Converting a Lindberg North Sea Fishing Trawler to RC
by Craig Parr
(Ft. Walton Beach, FL USA)
Lindberg North Sea Fishing Trawler plastic kit. Picture courtesy of J. Lloyd International.
I'm converting a Lindberg North Sea Fishing Trawler to RC and need a motor, stuffing box, prop, rudder kit and ESC for it.
The weigh is about 1 3/4 pounds. The Robbe Compact motor, gearbox, and stuffing box combination is a possibility.
I don't know if the stuffing box and propeller shaft can be shortened. I only have 3/8 inch from hull floor to center of stuffing box hull exit.
I like the Compact because the stuffing box is at the bottom of the gear box. 8 x 1.25 volt AA batteries - NiCads. Is the Compact to powerful for the boat?
That sounds like a fun project. I have never built an RC boat as small as the one you're working with, although I will soon. I won a 1/350 scale USS Arizona on ebay for the purpose of converting to RC.
1 3/4 pounds is not a lot, especially for a plastic kit. A couple of things come to mind as outlined below.
The Robbe Compact
I like the Robbe Compact with motor, transmission, shaft and propeller all in one unit. This way there is no need for aligning motor and shaft which can be a challenge. Unfortunately, I feel it's way too big and powerful for this model boat. I don't know if you can shorten the shaft, but I doubt it.
The propeller that comes with the Robbe Compact Mini (the smallest in the series) is 35mm. I suspect this is too big for the model as well.
You're saying you're planning on using eight NiCad AA cells. Those cells will gobble up somewhere around 1/2 pound. I think this is more than you need. I would try and share batteries for the receiver and to power the model boat. Most radios use four AA NiCads, which would probably be adequate.
Instead, here is what I'd do
I would approach this project trying to keep the weight to a minimum and add lead-ballast if it turns out too light in the end. I have not converted too many plastic kits to RC, but they tend to be top heavy by virtue of the plastic.
I would buy a propeller and six-inches long M2 shaft from the Prop Shop in the UK. I have not found shafts and propellers as small as what they carry in the US.
Use a propeller the same size as the one in the kit. I'd go with a “Standard Scale” pattern.
Consider direct drive. For coupling I'd use a piece of silicone fuel line (available from your local hobby shop).
For a motor I'd look around the surplus houses for one of those small Mabuchi motors such as the FF-130RH/SH (allelectronics.com P/N DCM-368 for instance).
This motor should fit with the 3/8-inch clearance you have to the floor.
For the sake of saving weight, I'd go with an ESC (Electronic Speed Controller). They've come down in price considerably over the last few years. A good one for this sort of project is:
- Water proof
- Comes with Reverse
You don't need a whole lot of amps - I'm guessing 10 Amps peak is more than plenty. The MICRO VIPER Marine ESC by Mtroniks would work out great.
Another option is to rebuild a 1/4-scale servo, if you have a donor. I haven't done it myself, but I hear you end up with a proportional ESC.
Like I said earlier, try and use the same battery for the RC receiver and the propulsion to save weight. Also, make sure you include a fuse in the circuit for safety.
I think this could be a nice little model. Best of luck with the conversion!