If you have been reading my posts on the Comment Wall you are aware that I am building a fairly large R/C racing boat for autonomous offshore competition.
The R/C boat I have selected is the Zippkit VBox 2013 edition that is 46" long and 17" in beam. The boat is normally powered by a 26cc gas engine of around 5 - 7 hp, however I plan to use a brushless electric motor in place of the gas engine.
Since I do not need speeds of 50 - 60 mph for the kind of competition that I envision, I feel that a brushless electric motor of around 3 hp will be sufficient to drive the boat at around 25 - 30 mph. Therefore I have identified a Leopard 5692 1000kva 3000 watt 56 mm dia brushless motor as being a suitable candidate for my purposes.
I have decided on using twin 6S 10,000mahr LiPo batteries in parallel to power the motor. So now I am researching high current, water cooled ESCs with 180 - 220 amp capacity to control the motor.
After the propulsion and steering hardware have been installed in the hull, I plan to integrate a Pixhawk navigation controller and associated components into the hull to provide autonomous navigation.
I will begin the Project Discussion with the installation of the propulsion and steering hardware and then move on to the integration of the navigation controller platform.
The OSE Leopard brushless motor, water jacket, and motor/shaft coupler came in yesterday's evening mail so I started test fitting the motor mount in the VBox hull today. From all appearances it looks like the motor mount will locate the brushless motor in virtually the same position as the 26 cc gas motor mount position.
The outside width of the brushless motor mount is around 4.33" so I have made up a pair of wooden spacers that will go between the outside of the brushless motor mount frame and the inside of the existing 5" wide gas motor rails. The wooden spacers are approximately 3/8" thick and will eventually be glued to the existing 5" wide gas motor rails once I have the brushless motor mount correctly positioned in the hull. Pictures to follow.
Tom C AVD
Here are some pictures of the Leopard brushless motor mounted in its motor mount and positioned between the gas engine motor rails in the VBox hull between the third and fourth bulkheads:
The Motor/Motor Mount has been positioned between the gas engine motor rails at very close to same position as the gas motor. The suggested position is such that a 1/4" dia drill mounted in the motor collet will touch the bottom of the hull about 3" from the fourth bulkhead. This is accomplished by adjusting the angle of the motor and longitudinal position of the motor mount in relation to the fourth bulkhead.
Presently I have been able to position the motor such that the tip of the 1/4" dia drill is around 2.75" from the forward side of the fourth bulkhead. This requires the forward end of the motor mount spacers to be touching the aft side of the third bulkhead. The left and right motor mount spacers are 3/8" wide and center the motor mount between the two gas motor rails and will be used to anchor the motor mount to the gas motor rails.
The next step will be to insert the brass drive shaft tube and with 1/2" protruding from the transom mark the position of the end of the drill bit on the tube to locate the position of the tube bend. The tube is then heated to anneal it so that it can be bent without kinking it at the bend point. Once the tube has cooled it is inserted back in the hull and the drill bit attached to the motor is used to bend the tube upwards to the same angle as the motor in the motor mount.
More to come
Today I finally managed to get a total dry fit of the Motor/Motor Mount, Drive Shaft Tube, and the Drive Shaft Tube installed in the VBox hull.
The biggest issue was getting the correct upward bend angle in the Drive Shaft Tube in order to meet the downward angle of the motor/coupler. Annealing and bending the 5/16" dia brass drive shaft tube is a real art not for the faint of heart.
Fortunately I had two pieces of brass tubing to work with as I received a 36" long piece of tubing and I only needed 18" for the drive shaft tube. I annealed the tube with my propane torch at the position I had previously marked on the tube where a 1/4" dia drill inserted in the shaft coupler contacted the surface of the "V" in the hull approximately 2.75" from the face of the fourth bulkhead. I then attempted to bend the tube by hand to the required angle of around 25 deg. Unfortunately the bending process caused a kink in the tube at the inside radius of the bend which totally blocked the drive shaft from entering the bend portion of the tube.
After consulting with a friend in California and emailing Joe Petro, the supplier of the VBox kit, I decided to purchase a tube bending tool to attempt to get a kink free bend in the tube. I wound up purchasing a modestly priced tube bender from Lowe's Building Supply that can bend 1/4", 5/16", and 3/8" dia metal tubes.
So as to try and get a perfect bend in the remaining 18" piece of brass tubing, I practiced on the kinked piece of tubing until I was satisfied that I could get a reasonable kink free bend. I then annealed the remaining 18" piece of tubing with my torch, waited for it to cool, and then proceeded to bend it in the tube bend at the appropriate point marked on the tube.
Fortunately for me I was able to get a pretty smooth relatively kink free bend in the tube at the required angle of around 25 deg. I then proceeded to check the alignment of the tube to the motor shaft coupler using the 1/4" dia drill used to mark the position of the bend in the tube. Lucky me, the drill mated with the entrance of the tube and slipped down to the beginning of the bend without any binding. I had created the correct angle on the first try!
I then proceed to fit the drive shaft tube lateral plywood support between the two motor support rails. The tube support sits on top of the motor mount rail spacers and will be epoxied to those rails. Pictures of the installation process follow:
Tom C AVD
Since the last weekend I have made a fair amount of progress towards completing the hull. I have added the flotation pool noodles to the area between the bow and the third bulkhead and have glued the deck sheeting to the hull and am in the process of preparing the hull for its first coat of epoxy finishing resin.
Once I have applied and sanded the first coat of epoxy finishing resin I will apply a second coat and finish the hull using 400 grit wet/dry sandpaper for a smooth pit free surface. I will then proceed to apply several coats of primer with wet/dry sanding in between the coats and then finish with several coats of pumpkin orange.
Below are several pictures of the flotation pool noodles and deck sheeting:
Hull with Deck viewed from the Bow
Once the hull is finished I will finish attaching the steering and propulsion hardware and then proceed to wire up the batteries and the ESC and add the tubing for the water jackets. The addition of the Pixhawk navigation controller platform will complete the installation.
Tom C AVD
I have made a lot of progress since my last post to my Project Thread.
Over the last two weeks of February and the first week of March I laid down four coats of finishing epoxy on the hull and the deck. The instruction manual only called for two with wet sanding in between, but I had a fair amount of trouble getting a smooth surface on the hull and deck without going through to the hull wooden surface during the wet sanding. So after applying and wet sanding four epoxy resin coats I was ready to paint the hull.
The first step was to apply two white primer undercoats with wet sanding in between and then apply several coats of the final color (real orange) with buffing in between the coats.
Here are a few pictures showing the primer undercoat followed by the first final color coat on the hull:
I still have to apply the final color coat to the deck and the sides of the hull and then go back and apply a second color coat to all surfaces with buffing in between the coats. It takes about 48 hours for the top coat of paint to dry between applications so I will not be done with the final color coat until Monday evening after which I will apply several coats of a crystal clear matt spray to protect all exposed surfaces. I will then be able to attach all of the propulsion and rudder hardware as well as the motor, ESC, and cooling lines.
Tom C AVD
Tom, Lookin good. You will have no problem seeing that out on the water. Boats are a lot of work.
David R. Boulanger
Thanks for the kudos, much appreciated. It will definitely be hard to miss during competitions:-)
Yes, if you want to do it right, it takes a lot of time to prep the hull for painting and I still notice slight imperfections that did not appear until the final color coat was applied:-(
I plan to add a set of black racing stripes up the side and across the deck ahead of the motor cockpit.
Tom C AVD
Today I wet sanded the primer coat on the deck and cleaned both the deck and the sides of the hull with alcohol in preparation for painting the deck and the sides with the real orange color coat. Like the pictures of the hull with real orange color coat, this is the first of two color coats which will be followed by two coats of crystal clear spray.
Here are a couple of pictures of the deck and sides of the hull with the first of the real orange color coats:
Tom C AVD
Made some good progress this weekend.
I built a boat cradle out of schedule 40 PVC pipe and refrigeration insulation.
I also completed spraying the hull and deck with a final coat of clear matt protective spray.
I am now at the point of applying the racing stripes to the deck. I purchased a racing stripe kit that consists of 24 ft of 6 in wide vinyl striping that has a 1/2 in stripe on either side of the main center stripe. I have prepared the surface of the servo/radio box deck access hatch by first sanding the hatch surface with 220 grit sandpaper and then finishing with 800 grit sandpaper. The surface of the hatch is now very smooth in the area that the stripe will be applied. If I am successful with the hatch cover stripe application tomorrow, I will then do the rest of the deck and the transom.
After I complete the application of the racing stripe to the deck, I will then size the prop drive shaft, attach the propeller to the drive shaft, and then bolt the prop stinger, rudder, trim tabs, and turn fin to the hull transom.
Tom C AVD
I have applied the black racing stripes to the deck and have proceeded to attach the propulsion, rudder, trim plates and turn fin to the hull transom.
I have installed the Leopard brushless motor back in its motor mount in order to size the length of the propeller drive shaft. The drive shaft is presently inserted in the motor adapter collet and the propeller and drive dog has been positioned on the stub end of the drive shaft. I have measured the distance from the front of the drive dog to the back of the prop stinger support to determine how much I need to shorten the drive shaft. I will need to subtract 1/4" from the distance between the front of the drive dog and the back of the prop stinger support to allow for the flex drive shaft rap up when it is being driven by the motor.
I will shorten the drive shaft tomorrow and then proceed to add the water jacket cooling lines, hull fittings, and install the water jacket on the brushless motor. The ESC will be mounted above the motor and only needs to have its water jacket cooling lines attached to it.
I am still waiting for the RMRC 10,000mah 6S batteries to be back in stock. I can then wire up the battery wiring harness to the ESC. I will be running two 10,000mah 6S batteries in parallel and have purchased a Hifei Capacitor Bank (http://www.offshoreelectrics.com/proddetail.php?prod=hef-h%230007) with connections for running parallel battery packs to help simplify the battery to ESC wiring.
The following pictures are what I have accomplished this week:
Tom C AVD
Between Thursday and today of this week I completed cutting the propeller drive shaft to the correct length, installed the cooling lines and fittings, installed the motor water jacket, and have attached the cooling lines to the motor water jacket and have sized the cooling lines to the ESC. I have also attached the ESC mounting fixture to the top of the motor mount, however it does not appear in this set of pictures.
I am still waiting on the batteries, but I can solder the 6mm connectors to the ESC motor cables and attach the ESC battery power cables to the Hifei Capacitor Bank for paralleling the two 6S 10,000mahr LiPo batteries.
While waiting for the batteries I will move ahead with installing the Pixhawk navigation controller and associated supporting components.
Tom C AVD
Today I finished installing the ESC and its water cooling lines. I then started on installing mounting points in the corners of the hull motor opening to support the navigation controller hatch plate and provide hard points for the hatch plate hold down locks.
I will order a Pixhawk, a GPS/Compass module, and a PPM encoder tomorrow and begin a layout of the navigation controller components on the hatch plate.
RMRC is still on back order for the 6S 10,000mahr batteries and have stated that they do not know when their supplier will deliver them. I have therefore decided to buy two 6S 5000mahr 45C batteries to be able to test the present configuration. They will probably only provide around five minutes of run time, but that will be enough time to assess the performance of the configuration.
Tom C AVD