spend thousands developing faster sails, yet the simple practice of golf balling the underside of the hull for example might improve performance whilst improving structural rigidity and reducing weight, it's typical dinghy luddite mania..
Or you just buy this spray stuff like I'm going to for the next FOM and no-one will notice as it's clear when dry and the surface only goes like fish skin once the boat is in the water.
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