hey guys, I'm building an rc ship for an event to be held in 20 days. The ship has been constructed but me and my team need help regarding propellers and the electronics involved. The model we made is a SWATH similar to the 'Sea Shadow'. Please let me know if anyone can provide help and I will post pictures and other details. Thanks!
I don't need electronic parts I just need help with what type of propellers to use and how to select suitable electronics so that it will run for long periods without heating up.
it'd be hard to suggest anything given that we know nothing about what is available to you, how fast you want to go, how long 'long periods' are, the limit on temperature you seem to be operating under, any details on the ship etc.
I've added some pictures of our ship. The length is 65 width 50 and height 35. weight without equipment is 7kg. the structures in the bottom are pvc pipes. We planned on placing 4 motors on the front and back of these pipes. Battery used is a 12V battery. We have 4 motors for the propellers each of 4000 rpm and torque around 1kg. Right now we have 3 types of propellers with us, CPU fans and 2 which are used in quadcopters but we have no idea if these will work. The large one is 10cm diameter and small one is 6cm radius(pics attached). We plan to buy new propellers if these don't work but we are on a limited budget so we may be buying plastic propellers or maybe try to make propellers by hand. Also we need to turn the propellers on and off to control speed and change direction so do you have any suggestions on that as well. We are also trying out a water jet propulsion system if propellers aren't good enough.
All of the propellers you have posted are designed to efficiently push air. While they will *function* in water, they will be horribly inefficient and will provide poor speed/thrust for their power requirements. A decent set of propellers is not terribly expensive. You can get a pair of props at Battler's Connection for around $20. An Electronic Speed Control will cost you around $20-$50, or you can rig up a MAG-style speed controller using a pair of micro-switches and a small servo. Since I don't see any rudders on your boat, I presume you'll be using differential steering, so you'll actually need two separate speed controllers, one for the port motors and one for the starboard motors. If you want to make your own prop and speed controller, you can find details in the following build thread: https://rcwarshipcombat.com/threads/sb-101-building-mn-edgar-quinet.441667/ For professionally made props and ESCs,
There are no shops selling boat propellors where we live and online delivery takes too long so our only options now are to try and make propellors or try a water jet propulsion system. Also is there any way to have steering by differential propulsion if we only have servos?( esc isn't available to us at the moment and we only have servos) .What if we have a system where we run propellors either in reverse or forward or turn them off and no speeds in between.
Joel, On the props, in your position, I would cut down two of those three blade aero props to maybe one third larger diameter than your drive motors. Test a motor and prop combination in a bucket of water to make sure your motors are not getting to hot. If they get to hot, cut the props down a little bit. On the motor controller's, yes you can use servo's and micro switches to control them. Review the write up on the MAG throttle on the following link. You will need two R/C channels and servos for your setup. If you want one stick differential steering using only servos, scroll down further and look at the Tri-Pact controller. http://www.rctankcombat.com/articles/speed-control/ Hope this helps.