In article ,
Tim Watts wrote:

If tripods did not have a serious disadvantage over tetrapods, they
would have replaced the latter millennia ago, because they are simpler
to make, lighter and (as you say) easier to position.

Not entirely - they are less suitable for building work. With a tree or
a hedge, you can get the 3rd leg around the tree or through the hedge.

With a building, you can't and that puts the top, which is not as wide
as the 2 step bearing legs, well away from where you want to be.

I don't think it is a simple as "one is better". They are made for
different purposes and each suits its purpose better than the other,
mostly (there are always exceptions).

I didn't say they were useless - I said that they are NOT more stable
than tetrapods (as was originally claimed) and, in fact, are less
stable. Yes, you can fix that by increasing the base by about a
factor of two but, as you point out, that means they cannot be used
straight ahead and must be used diagonally sideways (or straight up).
I should be surprised if the tripod ladder in the link was enough
larger in all dimensions to achieve the same stability as the 10'
ladder I have - yes, the width is ample, but what is the length from
the steps to the single leg, and how far is the step from the single
leg (in a horizontal direction)? With those figures, I could easily
calculate the relative stabilities.

Returning to what you responded to - being unsuitable for many (most?)
of the uses that stepladders are used for surely counts as a serious
disadvantage?

Overall, my advice to the non-expert is "watch out, and remember
that it is as important to ensure the ladder is upright as it is for
a tertrapod."


Regards,
Nick Maclaren.