Hovercraft
Boats
SRN 6 Twin Prop
I purchased this model from ebay and it needed lots of restoration, it came without motors or electronics.
The model is based on the SRN5 but has been extended with extra ribs as per the instructions in the Traplet Publications plan. Originally it was not a twin prop design but I decided that for better manoeuvrability and control it would be better to steer the model using the twin engines rather than just relying on the rear vanes.
These two pictures show the model as it arrived, I have already re-attached the rear vanes and tried fitting a lift motor.
This is the original SRN 5
I have the plans for this model from Traplet Publications, it's quite old now but still looks good.
Build
My first objective was to get the lift motor running and decide what motor & prop combination to use. I started with a standard 540 motor and a 7"x4 prop. This combination worked quite well but I had to be very careful with motor alignment in the duct to make sure the prop did not hit the sides of the duct. I now changed the motor for a brushless model - Turnigy Track Star 2400kv, it takes between 10A - 30A when running but will happily lift the hovercraft at 15A. A suitable airplane ESC was also bought (airplane because it only has to run in one direction).
Twin Props
I had to build the motor mount bracket first, which consists of bent aluminium which has an aerofoil section, purchased from B&Q, so that when two pieces are sandwiched together you get a gap down the middle to take the motor wires but has a neat external appearance. The brushless motors are 'Floater-Jet Replacement Motor (hobby king AXN-2208-2150)' fitted with a prop converter and contra rotating three bladed props 5x4 (purchased from ebay). Along with a pair of 'HobbyKing® ™ Brushless Car ESC 30A w/ Reverse' which need to be reprogrammed to mode Two2 (use programming card it's much easier).
Connect these ESC to the 6 channel receiver using a mixer allows me to drive the hovercraft like a model car (twin screw mixer from www.mr-rcworld.co.uk) I still have the rear vanes steerable but they only work when travelling at a decent forward speed.
After initial hover testing I found more weight was needed at the front so I decide to use two Li-Po batteries, 11.1v 2550mAh weight about 220g each, one to power the lift motor and the other to power the two thrust motors. Run time is over 15mins with this setup.
The videos show various test runs.