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flexible propeller shafts

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jeffrey mundell 131/12/2020 15:50:15
26 forum posts

i am just starting on a model boat with twin Korts nozzles,which i purchused from MMJ and very nice mouldings indeed,as the korts have to be mounted in horizonal position and motors are quite high up in hull i think it would be best for a pair of flexable shafts,but where can i obtain some?

the model is a American pusher tug of 750mm size

Has anyone any thoughts on this matter

regards Jeff

jeffrey mundell 131/12/2020 15:53:58
26 forum posts

Just a tought the Korts were purchused from MMJ, not the tug which i am scratch building


ashley needham31/12/2020 19:15:59
6920 forum posts
201 photos

Jeffrey. Flexishafts are really meant for racing boats which have motors forward, to keep the prop line flat.

They require a lot of maintenance, as the wire wound drive is not rustproof and ideally needs stripping, drying and re-greasing after every run. Usually this means loosening the solid coupling grub screw or collet, and withdrawing the shaft rearward.

Cant say that I have heard of flexis being used in a tug, but I may be horribly WRONG!

I would think that a small downwards angle should not be that detrimental to the Kort? Also, why are the motors so high? Normally something you would install low down.


Charles Oates31/12/2020 20:40:52
597 forum posts
50 photos

Hi Jeffrey, yes the korts need to be horizontal, but there is no practical reason why the props and shafts cant be angled, it's what I and hundreds of others do. Normally we just adjust the motor and shaft layout in the hull to give as flat an angle as is practical, remembering to position the motor and coupling where they can be easily accessed for maintenance.

Like Ashley, I've never heard of flexies being used in a sedate model, all that messing about in a delicate scale model wouldn't be for me.


Malcolm Frary01/01/2021 09:40:13
944 forum posts

Tugs do need reverse, flex shafts tend to unwind themselves in reverse, so they don't get used on tugs.

Chris E01/01/2021 09:59:33
198 forum posts
Posted by Malcolm Frary on 01/01/2021 09:40:13:

Tugs do need reverse, flex shafts tend to unwind themselves in reverse, so they don't get used on tugs.

Agreed. Never use flexible shafts if you need reverse which you most certainly do with a tug.

I am not familiar with MMJ, and thus clearly not your model, but with a tug hull it is normally possible to mount the motors quite low. Yours must be the exception.

Edited By Chris E on 01/01/2021 10:03:42

Charles Oates01/01/2021 10:20:04
597 forum posts
50 photos

Hi again, as you can see, people on here would all like to help. I suggest you post some pictures, this might make a big difference to the advice you get. If you haven't posted pictures before, go to all topics, and look at the item on posting pictures.


jeffrey mundell 102/01/2021 15:08:44
26 forum posts

many thanks for your replies,i did not relise that with the kort mounted horizonal the prop inside could be at an angle very slightly,as this was pointed out in the post by Charles Oates ,so this has solved the problem.

all have a happy and good New Year


live in New Malden

Charles Oates02/01/2021 15:28:10
597 forum posts
50 photos

Perhaps this will help.


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