Nav. bridge visibility on planing craft

[innomare]

Dear all,

On displacement ships, the requirements for navigation bridge visibility are quite clear: a 1m80 person standing at the stearing position should see the water's surface at 2 shiplengths forward of the bow, along with other requirements.
How does this work out for planing craft?
Is the same kind of rule applicable and should you then consider the ship in planing condition (with a trim of e.g. 4 °) or are there less stringent rules?

Thanks,

Bruno

[lewisboats]

I would say that before attaining planning speed you would be looking at 3-4 ship lengths (depending on how high the bows are, ( reverse sheer?)) and about the same 2-2.5 lengths once up on plane. Also depends on how high the cockpit/steering station is.

[dougfrolich]

The ISO has some specific guidelines for vis.

[lewisboats]

After browsing the PDF, looks like I was in the ball park. Doesn't seem to accomodate varying heights of people too well does it?

[dougfrolich]

Just ISO standard people

[lewisboats]

They threw out the cookie cutter before they got to me... Length/width ratio=1:1
steve

[innomare]

Thanks!
Very useful information!
well not the 1:1 body ratio perhaps

[innomare]

In a nutshell what I found:

Distance at which you should see the waters surface from the stearing position:

According to SOLAS: 2 ship lengths from the bow, or 500 m whichever is less
MCA large yacht code: refers to SOLAS
According to IMO High Speed Craft Code (HSC): 1 ship length
According to ISO standards for small craft (up to 24m): 4 ship lengths, with a maximum of 50 m

Are there any class rules for pleasure craft (say Lloyd's Register for example) giving a number on this?

Cheers,

Bruno

[Willallison]

The boys at Wally obviously didn't have a copy of those regs when they designed their (otherwise desirable) 118. A recent MBY test that I read said the helmsman couldn't see the water at all once the boat was on the plane!! Still... what damage can a 120ft boat doing 50+ knots do.....

[innomare]

This is a difficult issue. In my present design work it has a very strong impact on the overall design (as it often has).
Leaving the rules aside, what do you think would be a reasonable distance for an aprox. 40 m yacht, with a top speed of aprox. 30 knots?

Any yacht captains that want to throw in their bit of experience?

[D'ARTOIS]

On a 40 m yacht the bridge is placed high enough to see at least two shiplenghts ahead, secondly there are very few yachts of that length that can reach 30 knots at full sea - thirdly when they do plane they do not raise the bow as high as a (much smaller) cabin cruiser will do.

[yokebutt]

Well, let's consider this, you're barreling away at 50kts. with a 118 foot boat......If you happen to see an obstuction, be it at four boat-lengths or two boat-lengths, aren't the consequences somewhat.....Ahem.....Academic?

Yokebutt.

[innomare]

I don't consider this an academic issue at all. It seems obvious to me that the speed you will make is not only function of the seastate and your engine power, but also of what you can see.
Apart from that there is also the safety of other people to consider.
Yokebutt, at 30 knots with a 40 m yacht, you have about 13 seconds to react if you see something at four boatlengths.
If you can't see the water, you'll probably won't react at all.

D'Artois, I guess www.heesenyachts.com is not a new website to you?

[yokebutt]

Oh, come on, innomare, I was just being a little facetious, thats all, a little humour never hurts.

Yokebutt.

[innomare]

No problem, yokebutt. Joke taken