Boat Capacity in accordance with Marine and Safety By-Laws

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Raya
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Joined: Sat May 05, 2012 4:25 pm
Investigator Boat Name: Tme Out
Location: Gold Coast

Boat Capacity in accordance with Marine and Safety By-Laws

Post by Raya »

I wonder how our Investigators got by for the last forty years without that sticker.

I know that Investigators can carry at least one band with all instruments but I doubt that the authorities would take that evidence as a quantitative assessment.

There are several different versions of tables I have seen which relate people carrying capacity to boat size. Some tables take into account beam size as well as length but others go only on length (see below). For the Investigator at 5.63m long, all the tables that I can find result in a capacity of 7 adults. That would be quite squeezy on our boats.

I might be able to get a look at the Australian Standard. If I can, I'll extract the formular for carrying capacity and post here for prosperity.
Band(s).jpg
Boat capacity table.jpg
Ray
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Raya
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Investigator Boat Name: Tme Out
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Re: Boat Capacity in accordance with Marine and Safety By-Laws

Post by Raya »

I've had a look at the standard. (AS1799.1-1992 has now been superceded by AS 1799.1 - 2009.) There is no cross reference to an ISO standard.

AS 1799.1 doesn't include maximum persons tables but instead involves a calculation based on the maximum load capacity of the boat. An allowance of 80 kg is made for the body mass of each adult with an additional allowance of 10 kg per person for ancillary equipment and personal gear.

The maximum persons is calculated by taking the maximum load capacity, subtracting the assumed mass of the largest outboard motor (given in a table) and dividing the result by 90kg. There is a slightly different calculation for inboard motors but the Investigator would use the outboard method. The standard doesn't mention sail boats.

To calculate the maximumum load capacity, you first have to calculate the hull volume below the Static Float Plane. This is the level that water must reach before filling the boat. For the Investigator, this would be the level at the top of the combing below the cabin entry. The volume is converted to the mass of water it would displace, subtracting the mass of the boat, excluding the mass of the engine, fuel tank and fuel, allowing 1 kg of boat load capacity for each 5 kg of remaining displacement, and finally subtracting the mass of the engine, fuel tank and fuel to obtain the maximum load capacity.

I'll run the numbers to find the answer but will first have to take some measurements of the hull to determine volume below the Static Float Plane. This could be tricky.

David, I'll send you a PM with more info.
Ray
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Raya
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Investigator Boat Name: Tme Out
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Re: Boat Capacity in accordance with Marine and Safety By-Laws

Post by Raya »

Measured up my hull and did the calculations as per AS 1799.1 - 2009. Guess what? Works out to be 7 people just like the table says.

Here is a copy of the calculations to satisfy the powers that be.
Investigator Max People calculation.jpg
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Ozzie
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Re: Boat Capacity in accordance with Marine and Safety By-Laws

Post by Ozzie »

I had forgotten how much work Ray did in regards to this thread. Ray correct me here but does this mean if you raised the height of the combing at the cabin entry to say the seat height in the cockpit you could technically increase the capacity or am I overstating the significance of this.
Ozzie
Investigator #143 "SPRITZIG II"

The Mariner - “It’s too strange here. It doesn’t move right." ...
Enola - “Helen said that it’s only land sickness."
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Raya
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Re: Boat Capacity in accordance with Marine and Safety By-Laws

Post by Raya »

Ozzie,

Raising the height of the entry into the cabin would indeed raise the carrying capacity according to the formula in the standard as this increases the displacement needed to flood the hull. As a rough estimate, you would need to raise the height by around 100mm to reach the 8 person loading. The absolute limit would be reached when the cabin entry height was level with the gunnels.
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Ozzie
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Re: Boat Capacity in accordance with Marine and Safety By-Laws

Post by Ozzie »

Thanks Ray. Given the Investigator563 has such a good ballast ratio and stability it would make sense to have the cabin threshold at least at a max height you could comfortably step over If it increased the sea safety of the boat.

I have a split stormboard that I don’t use much and no longer keep aboard, just use a one piece that’s either in or out. When I built it, I made the bottom section as high as my wife can step over and comfortably reach the internal step but I think if I was going to do open water work I would glass the threshold permanently at that level particularly given the anaemic cockpit drains.

I remember stuff I may have posted on here years ago on the boats than sail inside the arctic circle. 🥶The stormboards are glassed over and accessing the cabin is via a roof hatch. Either that or replaced by something resembling a submarine hatch.

Probably overkill on Lake Mac. :oops:
Ozzie
Investigator #143 "SPRITZIG II"

The Mariner - “It’s too strange here. It doesn’t move right." ...
Enola - “Helen said that it’s only land sickness."
Waterworld (1995)
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