Bow steering, broaching, and trim tabs

B

BillE

New member
I am starting this thread to discuss an incident which I witnessed last October at the Apalachicola gathering. Tom and Joyce graciously invited my wife and I for a cruise up river on C-Otter, a C-25 and we were joined by Rusty and Jo Ann along with their other guests on Una Mas, a Venture 23.
While cruising along at around 24 knots or so I look over and suddenly Una Mas makes a very sharp turn to Port, almost into the path of another oncoming boat. Later talking to Rusty he said that one of his guests had suddenly shifted position and he indicated that with his trim tab setting and speed that the passenger's movement caused the bow to dig in, rolling the boat hard over onto it's side and tossing his passengers and belongings around the cabin. Fortunately nobody was injured, but all aboard were pretty shook up, as it happened very quickly. They said that the boat felt like it was going to capsize. From the outside it just looked like the boat made a very sharp turn, then suddenly stopped.

Well, this was my first and only ride on a C-Dory, and Tom and Joyce gave us a wonderful trip, but that incident has made a lasting impression on both of us, as the chance for injury seemed very high, so I was wondering if anyone else has experienced such a thing, and if so, was it related to the trim tabs?
 
Hey Bill and Sherry,

I can only surmise what happened, but it most likely was not just the trim tabs but a combination of factors.

I was a passenger on a Sea Ox 22 (if memory serves me correctly) outfitted with trim tabs. The operator had the boat "trimmed" out for speed and running full throttle. We came over one wave, the bow dug in the next and like you we went to port. I found myself in midair and then landed in the cabin as the boat had drastically slowed down.

I don't have trim tabs on my CD 16 but do use Dolfins and if trimmed improperly it too will bow steer, especially coming off another boat's wake or while running with the seas.

Hope this helps a little. There are a number of folks on here with a lot of experience and hopefully they'll weigh in.

Take care and be safe.
Remember, there are old coxswains and bold coxswains but there are no old bold coxswains.
 
IMO it is only related to trim tabs in that tabs bring the bow down increasing the chances that the bow will dig in and steer.

I have had bow steer occur on my boat a number of times, although not to the degree described by the OP. In most cases it results in the boat developing a bit of a lean while it turns. The lean is not severe enough to dislodge things in the cabin, but it is enough to get your attention (although my wife does not seem to notice). The biggest concern to me is that when this occurs, there is little to no helm control until the bow releases. The lack of control is unnerving.

IME experience, this usually happens in rougher conditions when crossing the predominant waves at a low angle (more parallel than perpendicular). When coming down the wave and picking up the next, the bow can grab while the stern is still on or over the top of the previous one. It can also occur with larger wake encounters. Surfing down waves at a good angle to the face also increases the chances of bow steer.

Unfortunately when traveling in rougher conditions is just the time you want the bow down to smooth the ride. The options to reduce the chances of bow steer are to raise the bow, slow down, and/or change the angle to the incoming waves.

Also, I have found that the CD-22 is fairly sensitive to lateral changes in load. Sometimes someone moving from one side of the boat to the other can cause a surprising change in lateral trim if I am not anticipating it, even on flat water.
 
In smooth water, which I assume this was during the gathering, if you set the trim tabs and engine down too much, you can get bow down and any sudden movement could cause this issue. I see many c Dory's being run in too bow down an attitude often. It is up to the skipper to be sure that the trim is proper. I ask my wife (we rarely have guests, but often our boat is heavily loaded), to let me know if she is going from one side to the other.

This is not unique to C Dory's. Any boat can behave in this manor if planing and bow down.

The going down waves and seas is a completely different matter. You should trim bow up--and have one hand on the throttle, the other on the wheel, if running fast in heavy seas down waves.

In the offshore power racing boats, there is one man assigned to the throttles and trim and another to the helm. It is that important.

I have never experienced what I considered a dangerous heel, or broach in a c Dory--but my with my sailing background, a sudden heel is something accepted are more likely under certain circumstances. I have found the c Dory to be one of the best boats, when properly trimmed for going down wind / seas in heavy conditions--far better than a deep V or semi displacement boat.

I would not be put off from buying a C Dory by this experience. Take it as a learning experience, Watch the trim, be sure you are not too much bow down, and always be aware of what is happening on your boat, and the sea conditions. It is certainly possible with other boats around, that there was a wake involved.
 
Yes, I've had something similar happen on the 22. I also ask my wife to let me know if she needs to move from one side of the cabin to the other. I tend not to dig the nose down too far, but you can read other threads where folks talk about trimming the nose down in chop. You can't win... :cry: Just be alert. Colby
 
BillE":23kiuxh7 said:
I am starting this thread to discuss an incident which I witnessed last October at the Apalachicola gathering. Tom and Joyce graciously invited my wife and I for a cruise up river on C-Otter, a C-25 and we were joined by Rusty and Jo Ann along with their other guests on Una Mas, a Venture 23.
While cruising along at around 24 knots or so I look over and suddenly Una Mas makes a very sharp turn to Port, almost into the path of another oncoming boat. Later talking to Rusty he said that one of his guests had suddenly shifted position and he indicated that with his trim tab setting and speed that the passenger's movement caused the bow to dig in, rolling the boat hard over onto it's side and tossing his passengers and belongings around the cabin. Fortunately nobody was injured, but all aboard were pretty shook up, as it happened very quickly. They said that the boat felt like it was going to capsize. From the outside it just looked like the boat made a very sharp turn, then suddenly stopped.

Well, this was my first and only ride on a C-Dory, and Tom and Joyce gave us a wonderful trip, but that incident has made a lasting impression on both of us, as the chance for injury seemed very high, so I was wondering if anyone else has experienced such a thing, and if so, was it related to the trim tabs?
Click to expand...

Sit down & stay put!! :roll: is the rule in my boat.
I have been in the same circumstance on 30' day cruisers, defiantly not a C-Dory issue. There is a learning curve with any type of vessel or equipment for that matter :beer
Good luck!!
 
For river cruising, where there is chop/swell, what are the indicators that you have too much trim and the bow is too far down? I assume it's all from experience and you just "know".

I'm just getting back into boating after 20 years off, and could use any wisdom.
 
We feel it sometimes on nearly every boat we have owned. Too much forward trim and usually wakes from other boats catching the bow and forcing a turn. It is not hard to avoid with attention to trim and passenger awareness of said trim. I would say that many boaters are encouraged by speed and eagerness to run with the trim a little bow heavy and that sets them up for the behavior. We see it as annoying and attention getting but never feel like it throws us around or poses a danger to how we boat. It alarms Cindie sometimes but I think she is past worrying about the boat rolling over.

Greg
 
We experienced something similar after installing Permatrim on our boat, we don't have trim tabs. Running fairly fast, trimmed way down, on the Willamette River, I turned quickly to avoid a snag. The boat dug in and slowed rapidly. We were not thrown around, but it was instructional in a big way.

My opinion is that it's experience and caution that will help keep you out of the situation. Emphasis on caution... Watch your speed and trim position regardless if using tabs, an engine plate or both.
 
I've posted this before as an example of a boating accident that was no accident. It is an example of "bow steer" caused by a lack of skill and intelligence.

https://www.youtube.com/watch?v=DQpq1_pfIgk

Obviously not a situation where trim tabs are the solution. Hard to say if the skipper didn't know or didn't care. He doesn't even glance around to see if his passengers are secure. Tough way to learn a lesson. And it won't do him any good because I assume that, with this footage on TV and the internet, his license was revoked.

Probably every type of vehicle can go too fast for certain conditions. When I'm on plane at 25 mph, it is the same feeling as towing my boat at 75 mph. All is well as long as it's smooth sailing, so to speak. But I feel like a long-tailed cat in a rocking chair factory.

Mark
 
Marco Flamingo":32uko4wu said:
I've posted this before as an example of a boating accident that was no accident. It is an example of "bow steer" caused by a lack of skill and intelligence.

https://www.youtube.com/watch?v=DQpq1_pfIgk

Obviously not a situation where trim tabs are the solution. Hard to say if the skipper didn't know or didn't care. He doesn't even glance around to see if his passengers are secure. Tough way to learn a lesson. And it won't do him any good because I assume that, with this footage on TV and the internet, his license was revoked. .....
Click to expand...

Yes the driver was an idiot. Doubt he had a license, likely not required. Usually all that is required is a boater education card and I don't think there is any way to revoke those.

From the video it looks like the boat actually went airborne and was developing a roll as it went through the air. The upset came when it hit the water again at an angle to its speed vector (maybe with bow steer). Other reports on this incident say the boat was going very fast (>50 mph).

This is a different situation than described in the original post where you are basically minding your own business and the boat decides to make a hard turn on its own.
 
Agree with ssobol. Back when this first appeared --and it probably was on another site--there was an analysis. The boat was going well over 50 MPH, and hit a wake. May have been a "hold my beer-watch this"... The skipper has one hand on the throttles, and the other on the wheel. He anticipates the issue by pulling back the throttles, and then hits them again--not sure if this was a reflex, or intentional. Always hard to know exactly how the boat is trimmed, but from the attitude and background, I suspect pretty well bow up--

Certainly use of the throttles will help--or make it worse--as it did in this case.

I have seen videos of similar accidents from outside the boat--and hitting wakes is the most common cause of this type of accident.

With the C Dory or most monohulls one has to be very cautious in this type of approach to a wake. The cats handle this far better--but again you have to keep the bow up.

As to river chop--often this is steep with wind against current. Yes, it is experience--but you can tell if the bow is down too much, the boat will start to tend to dig in. If it feels unstable--it is unstable...and sudden motion of a passenger will not be good. When you are going parallel with the seas, it is more likely to cause a roll, as is going down wind/seas. But there you trim bow up.
 
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