Banned Innovations in Sail Racing

beezer

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Annapolis
Curious to see what has been banned over the years.  I seem to recall trim tabs, bubbles being ejected along the hull to reduce drag, etc.  This is not to cheat in sailboat racing, it is related to a human powered submarine design.   

 
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valcour2

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51
Riblets (Rivlets?) used on Stars and Stripes in the 87 AC.  Applied as a film on the hull with micro-grooves of some sort.   Someone here likely has the details.  
 

 

12 metre

Super Anarchist
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English Bay
Curious to see what has been banned over the years.  I seem to recall trim tabs, bubbles being ejected along the hull to reduce drag, etc.  This is not to cheat in sailboat racing, it is related to a human powered submarine design.   
Let's keep in mind why the OP is asking this.

Further to the post by valcour2,  here is the relevant rule: 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.

IIRC, the 5.5 metre class and likely a few others experimented with tubes to eject polymers in the 60's.

I suspect that for human powered submarine design, you likely want the lowest drag.  To reduce form drag I believe there is an article by Tom Speers where he makes the assertion that low drag foil shapes are only really optimal for infinite span foils.  For bodies of revolution like a bulb or tube, you should take the Y co-ordinates and raise to the 1.5 power.

Okay, it wasn't an article by Tom Speer, it was some of his posts in this thread in Boat Design.net beginning with post # 4: https://www.boatdesign.net/threads/keel-bulb-design-help.6113/

Here is a snippet from his post # 4:  

There's a difference between the flow around a two-dimensional cylinder and the flow around an axisymmetric bulb. The whole point of shaping an airfoil or a bulb is to manipulate the boundary layer through the pressure distribution along each surface streamline. Using an airfoil section for a bulb profile will not give you the design pressures or the desired boundary layer development.

Alex Strojnick, in his book, "Laminar Aircraft Technologies" (published by the author, now deceased), recommends taking airfoil coordinates to the 3/2 power (and scaling to the original thickness) to use them as templates for bodies of revolution. The result will be a more pointed shape than the corresponding 2D airfoil profile. For example, the figure below shows the NACA 66-021 section converted to an axisymmetric profile using Strojnick's technique. This resembles a Parson's low drag body shape, although Parson designed his bodies using a CFD analysis code and an optimization technique (Parson, J. S, Godson, R. E, Goldschmied, F.R., "Shaping of Axisymmetric Bodies for Minimum Drag in Incompressible Flow", Journal of Hydronautics, July 1967.)


Okay, not a cheater thing, but IMO not a well known consideration in the design of low drag bodies.

 
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fastyacht

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All mamner of struts umless prescribred.  Outriggers excepy by exception IMOCa)

Qiadrilteral staysails.

A bunch of oter stuff

 

10thTonner

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There will always be things banned in some classes that are allowed in others… trapezes, hiking straps, keel trim tabs, membrane sails, movable ballast, carbon spars, autopilots, slack lifelines, faired bottoms, articulating bow sprits, outriggers, lifting foils, more than one hull, etc etc… hey, these golden globe types even banned breathable foulies! 

 

Zonker

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The hula wasn't banned but was a clever idea to get a different hull shape than the AC rule allowed. Got any hull shape restriction?

https://www.sail-world.com/Australia/Team-New-Zealand-reveals-total-commitment-to-the-Hula/-8282?source=google

Any prop diameter restrictions? Numbers of blades? (I would think a large slow turning 2 blade is optimimum for a Human powered sub but maybe depth/draft limits in area of operation). 

Is the sub a wet sub? With a dry sub I would think to use fins for lift instead of all the lift forces coming from the submerged shape buoyancy. (i.e. it sinks if you stop pedalling. Probably a safe rule would prohibit sinkers but can you ditch a n extra flotation volume once you get moving :) . Do you have to finish the race with the exact same sub you started with?

 




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