What is the difference between "practical" and "practicable"?

I use both the terms practical and practicable frequently, both in a social and professional environment, but I'd like to check the validity of my usage. To me it seems that "practical" could readily be used in each case where "practicable" is used, but not the other way around.

For example:

This is a practical solution.

and

The solution is practicable.

It seems slightly out of place to say practicable solution, but still correct to say The solution is practical.

So my question is: What is the usage difference between practical and practicable?

Solution 1:

I think "practicable" is something that could be implemented rather generally, a thing that can be put into practice.

"Practical" is an adjective defining something that is useful or reasonable to do.

Aaaand, it seems good old Webster agreed. (From Webster 1913 ed)

Practicable (Page: 1123)

Prac"ticable (?), a. [LL. practicare to act, transact, fr. L. practicus active, Gr. : cf. F. practicable, pratiquer to practice. See Practical.]

1. That may be practiced or performed; capable of being done or accomplished with available means or resources; feasible; as, a practicable method; a practicable aim; a practicable good.

2. Capable of being used; passable; as, a practicable weapon; a practicable road. Practicable breach (Mil.), a breach which admits of approach and entrance by an assailing party. Syn. -- Possible; feasible. -- Practicable, Possible. A thing may be possible, i. e., not forbidden by any law of nature, and yet may not now be practicable for want of the means requisite to its performance. -- Prac"ticableness, n. -- Prac"tica*bly, adv.

http://machaut.uchicago.edu/?resource=Webster%27s&word=practicable&use1913=on&use1828=on

Practical (Page: 1123)

Prac"ti*cal (?), a. [L. practicus active, Gr. fit for doing or performing, practical, active, fr. to do, work, effect: cf. F. pratique, formerly also practique. Cf. Pragmatic, Practice.]

1. Of or pertaining to practice or action.

2. Capable of being turned to use or account; useful, in distinction from ideal or theoretical; as, practical chemistry. Man's practical understanding." South. For all practical purposes." Macaulay.

3. Evincing practice or skill; capable of applying knowledge to some useful end; as, a practical man; a practical mind.

4. Derived from practice; as, practical skill. Practical joke, a joke put in practice; a joke the fun of which consists in something done, in distinction from something said; esp., a trick played upon a person.

http://machaut.uchicago.edu/?resource=Webster%27s&word=practical&use1913=on&use1828=on

Solution 2:

Practicable typically means that it's able to be implemented, or can be used in practice. Practical generally refers to the relative value of a given action, but it may not be practicable. Example: you're a doctor on a Disney cruise ship and all the children in the daycare are infected with airborne Ebola. The practical solution would be to close the door and let them all die, since allowing them out would almost certainly result in hundreds of additional deaths. However this isn't practicable since the parents would almost certainly react emotionally and take action to "rescue" their children. Instead you let them out and isolate them in their cabins, but everybody dies anyway because the Ebola is airborne. Thus practicable isn't always practical.