Building a laminated wooden Mast

[Dominique]

I have a 49 ft ferro-cement yacht which is not finished. It is supposed to be ketch rigged, but the mizzen is not fitted. The main is 13" taller than the mizzen should be, so I am intending to move it to the mizzen position (chain plate & compression post are allready there) and build a wooden mast for the main. A friend owns a vacant block of land 75 metres from the universitie's jetty which I will be able to use, to step my mast as I am a staff member there. I was a carpenter for ten years before studying computer science, so that and cost are the two main resons I am wanting to build a wooden mast. I also have access to all teh tools required to build a mast. The mast will need to be 19 metres long, but I do not know what section it should be, and I also want a hollow inside the mast for the wiring. I want to run external halyards.

Does anyone know how I should calculate the section required, rigging sizes etc.



Thanks in advance

Dominique.

[gonzo]

Square masts are easier to build. They are also easier to rig because of the flat sections. I'll check Herreshoff's formulas unless you got access to them.

[tspeer]

There was an article in Wooden Boat a year or two ago on building birds-mouth masts. It looked like a really slick way to go if you want a round section.

[Dominique]

Originally posted by gonzo
Square masts are easier to build. They are also easier to rig because of the flat sections. I'll check Herreshoff's formulas unless you got access to them.

I do not have Herreshoff's formulas so please check them for me.

Thank you

Dominique.

[gonzo]

I'll let you know in a day or two.

[Andy]

Check out Greg Carlsons page at www.carlsondesign.com for programs which calculate the scantlings required for a round wooden (hollow) mast based on a few basic input dimensions and preferences. 'The New cold molded boat building' by Reuel Parker has an excellent chapter on how to build the type of mast you are after, and is a superb book for much else besides with many ingenious solutions to modern boatbuilding and design.

[dionysis]

Hope this helps as well:

Very Nice!!! It is harder to figure out the correct dimensions and section for a mast like this though.

In terms of rigging dimensions and so on, i would advise getting some proper calculations done. The displacement of a 49ft ferro cement boat is not trivial, and the loads in all directions could be enormous! A failure of a component could put the boat, or worse still its crew, in real danger. The calculations can be found in 'Principles of Yacht Design' by Larsson and Eliasson, and if you cant be bothered working through them yourself then im sure a final year civil engineering student at your university would enjoy the project. You or they would need to establish the righting moment, probably by doing an inclining test, so its not quite as simple as just doing some sums. If you have a look around the other threads you should find information on doing this.

Incidentally, nice to hear about a ferro project - I spent last weekend cruising on the Firth of Clyde on a beautiful ferro boat with wood decks and interior, brass oil lamps, primus stove and all that ambience stuff. once it gets going, this boat is like a freight train, but even in light airs we put a fair number of plastic boats behind us! Fancy posting some photos of the boat? It may be possible to spot anything obvious which may hinder your plans...

[Andy]

Oops wasnt logged in for that post...

[dionysis]

I would go along with Andy's post, but add that any attempt to build your own mast will demand a steep learning curve. You do need to understand the calculations. Buy a good book on yacht design: I would recommend Skene's "Elements of Yacht Design" as a first book. This has a mast scantling method that is understandable and will put you in the ball park. It also has methods for working out your boat's righting moment etc.

Good luck, dionysis.

[gonzo]

To calculate your mast there are some necessary things to know:
*length of mast
*how many spreaders
*chainplate spread
*distance from mast step to deck
*righting moment of boat at 30 degrees
*sail area
*if it is a fractional or masthead rig

[Dominique]

On my private webpage at work I have a few photos of the yacht. I have a few more that I can put up.

http://homes.jcu.edu.au/~jc134035/ya...oto/photo.html

Dominiquue

[Robert Miller]

"There was an article in Wooden Boat a year or two ago on building birds-mouth masts. It looked like a really slick way to go if you want a round section."

Does anyone know the issue # for this article? I would like to find it.

Thanks.
Robert

[Suede]

Here is a link to a guy in Norway building a wood mast for his 42 ft....
even if the pages is in norwegian...I think he can be contacted for more info in english...
http://www.njordforum.no/kahytt_mast/mast/mast.shtml

Rgds
Olle

[dave evans]

hi, dominique. I have a 50ft ferro that I just bought and she needs a new mast.I have searched the net for plans but no luck yet..If at all possible could you email me any information that you have come across ...thanks ln advance......... d.evans@shaw.ca