Thanks for info. I cannot say what size props untill the motors are chosen. I cannot even order the running gear for the Dauntless as Cornwall's are out of stock at present.
That's a bit of an egg-or-chicken situation.
Motor choice depends on the props: ie getting the right RPM (power probably won't be much on an issue; BLDC motors exist in various sizes).
I guess
the Prop Shop's General Purpose props could do the job. Maybe a pair of 4514 (45mm x 63mm) props would do the job. Though I don't know how/whether they would fit on the Dumas shaft if you go that way.
There are a few Dauntless topics on RCgroups but not much info on the props used.
If we do some basic calculation for one of these props: RPM * pitch * slip rate = speed
Pitch is 63mm
Slip rate on a planing hull: let's assume 20% (maybe less)
From what I read these commuter boards were apparently capable of doing 35-40kt!
As the Dauntless is 1:16, scale top speed would be around 19kph.
Let's do some basic calculation:
19*1000 (speed in meters per hour) / 60 (60 minutes per hour) / 0.8 (20% slip rate) / 0.063 (prop pitch in meters) = 6283 (shaft RPM)
With 3 cells LiPo batteries (11.1V) here are a few options:
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Turnigy Aerodrive SK3 - 4240-620kv-
Turnigy Aerodrive SK3 - 3548-700kvI don't think either motor would require cooling. Car ESCs wouldn't require cooling (you may keep their little supplied fans though to be safe).
But as you can see on the Prop Shop's site, prop pitch can vary greatly between props and hence the motor speed.