Bronco Type XXIII Coastal Submarine
December 2025. Trying to bring this page up to date.
Table of Contents
Click on the link to take you to the section of interest.
1 Sanding the Hull
2 Rudder Service Cover
3 Rudder
4 Rudder Shaft
5 Rudder Foundation
6 Rudder Installation
7 Aft Dive Planes
8 Forward Dive Planes
9 Finishing up on the Dive Planes
10 Bow Section
11 Stern Section
12 Radial Joint
13 Joining Hull Halves
14 Prepping for the Hull Cut
15 Gluing the Deck Sections Together
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Section Heading
Text and information, with pictures below
Sanding the hull
May 2025. The hull will need to be sanded now or later. Sanding now with the hull in smaller sections will be easier. I used 220 grit sandpaper and emery boards, getting into areas as close to the weld lines and other raised parts as I could. The hull will be treated with conditioner or solvent prior to painting.
Rudder Service Cover
May 2025. The area above where the rudder is located has a ‘hatch’ which needs to be cut out and cleaned up. The hull halves were clamped and held together with rubber bands. Solvent was applied only to the section where the hatch halves come in contact with each other. The backside of an Exacto knife was used to score the hatch perimeter indentations to separate the hatch from the hull. Before starting I did a sample slice in scrap styrene to see how wide this cut will be. It amounted to about 20 thousandths. The only detail lost was the indentation indicating this was a hatch. The edges will be cleaned up and the method to keep the hatch in place will be done a a later time.
Rudder
May 2025. The rudder halves have nipples on either end to act as a pivot as a display model. These nipples were removed and openings were made on both ends and on both halves to accommodate a square brass tube. Spacers were applied to one rudder side as a glue point for the rudder tube then the brass tube was tack glued in place with CA. The rudder was held together and two 1/8″ holes were drilled into one end of the rudder. A mixture of epoxy was then applied to both halves and styrene solvent was applied to the edges. The halves were folded together and additional solvent was applied to help seal the joints. The rudder was clamped and held in place in a vertical position. A pick was then dipped into the epoxy mix and drops were placed in one hole until the remaining space inside the rudder was filled with epoxy. The other hole provided an escape for air displaced by the epoxy. Near the end as the epoxy filled the cavity, a pin was used at both openings to help any additional air escape. Then it was left alone overnight for the epoxy to settle within the cavity and to harden. The next day, baking soda and thin CA was used to top off the hole and level it out with the outside of the rudder. Then it was sanded and Nitro-Stan was used to fill any small voids. and sanded again.
Rudder Shaft
May 2025. The solid brass rod I had on hand was metric so I had to ream out the inner square brass tube. With the limited room available for the rudder arm, the arm was made from brass sheet. Two holes were drilled then the brass sheet was shaped with a Dremel abrasive wheel and files. It was then soldered onto the shaft. A small section of brass tubing was also soldered in place as a spacer. A brass mounting plate was made which had two holes, one for the shaft and one for a securing screw. A small section was also added as a guide for the the shaft. In the second to last picture you can see all of the parts. The last picture shows a partial assembly. For now the square brass tube slips onto the shaft with a friction fit. The outer brass tube is already fixed in the rudder during the previous step.
Rudder Foundation
May 2025. The lower foundation is three sections of glued styrene and shaped to fit. The hole was drilled and a brass tube was inserted. It was then glued into place.
The upper foundation has one hole for the shaft/square tube. The hole is big enough for the inner square tube to fit. It was adhered to on side of the hull with solvent.
Rudder Installation
May 2025. Installing and removal of the rudder into the hull is very easy. Insert the shaft through the upper mounting plate. Slide the inner square brass tube onto the shaft. Hold the rudder in position and insert the shaft assembly through the upper foundation, through the rudder and slide the shaft into the bottom foundation. Then insert the screw to hold the mounting plate.
Aft Dive Planes
May 2025. The forward and aft dive planes needed to be modified so they are working dive planes. The opening on the end was enlarged to accept a 3/32 brass rod and a spacer was added on the opposite side to this hole. The end of the rod was filed down to the halfway point. One for each aft plane. They were filed down to a lap joint so that each lap joint fit snuggly together within a brass tube with minimal deflection of each rod. Notches were also added to be secured with epoxy. Epoxy was filled within the dive planes the same way as the rudder.
Three sections of tubing were cut to length, two to be mounted to each hull and one acting as a pivot for the push rod.
Forward Dive Planes
May 2025. The forward dive planes were done the same way as the aft dive planes and the rudder. One difference was adding a spacer to the side against the hull to narrow the gap between the dive plane and the hull. To beef up the thickness of the hull for the stuffing tube a section of styrene was added to the inside of the hull. Thickened Epoxy was then used to glue the stuffing tube in place.
Finishing up on the Dive Planes
June 2025. Here you can see all of the tubes Epoxied in place. And the finished dive planes.
Bow Section
June 2025. I am going to be doing something different with the hull sections. Since I plan to have the torpedo doors open and close via radio, I will need to access the area in the bow in order to service them should they need it. Therefore, the four hull sections will be held together with machine screws. The bottom of the hull I will use 2-56 machine screws and the more noticeable top of the boat will have 080 machine screws. To begin, as always, test subjects are tested in order to verify the functionality. Weld•On 4 solvent is my go to solvent. A test piece of styrene and acrylic were attached together and holes were drilled and tapped for the machine screws. Moving on, tabs of acrylic were made which were attached to one side of the hull with solvent. Blocks of arylic were used in the oddly shaped bow. Once all of the acrylic was in placed the hull halves were secured together and holes were drilled and tapped for the appropriate machine screw. The holes were beveled with a reamer-countersink tool to have the machine screws even with the surface.
Stern section
June 2025. I cannot seem to find pictures of bolting the stern section together, so this is a placeholder if I do find them. The stern section was done the same as the bow section.
Radial Joint
June 2025. The radial joint is where the bow and stern sections will be joined together. I could join the starboard sides together and the port sides together, but I’m going this route. To strengthen the joint I’ll be backing it with a strip of acrylic which requires it to be shaped to fit. With the bow section bolted together a temporary bolt was added to hold the deck together. The acrylic strip was heated with the heat gun then pressed into position. Repeated heatings were done. I then cut 2.5″ templates on my laser/engraver to determine where the cylinder would go so I could estimate where the hull will be cut for the deck opening and where to cut the acrylic strips. Backlight was used to find the area that the acrylic would be glued to. The acrylic strips were cut to lenght and glued with solvent into position.
Joining Hull Halves
June 2025. Once the acrylic strip was glued to the hull, the forward and aft sections were held together and holes were drilled and tapped for 2-56 machine screws, three on each side. The screws held the hull together fine and the hull is lined up great front and back.
Prepping for the Deck Hull Cut
June 2025. The location of the hull cut for the deck was drawn on the hull sides. This was easy as the sides are a straight even line. An aluminum angle was used as a straight edge. The forward and aft cuts were drawn using a flexible ruler and the more difficult two inch aft cut connecting the side to the aft cut was drawn.
Gluing the Deck Sections
June 2025. The deck will be removable to insert and remove the sub-driver and access will be needed to the interior. Solvent was applied ONLY to the area to bind the left and right deck sections together. Once the solvent was dry, the joints were sanded.
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