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Any thoughts onhow to make this boat better
I have been getting interested in building this boat:
http://www.duckworksbbs.com/plans/jim/cormorant/ Of course, I have to finish the Tolman Skiff first, but a trailerable water ballast sailboat that I can build to my needs is attractive to me but I have some concerns 1. Do water ballasted boats tend to be exceptionally "tippy" before they are filled? 2. Could this be alleviated by including a few hundred lbs of lead sheeting along the bottom? Any other useful thoughts? Yes, I know you do not save money by building boats but its become an obsession. |
Any thoughts onhow to make this boat better
says...
I have been getting interested in building this boat: http://www.duckworksbbs.com/plans/jim/cormorant/ hmm, not the prettiest boat I've seen. Of course, I have to finish the Tolman Skiff first, but a trailerable water ballast sailboat that I can build to my needs is attractive to me but I have some concerns Trailerable can be a great way to go. The trade-offs are that you can cruise much wider territory (VMG to windward 65mph) but have to deal with trailer maintenance & highway traffic. Frankly I would not want to trailer a 32' boat, IMHO the 'bigger is better' attitudes leads to some expensive hassles when you try to take it on the road. My wife and I cruised a 19-footer (which was water ballasted) for some years. It was cozy but very practical & we spent much less time on rigging & other petty hassles than friends with bigger trailerables. 1. Do water ballasted boats tend to be exceptionally "tippy" before they are filled? No more so than the hull form dictates. 2. Could this be alleviated by including a few hundred lbs of lead sheeting along the bottom? Possibly but not definitely. Is the added weight no trailering penalty for your tow vehicle? All the lead is going to do for initial stability is to sink the hull lower in the water, it will increase stability if you put the turn of a hard bilge right to the waterline. Otherwise, it's not likely to make a great improvement in stability. Any other useful thoughts? Yes, I know you do not save money by building boats but its become an obsession. In that case, build the best one for your purpose. How about this one? http://www.dixdesign.com/26didi.htm I've sailed one of these and they're fast & fun. Dave Doe wrote: I have a couple a questions... 1. How much water ballast (approx litres) does it take to equal say 200lbs of lead hanging 6' down (on say a swing keel)? Umm, about 200# maybe? 2. How much righting moment does a water ballasted boat provide given the ballast is below the waterline? The same RM as an equal weight of any other material... say, feathers, for example... providing the same center of gravity. And a cheeky Q3? - How much does water weigh - in water? Not cheeky at all, just makes you sound ignorant of physics. How much does water weigh when it's inside the boat? Fresh Breezes- Doug king |
Any thoughts onhow to make this boat better
In article ,
says... says... I have been getting interested in building this boat: http://www.duckworksbbs.com/plans/jim/cormorant/ hmm, not the prettiest boat I've seen. Of course, I have to finish the Tolman Skiff first, but a trailerable water ballast sailboat that I can build to my needs is attractive to me but I have some concerns Trailerable can be a great way to go. The trade-offs are that you can cruise much wider territory (VMG to windward 65mph) but have to deal with trailer maintenance & highway traffic. Frankly I would not want to trailer a 32' boat, IMHO the 'bigger is better' attitudes leads to some expensive hassles when you try to take it on the road. My wife and I cruised a 19-footer (which was water ballasted) for some years. It was cozy but very practical & we spent much less time on rigging & other petty hassles than friends with bigger trailerables. 1. Do water ballasted boats tend to be exceptionally "tippy" before they are filled? No more so than the hull form dictates. 2. Could this be alleviated by including a few hundred lbs of lead sheeting along the bottom? Possibly but not definitely. Is the added weight no trailering penalty for your tow vehicle? All the lead is going to do for initial stability is to sink the hull lower in the water, it will increase stability if you put the turn of a hard bilge right to the waterline. Otherwise, it's not likely to make a great improvement in stability. Any other useful thoughts? Yes, I know you do not save money by building boats but its become an obsession. In that case, build the best one for your purpose. How about this one? http://www.dixdesign.com/26didi.htm I've sailed one of these and they're fast & fun. Dave Doe wrote: I have a couple a questions... 1. How much water ballast (approx litres) does it take to equal say 200lbs of lead hanging 6' down (on say a swing keel)? Umm, about 200# maybe? Can't be, the 'moment' is entirely different for starters, as: the water ballast is on the centerline, but the lead is 6' down. What the hell do you think canting keels are all about! 2. How much righting moment does a water ballasted boat provide given the ballast is below the waterline? The same RM as an equal weight of any other material... say, feathers, for example... providing the same center of gravity. And a cheeky Q3? - How much does water weigh - in water? Not cheeky at all, just makes you sound ignorant of physics. How much does water weigh when it's inside the boat? If it's below the waterline? - nothing! Sounds like *you're* ignorant of physics - think! - why did the last round the world yacht race boats pump water from side to side? A: because they could pump it to an area well above the waterline *and* to one side of the boat, therefore providing righting moment. I went out on a Mac 26M last year (a guy in NZ has become a dealer) - and was very impressed by its value for money. But there endeth my good impressions. The water ballast, to me, provided a stabalisation factor only. The rigging (infact the whole boat) seems a bit light. To me it may not be well suited to New Zealand conditions - though the Mac website tells us that the boats haven't busted - and they *have* produced quite a few of 'em. The 6' of head room surely must be measured before the carpet's fitted - I measured it at about 5'10 or 11. That said, in my boat there is only standing room under the poptop. The boat *does* make great use of the space available, but at the expense of storage and it's spartan interior. Back to water ballasting on the centerline though... I think the most inherently dangerous factor is the user - ie the "how often can I get away with an empty ballast in ever decreasing safe water conditions", factor. I think the instructions should say only in dead calm water condtions. Otherwise if the boat goes over, she ain't comin' back! Indeed the water ballasting *only* has positive righting moment if the boat is pushed over to where the centerline is above the waterline (a fair way!). Otherwise, it's mass is a stability plus factor only. PS: if yer don't believe me, fill a milk carton with water and play with it in the bath :) -- Duncan [Farr 7500 'Hi-Time' http://hitime.no-ip.info] |
Any thoughts onhow to make this boat better
Dave Doe wrote: In article , says... says... I have been getting interested in building this boat: http://www.duckworksbbs.com/plans/jim/cormorant/ hmm, not the prettiest boat I've seen. Of course, I have to finish the Tolman Skiff first, but a trailerable water ballast sailboat that I can build to my needs is attractive to me but I have some concerns Trailerable can be a great way to go. The trade-offs are that you can cruise much wider territory (VMG to windward 65mph) but have to deal with trailer maintenance & highway traffic. Frankly I would not want to trailer a 32' boat, IMHO the 'bigger is better' attitudes leads to some expensive hassles when you try to take it on the road. My wife and I cruised a 19-footer (which was water ballasted) for some years. It was cozy but very practical & we spent much less time on rigging & other petty hassles than friends with bigger trailerables. 1. Do water ballasted boats tend to be exceptionally "tippy" before they are filled? No more so than the hull form dictates. 2. Could this be alleviated by including a few hundred lbs of lead sheeting along the bottom? Possibly but not definitely. Is the added weight no trailering penalty for your tow vehicle? All the lead is going to do for initial stability is to sink the hull lower in the water, it will increase stability if you put the turn of a hard bilge right to the waterline. Otherwise, it's not likely to make a great improvement in stability. Any other useful thoughts? Yes, I know you do not save money by building boats but its become an obsession. In that case, build the best one for your purpose. How about this one? http://www.dixdesign.com/26didi.htm I've sailed one of these and they're fast & fun. Dave Doe wrote: I have a couple a questions... 1. How much water ballast (approx litres) does it take to equal say 200lbs of lead hanging 6' down (on say a swing keel)? Umm, about 200# maybe? Can't be, the 'moment' is entirely different for starters, as: the water ballast is on the centerline, but the lead is 6' down. What the hell do you think canting keels are all about! 2. How much righting moment does a water ballasted boat provide given the ballast is below the waterline? The same RM as an equal weight of any other material... say, feathers, for example... providing the same center of gravity. And a cheeky Q3? - How much does water weigh - in water? Not cheeky at all, just makes you sound ignorant of physics. How much does water weigh when it's inside the boat? If it's below the waterline? - nothing! Sounds like *you're* ignorant of physics - think! - why did the last round the world yacht race boats pump water from side to side? A: because they could pump it to an area well above the waterline *and* to one side of the boat, therefore providing righting moment. Water weighs the same above or below the waterline, and the same in or out of water assuming the same gravitational potential. I went out on a Mac 26M last year (a guy in NZ has become a dealer) - and was very impressed by its value for money. But there endeth my good impressions. The water ballast, to me, provided a stabalisation factor only. The rigging (infact the whole boat) seems a bit light. To me it may not be well suited to New Zealand conditions - though the Mac website tells us that the boats haven't busted - and they *have* produced quite a few of 'em. The 6' of head room surely must be measured before the carpet's fitted - I measured it at about 5'10 or 11. That said, in my boat there is only standing room under the poptop. The boat *does* make great use of the space available, but at the expense of storage and it's spartan interior. Back to water ballasting on the centerline though... I think the most inherently dangerous factor is the user - ie the "how often can I get away with an empty ballast in ever decreasing safe water conditions", factor. I think the instructions should say only in dead calm water condtions. Otherwise if the boat goes over, she ain't comin' back! Indeed the water ballasting *only* has positive righting moment if the boat is pushed over to where the centerline is above the waterline (a fair way!). Otherwise, it's mass is a stability plus factor only. PS: if yer don't believe me, fill a milk carton with water and play with it in the bath :) -- Duncan [Farr 7500 'Hi-Time' http://hitime.no-ip.info] |
Any thoughts onhow to make this boat better
"Dave Doe" wrote in . Indeed the water ballasting *only* has positive righting moment if the boat is pushed over to where the centerline is above the waterline (a fair way!). Bzzzzzzt! You are wrong Dave. PS: if yer don't believe me, fill a milk carton with water and play with it in the bath A scientific study if ever there was one. SBV |
Any thoughts onhow to make this boat better
Scotty wrote:
"Dave Doe" wrote in . Indeed the water ballasting *only* has positive righting moment if the boat is pushed over to where the centerline is above the waterline (a fair way!). Bzzzzzzt! You are wrong Dave. Agreed - the boat will start to acquire righting moment as soon as any of the water ballast is higher than the surface - and there won't be very much righting moment if only a little of the ballast is above the surface, improving as the boat heels. IOW, the amount of righting moment varies, depending on the amount of heel and just how the ballast is arranged within the hull. -- Capt Scumbalino |
Any thoughts onhow to make this boat better
In article ,
says... Scotty wrote: "Dave Doe" wrote in . Indeed the water ballasting *only* has positive righting moment if the boat is pushed over to where the centerline is above the waterline (a fair way!). Bzzzzzzt! You are wrong Dave. Agreed - the boat will start to acquire righting moment as soon as any of the water ballast is higher than the surface - and there won't be very much righting moment if only a little of the ballast is above the surface, improving as the boat heels. IOW, the amount of righting moment varies, depending on the amount of heel and just how the ballast is arranged within the hull. Yer just getting pedantic - yer know what I mean/meant. (Yes, if *any* water in the ballast is above the waterline, it will provide righting moment - pedantic chit aside - if this *ISN'T* the case, is there any righting moment?) -- Duncan [Farr 7500 'Hi-Time' http://hitime.no-ip.info] |
Any thoughts onhow to make this boat better
In article ,
says... "Dave Doe" wrote in . Indeed the water ballasting *only* has positive righting moment if the boat is pushed over to where the centerline is above the waterline (a fair way!). Bzzzzzzt! You are wrong Dave. Nice evidence. PS: if yer don't believe me, fill a milk carton with water and play with it in the bath A scientific study if ever there was one. It sure *is*. -- Duncan [Farr 7500 'Hi-Time' http://hitime.no-ip.info] |
Any thoughts onhow to make this boat better
Dave Doe wrote:
Yer just getting pedantic - yer know what I mean/meant. Nope. How do I know if you understand the physics involved, other than by assessing what you write? (Yes, if *any* water in the ballast is above the waterline, it will provide righting moment - pedantic chit aside - if this *ISN'T* the case, is there any righting moment?) I guess there could be as a result of increasing bouancy - if the water ballast at rest is below the surface, then a certain amount of heel might be such that the ballast stays below the surface, but, depending on hull shape, heeling might tend to increase the amount of air below the surface, with an effect not unlike the righting moment induced by a counterbalancing weight. -- Capt Scumbalino |
Any thoughts onhow to make this boat better
"Dave Doe" wrote in message . Indeed the water ballasting *only* has positive righting moment if the boat is pushed over to where the centerline is above the waterline (a fair way!). Bzzzzzzt! You are wrong Dave. Nice evidence. This is ASA, no evidence necassary. PS: if yer don't believe me, fill a milk carton with water and play with it in the bath A scientific study if ever there was one. It sure *is*. Take a 5 gallon jerry jug, put 5 gallons of water in it. Will it float? Take that same 5 g. jug and put the same weight ( approx. 40 lbs.) in of lead. Will it float? Which floats higher? Conclude which is heavier? Make sure you wash behind your ears. Scotty |
Any thoughts onhow to make this boat better
In article .com,
says... Dave Doe wrote: In article , says... says... I have been getting interested in building this boat: http://www.duckworksbbs.com/plans/jim/cormorant/ hmm, not the prettiest boat I've seen. Of course, I have to finish the Tolman Skiff first, but a trailerable water ballast sailboat that I can build to my needs is attractive to me but I have some concerns Trailerable can be a great way to go. The trade-offs are that you can cruise much wider territory (VMG to windward 65mph) but have to deal with trailer maintenance & highway traffic. Frankly I would not want to trailer a 32' boat, IMHO the 'bigger is better' attitudes leads to some expensive hassles when you try to take it on the road. My wife and I cruised a 19-footer (which was water ballasted) for some years. It was cozy but very practical & we spent much less time on rigging & other petty hassles than friends with bigger trailerables. 1. Do water ballasted boats tend to be exceptionally "tippy" before they are filled? No more so than the hull form dictates. 2. Could this be alleviated by including a few hundred lbs of lead sheeting along the bottom? Possibly but not definitely. Is the added weight no trailering penalty for your tow vehicle? All the lead is going to do for initial stability is to sink the hull lower in the water, it will increase stability if you put the turn of a hard bilge right to the waterline. Otherwise, it's not likely to make a great improvement in stability. Any other useful thoughts? Yes, I know you do not save money by building boats but its become an obsession. In that case, build the best one for your purpose. How about this one? http://www.dixdesign.com/26didi.htm I've sailed one of these and they're fast & fun. Dave Doe wrote: I have a couple a questions... 1. How much water ballast (approx litres) does it take to equal say 200lbs of lead hanging 6' down (on say a swing keel)? Umm, about 200# maybe? Can't be, the 'moment' is entirely different for starters, as: the water ballast is on the centerline, but the lead is 6' down. What the hell do you think canting keels are all about! 2. How much righting moment does a water ballasted boat provide given the ballast is below the waterline? The same RM as an equal weight of any other material... say, feathers, for example... providing the same center of gravity. And a cheeky Q3? - How much does water weigh - in water? Not cheeky at all, just makes you sound ignorant of physics. How much does water weigh when it's inside the boat? If it's below the waterline? - nothing! Sounds like *you're* ignorant of physics - think! - why did the last round the world yacht race boats pump water from side to side? A: because they could pump it to an area well above the waterline *and* to one side of the boat, therefore providing righting moment. Water weighs the same above or below the waterline, and the same in or out of water assuming the same gravitational potential. No it doesn't! The *mass* is the same. Take a plastic bag of water and push if off a bench. Take the same and do the same off a wee bench in a tub of water. Sheesh! -- Duncan [Farr 7500 'Hi-Time' http://hitime.no-ip.info] |
Any thoughts onhow to make this boat better
"Dave Doe" wrote in message . Water weighs the same above or below the waterline, and the same in or out of water assuming the same gravitational potential. No it doesn't! The *mass* is the same. Take a plastic bag of water and push if off a bench. Take the same and do the same off a wee bench in a tub of water. Dave, the water in a ballast tank is KNOT IN the water. Sheesh!!!! |
Any thoughts onhow to make this boat better
A chain saw.
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Any thoughts onhow to make this boat better
Thanks Bart:
Knowing a thang er two bout that fiziks an njineerin stuff (MS Physics, MSEE), I think that water ballast does nothing until it is raised above the waterline. I'll forego discussion about the diff tween mass and weight. |
Any thoughts onhow to make this boat better
wrote in message oups.com... Thanks Bart: Knowing a thang er two bout that fiziks an njineerin stuff (MS Physics, MSEE), I think that water ballast does nothing until it is raised above the waterline. Well, you're wrong! Scotty |
Any thoughts onhow to make this boat better
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Any thoughts onhow to make this boat better
Scumbalino. agreed
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Any thoughts onhow to make this boat better
If you want to build a boat, have you considered
the Dudley Dix kits built in South Africa? You could also buy just the plans. Their Mini design could be built with water ballast albeit I don't think the kit includes that feature. http://www.dixdesign.com/didimini.htm I've thought about building one. I like the mini's but the wooden designs are not very competitive, albeit I'm sure they are a blast to sail. wrote Thanks Bart: Knowing a thang er two bout that fiziks an njineerin stuff (MS Physics, MSEE), I think that water ballast does nothing until it is raised above the waterline. I'll forego discussion about the diff tween mass and weight. |
Any thoughts onhow to make this boat better
Capt. Scumbalino wrote: wrote: Knowing a thang er two bout that fiziks an njineerin stuff (MS Physics, MSEE), I think that water ballast does nothing until it is raised above the waterline. If the centre of rotation as the boat heels is in the centre of gravity of the mass of the water ballast, then that might be the case. If the centre of the boat's heeling rotation is above the COG of the ballast, then it has to pull that enclosed mass around - ergo, the water ballast can have an effect when it's below the waterline. I think this is the same thing as what I was saying about bouyancy, but from the perspective of te ballast rather than the air above it. I think this is the answer. - The downward forces on the water ballast tank tend to pull the boat down to the lowermost floating position, at point which the boat is in an upright position, absent other forces. For example, ocean liners utilize water ballast below the waterline. From personal experience, the Mac 26M is initially somewhat tender but becomes increasingly stiffer as it heels. Jim |
Any thoughts onhow to make this boat better
Please tell us the last time you actually heeled your boat!! We want to learn from your vast experience!
-- "j" ganz @@ www.sailnow.com "Jim Cate" wrote in message ... Capt. Scumbalino wrote: wrote: Knowing a thang er two bout that fiziks an njineerin stuff (MS Physics, MSEE), I think that water ballast does nothing until it is raised above the waterline. If the centre of rotation as the boat heels is in the centre of gravity of the mass of the water ballast, then that might be the case. If the centre of the boat's heeling rotation is above the COG of the ballast, then it has to pull that enclosed mass around - ergo, the water ballast can have an effect when it's below the waterline. I think this is the same thing as what I was saying about bouyancy, but from the perspective of te ballast rather than the air above it. I think this is the answer. - The downward forces on the water ballast tank tend to pull the boat down to the lowermost floating position, at point which the boat is in an upright position, absent other forces. For example, ocean liners utilize water ballast below the waterline. From personal experience, the Mac 26M is initially somewhat tender but becomes increasingly stiffer as it heels. Jim |
Any thoughts onhow to make this boat better
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Any thoughts onhow to make this boat better
I've looked at the Dix boats and a few others. Unfortunately, I am
6'1" so headroom matters. I also think that use of the boat will decrease exponentially with rigging difficulty so that a boat that has very low difficulty will get used much more. Thus, I am not in favor of the marconi rig on a trailer boat and like the Gaff rig of the cormorant with no shrouds. I cannot ascertain the headroom of the Cormorant |
Any thoughts onhow to make this boat better
OK, Duncan. here's a little experiment you can do in your
bathtub. 1. Put an empty Coke bottle in the water. Observe how it floats. 2. Fill the Coke bottle 1/4 with water. Observe how it floats. 3. Fill the bottle 1/2 way. Observe how it floats 4. Fill it 3/4 full. Observe how it floats 5. Is the water in the coke bottle below the tub water surface? 6. Wash your butt last. Scotty "Dave Doe" wrote in message . nz... In article , says... "Dave Doe" wrote in message . Water weighs the same above or below the waterline, and the same in or out of water assuming the same gravitational potential. No it doesn't! The *mass* is the same. Take a plastic bag of water and push if off a bench. Take the same and do the same off a wee bench in a tub of water. Dave, the water in a ballast tank is KNOT IN the water. Sheesh!!!! Neither is the water in the plastic bag! Sheesh! -- Duncan |
Any thoughts onhow to make this boat better
In article ,
says... OK, Duncan. here's a little experiment you can do in your bathtub. 1. Put an empty Coke bottle in the water. Observe how it floats. 2. Fill the Coke bottle 1/4 with water. Observe how it floats. 3. Fill the bottle 1/2 way. Observe how it floats 4. Fill it 3/4 full. Observe how it floats 5. Is the water in the coke bottle below the tub water surface? 6. Wash your butt last. Scotty a) What is the *point* of your experiement? - other than to only prove my argument correct. b) try this (your experiment pretty much, say 4) ... So 3/4 full. Hold the bottle at the top and note the weight. Slowly lower it into the water. Note the weight changing! ??? How can it be getting lighter all by itself? Note also the final level in the water. There is almost no difference in the level of the water in the bottle and the level to which it has sunk. (The difference being a result of the boyancy of the plastic). ie, Ans to your Q5. the level of the water in the bottle is very slightly higher than the water it is in. PS: experiment not conducted, just using simple physics. Feel free to do it and get back to me if I'm wrong. -- Duncan [Farr 7500 'Hi-Time' http://hitime.no-ip.info] |
Any thoughts onhow to make this boat better
Whoa Davey
Here's a better idea.... jump in the water and see how much water you displace. If you displace a lot ...as I suspect... you should still float well enough to undertake the test due to the residue of hot air. Now drink a quarter bottle of Lamb's Navy Overproof Rum and see where you float... continue drinking and take readings at every quarter mark of the bottle. Get Back to Us on Water Ballast.... we'll inform the multi national sailing franchises of your position that they're delusional and water ballast is ineffective. I'm certain someone would be willing to write a "definitive book" regarding your findings. CM "Dave Doe" wrote in message . nz... In article , says... OK, Duncan. here's a little experiment you can do in your bathtub. 1. Put an empty Coke bottle in the water. Observe how it floats. 2. Fill the Coke bottle 1/4 with water. Observe how it floats. 3. Fill the bottle 1/2 way. Observe how it floats 4. Fill it 3/4 full. Observe how it floats 5. Is the water in the coke bottle below the tub water surface? 6. Wash your butt last. Scotty a) What is the *point* of your experiement? - other than to only prove my argument correct. b) try this (your experiment pretty much, say 4) ... So 3/4 full. Hold the bottle at the top and note the weight. Slowly lower it into the water. Note the weight changing! ??? How can it be getting lighter all by itself? Note also the final level in the water. There is almost no difference in the level of the water in the bottle and the level to which it has sunk. (The difference being a result of the boyancy of the plastic). ie, Ans to your Q5. the level of the water in the bottle is very slightly higher than the water it is in. PS: experiment not conducted, just using simple physics. Feel free to do it and get back to me if I'm wrong. -- Duncan [Farr 7500 'Hi-Time' http://hitime.no-ip.info] |
Any thoughts onhow to make this boat better
|
Any thoughts onhow to make this boat better
"Dave Doe" wrote in message LOL - I *love* the idea - mind if I make that a nice single malt scotch though? Single Malt is a worthy choice PS: the book was written many years ago now, some dude called Archimedes IIRC - shame he's not still alive for Scotty to prove him wrong. Yeah... I believe something about the buoyant force on the solid object is equal to the weight of the fluid displaced . So... are you saying that 50 gallons of water in your bilge won't lower your waterline??? Good Grief that means I can store unlimited supplies of rum onboard. CM |
Any thoughts onhow to make this boat better
"Dave Doe" wrote in message . nz... In article , says... OK, Duncan. here's a little experiment you can do in your bathtub. 1. Put an empty Coke bottle in the water. Observe how it floats. 2. Fill the Coke bottle 1/4 with water. Observe how it floats. 3. Fill the bottle 1/2 way. Observe how it floats 4. Fill it 3/4 full. Observe how it floats 5. Is the water in the coke bottle below the tub water surface? 6. Wash your butt last. Scotty a) What is the *point* of your experiement? - other than to only prove my argument correct. To prove to you that water BELOW the water line can still act as ballast. Also , to wash some of the stink off of you. Scotty |
Any thoughts onhow to make this boat better
Dave Doe wrote:
a) What is the *point* of your experiement? - other than to only prove my argument correct. Dave, since your argument is not correct, it would be pretty hard to prove. Are you saying that the water ballast inside a boat hull does not affect it's stability? That the water ballast "weighs nothing" until it is above the waterline? If that were true, the boat's waterline would be the same when the ballast tank was empty as when it is full. Does the boat's displacement increase when the ballast tank is filled? If so, then the the water ballast "weighs" something, regardless of where it is relative to the waterline. If the unit conter of gravity is below what the boat's Center of Gravity would be without the ballast, then it increases the boat's stability, regardless of whether the tank is above or below the waterline. b) try this (your experiment pretty much, say 4) ... So 3/4 full. Hold the bottle at the top and note the weight. Slowly lower it into the water. Note the weight changing! ??? How can it be getting lighter all by itself? Try this experiment. Float an empty bottle. Mark where the waterline is. Now fill it however full you want, 1/4 or 3/4 or whatever. Does the bottle sink any deeper into the water? No? Then it "weighs" more, the water inside the bottle must be weighing it down. PS: experiment not conducted, just using simple physics. Feel free to do it and get back to me if I'm wrong. Yep, it's just simple physics. But a number of people have tried to proclaim that water ballast can't possibly work because "water doesn't weigh anything in water." But it obviously *does* work, and the physics (when considered correctly) show why. Fresh Breezes- Doug King |
Any thoughts onhow to make this boat better
I guess all those big ships with water ballast tanks are just
pretending. Scotty "DSK" wrote in message . .. Dave Doe wrote: a) What is the *point* of your experiement? - other than to only prove my argument correct. Dave, since your argument is not correct, it would be pretty hard to prove. Are you saying that the water ballast inside a boat hull does not affect it's stability? That the water ballast "weighs nothing" until it is above the waterline? If that were true, the boat's waterline would be the same when the ballast tank was empty as when it is full. Does the boat's displacement increase when the ballast tank is filled? If so, then the the water ballast "weighs" something, regardless of where it is relative to the waterline. If the unit conter of gravity is below what the boat's Center of Gravity would be without the ballast, then it increases the boat's stability, regardless of whether the tank is above or below the waterline. b) try this (your experiment pretty much, say 4) ... So 3/4 full. Hold the bottle at the top and note the weight. Slowly lower it into the water. Note the weight changing! ??? How can it be getting lighter all by itself? Try this experiment. Float an empty bottle. Mark where the waterline is. Now fill it however full you want, 1/4 or 3/4 or whatever. Does the bottle sink any deeper into the water? No? Then it "weighs" more, the water inside the bottle must be weighing it down. PS: experiment not conducted, just using simple physics. Feel free to do it and get back to me if I'm wrong. Yep, it's just simple physics. But a number of people have tried to proclaim that water ballast can't possibly work because "water doesn't weigh anything in water." But it obviously *does* work, and the physics (when considered correctly) show why. Fresh Breezes- Doug King |
Any thoughts onhow to make this boat better
Scotty wrote:
I guess all those big ships with water ballast tanks are just pretending. Of course they are. It's just a scam to irritate the enviro-whackoes. The Navy is in on the joke, too... http://p2library.nfesc.navy.mil/P2_O...book/11_9.html Notice that ship stability takes a back seat to needling those tree-hugging pinheads: (quote from the above web site) "Ships with water compensating fuel systems (WCFS) are not allowed to discharge compensating ballast water overboard in some navy ports. Navy ship destroyers (e.g., Spruance and Kidd class) and cruisers (Ticonderoga class) are designed with WCFS to enhance ship stability." DSK |
Any thoughts onhow to make this boat better
"Scotty" wrote in message ... I guess all those big ships with water ballast tanks are just pretending. Scotty That, and they're stealing fresh water from the Great Lakes to take back to Europe. Max |
Any thoughts onhow to make this boat better
"Maxprop" wrote in message ink.net... "Scotty" wrote in message ... I guess all those big ships with water ballast tanks are just pretending. Scotty That, and they're stealing fresh water from the Great Lakes to take back to Europe. Yes buy, don't they give you guys Euro mussels in exchange? SBV |
Any thoughts onhow to make this boat better
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Any thoughts onhow to make this boat better
In article ,
says... "Dave Doe" wrote in message . nz... In article , says... OK, Duncan. here's a little experiment you can do in your bathtub. 1. Put an empty Coke bottle in the water. Observe how it floats. 2. Fill the Coke bottle 1/4 with water. Observe how it floats. 3. Fill the bottle 1/2 way. Observe how it floats 4. Fill it 3/4 full. Observe how it floats 5. Is the water in the coke bottle below the tub water surface? 6. Wash your butt last. Scotty a) What is the *point* of your experiement? - other than to only prove my argument correct. To prove to you that water BELOW the water line can still act as ballast. Indeed it can and I have not questioned that, only it's effectiveness as not just ballast, which I have stated provides a positive stability factor - but I question its effectiveness when used as a righting moment. And further posed the question: How much water ballast (approx litres) does it take to equal say 200lbs of lead hanging 6' down (on say a swing keel)? To make it easier, how about we metricate it all for ease of calculation: Assume Standard Temp & Pressure (STP) How much fresh water (density: 1000kg/m3) does it take to equal 500kg of lead (density: 7140kg/m3) hanging 2m down with the boat at 45deg? Water ballast tank at 1m wide and the boat is in fresh water (also at STP). Feel free to use other figures, I've adjusted from my original, using hopefully more "average" figures and rounded to make calcs easier. So how much water? And... looking at say a Mac, they say they have 1150lbs of water ballast, that's about 520kg. You change the figures if you think mine are unrealistic - I'd just like to see the comparision. PS: only got to sail against a Mac 26M once out in Lytellton; my boat's just under 25' - the Mac is 26'. We thrashed it. (They might be quite competative in light air; 5knts or below). My boat's 23? years old, the Mac is less than 1. It's longer. -- Duncan |
Any thoughts onhow to make this boat better
"Dave Doe" wrote in message . nz... In article , says... "Dave Doe" wrote in message . nz... In article , says... OK, Duncan. here's a little experiment you can do in your bathtub. 1. Put an empty Coke bottle in the water. Observe how it floats. 2. Fill the Coke bottle 1/4 with water. Observe how it floats. 3. Fill the bottle 1/2 way. Observe how it floats 4. Fill it 3/4 full. Observe how it floats 5. Is the water in the coke bottle below the tub water surface? 6. Wash your butt last. Scotty a) What is the *point* of your experiement? - other than to only prove my argument correct. To prove to you that water BELOW the water line can still act as ballast. Indeed it can and I have not questioned that, only it's effectiveness as not just ballast, which I have stated provides a positive stability factor - but I question its effectiveness when used as a righting moment. And further posed the question: How much water ballast (approx litres) does it take to equal say 200lbs of lead hanging 6' down (on say a swing keel)? To make it easier, how about we metricate it all for ease of calculation: Assume Standard Temp & Pressure (STP) How much fresh water (density: 1000kg/m3) does it take to equal 500kg of lead (density: 7140kg/m3) hanging 2m down with the boat at 45deg? Water ballast tank at 1m wide and the boat is in fresh water (also at STP). Feel free to use other figures, I've adjusted from my original, using hopefully more "average" figures and rounded to make calcs easier. So how much water? And... looking at say a Mac, they say they have 1150lbs of water ballast, that's about 520kg. You change the figures if you think mine are unrealistic - I'd just like to see the comparision. PS: only got to sail against a Mac 26M once out in Lytellton; my boat's just under 25' - the Mac is 26'. We thrashed it. (They might be quite competative in light air; 5knts or below). My boat's 23? years old, the Mac is less than 1. It's longer. -- Duncan My understanding is that the Macs have an optimal window of between 7-10 kts.wind, they will hardly move in light air. Tiny rig and sailplan. Have seen a rating for the old 26X at 226, IIRC, but I'm willing to bet that it's very tough to sail anywhere near it's rating. Anecdotal, but I was sailing back to the marina one day, playing with the a-sail, and I passed an x that didn't appear to be moving, my knotmeter was reading 3-4 kts, maybe around 5 kts.of wind. John Cairns |
Any thoughts onhow to make this boat better
Are you saying that the water ballast inside a boat hull
does not affect it's stability? That the water ballast "weighs nothing" until it is above the waterline? Dave Doe wrote: Nope, never did. I'm saying it's stability is indeed improved (more mass to move) That would be an issue of inertia... dynamic stability, if you like the term. ... but question its righting ability vs lead keel - and posed a question about that. Well, I don't think that anybody has claimed that water ballast provides equal righting moment to external lead ballast. But it can provide significant righting moment, especially if the boat is designed from the start to utilize water ballast effectively. The problem is that water in the ballast has the same density of the water it is in Well there you go again. The water ballast is not "in water" it is in the boat. Will no amount of repetition get this point across? You used the example of an empty jug vs one 1/2 full of water... is the water in the jug "in water" or is it in the jug? Let me propose this example- a cooler full of ice & beer is lighter than water (hence lighter than water ballast) yet can be pretty heavy when you're carrying it down the dock. If you put it in the lowest possible location in the boat, right down against the hull, and tie it in securely (to the handles, so you can still open the lid of course), will this improve the boat's stability? DSK |
Any thoughts onhow to make this boat better
"DSK" wrote in message . .. Well there you go again. The water ballast is not "in water" it is in the boat. Will no amount of repetition get this point across? You used the example of an empty jug vs one 1/2 full of water... is the water in the jug "in water" or is it in the jug? Dave just doesn't get it. And he refuses to do any experiments because he is afraid of water. Scotty |
Any thoughts onhow to make this boat better
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