24 ft "picnic cruiser" designing

And have you calculated that comparison, $ wise ? Polystyrene is rubbish as a boat core material, the fact that it seems to be your default option, is a worry, even if it would accept polyester, it would not be a sensible choice.

 

Of course, but it can also fail due to excessive tension.
I think, and I do not intend to offend but warn of possible problems, you should review the concepts about how the structure of a ship works, especially a GRP hull.

 

The problem is sheer strength - so as a core for sandwich construction it is a bad choice. Use a recognized and accepted core material - Core-Cell, Klegecell, Dyvinicel etc

 

What he mean is that the primary role of the core is simply to separate the inner and outer skins by as much distance as possible, which is true and correct.

There are other properties that have been mentioned here (impact resistance, ability to support attachments, and of course shear strength), but the primary role is just separation, so for a low performance vessel the choice of material isn't particularly critical - good enough is good enough.

Polystyrene isn't a material I'd choose, but there won't be any problems with strength.

 

Rastapop, I do not know if I've spelled wrong but, as you can easily understand, I mean the resistive element, which, as you well says implicitly, is not the core.
I'm sorry I was so unclear as to having to explain it.

 

Hirvi, a fellow around here was recently talking about using rigid foam insulation panels intended to underlay floors citing that it had a closed cell structure that liked to him a bit like end grain. I looked up one product and naturally there were different compressive strengths available. I'm sorry but I can't recall exactly what it was right now.

Edit: just noticed it wasn't a recent thread but one I'd recently been reading ... my bad!

 

Those chines forward will probably create a fair amount of turbulent flow and waves (=resistance). Also, the chines are above the waterline for most of their length, so the initial stability will be low; a bad choice for a slow speed vessel.

 

I do not see why, but maybe you're right. Could you explain a little bit your opinions ?. Thanks

 

Polystyrene or something else ?

 

solar powered V13

Rick is probably the most expert efficient hull designer in this size as a spin off of his record breaking water bike designs.

 

hirvi49

Jorma Ponkala built his Finnish Solar boat from non-structural foam.

A Google search will help you.

https://www.youtube.com/watch?v=N0NB5AVsYIQ

http://www.solarnavigator.net/solar_boat.htm

https://www.google.co.uk/webhp?sour...47GB547&ion=1&espv=2&ie=UTF-8#q=jorma ponkala

Good luck

 

It is necessary to study all things in depth and not assume that what someone has done, in circumstances unknown to us, is valid for our circumstances.
It occurs to me that Ponkala's boat, since has not clear view devices (wipers), can not navigate in days of heavy rain. Nor do we know what sailing conditions has been projected that boat and therefore the maximum loads they will be subjected its structure. The material used for Ponkala to its conditions, may be totally inappropriate for hirvis49's boat. We must therefore be very cautious with what is done and how.

 

"I think the strength won't be a problem. Glass fiber is strong and you just need to increase thickness to get more strength."


Strength is seldom the problem with GRP, stiffness vs weight is the problem.

Just making GRP thicker adds weight rapidly , stiffness very slowly.

That is why folks use a quality core material.

The hassle is should the core FAIL, there is no realistic repair .

 

TANSL,

hirvi49 has the advantage here in that both he & Jorma are Finnish, so if the gods are willing, he'll be able to make contact with Jorma Ponkala, Ylökyläntie 32, 25610 Ylönkylä, Finland.

IIRC, the extruded polystyrene used was one of the products available from http://www.finnfoam.com/applications/

 

And in the nightmare scenario, solvents or fuel infiltrates the EPS core and liquifies it !