TOPIC:

HI!... Well as some of you know I'm a heavy construction worker (Machine operator/labourer). We are now on winter lay off up here, so I got till end of March to be bored out of my mind.

So a buddy of mine bought two of these huge boats from COSTCO a few years ago for $49.00(CAN) each. It's basically a kids toy. In stock form it does about 8KPH on the GPS. Not a blood pressure raising experience I can tell ya.

So he brought one over to me to see if we could make it a bit faster. So 1st I took it out in stock form to see for myself what it was all about. It's 28 inches long and 8 inches wide. All plastic. Has a 540 no name brand brushed motor in it hooked to a 4 gear gearbox joined to a prop shaft via a diff outdrive. Entire gearbox has plastic gears, no bearings anywhere! It was powered by a 19.2volt NiCd battery and AM stick radio. Later I tried a Traxxas TITAN 12T brushed but it was no faster.

So here's the stock drive :

As you can see, fish are faster. lol!

So I got it back home and decided this thing needs to be faster. So change gearing? Faster brushed motor? Nahhhhhhh! Hellll with that! Straight to a EZ-RUN 4000KV, 8.5T brushless motor, and 60AMP EZ-RUN ESC, via a ZIPPY 7.4 VOLT LiPo, 5800mAh.

1st because I new the motor was going to be spinning some serious RPM ,I disassembled the stock gearbox and de-burred all the gears, and lubed everything up good with some moly grease. Then I looked at the prop shaft and realized it was suspended in two cheap plastic bushings with a ton of play. Those bushings are held in rubber bushings, I guess to keep vibration down. So I dismantled it and install 3 sealed ball bearings at each end of the prop shaft. 6 in total. Huge difference in feel and hardly any friction now.

So here's how it runs on the bench :

O.k so out to the local pond we go :

As you can see it turns like crap! Also it now bounces a lot due to the speed and it not being a true 100% "V" bottom hull. It's only "V" bottom 60% down and then it's flat. Got to work on that later.

So I wanted to make it turn better so I removed the stock steering servo, and I use that term loosely.....lol! It just happens that a stock FUTABA servo slides right into the stock servo port! I had to make up a custom servo horn and made the tie rods adjustable with modded Hornet tie rods and ball cups. It turned on a dime after this.

So I ran it like this a few times and then decided to run it on a 11.1 volt LiPo 5800mAh. It ran great for two batteries and then you guessed it! The gearbox gave up the ghost.

Got back home and tore the gearbox apart. The lower out drive gear melted and fused itself onto it's shaft.

O.k so now I've decided to scrap the gearbox all together and go direct drive like most modern RC boats.

So basically the prop shaft on this thing is just basically a long threaded bolt. So I took a HOTSHOT Gearbox drive and cut down the cup slightly so it wouldn't rub on the prop shaft bearing carrier. Then I cut the Hotshot drive cup shaft down shorter and reinstalled the flat area so a grub screw can grab again. I then took a old outdrive cup from a Redcat Backdraft 8E I had and mounted it on the modded Hotshot drive cup shaft.

I then took a Redcat Backdraft 8E front center driveshaft and cut the one ball end off. The shaft diameter is exactly 4MM. Now I ordered a brass coupling that goes from 3.2MM (motor shaft) to 4MM (driveshaft). Just waiting for it to come in.

Now since I was going direct drive, I needed to find a way of mounting the motor, since I got rid of the stock gearbox and that also acted as the motor mount. Sooooo........ to the RC cave!!!!!!!!!

O.k so I fabricated up this new aluminum motor mount that also matches the motor to the new driveshaft angle. It is bolted through the hull of the boat but will be getting epoxied later so there's no leaks. So this is as far as I have got so far. I've got a total of $10 invested in this thing so far. That was for the 3MM - 4MM coupling. Everything else I had laying around the old RC shop and garage. So this is what she looks like so far :

Now I just got to work on the hull. Anyone have any suggestions? I know I need to get it into a more "V" shape so it cuts through the water instead of trying to ride on top of it and getting it to bounce at high speed. I was thinking of epoxying a "V" shaped piece of plastic on the bottom front to back.

Really nice topic!! I like boats myself too, but like so many other things no time for it atm.
It's nice to play around with different settings, motors and most difficult setup and balance. Especially with the brushless power you can get nowadays
But after reading topic it itches to dig up my boats and go for it here myself, unfortunately the weather is too bad here for some serious water action here.
About your last question, i wouldn't put to much effort in it. That hull will never be a real fast one because it wasn't designed for it. Making a deep v hull on it, might work but it will get heavy and disrupts the balance which you will have to compensate with using lead. 1 thing i def would try is and buy a different prop. That will make the biggest difference!
Keep us posted with your boat quest

Cheers, Bram

HI!... Well I'm no boat guy at all. This is the 1st one I have ever worked on or driven. I know NOTHING about what a good prop would be? It's currently got a 50mm, plastic twin blade prop on it. I don't know what the pitch is at all. I can't go any bigger in diameter or the steering rudders will hit it at full turn. Mabey a aluminum prop? 3 or 4 blade design? Any help on this would be greatly appreciated.

I'm interested to know how it'll behave with direct drive on a high rpm motor myself, theory says it won't work, but you've already proved theory wrong!

How much time/effort are you willing to put in? - might be a cool project to do the hydrofoil thing with it, & don't bother reshaping the hull. Waterjet propulsion could be entertaining to do as well! I wonder how difficult it would be to come up with a miniature high flow + pressure pump...

HI!... Well I'm still waiting for the couplings to show up. Their coming from China so probably 2 weeks or so. I hope the local ponds don't freeze over by then lol.

We don't plan on running it on 11.1 volts so it will strictly be run on a single 7.4 volt LiPo. Doing the math on it, the boat should go about 3/4's of the 11.1's speed on a 7.4 volt LiPo. That's fast enough for this boat. I'm still going to modify the stock hull. The owner of the boat works at a plastic manufacturing factory. He's going to grab me some flat thin sheets of plastic that I can work with.