Crackerbox Setup

Setup Guide Lines - Wes @ gaspartsplus

If you have been considering buying a fiberglass cracker box, then consider this…. RC Boatworks cracker boxes have won more NAMBA Nationals. And it holds more records than any other cracker, obviously a proven design. Now if you already have one, then here are some dimensions for you to start with. These dimensions are from the same winning boats.

Let’s start with engine placement. From spark plug to the transom should be 19”. That is about as far forward as you can go without removing the forward bulkhead, something not recommended as this will reduce the rigidity of the hull. Mount the engine as low as you can, while still having a smooth transition for the stuffing tube.

The first things that seem to show up are the trim plates. They are home made using some 1/8” aluminum plate, stainless hinge material, and some RC car turn buckles. They extend back from the hull 3 15/16”, and are 2 ½ wide. They were made to conform to NAMBA’s rule of nothing extending more than 4’’ past the transom. They are mounted flush with the bottom. The strut is mounted on the centerline of the boat, and the centerline of the prop shaft should be about ¾” below the bottom.

The rudder is mounted 3” to the right of the strut, and the rudder bottom is 3” below the bottom of the hull. On this boat an finned strut was used.

The rear turn fin is made from some .060 stainless. It extends 2” below the hull and is 1 3/4” wide. Turn fin adjustments are needed.

CENTER TURN FIN

The skeg, or center turn fin which is mounted under the hull. It is also made from the same 1/8” aluminum as the trim plates were. Made in the same “sharks tooth” shape as the rear fin, it extends 2 ½” below the bottom, and is 2 3/8” wide. Sharpened on the leading edge, the square trailing edge is 17” forward of the transom and is on the centerline of the hull.

Now with these measurements you should be ready to go. Keep in mind the Cracker box hull because of it’s large bottom area wants to fly. This is where the trim plates and strut angle come into play, to hold the nose down. You’ll also find kicking the bottom of the rudder forward will help plant the bow in the turn.

Prop wise a lot of boats are running Prather 270’s and the Propshop 6516’s work well also. Each cracker box seems to have a mind of its own. You will have to find out what it likes, and what it doesn’t. But it will probably bring you more laughs, and more fun than any other boat.