Soaring Steve

Good morning everyone. I hope this is the right forum for this.

I have been building RC Aircraft (nitro) for over 40 years. I know absolutley nothing about rc boats or electric power, so I am giving myself a crash course on the subject.

I inherited 2 Midwest boats from my father after he passed in 2006. Over the years they have been sitting around my garage collecting dust, but now since my son has moved to a lake front property, its time to get them going. One is the Midwest Harbor Tug and the other is the Midwest Fireboat. Both are in good condition and just need final finishing and detailing.

The first one I am overhauling is the fireboat. The first question I have is the standard MEPS motor any good? Should I upgrade it? If so, to what? I plan on removing the mechanical controls and using a ESC with BEC with the existing motor. What ESC is a good economical one? Also, Ive attached a pic of another MW Fireboat with question about some fittings on this.

mfr02

I am not familiar with a MEPS motor, but assume that it is a fairly normal permanent magnet motor, probably appropriate to that size and shape of hull. Again, assuming just two wires. It needs to be checked out and tested to determine its current requirements under load, an amp meter is good between motor and battery (no ESC needed yet). Once you know its amp draw, you double that and go for the next ESC up in the range. Unlike mechanical types, ESCs don't need to be closely matched, one that will handle a high current motor will control a low current motor just as well. Their only downside is that because of the way that they do their control, the attached motor tends to whistle. Some people get deeply annoyed by this, others appreciate that this is a sign that things are working, some ignore it,
Then you order your Mtronics Marine Viper 15 (probably). Not the cheapest in the world, but reasonably bulletproof and sure to work. (Since you only need to buy it once, this cuts the cost over types that need to be replaced and thus becomes economcal).

Soaring Steve

Thanks for the information. I have ordered an ESC from Mack Products for this. I think for now that I will try the existing motor, and if its underpowered then I will upgrade.
Currently I have now sanded out all the garage rash and have it looking quite smooth. Its all in primer now. I plan on puttig lights on it as well.

I have had my son 3d print a lot of accessories for it. Im excited about getting this into he water. I hope to have a coat of paint on her this weekend.

Soaring Steve

Another question. When I see "not LIPO safe", why not? I mean 7.2V DC is 7.2V dc no matter what the source, correct? What am I missing?

mfr02

If you over discharge a LiPo, you have, if you are lucky, a dead, unuseable LiPo that you will have to pay to replace. If your luck is not good, you have a boat giving itself a viking funeral.
Some ESCs have a safety feature that cuts performance down to a "limp home" mode shortly before over discharging happens.. A alternative is to fit a warning circuit that bleats at you when full discharge is imminent. Having neither is very much "LiPo unsafe".
And, of course, the 7.2 volts, when sourced from a 2S LiPo, is 7.4 volts. A LiPo of similar size will store more energy than a NiMH, and will support a higher discharge current. This means that the chemistry going on inside it is much more lively. When it is over-done, it kills the battery.

Soaring Steve

I have been out of town for a while, so my progress isnt as far as I had hoped for. Ive added some color, painted the interior, fitted stack, radar hand rails etc. I hope to get some color on it this weekend. One issue Ive noted is that my father did not seal the inside of this boat. as the aft and forward bulkheads are solid, I can only get so much of it sealed. What is a good sealer? Poly, epoxy, or just clear enamel?

Soaring Steve

Ive been off for a while and havent been able to get much done on this boat, but as parts come in I am getting the electronics fitted and have started building the brass railing, something I have never done before. I think its coming out pretty nice!

Soaring Steve

So now I have paint on it and started the detailing. Ive installed the brass railing and starting to put the finishing touches on it!

Soaring Steve

I have been slowly working on getting all the electronics and wiring run and its looking pretty good. The LEDs are mostly working, the rudder, prop and rudder tiller are all installed and shes nearly ready for a test run.

Soaring Steve

Slowly making progress. Lights all working, Electrical installed. Almost ready for a test run.

Soaring Steve

So I have finally moved and found a few minutes to get the boat out for its maiden voyage in the pool! One think Ive found is that the 550 motor is too much for this boat, as it seems to have a bit of torque roll and will dip the starboard rail into the water when you really nail it. If you slowly roll on the throttle it realy gets up and goes. so much so that I think it may need ballast in the bow to keep it lower in the water, but IM not sure how to get more weight in there as its all sealed up. However when just putting around its looks and runs pretty good. Looks super at night with all the lights on and the fire monitors will squirt around 15-20 feet. Its a pretty fun boat! I still need to finish some details, but it is working and pretty fun!

Hydro Junkie

I have a couple of thoughts for you:
1) Smaller battery pack(s). That would lower the power you're putting to the motor and will reduce your rolling issue
2) Add some expo into the throttle, will do the same thing.
3) Smaller motor, though to do so will mean probably having to replace the prop with something of either less pitch or diameter to keep from overloading it

I personally would start out with option 1 as it will also reduce the brightness of the lighting. To me, the picture has them looking too bright

Soaring Steve

Thanks Hydro. I have only just runit a bit as a test. There is still much to do and adjustments to make. I may add a resistor before the PC board I made to dim the lights a bit. I bought a Flysky 3 radio, which is lame on instructions, so Ill have to play with it a bit. Im sure it will do expo trimming. The prop I used was the one that came with the kit, the plastic Midwest one. Im not sure what pitch it is, but it measures 1.6" in Dia. Ive looked into a different prop, but not sure if I want a 3 blade, 4 blade, what pitch etc.. I can get a max 2", which I think may be way too big..