Front page- tanker with wing sails

Spin Echo

Anarchist
654
2
The latest design update includes lifting foils.

Picture1f.png

 

bgytr

Super Anarchist
5,076
681
Dunno, it might really work??

Naw....

As a nav. arch. student, I did a thesis paper on wind assist for commercial ships. Basically the price of fuel needs to be so high for it to work that it is not feasible.

Also, tankers routinely take green water over the deck. Those little sails would have to be pretty dern heavy to stand up to that. And just everyday industrial conditions on a tanker are pretty friggin rough. Maiteneance costs of another system onboard- not reasonable.

A simple computation... under ideal beam apparent wind at 20 knots...

assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2

lift= 0.5 r*v^2*A*C

C: lift coefficient (give a fairly generous C of 2.0)

r: air density taken as 0.0023769 slug/ft^3

v: 20 knots = 33.8 ft/s

A: area = 1600 ft^2

force from one sail = 4300 lb of thrust per sail. x 20 sails = 86000 lb of thrust.

A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust.

multiply the sail thrust by about .7 since the leeward sails will be in the wash of the windward sails => 60,000 lbs of sail thrust under ideal conditions.

60,000 / 1,500,000 = 0.04, or a 4% thrust benefit. Not worth it when you factor the drag under headwind conditions, maintenance costs, weight, etc. And that calc was for pretty much ideal circumstances. Actual thrust benefit under a range of conditions would be way less.

 

SF Woody Sailor

Super Anarchist
1,112
394
Dunno, it might really work??

Naw....

As a nav. arch. student, I did a thesis paper on wind assist for commercial ships. Basically the price of fuel needs to be so high for it to work that it is not feasible.

Also, tankers routinely take green water over the deck. Those little sails would have to be pretty dern heavy to stand up to that. And just everyday industrial conditions on a tanker are pretty friggin rough. Maiteneance costs of another system onboard- not reasonable.

A simple computation... under ideal beam apparent wind at 20 knots...

assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2

lift= 0.5 r*v^2*A*C

C: lift coefficient (give a fairly generous C of 2.0)

r: air density taken as 0.0023769 slug/ft^3

v: 20 knots = 33.8 ft/s

A: area = 1600 ft^2

force from one sail = 4300 lb of thrust per sail. x 20 sails = 86000 lb of thrust.

A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust.

multiply the sail thrust by about .7 since the leeward sails will be in the wash of the windward sails => 60,000 lbs of sail thrust under ideal conditions.

60,000 / 1,500,000 = 0.04, or a 4% thrust benefit. Not worth it when you factor the drag under headwind conditions, maintenance costs, weight, etc. And that calc was for pretty much ideal circumstances. Actual thrust benefit under a range of conditions would be way less.
You sounds like you know what you are talking about so you are probably on the wrong website.

 

nolatom

Super Anarchist
3,679
699
New Orleans
Is a beam reach the ideal, or would a run or near-run be? Maybe less self- blanketing that way (though more from the accommodation house). And crank the windspeed up to 30?

I'm an English major so obviously I would know.

If it could get up nearer to a 10% thrust benefit, industry might take notice in times of much higher fuel costs. But I bet the deck officers would hate all the sticks and sails for visibility-ahead reasons. Plus the maintenance headaches.

 
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2,689
0
Many variations of this have been pumped out in recent years. Another reason they don't work is Philippino deckies make crap mainsail trimmers.

Just reading it again, it claims SAVINGS of $60m a year in fuel costs, when a conventional

Ship would spend less than $10m TOTAL for fuel in a year. Too many other wild cleans to mention.

The biggest question is, what's it rate?

 
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P_Wop

Super Anarchist
7,134
4,293
Bay Area, CA
Back when I was working with Dave at KiteShip (2006) we did these analyses as well. A big (75,000ft2/7,500m2) helium-stabilized traction kite was by far the most efficient way of providing additional power to slow VLCCs, especially on the mostly downwind run from Venezuela to Galveston Bay, or California to Hawai'i, developing sometimes up to 50% fuel savings. The multiple-mast soft/hard sail option just wasn't a contender.

But in the end, neither were we.

Ship owners hate complexity and added risk. Ship masters hate it even more. The idea of having to look out the windows at something complex, fragile and different was a complete deal-killer. Pass the increased fuel costs to the customer every time, in the way of increased freight charges. A no-brainer.

All this is wonderful in theory, but it's a technology without a paying market. And that's no way to run a business.

 

LeeJerry

Anarchist
939
0
Gulf Coast
Dunno, it might really work??

Naw....

As a nav. arch. student, I did a thesis paper on wind assist for commercial ships. Basically the price of fuel needs to be so high for it to work that it is not feasible.

Also, tankers routinely take green water over the deck. Those little sails would have to be pretty dern heavy to stand up to that. And just everyday industrial conditions on a tanker are pretty friggin rough. Maiteneance costs of another system onboard- not reasonable.

A simple computation... under ideal beam apparent wind at 20 knots...

assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2

lift= 0.5 r*v^2*A*C

C: lift coefficient (give a fairly generous C of 2.0)

r: air density taken as 0.0023769 slug/ft^3

v: 20 knots = 33.8 ft/s

A: area = 1600 ft^2

force from one sail = 4300 lb of thrust per sail. x 20 sails = 86000 lb of thrust.

A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust.

multiply the sail thrust by about .7 since the leeward sails will be in the wash of the windward sails => 60,000 lbs of sail thrust under ideal conditions.

60,000 / 1,500,000 = 0.04, or a 4% thrust benefit. Not worth it when you factor the drag under headwind conditions, maintenance costs, weight, etc. And that calc was for pretty much ideal circumstances. Actual thrust benefit under a range of conditions would be way less.
I have a couple comments on your calculations:

"assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2"

They state 5000 sq m, which is almost 2700 sq ft per sail. So the force from one sail (using all of your other assumptions) then becomes over 7200 lb, and for 20 sails is almost 145,000 lb. Applying your 0.7 correction for “efficiency” results in about 100,000 lb of total thrust from the sails.

"A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust."

You don’t define this power, but since very few (actually no one) talk about effective power, it is reasonable to assume that this is brake power. Thus we need to apply a propulsive coefficient (efficiency) when calculating the thrust produced, which you seem to have missed. Using a generous 0.667, we then get => 1.0 million lb of thrust (resistance).

However, they claim typical power is half of your value: 30 MW = 40,230 hp. So now the total thrust / resistance is => 500,000 lb.

"60,000 / 1,500,000 = 0.04, or a 4% thrust benefit."

100,000 / 500,000 = 0.20, or 20% benefit.

They then claim further resistance reduction (required thrust) from “previous” ships through other means such as higher length-to-beam ratio and air lubrication of the hull. So the 500,000 lb resistance number goes down and the percentage obtained from the sails will be even higher (at least for this ideal case).

I'm not saying it's feasible...

 

bgytr

Super Anarchist
5,076
681
Dunno, it might really work??
Naw....

As a nav. arch. student, I did a thesis paper on wind assist for commercial ships. Basically the price of fuel needs to be so high for it to work that it is not feasible.

Also, tankers routinely take green water over the deck. Those little sails would have to be pretty dern heavy to stand up to that. And just everyday industrial conditions on a tanker are pretty friggin rough. Maiteneance costs of another system onboard- not reasonable.

A simple computation... under ideal beam apparent wind at 20 knots...

assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2

lift= 0.5 r*v^2*A*C

C: lift coefficient (give a fairly generous C of 2.0)

r: air density taken as 0.0023769 slug/ft^3

v: 20 knots = 33.8 ft/s

A: area = 1600 ft^2

force from one sail = 4300 lb of thrust per sail. x 20 sails = 86000 lb of thrust.

A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust.

multiply the sail thrust by about .7 since the leeward sails will be in the wash of the windward sails => 60,000 lbs of sail thrust under ideal conditions.

60,000 / 1,500,000 = 0.04, or a 4% thrust benefit. Not worth it when you factor the drag under headwind conditions, maintenance costs, weight, etc. And that calc was for pretty much ideal circumstances. Actual thrust benefit under a range of conditions would be way less.
I have a couple comments on your calculations:

"assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2"

They state 5000 sq m, which is almost 2700 sq ft per sail. So the force from one sail (using all of your other assumptions) then becomes over 7200 lb, and for 20 sails is almost 145,000 lb. Applying your 0.7 correction for efficiency results in about 100,000 lb of total thrust from the sails.

"A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust."

You dont define this power, but since very few (actually no one) talk about effective power, it is reasonable to assume that this is brake power. Thus we need to apply a propulsive coefficient (efficiency) when calculating the thrust produced, which you seem to have missed. Using a generous 0.667, we then get => 1.0 million lb of thrust (resistance).

However, they claim typical power is half of your value: 30 MW = 40,230 hp. So now the total thrust / resistance is => 500,000 lb.

"60,000 / 1,500,000 = 0.04, or a 4% thrust benefit."

100,000 / 500,000 = 0.20, or 20% benefit.

They then claim further resistance reduction (required thrust) from previous ships through other means such as higher length-to-beam ratio and air lubrication of the hull. So the 500,000 lb resistance number goes down and the percentage obtained from the sails will be even higher (at least for this ideal case).

I'm not saying it's feasible...
ya, I eyeballed the sail size by estimating the mast height from the ht of the deckhouse, maybe I underestimated a bit. But HP I estimated as power at the props, so maybe your cut down factor is a little much on the power.

The air lubrication thing is total bullshit.

 
2,689
0
Back when I was working with Dave at KiteShip (2006) we did these analyses as well. A big (75,000ft2/7,500m2) helium-stabilized traction kite was by far the most efficient way of providing additional power to slow VLCCs, especially on the mostly downwind run from Venezuela to Galveston Bay, or California to Hawai'i, developing sometimes up to 50% fuel savings. The multiple-mast soft/hard sail option just wasn't a contender.

But in the end, neither were we.

Ship owners hate complexity and added risk. Ship masters hate it even more. The idea of having to look out the windows at something complex, fragile and different was a complete deal-killer. Pass the increased fuel costs to the customer every time, in the way of increased freight charges. A no-brainer.

All this is wonderful in theory, but it's a technology without a paying market. And that's no way to run a business.
How often would a vlcc carry oil from California to Hawaii? When would a vlcc be anywhere near Galveston Bay, and why would you need air brakes to slow it down?

Is there usually a contractual requirement to perform at a minimum speed?

Just curious.

 
Last edited by a moderator:
2,689
0
Dunno, it might really work??
Naw....

As a nav. arch. student, I did a thesis paper on wind assist for commercial ships. Basically the price of fuel needs to be so high for it to work that it is not feasible.

Also, tankers routinely take green water over the deck. Those little sails would have to be pretty dern heavy to stand up to that. And just everyday industrial conditions on a tanker are pretty friggin rough. Maiteneance costs of another system onboard- not reasonable.

A simple computation... under ideal beam apparent wind at 20 knots...

assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2

lift= 0.5 r*v^2*A*C

C: lift coefficient (give a fairly generous C of 2.0)

r: air density taken as 0.0023769 slug/ft^3

v: 20 knots = 33.8 ft/s

A: area = 1600 ft^2

force from one sail = 4300 lb of thrust per sail. x 20 sails = 86000 lb of thrust.

A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust.

multiply the sail thrust by about .7 since the leeward sails will be in the wash of the windward sails => 60,000 lbs of sail thrust under ideal conditions.

60,000 / 1,500,000 = 0.04, or a 4% thrust benefit. Not worth it when you factor the drag under headwind conditions, maintenance costs, weight, etc. And that calc was for pretty much ideal circumstances. Actual thrust benefit under a range of conditions would be way less.
I have a couple comments on your calculations:

"assume those sails are roughly 80 feet high by 20 feet chord. = 1600 ft^2"

They state 5000 sq m, which is almost 2700 sq ft per sail. So the force from one sail (using all of your other assumptions) then becomes over 7200 lb, and for 20 sails is almost 145,000 lb. Applying your 0.7 correction for efficiency results in about 100,000 lb of total thrust from the sails.

"A typical tanker of that size will crank out 80000 hp or more at about 17 knots => 1.5 million lb of thrust."

You dont define this power, but since very few (actually no one) talk about effective power, it is reasonable to assume that this is brake power. Thus we need to apply a propulsive coefficient (efficiency) when calculating the thrust produced, which you seem to have missed. Using a generous 0.667, we then get => 1.0 million lb of thrust (resistance).

However, they claim typical power is half of your value: 30 MW = 40,230 hp. So now the total thrust / resistance is => 500,000 lb.

"60,000 / 1,500,000 = 0.04, or a 4% thrust benefit."

100,000 / 500,000 = 0.20, or 20% benefit.

They then claim further resistance reduction (required thrust) from previous ships through other means such as higher length-to-beam ratio and air lubrication of the hull. So the 500,000 lb resistance number goes down and the percentage obtained from the sails will be even higher (at least for this ideal case).

I'm not saying it's feasible...
ya, I eyeballed the sail size by estimating the mast height from the ht of the deckhouse, maybe I underestimated a bit. But HP I estimated as power at the props, so maybe your cut down factor is a little much on the power.
The air lubrication thing is total bullshit.
So is 17 knots in 90 pct of vlcc reality world
 

P_Wop

Super Anarchist
7,134
4,293
Bay Area, CA
Back when I was working with Dave at KiteShip (2006) we did these analyses as well. A big (75,000ft2/7,500m2) helium-stabilized traction kite was by far the most efficient way of providing additional power to slow VLCCs, especially on the mostly downwind run from Venezuela to Galveston Bay, or California to Hawai'i, developing sometimes up to 50% fuel savings. The multiple-mast soft/hard sail option just wasn't a contender.

But in the end, neither were we.

Ship owners hate complexity and added risk. Ship masters hate it even more. The idea of having to look out the windows at something complex, fragile and different was a complete deal-killer. Pass the increased fuel costs to the customer every time, in the way of increased freight charges. A no-brainer.

All this is wonderful in theory, but it's a technology without a paying market. And that's no way to run a business.
How often would a vlcc carry oil from California to Hawaii?When would a vlcc be anywhere near Galveston Bay, and why would you need air brakes to slow it down?

Is there usually a contractual requirement to perform at a minimum speed?

Just curious.
OK, answers....

1. Never. My error. But Matson and others tug loads of slow barges on that route

2. For Galveston bay, read US Gulf Coast. And air brakes? What part of my post suggested such nonsense?

3. Speed is a hull, machinery, design and operational decision. Slow speed ships should benefit more from sail assist. Fast ships don't. Simply a matter of a wider range of usable apparent wind angle.

Cheers, J

 




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