$fn=200;

motoraccess_x=230;  // mm , rememeber x is along the length of the boat
  midaccess_x=400;
  rudderaccess_x=686;  
 
 intersection(){ // cut off a section to print, 3 sections just fit my printer - though they might fall over when printed vertically...
     translate([192,-100,0])cube([177,200,200]);
     translate([192+177*1,-100,0])cube([177,200,200]);
     translate([192+177*2,-100,0])cube([178,200,200]);
 
 difference()  // hull of top hatch (using above but +1mm up and out) and balls
  {                  //  minus
                      // lower boat hull + bigger hatch edge + filled inside

  union(){
   translate([0,0,51])    // motor+rudder access lip, expanded by 2mm out and up
       hull()                   // so that it can be subtracted from the hatch
            {
                // original access hatch
               translate([rudderaccess_x,-10,0])cylinder(r=32+6,r2=32+5,h=22);
              translate([rudderaccess_x,10,0])cylinder(r=32+6,r2=32+5,h=22);
            translate([midaccess_x,-28,0])cylinder(r=32+6,r2=32+5,h=31.5);
             translate([midaccess_x,28,0])cylinder(r=32+6,r2=32+5,h=31.5);
             translate([motoraccess_x,-26,0])cylinder(r=32+6,r2=32+5,h=37);
            translate([motoraccess_x,26,0])cylinder(r=32+6,r2=32+5,h=37);
  
             // spheres above surface          
             translate([rudderaccess_x-10,-10,-10])sphere(40); 
             translate([rudderaccess_x-10, 10,-10])sphere(40);
                
            translate([midaccess_x,-20,-5])sphere(50); 
             translate([midaccess_x,20,-5])sphere(50); 
                 
             translate([motoraccess_x,-22,20])sphere(30); 
             translate([motoraccess_x,22,20])sphere(30); 
          }
   }
   union()
 {   
     import("boat_combineall_nohatch.stl",convexity=10);
     
translate([0,0,51])    // motor+rudder access lip, expanded by 1mm out and up
       hull()                   // so that it can be subtracted from the hatch
            {
               translate([rudderaccess_x,-10,0])cylinder(r=32+4,r2=32+3,h=20);
              translate([rudderaccess_x,10,0])cylinder(r=32+4,r2=32+3,h=20);
            translate([midaccess_x,-28,0])cylinder(r=32+4,r2=32+3,h=29.5);
             translate([midaccess_x,28,0])cylinder(r=32+4,r2=32+3,h=29.5);
             translate([motoraccess_x,-26,0])cylinder(r=32+4,r2=32+3,h=35);
            translate([motoraccess_x,26,0])cylinder(r=32+4,r2=32+3,h=35);
         } 
         
         rotate([0,1.7,0])
         translate([0,-100,-116])   // final hack, also remove bits of hatch that went below the hull
               cube([900,200,200]);
   }
   
}

}