Replacement motor TFL "Princess"

[Old School]

I am considering a new build optioning a 180 amp esc TFL "Princess". The replacement motor I am considering is a Turnigy AquaStar 4084 1050kv running 6s. Possibly the stock motor mount rails may need to be replaced to accommodate the longer motor. What advantage is there running such a low kv motor, please on 6s? Would overall amps be lower with lower temps and possibly the opportunity to increase the propellor size, or possibly run a three blade propellor? I believe the stock prop according to boat specs is a two blade 48 mm diameter (seems a little large for the standard 3660 1650kv motor). A larger diameter prop may interfere with the stock rudder placement so I was considering a three blade prop around the same diameter as standard. Other than the drawback of higher amp draw and lower maximum revolutions would a three blade offer any advantage over a two blade prop, please?

From research it seems that the Princess does not turn well to port at lower speeds. One operator fitted a second rudder to counteract this. Would perhaps a deeper single rudder impact on lower speed turns? Would perhaps turnfins help? The stock boat is not fitted with either turnfins or trim plates.

[Panther6834]

First, I don't have this boat...but, I HAVE learned something about installing a lower kV motor & installing a second rudder. Second, I'm still somewhat of a newb when it comes to FE boating. In the past year (when I bought the first of my (now) 6 boat (soon to be 7, once I build my first...currently just a hull, electronics, to and a pile of parts).

Anyway, my rescue boat is a bit (ok, more than just "a bit) unconventional - a modified ProBoat ShockWave. Obviously, this boat is designed to go fast, would overheat if it was run at a slow speed for an extended period of time...even hotter when pushing a rescue platform, and much hotter when pushing the platform AND a rescued boat...and would turn quite badly when pushing such a combo (even worse when trying to turn left, as it wouldn't turn left at all).

So...to 'counter' all three problems, I came up with (what I hoped was) a 3-part solution, starting with a lower kV motor, and a higher Amp-capacity ESC. First, the (crappy) 30A ESC Was swapped for a Seaking 60A v3.1 ESC. Second, the 2000kV Dynomite motor was swapped for an Leopard 3650 1350kV motor. Obviously, the boat runs a lot slower...but, it also has more torque, runs considerably cooler, and (because of the 60A ESC) can handle the greater Amperage draw being caused by pushing the platform, and rescued boat.

Resolving the steering problem required a little more thought...and, a LOT more ingenuity. Like you, I decided that a dual-rudder configuration eat the best solution. Thankfully, the ShockWave rudder mount was a simple design, utilizing a single piece of plastic on the inside, which mounted the rudder, as well as the strut. To determine where to drill the holes for mounting the second rudder, I temporarily "installed" the second interior plastic piece on the outside, using only the strut mount screws. This showed me exactly where to drill the additionally-needed holes. After the holes were drilled, I took that second interior piece, cut off (using a Dremel) everything but the rudder mount, and then mounted the second rudder in place. Due to the method I used for drilling the holes, alignment was perfectly matched to the first rudder, and the spacing to the strut perfectly matched the spacing of the original rudder to the strut.

With installation complete, the second half...and, what proved to be the more difficult half...was in coccidia out how to control the second rudder, AND keep it perfectly parallel to the first rudder. What finally worked was taking a couple identical pieces of carbon fiber, drilling holes through them close to each end (thus, both pieces had holes in identical locations), remove the water outlets asking the tops of the rudders, and then replacing the water outlets with the carbon fiber pieces sandwiched between the tops of the rudders, and the water outlets, with the carbon fiber pieces as straight-back as possible. To be certain the water outlets remained as tight as possible as so that the carbon fiber pieces would never move, I used red Loctite.

The final portion of swing up the dual-rudder was connecting the rudders. For this, I used a steering turnbuckle designed for a Traxxas Rally, as it had an eye-to-eye length that was 1mm longer than what I needed. Rotating the rod ends a few times at each end shortened it to the proper length. Mounting the turnbuckles to the rudders was as simple as using two M3x20mm caphead screws, two M3 Nylock nuts, and four M3 washers.

Lastly, I decided to use the two water outlets to individually cool the motor & ESC, so I drilled a second water line inlet hole close to the top of the transoms, and a second water outlet hole on the (opposite) side of the hull. The motor cooling line enters from the port rudder, and exits on the starboard side, while the ESC cooling line enters from the starboard rudder, and exits on the port side. Here's a short 6-second video showing it operational: https://youtu.be/55o61yZ8rw4

While I (probably) can't help you with selecting the best ESC & motor combo, if you use my dual-rudder configuration as "inspiration", it should give you a really good start.


~ More peace, love, and kindness would make the world a much better place

[Old School]

Many thanks

[fweasel]

Several people have hot-rodded the Princess before. You may find pictures of their builds here and at RC Groups for ideas. I've even seen one setup with the TFL integrated drive because they wanted the more scale look of an outdrive hanging off the back of the transom. You don't really state what your goals are with this boat, aside from hinting at possibly looking to lower temps and current draw. On paper, a 1000kV motor is not a great match for 6S voltage, and the increase in prop size to make up for that would not play well with the size of the hull in question here. Swicting over to such a motor would lower current draw and temps, and would make the boat much slower assuming the same prop.

[Old School]

Many thanks. Last night I read through a few past threads on the Princess. Contrary to several You-Tube videos showing the boat performing well in both speed and handling, it seems that the boat may be a bit of a dog if expecting speeds much above 30 mph. Many report poor handling and yet most videos show the boat in my opinion devoid of any handling traces although most seem to prefer right hand turns. A deeper 95 mm rudder blade seems to cure the inability to left turns.

A 1050kv motor on 6s (nominally 22.2 volts) would give around 23,000 rpm. This coupled with say a three bladed prop around 48 mm (1.4p) I would have thought would improve the boat speed and yet not impact too much on current draw. A three blade prop would also I believe cure the cavitation issues the boat suffers getting out of the hole. Would a kv around 1300 - 1400 be more suitable, please? The hull is not suited to "racing" and my intent is to increase boat speed without suffering high amps and temps.

[fweasel]

What size motor and kV are you running now? What voltage? What size and pitch prop? Is the prop stock or has it been sharpened and balanced? What temps are you seeing after a run and how long are your runs?

[Old School]

As yet I have not purchased the boat. I am simply researching what may be done to improve the boat before making any decision to purchase. The stock motor is a 3660 1650kv. Should I decide that the cost to improve the boat's performance plus the initial purchase cost outweighs the appeal of the boat then I would not purchase it. For similar cost I could build a much better performing boat with a known reputation. The appeal of the Princess is its scale looks so in reality making it go faster might be a backward step. There is a video on You-Tube with the stock boat running 6s and performance seems acceptable. Perhaps simply fitting a 95mm rudder blade might be all it needs. The manufacturer quotes a speed of 45 kilometres an hour which seems to be close to what many achieve.