6ft Fast Electric Mono

Low Power Planing

Some rough numbers might help you.

The best lift to drag ratio for a planing surface is around 8. Your 290lb boat will require a thrust of at least 36lbf to plane if it is a good planing surface. Your target speed of 16mph or 23ft/sec will require 828ftlbf/sec or 1.5HP.

Surface props have very low efficiency at low power levels and low speed. You could maybe get 50%. (My experience indicates their efficiency is lower than this at low power) So the required shaft power is at least 3HP.

A short hull will nose up before it gets on the plane so the lift to drag ratio will be less than 8 meaning you will have more drag to get it on the plane and possibly more power depending on the size of the planing surface. You may be able to use trim tabs to improve the situation.

With such low power level you could make a high aspect submerged prop that would have an efficiency around 88%. This would give you a better chance of getting it up but without all the wasted energy in producing the rooster tail.

Some years ago I built a 6ft long by 3 foot wide boat that had total weight around 250lb. It had a "V" hull with small planing strakes and would plane with a 6HP outboard providing I moved my weight forward to get it on the plane. It would do about 20mph once up on the plane. I have seen 3.5HP outboards get children on the plane.

Rick W.

 

Hey guys well time has passed and so has many new changes in what one can buy or make to produce a fast electric small mono. With the gas prices they way they are this trend to electric and going green for local lakes n small water ways is also a plus... Rick and others ty for your adivce Rick your spot on and really in tune with what I want to do. Thank you very good info!!!!
Since my postings I have been working on some motor designs.. My latest uses large 2in dia N42 magnets with a pancake type motor. Since then there are very large outrunner motors on the market now too ..brushless is the only way to go to get the most power and run time out of your system. Outrunners have the most torque so very important with the aplications in this forum. Im going to post a few pics the motor is a new china motor puts out 10hp amazing for its size but thats brushless for ya. I have a smaller version of this one rated for 2hp I was going to buy two more for a 6hp motor since then started on the larger pancake 20hp motor. I found a prop maker who will CNC me a surface prop from steel im shooting for 4k unloaded in the water with a 6pitch 6.5 dia 3 bladed prop. The hual will be 4x7 im shooting for 25 to 30mph. I want the rooster tail for effect and surface drive if set up right will get me going faster. I have alot of time on the water with surface drive setups already and know proper placement and prop type. Should be a blast to have a smaller electric 1 man electric the novelty alone will draw a few ohhs n awes providing I can get 25mph or better. There will be no gearing direct drive max torque out of the hole electrics can produce tremendous ft pounds of torque I will be at speed in a blink of an eye seemingly fooling myself of greater speed and visualy for onlookers too. check out this motor for 200.00 bucks vah vahh voom two of these would keep things light and very fast 60KV per volt I want to run 72V 200amps 14.4KW 19.5Hp The shaft on this motor is 15mm Last pic is of one of the rare earth mags im using in a pancake motor 240pouds of pull force per mag..one must be very careful when handleing these.. about $6.91 per mag when bought in bulks of 25 units my son is making a motor too 9arm 10 mag motor wound in Wye with 14gauge wire. about 2hp per mag rule of thumb. Will post more info as the project proceeds. For the rest of you electric users good luck and way to go change the future of boating.

 

Here is a pic of three props made with the CNC machine. Im going with the one on the left scaled up to 6x6.5 with a 3/4 ID hub.

 

Where can you buy that motor you have listed? The other motors in the picture look like AXI's, so does the big one a little bit, except for it's huge compared to the other ones. I need a motor like that Are you building the motors yourself? You mention buying it from china then building motors so I wasn't clear.

Machining props has got to be a bit pricey. I used these "mixing propellers" from mcmaster.com (search for 8004K161 or just search for mixing propellers) Although I don't claim to be a propeller design master, they seem alright to me though.

Look forward to hearing more.

Ross

 

Its a monster!
The largest motor we have ever had!

Model: HXT80-100-B
Wire Turns: 8
Resistance: 32ohm
Idle Current: 2A
ESC Required: 130A
Input Voltage : max. 48V
Kv : 130 rpm/V
Weight: 1570g
Shaft: 12mm
Voltage Range: 20-48v
Non Load Current: 2.0A
Maximum Power: 6500W
Equivalent: 60-80cc Gas Engine
http://www.hobbycity.com/hobbycity/...80-100-B_130Kv_Brushless_Outrunner_(eq:_70-55)

 

A 6 foot boat will not get out of the water......you have less than 3 hp available!

 

I tuned up my 3.5 hp Tohatsu on a 10 feet allow boat, it could plane quite easily, but 6 foot....nup.

 

That one is the smaller version the other pulls 200amps plus I cant find my link on the other one at the moment arggg. 6500W thats good for 8.7hp for this smaller one. Yes the magnet I showed is for my own motor build im going to use 10 of them with 9poles terminated in wye I hope to get 20hp. The CNC machined props your seeing are $38.00US each.. my custom order will be lil over $100. I want a pure surface diven prop for maximum top end on 20hp. Unloaded at full speed my amps will drop down under what it takes to run at 75% throttle given there will always be a blade out of the water. I saw the props your talking about. I would completely rework those props the steel ones could be sharpend cupped. I would detongue the leading edge and rake the back and put a texas cut on the tips with a nice flat edge on the rake. This would decrease load increase rpm and give you more speed if you modified a larger prop then you are currently using in essence the over all blade area would be closer to the same but with higer pitch and a much more agressive design that puts out more at the same amps. I have reworked alot of props in my day. I would also put a bar cut in to reduce amps and allow more pitch.

 

Hi Landlubber I agree . I have changed to a 8ft hual on 20hp now this post is over 500days old times have changed on my options and whats out there for parts.

 

I have been doing some doodles and liked this design here is a redering of the basic look 4.5 x 8ft mono two seater side by side. 3.5ft wide bench 42in or
21in per person. Im looking for some Cobalt Iron plate for the pancake motor now. It will be the back iron for the magnet aray.

 

Fantastic! AMP User

Hi AMP,

I was led to your web blogs thru several links and read with great interest all of your fantastic contributions to the electric boat discussions.

I'm planning to make a 10 ft electric boat and don't need high speed, just 6 mph. You mentioned the $200 motor and I also saw that you make your own propellers. I was wondering whether your motor and prop are available for me to purchase please?

Best regards, Merlin

AMP WROTE: Since my postings I have been working on some motor designs.. My latest uses large 2in dia N42 magnets with a pancake type motor. Since then there are very large outrunner motors on the market now too ..brushless is the only way to go to get the most power and run time out of your system. Outrunners have the most torque so very important with the aplications in this forum. Im going to post a few pics the motor is a new china motor puts out 10hp amazing for its size but thats brushless for ya. I have a smaller version of this one rated for 2hp I was going to buy two more for a 6hp motor since then started on the larger pancake 20hp motor. I found a prop maker who will CNC me a surface prop from steel im shooting for 4k unloaded in the water with a 6pitch 6.5 dia 3 bladed prop. The hual will be 4x7 im shooting for 25 to 30mph. I want the rooster tail for effect and surface drive if set up right will get me going faster. I have alot of time on the water with surface drive setups already and know proper placement and prop type. Should be a blast to have a smaller electric 1 man electric the novelty alone will draw a few ohhs n awes providing I can get 25mph or better. There will be no gearing direct drive max torque out of the hole electrics can produce tremendous ft pounds of torque I will be at speed in a blink of an eye seemingly fooling myself of greater speed and visualy for onlookers too. check out this motor for 200.00 bucks vah vahh voom two of these would keep things light and very fast 60KV per volt I want to run 72V 200amps 14.4KW 19.5Hp The shaft on this motor is 15mm Last pic is of one of the rare earth mags im using in a pancake motor 240pouds of pull force per mag..one must be very careful when handleing these.. about $6.91 per mag when bought in bulks of 25 units my son is making a motor too 9arm 10 mag motor wound in Wye with 14gauge wire. about 2hp per mag rule of thumb. Will post more info as the project proceeds. For the rest of you electric users good luck and way to go change the future of boating. [/QUOTE]

 

For your shaft bearings take a look at our XPC Bearings at http://www.xpcbearings.com/ Our Hilube Vesconite bearing has very low cofficient of friction (.09) These bearings run very smooth and do not swell in water. We also produce dripless shaft seals (stuffing box) that are very light weight and non conductive. If i can be of assistance please let me know.

 

Thank you for your support, and the bearing tip. I have been educating myself on the task at hand. And have enjoyed my findings, I would like to share some..

The bottom hual is mono hual in the front and a hydro ish.. tail. Supported lift for the prop and has enough sideboard.. so to speak to aid in turns as the front end will want to bank in the turns. To control some of the bank, I would have to have a wider foot print in the turns.

The prop is a simple design, one I would like to try as I will need to mod the pitch and dia as I go into testing. This form of prop could be made out of large steel spoons.. and some hub material. If you notice the right blade shows a simple half spoon design. This gives a long fade back on the leading edge, alot of grip which transfers to thrust with a sharp edge. Notice we have a cupping effect already built in. I dont think this prop would work well for lifting the back end of a hydro at first glace you see alot of slip off the trailing edge. Which doesnt help lift the rear up.. but the broad scooping effect of the blade as the hydro effects form from the spinning blades would suggest this long area of control on the front face of the right prop show promise. I like the two point hual it has the legs for a stable ride of a boat its length minus the extra weight. The blue shows the wet areas on each hual, the prop needs to focus on providing thrust rather then lift in my case. Another thing about this prop if you wanted to add rake there should be all you need built in already by nature of the spoon shape. Rake of course helps focus that thrust cone back. I will add one more pic a of the prop with a mod.
This looks more familar...and a fast way to unload the prop and show why this prop makes lift... just doesnt have a abrupt ramping trailing edge rather a longer hand in the water to ride up, adding some lift.

 

Here is a great example of the use of pan cake type motor frames that allow these sort of ironless stator cores you can produce with minimum effort. The value is aparent in the large aray of pure torquelicousness. The neat and well used trick here is the magnet fields overlap and max out copper fill. 0 eddie current effects with ironless cores; and weight / cost savings. To be fair back iron for the coils would increase the motors performance. Soon as I can im going to do coils of this nature for my 2in dia magnets, shown further back in the thread.

 

Can this propeller regenerate as well when sailing ?