A 3 inch thickness for a 15.75 chord works out to around 19% thick. That sounds like an airfoil from one of the old school fun flyer models from a few years back.

It would fly OK but you're right, it would look a bit silly. As mentioned something more in the 12 to 15% range would be just fine. Download Profili2 from www.profili2.com and use the freebie version to do a NACA 0013 or so and call it good.