Baitboat mk4 won’t reverse???????

[Neil Powell 1Participant @neilpowell1]

Morning,

So i've just lake tested my baitboat Mk4 and all is good when going forwards. It has decent speed and turns well. When i put it in reverse however it just goes forward. I have checked the rotation of the props. As i look at them, looking at the rear of the boat, they turn anti clockwise when in forward and clockwise in reverse.

Props are 62mm S type props on brushed 775 motors. I've attached some photos if they help.

[Neil Powell 1Participant @neilpowell1]

[Richard SimpsonModerator @richardsimpson88330]

If you are saying that the propeller rotates in the correct direction going forward and reverse then the only remaining option is that the flat wall that you have in front of the prop is acting as a baffle and so the propeller is basically pushing against the hull rather than the surrounding water when going astern. If you can try to get some sort of conical fairing in front of the propeller to direct the flow out into the surrounding water I think you will see a significant improvement.

I suspect you are seeing forward motion when in reverse as the thrust from the prop is bouncing of the flat wall and coming aft again thereby generating a little forward thrust.

You can try with some sort of temporary plastic conical arrangement to see what works best. You will actually find that a conical shape in front of the prop will also help the forwards progress significantly as it helps with the flow over the prop. At the moment you have an area of negative pressure behind the flat wall, which will be also spoiling the flow through the prop in the ahead direction.

[Neil Powell 1Participant @neilpowell1]

Posted by Richard Simpson on 29/07/2021 08:42:55:

If you are saying that the propeller rotates in the correct direction going forward and reverse then the only remaining option is that the flat wall that you have in front of the prop is acting as a baffle and so the propeller is basically pushing against the hull rather than the surrounding water when going astern. If you can try to get some sort of conical fairing in front of the propeller to direct the flow out into the surrounding water I think you will see a significant improvement.

I suspect you are seeing forward motion when in reverse as the thrust from the prop is bouncing of the flat wall and coming aft again thereby generating a little forward thrust.

You can try with some sort of temporary plastic conical arrangement to see what works best. You will actually find that a conical shape in front of the prop will also help the forwards progress significantly as it helps with the flow over the prop. At the moment you have an area of negative pressure behind the flat wall, which will be also spoiling the flow through the prop in the ahead direction.

Thanks Richard, are you suggesting something like this?

[ashley needhamParticipant @ashleyneedham69188]

….as Richard says!

…and yes having just seen the doctored snap. Try a temporary baffle with plasticard/tape, and you can refine it before making it permanent.

Is the paint job a bit scary for a bait boat??

Ashley

Edited By ashley needham on 29/07/2021 08:58:17

[Neil Powell 1Participant @neilpowell1]

I had 2 other thoughts whilst researching.

The waterline is quite close to the prop as shown in my edited photo. Should the props be a bit lower in the water or would a smaller diameter prop help. Also could they do with being moved away from the hull a bit more. Originally i had planned to fit rudders behind the prop.

[Ray Wood 3Participant @raywood3]

Richard is on the money !! that boat will scare the fish away it looks ferocious

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

Could try smaller X50 props, as these have more twist for better reverse…cheap enough.

Also a vertically set splitter wedge, to direct thrust either side rather than down.

Air being sucked into the prop should be visible when reversing if its happening. A slower reverse might be all that’s needed?

Ashley

[Neil Powell 1Participant @neilpowell1]

Posted by ashley needham on 29/07/2021 09:02:12:

Could try smaller X50 props, as these have more twist for better reverse…cheap enough.

Also a vertically set splitter wedge, to direct thrust either side rather than down.

Air being sucked into the prop should be visible when reversing if its happening. A slower reverse might be all that’s needed?

Ashley

I tried the slow reverse but no good. Ok so if i add a structure that directs the flow away from flat section it should work?

[ashley needhamParticipant @ashleyneedham69188]

Nothing’s certain, but having a vertically arranged splitter will not affect forward propulsion and may even help it by smoothing out the incoming water flow.

Sort of, anything should be better than the flat surfaces you have at the moment for reversing.

perhaps worth mentioning would be a cowl over the prop like a fixed Kort nozzle. This should improve the efficiency of the props by quite a bit. Best with “flat” radiussed off ends on the props to match the duct.

Ashley

[Neil Powell 1Participant @neilpowell1]

Posted by Ray Wood 2 on 29/07/2021 08:59:16:

Richard is on the money !! that boat will scare the fish away it looks ferocious

Regards Ray

Thanks Ray. Could have bought one off the internet for the money i've spent making it but then it wouldn't be one that i've created.

[Richard SimpsonModerator @richardsimpson88330]

I was actually thinking of a cone shape along these lines. The curved plate you show will only direct water downwards, so you are getting limited effect and it will not help forwards flow in any way.

A cone will help water flow in both directions and will direct astern flow all around the prop.

 

I would try turning down a piece of broom handle to a cone, drill a hole through it of shaft diameter, remove the prop and slide it on.  If it has the desired effect you can make it permanent.

Edited By Richard Simpson on 29/07/2021 10:31:59

[Neil Powell 1Participant @neilpowell1]

Posted by Richard Simpson on 29/07/2021 10:27:24:

I was actually thinking of a cone shape along these lines. The curved plate you show will only direct water downwards, so you are getting limited effect and it will not help forwards flow in any way.

A cone will help water flow in both directions and will direct astern flow all around the prop.

I would try turning down a piece of broom handle to a cone, drill a hole through it of shaft diameter, remove the prop and slide it on. If it has the desired effect you can make it permanent.

Edited By Richard Simpson on 29/07/2021 10:31:59

Ok so i'd already taken the bull by the horns before i read this reply Richard(i'm self isolating so needed something to occupy my mind). I have stripped out the shafts and removed what was the rudder mounts. I've mocked up what i was considering .

and

The inspiration was taken from my baitboat mk 3 as below.

This worked really well on the mk3 with no issues going forwards or backwards. No issues with the MK4 going forwards.

[Neil Powell 1Participant @neilpowell1]

Plus i don't have the kit to turn anything i'm afraid.

[Richard SimpsonModerator @richardsimpson88330]

Whittle it down with a Stanley knife.

Or do what Ashley does and strap a large motor to a Workmate!

There is always more than one way

Edited By Richard Simpson on 29/07/2021 13:54:48

[ashley needhamParticipant @ashleyneedham69188]

….safely of course! Snaps showed the foam after it had been turned and several clamps removed! Also the turning masses were very light.

Neil, take the wedges to the edges of the upright sides, having a little wedgie makes it look half done, and also still leaves flat surfaces in the wake.

You could make the wedges from foam and just slip them on, use epoxy or Gorilla glue…even that insulation foam you see in skips is ok if sealed with epoxy (not polyester resin) or even just painted. That would be easy to do and very neat, and could follow the contours of the base properly. 

Ashley

Edited By ashley needham on 29/07/2021 13:59:08

[Neil Powell 1Participant @neilpowell1]

THanks everyone for the help. I've got a plan now and will hopefully get it sorted over the next couple of weeks. Just one more question, i'm just considering the best way to fix the outer shafts in place. Has anyone used expanding foam to do this?

[ashley needhamParticipant @ashleyneedham69188]

Expanding foam No no no no no no no.

Epoxy or p38 filler yes.

Ashley

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