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[des321]

With very limited experience I am scratch building a Springer tug that I intend to be a rescue boat. The idea being to allow me to go to the lake when maybe nobody else is there. I have found a lot of helpfull information on this forum but nothing to answer the following.

I am thinking of fitting a steerable Kort nozzle around a 50mm prop. Is this a sensible way to go? Would I do better with a fixed Kort and Rudder? I assume I need a slow high torque motor. Any suggestions? Would the Mobile Marine Models T4A at 6v do the job?
Should the prop shaft be horizontal or angled downwards?
Thanks for any informed replies.

[chingdevil]

I would keep it as simple as possible so no Kort's just prop plus rudder, my springer has a 50 x 50 rudder with a 38mm prop and can virtually turn on its own length. Try to keep the prop shaft as level as possible, as the springer is notorious for diving. I have not used a T4A motor, mine is fitted with an Action 545 motor on 6volt, the batteries are two 6volt 4ah SLA's in parallel for ballast and power.
Hope this helps.

Brian

[craftysod]

Forget a Kort nozzle,a simple prop and rudder arrangement will be suffice,
The kort nozzle will not give you the turning circle you require,but with the standard
arrangement you will get the turning and propulsion you require.
Ask my missus,she rescued me and other boats on more than 1 occation,and she only knows full speed  ahead.
Mark

After reading Brians post,do not use a t4a motor i have got some,superb motors,but not for a springer,built for power,
not speed,i recommend a 540 or equivalent
Mark

[Martin (Admin)]

"...mine is fitted with an Action 545 motor on 6volt, the batteries are two 6volt 4ah SLA's in parallel for ballast and power."

... and Chingdevil's  is probably the best performing Springers there is!   
  (What prop do you use Brian?)

[chingdevil]

Martin

I brought my prop from Prop Shop, I have used others but I still think it is the best one.


Brian

[portside II]

Like you say , keep it simple .
I found the easiest set up for me is two 6v 4ah batts connected in parallel, 540 motor,graupner 3:1 gear box to a 50mm 4 blade brass prop. this set up gives me plenty of torque and a run time of about 3 days ,
oh and a rudder 3 1/2 X 4 1/4 also makes it very manoverable ,
my rudder linkage is a closed loop using chains, just to be different  .
My set up may not be to the regulations  but who cares i like it
daz

[des321]

Thanks guys. That's been really helpful.