What is your opinion about choosing marine plywood for this design?

[y. erhan]

Hi friends, i designed a 8 meter sailboat to be built from cnc cut fully.
Firstly I want to use marine plywood in frames(30mm x 80mm) and planking(thickness=15mm). Can you advise me for frames strong marine plywood and for planking flexible and durable plywood?
Secondly my design's angle of vanishing is 180 degree, what do you think about that?
Thanks in advance for your helps.

 

[bajansailor]

Hello Erhan,
Are your frames really 30 mm thick, and 80 mm deep?
That seems to be a bit of an overkill for an 8 metre boat re the thickness. Similarly the 15 mm planking thickness (unless this is in way of the keel?).

Re your vanishing angle of 180 degrees, I would not doubt it, but remember that it is conditional on all hatches / portlights / vents being securely closed - and also all heavy items stowed down below need to be securely lashed down so that they do not end up on the roof at 180 degrees of heel (if they do end up on the roof, they will then contribute to the stability in the inverted state)

 

[gonzo]

Ideally, the values should show negative starting around 100 degrees or so. That would indicate that the boat will not be stable when upside down. Your numbers show the opposite.

 

[y. erhan]

Hello Erhan,
Are your frames really 30 mm thick, and 80 mm deep?
That seems to be a bit of an overkill for an 8 metre boat re the thickness. Similarly the 15 mm planking thickness (unless this is in way of the keel?).

Re your vanishing angle of 180 degrees, I would not doubt it, but remember that it is conditional on all hatches / portlights / vents being securely closed - and also all heavy items stowed down below need to be securely lashed down so that they do not end up on the roof at 180 degrees of heel (if they do end up on the roof, they will then contribute to the stability in the inverted state)

Actually i think i could not properly scantling so I went a guarantee way for open water sailboat. Maybe I need to reduce those, for now i dont know that.
For vanishing angle, I don't want to put to sides openings to increase reel degree. Thank you for answer.

 

[y. erhan]

Ideally, the values should show negative starting around 100 degrees or so. That would indicate that the boat will not be stable when upside down. Your numbers show the opposite.

Gonzo actually I didn't understand that you are saying my boat is stable or not. Thank you for answer

 

[bajansailor]

Erhan, this link should help to explain the GZ curve.
GZ Curves http://sailskills.co.uk/Stability/sailskills_stability_stability_explained_righting_GZ_curves.html
It mentions that the RNLI lifeboats (which have positive stability through an inversion) have an 'all positive' curve in similar fashion to yours.

 

[RAraujo]

Ideally, the values should show negative starting around 100 degrees or so. That would indicate that the boat will not be stable when upside down. Your numbers show the opposite.

Sorry Gonzo but I cannot understand your point...