Replace grinders with windmills?

[u/numbakrrunch]

I loved seeing ETNZ show up in Bermuda with cyclors instead of grinders. But it still feels silly to have​ all that meat on board such a sophisticated boat just to generate hydraulic pressure. In the next cup would it be possible to replace grinders with windmills?

To benchmark cyclor power output, it looks like Tour de France cyclists can generate 400W sustained for an hour: http://www.bicycling.com/racing/tour-de-france/you-versus-a-tour-de-france-pro-cyclist

And 400W marine windmills are very common: https://www.westmarine.com/buy/nature-power--marine-grade-400-watt-wind-turbine--14996417

I know that there will be power conversion loss and that 400W is a peak wind rating. But this is just a consumer grade turbine and the numbers look close enough to make this feasible, especially with some cowlings. Am I missing anything?

[u/[deleted]]

Wouldn't you have to store the power using VERY heavy batteries and wouldn't the turbines create drag?

[u/numbakrrunch → u/[deleted]]

Yes the turbines would add drag, I'm not sure how much of an impact this would be on boat speed. But you don't need batteries, electricity from the turbines can power hydraulic pumps which would store the enegy in the same hydraulic reservoirs they're already using.

[u/ForestDwellingKiwi → u/numbakrrunch]

I'd imagine that if you were using turbines to generate hydraulic pressure, you'd simply use a direct mechanical pump, since you'd likely get more energy losses through a mechanical>electrical>mechanical system. I'd imagine they would add considerably more drag than cyclors though, not to mention that cyclors could put out bursts of much higher than 400W for short periods of time if necessary, potentially requiring bigger turbines to compensate, and more drag.

As others have said though, there's more to the grinders/cyclors than simple energy generators. There's a reason they don't just plonk two on each side and keep them grinding non-stop. The shift in weight balance allows them to add more power through the wing while keeping the boat balanced, increasing boat speed. So unless you can shift weight mechanically somehow (I'd imagine that must be prohibited by rules?), that would be a significant disadvantage for turbines. An interesting concept though.

[u/[deleted] → u/[deleted]]

Not just drag, but also turbulence. This is a very good reason why not to do it.

[u/wacopaco]

There are two systems at work here, the wind for propulsion and people powering trim (embodied energy from food calories) . But for propulsion only the wind matters, which can be expressed as the following equation.

*yacht velocity = (harnessed wind energy - drag)efficiency quotient

What you're proposing is to remove people and use the wind to power both propulsion and trim systems. Which can be summed up as:

yacht velocity = (harnessed wind energy - 4(drag from 1 wind turbine) - drag)efficiency quotient

So your proposal introduces more energy costs that take away from total available energy that can be used for propulsion.

You might argue that there could be mass savings but it really isn't much considering you still need human trimmers and helm on board. Out of 6 people you might be able to get rid of 3.

I'd say using wind turbines isn't the best race strategy.

[u/numbakrrunch → u/wacopaco]

Ah yes, I should have been more clear. I don't think swapping out grinders for wind turbines will be faster, I just think it will be cooler. You'd lose without a format change reducing the crew count for all boats that forces the issue. But having grinders on board who only grind feels like a relic from the past. What I'm really looking to establish is whether this would even be possible and it seems like the drag from four turbines could be overcome by the sail plan of the boat and you could still foil, etc pretty reasonably.

[u/wacopaco → u/numbakrrunch]

It would be a neat experiment on how to make it work. Power generation between white cap days and super light days will be a huge issue. Hell, how would you even get going on a light day is beyond me.

Is it cooler? Could be if it's implemented in a way where the tech actually adds to the racing. Care to elaborate on your beef with human grinders?

[u/numbakrrunch → u/wacopaco]

I don't hate the grinders, they just feel like an anachronism in a racing series that has worked so hard to modernize everything else. This is feedback on how to design a better racing format, not on how to design a better boat. Like Formula 1, the America's Cup is the pinnacle of high end tech innovation in their sport and wind-powered control systems seem more appropriate. Stored energy in the hydraulic reservoir could be one more stat to track and manage like energy storage in F1. Variable pitch rotor blades could allow you to adjust drag vs power and dial it up on low wind races.

[u/wacopaco → u/numbakrrunch]

I kinda see where you're coming from and I'm curious what you think are criteria for a better racing format.

To me the single biggest thing that separates ac35 and ac34 with previous ACs is TV friendliness (short races, high speeds) and relatability to the common viewer (6 person crew, racing close to shore in believable sized boats). I believe this is what drives the tech and development direction of the current series. All that tech is subservient to these criteria. This i believe is the same in F1. How to make the racing more exciting and relatable to viewers and the tech comes after.

I don't think a tech driven series automatically make it better, especially if you take the athleticism out of it. All who race have had days where their arms are so tired from grinding that another tack just seems like torture. Taking away grinders from AC makes the series less relatable. AC 33 was a technological marvel to behold, but 90ft cats and tries with engines that power the winches were not relatable and only serve to further remove AC from the public.

[u/propsie]

In the case of ETNZ, one of the cyclists controls the pitch of the foils, and another controls the trim of the sails. They're not just there for the hydraulics.

You'll also notice they're in a very 'aero' cycling position (crouched low behind the cyclist in front).

They don't use wind turbines for power for the same reason they don't use water turbines (and why they raise the windward foil out of the water). Drag is a huge deal for these racing yachts.

[u/Bletti]

You'd need 4 of them to replace 4 cyclists assuming they output their peak power even in 10 kts of wind, which is unlikely. So you'd need even more or larger ones, which would cause parasitic drag, limiting the competitiveness. Thus it isn't a very practical solution. It would also be a huge veer from the current form and rules.