We report measurements of the splay and bend elastic constants of 4'-butyl-4-heptyl-bicyclohexyl-4-carbononitrile (CCN47). We find K11 to be largely constant across the nematic range, with a value of similar to 10 pN. K33 has a slightly lower value with K33/K11 similar to 0.9 pN far from the transition to the SmA. In the vicinity of the SmA phase, K33 diverges with critical exponent gamma = -0.6, with K33/K11 exceeding 5 close to the transition.