Originally Posted by David M
So now you have me curious. If you dont know for sure how much the boat weighs then how do you know where to paint
the boot stripe? Or is the boot stripe painted after you have pulled the ready to sail boat back out of the water?
vessels the naval architect knows exactly where a ship is going to sit in the water according to where its cargo, fuel
, water etc is located. Small boats dont have these tables? And whats real nice, is you can run these tables in reverse and determine the displacement of the vessel according to how much water the vessel draws at the bow and stern. (accounting as well for hogging and sagging with a ship..but insignificant for a boat)
I'm sort of surprised naval architects of small boats dont create these tables. They certainly have the computers
and the software
to determine displacement volume at specific drafts. This whole heated argument about determining a boats weight could have been eliminated with these tables simply by observing its draft
at the bow and stern.
So, why are these tables not created to take the guesswork out of determining the displacement (weight) of a vessel?
The proffessional NAs do a comprehensive weight study during the design process. This is used to ensure the correct trim, displacement etc. under a given set or sets of conditions.The draught/displacement tables are easy to make with the software that is used these days, but they are seldom published. What you sometimes will see published are the immersion rates in mms/ton or pounds/inch. But this is often only for a certain start displacement as the hulls are seldom vertical on the sides.
The problem is when the builders, don't build as specified, and the basic boat is heavier than it should be. This happens with both infused, vacuum-bagged and hand lay-up.
The next area of weight gain is probably the biggest problem to manage, all the things that go into the boat, be it deck hardware
, machinery, wood trim, safety gear
, batteries, chargers, whatever.
If the builder
or the owner does this in an uncontrolled manner, the end result as is often seen, is a boat that is far over the originally designed weight.
Few builders document this during build, as it is not in their interests, nor do they get paid to do it. When the owner finds out the boat is way too heavy, they can never find out exactly why, so they learn to live with the fact.
If the builder doesn't feed information back to the designer
, then the incorrect figures just keep on being used.
Originally I was under the impression that Fastcat
was one of the few meticulous builders who really did put the effort required into this, (Gideon claimed the boats are built on scales) but it seems not to be the case, if the boat suddenly weighs nearly 3 tons more than anticipated.
3 tons can not be explained by a bimini
and some extra anchor rodes IMO.