 smudge wrote:I guess the best aspect of electric boat motors are that it is a reasonably constant load. With a near flat torque curve an electric motor really suits a boat. The reason I go for the hybrid option is it is easy to jump start a petrol engine |
funandfunction wrote:
The load on any boat motor varies exponentially with the rpm of the propellor so definitely not constant or near constant unless you mean when you drive everywhere at one speed. |
| Steps wrote: We will put some of that theory, smudge, into some real numbers then. Lets take an ave 6m planing hull Say ball park gross weight on water 1800/2000kg.. say 1900kg Co efficient around the 195/ 205 mark.. say 200 Cruise 28/30 mpg well non bar powered.. say 29 mph That works out to around 90 hp at the prop. Now you can convert that into KW then Kw/H and battery storage, keeping in mind batteries are not able to maintain power to flat or min storage maintained by maintenance systems. Lets not also forget this doesnt include the hp required to get over the bow wave, reserve power to power thru small chop at cruise speed...this is just flat water... nor does it include lights, sounders etc. Nor does it take into account a full fish bin(s) and/or a game fish on board or being towed home. Then throw in trolling or just going thru restricted areas say between ramp and open water, on a planing hull used inefficiently as a displacement or semi displacement. (an area I have only basic and at most 'concept' knowledge) |
| smudge wrote: Just to further get us off track on Bazza's post. An old slow displacement hull may suit future electric power? Steps' next door neighbours dad has a displacement hull. I think it has 40hp pushing it along at 8 knots. Just done his 1000th Manukau bar crossing on it. Would that be a more constant load than sa is that a planing hull? I'd expect so, maybe they would suit electric I don't know but I can't see that style of boat becoming too popular.It's hardly a market that is going to give lots of savings either. |
| Steps wrote: So what were the real numbers? Clearly the bigger the load the more
power requirements are. I don't deny that. They were just my thoughts. I
didn't realise I was matching wits against Sir Isaac Newton. No .. You are the electrician. going from hp to kw and kw hrs etc and the draw on batteries etc.. Thats your dept .. not matching wits at all The newton /crouch stuff is mine |
| Steps wrote: All I did was work out the min hp requirements for a petrol outboard along the linesof the previous posts chatting. As it electrics under discussion and be it petrol , hamsters in a wheel , or electric in this case, and you being the electrician here, you could convert that hp and time and required battery storage into electrical requirements.. Nothing else. So rather than go all nancy, why not just do the conversions and lets see if substantiate the comments in previous posts. and leave the bs behind... |
| Turnright wrote: About bloody time smudge, are you sure a week is long enough for steps holiday???? |
| Bounty Hunter wrote: how many regular contributors has Steps driven away from these forums do you think |
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