Yawl mast design using Euler

[willfox]

I am currently working on a yawl design and have started thinking about the masts. With a sloop rig I have been told that shroud base x bottom panel mast compression must equal RM@30 degrees. I guess it would be safe to do this for the main sail even if it is not taking the full force of the wind pressure. How would you tackle the Mizzen? Would you think this should be designed as a proportion of the RM@30 degrees by area? I have heard that Germanischer Lloyd have a recent rule regarding this topic but I’m unable to track it down. If anyone could help I would be great full.

Will Fox

[gonzo]

That is a bit simplistic. For a wide shallow boat, it may be the highest RM. A narrow deep boat will have the maximum at closer to 90 degrees.

[Grant Nelson]

Its more complex than that... has to do with sail area, number of spreaders, beam, mast material, keel or deck footed, aft stay or not... and you need to figure mast compression, but also shroud and stay sizes...

Larsson's Principles of Yacht Design gives details on how to do this, but it a steep understanding curve due to the poor structure of the content.

There are some spreadsheets in the software section of this forum for masts with three or so spreaders, but they are also not so easy to understand, at least if you are impatient.

You could look for similar boats, and then go to some rigging supplier sites and see if they give the sizes for all the rigging for those boats. In the end you will want to have the supplier check you numbers anyways...

Good luck!

Grant