Handling a Large Wave

[Dora~Jean]

On the last Delta/SF Bay Extravaganza, we encountered an unusually large wave in the bay on our way to the Oakland estruary towards Jack London Square. A large container ship (without tug escorts) was heading out from that area aiming between the Oakland Bay bridge supports increasing its throttle and rate of speed considerably -- I'd deem it reckless for that much speed in a close situation. A small sailboat was trying to cross its bow (too close) while it was accelerating. We four were well away from it's bow about 1/4-1/2 mile away also crossing it's path but not in danger (as long as our engines didn't fail that is...). The tanker was also executing a fairly sharp turn during this acceleration.

That was the situation, now the results. The tanker generated a rather large, steep wave off it's stern, I'd estimate it at 6-8 ft trough to peak and maybe 20-25 ft between the 2-3 peaks. Couldn't really see this wave from a distance because it was mostly a trough rather than a tall wave. This is what the 4 boats did, which was the best?
a) Salty-C's CD22 (1st) hit the throttle and turned parallel to the wave.
b) Pounder CD22 (2nd) turned perpendicular to the wave and slowed way down.
c) Dora~Jean CD25 (3rd) turned to hit wave at a 45 deg angle and slowed way down.
d) Discovery TC255 (4th) followed Dora~Jean's approach and speed.

My opinion later tonight after you have a chance to digest...

[B~C]

I vote for slow and at a slight angle. It's pretty amazing the waves these boats can take at any angle, if you go slow. I about lost a few teeth in my last boat speeding over a freighters wake.....you just don't know how steep the back side of those are, and, if there is another one hiding right behind it.

[TyBoo]

I'd follow M/V Pounder anywhere! The car haulers going up the Columbia can make some mighty deep troughs. I like to nose into the swell pretty much straight on and slow. On the other hand, if I am running on step I guess I usually just slice through the swell at about 45º and throttle up/down as needed to smooth it out. The ground swells we get at the river mouth are a lot like that.

Every once in a while we'll get a steep ship wake while anchored that comes at the side, in which case we just hang on and enjoy the ride.

Anyhow - to answer your quiz, I would take (b) if I felt the concern was great enough to require more defensive action than normal.

[Sealife]

Absolutely take it at a 45 degree angle on the bow, with enough speed to get up and over the top without being thrown backwards. Oh, yeah, hold on, and fasten your seat belt. Taking it as Salty C's did is inviting a rollover, (hope they are alright). Taking it head on is safe also, but alot more violent.

[JamesTXSD]

"C" from this sailor-boy's perspective... OK, "D" is even better, 'cause you can see what the guy in front of you just did!

With a steep wave, such as that kind of wake, if you take it parallel, you run the risk of a broach. If you take it nose-on, you risk "falling off" the top of the wave, with a big "splat" and the possiblity that the bow will plow into the next wave in the trough. Thus, taking the wave at an angle, and slow enough to not "fall off" the crest would be my choice, riding down the back side and being able to see what's coming with the next wave/wake.

Since we don't have our CD-25 yet, I'd be delighted to know if this is the proper technique with this hull design. We've had plenty of experience with close steep waves due to the shallow water in the Gulf. The above has served us well, combined with the helmsman keeping a close watch on the wave action. What say you experienced C-Dory drivers?

Best wishes,
Jim B.
(who visited with Jeff from the factory today - and all is good with our production schedule! )

[DaveS]

What happened to "E"?......About Face, Full Speed Ahead!

[Sea Wolf]

I'm in with the C boys!

Sealife and James said it best, but several are right on.

Plus, with the 45 degree approach and adding some throttle, you may be able to find a low spot in the crest and pass through more easily where the wave is less steep, less high, and where you can better steer and control your course.

In really big sequential wind waves, working through them sequentially finding their less dangerous lower crests, gives you a safe approach to work your way up through the waves. Using the throttle when necessary is very important!

Periodically turning at 90 degrees to the other 45 degree course off the direct up wave face direction is a bit more dicey, but necessary to wind up going dead up toward the direction of the waves source, if that's your required course. Pick out a relative "flat" spot and go for it!

Fun topic! I miss sailboats!!!

Joe.

[TyBoo]

Ship wake is somewhat unique as compared to swells, rollers and waves. For one thing, it is a temporary condition, and after it is seen its behaviour can be quickly predicted. Salty C's approach may well be the best if he is far enough away and fast enough to actually outrun the swell. We do that a lot on the river when passing a ship by cutting to the outside of the "v" before getting to the actual swell and then running parallel to and faster than the swell. (Of course, if it's a Navy ship they don't like you angling toward it and overtaking, now do they!?!) Or even being passed in opposite directions if there is room to run outside of it until it has lost its force. The angle approach to go over it works well if you're already scooting along and have to go through it. When trolling we generally try to face right into it and let it roll through us.

The ground swells at the entrance are a different story because they don't let up or end. They just keep coming so usually straight up and over with constant throttle control is the only option because zig-zagging isn't always wise and the river usually has a fairly narrow line where the running is best so quartering can get you into worse conditions fast.

Interesting chat you started here.

[oldgrowth]

When I saw this post, I thought what a good test for me. I did not have time to answer right away and did not want to be influenced by the members with more knowledge and experience than me. I left this post up until I could answer and did not refresh my browser.

Just my gut feeling tells me to enter into the wave a little less than 45 degrees at a fast trolling speed. Just enough to have good control/steering speed and ride the wave down one side and up the other. 20 to 25’ between peaks with a 6 to 8’ troughs is not an overly steep wave and I believe the C-Dory could ride it without any difficulty as I suggested. You did not indicate there was any crest breaking so I assumed it was more like 8 by 20’ swells.

The members with more experience let me know if I lived or died. Maybe I will know when I post this because some one will have answered it.

[Salmon Slayer]

I also would go with C or D, I try and take most waves at an angle with any boat and as has been said previously, there is less violence that way.

Hope everyone was alright and no damage was done; I would also report this ship to the USCG because that type of maneuver and speed in a restricted area may have been illegal.

[Dora~Jean]

Wow, we have some real experience out there! I've been busy doing honey-do's for past few hours, then checked the one or two responses I expected to see...was I surprised -- and delighted! I've owned my CD-25 for 3 1/2 glorious years now, been through most seastates and a few very high wind situations, but nothing quite like this wave.

Let me say first of all, we all survived(!) and no damage to any of the boats that I'm aware of. It hadn't occurred to me or any of us though, what Salmon Slayer suggested, to report that boat, I really do believe it was questionably being handled in a safe manner. It may not have been a "large container ship", but a large ship it was, and looming larger when so up close and personal.

I observed Pounder in front of me hit that wave at a slow speed perpendicular to it, his boat shot up at a 45 deg angle then slammed down on the backside; Kathy and Jim were shaken, but after finding no damage were able to get a call out to the rest of us that they were OK.

I was next. Whenever possible I always try to hit large oncoming waves at 30-45 degs to maintain best control, steerage, reduce chance of broaching while trying not to go airborne with too perpendicular of an angle (especially unforgiving in shallow-bottom boats!). I buried the bow and starboard side then shot skyward on the face of the next wave, then slammed down the backside, but I'm sure not quite as violent as Pounder. The face of that inner wave hit hard and managed to dump some water through my side window that was foolishly open about 8 inches -- but then again, I had no idea the steepness and period of this wave. Only took on less than a quart or so, enough to dampen my pride (window open), but still, it hit the boat hard. I'm now in doubt that it is ideal to hit such a steep wave at a 30-45 deg off the bow because if you look at the shape in that area, it will hit the flat part of the hull transferring a LOT of energy to that portion. OTOH, hitting it direct softens the blow to the hull sides but takes it out on the bottom and superstructure when it pancakes down on the backside.

Discovery behind me, not much time to consider other options, hit at the same angle and speed. He reported water in his starboard window also -- made MY day that someone else had their window open! Again, not much time to think about it, the size and speed were upon us in seconds, had to go with instinct. I would be interested to hear his thoughts on his actions and if there was a better choice.

Now to Salty-C's, actually the first boat in the chain, but he chose a different action than any of us. I apologize in advance though, I didn't give you ALL the facts, but Tyboo Mike picked up on it. Salty-C's turned parallel, hit the throttle (full I think)...and continued to turn till slightly AWAY from the wave. He didn't have a lot of room before he would have run aground but just enough to skirt 'just' past the starting edge of the steepest part of the wave -- remember the ship was accelerating while turning towards us. His description of his action: "RUN LIKE A CHICKEN"!!!!! We all laughed at his comment, but seriously and in my opinion, he was absolutely correct and suffered the least impact from that wave in this situation. We all voted at the dock while sitting around sipping his favorite wine (chillable Red) that he was the winner!

Now I have some thinking to do. I'd like to try that wave hitting one of my stern quarters while judiciously working the throttle to allow it to pass under. The wave was not breaking at the time we hit it, but would in another 100-200 feet as it approached shallower water near shore. The question would have been whether I had the leeway to safely do it with the rocks so near. Out at sea, a rogue wave would more than likely be breaking, taking it on a rear quarter could swamp (poop) the boat or possibly kill the engines, neither a good situation. I'd probably go with the 30-45 deg bow-on angle in an open ocean situation.

Please, comments, this is an excellent discussion, well worthy for all of us.

[ffheap]

Hi Folks,

Dora~Jean wins. Salty C goes swimming.

Fred

[Jim Gibson]

Steve Dora-Jean;

This was an excellent discussion. Thanks for bringing it forward.

What we learned from Salty-Cs is that if it is possible given the situation, that it is not a bad idea to out-run a large near-by ship tidal wave to the end of its vector of force. Now this technique may not always work because of obstacles, rocks, and shore, but it certainly worked in this case.

We tip our hat to Sam on Salty-C-s.

[Larry H]

Good discussion,

I would choose turning 180 degrees (if there is room and time)and running in front of the wake. Then adjust course to run away from the wake at 90 degrees to the wave and slow enough for the wave to overtake the boat. The wave will pick up the stern and the boat starts to surf. Then slow down and the wave will slip under the boat and the boat slides down the backside of the wave. Repeat until the wake has gone.

By running with the wake, the relative speed of boat to wave is slow and controllable. Its also possible to angle off to one side or the other to have a lower part of the wave overtake the boat, or speed up to outrun a bad spot in the wake.

[1TUBERIDER]

Swell approaching a set of 3 or four waves I usually set up for the biggest, drop in late and crank a turn off the bottom then look for the tube.
I do this on my 10' er.

Swell approaching a set of 3 or 4 waves coming and I am doing 70 mph, I usually run parrell and on the last wave I turn a little into, so I get major air and then I am looking for the white water. I do this in my outlaw whitewater racer.

Swell approaching in my fishing boat, I slow down enough so that there is no hull bouncing usually quartering the swell. If you have trim tabs drop the bow down, maintain a safe speed (c dory hull will let you know when you are going to fast) after the swells pass raise the tabs and resume.

If you need more practice, get out of the bay, chose a windy day with 10' swell at 7 seconds. After a few hours of this, a ships wake is no problem (not that a wake cannot be dangerous). Make sure you leave a float plan.

Be safe, a boat that don't float won't get you back. My priorities underway are 1 safety of my boat so I can get crew back 2 safety of crew 3 safety of people not in my boat 4 safety of your boat.

Oh yeah were your life jackets on? Good luck

1tuberider