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Well, I can certainly say that higher RPMs can work, when done properly. In some cases, this includes monos, but only when setup very well.
Years ago, I was testing several boats and mistakenly hooked-up two 2s lipos in series vs. parallel. It was an approx. 5000kv motor that was now running on 4s. Now considering an efficiency of 85% and even considering voltage sag, the RPMs were certainly up there. The boat ran great on a very small prop (detongued X632 as I recall) on a 24" mono. I brought it in after one pass since I knew why it picked-up so much speed. Everything survived, but I wouldn't recommend it to anyone. In a similar incident years before, incidentally with the same boat, I accidentally supplied similar kv motor with 12 nimh cells. I lost one of the nimhs in one of the packs. For the record, I haven't done that since. The point is, it can be done, but I doubt that a motor can handle that much for long, especially turning anything but a very small prop. If you are planning to try a setup like this (as in my example), it could be detrimental to everything connected and I wouldn't recommend it.
That all said, many run high RPM setups successfully. It only takes one pass to build-up a substantial amount of heat, so if you try it, it is best to monitor temperatures very closely. Also, be careful not to exceed the manufacturer's recommend wattage and amp ratings unless you are in the habit of buying electronics on the regular basis and don't mind the burnt smell in the boats. There are plenty of ways to do incredible speeds in the FE segment of this hobby. If you find you have the wrong motor for a particular setup, there is a great community here that would be willing to either swap motors with you or purchase your motor on the for sale threads so that you could buy one that is appropriate to your application and goals.
In almost every case, I hesitate to recommend RPM recommendations from an application standpoint unless I have a lot of experience with that particular model and similar setup. As with anything in this hobby, cavitation is a huge problem when you deploy too small of a prop and at the same time, too much diameter or pitch can be too much load. Meanwhile, I have seen some outrageous prop sizes run on old brushed motors, but the modern setups with brushless are far less forgiving.
Unfortunately, on many of my record setups, it just doesn't make sense to run in a few of my test ponds right now because of water temperature. So, for the time being, I'm enjoying my sport setups and building. Luckily, here our ponds don't often freeze. Consequently, I'll end-up testing throughout the winter...with gloves of course!
Years ago, I was testing several boats and mistakenly hooked-up two 2s lipos in series vs. parallel. It was an approx. 5000kv motor that was now running on 4s. Now considering an efficiency of 85% and even considering voltage sag, the RPMs were certainly up there. The boat ran great on a very small prop (detongued X632 as I recall) on a 24" mono. I brought it in after one pass since I knew why it picked-up so much speed. Everything survived, but I wouldn't recommend it to anyone. In a similar incident years before, incidentally with the same boat, I accidentally supplied similar kv motor with 12 nimh cells. I lost one of the nimhs in one of the packs. For the record, I haven't done that since. The point is, it can be done, but I doubt that a motor can handle that much for long, especially turning anything but a very small prop. If you are planning to try a setup like this (as in my example), it could be detrimental to everything connected and I wouldn't recommend it.
That all said, many run high RPM setups successfully. It only takes one pass to build-up a substantial amount of heat, so if you try it, it is best to monitor temperatures very closely. Also, be careful not to exceed the manufacturer's recommend wattage and amp ratings unless you are in the habit of buying electronics on the regular basis and don't mind the burnt smell in the boats. There are plenty of ways to do incredible speeds in the FE segment of this hobby. If you find you have the wrong motor for a particular setup, there is a great community here that would be willing to either swap motors with you or purchase your motor on the for sale threads so that you could buy one that is appropriate to your application and goals.
In almost every case, I hesitate to recommend RPM recommendations from an application standpoint unless I have a lot of experience with that particular model and similar setup. As with anything in this hobby, cavitation is a huge problem when you deploy too small of a prop and at the same time, too much diameter or pitch can be too much load. Meanwhile, I have seen some outrageous prop sizes run on old brushed motors, but the modern setups with brushless are far less forgiving.
Unfortunately, on many of my record setups, it just doesn't make sense to run in a few of my test ponds right now because of water temperature. So, for the time being, I'm enjoying my sport setups and building. Luckily, here our ponds don't often freeze. Consequently, I'll end-up testing throughout the winter...with gloves of course!
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