Ballast

[Don Hynes]

I own a 16’ C-Dory. Love the boat! But here in the San Juan Islands the currents can be fierce and the boat is light and easily “slides” with the tidal currents. I wonder if putting some ballast in the boat, a couple of 50 lb sand bags for instance, would help to stabilize. Any thoughts or experience out there?

 

[NORO LIM]

I own a 16’ C-Dory. Love the boat! But here in the San Juan Islands the currents can be fierce and the boat is light and easily “slides” with the tidal currents. I wonder if putting some ballast in the boat, a couple of 50 lb sand bags for instance, would help to stabilize. Any thoughts or experience out there?

Not sure what you mean by "slides" and "stabilize."

If you are talking about a boat moving with a current, weight isn't going to change much. Currents are like rivers or conveyor belts. Everything on them moves along at the same rate, absent some external force. The weight of the item really doesn't matter. If you are talking about being knocked about by waves, or by wind, then weight might make some difference in how the boat moves through the water, e.g., how susceptible the boat is to movement around one of its 3 axes (pitch, roll or yaw).

I think in most cases, weight distribution is more important than just more weight. Keep the weight as low as possible, and keep the boat in good trim. Also, of course, speed can make a huge difference in how the boat handles in a given set of conditions. Slowing down is often the best choice. These are shallow draft, light boats by design.

By the way, it's really edifying to watch a heavy, deep-keeled boat try to deal with layered currents - i.e., the bottom of the keel is being pushed one way and the hull at the water line is being push another. Sort of like trying to ride two conveyor belts at once. The Dent Rapids and the Devil's Hole come to mind.

 

[Don Hynes]

Thanks Bill. Our most common course is east or west across President’s Channel where the tidal current moves north or south. The ebb tide can be very strong, even on a windless day, and so to keep my bearing I have to make a lot of adjustments at the wheel to keep on course. I’m an experienced kayaker so I’m familiar with the phenomenon. I was just wondering whether a bit more weight low in the hull might help.

I may have used the term “sliding” in a misleading way. The boat, in a strong current, tends to follow the “conveyor belt” even though I want to run across it. I do slow down in those conditions as your recommend.

Thanks for the input.

 

[smckean (Tosca)]

As NORO LIM indicated, you may be misleading yourself.

Indeed the boat is going to follow a different course over the ground depending on what the currents might be doing; however, the boat itself knows nothing of this. All it knows is the water it is travelling thru. The boat will operate exactly the same whether the water is dead still or moving swiftly in any direction (the exception would be if the current is so fast that the flow becomes non-linear in whatever "basin" the water is contained in....that is, the water would then become turbulent).

Bottom line is that there is nothing you can do on or in the boat that will change anything relating to the current. OTOH, naturally you will have to modify your course, perhaps substantially, to make a waypoint on land since the current does affect how the boat travels over the land underneath the water (but again, the boat knows nothing of this).

 

[thataway]

Great advice--I agree 100%. Your 16 does not need ballast. Remember it is a 16 foot flat bottom boat. It handles better than many other 16' boats, but there are limits.

 

[Don Hynes]

Thanks Bob, Sandy. I've kayaked this waters for years and know the principle. Depending on the strength and direction of the current you adjust bearing to stay on course. For some reason, I guess being a relatively novice power boater, I didn't realize the same principle applies to my C-Dory. I appreciate the advice. Thank you.

 

[kcohen4]

I actually have a 16ft cruiser and have ballast.
My problem is when I am alone too much weight on the right side and the boat is not level. This causes a steering problem.
I put 3 25 pound weights under the passenger seat to almost level out the boat. Also keep the anchor and chain under the passenger seat.
When I have a second person on the boat seems to also be OK.
I have in the stern the battery on the right side and 2 6 gallon gas tanks on the left side. Not enough room to have the battery on the left side. After I put the ballast in the boat handled much better.

 

[Don Hynes]

Thanks for the input!

 

[ssobol]

Current affects big boats too. You should see the headings the Pt. Townsend/Keystone ferry in WA state can take to deal with the current coming in/out of the Sound to get across. Sometimes it looks like they are heading in completely the wrong direction.

 

[smckean (Tosca)]

Current affects big boats too.

With the exception of turbulent waters (such as the many "narrows" in the islands of BC, Canada), currents affect all objects in the water exactly the same. A huge freighter and a small stick floating the the water both have their progress over the ground changed by the exact same distance and in the exact same direction (i.e., the speed and direction of the current itself).

Think of it this way.....if a boat, or a freighter, or a stick were all together at rest in the water together in a thick fog, but the water was moving with a strong 5 knot current, no one could tell visually that situation as being any different than the same situation with zero current.

 

[NORO LIM]

. . .but the water was moving with a strong 5 knot current, no one could tell visually that situation as being any different than the same situation with zero current.

Except that in still air, you'd see pennants moving and feel a 5 knot wind - even see some ripples on the water. :lol: (Have to get your vector analysis going to calculate the perceived wind in other than still air.) But your point is exactly correct when you don't have a fixed visual reference such as a shoreline. You, your boat, and the current are one - a metaphor for life, no?

 

[smckean (Tosca)]

Except that in still air, you'd see pennants moving and feel a 5 knot wind.....

Hahahahahahahaha.....

You are absolutely correct! :wink: I was thinking "water" and "ground".....didn't think about "air"....which is, of course, also part of the system too.

You, your boat, and the current are one - a metaphor for life, no?

.....I love it!

 

[hardee]

OH yes, there is air, and water, and the boat is affected by the current by what is in the water . . . . so, if the surface of the water is agreeable, and you are crossing the direction of the flow of the water, IF you get as much of the boat out of the water, it will be affected less by that current right? SO, again, IF the surface of the water is agreeable (as in not to rough) get the boat up and out of the water -- yes, get up on plane, and get across that current. When I cross Juan de Fuca, IF the surface is agreeable, up on plane allows for less time for the current to force my boat out towards Japan or up onto the beach on Whidbey, so the boat is less affected, by both current and exposure time.

An example: Going through Deception Pass. Watch a 30 foot sailboat going through there and anything less than a full slack and you see a bunch of wiggle waggle. Then watch a 20 foot tin can boat, or a 22 C-Dory Cruiser go through at 15+ knots. No wiggle waggle there.

The momentum (and weight) of the faster boat (inertia created) will allow less effect by the cross currents.

(PS: I had a 15 foot Montgomery sailboat with 700# of ballast, and no that does not have the effect you are looking for.)

Harvey
SleepyC :moon

 

[NORO LIM]

". . .IF you get as much of the boat out of the water, it will be affected less by that current right? . . .

The momentum (and weight) of the faster boat (inertia created) will allow less effect by the cross currents."

I don't think so, Harvey. As long as the depth of the current exceeds the draft of the boat, it doesn't matter how high or low the boat is riding. (Does anything about your speed or direction of travel change if you stand on your tiptoes on a conveyor belt?) The effect of the current on the boat will be the same. Likewise, momentum and speed will not change how the current affects the boat. If you are thinking of turbulent water, or multi-layered cross currents, then draft and weight can matter.

Going faster across a current does mean the boat will spend less time being affected by the influence of the current, i.e., you will have to spend less time "crabbing" to keep making the best progress to some fixed point on the other side of the current, and you won't have to adjust your heading as much.

Trying to reduce the OP's original question to it's simplest components, I have been assuming he is asking about relatively flat water conditions with a current flowing across his desired direction of travel at a given speed. In that situation, I do not believe adding ballast to the boat will do anything to affect his need to make course corrections. If we start adding other factors, like wind or water turbulence, the problem gets more complex.