We　consider　a　hybrid　three-mode　optomechanical　system　where　one　mechanical　oscillator　couples　to　a　second　one　via　a　Coulomb　force　and　to　a　cavity　mode　via　an　optomechanical　interaction.　It　is　shown　that　stationary　cavity-mechanical　entanglement　can　be　achieved　by　effectively　cooling　a　Bogoliubov　mode　via　the　intermediate　mode　acting　as　an　engineered　reservoir.　The　entanglement　can　be　maximized　by　carefully　balancing　the　two　confronting　effects　of　the　ratio　of　the　effective　couplings.　Moreover,　we　analyze　in　detail　the　effects　of　the　nonresonant　terms.　It　is　found　that　while　the　stability　zone　of　the　system　shrinks　in　the　parameter　plane　for　large　cooperativity,　the　maximal　entanglement　is　not　significantly　reduced　by　the　nonresonant　terms.　We　numerically　optimize　the　ratio　in　the　stable　region　and　obtain　remarkably　strong　entanglement　in　the　large　cooperativity　regime.　©　2015　American　Physical　Society.