Update on: Will a Magnetic Mayhem push a 4lb crusier?

[Kez]

Hi All,

I have posted this thread a few months ago:

"]http://www.intlwaters.com/yabbse/index.php...1680

I ended up using the MM with a Master Airscrew 3:1 gearbox. Six 2000mAhr cells and a Kontronics Sun 4001 powered the craft. I tried 1240, 1245, 1440 and X445 and am disappointed at the performance. This will double as a rescue boat but I still like to have a descent planning speed.

I am thinking of going to 12-cell. Any suggestions?

Attached is a picture.

Thanks,

Kez

 

[Climate Boatworks]

If you put any more than 8 cells on that MM, the only thing you are going to see is smoke!

Even 8 cells is pushing it. 7 is about max.

Get a larger more powerfull motor.

A 700 will work great and can run on up to 14 cells with no problem.

The boat looks great by the way.

Peter

www.climatemodels.com

 

[Andrewg]

I believe that is a model of the Fairey Hunstman or a similar ChrisCraft hull

That said I am afraid you are going to have great difficulty getting that hull to plane - because it is a semi-planing hull which ran at 36mph peak speed. This equates to a scale speed around 11 mph for that hull

As a semiplaning hull these hulls run very wet.

The original boat had twin 3-blade props.

The closest prop for that is a 50mm diam 1.3 pitch ratio threeblader with a shaft output of 8000 rpm. Try Propshop scale props or the octura X450/3 (withthe octura you will need to reshape the baldes.

for the MM on 3:1 you need 8 cells. It will be fine as the current draw is very low - approx 12-15 amps.

To prepare the motor - cut the comm and replace the stock brushes with 6 or 9% silver brushes and red springs (11oz) - watercool the motor brushhoods and can. There are probably better motors in terms of motor wear.

Andrew Gilchrist

www.fastelectrics.com :

 

[sjslhill]

Looks like a great application for a Hughey gear drive Andrew.

 

[Kez]

Thank you guys for stopping by with your inputs. I scratch built this boat from a plan. It is a Bristish design named Sea Commander kitted by Aerokits in the 60's. In fact that was the very first glow power boat I built in 1970. Back then R/C gear were very expensive and the Futaba servos had 4 wires. I set the rudder to let the boat run in circles.

The boat did plane then as it does now but the speed on glow power was good enough as a crusier. As it is on the mentioned set up, it barely gets up on plane on a fresh pack and it runs perhaps 10-15mph.

Since I already have the MA 3:1, I think the easiest to try would be to use X450/3 as Andrew suggested.

Peter, I have a 700. Would you suggest direct? and what prop?

Regards,

Kez

 

[Andrewg]

The kits will be available again soon from Jotika in the UK

When u say it planes - how is the motor heat - that will determine whether u go up in prop size. U did say you were using 6 cells didnt you? If so simply try 7 or 8 before you give up the reduction shoudl let u carry a big prop at 8000 rpm

For the 700 one of the slower ones such as the 9.6 will be ok with 37mm prop; for the 8.4 look at a X435 -y536 on 12 cells

 

[Kez]

Andrew,

All my battery packs are 6-cell. That's why I was asking if it is possible to try 12-cell by putting two packs in series. Knowing the result will be smoke coming out of the MM, I will not attempt.

Neither the motor nor the pack got hot after a run and I was runing it full tilt continuous. I have a feeling that it would swing a 450/3 without overheating. I will try that tomorrow.

Yes I heard the Sea Commander will be kitted again. I hope more will follow as these boats bring back fond memories.

Regards,

Kez

 

[Andrewg]

Kez

how did it go?

With any opf the X series props you need to taper the rear edge of the blade so it is sharp like the front edge

Also round the prop tips reducing diameter as little as possible

 

[Kez]

Hi Andrew,

It actually went pretty well. I tried X447, 450/3 and an old JG I25. The MM on 6-cell swinged it without overheating. The boat now got up on plane clean and achieved about 18mph (estimate). The run time is good as well. The best prop is probably the 2-blade X450 in this set up.

I now enjoy running this boat and will experiment more on the set up.

Attached is a pic. It was probably running at 80% throttle as I was holding the camera and the transmitter at the same time.

Thanks,

Kez

 

[Andrewg]

Kez thats excellent

That sounds right on the money - the boat looks very scale

If you want longer runtime - you can parallel the packs but as soon as you notice a speed drop finish the run as there may be a greater chance an unblanced cells will be heading toward reverse polarity

discharge the individual cells to help avoid this

Andrew

www.fastelectrics.com

 

[MikDee]

IMHO a 17turn Trinity Monster Max E-Max motor would work best here, it is also a 550-600 size motor.