Nearly had an accident, but why?

M

Mullberry

New member
Long time reader, first time poster............I've always enjoyed the C-Brat site and its knowledgeable owners. I've spent years on the water, but only recently on a C-Dory. Until recently my experience has been with the displacement and deep V variety.

Yesterday, a friend and I went looking for Winter kings. Although we were unsuccessful, it was beautiful out, the weather calm, and the seas flat. On the way home we decided to see if we could coax the 1983 16' Angler up to 30 mph. We were successful, but a few moments later the boat began to gently bounce/porpoise up and down. All of a sudden, the bow grabbed, the boat heeled hard to stbd, and rolled down on it's port side. It felt like what would happen if you were travelling at 25 mph in the 12 o'clock direction, picked the boat up and aimed it 10 degrees from the line of travel (towards 1 o'clock), lowered the port side, and then while still travelling 25 mph lowered the boat back into the water. It grabbed, we banked very hard to Stbd, and the boat leaned hard down on it's port side. The Captain quickly reduced the throttle and we righted, but had 5 or so gallons of water on the deck where it had come in over the gunnel.

Now the question, why did the boat respond in such a manner? Clearly we were travelling too fast, but does that mean there is a maximum speed regardless of the water conditions? My guess is that the Captain had trimmed the bow down too much in an attempt to gain speed and with the old hull style, when the bow grabs off center, it moves the boat aggressively/quickly in that direction. A new semi-V hull may not respond in such a manner. In fact the Captain owned a Toland 18-8 for many years and stated he had never seen that in his boat.

Your opinions and thoughts on this would be appreciated so that I may avoid such unpleasantness in the future. Thanks.
 
I'm certainly not an expert in hydro-dynamics, but it sounds as though the speed started the porpoising, and the aft of the boat unloaded, allowing the bow to do the steering (however unintentional). With the bow dragging down, it would drive the aft even higher and any catch of the chine would cause that roll. Not so different from burying the bow on one side of a multihull, often causing a capsize.

Sounds to me like you were fortunate to only have 5 gallons of seawater to clean out (and your skivvies :shock: ). I guess you found the outside edge... probably best not to push that again. :wink:

Best wishes,
Jim B.

PS - Welcome aboard!
 
With a boat without any v and no keel you have nothing keeping the boat straight. Its like a snow board, it will slide sideways on the bottom until it catches a edge. what you did was catch that edge, then you bow steered. The bucking ride happens if you have to much or not enough trim down on the motor. adjust the motor trim and it will stop.
 
My humble opinion follows: Usually the most speed can be had with the bow trimmed (up), and that can lead to porpoising. Hard steering, less speed, and bow digging in usually is the result of bow trimmed (down), but rarely, if ever, results in porpoising. I think that the porpoising brought the bow down so hard as to have it catch the keel or chine forcing the boat to the side. This same thing can happen if you are following a boat and try to cross the wake -- you catch some air and then the bow of the boat hits hard after you've crossed, and tries to go in the direction it is pointed when the boat digs in.
 
Mullberry,

Welcome to the board.

I think you discovered the upper speed limit of stability for your boat.

Every hull form has a top speed, that when exceeded, causes instability.

Porpoising can be caused by fore and aft rocker in the hull or too much trim out on the motor.
 
Sorry to hear about your wild ride. My knee jerk reaction was that your boat is overpowered. As others have described, a boat will definitely make a dramatic change in direction if you plant the bow like that and with the engine possibly out of the water (i.e. purposing) and no sort of keel there was nothing aft to keep it straight. I have had similar reactions in boats when the bow has planted (though not at such a high rate of speed).

Glad to hear no one was hurt or vessel damaged. Also, it is bow up that will allow for more speed, bow down will definitely reduce max speed.
 
When accelerating in my race jet boat the trim nozzle is down to keep the hull in the water, but when up on a plane the trim nozzle is trimmed up till the bouncing stops. To much lift just cuts speed.

So yes your hull was trimmed down to much for the speed and yes your bow caught and changed your direction and lucky you are that your boat did not roll. Maybe your lucky our boats top out at 30.

I have both trim plates and twins. The trim plates help run level and the motor lifts I use for trim. My motors are pinched down tight when getting underway and then I lift them to elevate the hull when cruising. To much lift though will cut speed and you do not want your motor sucking air.

You want to be driving smooth at speed. Any bouncing should be immediately adjusted out thru either reduced speed or trim. And if trim doesn't fix it then slow down.
 
I have done the same thing when experimenting with trim tabs at a much lower speed. You can actually steer with trim tabs simply by lowering the bow on one side or the other. Based on what you saw, you may have experienced a situation where the boat was out of trim port and starboard. As your speed goes up the effectiveness of any trim tabs increases. If someone was working the trim tabs while going fast and didn't do the same thing at the same time to both tabs, then the bow could dive and the boat veer off toward the side with the low bow.
 
Thanks to all for the responses.

Yes, we were going too fast for sure! The Angler has a 40 hp Yamaha, so the boat is not overpowered, but also wasn't smartly driven. The more I reflect on the incident the more I am convinced that the port chine dug into the water and we "caught the edge".

Just in confirmation, to avoid that in the future, I should trim the bow up correct? Will this alone avoid the problem or must I also slow down? I'm not opposed to slowing down, just trying to determine the proper way to operate this boat.

Thanks again.
 
I had that problem with my 22 Cruiser with twin 45's on it. Just not a comfortable feeling. The permatrim will help you as will a moderate speed.

Charlie
 
Not being on the boat, all I can do is speculate. We have all experienced the effects even smaller swells can have in those instances where the bow lands in a valley just in front of a swell. This was a collision of factors to watch out for even in my Arima with its deep V hull. You could be flying along one minute and then if you take your eyes off the next few swells and fail to power down prior to landing in a hole, the bow would go through the swell. In summer this was a nice way to cool off, but you always wanted everyone to be forewarned.
Anyway, I suspect that your event came from a combination of factors which amplified how low the nose went. Even modest rollers taken slightly from the side would have created a water mass for the chine to dig into and turn on. Being out of trim as pointed out above would also add to the other factors detailed here. On a boat that size, if a passenger moves from one side of the boat to the other that can be all that is needed to cause a major change in how the boat reacts. When running hard in my Arima, I would always instruct passengers to give a heads up prior to moving from side to side.
 
I believe your bow caused the turn and your chine caused the roll.
Thirty is not to fast if the boat is handling properly, When ever the boat is misbehaving you should correct it before you add more speed.
 
Although some boats go faster, generally about 30 is the limit for these boats with out some handling problems. Normally "Chine walking" is found in V hull boats. Also purposing can be related to a "hook" in the bottom--that is the bottom not being completely straight--a little sag on the transom in relation to the rest of the boat. The boats have a slight amount of "rocker"--that is curvature fore and aft. But there should not be a downward hook in front of the transom. If this is present-it can be caused by lack of support in the aft 2 to 3 feet of the boat.

The bow steering is often brought on by surfing down swells, and then digging the bow--trim tabs can make this worse--as can engine cavitation plate fins--but they can also help to correct the problem. Some boats add trim tabs because of the purposing--and then cause bow steering--which is more dangerous.

Glad that there was no injury or capsize.
 
Captains Cat":1ju3wg7i said:
The permatrim will help you as will a moderate speed.

Charlie
Click to expand...

I totally agree, a Permatrim will most likely eliminate your boats tendency to porpoise.
My 22 with 90 Honda would porpoise easily, but after installing the Permatrim you can’t make it porpoise now.
 
It is interesting! I never had any porpoising until I added the permatrim. On flat water and wot if I trim bow up the boat will start porpoising. I have been thinking this may be due to my motor being mounted a little low for the permatrim, but not sure.

With the permatrim I can trim the bow up much higher than with the original plastic whale-tail. Also, on flat water I will get the best top speed with the bow trimmed down with the motor and the trim tabs.

Steve
 
I understand the term porpoising and how it would be a problem.

Please correct me if I am wrong, but the solution to porpoising would be too just slow down or lower trim tabs equally on both sides at the same time, right?

Could somebody please explain the term 'bow steer' and describe the symptoms and best solution.

The amount of info that can be found on this site is simply incredible and the interactive nature of extending the thread and getting input from so many knowledgable folks only makes it all that much sweeter.

Tanks,
Dan
 
The 16' Angler in the incident does have a permatrim.

I used the term porpoising and am not sure if I used it correctly. The boat began a smooth gentle bouncing up and down (similar to what would it would feel like if you were running over 3" swells).

I stated we trimmed the bow down to gain speed and it seemed as if many C-Brats thought you would trim the bow up to gain speed. I don't know which is typically more accurate, but I do know that when we trimmed the bow down, we gained about 1 mph on my GPS. We did this because we thought a "flatter" attack on the water was more efficient than "pushing" the water with the bow trimmed up. You tell me.....

Still looking to avoid this in the future and am sure I can do it by slowing down and that may be the answer, but I was curious if I didn't trim the bow down do I still run the risk of the same event?

Thanks for the info.
 
Mullberry,

Could you describe the 16 Angler?

It is a flat bottom 1983, right? How much horsepower and what engine does it have?

How would you describe the loading? You said two people, but how much fuel, fishing gear, water and so on?

Before you trimmed the bow down, how far back on the hull was the water breaking(spraying out to the sides)?
 
Mull, we all keep talking about trim up or down but we dont ask " down from where" at any planing speed to much or to little trim is going to slow the boat down. put to much bow in the water and you slow down, get the bow out to much and the stern down to much and you slow down. At some point you will hit the best angle of attack and make your best speed. and at some other point you will loose track and slide all over the place or buck up and down.
 
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