Will a Magnetic Mayhem push a 4 lb crusier?

[Kez]

I am scratch building a cabin cruiser from a plan. The boat is 35" in length, 11" beam and a pretty tall freeboard. With all the superstructure, the empty wt is about 3.5 lb before fihnishing.

I would like the boat to have reasonable speed and all my battery packs are 6-cell. Would a MM motor on 6 cell push this thing? What is a good prop to try? I also have a Kysho gearbox that I can vary the ratio between 1.4 to 1.9. Would a gear drive better choice?

Thanks,

Kez

 

[Dennis Whitt]

A Mayhem wouldnt be my first choice but if it was what I had laying on the bench I would definatly gear it with atleast a1.9 gratio and maybe a graupner three blade scale prop should give you EZ running at scale speeds.

 

[Climate Boatworks]

Dennis is right on!

A better choice for a motor would be something with some good torque like a 600 or 700 Graupner style.

A large hulled boat like yours will require some hosepower to get up and out of the water.

While direct drive is nice and simple, you will quickly burn that MM out with anything but the smallest of props. An x432 would be about as high as I would go without gears.

A good gearbox will let you drive a much larger prop at a more reasonable RPM for that type of hull.

 

[eddieh]

Kez, I go along with the peter's and dennis advice, but I would even go a little steeper on the gears, think about using the airplane tranny from great planes it's like 2.5 to 1 and then a 440, I have an old sterling chris craft 63' motor yacht, I run 2 graupner 600's 3 to 1 tranny's and counter rotating 955 3 blades, and it really moves, planes down till the last three portholes LOL, my uncle also runs a chris craft cabim cruiser, with a 600 and a 3 to 1 he is running a 445, and the boat runs fine, motor doesn't even get warm,, my 2 cents

 

[eddieh]

kez, thought i'd post a pic, this boat is over 5 pounds

 

[Kez]

Thanks everyone for your input. My experience in electric is limited to airplane. I thought the MM was a pretty torky motor but apparently not. Does a Graupner speed 600 motor produce more torque (or power) than a MM?

I have a Master Airscrew 3:1 gearbox that I will use with a MM reverse timed. According to your experience, that should be a good match with a 445 on 6 cell, right? Also, will a Castle Creation Pegasus ESC be suitable? Finally, who makes a universal joint that couples a 3/16 shaft to 3/16 shaft?

Hey Eddieh, that is a nice looking cruiser. Can you tell me more about the boat and set up? Although most of my fleet are glow, I do enjoy a nicely finished electric cruiser. Actually they are very useful as a rescue boat, too.

Kez

 

[Andrewg]

The Magnetic Mayhem is a long can 500 motor often known as 550 or 600.

It comes in anticlockwise (normal and reversed rotatio. It is timed about 15 degree and is 22 turn motor if memory serves me correctl.

It 's stated Kv is the same as a 600 BB 8.4v ie but is mre like 2600rpm/v in practice. The motor is somewhat heavier than the 600 due to a thicker can. With better magnets and can the Mayhem generate good torque.

The 3:1 box will be needed but you may be able to prop down somewhat - the larger X series props are running into serious innefficiencies in the blade shape and cross section fo submerged operation

Raboesch scale props are the best I have found to date

They are much better and span the prop shapes and style form 1890's to present. WIth low pitch, low vibe, high efficiency props which really do make a difference to run times.

I am talking a 20% difference in some of the testing I am doing - I am pushing a 52lb boat with a 60mm prop

I would tend to run a 40mm 4 blader - a little less diameter nade up for with a ho torque balde shape and more blades or go to 4 ona 4 blade low vibe prop for some longer runtimes

the drawback is you need a shaft with a 4mm thread

Andrew Gilchrist

fastelectrics.com

 

[eddieh]

Great info andrew do you have any of these props on your website??and are they bronze? metal, or composite? BTW the 9 series prop (not the v9) are really scale looking propellers, I have had good results with the 937/3 and the 955/3 thanx in advance

 

[Andrewg]

Eddie

I dont have them on the site

Raboesch has a site www.raboesch.com

 

[Kez]

I picked up this motor from a surplus store. It has a 1/4" shaft and looks like a desent motor with replacable brushes. Next to it is the Mayhem I planned on using along with the gearbox. Would this motor be a better choice? I will try to post my unfinished crusier in the next post.

 

[Andrewg]

that will depend entirely on the specs of each of the motors