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Race foil tuning warm vs cold water

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GuyinTCI
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Race foil tuning warm vs cold water

Postby GuyinTCI » Sat Jul 24, 2021 5:28 am

Hey guys i hope there are some experts here who can advise me on proper mast tuning for warm water. I know racing guys have different setups to be used with different water temperatures.

Im struggling to sustain speeds over 30 mph and would like to.

There seems to be a lack of literature on the subject matter any links of knowledge would be appreciated.

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Re: Race foil tuning warm vs cold water

Postby gmb13 » Sat Jul 24, 2021 11:27 am

GuyinTCI wrote:
Sat Jul 24, 2021 5:28 am
Hey guys i hope there are some experts here who can advise me on proper mast tuning for warm water. I know racing guys have different setups to be used with different water temperatures.

Im struggling to sustain speeds over 30 mph and would like to.

There seems to be a lack of literature on the subject matter any links of knowledge would be appreciated.
If you cannot sustain speeds over 30mph (26knots) with a Race Foil, the tuning is probably not the issue.
Can you give me some more info:

1) What foil are you on?
2) Does is feel draggy?
3) What tuning options does your foil have (Stab angle?)
4) Do you lack control over 30mph?

--
Gunnar

GuyinTCI
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Re: Race foil tuning warm vs cold water

Postby GuyinTCI » Sat Jul 24, 2021 4:40 pm

1) Spotz 2
2) it feels draggy at 26 knots, just not below
3) yes stab is adjustable currently at 2.9 degrees
4) yes it is harder to control but i assume it get twitcher the faster you go?

I bought this foil second hand years ago. The fuselage and front wind are epoxied together so there is no play there. i have over well 2,000 miles on this foil in this configuration, so if say its not set up right i would not be able to tell.

I assumed tuning because this foil was used in san fran which i understand to be cold water. I live in very warm waters.

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Re: Race foil tuning warm vs cold water

Postby tkaraszewski » Sat Jul 24, 2021 7:59 pm

GuyinTCI wrote:
Sat Jul 24, 2021 4:40 pm
i have over well 2,000 miles on this foil in this configuration, so if say its not set up right i would not be able to tell.
If you've always used it in this configuration how would you know if it had been set up wrong the whole time?

But Gunnar's probably right and I'd think it's something else. Can you easily break 30 mph on any other foil? What speeds are you hitting in what conditions, on what kite?

I've used my Mike's Lab Bullet 3 in San Francisco, the British Virgin Islands, and the Columbia River Gorge in both winter and summer, which covers both warm and cold and fresh and salt conditions with no dramatic difference in top speeds, without tuning it differently for the different conditions.

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Re: Race foil tuning warm vs cold water

Postby fluidity » Sun Jul 25, 2021 6:02 am

Second hand a couple of years ago??
All the good manufacturers are looking for and finding new edges to improve their products! I'm no speed expert but 3o mph on an old foil before the velocity^2 drag foils your attempts to go faster seems quite reasonable.
You will be looking for something that needs a bit of power and speed to lift you in the first place! Small area, well finished, thin vertical profile. Stabiliser proportionally smaller too, but longer fuselage to reduce twitchiness at speed.

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Re: Race foil tuning warm vs cold water

Postby gmb13 » Sun Jul 25, 2021 10:54 am

GuyinTCI wrote:
Sat Jul 24, 2021 4:40 pm
1) Spotz 2
2) it feels draggy at 26 knots, just not below
3) yes stab is adjustable currently at 2.9 degrees
4) yes it is harder to control but i assume it get twitcher the faster you go?

I bought this foil second hand years ago. The fuselage and front wind are epoxied together so there is no play there. i have over well 2,000 miles on this foil in this configuration, so if say its not set up right i would not be able to tell.

I assumed tuning because this foil was used in san fran which i understand to be cold water. I live in very warm waters.
Hi,

Ok. The Spotz 2 may not be the fastest anymore, but it can do more than 30 knots comfortanbly. 2.9 Stab angle is too much to go fast. Use max 1.5deg and adjust your stance accordlingly.

--
Gunnar

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Re: Race foil tuning warm vs cold water

Postby flying grandpa » Sun Jul 25, 2021 11:10 pm

Warm v cold water make a difference.
At 4 Celsius water has max density.
Also viscosity is almost 2 times higher than at 20C.

Both this factors increase substantially
dynamic forces ( lift- coused by underpressure) at given speed.

Unfortunately, surface tension that counteracts mast ventilation rise a little whith temperture drop.

In effect, we can expect increased mast ventilation tendency, but also lift increase substantially, prompting us to use smaller foils.

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Re: Race foil tuning warm vs cold water

Postby tkaraszewski » Mon Jul 26, 2021 4:18 am

flying grandpa wrote:
Sun Jul 25, 2021 11:10 pm
Warm v cold water make a difference.
At 4 Celsius water has max density.
Also viscosity is almost 2 times higher than at 20C.

Both this factors increase substantially
dynamic forces ( lift- coused by underpressure) at given speed.

Unfortunately, surface tension that counteracts mast ventilation rise a little whith temperture drop.

In effect, we can expect increased mast ventilation tendency, but also lift increase substantially, prompting us to use smaller foils.
Water at 21 degrees has 99.8% the density of water at 4 degrees. It’s not exactly a monumental difference.
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Schietwedder
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Re: Race foil tuning warm vs cold water

Postby Schietwedder » Mon Jul 26, 2021 9:01 am

But viscosity does as flying grandpa writes.
Ask someone at a towing tank for ships why they measure the temperature so accurately. Even if the density doesn't change much, the viscous effects change massively in summer and winter or even morning/afternoon between some test runs and therefore need to be corrected to be comparable in case of a towing tank.

That this effects foils and their development also, no question! At what rider level you are able to experience this, I don't know.

As Gunnar writes here it is probably more a setup issue.
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tkaraszewski
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Re: Race foil tuning warm vs cold water

Postby tkaraszewski » Mon Jul 26, 2021 4:15 pm

Schietwedder wrote:
Mon Jul 26, 2021 9:01 am
But viscosity does as flying grandpa writes.
Ask someone at a towing tank for ships why they measure the temperature so accurately.
Why don't you give me a link to some info instead of asking me to talk to a person I don't know? Where's the evidence that the viscosity change in water temp between 10 and 30 degrees C affects lift enough that you'd want to use a smaller foil in colder water? The density of water barely changes. The viscosity changes more but it's not clear to me that this will cause "lift increase substantially". Can you explain how that works or link me to something that does?


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