trawler line plans

Discussion in 'Boat Design' started by kcxd, Feb 16, 2016.

  1. kcxd
    Joined: Feb 2016
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    kcxd Junior Member

    Hi, Everyone,

    I am new to this forum, I amnot sure my request is legal here on this forum, I am not a designer nor a boater.

    my eight year old is obssessed with RC boat, partically on trawlers. He asked me build one instead buy him a toy. That's certainly not an easy task for a dad whom got limited engineering background.

    I have 3 years experience in wind turbine R & D, I can read 2D drawings and turn into 3Ds in solidworks, basic knowledge in machining, composite material, painting, besides, there's a backup professional, his uncle is a real mechanical
    engineer in automobile/pneumatic/electrical. my intention of this tutoring isn't focused on to please the kido with RC toy but to enlightening him in serious engineering world. It's for real. build from model ship kit isn't an option.the whole thing is about to give him ideas about basic physics, in resistance/thrust, speed, torque, rpm, efficiency, tooling, machining, craftmanship, structure, transimission, water tight, balance of system, cooling, RC communication. FPV etc. It's going to be a long term project.

    First thing first. I have practiced some hull making in solidworks from 2D line plan of a tug boat download from a model plan, without detailed dimension, it turns out to be wrinkled hull surface. I can smooth it out but rather than leave it, it's not a trawler anyway.

    I am looking for real trawler line plans, hopefully not patented. preferably, L 20m+, B 7m+, Depth molded 4m+, with bulbous bow, center lined propulsion with single propeller and nozzle. I don't need full set of drawings, not plan to make a real boat but enough contour to smooth out the hull, to suit with 1:20 scale model hydrodynamics. drawings on wheel house and deck equipment also welcome.


  2. gonzo
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    gonzo Senior Member

    If you have engineering background, it will be obvious that objects don't scale up and down linearly. An RC boat is a very different design than an actual trawler. Do you want a design for an RC boat?
  3. nzboy
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    nzboy Senior Member

  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I can't see why a full-size trawler design can't be directly scaled down to become a perfect RC model, but obviously some close attention would have to be paid to the motor and propellor chosen, as it will be a slow little thing that won't go faster than a couple of knots.
  5. TANSL
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    TANSL Senior Member

    kcxd, if you find interesting this boat , I can send you information about it.

    Attached Files:

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    FAST FRED Senior Member

    "as it will be a slow little thing that won't go faster than a couple of knots."

    Actually the usual motor installed is an off the shelf model boat unit , strong enough to plane most scale models at full throttle.
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    You won't plane a scaled-down trawler.
  8. gonzo
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    gonzo Senior Member

    There are more posts in the forum than I can shake a stick at, telling how boats don't scale up. Several members have asked if they can get a design they want and build it at twice the size. The consensus is that it won't be possible. What is the reason that scaling to 1/20 works?
  9. PAR
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    PAR Yacht Designer/Builder

    Mechanical similitude is pretty unforgiving and basic physics, so unavoidable. In a nutshell, let's say you want to make a model 50% of the original as a direct, proportional reduction. The surface area decreases 4 times not 1/2, the volume is reduced 8 times, not 1/2 and the butt kicker - stability is reduced 16 times (again, not half).

    This is why model sail yachts have fin keels that rival the height of the mast, dangling below them and the same issues will be true of a RC model, done to an actual 50' yachts (as an example) lines. This is also why small boats have considerably more beam/length ratio than larger yachts.
  10. kcxd
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    kcxd Junior Member

    Hi, Everyone, Thanks for the reply and advices.

    It’s the duty of fathers to play with boys for their dreamed toy, and we fathers do it seriously in professional way, don’t we? It also in the memory of my late dad, I still remember that he use simple file and sand paper made me a J-6(Chinese version of Mig-19) from wood log and chips. Back in 70s. there was no nothing but poverty all over the country. So now, it’s my turn to do this to my sons.

    I have very little engineering background, although I have involved with engineering projects. I do take drawings from clients, find them proper suppliers. Once, in 3 years, works with senior engineers, retired rocket designers on R & D wind turbine project. One of my duties is to turn their 2Ds into 3Ds to double check if there are interferences between the parts. I was amazed by their memories in 80s, generator is a complex machine, their calculation never failed in 3Ds. How they perform blades aerodynamic design is to use electric calculators. OK, the conclusion of my engineering background, I don’t have any but I know out sourcing.

    Here’s my preliminary plans in steps to fulfill the mission of to please sons and enlightening them with real world knowledge.

    Type of RC model
    I haven’t been bought the 8 yr old any boat toy because of safety concerns, when the propeller runs in the air, it’s cut like hell. Until now, 8 yr old is big enough to aware the potential danger.

    the reason for me to choose a trawler instead of military vessels, not only because my eight year old obsessed with it, but for the sake of sea-worthy. in a nearby park, there are RC players gathering around the pond in most calm days. It's been tradition to bring the boy on the scene for couple of hours watching the show. With the 8 yr old sending to boarding school, this activity goes to the 2 yr old boy now. Over the years, I see enough wreckage in the pond, some, are really funny. It goes capsized right away first time in water. No wind, no wave, no propeller running, just go sank. especially the old soviet gunship model, in real vessel, naval architect tries every way to prevent top heavy, they use steel hull, massive engine, ballast, aluminum bridge, to accommodate the massive weight of radar, rocket launcher, torpedo launcher, guns…RC players wanted the shape, its cool looking, they grab anything metal that can make the shape of those things. Model making is different, but basic physics cannot be ignored.

    Speed power boat also out of concern, although it’s more structural and light weight challenge out of the competition, it’s no toy in the first place. A 8 yr old isn’t big enough to control something travels 50km/h.

    Another reason, boys likes to fishing with me and his uncle. A trawler model may not able to catch fish by net but may able to tackle fishing lines in a lake, a one meter long boat is big enough to handle most size of fish and small enough to fit in the trunk of my Jeep. At least, it can go into the middle of a reservoir to leave baits for conventional angling. For this purpose, as a RC boat, at mean time, a work boat, it requires serious planning before unforeseen wreckage happens.

    Hull construction
    buying a kits is out of concern, we don’t want to miss the fun of building from scratch, although it may cost more time and money. The scale down to 1/20 is about a meter, the trawler hull shape is sea-worthy, fat, short, big enough to accommodate RC gears.
    Already showed to Larry and his uncle, we all like the shape of the hull, the point is, where can I get the contour, drawings, line plans. Still able to figure out the shape, but won’t be able to accurate enough. I see this type of fishing boat is all over the places, wish it’s not patent protected. Line plans is the key to scale down a perfect RC boat that’s the boys desired.
    Once the hull construction completed in solidworks, I can start on U-sections and the keel. All RC gears will be fitted into it through 3D planning.
    Since the boat need to be a work boat type in providing some bollard pull power, structural integrity is concerned. Big motor will be hard flanged onto the keel, the keel strengthened will be well distributed throughout the hull and the towing hook, like what we did on our wind turbine blades.
    Keel/centerlined section will be aluminum, U-section will be plywood, laser cutting based on dwg file, with stringers in place, the frame would be strong enough without play.
    hull construction will be planking on the frame, sanded and reinforced with fiber-glass and resin, filler and sanding, painting. Few layers of fiber glass reinforcement, as a small boat, I believe it will be robust enough to prevent possible structural damage with light collision and grounding.
    Below sheltered deck, there will be a water-tight-deck screwed onto the frame with ring of seals, sets of male/female plug sit on the water-tight-deck to receive wheel house deck.
    Bulbous bow desired because I wanted to give the boat more maneuverability by adding an industrial electromagnetic valve, place a small pump inside the internal water tight chamber, suck water from the bottom hole, internal circulation for the motor cooling pipes, external water jet from the pump provide bow thruster, 2 channel valve controls the direction from separate tubes.
    how to make it work, will ask my brother to do it. As a pneumatic engineer, should not be a big issue.
    it has a bulbous bow but overall dimension isn’t match. It’s longer, shallower in depth molded, and narrower in width molded, in another word, it’s more like a real world vessel, not cute enough compare to 20m*7m*4m trawler boat outlooks.

    One more concern, I spent lot of time on solidworks, that’s only software I am using. I knowit isn’t friendly in vessel designs, still, I am making a RC model, it’s not worthy to spend extra time and money on other software.

    Scale down to 1/20
    It’s a RC boat, accurate scale real boat line plans makes it aesthetic. without high & low spots on the frame, furthermore, a real boat drawings developed from professional hands, configured positive dynamic pressure to have draft decreases with increasing speed.
    I have to admit, it’s all about cosmetic thing in RC boat. Anything water tight would float, with motor big enough, it will counter any shape that drag provided, even a box shape will move.
    For sea-keeping purpose, I believe the fat round chin hull would stable enough in a lake, with planed bottom heavy, well balanced ballast, it will work like a tumbler toy.
    I understand the linear relationship when scale a real world trawler down to a RC boat, but really don’t see anything critical matters. Structure, weight, displacement, drag, speed, sea-keeping, they may not linear match the real boat efficiency but there will be formulas to do the calculation, test, modification, or just go compromise.

    Power train and propeller
    assume 200t displacement in real boat, 480kW engine, the ratio would be 2.4kW per ton, in scaled boat, if this is linear relationship, it should be 2.4watt per kilo. Assume the 1/20 model displacement is 10kg. that will be a 12V DC 24watt motor, in mind of power reduction through power train, motor attenuation over time, larger motor considered, normally they are small torque with high RPM, 1:3 reduction gear coupling to the propshaft applied, mechanical reduction provide torque, ESC electric speed controller provide RPM control, it can be done on ESC alone but would stress out cause malfunction.
    For such motor, an electric bike battery with 5-10aH capacity would drive the model for hours. It also provide the function of ballast balance to the boat.
    Propshaft already limited under 1500-2000rpm by reduction gear, with industrial lathe machine in our workshop, it’s easy to fit bearings and seals to built a model sized propshaft to take the heavy load.
    Propeller, plan to 1/20 miniature out of real boat propeller if I can get the drawings. However, our 3D CNC would not be good at all the curves, some craftsmanship welding required on a fixture, least of all, static balancing required for sanding & filing. Nevertheless, it’s a RC boat with low RPM load. With the fat shape of the hull in mind, resistance will increase with speed up, no matter how big the power train provided, it stays under 10knot I guess. In this matter, I think the torque of the shaft is more important than rpm.

    Wheel house and deck equipment
    I am not very keen on that, but cosmetic thing also important for a model, as long as I can build it in 3Ds, I can find a way to machine them out, maybe 3D print is the solution for small tiny things.

    RC control
    Balance of the system with RC controls, electric circuits, water tight will be further investigate.
    8-12 channel 2.4G package should be well enough,
    on/off, secured with on board switch,
    throttle up/down, forward and reverse,
    rudder left/right
    bow thruster left/right
    will upgrade the FPV /speaker/video recording function when the platform is stable.

  11. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    It is a scale model, for gawd's sake, it isn't going to be used on the open sea like the full-scale version. I don't see a problem. But it certainly will be constrained to travel at a sedate pace.
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