Actually, I didn't. The velocity of light in a vacuum is approximately 3 X 108 meters per second, or 300,000 kilometers per second. Ignoring relativistic effects, it would take just under 354 days to reach that velocity at an acceleration of 1G.
Relativistic effects don't become significant until one reaches a velocity of about 70% of the speed of light. Even accelerating at 1G for a period of two weeks (just over 1,200,000 seconds) will achieve a velocity of less than 12,000,000 meters per second, which is only (!) about 4% of the speed of light. Clocks on board such a spaceship might run a few seconds slow, but that would be about all.
As to the engineering obstacles, I did indeed deliberately ignore them. To take just the most obvious one, the energy required to continuously accelerate a useful spaceship (massing, say, 1,000 metric tons) at 1G for a period of only one day (86,400 seconds) would be enormous (kinetic energy, at a velocity of 850 kilometers per second, would amount to about 3.6 X 1017 joules, or the entire output of a 1-gigawatt generating station running continuously for nearly 11 and a half years - and that's assuming 100% efficiency). I was pointing out only that continuous acceleration removes the problem of supplying artificial gravity.
However, I think the term "inconceivable" is a bit too strong: "Impossible at our current level of technology" would be more accurate.
There would have to be a gigantic reason for building a manned ship that would accelerate at 1 gee for even an hour. An economic justification. Science itself will have to be content with accelerating very small robot ships to that extent, if even that.
With regard to engineering, I still think inconceivable is better since no one can conceive of a way to build the thing.
Of course the reason it is unconceivable is because our current undertanding of physics makes this "virtually" impossible. Therefore what we need is an improbability drive.