If you're a military history buff or a movie aficionado, the new Alpha Patrol Boat from ProBoat Models will probably look familiar to you. This 21"-long RC vessel is made in the image of the PBR (Patrol Boat, River) gunboats made famous during the Vietnam War. A PBR was also a focal point of Coppola's classic film, 'Apocalypse Now'.
A Look at the Kit
The Alpha Patrol Boat ($250) is a ready-to-run model. Pretty much everything is built and configured at the factory. A 2.4GHz, 2-channel radio system is included. The only items you'll need to add are batteries and a charger. Four AA dry cells are required for the pistol-grip transmitter. For the onboard battery, you can use either a 6-cell NiMH or 2-cell LiPo battery. I used both types (and more) during my testing with good results.
One of the most noticeable features of this boat is the array of scale details. There are machine guns, fuel barrels, pilothouse details, and even working spotlights. It all comes together to make a very convincing PBR replica.
Even the propulsion system of the full-scale PBR has been replicated. The real PBR used a pair of water jets driven by diesel engines. This system, notable for its lack of exposed propellers and rudders, allowed PBRs to operate in very shallow waters. Swiveling output nozzles provided extreme turning authority and made PBRs very nimble. This downsized version is very much the same except that the diesels have been replaced by brushed electric motors. Small wires over the intakes help prevent the Alpha's water jets from ingesting vegetation or any other unwanted bits.
While full-scale PBRs utilized a fiberglass hull, ProBoat's version is made of molded plastic. The handrails, antennas, and other small-diameter framework appear to be constructed of painted metal rod. So there's no concern with breaking these parts during normal handling and usage.
Preparing the Alpha Patrol Boat
The only necessary assembly step is to attach self-adhesive Velcro inside the hull for securing the battery. The manual isn't quite clear about where the battery should be located. The intended location is along the centerline of the hull just ahead of the motors. I soon discovered that the factory-installed Electronic Speed Control (ESC) was somewhat in the way. The ESC's stock location would have forced me to mount the battery slightly to the starboard side of center.
Maybe the weight imbalance caused by the small battery offset would not have had any noticeable ill effects. But the solution was very simple, so I played it safe and moved the ESC. The ESC is secured to the hull with two-sided foam tape. It's a strong bond. I was able to pop it loose with a careful, but firm twisting motion. The tape remained stuck to the ESC and was still useable. I reattached the ESC to the hull about an inch further to port, but not before making a couple of other tweaks.
I think that mechanical power switches are unnecessary on electric-powered models. In fact, they just introduce a potential failure mode…especially given the unfriendly electrical conditions on a boat. I removed the Alpha's switch from the ESC, snipped the wires, and soldered them together. Now, the boat is powered on as soon as I plug in the battery. A blob of GOOP adhesive around the solder joint provides a little extra protection against corrosion.
The motors are connected to the ESC with a pair of bullet connectors. Like the switch, I thought these connectors were also superfluous. I cut the wires emerging from the ESC right at the base of each connector. I still had plenty of wire left to solder directly to the power tabs on the port motor. The starboard motor already had short jumper wires connecting it in parallel with the port motor, so I left them in place.
I was able to perform my modification to the motor leads without removing the motors from the boat. I just had to be careful to avoid touching my soldering iron to the plastic hull and burning a hole through it. It was sort of like a high-stakes game of Operation. If you choose to make the same change, but don't trust your surgery skills, it only takes a few minutes to perform a preventive "dual motor-ectomy" and play it safe.
The provided Velcro for the battery is 1"-wide. When I test-fit the suggested 6-cell 3300mAh NiMH battery in the boat, I felt like it wasn't very secure. I figured that I'd better shore things up a little in case this boat proved to be as nimble as a real PBR (it is). I didn't want the battery to come loose during a tight turn and start bashing the internal gear like the ball inside of a can of spray paint.
I kept the 1"-wide Velcro on the battery, but modified the hull side with a 4" length of 2"-wide Velcro (parallel strips of 1"-wide Velcro would work just as well). More importantly, I added a Velcro strap to wrap around the battery. The strap is routed under the 2" Velcro. A few dabs of GOOP on the corners help keep things stuck in place. With these mods, the battery felt much more secure.
I know it sounds like I did a lot of modifications to the Alpha. Keep in mind that none of the tweaks I made are mandatory. I'm sure that you could run the boat in stock form without any immediate issues. My little tweaks are intended to help make the boat a little more user-friendly and robust over the long haul. The additional steps took me about an hour to complete.
The radio transmitter was already linked to the included receiver and all of the controls were set up properly. When testing the steering system, I noticed that the servo shifted in its mount with each cycle. This could cause inconsistent steering response and make the boat impossible to trim. Once again, I used GOOP to save the day. A few blobs around the servo mount locked everything into place.
Driving the Alpha
My initial tests of the Alpha Patrol Boat took place at a local pond. I brought along a variety of batteries to try. In addition to the aforementioned 3300mAh NiMH battery, I brought an 1800mAh NiMH, a 2S-5000mAh hard-case LiPo, and several 2S-2300mAh A123 packs. The batteries are installed in the hull through a hatch on the deck of the boat. The hatch cover is attached with magnets, so access is easy. Getting the NiMH pack through the hatch requires a little flexing of the rear lip. The deck is made of relatively thin plastic, so it flexes easily enough that it isn't a problem.
The hard-case LiPo that I used requires more flexing and more force to get into place. I don't think that this particular battery is feasible for long-term use. The hatch lip is bound to break sooner or later. The good news is that LiPo packs are available in tons of different configurations. ProBoat suggests a shorter 2S-4000mAh LiPo pack that should prove much easier to use.
My A123 packs fit easily and did not require any flexing of the hatch lip. A123 batteries are not as popular as they once were. But they are still available and provide a very robust lithium-based alternative to NiCad and NiMH cells. I don't plan to give mine up any time soon.
Like the full-scale PBR, the Alpha's bottom has no protrusions. I placed the boat in the water near the bank and was ready to go. The boat scooted away with a squeeze of the trigger. The water jets pump out impressive streams of water that push the vessel along. Acceleration of the Alpha is quite good. It's no racing boat, but it has adequate power to get on-plane and move along at a respectable pace.
Because the boat is steered with vectored thrust, you have to keep in mind that you can only turn under power. But when the motors are spinning – boy does this boat turn! Low speed maneuvering authority is very good. The boat can turn in really tight circles if you want it to. If you use the same heavy-handed approach when the Alpha is on-plane, you're likely to cause the boat to spin out. With the smooth bottom and no turn fins carving through the water, high speed turns require some finesse to avoid swapping ends in a cloud of water spray.
The transmitter has a dial that allows you to set the amount of travel on the steering servo. I turned it down to about 30% throw. This helps make high-speed maneuvering less touchy while sacrificing very little in the low-speed realm. I also noticed that water conditions played a significant part in how the boat handled. The Alpha was more prone to spin-out in choppy water.
The Alpha's quirky high-speed turns should not be viewed as a negative thing. Boat-length turnabouts are scale-appropriate maneuvers ripped right from the PBR's operational play book. The spins are simply something to be acknowledged and mastered. It's a lot of fun when you do them on command. It is equally fun when you navigate a nice turn right on the verge of a spin. With a little coaching and some practice, even my nine-year-old daughter was handling the Alpha with precision.
With a little coaching and some practice, even my nine-year-old daughter was handling the Alpha with precision.
The ESC has two sets of jumpers. One jumper allows you to select whether the motors can reverse. It's a moot point with the Alpha. Even with reverse enabled, the water jets produce no discernable reverse thrust. Full-scale water jets often use thrust-reversing buckets that drop over the exhaust nozzles. Versions exist for some RC water jets. I may look into such an option for the Alpha.
The other ESC jumper sets the low-voltage cutoff. LiPo batteries can be damaged if you discharge them too low. Setting the jumper to the LiPo pins when appropriate will avoid that problem. A123s can be run on the NiMH cutoff setting.
A fair amount of water gets in the boat while running. It hasn't caused any operational issues with the electronics. But on a few occasions, the Alpha took on enough water to noticeably affect performance. I think most of the water comes in through the unsealed forward gun turret. It's basically an open port for any water spray to get in. The hull has a drain plug for voiding this water. My future plans include sealing off the water entry points wherever possible.
Water also gets trapped in the rear section of the deck. This area is recessed and has no built-in drainage. I added drain holes in the rear corners so that it will empty on its own.
Each of the different battery types that I used has a different nominal voltage, resulting in slightly different performance. While the LiPo provided the best combination of power and run time, all of the batteries offered a similar driving experience. I suspect that I'll be using the NiMH and A123 packs for most future outings since they are cheap and robust.
Right out of the box, the Alpha Patrol Boat is an impressive rendition of the famous PBR. I'm sure that many modelers will be happy with the factory-delivered performance and scale details. Others will look at the Alpha and see the starting point of an even more accurate PBR model. Those of us with a keen eye for detail will find a blank canvas begging for all sorts of personal touches.
Personally, I plan to add a crew to my Alpha. The model works out to about 1/18-scale and there are several military-themed action figures available in that size. The forward gun turret is designed to be articulated with a servo, so I'll be adding that as well. I'd also like to experiment with some weathering techniques that I've never tried. I may even decide to emulate the Erebus from 'Apocalypse Now'. I'll decide which direction to go once I get underway. I'll follow up here to report on any successes (or failures) from these efforts. If you have experience or ideas for modeling a PBR (or any other "Brown Water Navy" craft) please share in the comments section.
Terry is a freelance writer living in Buffalo, NY. Visit his website at TerryDunn.org and follow him on Twitter and Facebook. You can also hear Terry talk about RC hobbies as one of the hosts of the RC Roundtable podcast.