Dufour 36 Classic

[Timgyacht]

Just looking at purchasing yacht around 36ft. We mainly will be sailing British isles French coast and down to Canary Islands. There is a Dufour 36, just worried about ballast ratio at 27%. Will she be safe capable boat if caught in a storm like I was in bay biscay F9. TIA

 

[doug748]

Just looking at purchasing yacht around 36ft. We mainly will be sailing British isles French coast and down to Canary Islands. There is a Dufour 36, just worried about ballast ratio at 27%. Will she be safe capable boat if caught in a storm like I was in bay biscay F9. TIA

I understand the deep keel version has a lead keel, which would help a lot. It's actually not very deep at all so that looks like the one to ideally go for.

 

[Shaddickp]

I have the deep lead keel version and she is very stable. I've only once had the toe rail under the water and that was a full on Bora in the Adriatic. Had 3 main reefs in and it all felt pretty comfortable.
The lead keel had a large bulb at the foot so a good deal of the weight is at the end of the 'lever arm' adding to it's stability.
How much you looking to spend ?

 

[Timgyacht]

Thanks for that! Around £50k mark, we are looking at a couple of moody’s 34s & 35? But we are fairly open minded? Mainly be me and the misses, maybe friends and family from time to time??

 

[Baggywrinkle]

Just looking at purchasing yacht around 36ft. We mainly will be sailing British isles French coast and down to Canary Islands. There is a Dufour 36, just worried about ballast ratio at 27%. Will she be safe capable boat if caught in a storm like I was in bay biscay F9. TIA

What were you on in Biscay? How did it feel?

Ballast ratio is not really a measure of stability, stability depends on the relation between the boat centre of buoyancy (CB) and centre of gravity (CG) - a heavy, shallow keel can produce the same CG as a longer lighter one with the weight in a bulb - and give the same righting moment - that's why shoal keels are heavier than standard keels. It alters the ballast ratio, but not the stability.

When the boat is upright CB is above CG, they are alligned and the boat is in equilibrium.

As the boat heels, it rotates around a metacentre (which is always directly above CB). CB moves outboard of CG and this creates a righting moment (RM) which is trying to force the boat back to its equilibrium position. The horizontal distance created between CG and CB as the boat heels is called the righting arm (GZ) - for GZ, bigger is better. A wider, more buoyant hull increases GZ as does ballast as low as possible - the reason so many boats now have wide hulls with chines and bulbs on their keels.

Eventually, the boat reaches a point of no return, the angle of vanishing stability (AVS), where the boat must capsize and enter a meta-stable state.

In this capsized state, the righting arm disappears and CG and CB are again vertically aligned. Now, however, the metacenter and CG are in the same place, and the hull is metastable, meaning it is in a state of anti-equilibrium. The slightest disturbance will cause it to turn one way or the other and right itself - but it is good if this happens fast, because the cockpit is under water during this time.

So have a look at the GZ curve for the boat, it will show the righting moment increasing as the boat reaches it's angle of maximum stability (AMS), decreasing until it reaches it's angle of vanishing stability (AVS), going negative until it is inverted, and then going positive again until it is back where it started.

Generally, the higher the AVS the better, and the bigger the righting moment the better - but ballast (and ballast ratio) are just part of the story.

GZ curves are calculated for empty boats. Add all your cruising gear and it can have a big effect on your GZ curve depending on how heavy your gear is is and how high in the hull it is stored. Lower is better. Full water and fuel tanks are better as they are usually low in the hull.

.. and all this is meaningless if you get water in the hull when the boat rolls ... downflooding into the cabin, most likely through the companionway makes recovery a lottery. Similarly, broken windows, cockpits that don't drain fast enough. The recent demise of Bayesian is an example of a boat sinking in freak weather that really shouldn't have happened.

Personally, I wouldn't worry too much about the absolute limits of the boat as when you get rolled so many other issues come into play it's a lottery.

Buy the boat you feel comfortable in (traditional or modern) as everything with a Catagory A rating will be capable of doing what you want.

 

[Timgyacht]

What were you on in Biscay? How did it feel?

Ballast ratio is not really a measure of stability, stability depends on the relation between the boat centre of buoyancy (CB) and centre of gravity (CG) - a heavy, shallow keel can produce the same CG as a longer lighter one with the weight in a bulb - and give the same righting moment - that's why shoal keels are heavier than standard keels. It alters the ballast ratio, but not the stability.

When the boat is upright CB is above CG, they are alligned and the boat is in equilibrium.

As the boat heels, it rotates around a metacentre (which is always directly above CB). CB moves outboard of CG and this creates a righting moment (RM) which is trying to force the boat back to its equilibrium position. The horizontal distance created between CG and CB as the boat heels is called the righting arm (GZ) - for GZ, bigger is better. A wider, more buoyant hull increases GZ as does ballast as low as possible - the reason so many boats now have wide hulls with chines and bulbs on their keels.

Eventually, the boat reaches a point of no return, the angle of vanishing stability (AVS), where the boat must capsize and enter a meta-stable state.

In this capsized state, the righting arm disappears and CG and CB are again vertically aligned. Now, however, the metacenter and CG are in the same place, and the hull is metastable, meaning it is in a state of anti-equilibrium. The slightest disturbance will cause it to turn one way or the other and right itself - but it is good if this happens fast, because the cockpit is under water during this time.

So have a look at the GZ curve for the boat, it will show the righting moment increasing as the boat reaches it's angle of maximum stability (AMS), decreasing until it reaches it's angle of vanishing stability (AVS), going negative until it is inverted, and then going positive again until it is back where it started.

Generally, the higher the AVS the better, and the bigger the righting moment the better - but ballast (and ballast ratio) are just part of the story.

GZ curves are calculated for empty boats. Add all your cruising gear and it can have a big effect on your GZ curve depending on how heavy your gear is is and how high in the hull it is stored. Lower is better. Full water and fuel tanks are better as they are usually low in the hull.

.. and all this is meaningless if you get water in the hull when the boat rolls ... downflooding into the cabin, most likely through the companionway makes recovery a lottery. Similarly, broken windows, cockpits that don't drain fast enough. The recent demise of Bayesian is an example of a boat sinking in freak weather that really shouldn't have happened.

Personally, I wouldn't worry too much about the absolute limits of the boat as when you get rolled so many other issues come into play it's a lottery.

Buy the boat you feel comfortable in (traditional or modern) as everything with a Catagory A rating will be capable of doing what you want.

Christ that is a lot of information!! Thanks for advice
Biscay was on 36ft Van da Stadt, we headed into deeper water, as had about 4hr warning off navtex, reefed in and got very wet!!