LouisMiller

Hi all, just start by saying that I am completely new to the world of RC boats, in fact I have only started my search for information this evening before stumbling across this forum.

Basically I am looking for information on the basic components required to make an RC boat, I'm hoping to build a catamaran style boat with twin jet pumps for propulsion.

So, sorry this is no doubt a slightly silly question but any infomation at all would be excellent, as I am quite in the dark at the moment as to what is required aside from some form of propulsion, motors and batteries!


Kind Regards,
Louis Miller.

pompebled

Hi Louis,

Welcome to this forum!

If the catamaran is going to function as a baitboat and speed isn't important, go for the twin waterjets.

If you want it to run like the real thing (fast!), I'd go for surface piercing props, like the 1:1 cats.

Do you want to build the hull from scratch, of fit out a commercially available hull?

Look here for inspiration: http://www.mhz-powerboats.com/en/agb-2/ and here: http://www.swissmodelpowerboatteam.ch/

There are a number of plans you can download for free, not being into cats (at the moment) I can't help you there.
I know the Dutch company RCB is working on a pre-cut kit for a cat designed by Jurriaan, I could contact him and ask about the status of that project if you want, just let me know.

Not knowing your building skills, a catamaran would not be my choice as a first scratch build, way too much opportunities to mess it up.
Build a monohull first, set it up properly and use that experience to build a cat next.

Regards, Jan.

LouisMiller

Hey there, thanks for the reply.

It is indeed going to be used as a baitboat, as you say speed isn't too important but I'll definately be looking into the most powerful jets I can get away with. All in due course though, got a lot of learning to do first though. [8D]

At the moment I'm uncertain on the hull, my original idea was to design one using CAD myself and look for a local engineering company to knock one together for me; however I'm unsure of the cost of this at the moment and if it turns out to be a bit too much for my budget then I will either take on the task of constructing one myself or finding a suitable existing hull I could modify for my needs.

The kind of style I'm aiming towards at the moment is similar to this: [link=http://www.anglingtechnics.co.uk/microcat.php]This[/link].

I think I am definately jumping in at the deep-end here with this build; I was looking to start this as a bit of a summer project, starting in a month or two so maybe starting a bit smaller may be a better idea.

Would you happen to know of any links with information on the technical aspects of RC boats? Such as the electronics required to control speed; the twin jets being able to run independantly of each other for steering etc.


Regards,
Louis.

cheesewizz69

In general you will need;

1 or 2 ESC's (electronic speed controler) rated for the batteries and motors
A 3 Channel Receiver at least, Steering - Throttle - Aux (bait drop)
Transmitter
Servos
Batteries
Charger

Here is a good place to start looking for radio kits
http://www.towerhobbies.com/

pompebled

quote]ORIGINAL: LouisMiller
It is indeed going to be used as a baitboat, as you say speed isn't too important but I'll definately be looking into the most powerful jets I can get away with. All in due course though, got a lot of learning to do first though. [8D]
Regards,
Louis.
[/quote]

Kehrer sells the most powerfull jets: http://www.jet-drive.de/cms/componen...art/Itemid,17/

I think, two of these may be a tad overkill, as far as speed and available power goes, not to mention the dissapointingly short runtimes...(at full throttle)
The wisest course of action would be to call or mail Kehrer, explain what you intend to build and ask for their advice, I'm sure they can provide you with a set-up for a baitboat with similar runtimes and speed as the one in the link.

Regards, Jan.

LouisMiller

Another couple of probably silly questions incoming, I'm getting there slowly... honest.

I'll work through this in a linear fashion from the transmitter to the eventual outputs.



So the number of channels on the receiver is defined by how many different things you wantthe boat to do?
I.e - 2 Jets, 2 bait dropping mechanisms and lights would require a 5-channel Transmitter and receiver?


Having a few problems with servo's, more getting my head around how exactly they work.
So servo's are connected to each of the receiver's channels, now what exactly are servo's capable of? Can they themselves control things such as motor speed and turning lights on/off and activating the two bait droppers; or for each of these are extra controllers needed, that the servo simply activates?

Lastly, I've been looking at various jets; now once I have figured out all the componentry and thus the approximate weight of the end result is there some sort of guidelines for propulsion power to weight ratio?


That's all for now, look forward to any replies, you guys are being a great help, extremely grateful for it. [8D]

LouisMiller

Ah thanks, that's answered my last question of my last post; all I'm looking for really is around 10mph tops, just wondering how much power it would take to propel something of X weight at X speed. Once I get a bit further down the rather slow development process I'm taking I shall get in contact with them.

cheesewizz69

Yes number of channels needed is defined by how many things you wish to control. No not all the channels are for servo's. First how will you steer the boat? Will you use a rudder or use the thurst from each motor individualy to control direction? If the later is the case I a bit out of my safety zone.

If your going to stear the boat using a conventional rudder system then one channel will be used for the steering. Ok thats channel one.
If your going to use one ESC for both motors then it needs one channel. Ok thats channel two. (As you see this is not a servo)
Bait drops. You can use one servo for both. Just build a cam as the servo horn and it can activate both drops. OK thats channel three.
I'm sure there is more than one way to control lights. But again you can build a cam to activate a switch or swithces as needed. Ok thats channel four.

Depending the application you can purchase or modify a servo for just about anything you can think of. They come in various sizes and strength.

LouisMiller

Ah I see, originally I was under the impression (from my own blind assumption) that a servo was required on each channel and then an extra controller if required attatched to that. This makes a bit more sense now. [8D]

Im looking to handle steering by having independant control over each jet's power; so to turn left, full power to the right jet and vice versa. So for this I should have each motor on its own channel with an ESC?

I think I can visualise how the one servo for the bait droppers would work; I'm guessing I'd be able to set it up so flip a switch one way and it opens one dropper, flip the switch the other way and the servo changes direction to open the other one.

Well that's it simplified a bit more, given that I'll be able to open both droppers with the one servo; I think I may even be getting a basic understanding of all these electronics.

LouisMiller

I have been looking at various components and thought I'd run it by you fine folk for some input.

First, for the jets I was thinking [link=http://www.cornwallmodelboats.co.uk/acatalog/graupner_2344.html]These.[/link]

Next, onto the motors, one of the things I'm a bit in the dark over but I think I'm along the right lines with [link=http://www.cornwallmodelboats.co.uk/acatalog/graupner_3301.html]These.[/link]

For the ESC's I've come across a Dual ESC and Mixer Module for a very reasonable price, would be interested to see what you guys think of [link=http://www.action-electronics.co.uk/pdfs/P94.pdf]This.[/link]

Finally, I had a quick look around for Transmitters and found [link=http://www.fusionhobbies.com/HF49-40-Hitec-Zebra-4-Channel-40Mhz-Radio-p/hf49-40.htm]This.[/link] Going on what has been mentioned so far would this be sufficient?


Thanks again guys.

pompebled

Hi Louis,

Given the choice, I'd go for the Kehrer (better build) over the Graupner Jets (easier available).

The Action package is intended for conventional underwater props, as it has reverse, which is rather useles in a jet application; reverse for a jet is lowering a bucket behind the nozzle while the motor keeps running in the same direction.
For a jet, a forward only ESC is all you need, along with a servo for each jet to lower the reverse bucket.

As you want to use two jets, having a mixerfunction on the transmitter would be nice, allowing you to controll both jets with a single stick, the transmitter can be programmed in such a way that when you pull the stick down to reverse, the motor will stop at the neutral point and run in the same direction when reversing, while the bucket is being lowered.
If you find this sounding complex; it is, getting this kind of programming right is tricky, I know I can't do it, but there are programming wizzards that could assist.

The 'simple' way would be to have each jet on a seperate stick (tank steering), but you'd still have to have the possibility to lower the reversing buckets individually, to be able to turn on the spot.

I'm not sure the four channels of the transmitter you linked to, will suffice. I gues not, as there's no mention of programming it.

Regards, Jan.

LouisMiller

I have been reconsidering what I will be using for propulsion, as far as I understand the jets will have a much higher battery drain than standard props and to be honest I have no real reason to avoid props, I could simply incorporate some kind of cage around them to protect from getting caught on weed and the like.

Also considerably cheaper aswell, which is a good thing.


As for the motors, do you think the 600's I found will suffice? Or would they even be an overkill and 400's would be better instead? Although I have noticed motors are fairly inexpensive so if I find 600's to be a bit too much I can always swap them for 400's at a later date.


The transmitter/receiver aspect is still something I'm a little bit fuzzy on, mainly how you program it to do what you want. I think I'm going to have to find a local model shop and have a look at some to get a better idea, I know I need 4 channels but on various makes of transmitter I assume there are always various controls linked to the channels, if I'm along the right lines here then I think I should be looking for a stick controller with a switch for activating lights and a two way switch for operating the droppers.


On a very good note I may have found someone to build me a hull once I have designed it! Turns out my partner's uncle is in that industry and owns his own company so should be no problem! That was a very welcome surprise as the hull build is the only thing concerning me at the moment.

On the hull design front I have been playing around with different shapes and came up with my first draft of the main part of the hull, once that is tweaked enough then I'll be able to plan out the top part of the hull. I'll stick a drawing up shortly of my first design.

LouisMiller

Here we go, this is the kind of thing I've got in mind; not set in stone yet though so feel free to chuck criticsm my way.

At the moment it is approx 600mm long, 400mm wide and 125mm high. With the top section aswell I estimate it to be about 200mm high.

pompebled

Hi Louis,

If you go for two motors with props, the Action ESC is perfect for your application.

You can go even cheaper with two motors, each with a forward/reverse ESC and use the transmitter you linked to before; left stick controls one motor forward and reverse, right stick controls the other motor forward and reverse, of the two remaining channels, one can be used to operate a servo to open the bait containers the other is free to switch on/off the lights, or whatever gadget you want to control.
No programming whatsoever (exept in your mind).

The design could be more hydrodynamic, the two pointy boxes with a blunt end create a lot of drag, costing power, speed and runtime.
Consider longer sleeker hulls (like a sailing catamaran), you'll have the same payload, but more speed with smaller motors and ample runtime.
Something like this: http://www.fliegernils.de.tl/Solarboot.htm
This one has the disadvantage of having to work with solarcells (design contest), but the hull itself is very quick with some decent motors and props.

Motors: stay away from the amphungry Speed series, for torque and runtime see if you can get your hands on some Bühler motors like these:
http://www.hobby-lobby-modellbau.com...0-12-Volt.html
Check out the average Ampdraw (Durchschnittlicher Strom ca. 1,0 A) and compare that to the Speedmotors; they won't even turn over on 1A.

With a sleek design, the cat will be plenty fast with two of these and they will push 20 Kg of boat together.

Regards, Jan.

martno1fan

Louis theres a guy sells some nice glass hulls on ebay UK theyre called dell quay dorys they make exellent bait boats im thinking of doing a cpl myself for my old man whos a carp fisherman and another for me lol.Theyre 33" long 13 "wide very stable boats and ideal to convert .He has none listed right now but heres a pic of them he lists them very regular he had ten available on sunday so must have sold em all [X(].oh yea theyre only 36 quid

LouisMiller

Thank you very much for the advice, I've just made a new design which I think is much better. Pretty sure I've made it as hydronamic as possible while still leaving room for the batteries, motors etc. Once I've made a final decision on components I may be able to make the hulls a little smaller, at the moment they are each 100mm wide, pretty sure I might able to take that down a bit.

Will post design in a second, on the laptop I work on I can't change the drawing created from the CAD program into JPEG.

Thanks for the link to that motor, once again that's something I have no idea about so much appreciated. [8D]

For prop size I was thinking 50mm, and for that I've made the recess at the back end of the boat 65mm deep, I think it should fit snugly under there with some kind of guard around it.

LouisMiller

Here she is; as I said I can't think of anything else to change to make it more hydrodynamic and still have enough room for everything but I'll leave that for all of you to judge!

pompebled

Hi Louis,

The butt ends still cause massive drag.
If you cut the hull off where the blunt end starts and glue another one just like that onto it, you'll have a much more fluid form with low drag.

Granted, the props would have to stick out from under the hulls, in weedy waters that may prove to be a problem, to say the least.

You may want to alter the rear end so it formes half a tunnel around the props, that would shield is from the sides and you'll still have a decent hydrodynamic design, some mesh below the props might keep the weeds from them clogging up.

If you need a (crude) sketch, let me know.

Regards, Jan.

LouisMiller

I think I know what you mean; with the cut away section I was planning on fitting some mesh around that part once the props are fitted, forming a cage for them to keep them clear of snags.

Pardon my very bad drawing (and writing - was rushing a bit) but I think this is along the right lines, not having a blunt end:

pompebled

Hi Louis,

Correct!

If you let the section under water end like the top section, you'll have a sleek hull that has very little drag and will be quick with very little power.

Provided I find the time, I'll make a drawing of the tunnel idea.

Regards, Jan.

LouisMiller

Excellent! Thanks a lot.

I have just finished yet another design, I haven't incorporated a tunnel into it for the props yet but I have a very good foundation for it. I think I may be getting close to a finished model!


Will post drawings in a few minutes. once I've sorted them out.

LouisMiller

Right then, the latest design!

pompebled

Hi Louis,

The way it's drawn now, allows no waterflow to the props, I've added a sketch of how I think it could look.
The proptunnel is open at the bottom to allow waterflow to the prop.

Regards, Jan.

LouisMiller

Very good idea, is there anything else you think could be changed about the boat on top of that?

Looking to try and get a final design sometime soon so I can go about gettign a wooden model knocked up in order to create the hull mould.

The final thing is props, I mentioned somewhere above about 50mm props, do you think this would be sufficient? or could I afford to scale it down a bit?

And how much space should I leave between them and the hull in the tunnel?


Regards,
Louis.

pompebled

Hi Louis,

The Bühler motors I mentioned can turn 50 mm props, provided they are 'normal' scale props, not the very coarse pitched race props.

If you look for Raboesch, they have a lot of scale props.

Raboesch also has props for use in Kort ducts, used on tugs to enhance thrust, where the tips are flattened to fit in the ducts snuggly.

Having a tunnel around the section where the props sit, with a wire mesh to keep out weeds, to the front, would make the propulsion more powerful and protects your props.

Not knowing how much load the boat will have to carry, I don't have any comments on what shape the hulls should be, square(ish), rounded or V-shaped, regarding the boyancy required.

Regards, Jan.