Which rule?

[Mat-C]

Simple question...
25 foot, aluminium planing hull, for recreational use.
Which scantling rule / method is best?

[Paul Kotzebue]

ISO 12215-5
Small craft ― Hull construction and scantlings
Part 5: Design pressures for monohulls, design stresses,
scantlings determination

[Willallison]

It depends a fair bit on what you're trying to achieve Mat. ISO is probably the most widely used now, though ABS (and the Oz standards which are based on ABS) are also widely accepted.
If you're after a simple, easy to follow, conservative rule the Gerr's Elements of Boat Strength is fine too.

[Mat-C]

Thanks Paul, Will.
Paul, why do you suggest ISO over others - ABS, Lloyds etc?

Will, I'm just trying to establish which method gives a good strong structure at the minimum weight

[Alik]

Mat, ISO12215-5 has simplified method of scantlings calculations suitable for boats with LH<9m. I am sure in Your case it is the way to go.

[Paul Kotzebue]

Lloyd's Special Service Craft is applicable for yachts over 24m. ABS guide for motor pleasure vessels is applicable only for yachts over 24m. I don't think ABS or Lloyd's has current scantling guidelines applicable to recreational motor craft under 24m.

ISO 12215-5 is applicable for recreational craft between 2.5m and 24m. The ISO simplified method is fine if the boat falls in design category C or D.

[Mat-C]

Great - thanks.
Now, Can I just buy ISO12215-5, or do I need the whole damn lot....? I mean, I know I can buy just part 5, but will it enable me to do all the calcs without having the other standards to refer to?

[TeddyDiver]

Depens if you want to make the boat 100% ISO compliant or use just the scantlings..
http://www.evs.ee/Default.aspx?TabId=58&language=en-US

[Alik]

Paul, we did 15m pleasure cat to LR SSC rules. They work quite good for small craft below 24m.

Teddy, for craft below 12m compliance to ISO12215-5 is not mandatory.

[rxcomposite]

Originally Posted by Paul Kotzebue

Lloyd's Special Service Craft is applicable for yachts over 24m. ABS guide for motor pleasure vessels is applicable only for yachts over 24m.

Paul,

LR is applicable for yachts UP TO (150 ft?) All other types (cat,mono,patrol) is for below 24 meters. Anything above 24 meters is ship and LR has a different set of books for that. THe minimum scantlings of LR becomes impractical for small boats but the calculation procedure is bulletproof.

I agree ABS is for 24 meter above. They dont touch anything below 24 m.

ISO is more applicable for small boats.


Regards,

RX

[Willallison]

ABS High Speed Craft:

1/1.5.1 Application Limits
This Guide is applicable to high speed craft for
commercial or governmental use constructed of steel,
aluminum, or FRP and having V / L not less than
2.36 (1.30) where L is as defined in 3/1.1 and V is as
defined in 3/8.1.1. Applicable craft type and length
are as follows:
Vessel Type Applicable Length
Mono-hull < 130 m (427 ft.)
Multi-hull < 100 m (328 ft.)
Surface Effects Ship (SES) < 90 m (295 ft.)
Hydro Foil < 60 m (197 ft.)

[Paul Kotzebue]

ABS High Speed Craft is not applicable to recreational vessels.

This is from LRSSC:

2.1.1 The Rules are applicable to the following craft types
constructed from steel, aluminium alloy, composite materials
or combinations of these materials:
(a) High speed craft.
(b) Light displacement craft.
(c) Multi-hull craft.
(d) Yachts of overall length, LOA, 24 m or greater.
(e) Craft with draught to depth ratio less than or equal to 0,55.

So, for recreational vessels (yachts), LRSSC is only applicable if LOA is 24 m or greater. I am not aware of an upper length limit in LRSSC.

Scantling guidelines can be used outside their intended scope as long as the user understands the limitations. However, the answer to the original post is ISO 12215-5.

[Alik]

Originally Posted by Paul Kotzebue

ABS High Speed Craft is not applicable to recreational vessels.

This is from LRSSC:

2.1.1 The Rules are applicable to the following craft types
constructed from steel, aluminium alloy, composite materials
or combinations of these materials:
(a) High speed craft.
(b) Light displacement craft.
(c) Multi-hull craft.
(d) Yachts of overall length, LOA, 24 m or greater.
(e) Craft with draught to depth ratio less than or equal to 0,55.

So, for recreational vessels (yachts), LRSSC is only applicable if LOA is 24 m or greater. I am not aware of an upper length limit in LRSSC.

Scantling guidelines can be used outside their intended scope as long as the user understands the limitations. However, the answer to the original post is ISO 12215-5.

I believe that the only reason why LR SSC rules exclude 'yachts' below 24m from classification is LR's policy. They just don't want to touch this type of boats, pushing them towards harmonised European ISO12215-5. Generally ISO results heavier/stronger hulls compared with LR SSC.

[Paul Kotzebue]

Originally Posted by Alik

I believe that the only reason why LR SSC rules exclude 'yachts' below 24m from classification is LR's policy.

That seems reasonable to me as well.

[rxcomposite]

I may be wrong Paul, I do not have the LR special rules with me at the moment. I am living on a suitcase.

What I do remember is the number divides a yachts and a megayachts.