This is a relatively simple instructable about how to make a PlayMobil boat into a Radio controlled Jet Drive boat.
Step 1: The Jet Drive Explained.
So you should be able to pick one of these jet drives from eBay. i picked up a couple a few years ago but i checked and they are still around. the jet drive comes from a boat made by "NQD" if you search for "jet boat nqd" you should find it, the unit should cost around £12. The beauty of a jet drive is that it is a complete boat propulsion unit in one! it has the motor, shaft, propeller and rudder all in one. The bad bit is that it doesn't have reverse and you need to fit it into the chosen hull. Also a consideration is how safe this is for my little boy, there is no exposed propeller to catch.
Step 2: Fitting to the Hull.
This is a bit time consuming and fiddly. i am guessing the original boat is vacuum formed and very thin, and so when you come to fit this in a boat the transom needs to be very thin to allow the real nozzle to still fit in the correct place. that is to say there is a recession in the nozzle and if the transom is too thick then you will lose this alignment. For this reason i made the transom from two different bits of ply wood, 1/32" and 1/8" the 1/8" reinforces the 1/32" the pictures how it better than i can describe.
The bottom (hull) section of ply is also laminated from two pieces of ply to give the required thickness.
To fit the unit in the hull you just need to cut a hole to allow the wood to slot into place, then once you are happy with the fit make up another section of wood and stick to the top surface of the hull piece (of wood) to allow the unit to be lapped into the hole.
Step 3: The Controls
There really isn't much to this boat once you have fitted the unit into the hull then you just need to add a servo to move the jet for steering then add the esc and receiver and battery. you can see in the picture how i did this by making a 3 sided cradle then gluing down a top with the hole for the servo.
The ESC is a brushed esc and is a hobbywing 1060. which will do up to 60 amps so is a bit overkill but works fine. it is also easy to set up with just two jumpers to set the required battery type, and the other for selecting forward/reverse/brake.... for this application you only need forward.
For the steering i used a piece of piano wire for the link, but its worth pointing out that you need only a very small amount of travel and if you have to much you can end up pulling the arm off the jet nozzle.
Before i put the top back on the boat i filled the front section with two part expanding foam.
Step 4: Running
When i first put this on the water i was very surprised at the amount of steering, just the slightest movement of the stick would send the boat around in circles. So very quickly i set up limits and the rates to limit the movement at the center point, once that was done i stood a better chance at see how fast it went.....
And the result is Very Fast, but not for long. as you can see in the pictures the boat jumps out of the water, now that might seem cool, but for a jet boat that's not very good, as soon as the boat leaves the surface of the water it stops sucking in water and falls back down resulting in a big splash. then the cycle is repeated! until the hull partially fills with water and the back end sinks!
I played around with the position of the battery and moving it forward helped a bit, but i think in the long term i will have to put a couple of trim tabs on the back to help keep the nose down!
And maybe look at putting in some windows and making a cover for the back!