lots of yaw at high speed under power

[DaveC426913]

I've surely asked this before, but it can't hurt to ask again.

Doing 7-10 knots under power, my Sea Saw wallows like a ...well a walrus. Cannot keep it pointing in one direction for any length of time, even with much practice and a light touch. Must terrify any oncoming vessels, who probably think the thing is skipperless.

I take the rudders up but keep CB down 25%.

Any way I can reduce the back and forth yaw?

[Ormonddude]

Mine dont smooth out till around 12 knots but I am much better even at lower speeds it just takes practice. Once you truly wit a plane it handles more like a speed boat

[jimbo]

What is weight distribution in the hull?
I notice this as well if I have some one on the foredeck under power for example. Things settle down if they return to the cockpit.

[Highlander]

No center board down @ high speeds

J

[Tomfoolery]

^^^^^^^^^^^^ Ditto that. ^^^^^^^^^^

Doesn't contribute anything good at high speeds, and can cause wallowing, at least in my experience.

[DaveC426913]

What is weight distribution in the hull?
I notice this as well if I have some one on the foredeck under power for example. Things settle down if they return to the cockpit.

No one forward.

No center board down @ high speeds

Gotta. It just makes it worse if I have the CB up. It's only down enough to act like a fin/skeg.

[Crikey]

The Centerboard on an X, lowered 25%, is still too much for this speed, under power. The hull is being pushed from the rear, not pulled from the front as it is when sailed, and the dynamics of the balance point centering around the keel are altered when you do this. It's not the same thing, either, as when you are deployed during a docking maneuver for more control in a tight space.
Try much less than this amount, if you want to experiment under similar conditions, but also take a good look at how the weight is distributed fore to aft. As this is almost never mentioned by our hoardes of X owners - I think you will find most of the problem lies in the ballasting.

R.

[JohnCFI]

Mine improved after I put my three house batteries up forward (Stbd Side) and spare water (Port side) moved them from in the aft berth. But I rarely exceed hull speed..

[mastreb]

No boat is stable in steerage while semi-planing, which is the speed from 7-12 knots on a Mac X or M. Point straight, all boards up, and get the boat upon an plane or below it. Having your CB down 25% is definitely contributing to the problem and at planing speeds is completely unsafe.

I wrote a post on the dynamics of why this is the case, but the the short version is that while steering under displacement the hull rolls to outside the turn, and while steering under plane the hull rolls to inside the turn. When semi-planing, the boat shifts back and forth between inside and outside rolling dynamically, which is the phenomenon you're describing as wallowing. It's not stable and cannot be accurately controlled, and should therefore be completely avoided for both comfort and safety.

Bottom line: Don't run between 7 and 12 knots except to straight-line transition. Run under or over these speeds. If your outboard can't get you above 12 knots with a clean hull, then your maximum speed is 7 knots.

[kurz]

sorry mastreb, but I dont have any problem to ride between 6 to 12 kn. I do it not too often.

But if it was true what you are saying why buy an outboard of 50hp? Full loaded with all stuff it is not so easy to ride more than 12 kn...

[Crikey]

Another thought on the poor pointing under power: the X swinging keel has a pivot bolt with an engineered amount of play built into it. This is there to provide a canting of the keel under the pressure of sailing, in order to add a little 'aileron' into the picture. When you are partially lowered the keel is pointing rearward (X only) and able to move to the left or right, just like the rudders. This may have a connection with it steering in an unintended direction.

[bscott]

1) Have you adjusted the engine's trim tab to counter the prop walk?
2) Too much engine tilt-either up or down-will cause the boat to yaw and porpoise-power tilt should be adjusted under way as the boat accelerates
3) Check engine height on the transom--the cavitation plate should be about 1" below the bottom of the boat.
4) The Power Thruster stabilized my pm me for details.

Bob

[Steve K]

What Bob said

And........

All boards up!!!!

Some may say otherwise, but all boards up

Empty ballast.

MHO,
SK

[DaveC426913]

The Centerboard on an X, lowered 25%, is still too much for this speed, under power. The hull is being pushed from the rear, not pulled from the front as it is when sailed, and the dynamics of the balance point centering around the keel are altered when you do this. It's not the same thing, either, as when you are deployed during a docking maneuver for more control in a tight space.
Try much less than this amount, if you want to experiment under similar conditions, but also take a good look at how the weight is distributed fore to aft. As this is almost never mentioned by our hoardes of X owners - I think you will find most of the problem lies in the ballasting.
R.

OK, your suggestion is to move ballast forward. I do normally have a fair bit of equipment under the cockpit.

Bottom line: Don't run between 7 and 12 knots except to straight-line transition. Run under or over these speeds. If your outboard can't get you above 12 knots with a clean hull, then your maximum speed is 7 knots.

Well that sucks...

At max, with one occupant, I manage 11Kn. If I have to keep it under 7, that means I have about 35% more engine than I need.

Another thought on the poor pointing under power: the X swinging keel has a pivot bolt with an engineered amount of play built into it. This is there to provide a canting of the keel under the pressure of sailing, in order to add a little 'aileron' into the picture. When you are partially lowered the keel is pointing rearward (X only) and able to move to the left or right, just like the rudders. This may have a connection with it steering in an unintended direction.

Maybe I'll try 10%. Or less.

1) Have you adjusted the engine's trim tab to counter the prop walk?
2) Too much engine tilt-either up or down-will cause the boat to yaw and porpoise-power tilt should be adjusted under way as the boat accelerates
3) Check engine height on the transom--the cavitation plate should be about 1" below the bottom of the boat.
4) The Power Thruster stabilized my pm me for details.
Bob

1) Doubt that's a major factor.
I'll check on 2,3 and 4.

Thanks guys.

[dlandersson]

Do what I do - just don't go fast.

In any case, above 6.5 knots, swing keel should be up.

I've surely asked this before, but it can't hurt to ask again.

Doing 7-10 knots under power, my Sea Saw wallows like a ...well a walrus. Cannot keep it pointing in one direction for any length of time, even with much practice and a light touch. Must terrify any oncoming vessels, who probably think the thing is skipperless.

I take the rudders up but keep CB down 25%.

Any way I can reduce the back and forth yaw?