Pipes on board

[James Sun]

I'm going to build a 70ft fast motor boat, we need the weight of the boat as light as possible, I need engineering's comments for pipes in bilge and engine room. Is any material can be used for fuel and sea water pipe except metal which is allowed by class for leisure yachts?
thanks.

[gonzo]

What class are you building to? Also, What is the speed? That will change what the acceleration forces on the piping will be.

[James Sun]

Thanks Gonzo, this boat just need to fulfill the normal marine rule, like IMO, CE, ABYC etc.
You give me another way to think, because this is a expree boat, would run upto 50kns in some modle, how much affect of the pipes concern to the boat speed?