What floats your boat.

When you do add to the equation the depth and direction of the surface you get the right answer. Which would also mean flat is best.

 

No, I've read enough to make this the last waste of my time. Bub-bye!

 

Could you explain why you posted the link to it here?

While K-12 school students doing the experiment will probably understand correctly by making simple observations, the text on that page should be reworked. As written, it's inaccurate and logically flawed.

* It has a false premise (that water pressure is meaningfully less 6" from the surface than 18" from the surface which it is not.
* If true, that would actually make that sentence "This means that the more area you can give a material, the higher it can ride on the water, where the water pressure is much less." illogical. A boat hull's volume doesn't decrease with increase external pressure or increase with decreased external pressure meaningfully, or there is a much larger problem.
* The use of the term "area" is vague and apparently misinterpreted by you to mean surface area which is not correct.
* Vague descriptions are not good engineering, such as "right at the surface of the water" because these can be used to support wrong conclusions through very inexact observation. (half submerged could be "right at the surface" to one student compared with a larger cube which is also half submerged and much deeper, which can lead to an incorrect conclusion.)

Rewriting that paragraph is necessary.

 

What customer requirements make a v bottom an obvious improvement for your customer? Post 6 doesn't include any requirements for handling under power.

 

Er, yes it is. If I pull a hull from its natural 6" draft down to an 18" draft and let go the increased pressure will lift it back up. That's very meaningful.

That sentence, as it's currently written, isn't strictly correct.

It would be a good idea, yes.

 

The major factor there is an increase in displacement as the hull is pulled down displacing more water, not an increase in water pressure as the same volume is either 18" deep or 6" deep, right?

 

A present, Tom:



On the left a hull section of two triangles pushed together into a single larger triangle.

On the right the same two smaller triangles in a catamaran type arrangement.

The right hand hull shape has considerably more surface area than the left, but both have identical drafts.



EDIT: And a second example, precisely the same story, except the halves aren't triangles:

 

The actual mechanism that causes the forces that move the boat up is the pressure on the surface area.

The increased volume itself doesn't actually directly "do" anything in a literal sense, it just means that when you increase submerged volume, you must by definition increase the total pressure over the surface area, either by increasing horizontal surface area, or pressure (as in this example), or both.

You can't increase submerged volume without increasing the total pressure over the surface area.

The volume that causes the "correct" force required is, as Archimedes discovered, the volume with the same mass as the floating object.

No, the volume will increase in height by 12".... Not sure what you're asking here.

 

This thread is a "wind-up", or Tom is having a hyper-extended "senior moment".

 

I had a senior moment too

I thought "where the water pressure is much less" was referring to the difference between one cubic foot of water displacement 6" from the surface and one cubic foot of water displacement 18" from the surface.

 

Any student can withdraw from the course at any time..but you will not get your course fee $100 refunded.

If teachengineering.org can not teach our engineering students with the correct information. Where can we turn to get it right.

We are supposed to be planing a boat for a customer and his requirements not our own personal choices. and be able to prove our design with observable reasonable accuracy or we will not be paid.

If we can not get past the bottom of the hull design for a shallow draft boat to suit our customers requirements you will all lose your jobs.

Your teacher has carried out this project in real life and produced a built boat that ticks all of the boxes plus many more.

 

The about page describes it as "curriculum for K-12 teachers" not engineering students. Still it would be good if the lesson you linked was reworded to reduce the chance of leading to inaccurate conclusions.

The shallowest draft will be achieved with a flat bottom unless a shaped bottom can reduce weight by reducing the need for heavier internal structure.

 

Tom Kane, are you the "your teacher" in the last sentence? Is this an attempt by you to teach other forum participants?

 

Now you are starting to get the idea. The shallowest draft will be achieved if we reduce weight and increase buoyancy area available by the shape and material and volume of the bottom giving more surface area for the uplift pressure from the water.

 

Nothing wrong with having "senior" moments or being kept on our toes by a challenging project..the problem is getting the right information to start from and not personal theories.