We investigate here the adequate balance between hydrophobic and electrostatic interactions in the correct folding of two-stranded, parallel coiled-coils. We have used a very reduced model of rigid straight helices, simulated by means of a Monte Carlo algorithm. The amino acid side chains are reduced to the level of beta-carbons, which interact through simple Lennard-Jones-type potentials. The model is able to reproduce the association of only two chains to form dimers, when peptides with a highly regular sequence are studied. For a given value of the parameter controlling the strength of interactions between hydrophobic residues, the electrostatic interactions between charged residues are systematically analyzed. We conclude that the optimum contribution of electrostatic interactions to the global stability of the dimer is about 20%. Weaker interactions provide a substantial population of missfolded antiparallel dimers, while larger electrostatic interactions create associations between dimers. The optimized model has been tested with other simplified sequences, providing results consistent with experimental evidence.