robert12319

Hi, i am new to this. The boat is a custom hull designed like an aircraft carrier but not scale. 6' long and 1 foot 6 wide. it will have to airsoft guns a sub hanger and a functioning rocket launch pad. It will also be solar powered so it will weigh like fifty pounds plus hull. I plan to make the hull out of fiberglass. I also want to make a catapult and arrestor cable system, i have a robotics kit and a small compressor with pistons that operate at 100psi. Some help on propulsion ideas would be greatly appreciated. i figured this forum is the closest one to what i want. sorry if it is way off, but if you can tell me where to post this i will gladly move it.

Thanks
Robert

HoaRC

This will cost you a $1000. A 6 feet long ship will be slow, clumsy, and won't handle current, waves or wind. Try this: get three RTR boats on ebay, put a catapult on one, airsoft gun on the other. Forget launching rockets from an rc boat it's illegal in the USA. Have you and two of your friends battle it out. For airsoft gun, buy an electric airsoft pistol and mount it inside the boat or buy a hen long tank, take the top off and put on the boat. Connect servo/switch to trigger. Use water biodegradable bbs.

johnmCA72

Just for reference, a WWII-era Essex carrier in 1:144 scale (common for combat) comes out to 72-2/3" long x 7-3/4" beam. You're in the ballpark length-wise, but quite beamy, compared to what's pretty common for a combat ship.

The big question for you to decide is, how fast do you want to go? I don't think that you're going to be able to get a speed that's meaningful as far as providing lift for your aircraft is concerned. If you want it to at least "appear" to be going a reasonable speed, consider that the Essex' 33 kts scales out in 1:144 to about 34 seconds to run 100'. Although, not being scale & having the collection of armament/equipment you list, "reality" may not even be part of your equation (not meant as a put-down; I have no idea what your objective is, just commenting that it's nothing like anything actually/ever afloat in 1:1 scale).

I don't know a thing about your hull other than that it's pretty tubby. That suggests that it probably won't go very fast without some outrageous power applied (which is a problem, since you'll probably have limited power available). I don't know whether it's going to plane or displace. A planing hull can go a lot faster, but takes a lot of power to get up to speed & won't be very stable as far as launching/recovering planes, launching rockets, or firing guns accurately are concerned. Since you're going to use solar power (exclusively, or to charge onboard batteries?) you're limited to whatever power your cells can provide. That's going to cut the choices down a lot because you'll need a very efficient drive train. Since solar power is a requirement/limitation, start with what voltage & current are available. That's your "Power Budget".

Besides motors, props & transmission are your big concerns. Props with larger diameters, steeper pitch, & greater number of blades generally take more power to turn than smaller diameter, shallower pitch, smaller number of blades. However, larger/steeper/more blades produce greater thrust for a given power input than do smaller/shallower/fewer blades. Just as a wild guess, I'd suggest driving 2 props with 4-5 blades each, about 2-2.5" diameter, & a pitch angle of about 25-30 deg., for starters. That suggestion is based on my own experience & preferences to drive similar-sized ships to about that speed. I'd use a pair of Mabuchi RS-540SH motors, direct drive, & 6V. That combination would probably get you to a bit over scale Essex speed - or maybe not. I think you're in for a lot of trial-&-error to find what works well with your requirements. 6V may not be practical for your power system (I have no idea what voltage & current are going to be available), & the RS-540SH motors will probably draw more current than what you can provide.

You might want to look into brushless motors. I don't have any personal experience with them, but I understand that they can provide useful power at a wide range of speeds & can be very efficient. Any sort of transmission is going to rob some power from the overall system, so you might want to try to use direct drive if possible. If not, select a transmission ratio that lets your motors run at THEIR most efficient speed while driving the props at a speed that you want for your hull. There are really WAY too many unknowns to be able to tell you exactly (or, really, even very close) what to use.

I would suggest, though, that you try to settle on a prop size. Make sure to space your shafts so that something like around 2.5-3" props will just barely clear the hull, which sets the maximum prop diameter that you'll be able to use. You might consider buying several sets of props, with different blade counts & pitches, at or near the same diameter. Props can be changed pretty easily. Make sure you use a common hub size for all, & let that determine your hub (shaft) size. Try several different motors WITH BATTERIES in your completed & ballasted hull, just to see what sort of performance you can expect. Once you've got a good handle on what sort of power it's going to take to propel your hull at (whatever) speed for (however long) running time, then you can start looking for ways to improve efficiency to the point where solar power might be viable (or, it might not be at all!).

Like I said, I think you're in for a lot of trial-&-error experimentation. HoaRC suggested that it will cost you about $1000; I think you'll be lucky to get away spending twice that, just to get the basic hull working well, never mind catapults, arrestors, guns, rockets, etc. (what about aircraft, to be launched & recovered?). A lot of what you spend will end up in bins because it just won't work well for this project. That's just the nature of trial-&-error. You should also expect to spend a considerable amount of time, testing & tweaking. I'd suggest breaking the project down into parts, & solving each part 1 at a time. For now, get the hull to the point where it can contain everything that you think you'll need (in terms of space & weight payload) at whatever speed you need on the power that's available. "Best guess" is gong to have to do for most parameters, but the more you can nail down precisely, the better.

Good luck, & please continue to post progress, questions, etc.

JM

robert12319

the solar power is really just to extend the battery life, and no, scale isn't an objective. I would not be able to land my eflite blade cp+ on it. The battery is huge, 26 amp hour sealed lead acid battery. 12 volts. I was thinking three graupner jet drives with speed 700 motors. the boat is going to be run on a couple of systems, one will be for driving and the other for fun and games off the deck, such as planes, helicopters and subs. the thing is going to haul around a 10lbs toothed anchor so i can turn of motors without it crashing into something. the deck will be run of off VEX robotics compatible parts. not necessarily VEX but stuff that can come off its controller, in other words PWM directed objects and sensors. if that sounds possible i would like to do that because i wount have to worry about props going in our boat on the way to the island i go to.

Thanks guys
Robert

robert12319

Oh i forgot to say, nothings made yet all drawing board for summer, im in highschool so i have awhile to design, the hull will most likely look like a tanker due to lack of skills in making a mould for the glass, i was thinking a pt boat style hull might be stable enough but i dont know about the efficiency for driving. It needs to be stable but also be movable, biggest problem. I have everything needed to make the boat but the drive systems, batteries and solar. my dad is buying the solar so he can charge his laptop at night off of the stored battery power, though he might not get that much, hehe.

Umi_Ryuzuki

With a ship that large, you won't need solar.
My 6'-8" light cruiser could run around the pond all day on a one 6v-7ah gell cell.
It could speed around quite well on 12volts. The batteries only weigh about 10 pounds, so
you will be able to load two or more batteries into the boat at the size you are proposing.


With some careful planning and ingenuity, you should be able to do everything you have proposed.

[8D]

HoaRC

I agree! Take it one step at a time! Some projects last months and years but if you plan well, budget, and stick to it you'll get it done.

Graft Zeppelin

Me and my friends buitl a 31 foot Graft Zepplin it took 10 of use 6 mounts.
but it holds Complement of 15
5 × Messerschmitt Bf 109 fighters, 2 airsoft guns
5 × Junkers Ju 87 dive bombers,2 airsoft guns+bomb drop capability
5 × Fieseler Fi 167 torpedo bombers, 1 airsoft gun and one electric torpedo(torpedo is sketchy as hell)

all are RC airplanes and the carrier can be fully RC or we stick 2 people in it

it was actually prety cheap we found an old 31 foot sail boat in kiel and cut off the top then added the flight deck and superstucture
we can hold all 15 planes in the hangar and each is pulled out on to the elevator a by a computurized robot (took 3 mounts of programning) after it on deck we point her into the wind and throw the throttle and shes gone. for landing we use a TV camera with a cross hair line up the plane with the cross hair and land the plane on the deck with the arresting wires. we used a 4 strock 90horse power motor to dive the two skrews.

will post pictures

robert12319

hey guys, im working on the jull designs in solidworks 08. just wondering, for stability should hull be both deep and wide or just wide. it needs to be 16" or more wide and 10" or more deep to fit the FRC batteries im getting for free. they are the old batteries from the robot. they are motorcycle batteries. also, how do i design area round jet drives, do i level it out or just deal with it when i mount them, using them because there are many rocks were this boat will operate [&o]
Thanks Robert

HoaRC

Dude, you need to post pictures.

robert12319

The dimensiones are 19.06 wide by 16.47 deep, sorry if its blurry. this is the only rib so far. just got solidworks last night, still playing with. and i just realized i put it on the wrong plane. Ill have to fix that. i should have a hull designed in solidworks by tomorrow night, then u guys can tweak it, if you want to. sorry about the no pics though, i just don't have anything.

Thanks
Robert

Umi_Ryuzuki

You can get a set of frame plans from floating drydock for a battleship, or carrier, and enlarge them to
meet your needs.

http://floatingdrydock.com/HULL.htm


One of our clubs eight foot cruisers ran on two pitman motors.
Plenty of power and maneuverablitiy.

The Graf Spee is outfitted similarly.


oh, here are some hull lines for the Bismarck that you might modify.
http://www.bismarck-class.dk/miscell...ok_review.html

And a Bulk carrier/tanker like you were imagining for your start...
http://en.wikipedia.org/wiki/Image:C...lines_plan.svg

[8D]
[8D]

beer=food

l think l want a new hobby the trucks n cars , choppers , n planes, are just LOL, airsoft guns on boats, LOLOL, u turkies are gunna get me killed when me wife finds out !

robert12319

This thread is coming back, reviving the project, finally. I have to sketch this stuff by hand, hope to be doing some of it over the weekend. Making my own interpretation of an azimuth thruster with probably a 3" prop. can anyone help with pitch. planing on putting on 2-4. The boat is still a tub, looking at about 80" length and at least 10" wide in the water growing to 20" above so as to land a plane. Going to be powered by a motorcycle battery or 2, driven by 350 watt motors with a power band near 1 ftlb of torque at 2360rpm max of 5360rpm. 1 per thruster. also going to have a full pneumatic catapult and most likely arrestor cables attached to rc car shocks. The plan is to make it land a rc piper cub, since cubs almost land themselves. I have since grown capable in a machine shop with access to a 3d printer and 3 axis cnc. Plane is going to be similar to this http://www.hobby-lobby.com/j_3_cub_b...85563_prd1.htm and the thrusters are my own interpretation of this http://www.thrustmastertexas.com/ima...erCutLarge.jpg. I really need help sizing the prop, I havent ever done this before. Also, can I get away with such a slow motor with a steep bladed prop?

grael

Planes: the cub looks like a good choice, high wings and or dihedral (sloping to higher tips) helps an aircraft to self right horizontally. Cesnas are also well known for easy flying. My latest glider on the other hand, is perfectly centred, but gradually wanders to which ever side it's slightly leaning to. Great for light winds like today, when sweeping turns conserve height.

You might consider a biplane though, like this for example:
http://www.hobbyking.com/hobbyking/s...w/_Motor_&_ESC
as biplanes generate great lift at low speeds, and are a more compact design. It's half the wingspan of the one you're looking at.

I think for the boat, that you mean a low pitch prop, opposite of what I would consider steep. Equivalent of running in a low gear.

Possibly around 50mm diameter, and a pitch that screws more like 40mm per revolution.

You'll want to waterproof the plane...

For waterproofing, I gum up one end of the ESC with bluetack, and fill the other end with epoxy resin. works really well.

For servos, box them with nutral cure silicon all the way around, and use an O ring at the top, just under the servo horn. Thats been my most durable fix to date for my jetboat... keeps on working now.

For radio receiver, bluetack around the wires, and then a thick plastic bag rubber banded around the receiver and over the wires.

robert12319

Hey grael, for props I was looking at Dumas brass props, whats the difference between 2,3,4,5 blade props, I have a feeling i want something like a four blade. I was actually thinking about 3" diameter as it is easy to buy 3" ID pipe to make the drive unit around. Also, since my rpm is so low, dont I want higher pitch for more speed, I at least need to acheive 6mph or I am going to get swamped by waves. Some boats make 3' waves on Winni, and I don't want my scholarship project going down that easy I was thinking that 4 blade scale props could work, but now I am to thinking that scale might hurt me, as does that have to do with pitch also? http://www.dumasestore.com/catalog/i...hp?cPath=72_76

Umi_Ryuzuki

Seems like most boats run around 9000 rpm...
So the CIM might be a bit low in rpm...
The AM-0316 would probably work if you gear it down 2:1 to 3:1 ratio.
That will give the set up extra torque also to swing a larger propeller.

Both motors have an awfully high amp draw, but gearing the AM-0316 down should
reduce that.

You don't have a lot of choice in pitch...The propellers are what they are. Bending or
twisting the blades on these often results in the removal of a blade... [&:]

robert12319

well. i dont really care about the amp draw, im driving with a motorcycle battery, 18 amp hours. Also, that number is stall current or "max effiencency" not likely that water will put near that resistance on them. You cant even stop those motors by hand 1:1 even if you put a grip on the output. I really was thinking CIMS geared 2:1, but i guess a fisher price 3:2 for 10k rpm would work pretty well too. never got around to sketching, been a little busy, we will have to see if I can do it tomorrow during study.

robert12319

Umi, can you just give me some specs from some of your boats in terms of length, beam, weight, and draft then the motor names so I can look up specs + what is on them for props. I know I am biting off far more than I can chew so I am trying to get as much help as possible, also, do you know any tugboat people, I feel that they may have some good experience with this kind project due to weight and what not. I also have been given a contact who is a naval engineer, and I intend to talk with him soon. Thanks Robert

Umi_Ryuzuki

My destroyer is 56" long, weighs 15lbs, and runs on two 14 volt pittman motors. the propellers are
just some brass stamped petals about 1.5" in diameter.

Some of the bigger ships the heavy cruisers are 96" long and weigh about 100lbs to the water line.
They also run on pittman motors. Typically 12 volts... heres a picture of a set...
I would guess that the propellers are about 2-2.25" in diameter.

.

robert12319

wow, those look like they see quite a bit of the depths, do know approximately the speed of the ships? With what you are saying 2 3" props in turrets thrusters actually sounds pretty good. Might just add a third prop if it needs more speed.
Thanks, Robert

Umi_Ryuzuki

The speeds of the larger ships are usually set at 33-41 seconds per 100 feet...

1.63-2.04 mph... but if allowed to run unlimited, no telling really, I would imagine that
four miles per hour would easily be attainable, six with just a bit of tweeking.

[8D]

kotori

Robert, here's a few ideas for you.

1) if you're designing your own hull, I would highly recommend that you try out the free CAD program DELFTship. It's a surface modeler specifically intended for ship design. I use it to make computer models of historical ships, when my paper plans don't provide enough detail for an accurate hull. This program can also calculate statistics like displacement, water resistance formulas, etc. Very nifty stuff. My most recent project was the Russian predreadnought battleship Borodino:






They also have a number of free hull designs online, including a number of cargo ships, super-tankers, and other tubby hulls. You would just need to re-scale the hull you want to the correct size, pick which ribs and cross-sections you want, and tell it to generate a set of plans. Very useful.

2) have you considered buying a fiberglass hull pre-built? There are a number of R/C combat suppliers, who make warship hulls out of fiberglass. You can buy a large 1:144 scale battleship hull, and convert it into a carrier. Your best bet for this would probably be the Strike Models USS Iowa hull:
http://www.strikemodels.com/products/ships/uss-iowa/
The best part of this is that, by buying a hull ready-made, you don't have to worry about designing a hull, building a mold, making your own fiberglass hull, getting a thick enough layer of fiberglass, etc. Just open the box and start installing components. The Iowa hull in particular is big, stable, and sleek. And if you install the skegs, you'll have extra protection against rocks and other underwater obstacles.

Whichever solution you choose, Grael is right: you'll need to waterproof everything in your planes and helicopters, and make sure they float. You wouldn't want to wreck an expensive helicopter or airplane just because you missed the flight deck by a foot. There are a number of waterproof servos available, from Traxxas and other companies, or you can seal them yourself. The method Grael described is one way, suitable for shallow-water immersion. Other R/C combat skippers on this forum know of additional methods for a wider range of conditions, that we can describe if you want.

Hydro Junkie

Not so sure I'd want to use an Iowa class hull for a carrier. I'd go a more historical route and go with a Lexington class BC hull as it was a more readily adaptable to that kind of modification. The Iowa has that long thin bow that doesn't have a lot of floatation in it to begin with that was more for getting higher speeds than anything else

robert12319

Hi guys, sorry I have been inactive lately. I've been getting ready for finals, Highschool is almost over, Hurray. That cad program looks cool but im not sure how much easier it will really be than solidworks, though I will give it a shot. I have been discussing this idea with a few of my mentors and I still would like to make my own hull. Reasons being cost and getting a shape that I like. This thing is not gonna be anywhere near scale nor is it intended to be. I personally am not a fan of going nuts over scale. I just want something fun and different at a fraction of the price of something similar retail. As I have access to a machine shop and 3d printer, i can make many of the parts on my own, and it is an easy way to keep costs down. 2 questions, what do you think of Azimuth thrusters as opposed to direct drive for amount of thrust and maneuverability, and what do you think would happen if I printed my own props. The printer works by gluing .1 mm sheets of pvc together with pvc cement and then it scores the shape into the layer, until it has reached the proper depth. It does not make a smooth finish, but I think I could sand it. More or less, would a pvc prop hold up to moving a 9' boat I guess.