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Author Topic: Newbie here, building a multi  (Read 1264 times)

joelomunro

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Newbie here, building a multi
« on: February 04, 2015, 09:19:40 am »

Gday everyone, I'm new around here and hence this is post 1.  A little about me to begin with.


I'm in my mid 30s, live in New South Wales, Australia, and work in Canberra, however I'm a Queenslander and have only been down here a couple of years.  I've been interested in radio controlled hobbies since I was a kid, but it took me a while to actually get into it, having actually had a chance to get a start at things about 10 years ago with an RC10GT truck and a multi that I built from a mould which I brought with an engine, rudder and shaft from an ex's dad.  I've been flying radio controlled planes on and off for the last two years also. 


When I built the multi the first time the mould got damaged by a mates bother who apparently 'knew' how to apply gel coat properly.  The hull got pretty well stuck in the mould and getting it out took some of the moulds gel coat with it.  In a flash of inspiration while I was at home last Christmas I dug up the mould in my shed and brought it home with me with intentions of repairing it and seeing if I could make a few hulls for a mate of mine and I.  I've been giving the mould a make over with a gel coat repair product and it's looking like it'll be usable, so now onto some technical queries regarding properly setting up a multi.


First time around I was given, along with the mould, a modified OS .40SF engine with a watercooled head and flywheel, a 3/16" drive shaft with stainless shaft, brass stuffing tube and drive dog, rudder with stuffing box, a uni joint for the engine, a solid engine mount like an octura and a couple of .40 size tuned pipes from my ex's dads pylon flying days.  Not knowing a lot about r/c boats back then I basically just laid out the engine, drive shaft and rudder to best fit the hull and put it all together.  The hull is about 870mm long and I ended up with the rudder shaft at about 55mm from the transom, the propeller at about 130mm from the transom and the engine mounted about 500mm from the transom.  I fitted a balanced and sharpened Octura X442 and ran it in the dam at my parents property.  The boat ran pretty well but was no power house and didn't set a cracking pace.


For the new build I'm keen to try and optimise the layout, correct COG and the like.  I plan on running an old OPS .60 that I recently picked up in mine and an ASP .46 in the one I'm going to make for my mate.  I intend to use a ball raced 5mm drive shaft, rubber cushioned coupling, rubber isolated engine mount and a Mocom or RG propeller.  The hull us a Silak style Multi, atleast that's the best I can do to identify it, and 870mm long.  In this style hull what % COG should I aim for, and what's the optimal positioning for the rudder and propeller?


Long post for a start, but it'll hopefully give me a few ideas to push this project forward, and once I get a bit more boating experience I'll see about getting my other project boat wet, a 40" deep vee mono with surface drive and a Rossi R.65.


Cheers




Joel
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