- Suffren -

FN Suffren - Tim

3.0 units, 23 seconds, French Heavy Cruiser, Commissioned 1930

The Suffren is a larger heavy cruiser with the typical 3 units. This ship has a rather unique characteristic of 3 shafts with two rudders. Conventionally only the center prop is driven which proves for excellent turning at the slight expense of acceleration. Tim has his cruiser set up in what I would argue is the most competitive arrangement, twin sterns and single pump. Pictures are from Nats 2023.

Here the ship sits ready for transport. The Superstructure is a combination of printed, wood, balsa. The ship is fairly large so it can handle some top side weight but the lighter you can make it, the better off you are for most ships but especially inherently unstable smaller ships like cruisers.

Bow section with 4 oz CO2 bottle. Water channeling in the far bow disallows water to settle there. Tim uses a waterproof box with sensor safe RTV gasket maker to seal it. In the far bow of the ship he can not remove the deck. The removable section has a latch on the bow most portion and rare earth magnets to hold the rest in place. He uses a 1/16 inch thick magnet on the deck and a 1/8 inch thick magnet in the subdeck to provide for stronger pull. He has screws for the stern most deck that you see stuck to the magnets here so I wouldn’t lose them when I was taking pictures.

The stern deck section screws down and there is the option to screw down the mid section though generally he allows the deck latch and the bow most section’s magnets with the tripod overlap to hold the deck down and doesn’t use the screws for the middle piece.

The middle of the ship holds batteries behind the water tight box. There are test fire push buttons along the cross beam. To the stern of the cross beam there is a 550 size brushed pump and a 550 size brushed drive motor. The solenoids sit to the sides of this.

The stern water channeling is also built up fairly robustly. The far stern holds the rudder servo with gear that directly turns the two rudder post gears. He has some lead in the back that he could sink deeper into the water channeling if he wanted, it’s probably on the to-do list. Guns magazines are coiled back to 180 degrees, sometimes this leads to difficult feeding/loading but if done carefully you can get away with not having the magazines in the way of other components or having to wiggle it under cross braces to get the deck off/on. The stern deck has a latch but also has screws with threaded inserts to hold it down.

The motor with geared drive is common to battle ships. This ship has the spare weight to get away with a large motor and gear drive. Gear drive allows to set up a reduction ration to maximize torque.

Position of rudder posts.

Position of internal components from stern.

Position of components measured from the stern.

Rudders and Props, the outer two are non-powered “drag props.” The main drive is 5 blade.

1.25 inch props, you might be able to get more acceleration out of 1.5 inch props but turning would suffer. This is compensated for by using a 5 blade prop.

Rudders are 1.5 x 1 inch times two rudders for the allowed 3.0 square inches.

Rudders are 1.5 x 1 inch times two rudders for the allowed 3.0 square inches.

Stern profile with measurements. He has the drag props rather close to the drive prop. If using drag disks this can some times block water from reaching the drive prop smoothly and causing cavitation.

Another look at the twisted magazines. He has little hold downs to keep them still and a hole in the deck to load.

The barbet and his clear plastic mount hold the guns at the desired angle. Generally flush to slight down angle is desired depending on the height of the ship’s stern deck off the water.

The magazine loading hold and the cut out for the pump motor have superstructure hiding them.

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