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Author Topic: U47 robbe tech rack  (Read 7437 times)

tsenecal

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Re: U47 robbe tech rack
« Reply #25 on: May 03, 2015, 01:43:07 AM »

Didn't mean to leave you guys hanging on this... two shots of the internals...  the two pieces on fore and aft that appear somewhat "white" are what i am talking about. as you can see, when the hull is closed, the two pieces of ABS lay against each other.    start by taking two sheets of styrene (i used .040, but anything will work) , cutting a 4" hole into them, so they slide over the internal WTC cylinder, and tape them together so there is zero space between them.   close the two pieces of the WTC together, and then either glue the rear external hull in place as the instructions indicate, or temporarily hold the rear in place so it doesn't move.  use plastic "weld" type glue to glue the sheets to the appropriate external hull parts.  after the two sheets have basically been solidly attached to the corresponding original skins, shave the two sheets down until they follow contour of the external hull.   putty and sand until the seam between the original hull and the new sheets is gone.


any more questions, ask, and i promise i will answer


metrically speaking, 1mm sheet would basically be the equivalent of .040"
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tsenecal

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Re: U47 robbe tech rack
« Reply #26 on: May 03, 2015, 01:50:04 AM »

as to the tank size....  its difficult to know exactly what the best size is...  like i said 750ml can be made to work, but it also has to do with the fact that there is a limited amount of space inside the cylinder.  much larger than the 750ml, and you also have to start looking at how much room is needed for the piston rod, and how far the tank has to be moved to make room for it.  I will post another pick of where and how i have the tank situated.
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tsenecal

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Re: U47 robbe tech rack
« Reply #27 on: May 03, 2015, 02:50:56 AM »

Okay,


two photos.

this is a custom built 1/8" acrylic addition to the original tech rack.  designed to allow for the addition of the tank, without all the leftovers for the lead acid batteries.   on the top, from rear to front: three servos, rear dive planes, rudder, front dive planes.  two 400 size graupner motors with 3:1 planetary gearboxes, motor speed controller, ballast tank.  in front of the ballast tank is space where the ballast tank controller and receiver were located.  on the bottom, from rear to front:  5 cell nimh battery, ballast tank, and room for 3 more 5 cell nimh batteries.   the battery packs were each 3000mah, giving me a total of 6v 12000mah for the battery.  speed controller fed the receiver.    for the specifics, the way it was setup, the rear of the ballast tank is 280mm from the inner edge of the rear endcap.  the plastic tube that you may see some of in the photos for the piston rod to go through ends 65mm from the inner edge of the rear endcap (the 1/2" white "line" running between the motors).   in all honesty, i think the ballast tank could be moved a little further forward, based on the amount of foam i had to put in the stern free flooding section.   maybe 20mm further forward.

the big white strips you see underneath the ballast tank are lead weights

the brass tube running along side the tank is an 8mm ID tube to feed the ballast tank.  it is in two pieces.  one is soldered to ballast tank, one is bonded to endcap.  the 1"+ piece of shrink tubing links the two together where the ballast tank motor is located.
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Silent Running

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Re: U47 robbe tech rack
« Reply #28 on: May 03, 2015, 09:56:31 PM »

Is it a big job to convert to a pump system? How much are those 800 pumps? Would I need new batteries etc. to make space? I'd better get my boat wet first. :embarrassed:
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tsenecal

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Re: U47 robbe tech rack
« Reply #29 on: May 04, 2015, 12:15:13 AM »

Silent Running,

yes, it is a big deal to make the U47 a static diver.  due to space, the original batteries cannot be used, new batteries that fit in areas that were unused before must be made... why?  because the space where the original batteries go is where the tank goes.   to buy the engel 750ml tank and controller is going to cost about 220 euros. new batteries (in my design) were another 70 euros.  then all the time and work to make the changes to the tech rack
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