function boatcalc(){
var boat=calc.boat.value;
var depth=calc.depth.value;


var length = depth * 8;
var chain= Math.ceil(depth*1.3);

if (boat<=9)
{
var diam= '1/8" rope';
}
else if (boat>9 && boat<=18)
{
var diam= '1/4" rope';
}
else
{
var diam= '3/8" rope';
}



calc.diam.value=diam;
calc.length.value=length;
calc.chain.value=chain;
return false;
}