Moth plans

[Panos_na]

I am a Student of Naval Architecture and I am doing a last year project for my University.

The subject is about the design of a hydrofoil sailboat.
I deciced to design a Moth boat.

Because my project will be focused mostly in the hydrofoil design and appplication and not in the hull design, I need some plans of a Moth boat.

Can anyone help me?

I need the lines plans, body plan, etc, plus the exact Center of gravity of the hull.

Please if anyone can help me, let me know.

Thank you!

[Stephen Ditmore]

Go to www.foils.org
The last item under "site map" is a paper by Ian Ward. That's your starting point.

The Italian Moth Class page is
www.moth.it
They have an article on the subject posted at
www.moth.it/Magazine_dinghy.htm

The pioneering designer and most successful builder of hydrofoil Moths is John Ilett at
www.fastacraft.com
I don't know if he sells plans (or would provide you with them free if you were to offer to do research for him and sign a nondisclosure).

A thread in this forum with many participants who might be able to help you is
www.boatdesign.net/forums/showthread.php?t=2447

I've started what I hope will be a related thread at
www.boatdesign.net/forums/showthread.php?t=9695

[casavecchia]

http://www.intmoth.com/info/lines.php

[thesom]

sti zitiania gia sxedia vgikame????

zita apo to mavraki

[Panos_na]

This is a moth boat that I designed myself.

What do you think?

[zerogara]

I would suspect that you will find some plans for a Moth on the net and most specifications. I would also speculate that the design itself is not of outmost importance but the specification of weight/drag at various stages.

What you are asking about the CG is a little peculiar though! You are talking about a boat that on the average weighs as much or less than its crew, which is able to move around and effectively change the cg from one possible extreme to the other. For being of scientific importance it must be something new and innovative. Would redesigning something that exists and possibly improve its efficiency be sufficient?

Kozmas

[Panos_na]

I don't want to design something new and innovative.

What I want is to find a method for a Hydrofoil boat design.

For example, I want to find out the steps that a designer must follow, in order to design a hydrofoil boat.

One thing that the designer must know, is the Center of Gravity of the boat itself,excluding the crew.

That's why I want someone to give me some information about tha CG of amoth boat.

[Stephen Ditmore]

Moving one's weight fore & aft as required is a part of dinghy sailing, so there's no reason to assume that the LCG is static. Having said that, my assumption would be 8/15 of the waterline length (53.33% from the bow) initially, with the sailor shifting aft at takeoff to bring the total LCG to about 60% of waterline.

I'm pretty confident my first number is on target for displacement speeds. There are people who may be more expert than I on the second part.

[zerogara]

What if you were to make an assumption of the range that the CG of a Moth may be ranging between 52%-62% let's say, and use it as a variable of the model?
Even within a single design you may have variations of the CG disregarding crew position. Mast rake for example which in a Moth is a significant part of its total weight (complete rig with sail up). Boom position, etc.
You can excuse yourself with a guestimate based on these (at least as far as academics go).
Also in aircraft design models the CG with the foil plains are pretty close, while on the moth the CG in reference to the plain of the foils that produce lift is a triangle. Any kind of fore/aft rocking shifts the CG from the foil center point axis by a large percentage. Imagine the heights of 2 triangles the one with a 60' top angle the other with 170'
I hope to have thrown some ideas in there that may help you.
Keep us posted!

[Panos_na]

In order to find the CG including the crew weight, you must already know the CG of the boat itself.
But it is difficult to find the CG of the boat itself, without having the boat already constructed.

[Stephen Ditmore]

Do you? Why not just decide where you WANT the total CG to be and figure the person sailing the boat will position herself (another wishful thought) accordingly?

[wet feet]

I don't know how familiar you gentlemen are with Moths.This being the case,I hope nobody will be offended if I point out that the hulls often weigh less that 10Kg,sometimes much less.Compared to the weight of the acrobat driving the beast and the other forces acting on it,the CG of the hull could probably be ignored.

[Panos_na]

Originally Posted by wet feet

I don't know how familiar you gentlemen are with Moths.This being the case,I hope nobody will be offended if I point out that the hulls often weigh less that 10Kg,sometimes much less.Compared to the weight of the acrobat driving the beast and the other forces acting on it,the CG of the hull could probably be ignored.

I think that you may have right.

It could probably be ignored, but if someone wants to do a complete and correct design of a boat, it is necessary to know the CG.

It is very sure that the CG of a Moth boat (crew included), will be within the two foils.

Can anyone give me some information about the dimensions of a Moth?
Maybe the length of the hull and the L/B

[Robjl]

Panos,
I find it hard to believe that a student in their final year of Naval Architecture can't calculate the CG from basics? What have you learnt?
It is a simple arithmetic exercise, (usually on a spreadsheet) and has been described on other threads.
However you seem to be stuck...
I would estimate the CG to be about 5% aft of the centre for the hull only then add rig etc.
Have you tried using the search facility in this forum to research centre gravity?
But as others have said ... It's not going to make much difference due to the weight of the crew.

Cheers.

[Panos_na]

Originally Posted by Robjl

Panos,
I find it hard to believe that a student in their final year of Naval Architecture can't calculate the CG from basics? What have you learnt?
It is a simple arithmetic exercise, (usually on a spreadsheet) and has been described on other threads.
However you seem to be stuck...
I would estimate the CG to be about 5% aft of the centre for the hull only then add rig etc.
Have you tried using the search facility in this forum to research centre gravity?
But as others have said ... It's not going to make much difference due to the weight of the crew.

Cheers.

Of course I know how to calculate the CG of a boat.

I am just asking if someone has already plans of a Moth boat that has been constructed, in order to help me save time.

That's all my friend!

Also, I am seaching to find information about Moth boats (like L.O.A. , B, etc)