Tips to reduce hull slamming when sailing to windward?

[rdubs]

Hi everyone
I have a 2013 SO469.  Just moved it to the Nassau in the Bahamas, keeping it at a marina during non-hurricane season and on the hard during hurricane season.  Due to both my wife and myself working, we will likely just keep our cruising to between the Abacos and the Exumas, so we aren't planning to do a full windward / south passage.  But nonetheless, there will be times when we will need to beat to windward against the trade winds.  A week ago we took the boat out and even in ~17 knot winds, the boat would occasionally slam against the waves.  Our kids are younger so I'd like to reduce the slamming.  Aside from turning to sail downwind, are there any tricks folks have found to reduce slamming? 

The slamming seems to come in batches of threes, so the wave action will be like:
Slap...slap...slap...slap....slap....SLAM...SLAM...SLAM...slap...slap....slap....slap...slap...
etc.

I've read that boats with flat bottoms ahead of the keel really are prone to slamming, but wondering if maybe keeping the front water tank more empty and the back water tank full would reduce the weight of the front end?  Right now my back water tank is empty and the front one fairly full.

Many thanks for any thoughts.
'Dubs

[jdl01]

Weight centred amidships is the best way to reduce hobby horsing - but your boat offers few opportunities to do this.
A lightened job is more prone to rise up - hence slam down. Keep your water forward.
One possibility is to modify your sail plan - carry more sail forward and reduce your main when the wind a seas get up.
This will help drive the bow down into the waves s opposed to bouncing over them.
Lastly, if the waves are not too tightly packed, use your helm. Steer up more into the face of the oncoming wave and drop off as it runs under the hull. This presents less surface area for the wave face to initially lift, reducing the height of the slam.
These hull designs are always going to slam around, but the above may help reduce it a little bit.

[zaphod]

While it is true that hull shape makes a boat more prone to slamming, good helmsmanship will minimize it. Going upwind in seas takes a lot of concentration, and constant course adjustments. Watch a few waves ahead, and for the bigger waves bear off and slide down the back of the wave rather than dropping off them. You will find that with a bit of practice you will maintain much better boatspeed, and less wear and tear on the boat. (Not to mention your nerves!)

[jdl01]

Apr 24, 2019 18:56:24 GMT zaphod said:

While it is true that hull shape makes a boat more prone to slamming, good helmsmanship will minimize it. Going upwind in seas takes a lot of concentration, and constant course adjustments. Watch a few waves ahead, and for the bigger waves bear off and slide down the back of the wave rather than dropping off them. You will find that with a bit of practice you will maintain much better boatspeed, and less wear and tear on the boat. (Not to mention your nerves!)

Good advice when sailing on a close reach, but if your are beating hard to weather to clear a headland, you will find that you are loosing ground.

[zaphod]

Apr 26, 2019 17:17:56 GMT jdl01 said:

Apr 24, 2019 18:56:24 GMT zaphod said:

While it is true that hull shape makes a boat more prone to slamming, good helmsmanship will minimize it. Going upwind in seas takes a lot of concentration, and constant course adjustments. Watch a few waves ahead, and for the bigger waves bear off and slide down the back of the wave rather than dropping off them. You will find that with a bit of practice you will maintain much better boatspeed, and less wear and tear on the boat. (Not to mention your nerves!)

Good advice when sailing on a close reach, but if your are beating hard to weather to clear a headland, you will find that you are loosing ground.

Not really. When you are sailing upwind in seas you can't just blindly point as high as you can. Every wave you slam slows you down, and the slower you go the less lift your keel generates. You can sail higher through the smaller waves, but when a bigger set comes you want to bear off a little for power anyway, so you time that bearing off for when you are sliding down the back side of the wave. It makes for a much smoother ride, and you will be going faster as well. The saying "you have to be smooth to be fast" applies as much to sailing as it does to race cars! A lesson I learned years ago was that you can't force a boat to point well. You have to focus on keeping the boat moving, and the pointing just happens!

Of course there are situations where the sea conditions are just generally unpleasant for upwind sailing. Tall steep waves generated by heavy currents, and waves coming from unpredictable angles may still result in some pounding. We are still sailing big fat cruising boats after all!

[chuckr]

We are not very good sailors but can only tell you what we have done. We have a Jeanneau DS40 and during out Atlantic crossing we spent 3 days in winds of 30-35k and seas in the 10-12++ and the boat wanted to run as we were about 50-60 deg on the wind. She was flying along but banging a lot so we just slowed her down.  We reefed to a handkerchief for the main and jib and we stopped the banging and maintained a speed of 5-5.5k - she just rode the seas. Later we had 2 days of wind that never varied between 26-28k and again big seas and we did it again and it worked great.

Just throughts from a couple of below average sailors.

[ChrisD]

Most boats tend to be fully powered up at around 12 knots of breeze. So any thing above this here would be to much sail, unless you are depowering through trim.

If the boats motion is aggressive and not smooth again this is an indication that there is to much sail up for the conditions.

If you are in similar conditions a reef in the main would achieve this learning when to put this in takes time, however as you sailing with family your first reef should be in by a steady breeze of 15 knots. The boats motion will be the best indicator.

Reefing moves the boats center of effort forward, helping to keep the bow down.

Remeber that a smooth boat is a fast boat.

[zaphod]

May 8, 2019 15:31:44 GMT chuckr said:

We are not very good sailors but can only tell you what we have done. We have a Jeanneau DS40 and during out Atlantic crossing we spent 3 days in winds of 30-35k and seas in the 10-12++ and the boat wanted to run as we were about 50-60 deg on the wind. She was flying along but banging a lot so we just slowed her down.  We reefed to a handkerchief for the main and jib and we stopped the banging and maintained a speed of 5-5.5k - she just rode the seas. Later we had 2 days of wind that never varied between 26-28k and again big seas and we did it again and it worked great.

Just throughts from a couple of below average sailors.

I sense a bit of false modesty here...I would guess that most of us have not crossed the Atlantic; I certainly haven't. Around here 25 kts is a gear buster for the racing fleets, and we don't see anything like those kind of seas. I am thinking that slowing the boat down to reduce the abuse on the boat and crew is the wisest thing to do in those conditions in the middle of the Atlantic.

Having said that, if I had my racing buddies on board I would love to push my 39i and see what she could do in those conditions!

[timeflies]

I agree with Zaphod. You cannot simply point as high as possible to clear a headland in a heavy sea. With waves, maintaining boat speed ( energy ) to offset leeway will pay back in spades. Increasing the twist on the main will also help to keep the boat on her feet while the helmsman drives up the wave face and bears away slightly at the top to reduce crashing into the next.

[jdl01]

At no point did I suggest that you "blindly point as high as you can". This was a straw man created to make some one else's point. The object was to reduce slamming while retaining course to the greatest degree possible. I suggested putting the bow into the wave and then dropping the helm to run more parallel to the wave as it passed the keel [midpoint on the hull}. This will reduce the drop distance of the bow as it lands on a higher point on the downside of the passing wave and thereby reduce [not eliminate] pounding while holding course to the greatest degree possible. After 67,000 miles of sailing, it still works for me.

[zaphod]

Oct 26, 2019 17:51:13 GMT jdl01 said:

At no point did I suggest that you "blindly point as high as you can". This was a straw man created to make some one else's point. The object was to reduce slamming while retaining course to the greatest degree possible. I suggested putting the bow into the wave and then dropping the helm to run more parallel to the wave as it passed the keel [midpoint on the hull}. This will reduce the drop distance of the bow as it lands on a higher point on the downside of the passing wave and thereby reduce [not eliminate] pounding while holding course to the greatest degree possible. After 67,000 miles of sailing, it still works for me.

Yes I believe that is pretty much what I was saying in my first post.

[jdl01]

Except that you seem to miss my point about initially driving up [possibly above your course line] into the wave face before putting the helm down. Try it out this winter in the Strait after a sustained NWer when the wave separation has extended.

[zaphod]

Nov 2, 2019 17:53:03 GMT jdl01 said:

Except that you seem to miss my point about initially driving up [possibly above your course line] into the wave face before putting the helm down. Try it out this winter in the Strait after a sustained NWer when the wave separation has extended.

I will try that and see how it works. I am still on the steep part of the learning curve on the new boat, although she is a lot more forgiving than my last boat. I can't say that I have had any problems with pounding so far though.