Hmmm;
I got to thinking .( I know , dangerous thing for me ). How about this . Say you want to build a ship out of plastic . You know what you want . There's just no plastic model of it . Shoot , you can do wood ( it's been done for hundreds of years after all ).
Nah ; Don't want to have sawdust all over the small apartment . So use plastic .You can do this one of two ways . Solid frames or laminated frames . In the case of laminated frames , I have found that you actually do get more strength with laminating !
Microscopically , plastic sheet does have grain . Now , clear lexan , if cast , doesn't . This is important to know . If you choose to laminate then you must do this . One full piece on one side the same , split in two , for the middle pieces and another whole piece for the other side .
Of course this is for larger scales . Smaller scales can be handled by cutting the frame shape out of sheet . .060 is the preferred thickness . You could use Evergreen strip and heat shape it , But , remember , plastic still has memory and like metal , wants to return to it's original shape .
With sheet you defeat this memory . Using your plans and being careful you should be able to create the ship hull . It takes a lot of patience but it works .
Want to shortcut ? How about waterlining ? This is where you build an eggcrate type structure and while building generate the shape you need . You must have a waterline and deck plate .Keel plate ( in the center .) sets the shape of sheer and deckhouse . Yes folks , just like papermodels .
Then you do something different from papermodels .You make doublers on the edges of the frames .Then you glue shaped panels in place in each location . You can allow for bulwarks in scale by doubling the edges of the deck here and then putting scale thickness bulwarks on the upper edge .
Now , I've run out of words . Think about it and try it . T.B.