Motoring - lift keel up or down?

[William_H]

My drop keel is always locked in place for the season. At 100kg it is a pain to winch up using 4 purchase tackle and halyard winch. It is a beast to steer without keel down under motor. As with ingwe my keel has a square box section on top which fits tightly in to the CB case. I is reasonably robust in a collision with bottom as I have a bolt through at the aft end of the case to absorb deflection back and up at trailing edge. I reckon any collision with CB half up would wreck the trailing edge of CB. (Finely shaped GRP.) Hitting bottom is non uncommon for this skipper. Fortunately a fairly light weight 21fter.
Having said all that it is currently sitting on the trailer half keel down pushed back by about 25cms and trailer jacked up[ by 10 cms to expose half the keel which has just been painted. (A/F) The top half of the keel is accessible from inside the cabin and has been painted. Tomorrow winch up the keel apint the hull underneath a real pain with trailer structure in the way. Relaunch tomorrow week for a brand new season. (season 42)
ol'will

 

[ducked]

Bear in mind some keels are not designed to be used part up. I have a first 18se, a similar question came up on our Facebook group a couple of months ago and the designer came straight back and said don't do it, basically the shape of the keel means that if it is only part down it does not fully fill the slot due to slight tapering of the keel section, so can move more than it should laterally and damage the mechanism.

Clearly a man who likes to make life difficult for his customers

 

[Supertramp]

Isn't the real question here what the stability of the boat is when the board is raised?

Southerly and Ovni have substantial ballast plates in addition to the board weight, plus their boards pivot, keeping the board weight at or below the waterline. They remain stable with board up.

A vertical lifting keel without a ballast plate will raise the centre of gravity (although some may have a bulb on the keel base). In this case I would want to know the boat retained sufficient stability to sail or encounter a broaching wave or wake without drama. Some vertical lift keels need locked down effectively creating a fixed keel. If the designer hasn't provided guidance I would handle with care.

 

[Refueler]

Isn't the real question here what the stability of the boat is when the board is raised?

Southerly and Ovni have substantial ballast plates in addition to the board weight, plus their boards pivot, keeping the board weight at or below the waterline. They remain stable with board up.

A vertical lifting keel without a ballast plate will raise the centre of gravity (although some may have a bulb on the keel base). In this case I would want to know the boat retained sufficient stability to sail or encounter a broaching wave or wake without drama. Some vertical lift keels need locked down effectively creating a fixed keel. If the designer hasn't provided guidance I would handle with care.

Exactly.

 

[RogerFoxTerrier]

Wow, a plethora of really interesting responses there - but the jury's still out regarding our boat!

I think, given that I've not noticed any appreciable speed increase with it up, I'll leave it down apart from in shallow water or drying out.

I agree about raising the centre of gravity as there's no other ballast...

 

[fredrussell]

I would say that if the keel/centreboard is unballasted it’s ok to proceed under engine with it up. Mine’s got a ton of lead at the bottom and boat is obviously much more stable with it down.

 

[Refueler]

I would say that if the keel/centreboard is unballasted it’s ok to proceed under engine with it up. Mine’s got a ton of lead at the bottom and boat is obviously much more stable with it down.

It also depends on whether boat has a stub keel ... which usually carry ballast to allow you to have 'board' up when not under sail etc.

 

[Tintin]

Although it's also possible for a dinghy to trip over its board and capsize. There was a good anecdote doing the rounds in the Wayfarer scene. With a squall approaching, one boat lifted its board and simply slipped sideways in the gust. Every other boat dipped a gunwale and capsized.

This is one of the tactics with an Ovni, rather than deploying drogues or sea anchors as you would with a fixed keel yacht. Jimmy Cornell swears by it, and it does seem to work well.

 

[Tintin]

And if it’s knocking half a knot off, then perhaps some attention to it’s surfaces over winter should be on your to do list. Our board makes no measurable difference.

Happens even when freshly anti-fouked, or (as now) freshly copper coated.

 

[James_Calvert]

Glad to see you are going to mostly keep it down. Still got the dent in my toerail when an owner of a similar boat thought it would turn around when up, it wouldn't and so tried more power...

The violent T boning was a bit of a surprise, Victoria marina in St Peter Port is normally very quiet after the sill dries.

 

[seeSimon]

Foil shaped electric lift keel (dagger board style), with 300kg lead bulb at tip.

Yes, similar to tintin.

Two kinds of "stability " here.
1. Directional....steering, when motoring.
2. Righting moment, predominantly transverse stability. Stops me capsizing.

With my Ovni 435, yes I do, and it reduces drag and I get another 0.5kn of boat speed.

If the wind is strong and on the beam then I'll drop it 1/3rd to 1/2 to give better directional stability.

And when sailing, often on a beam or broad reach it'll only be down 1/3rd too.