ernest2

hi!! i'm planning to scratch build a grand banks 42 or 46 classic. i'm basically new to the hobby, but i do have a lot of magazines and read alot about model boating.. and i do research.[8D] can anyone suggest what motor and prop size i used? i want it to have a good speed, but not too much.. and can anyone suggest hardwares? i'm planning to build my own... i'm a little tight on a budget.. i'm initally planning to buy dumas hardwares... but i'm from the philippines and shipping is a bit pricey.. i will be building the boat in 1:12 scale so my model would be 42" or 46".. and i guess i will power it with a lead acid if its electric or a .40 size airplane nitro engine.

thanks for any advice

ernest

LtDoc

ernest2,
There's nothing wrong with the 'Dumas' motors and drive trains, but they are kind of expensive. A little 'judiscious' shopping should reduce the component costs some. The shipping is another matter, not much you can do about that.
If it's a choice between electric motors and fuel engines, the deciding factor (for me) is that using a fuel engine usually means that there's no reverse. That's not a 'big deal' with "go fast" boats, but if you plan to do any manuvering, a 'reverse' sure is handy! You could always add a clutch and transmission, but that'$ not alway$ the ea$ie$t thing to do.
In your research, look for boats with the same general hull shape (planing or displacement), that's really the deciding factor on how big of a motor(s) you'll need (among other things like weight).
Also don't overlook motors you may have (or can find) locally. I'm using a motor from a hand drill (120vac) with a 6 volt battery in a tugboat about 24" long and 10(?) pounds. It will almost get onto a 'plane' with a displacement hull, which means it has more than enough power (LOL). Just a suggestion so take it for what it's worth. You might also take a look at the gear drives made by 'Graupner', with or without the motors. The biggest draw back is that they are noisy (but they all are).
Just for the 'heck' of it, take a look at the 'boat' forums/sites in the U.K., seems they do a lot of scratch building over there and may have lots of suggestions.
Good luck and have fun...
- 'Doc

Tachikaze

You could obtain one of these motors from All Electronics and run the boat anywhere from 6V-12V and get what you want speed wish. These are the same type of motors that we use to run combat warships with twin screws and two motors for ships that are over 50". Check through the rest of the motors on the page. Look for high RPM with a low amp draw. This motor that I selected should work well for a boat that size with a 1" to 1 1/4" three bladed prop.
CAT# DCM-165


[link]http://www.allelectronics.com/cgi-bin/category.cgi?category=400200&item=DCM-165&type=store[/link]

ernest2

lildoc, i have 2 tamiya cars, i guess i'll just strip the motors out of it. that would be 2-rs540.. will that be enough to power a 46" long 14" wide grand banks? what would be the size of the props? 2" dumas or 1.5"? i'm actually looking in the hardwares here for materials like brass rods and tube so i can make my own drive gears and just buy the props and drive dogs.. will bronze work?
i've seen the site tachikaze, i really wish i can buy from there, really cheap motors and good amp draw.. but i'm here in manila. i'll to look for any dc motors here.. thanks a lot guys!!!
maybe by march i'll start with the hull construction, hope you'll give me advices again...

ernest

LtDoc

ernest2,
As Tachikaze suggested, a geared motor(s) may not be necessary and a direct drive system may work just fine. A 'Grand Banks' isn't a 'speed' boat although they are fairly fast in the 'full sized' versions. Scale speeds are really much slower than what you'd think (or want), don't worry too much about finding a large motor(s). It's 'better' to have a motor that's too large than too small though, then just be 'easy' on the throttle. The 'extra' speed/power can get you out of some situations (and if you can keep off the throttle you've got more will power than I do LOL!), and it can also get you INTO those situations if you're not careful! Two '540's should be more than enough for your 'Grand Banks'... I'd think.

Making your own drive shafts and stuffing boxes is certainly an option, lots of people do it. You might have to order the bearings (no idea what you may find available there), but that shouldn't be much of a problem. Making allowances for greasing/oiling the drive shaft is something you might think about. Having to disassemble half the boat to get to the stuffing box is a real P.I.T.A. After the first time, you'll know exactly what I mean!

"Scrounging", or 'dumpster diving' can be a very nice source of various parts/material. You'd be amazed at what people throw away. Small appliance service centers, RadioShack, Sears, whatever, are gold mines for small motors, brass, plastic sheets, gears, and 'stuff' you didn't even know you needed! If you have children/grandchildren/neighbors with kids, raid their toy boxes. You wanna be careful, kids are vicious when you mess with their toys!
- 'Doc

blackhole

Hi Guys:
Have had great luck with Loyalhanna Dockyard (www.loyalhannadockyard.com). They have a huge range of motors, props, drive shafts and universals. Looks like they could outfit most any boat. Just thought I would pass it along.

Don

ernest2

thanks blackhole! have anyone of you know this engine? Tamiya Engine 43501 FS-18LT.. i'd like to buy one and use it, because it already have a starter and a clutch, which i think would be nice for a scale boat with some speed

pompebled

Hi Ernest,

Try the scrapyard, see if you can find a car fan motor that is used to cool the radiator, if you'r lucky you get one with ballbearings, multipoled anchor for a fraction of the cost of anything proceded by the word "model".

I have one in my scratchbuilt patrolboat, running on a 12V gelbattery, I get hours of running time. Even using a 65X prop.
Only watercooling the brush holders is usually enough.

For my MTB model I am currently rewire-ing a fanmotor to take the higher voltage.

It's the cheapest way to dependable high torque motors!

Best regards, Jan.

gulfstreamI

Ernest2,
Hello there! I'm also into scratch building, and my main interest is in conversions of static model warships & submarine kits. I practice with the small scale kits before I move on to the big ones. I'm fascinated with the new micro-technology that's recently been available to r/c enthusiasts. What type of Dumas model boat do you plan to build?
Oh, and "Mabuhay - Kabayan"

gulfstream1

ernest2

hi guy! mabuhay gulfstream!!!
i've decided to build a 1/6 scale model of a runabout. i've found a plan on the net, for a full size boat. i guess i just make some modifications to it, because i want the look of a runabout. i am now planning on the power.. i want to have a good speed on it and longer runtimes.. i am thinking of buying a k&b .18 marine engine. any inputs?
thanks!

ernest2

i am also considering buying an os .21 rg-m engine.. i wanted to put clutch on it for added realism.. electric would have been nice but runtime is short, and lead acid are heavy and only 6 volts.. i already have 540 motors from the rc cars.
i'm still undecided up to now what kind of power to put in.

gulfstreamI

ernest2,

We do speak the same language even in R/C hobbies! In your case I think bigger is better. Do you have a specific budget to follow or is it a adjustable? I'm more into electric powered boats. Try to research more on the torque of the .18 marine engines out there & prop set up that would match.

gulfstreamI

ernest2

it's very limited at the moment. will i'm thinking of doing it first in electric then switch to nitro afterwards. maybe you can help me. i have a mabuchi rs540sh motor, how will i set it up so that i can get good speed and long run time? the hardware i gonna use will probably be a 1.75 or 2in prop..

how long have you been into rc boat gulfstream?
thanks!!!

LtDoc

ernest2,
A '540' will run just fine on 6 volts. Considering the size of the prospective boat, putting more than one 6 volt battery in it shouldn't be unreasonable. That would double the run time if they are in parallel, or give you 12 volts if in series (also takes the place of ballast). There are several sources of gel-cell batteries, not all of them are 'huge', and some of them offer a fairly large 'Amp-hour' rating. I think the run time will be longer than what you may expect. If your '540' draws 4 amps, and the battery(s) total 12 Ahr, that's a possible 3 hours of run time at 6 volts, or 1.5 hours at 12 volts. I don't know about you, but my attention span isn't quite that long (LOL)! Also, scale speeds are much slower than what you might think.
(I seriously doubt if a single '540' will draw that much current (4A), so run times should be even longer.) Electric power is a lot easier to 'do' than using an internal combustion engine, at least for me, and I don't have to mess with all the other 'stuff' that goes with the gas engines. Just depends on what you want to do...
- 'Doc

ernest2

ok thanks!! i guess i'll just use the 540 motor i got here.. i don't really want scale speed because it might be boring, i want the boat to have a scale splashes and wakes.. like in the pictures in the review of chris craft in RCBM.. do you think lead acid will be able to do that with the 540 motor? if yes then i'd go for electric power.. thnks a lot guys!

LtDoc

ernest2,
'Lead acid' batteries shouldn't be used in a model, ever. A sealed 'gel-cell', yes, but an ordinary lead-acid battery, no. The problem is in the fumes that a lead-acid battery produces (as in sulfuric acid), which will destroy a model in 'no time' unless precautions are taken. The precautions are usually more trouble than they are worth, such as using a sealed battery container, venting the fumes overboard, etc. (There's a problem with venting sulfuric acid fumes too. If you 'bubble' sulfuric acid gas through water you make the 'pond' acidic, killing whatever is living in it. That would really 'go over' big, right?) Of course, you could always use one of the 'Optima' type sealed lead acid batteries, the are really fantastic batteries. But, they cost an arm and a leg! The price of an 'Optima' would get you at least a dozen 'gel-cells'.

Electric power is comparatively 'short time' kind'a power, but clean, easy to 'do', and not nearly the hassle that IC power is. You can't run all day on a single battery charge but you have to refuel a 'gas' engine too (swap batteries or take a charger with you). Another 'problem' with 'gas' motors is that you usually don't have a 'reverse'. I'm sure a clutch and transmission are possible, but not too common and much more complex than a reversible ESC ($$$).
- 'Doc

ernest2

ltdoc, what i mean is SEALED LEAD ACID... what is the difference between SEALED LEAD ACID and SEALED GEL CELL? i haven't found a hardware shop here that sells gel cell.. only sealed lead acid.. thanks a lot!!!
ernest

LtDoc

ernest2,
Good question, and I'm not exactly sure how to answer it. Most 'sealed' lead acid batteries (like you find in a car) are not really 'sealed', just harder to get into (you can still add water to them). They 'slosh' when shaken, (not that I recomend shaking a battery!). The 'gel-cells' use a 'thicker' electrolyte, not water. Gel-cells are found in the 'cheaper' computer UPS's if that helps.
- 'Doc

pompebled

About the amps drawn by 500 types motors:

Depending on the load these motors can easily draw 6 Ah, starting up can peak to 20 Ah.

An extreme example is my mono1, powered by a 600 race, driving a 37,5K surfacedrive on 7cells (GP3300), the runtime is just over 8 minutes, making a average of 24 Ah !

Don't underestimate these little Amp eaters, they have poor efficiency, sometimes as low as 65%, combined with the losses on the cables and drive train, they are in fact not the best way to make your boat go.

But hey, there cheap!

That's why manufacturers use them in RTR boats, a halfway decent motor would make the offer less attractive.

Greetings, Jan.