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Installing the Prop Packing Tubes

(Original Article by Phil Sensibaugh, edited by Bill Pickl and Strike Models) Note: this is one section of a comprehensive model warship construction manual originally published on the BDE/RC website. This section is applicable to both Big Gun and Fast Gun combat.

This article does not discuss how to make the packing tubes or prop shafts. That is a topic of an article in the Drive Train section of this manual. Before you get started locate the position of your rear cannons in your hull set them inside and determine approximately where you want to locate your motors and where you want the packing tubes to end. This will eliminate the need for modification of your prop stuffing tubes later on when you begin installing the hardware into your boat.

Installing prop shafts and packing tubes is far less difficult than most builders make it. An important thing to remember is not to be overly critical when cutting a hole(s) in you hull for the prop shafts. The holes will probably be in the wrong place no matter how much time you spend thinking about anyway, so just cut them. Oversize holes are easier to fill later.

If you have a wood frame hull you can install the prop shaft packing tubes before or after the hull is sheeted and fiberglassed. Due to the nature of the Iowa prop and skeg arrangement I chose to install them first. Just remember that it is very important to determine how and where your cannon will mount in the hull before installing the packing tubes, otherwise you will surely install them in the wrong place.

The upper photos show how the packing tubes were aligned parallel to one another and level, glued to a wood dowel that was carefully measured and marked. If you are using a fiberglass hull and brass stand-off supports for the ends of your packing tubes then use the dremel to cut a slot for your brass stand-off support near the end of the packing tube. Slide the brass support into the slot as you  tilt your packing tube in place and glue to the wood dowel. Ribs were ground away as needed to allow the tubes to lie level with one another and fit in place at a slight downward angle. The tubes were secured in place with epoxy putty, which also reinforced the ribs that were ground down substantially.

If you are using the brass stand-off support for the end of your prop shaft and have not yet sheeted the bottom of your wood hull then glue cross support between ribs so that you have something to glue the supports to.

Wood sheeting was installed around the tubes and stand-offs (editors note: the above article on wood hull construction suggests the use of hardwood strips instead of balsa wood sheeting), but a small space was left open around the rib. This hole was filled with epoxy putty, which is a great water seal and also gives a nice appearance to the hull and looks like the packing boxes on real ships.

The third photo shows how the over size holes cut into a fiberglass hull were filled with epoxy putty. It also shows the extreme angle on the coupling for the motors that was required to allow the cannon to fit between the motors. As it turns out, the center motor was still in the way of the stern cannon and had to be removed and installed “backwards” above the packing tube using an o-ring drive or gear drive. The motors are installed by attaching small sections of brass tube to the hull with epoxy, then slipping plastic wire ties through the brass and around the motors. This is a system that has proven to work very well.

The bottom photo shows the running gear of the Scharnhorst, which is one of the most difficult ship hulls to outfit. Three props and two rudders fit into a very small space, but it can be done.