Boil potatoes whole. when easily pierced with a fork, drain and rinse under cold water, untill potatoes are cool to the touch. Cut them into chunks. Add the chopped onion, and cucumbers. stir in the mayonnaise and the ranch salad dressing. If your salad doesn''''t have enough mayonaise add a little more mayonnaise and salad dressing in equal parts untill all potatoes are covered. chill in refrigarator for about an hour.