What floats your boat.

OK, and at the same time make the whole thing more comprehensible for us more challenged types. I don't understand a word of it save what I remember about Archimedes.

 

The customer wants minimum draft, and improvements to the boat in the image.
as listed. A light boat is also wanted.
The shape of the of the bottom and area of it determines the amount of pressure from the water contact acting upon the object to make it float.
A v or round bottom creates a little more area,increased water line length also helps. Just that alone would decrease the draft of a boat.

 

You do realize that I was not addressing you, no? But while I'm taking the time, unless you have discovered 'the new physics' I'll stick with displacement being the same as dear old Archimedes described a couple of years ago, if, that is, what we are even talking about. But, I'm not really certain because your word salad makes me think we may be talking about how fluids and things that (may or may not) float in them behave in some next door universe:

"The shape of the of the bottom and area of it determines the amount of pressure from the water contact acting upon the object to make it float. A v or round bottom creates a little more area, increased water line length also helps. Just that alone would decrease the draft of a boat."

 

Hydrostatic pressure acts "normal" to the surface, perpendicular to it in other words, that is the key fact you are neglecting, Tom.

 

Increased length will, but going from flat to round or v bottom won't, it will increase draft. Instead of trying to teach people who apparently know more about this than you do, how about learning from them instead....

 

I was about to say no, then I did a quick drawing of a true V (whatever) and a true flat bottom (whatever) of the same breadth and the same volume (y1, y2 = 2') as in pic and sure enough.....

 

All else being equal going from a rectangular
immersed section to a triangular one will give you twice the draft to float this boat

 

This thread makes about as much sense as sending astronauts to the sun at night, when it cools down enough to land on.

 

That is brilliant. I have always wanted to go the sun but it was to hot. Its simple when you point it out . But how can I take decent videos in the dark. In western australia the sun actually disappears into the ocean each night so I guess I need dive gear to.

 

Yeah, I screwed the pooch on post 7, but I know what I meant when I was thought it up ( ).

To deviate from the original premise that was raised, if the "customer" wants a shallower boat, there are a number of ways to do this, particularly compared to the hideous late 40's early 50's concoction shown in the Popular Mechanics piece (my assumption). It could be longer, wider, built with a different method or a combination of several of these (and other) things. Rather than "improve" this design, the "customer" should wake up and smell the 21st century, as we've learned a thing or two since it was drawn up, particularly with V bottoms . . .

The boat pictured appears to be in the 16' range, though the hand drawn 3D view suggests a 9' tall man is driving it. There are thousands of 16' powerboat designs available, a huge percentage of these will offer what the "customer" desires. If it's simply an exercise for 8th graders, then all they need to do is stretch it's length, add beam or both and consider a building method, more indicative of the later half of the last century, rather than the first half.

About sun landings in the dark, why bother, unless the girls are better looking and intrinsically more promiscuous.

 

You can't see the steam rising off the ocean as it descends into the sea, for some reason.

 

PAR, you've changed both masses to 1600! So you're now saying a 1,600 lb boat (the v bottom) displaces 19 cubic feet, which is equally impossible!

One is 1600, one is 1200

 

I think the real issue here is the relationship displacement-wet surface, which would make sense.
A parity of a displacement hull with hemispherical sections will have a lesser wet surface (therefore less friction) than a V-shaped or flat.

 

Buoyancy can be very simple, or if desired it can be complicated.

Divide the boat's wetted surface into small pieces, each of which is small enough that the piece can be considered essentially flat and the hydrostatic pressure, P, can be considered essentially constant over the individual piece.

Now consider one of those pieces with area dA. (See attached illustration). the total hydrostatic force on that area, dFt, is the pressure times the area:

dFt = P * dA.

This force is normal (perpendicular) to the surface. Only the vertical component of the vertical force, dFz, contributes to buoyancy, and that component is

dFz = dFt * cosine(Theta) = P * dA * cosine(Theta)

where Theta is the angle between the surface normal and vertical.

Add up the contributions to buoyancy from each of the small pieces of the surface and the sum will be the total buoyancy of the boat.

Dividing the wetted area into small pieces and adding up the results for the individual contributions to buoyancy can be tedious. But remember that the hydrostatic pressure is proportional to the depth:

P = h * Rho *g

where h is the deph, Rho is the density of water, and g is the gravitational constant.

It turns out that the total buoyancy force equals the weight of the water displaced by the hull, which is the volumetric displacement of the hull multiplied by the density of water and the gravitational constant. No need to consider the variation of pressure with water depth or the cosine of the angle of surface normal to vertical, just determine the displaced volume. This is Archimedes principle.

 

Indeed.

When teaching i generally use a simple mind experiment.

Image a ship/boat floating in water. If that water is now frozen solid and you lift out the ship/boat a "hole" is left in the frozen sea. If you now fill this "hole" up with water completely and then weight the amount of water you have poured into this "hole", it will weigh the same as the ship/boat you just removed.