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Author Topic: Motor help needed.  (Read 1716 times)

gregk9

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Motor help needed.
« on: April 11, 2011, 11:55:46 PM »

I have recently purchased the hull as seen in the pictures below. It was previously fitted with what appears to of been an "i/c" engine, but this is NOT an option for me, it will have to be electric powered.
the hull is approx 40" long, by 11" wide. the side sponsons are 2" wide and 3" deep and have no internal bulkheads fitted.

So, reason for asking is.

What would you guys suggest as the better option for it.
I am torn between fitting twin motors/props, as I think it would run better than a single motor.  Also would it be better to place the motors in the outer sponsons, as low as possible, rather than mount centrally and then have to run flexi drives down to the props, as Im thinking it looks very much like I could get a straight drive motor/shaft inside the sponsons with ease.
but then, what to do about rudders? would it then be preferable to have a rudder behind each prop? or centrally mount a single/twin unit.

So, what motor/s?  what size of props and recommended battery sizes.

i dont have the biggest bank account in the world, so dont go quoting mega buck, reasonable prices is my game court, im here to enjoy the sport not pay an arm and a leg for things.
















yes, the air scoop is missing off the cabin roof, I will be sorting that out too, once i have removed all the dead paintwork and started afresh. i have a couple of splits in the hull, the one on the nose of one sponson is concerning, but I can soon fix that once I can remove all the old bonded on sealer from an earlier attempt to repair failed.
All the decals have now been removed and ready for an attack on the paint, as there seems to be several coats, so dont want to over spray it too much, just incase it al then starts to react and blister up, so may well strip it all back to original shell.
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Best wishes.

Steve. G.
Treasurer & Membership Secretary:  Chasewater Model Boat Club
http://chasewatermbc.blogspot.com/

triumphjon

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Re: Motor help needed.
« Reply #1 on: April 12, 2011, 08:14:08 AM »

i should imagine that a single shaft / motor would be the simplest option , as you already have the exit position for a flexi shaft and the mounting holes in the transom for the strudder unit to bolt through ? the better route for power to weight route appears to be with a  brushless motor ! im in the process of fabricating aluminuim air scoops for those who require functional air intakes ? jon
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gregk9

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Re: Motor help needed.
« Reply #2 on: April 12, 2011, 03:36:32 PM »

hi Jon, may take you up on an air scoop, that would save me some work making a pattern , then vac forming one.
Im not too bothered about the original holes in the hull floor. Im not keen on flexi shafts with brushless motors, all the ones ive seen have failed rather quickly, needing replacement.
So if I need to place the motors down low in thew sponsons, id do that instead, all i need is some suggestions as to what motors would be suited for this size of boat, best option size for props and battery options, if to go for single battery pack, or split to even the weight and add capacity.







All the tacky decals are now off and its ready for me to remove the old paintwork. this is where good old "fairy power spray" comes in to its own.
the holes in the plastic hull are not a problem to me, im well used to working with styrene, so they wont take anything to fill up and seal over, once im fully back to original plastic base, im not going to attempt to seal these holes untill i can see the original base.
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Best wishes.

Steve. G.
Treasurer & Membership Secretary:  Chasewater Model Boat Club
http://chasewatermbc.blogspot.com/

martno1fan

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Re: Motor help needed.
« Reply #3 on: April 12, 2011, 05:37:47 PM »

Only one way to go with electric on that size hull in my opinion and thats brushless with flexi drive.Im planning a 57" electric build using one of my Arrow hulls using two big outrunners and 6 s lipos its not cheap but should be fun.Also last thing you want with a fast electric hull is air scoops you want it water tight,just water cool the motor and esc and your good to go.Theres a few guys running the genesis cats 37" on single outrunners on 6s (3s x2 one in each sponson) and theyre getting some very fast speeds,you could go 4 s and get arround 35 mph pretty easy.Checkout offshore electrics for some similar builds.
Mart
http://forums.offshoreelectrics.com/index.php
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triumphjon

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Re: Motor help needed.
« Reply #4 on: April 12, 2011, 11:19:21 PM »

gregk9 , if you pm me with the dimensions of the scoops required they can be made , , i have in the past converted a v24 mono hulled offshore powerboat and managed to fit a short m4 solid shaft through the transom with a home made strudder for steerage , this worked well until a novice driver failed to stop before she got to the edge of the lake & wrote off the hull !
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tiggy_cat

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Re: Motor help needed.
« Reply #5 on: April 13, 2011, 12:33:14 AM »

Hi Greg,

I am currently building a Graupner PX-1 cat, very similar dimensionally to the one you have. I have opted for Turnigy T600 1400KV brushless outrunners. Just for the hell of it, 3 of them. One each in the sponsons, probably running solid shafts, counter rotating for balance, and the third powering through a HOR strudder and flex shaft. 

Power looks like 6s lipos or 4x 3s run in series and then parallel to get 6S2P for enough power.  Ideal power controllers would be Turnigy T180's but that gets a bit expensive as Mart pointed out, so might go for something a bit cheaper in the 200A range, from Giant Cod.

The above might be a bit excessive but it is more for the challenge than anything else.  If you are looking for something a little more economical, have a look on Astec's web site at the Leopard 4074 range of brushless motors, 2 of those should give you enough power to get the hull shifting
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martno1fan

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Re: Motor help needed.
« Reply #6 on: April 13, 2011, 08:37:41 AM »

Hi Tiggy ,i have two of the t600 880 kv motors for my large vee, im using the HK 200A escs 6s lipos 1p will go to 2 packs later.I think your boat would fly with one of the 1400 ones i know of one pushing a 36 sprintcat close to 50 and another pushing a 40" cat to 50s so 3 in a small boat will be scary  :o..Two would be enough for a cooler setup with great speeds me thinks.I think my whole package with hardware has cost me arround the same as it would cost for a gas motor but its just something i wanted to try for the hell of it lol.I plan on trying one single 1100 kv one in a small 36-38" cat,should push it very well and run a bit cooler than the 1400 maybe.How about abuild thread on yours id be more than interested in seeing how she comes together  :-)).
Mart
heres the sprintcat with a single t600 1100kv outrunner on 6s lipos
http://www.youtube.com/watch?v=9kgn5vhOdZQ&feature=player_embedded
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