Narasimham wrote:

Am mechanical engineer with a composites background presently residing
in south India. After recent Tsunami disaster, toying with the idea to
help make hand /sail/outboard moter powered fiberglass fishing boats of
standard 30 feet length. Raw materials .. chopped strand mat,
fiberglass cloth, polyester resin and rigid PU foam are commercially
available locally, as is semi-skilled labour who could make boats to
pre designed drawings.

I think you first have to define the boat and it's mission a bit better
- hand (paddle/oar) powered will have to be smaller than sail or
outboard power. How much cargo (fish) will it carry? How fast does it
need to go?

Rigid PU foam is o.k. for insulation and flotation but not structural
purposes; it is too brittle and weak.

Can someone help to guide in the following ?
Shapes: Are drawings available on net? or on payment? What hull shape
is better? U? Flatbottom?

Hull shape will depend on whether it will be a planing boat (fast with
outboard power) or slow (sail or human powered)

If you hire a naval architect they will define the shape of the hull and
the construction method. If you are building more than a few boats, a
female mould (concave shape) is the only way to build efficiently.

You may also be able to purchase stock (premade) plans from a plan company.

Do Lloyds or other certifying agencies based in Europe/US have a
branch or mechanism to test and certify marine craft after fabrication
and testing when involved right from beginning stages in India?

Yes, Lloyds, DNV (Det Norske Veritas) and ABS (American Bureau of
Shipping) are the big ones.
But for a third world project they will be costly and probably not
worthwhile or needed.


If existing wooden hull shapes are duplicated but replaced by solid
fiberglass laminate or polyurethene foam (closed cell to keep out
water) sandwich, would it serve the purpose with stability resisting
wave forces with adequate margin before capsizing?

It depends on what the existing shapes are and how heavy they are built
and where the weights are located - too complex to give a simple answer
here.

For a physics picture of stability:

1) Is metacentric height a parameter to assess stability?

Yes - higher GM means higher static stability

2) Draft. On what factors is load-depth of immersion relations
established?

The shape of the waterplane area (cross section of the hull) determines
how much it will sink at a given draft.


One thought - in Mexico fisherman changed their style of fishing boat
over the past 20 years or so. Initally they used dugout canoes with
paddles or simple oars and stayed close to shore.

Later dugouts had small outboards added, and were sometimes replicated
in fiberglass.

Then the "panga" appeared, a very shallow deadrise (shallow V shape
hull) about 24-26' long. It is built in fiberglass and typically uses a
48,55, or 70 HP outboard motor. These boats are very seaworthy and
often venture offshore about 50 miles, catching up to about 1 tonne of
fish before returning home at slower speeds. Gill nets are the most
used fishing gear. These boats are beached at the end of the day or
anchored just off the beach. They are built in solid fiberglass with
some wood for rubrails and seats etc. They look like this:

http://www.panga.com/pangagallery/pangamex.html

I think they are a good solution to Mexican fisherman's needs but the
government had to offer low interest loans to allow the fisherman to buy
the motor and boat.

Good luck.

Evan Gatehouse