LB22 - how many people and how much weight can she carry?

[Rob R]

Hi All,

I am approaching the final stages of building my nina and am trying to organise registration.

Firstly, thanks to all on the forum and particularly the LB22 builders whose posts have answered my questions along the way.

In Australia we need to attach an Australian Builder's Plate to the boat. This identifies the maximum horsepower, maximum weight of motor, maximum number of people and maximum load weight that the boat can manage and still float if swamped.

These numbers should be assessed via the Australian standard (AS 1799) or the International one (ISO 12217-1:2015
Small craft -- Stability and buoyancy assessment and categorization -- Part 1: Non-sailing boats of hull length greater than or equal to 6 m)

Given it is an international standard, are these figures already available for the LB22?

Thanks again

Rob

[BarraMan]

If Jacques doesn’t have that data readily at hand, I would have thought he could produce it fairly easily. If not, you can calculate it yourself from the Australian Standards, or retain a naval architect to do so.

[OneWayTraffic]

Do you actually need to show official evidence? I would think that the recommended max hp and actual amount of flotation would suffice? You built it after all. If you state that it can do x y z how who will say otherwise?

[Rob R]

Thanks, Barraman and One Way Traffic,

You have to state on the Builder's Plate which official standard was used for the calculations and who authorises that it is correct- they won't take my word for it.

From further discussion with our Maritime, I think I can get it registered without the plate. I notice that Barraman wrote about his experience in Queensland where you can't sell a boat within 5 years of building it without a plate. I'm not surprised Barraman doesn't want to sell his boat - it looks magnificent. Mine is a more modest affair, but I can't imagine selling it either. It took me 5 years to build so I want to use it for a while.

I'll find out this week whether I can register it as is.

[jacquesmm]

I did read about that and it looks like in some places, they ask for that builder's plate.
Fortunately, it is nothing like the ISO certification, it is closer to the USCG capacity plate.
Until now, Australian builders have fill the form them self, the builder can do it. The calculations are simple.
I plan to enter the data in a spreadsheet and propose the results it as an option to the plans.

Let me find the form and create the spreadsheet.
If somebody has a link, please post it. I found one for Victoria but I am certain there must be a form that covers all Australia.

[jacquesmm]

OK, I did read most of what I could find.
It is based on the usual idea that the government must protect you and will do that by adding regulations. There is nothing I can do about that.

It looks like it is required in most states.
Blank plates are available:

The general public may obtain a blank ABP plate from any one of a number of suppliers, or may contact the BIAA supplier on 07 3299 3877

The information on the plate can be "calculated" by the builder or the importer or a "competent person".
A yacht designer is competent but it looks like he must be Australian therefore, in the case of amateur builders, it will be the builder.

The good news is that we can use ABYC values (American Boat and Yacht Council) and I am an ABYC member.
The ABYC is in charge of the US capacity plates standard and I have a spreadsheet to calculate the tags.
However, in the US, we don't put capacity tags on large boats with inboards. I would still use the same standard.

I will help by providing those calculations but just as in the US, I can not guarantee that the boat will be built exactly as designed. The builder is responsible for that conformity and he can also adjust some values, using my figures as a starting point.
For example, I like to specify max. HP very conservatively for liability reasons but all my designs have transoms and hulls that can take much more power than what I specify.
Another point is that those standard calculations do not always work well with extreme boats. For example, the calculations for max. HP and number of persons take in account the width of the transom and the existence of a large aft deck (for flooding).
From memory, I think the PH18 comes out at 250 HP and 11 persons which is ridiculous. I can not go over those max. figures but I often reduce them based on common sense.
( There is also an HP limit based on maneuverability testing.)
A last point is upright flotation for boats less than 20'. I mention proposed foam locations in some of the building notes, I may have to sketch some proposed foam locations.

Based on my figures, the Australian builder can make his own plate.
He must put his name on the plate and he must state that the calculations are based on the ABYC standard: per ABYC.

It is going to take me some time to do the calculations: first I must extract hydrostatics values from my 3D model (in ORCA), copy those values to my capacity tag spreadsheet and export values in a readable format, one boat at a time.
I must also check my spreadsheet and see if it is up to date.

In the mean time, keep building, you will get the info you need.

[Rob R]

thanks, Jacques.

I look forward to seeing the numbers. I agree that common sense is more important than formula, but I am interested in what comes out.

Regards,

Rob

[fallguy1000]

Isn't this just displacement less hull weight?

2000# less 950# per the study plans, or 1050 motor, gear, passengers. If you put a heavy 4 stroke 50hp on it; those are 250#, so that leaves you with 800 pounds for passengers and gear. Or roughly 5 people at the standard, which in the US is 165# per person.

Frankly, that boat will hold more people than that safely, so I'm a little suspicious at the numbers.

I'd like to know if I'm wrong because I am reviewing my own vessel for loading as well. I have 2200 available less engines of 600, or 1600, but ten people seems easy light ship. No intent to hijack; just learn.

[jacquesmm]

Each country has it's formula but yes, it is based on displacement minus weight = total capacity but they don't calculate the displacement as "normal" displacement. It is what they consider the max. safe displacement. In the US and Canada, for boats less than 20', it is the volume calculated with the waterline matching a plane that runs from the transom or motorwell bulkhead, tangent to the lowest sheer point.
From that displacement we subtract hull weight, machinery, accessories and the weight of persons.
The weight of persons is either arbitrary or taken form a simple formula, beam by length by a factor with persons at 180 lbs each.
There is a simplified formula for amateurs here:
http://www.boatingbasicsonline.com/cont ... al/3_7.htm
and here
http://newboatbuilders.com/pages/hp.html
but professionals CAN NOT use that formula. They must calculate the real volume listed above.

My current spreadsheet is the long formula as specified in the ABYC standards. I may list the short formula values for the US and Canada but Australia requires calculations to be made per Australian formula or ISO or ABYC.

I am still looking for a short form for Australia but it may not exist.
For boats above 20' up to 26, it is a grey area but the ABYC formula is accepted.
For boats above 26' and/or inboard, we must do stability calculations.
I can do that but the result depends very much on how the boat is built and loaded.
If I calculate the LB26 with 120 gallons of fuel, 4 persons in the cockpit, X and Y weight and location of "stuff" like ground tackle, batteries, accomodations, a certain engine etc., it will be very rare that the finished boat will exactly match those figures.
They will be a good starting point and certainly sufficient to print that plaque.
You don't see an outboard type capacity tag for example on a trawler like the TW28 but you may see a plaque stating that boat was built according to ABYC standards (or ISO) and warnings like: max. 6 persons on flying bridge when underway.

Here are some figures for the XF20 using the short formula:
max. # persons = 11
max. HP = 250
but if we consider flat bottom with tiller steering, max. HP becomes 75.
I remember doing the long form for the PH18 and again obtained around 250 HP and 12 persons, it doesn't make sense.
The 1st set is ridiculous and even tiller steering a 75 HP is too much.

[Spokaloo]

I once had 17 adults and kids in mine. It was a little tight...

10 is a pretty safe max, at least from what we found. 2 families with a mess of kids, or 4 couples, are comfortable and the boat retains good running trim and speed.

E