I have personnaly dived in a 40 sits tourism sub-marine in monaco , 
  the sub hull was totaly made in a transparent resin (very thick), so i see no 
  reason why a sub could not be made in a plastic material.
   
  ---it is probably cast acrylic. As far as I know 
  exists no clear resin.
   
  On the other hand i could note that this kind of building requires bigger 
  means than the traditional stell hulls, it cant' be done in a small garage, 
  requires big moults , amtmosphere control (humidity and temperature).
   
  Steel or GRP; I think the same workshop space is 
  required. but you dont wake up the neighburs with the angle 
grinder.
   
   
   
  Personnaly i am really interrested in the result cause i would like to 
  built an un motorized sub five meter long designed to welcome divers for 4 
  days with the possibility to reduce the pressure up to surface pressure 
   at the end of stay.
   
  --Do you have a drawing?(post to moki) what 
  hull diameter. It schould have some comfort for a long deco stay.
   
   
  or maybe am I a stupid newbie dreamer that has nothing to do 
  here ??????
   
  --No
   
  regards, Emile
   
   
   
   
   
   
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