Heavy sailboats are slower and

[a64pilot]

Originally Posted by Dockhead

Well, 2 knots more than 5.5 knots is 36%. 5.5 knots and 7.5 knots is totally different. It means 180 miles a day instead of 132 miles.





And yes, like you, I also like a beam reach in 15 knots. Who the hell doesn't?



I have been loving the Baltic this summer, which unlike my usual stomping grounds in the Northern parts of the Atlantic Ocean, has been serving up balmy sunny days and Force 4's and flat seas day after day after day. I'm starting to forget what a F8 is like.



I might even need to break out the Big Jib.

I guess my point is that you can spend shed loads of money and stress and work for those two kts, or you can sit back and enjoy life.
I’m the type that trims their sails a little tighter than optimum, so that I don’t have to mess with them, some however are trimming every 15 min, and watching the tell tales the whole time, I sit back and read a book and relax.
If I wanted to go fast I would have stayed with power, and kept my job to pay the fuel bill.
I have gotten lazy and not so much in a hurry, so I give up 30 miles a day. I gain a relaxed way of life.
Of course I knowingly, intentionally sought a comfortable boat over a fast boat, and one I could buy and Retire.

To me, that extra 35 miles a day isn’t worth spending loads more money on, or lots of extra work.

I think most Mom and Pop cruising teams have adopted the thought process of we will get there, when we get there.

[boatman61]

Originally Posted by a64pilot

I guess my point is that you can spend shed loads of money and stress and work for those two kts, or you can sit back and enjoy life.
I’m the type that trims their sails a little tighter than optimum, so that I don’t have to mess with them, some however are trimming every 15 min, and watching the tell tales the whole time, I sit back and read a book and relax.
If I wanted to go fast I would have stayed with power, and kept my job to pay the fuel bill.
I have gotten lazy and not so much in a hurry, so I give up 30 miles a day. I gain a relaxed way of life.
Of course I knowingly, intentionally sought a comfortable boat over a fast boat, and one I could buy and Retire.

To me, that extra 35 miles a day isn’t worth spending loads more money on, or lots of extra work.

I think most Mom and Pop cruising teams have adopted the thought process of we will get there, when we get there.

Best way to cruise..
That extra knot or so is for the day trippers to scratch for.

[Smokeys Kitchen]

Originally Posted by wingssail

1.3 * (SQRT LWL)

If you make it longer (aircraft carriers) that formula still holds.

If it is underwater (submarine) some other formular might apply

A planning hull is not subject to this formula

I do not believe that holds true all the time. I had a friend stationed on a Nimitz class carrier (1092 feet) and watched the speed trials going on. When the speed hit 55 the reporting screens went blank - and he felt the speed still increasing.

Not my experience, but someone I trust. Perhaps some experienced Navy personal can "weigh" in.

[Boatyarddog]

Originally Posted by hamburking

I think the OP has oversimplified.

For example, a "heavier" boat can have more sail area, which really helps in light winds.

And a "lighter" boat may be too tender to go out at all in big seas or big winds. It can also lack the power to punch into big seas/winds when going upwind.

And of course the most important thing in sailing....the sailor. A good sailor can make any boat go. And a poor sailor can make any boat slow.

I owned a "heavy" 1972 Pearson 30. And it was quite fast.

Every boat is a compromise. Every boat has its own strengths and features. And for every "rule" there is an exception.

I don't agree that a Pearson 30 is considered a heavy boat.
It's only 8300+ lbs.
And a fin keel.
What do you consider heavy?
SV Cloud Duster

[CarinaPDX]

Originally Posted by Smokeys Kitchen

I do not believe that holds true all the time. I had a friend stationed on a Nimitz class carrier (1092 feet) and watched the speed trials going on. When the speed hit 55 the reporting screens went blank - and he felt the speed still increasing.

You don't understand the concept of hull speed. It is not a brick wall. If you looked at a graph of power versus speed for any displacement vessel you would notice a roughly linear increase of both, out to a point near "hull speed", where the power curves up (i.e. it takes more power for incremental speed increases). If you have massive sources of power from a nuclear reactor an aircraft carrier or submarine can be pushed to much higher speeds than the hull speed - it is just highly inefficient.

Greg

[boatman61]

Originally Posted by CarinaPDX

You don't understand the concept of hull speed. It is not a brick wall. If you looked at a graph of power versus speed for any displacement vessel you would notice a roughly linear increase of both, out to a point near "hull speed", where the power curves up (i.e. it takes more power for incremental speed increases). If you have massive sources of power from a nuclear reactor an aircraft carrier or submarine can be pushed to much higher speeds than the hull speed - it is just highly inefficient.

Greg

Then why was my Hurley 22 nearly burying its bow as it reached 8kts and I had to keep spilling wind from the genny to keep from going under.. or does it only not apply if the thrust is from an engine at the back.

[Adelie]

Originally Posted by CarinaPDX

You don't understand the concept of hull speed. It is not a brick wall. If you looked at a graph of power versus speed for any displacement vessel you would notice a roughly linear increase of both, out to a point near "hull speed", where the power curves up (i.e. it takes more power for incremental speed increases). If you have massive sources of power from a nuclear reactor an aircraft carrier or submarine can be pushed to much higher speeds than the hull speed - it is just highly inefficient.

Greg

The hull speed for a Nimitz is around 40-44kt. Given that they are very narrow for length (near 10:1) the increased resistance due to wave making above hull speed is a lot more moderate than a normal pleasure sailboat that is near 3:1 length to beam. And the nukes have a lot of spare power.

Submarines are not subject to wave making resistance and therefore do not have a hull speed when submerged.

[Boatyarddog]

Originally Posted by boatman61

Then why was my Hurley 22 nearly burying its bow as it reached 8kts and I had to keep spilling wind from the genny to keep from going under.. or does it only not apply if the thrust is from an engine at the back.

IMO
Probably to much weight in front.
That's a tiny boat.
It's going to react to everything.
Move ballast around.
I bet your Genny is 150% or better.
SV Cloud Duster

[CarinaPDX]

Originally Posted by boatman61

Then why was my Hurley 22 nearly burying its bow as it reached 8kts and I had to keep spilling wind from the genny to keep from going under.. or does it only not apply if the thrust is from an engine at the back.

I'm not sure how that relates to hull speed, other than both are a result of the bow and stern waves created. The bow going under is more a function of buoyancy, and especially reserve buoyancy. Raise the freeboard at the bow, or make the bow fuller, and she won't go under as easily - but the hull speed isn't going to change a lot unless you change the underwater length and/or shape.

It doesn't matter the source of the power, however by heeling the boat the underwater shape and often the LWL is changed, and the effect of the location of the reserve buoyancy might come into play.

Greg

[a64pilot]

Originally Posted by Adelie

Submarines are not subject to wave making resistance and therefore do not have a hull speed when submerged.

I have never set foot on a sub, but have wondered what their theoretical top speed could be. I assume of course they never do that cause they would be both blind and as noisy as a threshing machine, and that their prop is likely optimized for lack of noise and not speed anyway.
I have heard that on an attack boat the Capt gets to chose the type of prop?
But I have wondered if cavitation of the prop is the limiting factor and that maybe if they were real deep, that cavitation at extreme pressure just didn’t happen?

A Russian Alpha was a very, very fast boat?

Oh and I believe that well before WWII a French Destroyer blew through 40 kts, so that had to be well beyond hull speed, but maybe their hull is so narrow that hull speed isn’t nearly as restrictive?

[boatman61]

Originally Posted by Boatyarddog

IMO
Probably to much weight in front.
That's a tiny boat.
It's going to react to everything.
Move ballast around.
I bet your Genny is 150% or better.
SV Cloud Duster

The only ballast was in the keel apart from a Honda 5 in a well at the stern, some clothes food, water and me.
I thought it was common knowledge that non planing hulls have a tendency to start burying their hulls as their speed goes past hull limits..
And yes it was a No 1 jib with reefed main running before 30kts into La Coruna with a short breaking following sea.
If the bow had gone those extra 6inches I would have pitchpoled.. and likely not be here writing about it.
She does displace 4000lbs.. 2300 in balllast.

[Adelie]

Originally Posted by a64pilot

I have never set foot on a sub, but have wondered what their theoretical top speed could be. I assume of course they never do that cause they would be both blind and as noisy as a threshing machine, and that their prop is likely optimized for lack of noise and not speed anyway.
I have heard that on an attack boat the Capt gets to chose the type of prop?
But I have wondered if cavitation of the prop is the limiting factor and that maybe if they were real deep, that cavitation at extreme pressure just didn’t happen?

A Russian Alpha was a very, very fast boat?

Oh and I believe that well before WWII a French Destroyer blew through 40 kts, so that had to be well beyond hull speed, but maybe their hull is so narrow that hull speed isn’t nearly as restrictive?

Ultimate speed of a sub is limited by available power, surface area, hull shape, prop shape and depth.

At high speed cavitation of the prop become a problem that is moderated by going deeper. Cavitation is a problem both because it generates noise but also because the prop becomes less effective in propelling the boat.

The Russian Alphas were very fast at the cost of being noisy. They were built with titanium hulls and Lead-Bismuth cooled reactors which were smaller and lighter for their power output.

[Boatyarddog]

Originally Posted by boatman61

The only ballast was in the keel apart from a Honda 5 in a well at the stern, some clothes food, water and me.
I thought it was common knowledge that non planing hulls have a tendency to start burying their hulls as their speed goes past hull limits..
And yes it was a No 1 jib with reefed main running before 30kts into La Coruna with a short breaking following sea.
If the bow had gone those extra 6inches I would have pitchpoled.. and likely not be here writing about it.
She does displace 4000lbs.. 2300 in balllast.

Humm.. Just over 50% in the keel would make it a bit on the tender side.
Tall mast or ? Good you were reefed.
IMO you were overpower at the wind speed and sail area, for the almost equal displacement weight to ballast in the keel ratio.
That makes where your movable ballast goes very critical.

[barnakiel]

Originally Posted by Adelie

Ultimate speed of a sub is limited by available power, surface area, hull shape, prop shape and depth.

At high speed cavitation of the prop become a problem that is moderated by going deeper. Cavitation is a problem both because it generates noise but also because the prop becomes less effective in propelling the boat.

The Russian Alphas were very fast at the cost of being noisy. They were built with titanium hulls and Lead-Bismuth cooled reactors which were smaller and lighter for their power output.

Good you chimed in I was wondering the same thing too.


How fast are the faster nuclear subs, do you happen to know?


I have read last week that the Ruski nuclear TORPEDOES can go at 100 knots. Later read a corrected info that closer to like 50 knots.


When they are in the silent mode sneaking silently towards New York, they go at only 2-3 knots - as discussed above for noise reasons.


Interestingly, they go shallow - some 100m - apparently going deeper cause more echo from the bottom.


I wonder how fast the fastest subs go, I bet it is mostly the structural limit due to strain from speed that limits them.


?


b.

[boatman61]

Oh there was to much sail up, but with the short breaking seas I felt if I tried turning into wind to drop the sail and hank on a No3 I'd have broached in the attempt and I did not have 100% confidence the TP would hold her steady long enough with the occasional left over cross sea if I tried it on the run.. so I played spill the jib instead.
It worked..

https://sailboatdata.com/sailboat/hurley-22