I have done a bit more thinking on this one and have come up with an interesting idea.
My ~34"cat has about 1600W of calculated power and run well.
My ~25" cat ( now dead) had about 1000W of calculated power and was very fast.
I see a pattern here
About 70% hull size reduction runs on about 70% of the power, so far so good.
One new hull i plan on build will be 18"(wet) 20"loa and most of my reading points to about 750W power setups. This is where the light bulb came on.
The smallest cat on the paper at the moment will have aboat 13"wet and 14"+ loa. This should then get by with about 250W of power.
I did a few paper cutouts and have shown my "formula" to be based on plan view sizes. Given that my cats are close to the same design and proportional build construction I now see this as a power to size ratio.
Now all I need to do is suit up about 250W of power to feed to a 27mm Graupner prop.
I plan to use the Graupner 2318 series M4 threaded props until I find the right size and then if needed go to a metal one.
Possible power combo#1
20x40mm (130L) 4850kv Inrunner max load 25A?? (185W) Add more for short sprints with cooling !!
40A esc
1600 30-40C (48-64A) 2S1P pack
Possible power combo#2
24x35mm (370s) 4400kv Inrunner Max load 26A (192W)
Same pack, and esc.
Last resort is to go with a 380S.
I am leaning toward the smaller motors as that seems to be a fairly successful size to transplant into the Pro-Boat Mini-C and I have seen a few clips of them going nuts on small setups.
This is deffo a fun boat, not a saw or racer.
I am enjoying the research and thought that all of this takes.
See it....find the photos.....sketch it it....build it........with wood
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