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Apologize for the highjack so this is the last on this subject. Will use situations you may find yourself in and wish to avoid.
You’re on a ball facing a strong current in a active traffic river. Power up to ball and release the pendant. Make a 90 degree turn and are swept down stream but you have movement forward so you are moving across the current flow so have water flow past the rudder. But when you turn totally downstream between windage of your house and current there’s no water movement going past the rudder(s). Yes you’re moving fast downstream but you’re stationary in the water column so no steerage. Same thing happens surfing in waves if between wind and gravity as you descend down the wave you are moving at the same speed as the wave. Usually because of gravity you are moving faster than the wave so there’s some movement of water past the rudder. it’s much less and steering is mushy and not that effective. But sometimes there’s no movement and no steerage.
Also a screw spinning in a fluid with have no load (so no propulsive force) if it is spinning at rate that produces the same rate of flow as the column of water is already flowing at. It must either spin faster to exhaust water behind it and produce propulsion or slower and produce drag. If you have a old school speedo think of the paddles. They are rotating at just about your speed through the water ( frictional losses aside). Think of your prop if it was freewheeling it would spin at a certain rpm depending upon boat speed through the water. Now if your prop is spinning at that rpm it wouldn’t be loaded at all. Usually engines transmissions and propeller(s) are set up this doesn’t happen. The load on the propulsion system decreases but some remains even going downstream. You may be going fast but actually slowly or even not at all through the water column. Again current, wind resistance and gravity can combine to produce enough propulsive force to match the propulsive force the engine should be producing so there’s no load at all on the prop. Yes it’s unusual but does occur. More commonly wash coming off the prop decreases. If that wash is aimed at your rudder that contribution to water flow past your prop decreases and steering will be less crisp. All this underlies the reason for the colreg rules. Think many of us have experienced occasions when this was quite obvious and potentially dangerous.
Think you know this intuitively but unless you have torque sensors on your shafts measuring load there or shaft HP and comparing it to SOG, speed through the water, RPM you don’t think about it. Similarly look at the rudder angle indicator going downwind and with the wave train and compare it to upwind when on a no drift AP setting. AP works less (lower forces) downwind down seas than up but course corrections are larger. There’s less movement of water past the rudder going down than up although your SOG maybe higher. It’s obvious on mechanical linkage steering but not so much on hydraulic or other systems with less “feel” that load on the rudder(s) decreases when going with the flow.
For the first time I’m on a SD hull. Compared to before the ability to nearly always be able to power up and not be in the ranges where the above is much of a concern is liberating. But it is for underpowered FD hulls and can be for SD hulls in surfing conditions.
 
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Hippocampus said:
Apologize for the highjack so this is the last on this subject. Will use situations you may find yourself in and wish to avoid.
You’re on a ball facing a strong current in a active traffic river. Power up to ball and release the pendant. Make a 90 degree turn and are swept down stream but you have movement forward so you are moving across the current flow so have water flow past the rudder. But when you turn totally downstream between windage of your house and current there’s no water movement going past the rudder(s). Yes you’re moving fast downstream but you’re stationary in the water column so no steerage. Same thing happens surfing in waves if between wind and gravity as you descend down the wave you are moving at the same speed as the wave. Usually because of gravity you are moving faster than the wave so there’s some movement of water past the rudder much it’s much less and steering is mushy and not that effective. But sometimes there’s no movement and no steerage.
Also a screw spinning in a fluid with have no load (so no propulsive force) if it is spinning at rate that produces the same rate of flow as the column of water is already flowing at. It must either spin faster to exhaust water behind it and produce propulsion or slower and produce drag. Usually engines transmissions and propeller(s) are set up this doesn’t happen. The load on the propulsion system decreases but some remains. Again current, wind resistance and gravity can combine to produce enough propulsive force to match the propulsive force the engine should be producing so there’s no load at all on the prop. Yes it’s unusual but does occur. More commonly wash coming off the prop decreases. If that wash is aimed at your rudder that contribution to water flow past your prop decreases steering will be less crisp. All this underlies the reason for the colreg rules.
Think you know this intuitively but unless you have torque sensors on your shafts measuring load there or shaft HP and comparing it to SOG, speed through the water, RPM you don’t think about it. Similarly look at the rudder angle indicator going downwind and with the wave train and compare it to upwind when on a no drift AP setting. AP works less (lower forces) downwind down seas than up but course corrections are larger. There’s less movement of water past the rudder going down than up although your SOG maybe higher. It’s obvious on mechanical linkage steering but not so much on hydraulic or other systems with less “feel”.
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This sounds like a sailboat with small propeller issue.

In your analogy, when I motor up current to the pendant, I have speed through the water, which is different than speed across the bottom, because of the current. When I turn to cross the current, I still have that same speed though the water, but speed across the bottom has increased as I'm not going into the current. When I turn down current, speed through the water is still the same, but speed across the bottom is now faster than through the water because of the current. In all directions, the through the water speed hasn't changed, and steering is relatively unaffected because of my 28" propeller and 36" x 24" rudder.

Ted
 
O C Diver said:
This sounds like a sailboat with small propeller issue.

In your analogy, when I motor up current to the pendant, I have speed through the water, which is different than speed across the bottom, because of the current. When I turn to cross the current, I still have that same speed though the water, but speed across the bottom has increased as I'm not going into the current. When I turn down current, speed through the water is still the same, but speed across the bottom is now faster than through the water because of the current. In all directions, the through the water speed hasn't changed, and steering is relatively unaffected because of my 28" propeller and 36" x 24" rudder.

Ted
Click to expand...

Agreed. The prop and rudder only feel how fast the boat is moving through the water. They don't know if the water is also moving or not.

The following seas example has no relation to a steady current, as in a strong following sea the water under the boat can momentarily reverse because the water is able to change speed much faster than the boat can.
 
Greetings,

Mr. HT...


iu
 
rslifkin said:
Agreed. The prop and rudder only feel how fast the boat is moving through the water. They don't know if the water is also moving or not.

The following seas example has no relation to a steady current, as in a strong following sea the water under the boat can momentarily reverse because the water is able to change speed much faster than the boat can.
Click to expand...

Still think it depends on your boat's propeller and rudder. There's a difference between momentum and drive. A planing hull can cruise in a following sea until it plows into a wave ahead of it or drops off the face and starts to turn. It looses its momentum and the propeller cavitates because it can't immediately drive it up on plane. A displacement hull with a small propeller can also have that problem as it looses momentum as the propeller cavitates.

A displacement vessel with a large enough propeller moves through the water with drive and some momentum. As a result, when the wave goes under the boat from the stern, there is minimal cavitation and the propeller is still throwing water at the rudder.

In my boat, going down Delaware bay in 4 to 5' following seas, I can comfortably run on autopilot. The autopilot is working harder and faster, but there's no loss of steering.

I certainly couldn't do that on my 15 knot Downeaster charter boat. When passing over waves, the autopilot couldn't react fast enough when dropping off the front of the wave and risk falling off plane from loss of momentum.

Ted
 
O C Diver said:
Still think it depends on your boat's propeller and rudder. There's a difference between momentum and drive. A planing hull can cruise in a following sea until it plows into a wave ahead of it or drops off the face and starts to turn. It looses its momentum and the propeller cavitates because it can't immediately drive it up on plane. A displacement hull with a small propeller can also have that problem as it looses momentum as the propeller cavitates.

A displacement vessel with a large enough propeller moves through the water with drive and some momentum. As a result, when the wave goes under the boat from the stern, there is minimal cavitation and the propeller is still throwing water at the rudder.

In my boat, going down Delaware bay in 4 to 5' following seas, I can comfortably run on autopilot. The autopilot is working harder and faster, but there's no loss of steering.

I certainly couldn't do that on my 15 knot Downeaster charter boat. When passing over waves, the autopilot couldn't react fast enough when dropping off the front of the wave and risk falling off plane from loss of momentum.

Ted
Click to expand...

Agreed, some boats will be harder to handle in various conditions than others. And something with a small prop like a sailboat might take a little longer to build speed through water when turning away from the mooring in that example (and will have prop wash over less than the whole rudder), so steerage may be poor for the first few seconds.

As far as running in a following sea, big props and rudders absolutely help to maintain steerage at low speeds. My boat is pretty good about it, but not perfect, especially with the big, flat transom. When I add an autopilot it will need a decent size pump to move the rudders fast enough to not yaw all over the place at 6.5 kts in a following sea. On plane in 3 - 4 foot following seas (even the steep crap we get in the Great Lakes), it's pretty much 1 finger steering and effortless powered and trimmed for 16 - 17 kts. The bow is pretty full, so it doesn't try to stuff unless you trim it way too far down. Chug up the back side of the wave at 13 - 14 kts, make a slight steering correction over the top of the wave and surf down the front at 18 - 20 kts. Autopilot would have an easy time with that. The limitation would be when you can't climb the back side of a wave due to size and steepness slowing you down too much. Then it's time to just slow down and pace them, but I haven't seen that happen. It helps that for a planing boat, I have reasonably big props and rudders compared to many of similar size and speed.
 
Broke my promise.
Yes totally agree. You need speed through the water for the rudder to work. Yes totally agree in the vast amount of circumstances you have that. Don’t agree that’s always the case. Continue to think a strong current means even when you have enough speed through the water to maintain steerage you may have traveled enough distance downstream during a turn to make navigation difficult.
There’s a small marina on the Hudson River side of the tip of Manhattan. If going downstream at the peak of current you need to line things up well in advance and be spot on at the entrance. Going upstream it’s a piece of cake. In a SD hull going either way ain’t a biggie but in a FD hull a downstream approach is. Same in some rivers if you want to miss rocks and islands. You travel longer distances or need a greater rudder angle to get the same effect. Surfing in a displacement hull even with power on you can get no helm or minimal impact. Been there so what’s above doesn’t convince me otherwise. Normally you surf at a faster speed than the wave is moving but if you don’t things can match and steering suffer. This is independent of extreme heel. The more horizontal the rudder is the less effective it is steering. That effect maybe a more common reason for a broach with loss of steering but isn’t what I was talking about.
 
This could be the biggest thread drift ever, as we all drift downstream and try to steer back on course. The funny part is everyone is mostly agreeing with each other but saying it in differnt ways. Carry on!
 
Hippocampus said:
Continue to think a strong current means even when you have enough speed through the water to maintain steerage you may have traveled enough distance downstream during a turn to make navigation difficult.
Click to expand...

That's the key. It's not that you don't have steerage, but that you have to account for the distance you'll be pushed sideways in a turn when trying to make a turn in a strong current. Knowing where to aim the boat becomes unintuitive in a strong current even though the boat is responding fine.
 
Yup . We followed a N40 out of Portsmouth NH. Had been raining heavily for several weeks before (finally stopped) and a king tide. Lots of traffic on the river. Both of us left on the ebb. Both of us were very busy at the wheel. We chatted on the VHF after gaining open ocean. We agreed for FD hulls will pay more attention to the current before leaving. It isn’t just a sailboat thing.
 
HTurner said:
To get back on topic... here is something interesting:


https://www.yachtworld.com/yacht/2003-custom-townsend-motorsailor-8258775/
Click to expand...

Thanks for posting this interesting boat…..
She was moored at the foot of my dock at Elliott Bay for the ten years I was there and as far as I know, never left her birth until last Summer about this time when she went to the yard. Likely to get cleaned up for this sale apparently.
They call her a Townsend Bay 50. She suffers from a very low L/B so unlikely to be fast nor efficient. She has the sails and paravanes but based on the shape of her bottom I expect she could still roll the eyes right out of your head.
She caught my eye immediately 11 years ago based on a bit of a salty look for sure, but based on what I have come to think about boats and hull forms over the ensuing time, I would have to say, “no thanks”.
Nice interior though….
 
klee wyck said:
Thanks for posting this interesting boat…..
She was moored at the foot of my dock at Elliott Bay for the ten years I was there and as far as I know, never left her birth until last Summer about this time when she went to the yard. Likely to get cleaned up for this sale apparently.
They call her a Townsend Bay 50. She suffers from a very low L/B so unlikely to be fast nor efficient. She has the sails and paravanes but based on the shape of her bottom I expect she could still roll the eyes right out of your head.
She caught my eye immediately 11 years ago based on a bit of a salty look for sure, but based on what I have come to think about boats and hull forms over the ensuing time, I would have to say, “no thanks”.
Nice interior though….
Click to expand...


Thanks, it is always nice to get "the rest of the story," as they say, or at least a bit more of the story.
 
Wasn`t Merlin a Rolls Royce brand? Try boatdiesel.
 
The Steeler 61 looks pretty good. Finally we're seeing more and more electric /hybrid boats! I'd prefer it with ALU though.
 
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healhustler said:
Always thought highly about the Vega. I prefer sans the flybridge, one of most balanced looking vessels ever, rugged & efficient.
Click to expand...

Larry I agree .. predictably.
I think all stock Willard pleasure boats are Vegas. 30, 36 and 40’.
But I can’t remember exactly what the “Vega” stands for?
 
Nomad Willy said:
Larry I agree .. predictably.
I think all stock Willard pleasure boats are Vegas. 30, 36 and 40’.
But I can’t remember exactly what the “Vega” stands for?
Click to expand...


I always thought Vega referred to Vega the star, one of the five brightest stars. The star logo can be found on the bows of Willards and on the main sail of my Willard Horizon.
 
Vega (n.)
1638, bright northern star, the alpha of Lyra, from Arabic (Al Nasr) al Waqi translated variously as "the eagle of the desert" or "the falling vulture" (or bird).
 
Or maybe they were referencing this bad boy?[emoji51]

IMG_4800.jpg
 
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