Vac-U-Tug recovery boat build

[alanr77]

Ok, today I spent a few hours programming my ExceedRC 6 channel TX so that the two micro servo's would operate with the two top switches on the TX, channel 5 and 6. I had bought a program called DigitalRadio that allows easy programming of the Exceed, Hobbyking, FlySky Chinese radios. It works much better than the cheap T6 config program that is available for these TX's. Can't say enough about the program. It works really well and is available at http://www.sgr.info/usbradio/default.htm for a few dollars. While I was at it, I decided to fix a loose switch at the top of the radio. The nut had simply come loose.

radiorepair1.jpg

Next I test fit the component tray with the motor attached to the mount. I found that the tray hit the lower screw
mountscrewhit2.jpg

So I trimmed the tray to clear the screw
trimtray3.jpg

Next I had to build a tray for the ESC to attach to. I decided to place the ESC right behind the motor for shorter wire runs
buildesctray4.jpg

I used 1/4" balsa sheet. The tray had to be placed carefully to clear the motor mount. I also wanted the tray to be a structural member by securing to the motor mount
buildesctray5.jpg

[alanr77]

The tray was cut to match the width of the ESC
testfitesctotray6.jpg

To accomplish this, I cut notches into the tray to fit on the motor mount. Once everything is installed I will put a few drops flexible sealant in the notches to secure them but still allow for some flex to reduce vibration
notchedesctray7.jpg

I then test fit the ESC on the tray to ensure this all would work
testfitesc8.jpg

All the wire are going to be hidden under the component tray so I drilled holes in the ESC tray for the 3 motor and 2 battery wires
eschiddenwire9.jpg

Wires hidden and ESC attached. Everything looks good. I have not secured the ESC to the tray yet so that I can still move it to solder the wires but the friction of the wires in the wood does not allow it to move for now
eschidden10.jpg

[alanr77]

Next I tried to find a place to mount the water pump for the cooling system. I wanted to mount it in the bow but I needed to leave room for double stacked 2s batteries. First I tried to make a small bracket to hold the pump but no matter how I positioned it the bracket was to wide
mockpumpmount11.jpg

Eventually after trial and error I decided to mount it in front of the ESC on the plastic component tray. There was a small patch of unused real estate that was perfect. Amazing how the obvious sometimes eludes us
waterpmpmarkholes12.jpg

Small drill and two measured holes allowed me to use the two mounting holes already on the pump housing. Secure
mountedwaterpmp13.jpg

This area was perfect because the deck housing allows plenty of vertical clearance here. And as a bonus, the access hatch will be right on top of the component tray so everything will be easily accessible once the deck is on
verticleclearpump14.jpg

The deck won't be attached for a while though because once I am happy with the layout of everything, I will remove all the componets and make it all pretty....I mean seal everything with paint.

[alanr77]

Today I decided that I would place the receiver in the bow of the hull liner. I made this decision because it would keep the RX away from all the other electronics and hopefully avoid interference. In addition, when using a satellite receiver it helps to keep the antenna's 90 degrees from each other.

I traced the outline of the hull liner on to a piece of 1/4" balsa sheet
bulkheadfor rx1.jpg

Then cut it out and began sanding it to fit the contour of the hull liner
cutouttop2.jpg

I test fit the upper bulkhead and continued to sand it until it was a close as possible. I will fill the gaps with epoxy so it does not have to be perfect
testfittop3.jpg

I then cut out the bottom portion of the bulkhead and sanded it to fit the hull liner
lowerbh4.jpg

Once it looked right, I cut a notch into the top portion for the lower bulkhead, this increases the strength of the assembly
cutnotch5.jpg

[alanr77]

Once everything was aligned correctly, I epoxied the assembly into the hull liner. While doing this, I coated all the balsa with epoxy to seal it
epoxyassembly6.jpg

This assembly should keep the balloon wrapped receiver out of the bilge and provide strength in the forward portion of the bow. The antenna will be glued along the starboard side keeping it 90 degrees from the satellite receivers antenna. The servo wires will run down the port side. Eventually when I assemble the hull liner to the outer hull, the seams of this bulkhead will be glassed to the outer hull, making a solid, 1 piece assembly.

[alanr77]

Hello, it's been a minute since I did any work. I have too many other projects going on right now. However, I did test float the hull to see if I will need ballast. I am waiting on the second 5000 mah battery to come in so in order to do this I had to cut a piece of metal out that would weigh as much as a second battery and the top portion of the hull.

Obviously even with all this gear I will still need quite a bit of ballast
20130415_123624.jpg

The prop is half way out of the water
20130415_123612.jpg

So, now I am waiting on a box of BB's in addition to the second battery.

[alanr77]

The next step is to install the cooling water inlet. I had to find a location that would not interfere with the boat stand and not get in the way of the internal components.I also had to factor in making sure it was always submerged. Displacement hulls, when moving at a good clip, create a "hole" in the water amidships as they move, so hopefully the inlet is far enough aft to prevent it being exposed when the boat is moving.

Marked location
2parts1.jpg
drillhole2.jpg

Test fit parts
testfit3.jpg
testfit4.jpg

Next I applied a thin layer of blue silicon to seal it, scuffed the hull and installed the inlet. This inlet is designed for a much larger FE boat so it looks kind of out of place on this little tug. It should work well though.
installed5.jpg

[alanr77]

The next step is to install the water cooling outlet. The only place left is across from the inlet that I installed yesterday.

Hole drilled
holedrilled1.jpg

Dry fit of the inlet
dryfit2.jpg

Sealed with blue RTV
installed3.jpg

Installed and waiting to dry
finished4.jpg

[alanr77]

FINALLY!!! I have a ship date for the second battery. Guess they had to make the damn thing or something. Moving forward.

I installed the prop and rudder skeg and realized that there was not enough clearance with the big prop.

notenoughclear1.jpg

I had to reposition the rudder 2mm aft

removerudder2.jpg

I did this by moving the lower hole aft on the skeg. It actually lined up better this way with no binding through the full range of motion.
I also had to grind the skeg a bit to allow better clearance for the blades.

trimnewhole3.jpg

Reinstalled. Much better now.

clear4.jpg

In order to fit the two batteries on top of each other, I had to raise the entire servo tray 3mm.

raisetray5.jpg

[alanr77]

After the skeg was reinstalled, I lined up the rudder arm and attached it with two set screws and epoxy. I do not plan to cut an access hole in the deck so I want this thing to stay attached. This tug naturally sits low in the water. I want to keep the deck as water tight as possible. The only access hatch will be the bridge deck, high enough so no running water ever comes close. If I ever have issues with the rudder arm, I will cut a hole, make repairs and then re seal it.

attacharm6.jpg

[alanr77]

The next step is to glass in the hull liner. Now that the ballast is in the correct place, I have no reason not to make everything permanent. By glassing in the liner over all the seals, I can sand everything and apply some cheap spray paint to make the interior look "finished". This also creates an air pocket along the entire lower half of the hull and in the bow area to hopefully add some positive flotation. I doubt there will be enough room for any other flotation so if it takes on water, hopefully this will slow things down a bit.

3oz cloth and west system along all the seams
glassedinliner1.jpg

Covered the ballast and sealed the rear of the hull
glassedinliner2.jpg

Next I had to wire the motor to ensure it was spinning the correct way. The throttle channel had to be reversed and the wires switched around to accomplish this. Man does this motor spin slow....950kv is the lowest I have ever used.
wiredmotor3.jpg

Next I wired the switches for the water pump and lights. I had to create y harness' to tap a + and - off the battery leads
wiredswitches4.jpg

Next I setup the switch linkage. Nothing fancy but secure. My radio is a cheap 6 channel Exceed TX that requires a laptop to program; so I had to keep taking it to my desk to adjust the servo end points so that the servos would not bind. I ended up with 50% throw on both servos when activating them.
setupswitches5.jpg

[alanr77]

Both servos connected with the proper amount of throw. Not fancy but adjustable and strong
setupswitches6.jpg

Next I wired the water pump to one of the switches.
wiredpump7.jpg

After doing this I realized that I forgot to run two leads off the water pump motor to power the radar arch. Later I will remove the leads from the motor and splice in two power leads.

[alanr77]

OK, everything was hooked up and adjusted and...under pressure from friends, I plugged in both batteries and did a power test in the bathtub. The water pump works great. It provides a steady, low pressure stream to all the components without creating a water jet that pushes the stern around. I did notice that when on, the pump motor created enough interference to cause the switch servos to twitch badly. After staring at it for a while, I decided to try the quad capacitor setup off of an old motor from one of my helicopters. Worked like a champion. Apparently the cheap 380 motor attached to the pump runs very dirty...what do you expect from Chinese engineering. At the power level this tug will run, I doubt the pump was even necessary but why not?

Now, speaking of power, with this huge prop the boat looks like it will achieve hull speed at a very low RPM. Just off idle to be exact. That was the goal. This thing will run all day with the motor spinning slow enough that you can almost read the writing on the outer can. As I increase the throttle, the bathtub turned into a white water whirlpool. I believe this thing will be able to pull a 10' dinghy around...:) Once completed, I will attach a fish scale to the dock and test it's pull compared to stock specs. I ran it at "hull speed" power for about an hour and no component got even remotely warm. Another thing I noticed is that this thing is heavy! Should have quite a presence in the water for it's size.

I roughed up the interior hull after glassing everything and sprayed cheap spray paint in it to seal everything. You can see that the receiver is mounted to the hull on a platform I built to keep it away from electronics and up off the bilge floor.
forward1.jpg

Amidships. After all cooling lines were ran. The bundle of wires is for the lights and radar arch that will be mounted in the deck and bridge after the hull is attached to the deck.
amidships2.jpg

Aft shot. After lining up the prop shaft, I used red loctite on all the set screws and the prop nut. Zero vibration so I guess that turned out right. Notice the black RTV on the water inlet tube. The clamps I had bought were to small for the fitting so I smothered it with RTV and used a zip tie on the fitting below the barb. Also the screws are not holding the servo tray in yet. I have since put a bed of epoxy under the tray an attached the screws to make it permanent.
amidships3.jpg

Quad capacitor's attached. The setup, from an Esky HoneyBee FP 380, has four capacitors. One side to the can, then to the - lead, then bridged to the + lead, then to the other side of the can. Worked perfectly.
capaciter4.jpg

Next I attached the "towing loop". Which is actually a small shackle from leftover from the full size boat. I used a wood backing plate that takes up the entire inside of the aft deck. Shouldn't pull out. Saturated in epoxy. I have a 1/48th scale drum winch that will mount to the deck but will not be load bearing. The tow line will run around the winch, however, when using the boat for recovery, I will unwind the tow cable, loop it into the shackle to take the load and then attach the "grappling hook bobber" and tow it to the broken down boat.
towing bridle5.jpg

I am running out of reasons to not attach the deck but I want to make sure everything is in order before doing so because once attached, anything aft of the motor will not be accessible. Can anyone think of anything I might be forgetting before I do this?

[alanr77]

Ok, deck attached. I used the recommended sealant, Loctite roofing sealant S30. It required a week to fully cure. The stuff is like hardened tar so it should be water tight.
deckattached1.jpg

I epoxied really strong magnets to the top of the cabin to hold the bridge deck on. This is where I will have access to the batteries and other components.
magnets2.jpg

The satellite receiver and junction box for the lights were mounted in the bridge. I cut small pieces of metal and epoxied them to the bridge deck to attach to the magnets. I am testing the weatherstrip to see if it keeps water out. May have to go to actual rubber.
satellite3.jpg

The boat is now ready for her maiden voyage this weekend. I temporarily taped up the holes for the deck lights for this test. Hopefully all is well and I can move on to the cosmetics- detailing and paint. The power test will be recovering 1 meter sailboats in high winds. If she can tow them, any FE hull should be easy.
ready4.jpg

[CPDMU]

Nice Build,,, Been 2 years since your post about being ready for the maiden voyage.


How did the maiden go? Pictures videos?

I ask because I am in the process of building one now.


Thanks
Ed