I had a spare few hours so I built the tabletop for the bench I've been working on. The table top pretty much came out as I wanted, but I'm not 100% happy with the hinges; they'll do for now but I may try to improve them in the future.
The problem with these hinges is that they are not designed to take
the weight of the folding table leaf and anything you put on it (such as
elbows). If the hinges take the weight, the leaves bend backwards and
will eventually break, or rip out of the wood.
To prevent this
happening, I presumed that the leaves had to be butted very closely to
the main table, to allow the fiddle rails to take the weight. But when I
butted the two components too closely together, they bound when opening
and closing the leaves. I have found a reasonable compromise by sanding a
slight bevel into the top edge of the table and leaves along the joint,
to prevent binding, but it not a perfect solution. I guess it would be
possible to move the leaves apart again, and incorporate a sliding
support rail under the table to take the weight, but it adds complication
On doing some further research it seems that the only way to get a perfect counterflap when using these hinges, without a sliding support bar, is to have a thicker table profile. The photos below show how these hinges are used on a beautifully made yacht, from Rustler Yachts. I was fairly happy with my effort until I found these photos. Clearly I have a long way to go...