RC Boat.

I don't really know why I started this project. Few thing I guess. I've been told pergolas aren't' my thing. Having a clean up im my garage & finding some rc bits & pieces. Or I still haven't grown up & like tinkering. Or perhaps were half way though doing the kitchen up, & im procrastinating. But the biggest evil i think is ebay. Being able to buy cheep things from your comfy chair while raping Australia's economy. Perhaps i want to let my boys use / destroy it, while im watching in horror as they laugh their heads off.

I found (they were never lost) some plans on the net for a mono hull called "wildthing" from www.modelpowerboat.com and scaled them down so the hull is 500mm long. Its a deep 23 degree V, but there other cool plans also. The web site was great for sizing of motors, props, batts, & esc. So far, were in the ball park.

Below is a pic of some of the assembly. I wouldn't recommend doing it this way, i took a short cut and paid the price. Some people who make these start off with a solid piece if wood, drill / nail / screw timbers squarely across it to clamp the frame to to keep it true. Doing it the below way, i ended up with a twisted hull by aprox 3mm. Does not sound like much, but its noticeable.

 

Starting to put the sides on, and quick layout / weight check. Brushed 540 motor, cheep & nasty ebay esc (wont last 10 seconds), advertised 3.8aH (but really 1.7aH) ni-mh batts, eurgle receiver, and old std size servo to start with.

Sides finished & stand made.

 

Glass matt prep for rear, oh and moral support in the background.

Base glassed.

Mounting plate for water proof (i hope) receiver box. Brass M3 inserts glassed in & plate sitting in position ready to be glassed. Later, I changed my mind. Replaced the brass with resin, which will be drilled & tapped.

First sting via ebay. Bought an ESC from revolution.com that was supposed to be water proof. On arrival, you could see through the cable entries, and see the circuit board. Then noticed the cover was loose. Tried to do it up, but the screws would not bite into anything. Opened it up, and found the plastic broken on all 4 corners. OK, plan B. Carefully opening it up, then finding there was heaps of room between the FET's and heat sink. The gap was made up bits of thermal pad & half a tube of heat-sink compound. Absolutely rubbish. Id put money on first test drive, the FET's would have cooked, if not drowned. Then one of the receiver wires came off the PCB. Double crap. After re-working this rubbish, new heat pad, new heat sink compound & cable tied a water heat exchanger to it. Finished it off with heat shrink & siliconed up the ends. Just beware of the ESC in the below photo. Definitely not for a boat, or even a car, hang on, anything. Especially when it does not work.

Working out where the mini rudder servo is to be mounted. 

Foam in, top on, servo mount resined in, esc mounts in, and few over all coats of polyurethane resin. 

Spray putty on. And no, i don't drink that junk

First coat of Candy apple red. 

Rudder & cooling hose on.

Servo water proofed & in.

Getting there....

Top cowl prelim design.

Round 2: New top radio box plate made up to replace the brass insert one. Just drilled m6 holes in the ply, roughly where i wanted the cover screws & filled them up with resin. Then drilled & tapped m3 threads in the resin. Added a dodgy coat of satin black paint.

Outer frame & perspex made up.

Top painted & captive thumb screw.

Uni joint in & outer (stuffing) tube in. Most guys with fast electric boats will use a flex drive, and solid coupling, as the uni joints wear out too quick. See how we go with this one. This tube & shaft arrived bent in the mail. Yay.

I know, its not a stinger drive, but may be a future mod. Prop in photo is 35mm. I doubt the motor will be able to turn it, but its designed just in case, leaving a 3mm gap between the prop & hull. Props bought are sizes 27 to 35mm, all been sharpened.

Finally crammed it all in there.

Clearance for motor.

Sitting low in the water.

Well today was the first time it was dunked. Put on the 27mm prop & went down to the local park and threw it in the lake. It sat very low in the water, top of stern was level with the water, and took no water in which was a bonus. Went up on the plane easy enough. Speed wise, average, basically a toy boat & not a FE. Ran it for one minute, and tested the temperature of everything..... all good. Put the next size prop on, and away we went. This time, the motor didnt reach full rpm, then low voltage cut in on the ESC. Dead battery.  3.8aH didnt last that long. Bit disappointing over all. See what happens when my 2X 50C lipos arrive. If it is still a snail, brand name brushless motor & matching ESC...

Here is a quick video with fresh 3.8aH nimh, and the 30mm prop: RC BOAT.

Sourced some Li-ion sony cells. Used them in 3P - 3S for aprox 10V. Still haven't received the lipos yet, so lets cook the motor with these....

Took the boat out on the weekend to have a play. The 10V laptop batteries made a big difference..... for a minute, until the esc drowned / sizzled. Didn't even have a chance to try the lipo. One issue i cant work out is this boat suffers badly from prop ventilation. Especially after a corner. The back is not kicking out like it used to with my nitro, but turn fins are going on soon. Any suggestions to stop the ventilation are welcome.

Things just get better! Bought a "Carnage" 4WD brushless with lipo & charger second hand from a mate at work. This was to be a motor & esc donor for the boat. Couldnt help but have a go before it was stripped. Awsome. Well until I put the boat motor in it.

Donor 2370kV brushless, 2X lipos, 12AWG wire & custom esc. Front & rear of drive tube has been reinforced. Prop & drive dog were oversized by 0.1 & 0.2mm respectively, so new ones have been ordered to reduce vibration.

Extra brace for the brushless.

More dodgy ply & glass. Unfortunately, when i bench ran the brushless on 3S, the fibreglass around the front of the drive shaft tube started to smoke. Perhaps i will go a teflon stuffing tube?

Thanks to Justin picking up some m2 stainless threads, the turn fins on.

OK, well that was awesome & disappointing at the same time. Took the baby down the local water & gave it ago with the brushless, lipos, & 35mm prop. It sat the same in the water as before. First noticed it aerating on idle when priming the cooling pipes. Then on throttle, got big air (read that as 300mm+ up & 1m+ fwd) with barrel roll, and thank god it landed on its base. Next go, not so lucky & had to wade out through slops. Third go, took it easy with gradual inc in throttle resulting in a small wave causing it to disappear under the water. Any remote sort of speed it would turn into a sub. Hmmmm, stinnger drive next to do this properly..

Here is a link with the brushless only one lipo with a 20mm prop: Rev 2: Brushless Run.
 

Well after the last disappointing run (kinda fun having a zillion "Killer Wasps" with something that weighs 1kg), totally stripped it, to fit a stinger drive. Also found the fibre glass had torn / broken around the engine mount.

Painted & back end re-assembled.

New placement of ESC, and new ally motor mount.

 

And, what Ive been waiting for........ 2S brushless run.

 

Can't wait to try it again.

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