Has anyone bought a dutch steel for sea use and loved it?

[MapisM]

Out of interest, why should the CoG of a steel boat be any higher than a grp boat?

+1.
That sounds like a sweeping generalization, because there are many factors to consider.
On one hand, it's fair to assume that a steel superstructure is heavier than a plastic one.
Otoh, steel is normally used for D hulls, which are normally ballasted in the keel.
And many of them are also built with a steel hull+alu superstructure.
"Horses for courses" springs to mind...

 

[Deleted User YDKXO]

Otoh, steel is normally used for D hulls, which are normally ballasted in the keel.

That was my thinking. On a D boat, if you need to lower the CoG, surely all you do is add ballast? How much heavier is the steel plate that might be used in the construction of the superstructure on a steel D boat compared to cored grp construction? Anyone got any figures?

 

[MapisM]

Nope, I've never seen such comparison.
Common sense suggests that even if steel plates typically used for superstructures are thinner than those used for the hull, they still can't match the lightness of cored grp, anyway...
Then again, this doesn't necessarily mean a higher COG, if the lower bits are proportionally heavier, as is the case in D boats, for more reasons than one (thicker plates, ballast, structural tanks in double bottom).

 

[Deleted User YDKXO]

Nope, I've never seen such comparison.
Common sense suggests that even if steel plates typically used for superstructures are thinner than those used for the hull, they still can't match the lightness of cored grp, anyway...

Mmm, I'd still like to understand the difference

 

[MapisM]

Well, my "common sense guess" was nothing else than, ermm, a guess...
But I'd be surprised if you could find any proper comparison of a boat superstructure weight between the two materials AOTBE, simply because they are typically used for very different boats, where the choice is mainly driven by other factors.
Though maybe it's possible to find some numbers comparing strength/stiffness of the two materials for a given fixed shape, 'dunno...

 

[oceanfroggie]

Oohhoo I'll be watching this one..... OceanFroggie give I think has D steel boat and has done many passages.

No we are SD GRP (ie Broom @ 7kt, 15kt or 18kt)

Steel popular for inland displacement designs, and occasional short salt water forays, but leisure steel boats definitely need a lot more care if kept on salt water. It's manageable but needs constant touching up at the first sign of rust marks. In these damp isles inside steel hulls are more vulnerable to condensation. GRP in this climate feels dryer and warmer. Despite the advances in epoxy resin paints steel hulls will need to be repainted every 10-12 years or so.

 

[rustybarge]

Well, my "common sense guess" was nothing else than, ermm, a guess...
But I'd be surprised if you could find any proper comparison of a boat superstructure weight between the two materials AOTBE, simply because they are typically used for very different boats, where the choice is mainly driven by other factors.
Though maybe it's possible to find some numbers comparing strength/stiffness of the two materials for a given fixed shape, 'dunno...

Robg71 steel Bonito 45' fast S/D 20 tons.....ST44 GRP fast S/D 11 tons. Max speed on both in the low 20's.......

 

[MapisM]

Robg71 steeel 45' fast S/D 20 tons.....ST44 GRP fast S/D 11 tons. Max speed on both in the low 20's.......

Yep, I know, but that doesn't really answer Deleted User question, does it?

 

[rustybarge]

Yep, I know, but that doesn't really answer Deleted User question, does it?

Displ. Boats are normally round bilge, so they roll much easier.

 

[Deleted User YDKXO]

Well, my "common sense guess" was nothing else than, ermm, a guess...
But I'd be surprised if you could find any proper comparison of a boat superstructure weight between the two materials AOTBE, simply because they are typically used for very different boats, where the choice is mainly driven by other factors.
Though maybe it's possible to find some numbers comparing strength/stiffness of the two materials for a given fixed shape, 'dunno...

The reason I ask is that thin steel plate reinforced with light steel angle is quite stiff and yet quite lightweight; it's a common manufacturing method for the superstructure of construction machines. I find it hard to believe this is considerably heavier than cored grp. Still, I know nothing; I'm sure the boat builders themselves know what they're doing

 

[Searush]

FYI; If you take the mast down on a raggie, it rolls with a nasty "whip" action because the weight is concentrated in a shorter lever without the mast & rigging.

Perhaps the use of ballast in a barge type hull has a similar effect because the effect is that of a short pendulum rather than a long one, or for more evenly distributed weights.

 

[Deleted User YDKXO]

FYI; If you take the mast down on a raggie, it rolls with a nasty "whip" action because the weight is concentrated in a shorter lever without the mast & rigging.

Same argument that Nordhavn use to justify their tall superstructures. They say it increases the roll period and slows down the transition between rolling in one direction to rolling in the other direction. Of course, too tall a superstructure and you are into stability issues

 

[rustybarge]

Same argument that Nordhavn use to justify their tall superstructures. They say it increases the roll period and slows down the transition between rolling in one direction to rolling in the other direction. Of course, too tall a superstructure and you are into stability issues

that's very interesting.
Many Years ago I used to take the mail boat across the Irish sea before stabs were common. It used to roll like a pig...but it was a very slow roll. Comfortable, but sick inducing.

 

[oceanfroggie]

that's very interesting.
Many Years ago I used to take the mail boat across the Irish sea before stabs were common. It used to roll like a pig...but it was a very slow roll. Comfortable, but sick inducing.

I remember it well, the old B&I vomit bucket

 

[PCUK]

No we are SD GRP (ie Broom @ 7kt, 15kt or 18kt)

Steel popular for inland displacement designs, and occasional short salt water forays, but leisure steel boats definitely need a lot more care if kept on salt water. It's manageable but needs constant touching up at the first sign of rust marks. In these damp isles inside steel hulls are more vulnerable to condensation. GRP in this climate feels dryer and warmer. Despite the advances in epoxy resin paints steel hulls will need to be repainted every 10-12 years or so.

Sorry total nonsense. Epoxy coated steel boats are as corrosion resistant as GRP except when damaged.

 

[PCUK]

I met a guy in Croatia this year who had just bought a 40ft Linssen for coastal passaging and he was complaining about roll too. Out of interest, why should the CoG of a steel boat be any higher than a grp boat?

Because as said, the superstructure is heavier. Small sea-going steel boats do not have extra heavily built hulls so the only option is ballast which costs in fuel and speed terms.

 

[rustybarge]

Sorry total nonsense. Epoxy coated steel boats are as corrosion resistant as GRP except when damaged.

Instead of GRP foam sandwich, it's epoxy steel sandwich.

 

[MapisM]

Same argument that Nordhavn use to justify their tall superstructures.
They say it increases the roll period and slows down the transition between rolling in one direction to rolling in the other direction.

Yeah, I heard that before. The key word is "justify", I suppose.
It's pretty obvious that the real reason behind their latest boat design is to sell more living space for any given LOA.
And in doing that, they make boats whose layout force anyone onboard to be climbing stairs all the time.
True as it is that the rolling motion is smoother with a higher COG (AOTBE), the justification doesn't make a lot of sense for stabilised boats (as 99% of Nordhavn are), where the rolling is ironed out anyway.
Rather the opposite, in fact, since stabs are more efficient with a lower COG (again, AOTBE).

 

[oceanfroggie]

Sorry total nonsense. Epoxy coated steel boats are as corrosion resistant as GRP except when damaged.

That's the point, some hulls get the occasional rub off a jetty or quay, or little scratch and the rust stains follow, but much faster in salt water. Its generally more of an issue for the superstructure as its more exposed to wear and tear. Look inside a steel hull where even stainless sterl bolts and fixtures attach to the hull, after a time rust stains and rust makes an appearance. It's negligible inland but on salt water based vessels it's more prevalent. Three pals of mine have lovely steel D cruisers. They are fastidious about treating and touching up any sign of staining or rust as soon as it appears. It's not a huge problem, but they do need more care than grp.

 

[rustybarge]

That's the point, some hulls get the occasional rub off a jetty or quay, or little scratch and the rust stains follow, but much faster in salt water. Its generally more of an issue for the superstructure as its more exposed to wear and tear. Look inside a steel hull where even stainless sterl bolts and fixtures attach to the hull, after a time rust stains and rust makes an appearance. It's negligible inland but on salt water based vessels it's more prevalent. Three pals of mine have lovely steel D cruisers. They are fastidious about treating and touching up any sign of staining or rust as soon as it appears. It's not a huge problem, but they do need more care than grp.

...and of course GRP cracks and crazes; rips and splinters if you hit something. steel may rust, but just crumples on contact with an immovable object.

You pays your money and.......