I've never done marine RC before although I've been doing most other forms of RC (i.e. land and air) for about twenty years. I've not done 'proper' electric before, I've played almost exclusively with IC. I have a long history of micro-electronics so the electronics side isn't a problem. I figured I'd start with a relatively cheap kit as if I then screw it up I haven't lost much. I've also little interest in accurate scale representation although I'd like it to look reasonable when complete.
Because of my motivations for building a boat I figured I'd go adventurous. I've built a triple-screw setup with three ESCs, differential drive and separate rudder control.
I'm still only part way through the build, I've done a few bathtub tests and sealed holes where I found them and today took it out for its maiden open-water voyage.
I've discovered something distressing...
I don't believe my battery setup can dump enough current into the stock (i.e. cheap) 550 can motors to drive the three-bladed semi-scale brass props. With one fully charged 7.2v pack I get about 2 seconds semi-planing before it slowly crawls back to me. With three 7.2v packs in parallel (one per ESC) it lasts marginally longer (maybe 10 seconds) with the bow coming out of the water but still it's all but dead after 30 seconds on the water.
I think it's probably the batteries, I don't know the current demands of stock 550 motors but I suspect they're pretty high. If it's 10A a pop then 30A is a lot for a 7.2v NiMH to provide. I also don't know how good condition these packs are in, they've been in the garage for a few years and despite being high tech at the time (3600mAh) I doubt they're as capacious as they used to be.
Other options that come to mind are overheating somewhere, maybe in the wiring. I don't think that's happening but it seems plausible.
So, onto the questions, if you have the time and inclination to answer them...
1) Are 3 x cheap 550 can motors capable of getting the boat up onto the plane? Their performance in the bathtub is impressive, giving huge swells at either end of the bath. If not what's the most cost effective way of getting this result? I don't want to spend the cash on a racing setup, just a modicum of performance to earn the title 'Fast' Patrol Boat in preference to 'Mediocre' Patrol Boat.
2) What battery setup do people use for high-current demands? I don't want to go LiPo unless I really have to due to the high costs of every aspect of this power setup.
3) Do you have any other ideas of what could be causing these symptoms?
Thank you all in advance :)