A Thames Racing Skiff is a wooden hand built craft of a design which has been seen on the Thames and other waterways for over 100 years, and which remains virtually unchanged.
In an attempt to make racing as fair as possible it was decided that the boats used as racing skiffs should be built of similar dimensions and for side by side racing they should be matched sets. To achieve this, in June 1965 the SRA appointed a Sub-Committee to record the leading dimensions of the affiliated clubs’ racing skiffs and sculls in current use and to make recommendations for standardizing their dimensions and form of construction. Today we have a set of “recommended dimensions” that we ask boat builders to follow for all new skiffs.
The SRA has also provided guidelines regarding the construction and dimensions of the sculls. All the details can be found in the Skiff Racing Association’s handbook.
You can also find a little more information on wikipedia