brickhead179

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I just wandered into this hobby and i want to know how to start building a warship to sail and fight with. After i get the plans what should i do? Do i get balsa wood and make a frame, then coat it in thin balsa? Or is there fiberglass hulls involved? Iv seen people get fiberglass hulls and then cut squares throughout the hull and then put the thin balsa on it followed by the placement of electronics, guns, and such. But i need to know for sure. Can anybody tell me all the steps from reading the plans to actually building from them. Thanks

johnmCA72

Here's a series of articles. Not exactly a "How-to", more of a "How-did", complete with a few instances of things learned the hard way:

https://ntxbg.org/KnowledgeBase/?cat...ticle&art_id=4
https://ntxbg.org/KnowledgeBase/?cat...ticle&art_id=5
https://ntxbg.org/KnowledgeBase/?cat...ticle&art_id=6
https://ntxbg.org/KnowledgeBase/?cat...ticle&art_id=7
https://ntxbg.org/KnowledgeBase/?cat...ticle&art_id=8
https://ntxbg.org/KnowledgeBase/?cat...ticle&art_id=9

There are plenty of other articles around, too. Look for links in this forum (I think there's a "sticky" at the top, that lists known combat club at the time it was posted).

JM

Raymondpb

Hi JM, Thanks for posting those articles; very good stuff there. My 16 year old son has embarked upon a 1/84th scale Arleigh Burke class destroyer build project from scratch and those articles will help us work out some of our ‘gray area’ engineering issues. You must understand we have never built a ship before let alone from scratch. As of last evening he had all his bulkheads and keel cut out. Today he will laminate the two keel pieces together and cut out the rail caps and stringers.

His fundamental structural design differs a bit from what you have presented in that his keel is laminated ply and he is not using as many bulkheads (ribs) as you have. He (we) is counting on gaining strength from a stronger skin of burch ply overlaid with fiberglass. Understand that this is an RC project with no intention of taking this model into battle; yet. Obviously we will not be legal without the balsa skin but this is just his first scratch built wooden ship. We are considering a couple of astatically pleasing combat systems. For one of them we are planning on flying a Helo from the fantail and the other, well, we still need to study all the safety implications before we can commit to design and testing. Call us crazy; you would not be the first but we have a little experience with model rockets and have a design for a small rocket we may be able to retro fit into a small missile battery. In order to be safe we need multiple safety interlocks in place such as 1) ship list level switch 2) a dead mans safety arming switch 3) launch trigger and 4) a safety interlock independent of the radio remote such as a timer enabled circuit to ensure the system could not be enabled until after a predetermined amount of time has elapsed to ensure all the arming and ship launching procedures have a occurred and the ship is safely established out at sea. If this system comes to fruition it would probably be employed in a modular form so as to not take away from the normal scale appearance and would only be deployed for 4th of July evening celebrations.

Ok, enough of that crazy talk. I would like to ask you a few questions if I could. We are estimating that a ship of this size will be at least 20 pounds when complete; are we in the ballpark here?

Can you help us determine motor and battery size?

When was the boat in the articles built? Could you not have used a speed controller and enable the ability for intermediate speeds?

Where did you find the same sized but reversed pitch propellers to enable you’re your motors to rotate in opposite directions?

Ray
Mattawan, MI
[email protected]

johnmCA72

Nor had I, at the time those articles were written. That was sort of the point. Nobody around to help, either, except some remote advice.

If you have a combat club nearby, I'd strongly advise talking to them if you have even the slightest inclination of ever getting into combat. Find out what they do or don't allow, their building standards, scale(s), time period, etc. so that you don't end up building yourself a white elephant (unless that doesn't matter to you).

Clarify terms: A rib provides the shape of the hull, in other words an element of framing. A bulkhead is basically a wall, & stops things (like water) from passing through it.

Number & spacing of ribs in my case were determined by rule for the combat I was intending to get involved in.

"Yet" may turn into "never" unless you know of a combat club that will allow fiberglassed plywood skin. Be aware that, if you ever plan to get involved in combat with this ship, you're probably going to need some other skin. The whole point is to cause & receive damage, by punching holes. It's pretty easy to build an impenetrable hull - you've just described a pretty good way to do it. Combat warships get re-skinned frequently. A fiberglassed plywood skin is probably not going to come off easily, without damaging the frame. Of course, this is only a consideration if you ever plan to convert the ship into a combat ship. If not, no problem. But some of the decisions you seem to have made already will make it very difficult to convert, if you ever want to.

What's aesthetically pleasing & what's effective in combat are very seldom the same. Every minute or dollar spent on cosmetics takes away from what you can spend on making it battle-worthy.

Note: Most (all that I know of) combat clubs specifically prohibit pyrotechnics of any kind.

Flt IIA is 92' long, 59' wide, & displaces 9200 tons. In 1:84 scale that comes out to about 6' by 8.4" & should weigh about 31 lbs.

Start with the props. That's what drives the ship through the water. How scale do you want to be? If you want everything to look right, get scale-sized props with the same blade count & basic blade shape as what the 1:1 ships use - or as close of an approximation as you can find (my guess is that you'll be able to find something pretty darn close, if you want to). If not, pick something with 4 or 5 blades & lots of surface area. Larger diameter means more bite, so some builders go oversize. Be aware that there can be issues of hull clearance or shaft angle when you go too much oversize, not to mention what it looks like. Some combat clubs require props to be in scale or allow some %-age over. Some clubs don't restrict prop size or placement at all.

Pitch is like the gears in your car's transmission. Higher pitch lets you move more water & go faster. Lower pitch gives you quicker acceleration. Acceleration is handy in combat, & top speed is usually regulated. Once you settle on a pitch, you can calculate approx. how many RPMs your shafts should turn to move your ship through the water at the speed you want. Note that water isn't exactly solid - you'll experience what's called "slip". In other words, if the pitch of a prop is such that it should propel the ship some distance 'x' in a single turn, you're actually going to get something less than 'x'. I'd give it a factor of about 30-50%.

Once you have an idea how many turns of the shaft it's going to take to get you into the ballpark of your target speed, look for a way of driving the shaft at that speed. That means some combination of motor & transmission. Brushed DC electric motors are often rated in terms of current (among other attributes) by their makers. It's usually safe to assume that the motor maker will rate their products in a way that's most favorable to them, which means that they'll pick a test speed that draws the least current. The manufacturer's "rated" speed would be where the motor is most efficient, & that's where you want it to run in your ship so that you'll last longest amount of time on a battery charge. So, if you see a motor that's spec-ed to draw 0.8A at 10,000 RPM, & you've figured that you need to run at around 8,000 RPM, that might work out fine. At least, you can probably eliminate a motor that draws 6.0A at 5,000 RPM! Everything that you can eliminate helps you make your decision! Note also what voltage they're rated at. Rated voltage doesn't necessarily mean you can't use some other voltage, just that this is what was used for testing. You may get different torque, speed, current draw, etc. at some other voltage in your ship, so just be aware of apples-to-oranges comparisons. At the same time, you need to look for something that's fairly close to what you'll be using; a motor that's tested & rated at 48V might be completely unsuitable for 6V because the difference is so great that the parameters aren't even close (you might even need to hit it with something like 18-24V to even get it to start turning!). Torque is another consideration. Torque is, basically, power applied to a rotating shaft instead of moving something in a straight line. It's a measure of how much power you need to put into a shaft to get it to turn one rotation. A small motor may, on paper, be able to run 15,000 RPM while drawing only a few dozen milli-amps. However, it may not be able to overcome the opposing forces such as friction in the drive train, resistance of water, etc. In general, bigger (in terms of diameter, blade-count, & blade surface area) & steeper-pitched props will need more torque put in. I don't have any specifics about what torque ranges might be needed for any particular combination of ship, speed, & running gear, but I can offer some suggestions that I've known to work. "Racing" motors are big-time overkill, draw way too much power (racers only run for a few minutes at a time; you'll probably want to run all day), & cost way too much. I use surplus tool motors (i.e. for drills, etc.) that can be found in a wide variety at good prices.

Suppose you find a motor that gives you plenty of torque, draws low current, is a size & weight that you can live with, but runs most happily at 15,000 RPM, when you need 5,000 RPM delivered to your props shafts. That's when a transmission would be needed, to reduce speed. Reducing speed increases torque (all else being equal, which it never is 100% in real life!), which is generally a good thing & lets you get away with a smaller/lower-torque motor than you might need otherwise. Because of the torque-multiplying effect of a transmission, you may get a little more speed out than the basic numbers might suggest. In the current example, reducing 15,000 to 5,000 suggests a 3:1 ratio. However, because of the torque differences, you might only be able to turn the directly-driven motor at something like 12-13,000, while the reducer might let it run at closer to the "happy" speed. Again, I don't have any empirical data, & it probably isn't worth the trouble to bother with it anyway, since there are so many other factors in play. The point is, just not to be surprised if a change in gear ratio doesn't have exactly the same corresponding change in speed when it's all put together.

Using a transmission can be a big help if you're unsure of your combination, or if you have the "ends" (i.e. props & motors) selected for whatever reason, & need to "tweak" the middle. Depending on how it's placed & used, a transmission can get in the way of other components, or it can even be used to clear out key spaces. An example of the latter was a Scharnhorst that I helped somebody build. Scharnhorst has 3 shafts, 1 in the center & 2 outboard. We decided that we wanted to drive only the center prop, so that 100% of the propwash gets directed at the (twin) rudders all the time. This would allow better turning than if 50% or more of the thrust was directed away from the rudders, but the outboard props. The problem with this idea was that there was no room for a motor in the obvious spot for one, just ahead of where the center shaft enters the hull - there was this small matter of a main battery gun turret in that spot, & since the point of a warship is to serve as a gun platform, that had to stay where it was. The solution we found was to turn the motor around, raise it up above the prop shaft, & connect the shafts using chain & sprockets. If you need or want a transmission, here are the basic types:

Gears: On the plus side, gears are very solid, the math is simple (at least as far a calculating ratios), & don't slip. Downside is that they need to be set up with a greater degree of precision than most hobbyists can handle, they can be noisy (especially if they're not set right), & you can't always configure them in every combination that you might like. They can also get jammed if some kind of junk finds its way into where it shouldn't be, & they can wear too much if they aren't set up just right. Gears can also be used to reverse shaft direction, & make it possible to drive 2 opposing shafts from a single motor if you want to.

Chain & sprockets: Advantage of gears in the sense of being solid & able to avoid slipping. You don't have to place the shaft centers with the precision of gears because you can use idlers or flexible mounts to keep the right tension on the chain, & it's fairly tolerant of misalignment in general (shafts don't have to be perfectly parallel, etc.). You can also use a greater variety of sprocket combination to get just the ratio you want. Chains can be a little noisy, can get jammed with crud, & can break or jump off the sprockets (usually not a problem if they're tensioned right & spans kept short).

Gilmer (internal-tooth, or "timing" ) belt & pulleys: Slip-resistance close to that of chain & sprockets, along with the ability to mix & match just about any pulley combination. Lots quieter than chain & sprockets or gears, nearly as quite as direct drive. Spans need to be kept short & under proper tension, which isn't a big problem, just something to be aware of.

Any kind of drive that depends on friction to transfer power should be avoided. It WILL slip.

Direct drive is the quietest, simplest, loses the least power, & takes the least amount of space. It's also the least flexible option.

Electronic speed controls (ESCs) will lose some power. You won't get 100% of the speed out of a given motor than you would, had you bypassed the ESC entirely & run directly off the battery. The convenience of being able to use a continuous range of speeds generally outweighs the slight loss. Set up everything to work at maximum speed with the ESC "wide open". That will let you get the most out of your speed control range. Pick an ESC that's rated for the max. stall current of ALL your motors, then give it an extra 50% safety factor at least. Motors will draw their max. current when they're stalled - such as if your drive train gets jammed, props clogged with weeds, etc. A motor that hums along happily, drawing 1A at 15,000 RPM might draw 10A when it's stalled. 2 of those will draw 20A, & your system needs to be able to handle it. I'd use a 30A ESC, minimum, for that kind of setup.

As for batteries: As much as you can carry! You're going to need plenty of ballast, to get your ship to float at the correct scale waterline. It's hard to find more effective ballast than boxes of lead, & if they can provide power, so much the better! Mount them as low in the hull as you can, for stability. Amp-hour (AH) ratings are key & refer to the amount of total power available. This translates directly to running time, & you want to be able to run as long as you can. A 12AH-rated battery, in a ship that draws 2A when everything is running flat-out, "should" be able to run continuously for 6 hours. As usual, nothing is ever absolute, so I wouldn't set my watch by that, but it's a decent ballpark estimate. Discharge rating is another factor to consider. Some battery technologies can't deliver power at the "flow" rate you need unless you use the more expensive models. Discharge is spec-ed using a "C" rating, that I'll leave up to you to research - I generally don't care, because I long ago settled on a preferred battery technology. As for that, there are several around: Sealed Lead-Acid (SLA, or "gel cell"), NiCd (been around forever), NiMH, Li-ion, etc. For a ship the size of yours, "high tech" isn't going to be as important as reliability & flexibility. It's not like an aircraft, or a racing boat, where you need to trim every oz. of weight you can, to keep flying longer or go faster. Personally, I use SLA batteries for everything except small ships, where there just isn't enough space or the weight is needed for other, more important things (like weapons, gas, CO2 delivery, etc. that's basically the same for any ship). I also like to use 6V because I can use it to run everything, including radio receiver, servos, etc. Other voltages, common in go-fast boats (7.2V, 8.4V, 9.6V, 12V, etc.) mean that separate electrical systems are needed, or voltage regulators/battery elimination circuits (BECs) to split out the right voltage for those items. Radios, servos, etc. are quite happy on 6V, even though they normally run on 4.8V. I never, ever, use the BECs available on ESCs. They're usually good only for about the amount of current that a receiver draws, & not much else. The sort of equipment found on a working ship usually draws much more than they can deliver, which causes all sorts of problems (of the expensive and annoying kind, too!). So, I always disable BECs, wherever I can find them. That often means snipping the (red) power lead on the "servo" connector (from receiver to ESC).

Now, for the "short" answer. I've found the following combination to work well for me in a variety of ships, of the approx. size of yours:

Battery: 6V SLA, 12-14AH, 2 per ship. I generally split power to separate anything "dirty" (i.e. motors, solenoids, etc.; anything that's an inductive load) vs. "clean" (radio, computers/controllers, etc. that doesn't like sharing power with inductive loads).

Speed control: MTroniks Marine, 30A. These are waterproof (which is important for ships designed to sink), & also have instant reverse (also important; many ESCs have delayed reverse, & some don't have it at all!).

Motors: Mabuchi RS-540SH, 2 per ship. I drive only the inboard shafts of 4-shaft ships to direct most propwash across the rudder(s) & let the outboard shafts sit idle (with props). These are widely available as surplus for $5 or less. They're "good" in terms of torque, current, size, weight, & speed. I don't have the exact specs in front of me, but they're easy to find (or something close; look them up & use as a baseline for comparison). Basically, they're about 2.25" long by 1" dia., with a 1/8" shaft (I settled on 1/8" shafting long ago, which helps reduce my choices to something manageable, although it's certainly possible to adapt different shaft sizes if you need to; I choose not to). If I recall correctly, they'll run 10-12,000 RPM on 6V, drawing about 1A with no load.

Drive train: I usually use chain-and-sprockets (Delrin plastic, from ServoLink, that I discovered when building CA-72). I do have a couple of ships with direct drive. Drive ratios are tweaked to get just above the desired speed (regulated by rule), so that I can adjust precisely with my transmitters' end-point adjustments (EPAs). If it's close but just slightly over, there's plenty of room for fine adjustment; if your speed is over by more than about 5-10%, then it's harder to fine-tune the EPA, plus you'll lose a lot of your low-speed control. Final drive ratios end up being about 3:1 or 5:2, if I remember right (for those ships that aren't direct-drive, or 1:1).

Props: I don't use oversize props, even though I can (per rule). Larger props can have clearance problems with the hull. If you change the locations to accommodate the oversized props, then it changes your shaft angles & can put the motors where you don't necessarily want them. I also use "scale" blade counts, & try to find a blade shape that's close to original. Pitch is difficult-to-impossible to find, for original 1:1 ships. "Pitch" is also mis-used by scale prop makers - they usually quote it in degrees (angle of the blades). I generally use the shallowest pitch that the maker offers, usually about 25º.

1998.

Absolutely. In fact, that ship has been retrofitted with a speed control. At the time it was built, everybody was using switches. Speed controls were expensive, & waterproof models weren't available. Killing a $60+ speed control every time you sink wasn't anybody's idea of reasonable cost.

That source is long gone, but there are several others. Scale ship props can be found in a variety of sizes, pitches, blade counts, blade shapes, & in either RH or LH. Google "model" "ship" & "propeller". One good source that I've used for a variety of items is: http://www.loyalhannadockyard.com/

JM

Raymondpb

Hi JM, I am sorry to report that there are no clubs in my immediate area but there are a few within 100 miles or so. While combat sounds like fun it is not really the focus of this current first learner project. At this point in our hobby career we are more interested absorbing overall build knowledge more so than the combat branch of the hobby. Actually I am most interested letting my Sons creativity blossom while he studies elementary engineering while he does not even know it. If he wants to build it then I will support it ya know? So to make a long story short, a white elephant is ok if that’s the direction he wants to take with this one.

Yes, being new to this hobby our terminology is off a bit. In order to keep costs down on this project and because we intend to employ fiberglass over wood we have elected to use a cheaper grade of sheet stock (luaun) for our framing. All our “rib’s� are currently “bulkheads�. Once the hull is framed, sheathed (planked) and the external side is glassed we will use a hand held mini router/dermal to cut lightening holes in the bulk heads to convert them to more of a rib. One thing I think we will do today is cut out and incorporate an intermediate structural rib in between each bulkhead for extra strength. Our rib/bulkhead spacing is actually arbitrary as we have no intention of building it to ‘scale’ on the inside also. I am letting my son make these decisions: I am only a consultant, assistant and part time woodworking technique trainer.

Thanks for the weight conversion. Does that mean that if she is built to these dimensions and if her total ready to launch weight is 31 pounds that she should sit naturally in the water at the water lines depth?

Exactly what else would we need determine to be able to make preliminary motor and battery choices. Yea, I know 1/84th scale is not a standard size to build to and we are going to be challenged in getting accessories to fit exactly but then again, I am not making the decisions� Thanks for the link to Loyal Hanna Dockyard’s website. It appears that it should bear much fruit in sourcing parts for this project.

Sorry my post is so long but I am trying to convey the nature of our project in hopes keeping you interested even though it is not a ‘combat build’.

Thanks
Ray

Raymondpb

JM, The first time I looked at your post I did not see the prop, motor, gearign and battery stuff in the middle of the post. Ok, off to reread it.

Thanks
Ray

Raymondpb

JM, Thanks for the good info. I must digest some of it but it is all very usefull. This is a very exciteing project. For now we our out to the shop to make some more saw dust and hopfull spread some glue later this eveining.

Ray

johnmCA72

Neither did I, so I started one!

I wouldn't necessarily take that as absolute. Try to build a little lighter, if you can. It's easy to add ballast, but can be tough to lighten a ship that sits too low.

JM

Raymondpb

Thanks for the good advice JM. The Hulls frame is done and we are starting in on sheeting it. Here are a few pics of the frame. I know its design is a bit unconventional but we are banking on gaining strength from fiberglass. Actually we have installed some longitudinal stringers since these photos were taken and the frame is surprisingly ridged.

Ray

johnmCA72

First time I built a plywood-frame hull, I thought for sure I could stand on it without breaking it - it seemed that strong!

Fortunately, I never did test that hypothesis!

JM

Raymondpb

Well, the hull has been sheethed and covered with one coat of glass inside and out. Wow, that was fun.

Raymond.

djmason9

Here's a video of how to build on too
http://www.rcgawker.com/2009/07/rc-w...battle-groups/

corpestipp

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check this out guys! the baddest ass toy boat ever!! http://www.bismarck-class.dk/shipmod...speeterra.html

Raymondpb

Wow! I mean Wooow! That guy definietly has two things in abundance. One is talent the other is time.

Ray