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I'm new to scale warships and I'm wondering about just what should be good for power. I 'm building the deans marine narvik class destroyer. It's 52" long with a 5" beam. I'm sure this hull should move very easy through the water. Loyalhanna sells their #1 motor which is 1.5" long and 1.1" diamater. I'm just guessing but it sounds like that may be equal to about a 280. The destroyer is a twin screw. Are a pair of these motors good propulsion for a boat like this? Any input would be greatly appreciated.

thanks to all
Tim

LtDoc

x-craft,
I would guess that it depends on just how 'scale' you want to make it. I'm not familiar with the motor you described but a pair of them ought to produce at least scale speed. If you can keep your 'foot off the throttle', maybe a pair of 380's?
- 'Doc

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Thanks doc, I do want scale like speed. A destroyer on plane just doesn't seem right but I don't want it underpowered either. I plan to make a removable adjustable mount for the motors so if necessary I can put in a couple bigger motors easily. I'm going with direct drive, gearing just seems like a waste and I dont want the howl of gears. any comments about that?

Thanks again
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LtDoc

x-craft,
About gearing. There are some cases where the noise of a geared drive system make the model more realistic. Some destroyers had turbine engines so the 'gear noise' might even be 'better'.
If you do use a geared system, use the 'plastic' geared type. They're a little quieter (sort of) and can cause much less RF interference compared to metal gears. A belt drive is also an option! (The problem is ~finding~ them!)
Geared systems are handy in that they allow you to use a motor that's way too fast (RPM) for the model. They don't really 'waste' power, they do give you the ability to use a coarser pitched prop to get more 'usable' power (usable torque vs. high RPM). Motors use 'less' power when running at their 'design' speed than if 'lugged' down to a low speed. There are losses due to friction, but compared to the watts consumed, that friction isn't really significant. It also means a geared motor will usually run longer for a given battery size than an un-geared motor (not in all cases, but usually). It has to do with the efficiency of the 'system'. (Just like a lower gear in a car with a motor that has maximum torque at higher rpm's. Not much speed, but lots of power, right?) Don't expect miracles, though (LOL)!
I have a freighter (about 36"?) using a geared motor and it will get up on a 'plane' if it isn't ballasted correctly (Graupner gear drive, a '380' size motor, if I'm not mistaken). It has lots more power than required, just from that 'dinky' looking motor, and powered from a 6 volt gell-cell so run time is in hours, not minutes. To keep it 'scale', I have to use the speed trim control instead of the 'stick'... 'cept when I give the ducks @#$%...
- 'Doc

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ok, if you were building what I'm building what would you use? Deans says to be very careful about over powering this hull as it will snap capsize.

Tachikaze

I would not gear your drive system in this boat. We have several of these in our 1/72nd combat club with direct drive motors. Several members many years ago did the math to work out "scale" speed for our club. The German Z-Boat of the 36A Mod Class ( Narvik) we run at 38K which in our club is 32sec for 100 ft. This looks fine for a boat that size. It would make your smaller boat look even faster, but not out of the scope of appearance.
We are running inexpensive motors that under no load turn about 4500 RPMs. The motors that are going into my HIJMS Shimakze are a Johnson 12V motor that came off of All Electronics
[link]http://www.allelectronics.com[/link]
Look under the DC motor section under Motors. A recommendation would be #DCM-216 which is very similar to what we use. We look for a small amp draw, no load of say 300mAmp what is very popular for us are these 24V Pittman motors that run at 12000RPM that we run on 12V. These work very well for a ship the size of what you are looking at building. They have the RPM's to move your boat at a good looking speed, but not the torque to pull the motor out of the boat. If you can obtain them, those little black case, red topped Maxon motors are also great. They make a silver cannistored unit also that are also great for that size of motor.
E Bay items like this is good choices also: 3185437166

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ok, thanks for the advice. I now know where I'm going with the drives on this. I'm guessing that with these little tiny motors most speed controls should be able to handle it I would think. Do you have any recommendations regarding that?

Tachikaze

Because these low amp motors draw far less than the 550 car motors we have been running two of these in parellel.
I have an MCD micro in one 56" destroyer.[link]http://www.modelcontrol.com/sminicon.htm[/link] and this has functioned flawlessly for me.
The Japanese 56" destroyer is running a Tekin Rebel with two motors in Parellel. I found that speed control on ebay for about $30.
The Japanese 70" destroyer that I am now building will run two 550 like ( but much less am draw, measured at 300mAmp no load) in parellel using a new Mtroniks [link]http://www.mtroniks.net/[/link] The sonik4 Marine 15. Very nice looking unit that should work for this size of boat. I do not have any experience with these though. The above units have worked out fine. We are also running Vantac ESC for a lot of guys in the club.

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Excellent, thanks for the advice, it sounds like I can use just about anything which was something that I had already suspected since the motors are so small and low amp draw. Your input is greatly appreciated.

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LtDoc

x-craft,
The 'best' advice I can give (since I haven't any experience with your particular model) is to stay fairly 'close' to what the manufacturer recommends. Too much motor can cause more problems than having a too small motor, it depends on how ~you~ run the thing. Large motors can make a model very 'touchy' in controling it...
- 'Doc

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this is a english kit and their recommendations are totally greek to me. Stuff I have never heard of. What I picked up are equal to speed 400's. Low amp draw and I can keep my foot out of it if they are to much power. Their 6-12v motors so I'm going to start with a 7.2v pack and see what happens and then go from there. I'm going to get the stuffing boxes installed today and motors mounted. Thanks for your advice. I'm planning on starting a building thread and posting pics.

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