Waves slamming

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tortoise

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When motoring against the wind my Jeanneau 39i slams throught the waves falling with a loud bang. Recently I did that in a F7-F8 crossing from Biscay. Some slams were very worrying with the whole yacht badly shaking.
Do I have to be concerned about structural damage? How much slamming can a yacht take?
 
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I would never motor straight into the wind with a F7-F8 especially with big waves.
Not only the hull will take a lot of stress but also the mast will suffer a lot from this treatment.
With a new boat I don't think you have to worry to much about structural damage if this was a one time experience.

The best way to go imho would be steering with the wind 20 degrees of the bow with a reefed mainsail and motor (no headsail). That way you can point high without slamming to much in the waves. But perhaps there was another reason why you had to steer straight in the wind.
 
Motorsailing against the waves is never a good idea.Apart from the possible damage to the boat , it's slow.It's much better to hoist the main and sail a bit off the wind.Speed increases and motion becomes much more pleasant.
 
I will also agree with motor sailing in an angle to the waves but if this angle is large enough to have some genoa on (rather than just the main) it will be an even smoother ride. You need a lot of power at the bow to avoid the heavy slamming.
 
tortoise said:
When motoring against the wind my Jeanneau 39i slams throught the waves falling with a loud bang. Recently I did that in a F7-F8 crossing from Biscay. Some slams were very worrying with the whole yacht badly shaking.
Do I have to be concerned about structural damage? How much slamming can a yacht take?
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Don't you love your boat? Not so kind to chuck it into oncoming seas - adopt an angle, as others have said, to lessen the precipitous falloff. The boat will take the slamming - but it's not seamanlike.

In this force of wind, having even a deeply reefed main up will make you wonder about overpowering etc but it is the better course of action.

Slamming is not unique to your boat but modern styles with large beams naturally present a broad foot to oncoming seas - the slamming reflects the buoyancy of your design: older vessels will submarine in these conditions - less slamming perhaps but a lot of water over the decks, which also slows down progress in vigorous conditions.

PWG
 
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tortoise said:
When motoring against the wind my Jeanneau 39i slams throught the waves falling with a loud bang. Recently I did that in a F7-F8 crossing from Biscay. Some slams were very worrying with the whole yacht badly shaking.
Do I have to be concerned about structural damage? How much slamming can a yacht take?
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Yes you have almost certainly devalued the boat enormously, however I am prepared to offer to take her off your hands for £5000 :D
 
Its just these modern designs have large flat areas to increase volume inside. They all slam and its nothing to worry about they are designed to take it within reason of course :)
 
Its down to the underwater shape of the hull with flat panels maximising internal accommodation.

Yes it can damage and even cause the break up of the boat but when and under what conditions that happens will be decided also by how heavy and tough the boat structure is.

Jeanneau make bl**dy good boats but I would suggest that they arent designed or made with bashing into an F8 - 9 in mind, as opposed to turning off the wind and riding easier.
 
As others have said. Bear away a bit and have some main up to soften the motion.

However, two weeks ago I was leaving Fecamp in a SW F6 with a deeply reefed main in readiness to free off as described. The entrance to the channel is narrow and the wind/waves were effectively on the nose - with no room to change direction. The boat slammed as you describe and the mainsail ripped! Now, the mainsail was old and needed replacing and was already in a poor state - so this is unlikely to happen to many. It does however illustrate the potentially destructive nature of 7T of fibreglass coming to a dead stop in a wave trough...
 
Yes, as said previously sailing over the waves at an angle will have the effect of lengthening the wave and matching the wave curve to the shape of your hull with a smoother ride, not necessarily directly where you wish to go, but certainly being more kindly to hull and crew.
The shorter chop waves and the flatter sections forward of modern hulls, plus the plumb bow, are a mismatch going to windward, but perfect for offwind speed and stability; older designs with longer ends, deep long keels and pointed bows cushioned waves, but still gets you wet .

ianat182
 
Damage to the structure from slamming is fairly common, and one of the things that surveyors look for during the survey. Theres been some good advice from the guys about sailing to minimise the slamming, and I took note of it because I also slam through with the engine on when I just want to get home out of the bad weather
 
Are you bull****ting, trolling or just foolish

When motoring against the wind my Jeanneau 39i slams... Recently I did that in a F7-F8 crossing from Biscay...

Could you perhaps explain why?

If you just wanted to damage the boat, then surely a sledge hammer would be quicker. If you wanted the pain and suffering, then standing under a cold shower whilst wedging match sticks under your finger nails would be more efficient and not oblige others to share the grief.

I note several posts suggest sailing off the wind/seas by twenty degrees; good advice, but in addition, why not also look at the weather forecast before setting off. 'Recently' suggests you've endured this escapade during the summer? FFS, there haven't been that many days when it's blown F7-F8, so why were you even out there?
 
Had the same slamming issue with a chartered Sun Fizz in Turkey. We found the best solution was to steer up the front face of the wave then turn on the crest to "slalom" down the back, in a sort of zig-zag.. It avoiding most of the slamming when we got the timing right :o
 
tortoise said:
When motoring against the wind my Jeanneau 39i slams throught the waves falling with a loud bang. Recently I did that in a F7-F8 crossing from Biscay. Some slams were very worrying with the whole yacht badly shaking.
Do I have to be concerned about structural damage? How much slamming can a yacht take?
Click to expand...

You seem to have been told off enough for what you did, so back to what you should now do.

One man's slam is another's slight bump, so it is not really possible for anyone to give advice to you on what damage you have done.

Perhaps the safest thing to do is to have a surveyor spend a short time looking at the boat. You will then have peace of mind and the knowledge that, when the boat is sold and surveyed, you do not have any nasty surprises stored up. I certainly would.
 
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