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[wombat]

Hi All,

Bit of advice wanted - as some of you know I am building an Aziz from Model Slipway. The thing has three ESCs in it - all MTroniks Viper 15s, which are drving a Robbe 1155 bow thruster and two MFA919 (IIRC) geared motors.

Do these units need to be mounted on heatsinks or does any sort of forced cooling need to be provided? I was thinking of mounting on an ali sheet, though I cannot decide how to mount it - vertically to use as a support for the towing bollard or horizontal flat on the bottom of the hull to use passive water cooling.

Also, how picky do I NEED to be in finishing the fibre glass on the inside of the gunwales - it has been given a basic smoothing down with the old Dremel, but how far do I need to go to get something that looks reasonable.

Tim (the Wombat)

[Shipmate60]

Tim,
The geared motors will not need heat sinks as they shouldnt get hot unless they are under severe load. I
 would also fuse the speed controllers at 10 amps, as if they get anywhere near this they are under too much load.
As for the Gunwhales. I use P38 car Body filler then rub down with wet and dry.
You will need fairly good surface to glue the struts to.
It also helps with keeping the GRP in one piece when cutting out the freeing ports.
Some use plasticard on the inside of the gunwhales, some make a good job, but I have seen some comming off after a little while.

Bob

[wombat]

Cheers Bob,

I'm less worried about the motors - it is the ESCs that I am concerned about. The cases of the ESCs are small heatsinks, but are they enough?

Sounds like I have more rubbing down and filling to do >:( >:( >:(

Tim (the Wombat)

[Stavros]

Hi wombat never had trouble wiht the esc overheating heatsinks usually are up to teh job,personally I mount with velcro to lite ply stavros

[Doc]

Tim,
Keep sanding or as suggested, line them with plastic (saves a lot of sanding!).  Heat sinking the ESCs shouldn't be necessary unless you're going to be running them near their limits (current ratings).  If that's the case then mounting on an aluminum plate (no matter what else it may do) isn't a bad idea.  'Course, running them at their limit isn't exactly the best thing to do, right?
 - 'Doc

[dannymax]

I think you would have to be running the "Aziz" as if you wanted it to plane  :) before you needed to worry about the ESC..

[kayem]

Finishing the inside of gunwales, or more correctly bulwarks, on a fibreglass hull. Not the easiest job. The way I do it is to start with coarse #60 abrasive on a small piece of balsa used as a sanding block, this takes care of larger protuberances. Some areas will be thicker, caused by overlaps in the glass in the moulding process, and these will need to be reduced further, but don't take off too much and thin the bulwarks. When you think you've done enough, dust everything off and fill any low areas, sand again when hard, and you'll probably have to do a bit more filling here and there. Go down to just below where the inwales are going to fit, then you'll have a smooth area for glueing. Then go down to something finer like #80 or #100 until you're happy with the finish. You could achieve much the same result with a paint primer, but I mix a small amount of resin with a wax additive to prevent surface tackiness, then sand again until it's smooth enough to paint in the normal way. The resin seals any exposed glass fibres, which can still be visible under many layers of paint if left untreated. Laurie & Dave at Slipway have tried to convince me of the advantages of lining bulwarks with thin plasticard, but that wouldn't work for me, I hate the stuff and wouldn't get good results that way. Each to his own.

[dougal99]

Hi all,

on my Sentinel I sanded first to get a smooth ie lump free surface, then abraded it and used epoxy to glue thin platicard. It seems OK, but have yet to finish the boat (life keeps getting in the way).

HTH

Doug

[Dave Leishman]

I just sand down the GRP to remove any unevenness in the laying up process and then smear P-38 around the sanded areas and smooth that down. Once painted it's fine.

[Shipmate60]

The geared motors shouldnt normally draw more than a couple of amps in normal running, absolutely no problem to the ESC's.
The fuse is only there for a completely stalled motor caused by things like something in the prop / kort nozzle.

Bob

[wombat]

Thanks for all the information everyone.

I had no feel at all for how much power the ESCs themselves would consume - as long as they are not going to start to glow. I will probably still try to stick them on an ali plate, just for the sake of reliability.

I was thinking about lining the gunwales (or bulwarks), and did get some almost paper-thin plasticard in - I think I will try that because if I rub down the hull anymore there will be nothing left of it 

Tim (the Wombat)