Vac-U-Tug recovery boat build

[alanr77]

Hello, going through the many threads in the various forums I noticed that there is not much attention given to a very important aspect of our hobby; how to recover these super expensive FE boats that we build. I happen to live in a very boat friendly area- 1 block from the slip of my 30' sailboat on a tidal saltwater creek 3 miles from the open Atlantic Ocean. Perfect place to run everything from float planes, sailboats and FE boats. Having played around with RC sailboats on this creek, and while trying to dock my full size boat, the extreme tides here and the resulting 7 knot current makes a recovery vessel mandatory. It is a pain to inflate the dinghy everytime I want to use my models. Now, as a modeller, I could not bring myself to buy a cheap RTR rc boat and trust it to recover larger sailboats in this current. In addition, I am looking to build a FCR Fantasm in the near future. Given that our boats usually have at least a grand worth of expensive electronics aboard, I would hate to see my boat being carried out to sea. So, I chose to build a Vac-U-Tug- available from Vac-U-Boat.com.

Now, the stock setup that comes with the tug is a 12v low kv brushed Johnson 385. It also comes supplied with a 1/8" shaft and 3 blade plastic prop. I am sure this works fine but being a crazed modeller who can't leave well enough alone, I decided to "upgrade" the drive system. Now, I am sure this is most likely overkill but why not? So, the parts list of upgrades is as follows;

Turnigy 28mm 950kv brushless outrunner
Turnigy 30 amp water cooled esc
50mm Raboesch 4 blade brass prop
Harbor Models 3/16 prop shaft and stuffing tube
Subwerks electric waterpump
Water cooled motor mount
Various LED's to recreate deck lights
1/48 scale radar with a modified micro servo to spin it
Various scale parts- tires, fenders ect from harbor models

The plan is to have a forced water cooled setup that is turned on and off via channel 5 on my tx. The radar will be tied into this so that I can visually see that the water pump is on by looking at the radar. The lights will be controlled by channel 6. I will modify mini aaa maglight housings to operate as the two forward search lights. The tug will be modeled after a tugboat on the Savannah River named "CYNTHIA TURECAMO".

Overkill? Maybe. But it should be a fun build nontheless. 9527795278952799528095281

[alanr77]

Tug that she will be modeled after. It was the closest tug that I could find that looked similar to the Vac-U-Tug. 95282

[alanr77]

The kit includes a formed plastic stand that is molded to fit the hull.

95307

I used this build to justify buying an airbrush kit. I have never used an airbrush before so I will use the boat stand to practice painting before I paint the actual hull. I will paint the hull with Badger Modelflex marine colors Acrylic water based paint.

The entire kit has traced edges showing where to cut out the parts. The material is easily cut with normal scissors.

95308

Before paint- as always- comes the most important part, prep work. I first cleaned the plastic with a scrub pad and mild soap to remove surface contaminates. Then lightly sanded/scuffed with 130 grit sandpaper.

95309

I then primed the plastic with PlastiKote sandable primer. Three coats were needed, as per the instructions. I lightly sanded with 400 grit in between coats.

95310

I will let the primer dry for a day or so before lightly sanding with 400 and then comes my first airbrush coat. Being that I have never used an airbrush, I will play it safe and follow all the rules to a T. As in multiple mist coats until the plastic is covered. Everything I paint will be coated with a clear acrylic to protect it from scuffs.

[alanr77]

The nest step is to assemble the new prop shaft and stuffing tube. The stock setup is a 1/8" shaft with a small 3 blade plastic prop. I wanted to use a brass prop, 50mm in size. So instead of adapting the little prop shaft to the prop, I ordered a 3/16" stainless prop shaft and stuffing tube from Harbor Models. The new shaft is 22" or so long so I had to cut it down to size.


Stock prop shaft vs the new prop shaft
95311

I think the 3/16" shaft is for a MUCH bigger boat
95313

Measure and mark
95314

Dremel cuts
95315

My cuts were horrible so I had to gring the shaft and tube
95316

[alanr77]

Next I had to grind a flat spot for the motor coupler set screw
95317

Scuff the stuffing box tube so the epoxy used during installation will bond to it
95318

Deburr and polish the prop shaft
95319

New shaft ready for dry fit of coupling
95320

The included motor coupling is designed for a 1/8" shaft so I had to drill out the hole to 3/16". Instead of buying a new coupling at $22 a pop I figured there would be enough material in the coupling to just modify it. I had to build a drill jig to ensure the hole was true. Seems to have worked out well.
95321

[alanr77]

New shaft and coupling ready for assembly
95322

Good to go
95323

The instructions at this point tell me to fill the tube full of grease. However, I will install the stuffing tube before doing this to prevent and grease from getting on the tube and messing up the epoxy bond.

[alanr77]

Ok, the learning curve for using an airbrush was pretty steep. I ended up with blue paint all over myself and everything around me. But, I think I have it figured out. Airbrushes spray a much finer mist than spray cans- this lends itself to many thin coats to achieve a nice finish. I originally was going to paint the topsides blue but have decided on red instead. So, having 4oz of blue left over, I decided to paint the stand blue. Should look better when the tug is on display- black hull against the blue stand.

Coat number 4
95380

Coat 5
95381

[alanr77]

Next is to cut the outline of the outer hull. The lines come pre scribed and only require a steady hand with the scissors.

Line to cut with scissors
95386

My hands shake so....
95387

Now I have to sand the outline because I can't cut a straight line
95388

Next is to mark the stuffing tube at 3/8". This is how far the tube will stick out of the hull
95389

Step drill the rudder hole to 1/4"
95391

[alanr77]

Rudder hole drilled
95393

Sand the rudder hole to remove burrs
95394

Cut the hole for the prop stuffing tube
95395

Mark hole for first skeg screw
95396

Drill the first hole. It's really important to get this hole right. The skeg is aligned to the keel and the first hole sets the stage for the rest of the task.
95397

[alanr77]

Align the skeg to the keel and mark it for the second hole
95398

I was not happy with aligning it by eye. The alignment is important to ensure the rudder does not bind when it is attached to the bottom of the skeg. To ensure this alignment was correct, I dry fit the rudder and used it as the jig to mark the second hole for the skeg.
95399

At this point, drill the second hole and secure the skeg. Double check the rudder after securing the skeg to make sure there is no bind.
95400

While everything is attached, I dry fit the prop. The skeg will have to be notched to clear the 50mm prop. I will modify the hull to use this big prop. With a low kv outrunner and the 50mm prop this thing should be a powerhouse.
95401

[alanr77]

The next steps called for a cutout and test fit of the hull inner liner. This will most likely need to be modified to fit the water cooled motor mount but I followed the directions up to this point.

The inner liner has the pre made scribe lines as well.
95473

I am NOT good with scissors. I cut out the outline and had to sand the area to make it smooth. This will not hurt anything because I plan to fasten the liner to the hull with bi-axle cloth and epoxy. The scuffing would be needed for the epoxy to bond anyway.
95475
95474

After sanding I test fitting I cut out the hole for the prop shaft with a razor.
95476

After test fitting and ensuring everything was lined up, I scuffed the area around the stuffing tube to prepare for the cloth and epoxy.
95477

[alanr77]

To bond the stuffing tube to the hull, I first aligned it and secured it with a dab of CA glue to hold it in alignment. I then applied 5 layers of bi-axle cloth saturated in West System Epoxy. This should hold the stuffing tube in place.
95478

I always blend in a little filler to add strength to the epoxy, hence the black dots. After this dries I will fill in around the outside of the stuffing tube with thickened epoxy and fair it to the hull.

[Make-a-Wake]

Nice build.

[ray schrauwen]

Subbed.... err ahh, tugged... Nice extras you have decided on. This will be cool to watch. This build may be a good idea for me too...

[alanr77]

Thanks for the comments, I was beginning to wonder if anyone had any interest in a lowly vacUtug here on OSE. The support vessels and teams never get any credit lol.

Anyways, I applied the final coat of blue on the stand. My god, I am now an airbrush fan. The finish is perfect. No flaws, runs and very little overspray. It's a little more work being that you have to clean it each time, but the paints are water based and clean up easily. I just wait until the girl is not around and use the kitchen sink. :)

Final coat, ready for clear coat.
95504

New parts came in today. A real rubber bumper for the bow and 20 real rubber tires in two different sizes for use as fenders. If you notice on the real tug, she had bigger tires up front and smaller tires aft. Small details but they make a difference.
95505

At this time I mixed up some thickened West System and layered it over the hardened cloth. Looks like I will have some sanding to do but it will be bulletproof.
95506
95507

I also faired the outside of the stuffing tube.
95508

When everything was dry fit, I noticed I may be able to install the prop without notching the skeg. The clearance is like 1/16" so we will see. I am not sure how true this prop shaft will run so if it is any less than 1/16 I will notch it for clearance.

[alanr77]

Ok, with the epoxy around the stuffing tube dry, it was time to sand it all down both inside and out;

Sanded inside so the inner liner would fit properly
95532

I faired the outside smooth
95533

Test fit of the stock motor and tray. I will not be using this motor but I wanted to see how it fit in the hull
95534

This is the new motor and watercooled mount. The motor is a 28mm 950kv brushless outrunner- Turnigy 2836. The mount in the 28mm water cooled mount available here on OSE
95535

I doubt the stock tray will work but it is worth a try. I had to cut out the tray so the outruner would have room to spin
95536

[alanr77]

I used a Dremel to rough cut the plastic. Filled the garage with smoke
95537

Test fit of the motor mount on the cut tray
95538

I attached the mount with tape to hold it in place. The stock tray has the motor under the tray, so thats the way I would try the tray
95539
If you notice, the motor is mounted backwards in the mount. I did this for two reasons; the motor has the proper hole spacing on the back being that it is designed for an airplane. Second, the water cooled mount would have the water cooling at the bottom of the motor. Heat travels up, and the cooling fins built into the motor draw air through the front and push it out the back. So,the water cooling is now at the top of the motor and at the back.

Now I test fit the motor with the tray. I was unable to get a good alignment this way. I want the shaft to be a straight as possible, even at the slow speeds this motor will be turning, I want to reduce as much vibration as possible
95540

The end result of my stuffing tube install. I have to match this shaft angle to the motor shaft
95541

[alanr77]

Next I had to drill the motor coupling to match the 4mm motor shaft.
95542

The result of proper alignment
95543

Being that the stock motor tray will not work with the brushless motor, I decided to build a new one out of 1/4" balsa sheet. The new tray will be glassed and epoxied to the inner hull liner
95544

With the new tray cut out, I test fit the motor. I wanted to ensure the motor mount adjusting screws were in the middle of their range so that I could make small adjustments after the mount was secured to the hull. Therefore it was important to get the mounting tray as close to perfect alignment as I could.
95545

At this point the alignment looks really good. Now I have to mark the location of the tray and the location of the motor mount on the balsa sheet
95546

[alanr77]

I simply used a marker to mark the location of the parts
95547

The balsa by itself is not strong enough to handle the torque this motor will put out. So, I added cross beams going against the grain to add strength
95548

Then I added another beam of balsa to create a box
95549

Once this was dry, I rounded all the edges so that the cloth would follow the contours better
95550

The cloth was cut into strips and layered on to the bottom of the new tray. 95551

[alanr77]

I built up 3 layers of cloth. Once this has dried, I will flip it over and coat the top with clear epoxy.
95552

Now, to anyone building this boat. None of this is really needed as the kit comes very complete. If I was just building this boat, it would be done already. The stock motor and tray fit very well and the assembly is very simple. The route I decided to take pretty much changes the entire running gear of this boat. My goal is to triple the pull of the stock running gear and still have long run times. We will see.

[Make-a-Wake]

lookin good!

[alanr77]

Well I thought I was ready to start spraying the clear coat on the stand. However I have run into a small issue. The paint from the airbrush goes on so thin that whenever I start to scuff the paint with 400g, it sands right through on the corners and edges. I had to spray another coat of blue this morning. I think I will lightly scuff the main part of the stand and leave the edges alone. Hopefully this will not affect the bonding of the paint in these areas. Any suggestions from people who have used an airbrush?

[Make-a-Wake]

I wouldnt have used 400 grit, I wet sand with 1500-2000 myself then let dry in the sun, just how I do it.

[jcald2000]

I always put 2 medium coats on the corners before I do the rest of the coats, it helps.

[alanr77]

Good morning! Thanks for the tips. I am used to using painting methods that apply thicker coats so I was unprepared for what happened. I will use all the advice given. I ordered 1500 grit sandpaper and sprayed a thick coat on the edges and corners. Thanks! When the sandpaper arrives I will lightly scuff the stand and hopefully spray the first clear coat.

[alanr77]

The next step was to create a "pocket" for the motor mount side plates to sit in. Once the motor tray has been secured to the inner hull liner, and I am happy with everything regarding alignment, I will fill the pockets with epoxy and sit the motor mount into the tray.

Create a pocket for the motor mount
95637

95638

Next I built rails for the motor tray to sit on.
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The rails will be attached with screws, then epoxied in place

95641

[alanr77]

Rails double secured to the inner hull liner

95642

Test fit of the mount onto the motor tray

95643

Test fit the tray into the hull

95644

After everything is aligned the best it can be, the hole assembly was epoxied in place. Once this dries, I will remove the motor mount and using cloth and epoxy, glass the entire assembly into the hull
95645

[alanr77]

Next I cut out the cloth strips to glass in the motor tray
95646

Then using West System I wet out the cloth and attached it to the hull liner. I doubt this is going anywhere.
95647

Once this dries, I will sand it all down. Ultimately, the bilge will be painted even though it may not ever been seen. I figure the paint will seal anything that was not coated in epoxy so water will not effect the balsa tray. The nice thing about this kit is that by using a hull liner, I can build everything and attach it to the liner before securing the inner liner to the outer hull. The plans call for ballast. I am unsure if this will be needed though. I am building a battery compartment that will be able to hold 2 5000mah 2s lipos. 10,000 mah should run this thing forever even with the accessories. The sheer weight of the gear and batteries may be enough.

[Make-a-Wake]

That's one purdy flex drive!

[alanr77]

After allowing everything to dry for a few days, I dry fit the motor mount to the new tray. I had to sand about 1/8" off the bottom of the OSE mount to get it to line up with the prop shaft. After carefully measuring and sanding, I was able to get the alignment right and keep the motor mount adjustment screws in the middle. This will allow me to fine tune the adjustments later in the build.

96041

I then used 5 minute epoxy to attach the motor mount to the tray.

96042

The 1500 grit sand paper worked great. I was able to scuff the boat stand and spray the first coat of clear. Thanks for the advice.

[Make-a-Wake]

I was wondering about the cell count you would use, I was hoping i wasnt gonna read you were using 6s or something crazy. 2s and that motor will give you great runtime and good low speed torque and allow you to use a decent size prop with some bite. Glad the 1500 grit worked out.

[alanr77]

I am using 2 5000mah turnigy nanotech 2s batteries wired in parallel for 2s 10,000 mah.

[alanr77]

With the 950kv motor it should spin around 7k unloaded. The 50mm 4 blade prop is rated to 7000 rpm. Loaded speed should be in the 5-6k range at full throttle. The way this boat is set up, I shouldn't need to go past 1/2 throttle when just running around. I want the high reserve for towing operations.

[Make-a-Wake]

I retrospect a 700 brushed would probably have been better since a brushless ESC especially doesnt like tooling around at half throttle and having to manage the voltage at mid throttle. Hopefully with only 2s2p it wont be an issue with your brushless setup..............you may consider a smaller prop to be able to throttle up more.

[alanr77]

MaW: a brushed 700 would be going in the opposite direction from where I want to go. An underlying theme for this build was to update the running gear to something from this decade. I guess I forgot to list that as my intention in the first post. When researching the running gear for this boat, or any tug, all I could find were posts from people telling the builders to pull motors out of hairdryers and such. It was insinuated and sometimes flat out written that "brushed motors have no place in scale builds". Now, being just below mid life, I was around when brushed motors were all we had and at the time the only choice. However, now, we have much better technology and the days of the brushed motor are coming to an end. I can't really think of any benefit a brushed motor has over a brushless motor. I have 14 planes and 6 helicopters all running brushless setups from 2s to 6s. I rarely run any of them at full throttle other than during take off. I have never had any issues with my esc's handling this over the past 6 years. I thought about the reasoning for your caution and at first came up with the lower loading of my airplanes spinning smaller props, but I could not logically apply that theory to my helicopters, which spin large diameter blades and drive belt tails. If I am missing something here let me know. Beyond all of this, I feel that in a lot of ways older, experienced modelers are holding onto their brushed motors like people in the 80's did with VHS tapes. So instead of following the masses I'm going to show it can be done- because eventually we will run out of hairdryers to steal motors out of....:] By the way, please don't take this as a defensive backlash at your post- no harm intended, I really appreciate your input and advice, besides, I think there may be 2 people watching this and I don't want to lose my only audience.

So, being that to me these are toys that I play with when I am unable or don't feel like working on my full size toys, I like to experiment with them. When all is said and done I will have less money in this tug than it costs me to buy a gallon of bottom paint for the big boat. So if I burn up some stuff, so be it. [mind you, I will not play this game with the FE build as the electronics are going to set me back a few grand]

Having said all this, lets troubleshoot my logic when I chose the components of this build;

Stock motor specs:

Specifications:
Dimensions : Ø 27.5 X 38.0 mm
Shaft Diameter : Ø 2.305 mm
Input Voltage : 24.0 V DC
No Load Speed : 22000 rpm
No Load Current : 0.20 A
Nominal Speed : 18500 rpm
Nominal Torque : 10.00 mNm
Nominal Current : 1.20 A
Stall Torque : 60.00 mNm
Stall Current : 6.00 A
Maximum Output Power : 35.00 W
Maximum Efficiency : 70 %
Torque at Maximum Efficiency : 10.00 mNm
Speed at Maximum Efficiency : 18500 rpm
Life (typical) : 150 hr
Weight : 65 g
Operation Temperature : -10 to 55 °C

Upgraded brushless motor specs:

Spec.
Battery: 2~4 Cell /7.4~14.8V
RPM: 950kv
Max current: 23.2A
No load current: 1A
Max power: 243W
Internal resistance: 0.070 ohm
Weight: 70g (including connectors)
Diameter of shaft: 4mm
Dimensions: 28x36m
Prop size: 7.4V/12x6 14.8V/9x6
Max thrust: 850g
Storage Temperature : -20 to 80 °C
Electrical Connection : terminals

I will be running a 30 amp esc with this motor- forced water cooling on the motor mount and esc. Goal is to spin a 50 mm 4 blade prop that will push the boat to hull speed at less than 1/2 throttle. I purchased this motor after spending hours comparing the specs of countless motors. the goal was to increase the efficiency and triple the watts without increasing the rated rpm. I think I have come close to this. Do you not agree? Give me some insight to what I have missed. Thanks for the replies. Alan

[Make-a-Wake]

I hear ya loud and clear, my "insight" is that brushless ESC's dont like being powered at half throttle, they hate it and will overheat having to manage the current, ripple currents can result and then the ESC can fry, that's the only part of the setup that worries me. Keep on building!!:Peace_Sign:

[jj2003]

I'm dropping in on this one alanr77......so now you have an audience of 3...hehehe! Nice build process :)

[marko500]

Oh I think there's more then 3 watching this thread. I've been following it too. Very nice build so far. I have a Vac-U-Tow that we use for rescues, works great.

[alanr77]

Good afternoon, ok, after letting the motor mount dry overnight, the next step is to start placing the components into the hull liner. Now, the instructions only call for the rudder servo to be mounted. There are tiny dimples already in place to guide your drill bit when installing the rudder servo. I found that the hole and dimples match the mounting tabs of a Futaba S3004 standard servo perfectly and mounting it was easy. However, I am installing two additional servos and switches. The first will use channel 5 and turn on the lights. The second using channel 6 will turn on the water pump and radar dome. If you remember, I am using a micro water pump to force cool the components. The hull will not move fast enough to draw water on it's own. The radar dome will spin when the pump is on to tell me it is running. The light switch will control navigation lights, deck lights and two spotlights.

First, I marked the location of the mounting holes for the tray within the hull liner
96112

Next I drilled the holes with a hand drill
96113

I had to move the entire tray forward from the stock location because the large servo hit the motor tray. Small oversight when I designed the motor tray.
96114

I played around with the direction that the servo would face. I had to ensure that the rudder control arm would clear the motor mount
96115

Then I started placing all the components where I thought they should be. This is going to require some ingenuity
96116

[alanr77]

Lots of parts. This hull is looking small....the main receiver is going to be below decks, the satellite receiver will be on the bridge with it's antenna attached to the simulated VHF antenna
96122

I marked the location of the two micro servo's and switches. They were cut out with a Dremel and a razor blade. Not pretty but functional and will be unseen
96123

I had to offset the servo's slightly to accommodate the curve of the hull. I am not sure how all of this will fit so I want to leave myself options later
96124

After everything was cut out, I placed reinforcement strips of epoxy saturated balsa under the screw holes
96125

When screwed down you can see the offset. May not be necessary but it's better to do it now
96126

[alanr77]

After everything was secured, I dry fit the component tray again to make sure everything fit so far
96127

I had to tweak the servos a bit to clear the hull liner. There are so many pieces going into this hull that the placement of components has to be well thought out in advance.
96128

Next I drilled the holes in the switches for the rod that will connect to the two micro servo's
96134

Then I trimmed the bottom of the screws. No need to have extra sharp bits sticking out. This hull will have a mess of wires and water tubes running around so I'm trying to prevent issues later
96135

After putting it all together, I went to center the servo's and found out my old GWS servo was shot. As you can see, I am reusing many parts that I have laying around, such as screws and servo's. Luckily I have packs of micro servo's left over from other builds so I installed a towerpro micro servo in place of the GWS servo. It's a little taller but shouldn't cause an issue
96136

Also while doing this I found that my transmitter was not using channel 5 at all and channel 6 using both the right stick and switch a. Unfortunately, the cheap ExceedRC Tx I had laying around can only be programmed via laptop and programming cable. Thats enough work for today though and I will tackle that tomorrow.

[Make-a-Wake]

You gonna use the Lipo to power the pump as well?

Why 2 servo's............didnt see it if you explained.:huh:

[ray schrauwen]

Are you adding any ballast?

[alanr77]

MaW; three servos are being used. The large Futaba servo is for the rudder. The two micro servos will be used to actuate small switches controlling 1) all lights, 2) water pump and radar dome motor. The two lipos in parallel will power everything. This tug is designed to run on a 1200 mah nicad pack so 10,000 mah of lipo power should give good run times even with all systems operating. I will most likely get bored before running the battery down.

RayS; the instructions call for ballast, however, I am adding lots of weight in running gear and accessories. The ballast is supposed to be glued in between the inner and outer hull. Once I have all the components installed I will put it in the bathtub to check the water line and add ballast as needed. Then I will attach the liner to the outer hull.

[Make-a-Wake]

I think 10,000 mah is plenty of ballast lol

[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.

96235

Next I test fit the component tray with the motor attached to the mount. I found that the tray hit the lower screw
96236

So I trimmed the tray to clear the screw
96237

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
96244

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
96249

[alanr77]

The tray was cut to match the width of the ESC
96250

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
96251

I then test fit the ESC on the tray to ensure this all would work
96252

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
96253

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
96254

[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
96255

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
96256

Small drill and two measured holes allowed me to use the two mounting holes already on the pump housing. Secure
96257

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
96258

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
96333

Then cut it out and began sanding it to fit the contour of the hull liner
96334

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
96335

I then cut out the bottom portion of the bulkhead and sanded it to fit the hull liner
96336

Once it looked right, I cut a notch into the top portion for the lower bulkhead, this increases the strength of the assembly
96339

[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
96343

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
97192

The prop is half way out of the water
97193

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
97243
97244

Test fit parts
97245
97246

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.
97247

[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
97288

Dry fit of the inlet
97289

Sealed with blue RTV
97290

Installed and waiting to dry
97291

[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.

98095

I had to reposition the rudder 2mm aft

98096

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.

98097

Reinstalled. Much better now.

98098

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

98099

[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.

98100

[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
98129

Covered the ballast and sealed the rear of the hull
98130

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.
98131

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
98132

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.
98133

[alanr77]

Both servos connected with the proper amount of throw. Not fancy but adjustable and strong
98134

Next I wired the water pump to one of the switches.
98135

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.
98348

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.
98349

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.
98350

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.
98351

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.
98352

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.
98911

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.
98912

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.
98913

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.
98914

[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

[pescador]

I've had the Vac-U-Tug and built the Vac-U-Tow and have photobucket pics and a build thread if you want to message me I can give you the links. Not sure if this is the place for my stuff.

[CPDMU]

Ok PM Sent

[alanr77]

Hello CP. Sorry I took so long to respond:

Initially, the prop I had installed on the tug was to big. I've since bought 3 different props to try out, I'll have to get back to you on the sizes. The original prop i used, which is listed in the build, resulted in an incredibly powerful combination. On 2S it would try to plane, even with a couple POUNDS of ballast epoxied in the hull. Pulling power wise it would pull a raft around with a person on it. Make sure the hull, deck and superstructure is water tight if you go this route though. It's way beyond the capability of this hull. At the time, I simply limited the max throttle by programming it on the tx. We have been using it as a recovery vehicle ever since. It will pull anything in regardless of tides and current. This fall/winter, I'd like to try the other props and return the throttle to normal In order to allow the motor to run at its most efficient rpm. With the 2 5000mah 2s lipos wired in parallel, it has been used an entire weekend without running out of battery. Additionally, I had bought all the parts and paint to make it look semi scale, lights ect. But, being used as a workhorse suits a plain hull better so far. To summarize, it did exactly what I wanted it to do and continues to do it. Though in retrospect, I would imagine it could do the same thing with the supplied hardware.