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Author Topic: SDM tug mkII  (Read 1433 times)

portside II

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    • goole model boat club indi site
SDM tug mkII
« on: May 04, 2010, 11:08:29 AM »

I have had a pair of the big graupner schottels for a while in the shed and now i have the dervos to match i thought i would put them to work .
After a breif discussion with Poll i made the hull from a simple deck with a box underneath and polystyreen around the sides for buyancy ,
a wire frame was made to support the hull and protect the schottels from damage .The schottels were fitted in opposit corners and
the electrics comprised of a pair of electronize esc's and a disribution board from ACtion , all working off a planet 2.4ghz radio.
First water trials were not that great , Quote from our news letter, oh it had a red deck .

"The red one had an impressive array of electrical equipment and after a few minutes on the pond an equally impressive amount of water"

But on the second water trial it was better (little water) but Poll did warn me , they are not the easiesd things to controll , yeh right
it was more like trying to controll a ball bearing on a sheet of glass which is also on a ball bearing . This thing would go sideways with some degree of controll ,
but as for forwards and astern not a cat in hell chance  .
So it is back to the drawing board and the latest design will have the two drives forward and a big skeg (fixed rudder) at the rear , much like a tractor tug
hopefully it will be more stable as the drives will be linked together .
Its only on the saw bench at the moment so pics to follow , and as for the other one it is still sat on the bench outside waiting for an empty wheely bin .
daz
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I like to build my boats to play with, not to just look pretty,so they dont !

Umi_Ryuzuki

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Re: SDM tug mkII
« Reply #1 on: May 04, 2010, 07:38:47 PM »

Something to consider with the schottel drives, is that full power will often overwhelm a standard servo.
If you were using a standard servo(torque) to steer the schottels, then it may be, that they were being
forced out of alignment when full power was applied.

I very much enjoy running my SDM, in all directions. However if I hand the controls to
anyone else, about 90% of them can not drive it straight.

 %)
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portside II

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    • goole model boat club indi site
Re: SDM tug mkII
« Reply #2 on: May 05, 2010, 11:00:54 PM »

Thanks Umi , i did find that out at an early stage with the standard servos , so i purchased a pair of Savox servo's which have a torque of 10.5kg (Savox SC0252MG) .
I dont intend to try and steer at full chat as even they would have some strain on them ,
i think maybe the problem with the old hull was that there were no skeg's to give some guidance .
But the new hull will have a deep skeg at the stern for stabillity and also to protect the schottels from damage .
More to follow .
Ps as it's sourounded with polystyreen at least it won't sink and be ascociated with some of my other stuff  %) .
daz
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