The scaled-down prototype was due to be constructed by the end of 2014. The design will be used to create a full-scale 100-metre blade to be used on 8-10MW offshore turbines.
Project partner, the government-backed ETI, said this kind of delay was typical of a "challenging engineering development project".
Andrew Scott, programme manager for offshore wind at ETI, said, "They are now starting to build the prototype blade for testing and we are expecting to see it being tested in the summer of 2015. Effectively it is about six months behind.
"But anyone familiar with engineering and development would not be surprised to find it has slipped a bit. On the other hand it is still going well."
Negotiations are continuing in to where the blade will be tested. Scott said both the UK and the United States have suitable facilities. The blade is due to be tested on Siemens' 6MW turbine.
The design contains carbon fibre rather than the usual glass-fibre in order for the blade to deal with the greater stresses it will undergo due to its length.