I have been away so unable to check this out until now.
It is a big boat, bigger than a Tyne class lifeboat for example.
There is an interesting photo here of one used as a picket boat:
**LINK**
and a Forum on restoring one here:
**LINK**
Chatham Historic Dockyard has one:
**LINK**
This one was apparently visiting Portsmouth:
**LINK**
Brown Son & Ferguson have three sheets of detailed model making plans (possibly used to build your model):
**LINK**
Should be enough to be getting on with for a bit!
Colin