Gaff Rig conversion

[Sulian]

Hi,

I'm in the process of restoring a 24' boat with a 30' Fractional Bermudan rig, unfortunately it requires a new mast, boom, rigging chainplates and sails

The upshot of this is that I'm thinking of converting to a high peak(?) gaff rig (no topsail), only because I like the look and I think it will suit the finished boat.

Does anyone know of an online resource or book to assist with the calculations required to convert successfully. I think the things I'm gioing to need to look at are; mast height, mast/boom/Gaff diameters, Centre of force, will I need to alter the mast position, mast rake and approximate sail area of the gaff.

As the dimensions of the hull, displacement and ballast etc are in effect known quantities will I be able to calculate the above?

Other things to consider are the necessity of a bow sprit to enable a fatter (longer foot) or second jib to be fitted due to the loss of mast height,

Having overheard mutterings along the lines of 'convert to a gaff rig... are you mad!' I'm also bound to ask the question.... are they right?

Your thoughts..?

Thanks in advance

[TeddyDiver]

There's no single source for that kind of conversion.. To make it succesfully there's a thousand things to consider, calculate, design and build.. so even if you mange in such work with an outcome you be proud those "besserwissers" muttering might still be right ;)
If you consider thou to continue something to read..
John Leather: TheGaff Rig Handbook
Tom Cunliffe: Hand Reef and Steer
Ted Brewer: Understanding Boat Design
Larsson & Eliasson: Principles of Yach Design

Chears! Teddy

[PAR]

It's a fairly simple conversion for a professional, but you'll have to acquire a considerable amount of knowledge to pull it off with some level of success. It's likely things will have to move around a little, making for structural considerations. Some of these things may include mast step, chain plate locations, tie rods, bulkheads, etc.

It's certainly possible, but you should find professional help.

[alan white]

A lot of things have to happen. CE is obvious, but so amny other issues have to be dealt with. The sail shape is one thing. Then there are many other rigging decisions to make, all of which require a person familiar with setting up the gaff.
A good idea would be to look at some old gaff designs (plan view) and copy a Geary, Herresgoff, Alden, etc., for shape, rigging details, and so forth.
The masters knew how to design gaffers. Then scale the rig to fit your proposed CE. There are lots of little ideas that make gaff rigs work well, and once you have specific questions, ask away.
I think gaffers look great. especially with wooden spars, which are cheap to male.

[Sulian]

Thanks for the information.

I've ordered 3 of the books suggested by Teddy and I'll peruse those when they arrive.

My only real worry is the mast step, I've got about 6 inches aft and 12 inches forward to play with before bulkheads may need moving. Chainplates etc aren't fitted at present so no issue there.

I've found some older gaff designs that I can scale and hopefuly with the information found in the books i may be able to move forward with this idea.

I'll update as and when.

Thanks again
Sulian.

[M&M Ovenden]

Elements of yacht design from Skene would be a very helpful book. It is an old one, originally published in the '30s so mostly applied to gaff rigs. It will be helpful for the sail plan but also for proportions of your wood spars. John Leather and Tom Cunliff are good books but will not give you so much the information on sizing and proportions as you will find with Skenes.

http://www.amazon.com/Elements-Yacht-Design-Seafarer-Books/dp/1574091344

Murielle