Hull speed vs. wind speed

[elibobeli]

In general, does it take a wind speed, double that of hull speed to reach hull speed?  We are talking on a windward course for a displacement hull.

Another way of asking is how much wind does it take for a boat to reach hull speed?

I know each boat is different, and am not looking for specifics, just rule of thumbs if they exist.

I am thinking that a wind that is nearly overpowering the rig is just slightly more than is needed to maintain hull speed.  So does that mean that anything less just won't get you to hull speed?

Let's have it.

[Paul]

Elibobeli:

That's a good question.  I am curious as well.  Maybe someone who has a GPS could log some data and let us know.  You could set up parameters for an experiment and sail daily until all the conditions were met.

I've never seen any data out  there that suggests a percentage of wind will equal hull speed.  Probably too many parameters to control for to generalize for all boats.  IMHO, it would need to be set up for a specific model, dedicate which jib to use, and consider a foil rudder vs. a flat plate rudder.

Anyone out there have the time, tools, and desire to gather data?

[newt]

The question you guys are asking it too complex to narrow down a hull speed verus windspeed  formula. That is why we have speed radian diagrams for almost every type of boat. My CP-23 will reach hull speed when the wind is about 20knts and on my beam somewhere. I have a pretty much stock boat, with exception of a mid boom traveler.  And that is without to many swells.  It gets complex doesn't it?

[Bob23]

Newt:
   This isn't abut hull speed, but do you feel the mid-boom traveller system has been an improvement over the stock mainsheet setup? I've been considering this upgrade...whadayasay?
   I don't know of any formulas pertaining to hull speed and wind speed. There are way too many variables. Sometimes I spend too much time looking at instruments, analyzing, trimming this a bit and that a bit and I forGet why I'm there...to enjoy the wind in my face and feel the yacht move through the water...FUN!
   Bob23, on the hard in NJ

[newt]

Hi ya Bob!
What are you doing on the hard? Don't ya know boats float better in the water? But while you are there I would put in a midboom traveler. Over the top of the cabin would be my first choice, but mine is just aft of the slats for the cabin door- and it works great. BTw, since our boats are so small, just about any traveler will do. I gave away the last traveler from an old catalina I parted out. Just kinda look around, you should be able to pick one up cheap.

[Bob23]

What am I doing on the hard? Being bored to tears, that's what! I had rotator cuff surgery on 9/11 and I hauled out "Koinonia" early- August 5th, I think.
I'll look into the mid-boom traveler this winter. On another note, are you or anyone else planning to be at the show in Annapolis October 9-12, me thinks. If so, we should email cell phone numbers and plan a meet-up.
Whadayasay?
Bored23

[elibobeli]

Newt et al,

Alright, now I know that data does exist.  Now, how do I get it for my boat, an Eclipse.  I don't have wind speed indicator but do have a hand held GPS.  My dealer informed me that reefing time is about 18 knots, so I assume that is also the time I should be able to get hull speed.  I don't try to worry too much about boat speed, but as a new sailor, I do want to acheive the most from myself and the boat without trying to get milk from a turnip.

If I knew what to expect from the boat, then I could work toward those expectations.

Thanks for the input.

[newt]

Without trying to appear arrogant ( That is way  too easy for me to do) may I suggest that you should concentrate on sailing the boat, sail trim and getting yourself seaworthy. Speed will come later and is only part of the equation. It is the journey, man! Using your boat as a worthy tool for transport and enjoyment is far more important than speed. I am find much more fulfillment getting my boat into the slip on sail and oar in and hour than 5 minutes of motoring through the breakwater.
Now that said, I realize that I am a purist. I am the flyfisher that built his own flies, leader rod and reel. I teach desert survival to help kids experience life without anything, so I realize that I may be a bit far out on the curve.
But the more you sail- I think you will eventually agree- the more it touches your soul and not your GPS generated numbers.

[Bob23]

Well put, Newt!
   That is the main reason I chose not to race. I didn't want to get tricked into thinking of sailing in terms of points and seconds. Besides that, I don't enjoy loosing. Besides that also, I'm too much of a dreamer to bother with trying to beat someone around a mark...I just enjoy the feel of "Koinonia" and I moving over the water. Somehow, after a good day of sailing, the soul is refreshed.
   Bob23, dreaming.......................

[newt]

We going sailing one of these days Bob, just as soon as I make it to the east coast. You just craw on to your boat and hold your shoulder while you give the commands- I'll do the rest of it. Arrgg me mates!

[elibobeli]

Newt and Bob,

I posed a question and Paul wondered the same thing.  I never mentioned racing nor want to entertain the idea.  While I appreciate the suggestion, Newt, it doesn't help me with my answer.  When I first started fly fishing, I would ask what kind of fish were in a body of water, since throwing a bass fly to a brookie is a waste of time.  If someone were to have answered my question with "Man, don't worry about it, just enjoy casting and feel the rush of the river," I still woudn't know what kind of fish was in that body of water.  Had I thrown the bass bug repeatedly to the brookies (and not caught anything), I would have wondered if I was doing something wrong.  Yeh, I would have been doing something wrong.  I would have been trying to get milk from a turnip.  While it may be enjoyable to some to try to get milk from a turnip,  I would like to know that it could actually happen before trying. 

So does anyone want to discuss Hull speed vs. wind speed?  It may help me being a better seaman.

[kchunk]

Hull speed vs wind speed. IMHO, they're related but not directly. Some boats will obviously do better to windward/downwind than others. The sails you're using will greatly affect your downwind speed too, a spinnaker will get the boat downwind faster (approaching hull speed) in lighter wind than will a working jib. There are just too many variables to develop a rule of thumb.

I don't think there are too many things about sailing that you can apply a rule of thumb.

One thing's for sure, A downwind run with a following sea in this boat in a stiff breeze can be fun! The boat really keeps the captain on his toes. I love the feel of the tiller wanting to stall just before the boat rounds up. I've never rounded up unintentionally, but sometimes it feels like you're balancing on the head of a pin

[Bob23]

Eli:
   Sure didn't want to poke fun at your question with my philosophical view of sailing. I, too, like to sail in the most efficient manner; I think it's part of the fun! Probably the best thing is to know the hull speed of your vessel, use a GPS, and start experimenting.
   An interesting fact, my 1985 23/2 has a theoretical hull speed of about 6.02 knots yet we've sailed at 6.3. And I'm sure she'll go faster and we are not talking about 50 kt. winds here, just average sailing conditions maybe 20-30kts. How? Remember that theoretical hull speed takes no wind resistance into account and assumes a smooth underbody.
   I think our common goal is to ALL become better seamen. I just don't want to become a boring one, over-analyzing and missing the beauty and wonder of it all. Not infering that you are, of course.
   Milk from a turnip? Maybe it's me but I fail to see the correlation.
   Bob23, off to have a turnip milk and Black Goslings cocktail!

[Paul]

FWIW: I think one can study the parameters I outlined above and thoroughly enjoy the essence of sailing at the same time; the science of sailing and the spirit of sailing at the same time.  One only needs to have the tools and document the parameters while getting in that "sailing frame of mind."

This link might help.  Sail Boats

Check out the articles.  Also, check out "performance."

Peace and keep on enjoying the learning curve.

[Bob23]

To all:
   I found a lot of helpful calculations on www.sailingusa.info/
There is even a hull speed calculator for the math-challenged like myself.
Bob23, g'night!