New forum member (equivalents in foam to 9mm marine ply?)

[Initial_G]

Initial_G, it is possible that by placing plates in a lighter material, and certainly less strong, you have to put more reinforcements, and stronger. It is therefore difficult to judge whether the okumen will result in a lighter vessel or not and, especially, would be impossible to know the difference.

From your answer, I deduce, as meranti is harder and more dense then okoume, that with meranti the boat would be heavier when using the same construction/thickness/panels then it would be when using okoume, but it would be stronger ?

 

[TANSL]

No, I do not say that. What I'm saying is that you can not guarantee anything and even less to speak of percentage differences .
If the structure of reinforcement is maintained, with thinner plates meranti (which is stronger), it can achieve an overall structure that may or may not be heavier.
The designer should calculate the design pressures on the structure which are the same regardless of the material used. Then calculate the required thickness, according to the properties of each material, to withstand these pressures. Therefore, the structure does not have to be neither stronger nor less. In either case it will be just enough to withstand the design pressures (which is always the same).

 

[rwatson]

Initial_G, it is possible that by placing plates in a lighter material, and certainly less strong, ....

When boatbuilders design plans, they dont specify what type of marine Ply to use.

Why ?

Because the mechanical characteristics are not that critical.

This is why the majority of plywood constructions have a fibreglass layer for the physical properties where plywood could potentially be weak.

I have never seen the wood variety of plywood being part of a plan requirement.

 

[TANSL]

When boatbuilders design plans, they dont specify what type of marine Ply to use.

Why ?

Because the mechanical characteristics are not that critical.

This is why the majority of plywood constructions have a fibreglass layer for the physical properties where plywood could potentially be weak.

I have never seen the wood variety of plywood being part of a plan requirement.

It is possible. You seem to have experience in this type of construction, but do not know if you have it in its calculation. Although I find it strange, I'll believe what you say and I´ll think about the real reasons why designers work as you say.

 

[Initial_G]

Thanks for all the replies

Another question if I may:
The plans require a Unidirectional glassfiber 900gr/m² to be used
Question:
Anyone have an address (preferably in Europe) where I can get that?
or:
Could I use Biaxial 900gr/m² instead
or:
Double the layers and use 450gr/m² unidirectional

thanks

 

[whosail]

Initial_G I to am a brand new member. My plans are to build a Ruth wherry however I do not no how to post questions. Can you help an old man out?

whosail

 

[Initial_G]

Hi Whosail

just go to the main forum page, select the part of the forum u want to post your question in and hit the button "New Thread"