10. RULES FOR THE CONSTRUCTION AND CLASSIFICATION OF FERROCEMENT VESSELS

A number of countries around the world have either their own or international authorities and organisations which will apply their rules to the classification of a ferrocement vessel. Amongst those that produce rules are the American Bureau of Shipping, The Australian Transport Advisory Council, Marine Department of New Zealand, and Det Norske Veritas of Norway. The latter produced tentative rules for the construction and classification of ferrocement vessels in 1974.

Whilst working in India, the American Bureau of Shipping was approached with a view to obtaining classification on future vessels built in India. Set out below are the guidelines produced in June 1986:

"To consider a ferrocement vessel for classification the following plans and data are to be submitted for our review.

1. Drawings showing the particulars, arrangements and details of the principal parts of the hull structure, including tanks with information on height of overflow pipes, and a construction schedule giving details of material specifications, mixes, reinforcements, mortar application and curing procedures are to be submitted in quadruplicate and approved before work on construction commences.

"For reviewing the structural details of fishing vessels we would obtain required steel scantlings from our Rule for Steel Vessels Under 61 m in Length and convert these to ferrocement scantlings using the following relations:

ffc	=	Allowable tensile stress in ferrocement
SMfc	=	Section modulus of ferrocement
SMms	=	Section modulus of ABS mild steel
tfc	=	Thickness of ferrocement
tms	=	Thickness of ABS mild steel
M.R.	=	Modulus of Rupture of test sample (stress psi at which cracks of 1.100" in width appear during the flexural test)

"The value of 15,690 pounds per inches squared in the above formula is the presumed allowable tensile stress for ABS quality mild steel. Depending on the location and orientation of the particular member it may go up to 20,160 pounds per inches squared.

"These guidelines and conversion methods were designed primarily as an aid to inexperienced builders and designers. They are simplified and usually result in conservative scantlings. We are prepared to accept alternative design procedures proposed by a designer provided that complete documentation of the procedures and subsequent design calculations are submitted in conjunction with the vessels plans.

"Strength calculations based on the results of the following procedures are to be submitted with the construction drawings to substantiate the adequacy of the hull strength (see Section 4 of ABS Guidelines and relevant Standards):

a) Compressive test
b) Tensile test
c) Flexural test
d) Impact test

"Upon satisfactory completion of our review of plans, calculations and construction schedule, material testing and surveys, each vessel will be eligible to be classed * Al Fishing Service Annual Survey * AMS. The type of construction and description of the vessel will be noted in the Record."

The full set of ABS guidelines for the construction of ferrocement vessels would be available through the local ABS surveyor where the boat is to be built, or equivalent organisation which covers the area involved.

The full set of rules available would be too numerous to mention here; nevertheless, the above gives a fairly good idea as to what will be required.

The exact requirements of any one classification body may well differ from another, both in specific requirements and in cost of providing the survey and classification. Therefore, it is necessary to make contact on deciding whether or not to produce a boat to classification using the most up to date rules. It should be noted that the cost for building just the ferrocement element to rules for one vessel may well prove prohibitive.

For a guide to ferrocement fishing boat scantlings refer to Table 2, which indicates from practical experience the likely scantlings required in the upright method of construction.

Table 1
A Guide to Ferrocement Fishing Boat Scantlings

Length metres	Hull & deck minimum thickness	Welded mesh reinforcement			Reinforcing rods				Web Depth Thickness
		gauge	size	No of layers	longitudinal		transverse
	mm		mm		dia mm	space mm	dia mm	space mm	mm	mm
10	30	19	13x13	6	6	50	6	50-75	100	25
12	30	19	13x13	6	6	50	6	50-75	100	25
14	30	19	13x13	6	6	50	6	50-75	100	25
16	30	19	13x13	6	6	50	6	50-75	125	30
18	32	19	13x13	7	8	50	6	50-75	150	30
20	32	19	13x13	7	8	50	6	50-75	150	30

General Notes:-

Frame Spacing:	Will be in the range of 600-700 mm for the upright construction technique.
Wire Mesh:	Mesh can be of varied type of 22-18 gauge, providing the steel content is maintained in line with that shown in the table above.
Rod Reinforcement:	The distribution and diameter of the rods may well vary in other forms of construction technique, eg: upside down and moulded methods.
Longitudinal Webs:	These will always be required in ferrocement deck construction, as well as in hulls above 15 metres in length.

NB The above table and notes are derived from practical experience in constructing fishing boats, and may be subject to change when a vessel is built to classification rules.