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.

In article .com,
says...
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.

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)?

2. How much righting moment does a water ballasted boat provide given
the ballast is below the waterline?

And a cheeky Q3? - How much does water weigh - in water?

--
Duncan
[Farr 7500 'Hi-Time' http://hitime.no-ip.info]

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

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]

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]

"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

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

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]

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]

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