Spider

[Ural_RUS]

At manufacturing boats authority has insisted on installing such a "spider".
I would like to hear your opinion about the necessity of this device in a boat, subject to her operation in the Mediterranean Sea.

[Zanshin]

The Italian yacht manufucturer Cantieri Del Pardo, among others, has put these strengtheners/stiffeners in their Grand Soleil yachts for quite some time.

[Ural_RUS]

Yes, thank you, I know. Just usually so strong support to establish ocean yachts. Bavaria, Beneteau - in my opinion, do not set?

[Zanshin]

The Bavarias and Beneteaus and Jeanneaus don't have this additional stiffener, but their keel mountings are designed with the expected stresses in mind and don't need this. I like the Grand Soleil "spider" since it also supports the shrouds.

[hellosailor]

RUS, it does not matter how you put strength in a structure, it only matters that you have enough strength for the structure to not collapse.

Whether it is a monocoque design, or a separate frame chassis (what you call a spider) or traditional framed and planked construction...If your boating authority says that a hull is not strong enough and needs additional structural members, they probably are right. Generally using stiffening members like that will be stronger (for the weight and cost) than trying to simply use a stronger hull. Even metal hulls have taken damage from wave action against unsupported areas.