Righting Moment Calcs

[Stillbuilding]

I have had professional engineering calculations done on my proposed rig for a 65' long keeled steel cruising yacht.
The engineering was based on Righting Moment @ 25 degrees. The rigging is calculated with Nitronic rod and results in a mast 15.24" x 9.61" and wall thickness 0.28".

I was a little surprised to find the section no larger compared with some other yachts.
My background reading would suggest that traditional calculations have been done on RM @ 30 degrees.

Any comments or reservations about this? My guess is that it is a calculation which places greater reliance on the rigging strength than was traditionally the case. Is this a smart direction to be heading in? Most particularly does this produce a mast specification which may be on the light side for a cruising yacht?

Gratuitous comments welcome.
Thanks

[Brion Toss]

Hello,
First, the section depends on much else besides righting moment. For instance, a keel-stepped mast can be significantly lighter than a deck-stepped one, and a multi-spreader mast lighter than one with single spreaders. Mast material also makes a difference, as does whether it is a fractional or masthead rig. And of course similar-size boats can vary hugely in how much load they apply to their rigs, depending on stability characteristics, staying angles, etc. So rather than compare your proposed mast to others, stick with the First Question of Rigging: What Is The Load?
As for the RM@25, I can assure you that they did not design a mast for that angle, any more than the more common RM@30 formulas are about loads at that angle. Rather, both angles are starting points, from which the designer can extrapolate to ultimate loads. And both angles happen to constitute approximate likely maximum working load angles.
So there is nothing in what you have said that might indicate anything scary. On the other hand, there is a lot of information that we don't have, like factors of safety, unsupported lengths, sail proportions, etc. So if you are looking for confirmation that your engineer knew their job (and I think it's a good idea), simply have a second party, similarly qualified, look over the numbers.
Fair leads,
Brion Toss