Trim Question?

I have never played around much with trim and what it may accomplish. I started looking at the water mark left on the hull after a paddle and it’s making me think again. Looks like our Spirit II only has about 2" of bow in the water. On occasion the boat does not respond as it should and I don’t know if it is me in the stern or my strong bow paddler, the wind, or what. What should I expect out of sliding the bow seat forward (my wife has been using it all the way aft).



Tom

Trim can make a difference
Particularly in wind and current. In wind, the heavy end of the boat wants to point upwind. In current the water gets more grip on the deeper end of boat and will tend to want to take the deeper, presumably heavy, end downstream.



Play around with the trim options and see what you think.



~~Chip

The effect of current…

– Last Updated: May-13-08 11:10 AM EST –

...only matters when the current suddenly changes, like when your boat crosses eddylines. Turbulence in general will complicate boat-handling too for the same reason. However, if you've been in a steady current for more than a few seconds so inertia is no longer an issue, paddling and boat-handling are the same as if the water were still. Trim is always an issue when poling however, because now the boat is being held and propelled relative to the immovable river bottom, rather than being propelled by "gripping" the water in which the boat is drifting (this is analogous to the difference between flying like an airplane and flying like a kite).

Plop a big stick in the water - choose a stick that has a "big end" and a little end so it "should" act like a weather vane - and watch it drift downstream next to your boat for 10 minutes or so. It will just pivot randomly according to minor turbulence, but will not consistently point in any one direction. You can do the same thing yourself. Go swimming in a really big river at night, let yourself drift a few seconds and then just try to "feel" the current. If you are far enough from shore that your visual cues are not much good in the dark, you'll have no clue what the current is doing UNTIL your feet touch the bottom, and at that moment it will feel like you've stepped on a moving object, not on a stationary riverbed, because the whole time you have "felt" like you were swimming in completely still water.

Every once in a while I harp on this issue of paddling in moving water because it's very deceptive for many. Sea-kayakers who paddle in extremely fast tidal currents far from shore should understand this pretty well. Pilots seem to "get it" too.

Are you saying the bow is light?

– Last Updated: May-13-08 11:44 AM EST –

Since you didn't say how deep the stern sits in the water it's hard to say what's going on. If the bow is lighter than the stern, it will be more affected by the wind. Sometimes that's a good thing, like when going downwind. However, minor trim issues in a tandem boat are not nearly as important as in a solo with respect to the handling in wind, but still important with regard to efficient travel, especially at faster paddling speeds.

Trim makes a tremendous difference
If you are bow heavy, you will be battling to keep the boat straight.

If you are bow light, it will be tough to get the boat on plane and also on a windy day you will be fighting to keep it straight.



The best way to get a perfect trim is to float the boat in water with no one in it. Then measure up a inch or two from the water line and either put a piece of tape or make a line with a indelible marker on the stern and bow.

Then you and your partner sit in your places and have someone on shore take a look and see if there is approximately the same distance from the water to your mark at both the bow and stern.

If not you have to adjust the seat accordingly, and if you still can’t get it trim, you should either add weight or subtract some.



Another way is to take a small level and place it front to back on a flat surface on the floor of the canoe while you are both sitting in the boat and then adjust accordingly

I use both methods.



When just lilly dipping a little out of trim won’t hurt, but if you are a lot out and want to get from point A to point B in a hurry it will.



Cheers,

jackL


I may not be trim, but my hull must be!
This is a subject, about which much can be said. Briefly, for tripping in a tandem trim can be very important. If ya’ll are paddling many strokes per day for many days it can make a major difference in efficiency and we know, in the wilderness getting the biggest bang for the buck is important. My general rule of thumb is, level trim for forward or reverse travel. This means all dimensions but especially pitch and roll. For turning I prefer to change the trim by heeling. Generally, heeling in either direction will help a turn but heeling away from the turned side will result in a tighter, faster turn. HTH.

What you can expect

– Last Updated: May-13-08 12:00 PM EST –

- Sliding the bow slider forward... Your bow person will feel more cramped with a less comfortable paddling station. If you have a gear load, position that forward in the front bay before you engage the bow slider.
- Trimming the boat better will help whether it is the bow person overpowering you or whether it's a wind factor.
- Something else to consider... If you both are right handed (or both left handed) chances are very good that one of you is paddling on their strong side while the other is paddling on the weak side. Learn to paddle on both sides and switch occasionally to balance this out better, OR one of you will have to paddle stronger, OR find an opposite handed person to paddle with.
- If nothing seems to work the stern person should consider using a long narrow bladed paddle to give them more control.

But the stick doesn’t ferry
Agreed, that if the boat is at rest, moving or still water, trim makes no difference. However, I notice it is difficult to maintain the ferry angle when the deeper end (heavy) is upstream.



~~Chip

Level for trim indicator
I have glued in small levels on the bottom of my canoes to indicate trim without having to compare trim marks on the hull. I float the canoe empty and epoxy putty the level to the hull bottom adjusting it to read level in the empty canoe. Then when in the canoe all i have to do is look down to see the trim and adjust seats or gear till it reads level.

Bill

Try ferrying across a wide river, …
…rather than suddenly lunging into a stream of fast water. I did say that trim DOES matter when crossing eddylines or in turbulence in general. When you enter the current, the boat’s inertia causes it to remain relatively stationary relative to the current for a short while, and during that time the current streams by and you can take advantage of that during the “jet” portion of your ferry. On the other hand, if you ferry across a large enough stream that the boat’s inertia is overcome by the current, the boat itself no longer “feels” the current because it is drifting at the same speed. You still pick a ferry angle to get where you are going, but this time the water is streaming evenly along both sides of the boat, and the ferry angle serves only to balance the speed of downstreamn drift against paddling the direction the boat is aimed. This situation is just like an airplane or bird flying in a crosswind, it will be just like paddling in still water. When you lunge your boat out of an eddy and into a zone of fast water, the inertia of your boat “anchors” you in place much like the string of a kite causes the wind to blow against the fabric so that it lifts. Once that inertia is overcome, your boat is like a kite without a string because there’s no external force acting on it. Now, only paddle power comes into play, and ferrying is just like a plane flying in a crosswind.



Once inertia is out of the picture, you can paddle across the current at any angle and there will be no sideways force acting on your boat. Instead, the boat will move WITH the current, the same way as if you were walking across a wide conveyor belt. I’m rower besides a paddler, and even if I didn’t already know this (and even if my high-school physics teacher and college physics professor hadn’t drilled this into us one day (using the example of a boat in a current!)), I can see this principle by watching my wake on my local river which is as much as 1,000 feet wide. If I row on a constant heading, my wake is always straight behind me no matter what my angle to the current (the wake drifts with the current too, which illustrates that there is no water going sideways under the boat). If you could go out in the middle of the Mississippi river when it’s in flood and the current is rushing along at 6 or 7 mph, you could do all your normal calm-water moves out there and not feel a thing (other than those times when your boat crossed a boil), but the whole time you’d be drifting downstream.



Out on the open ocean, you could paddle crosswise to the fastest current that exists and not be flipped or even feel any force on your boat (that’s why mariners need to chart their progress relative to the stars or GPS - they can’t tell if they are in a crosscurrent or not just by observing their boat’s progress). Where things get tricky is when entering OR leaving a fast current, and you are subjected to a sudden change of current speed. Current is not a problem, but CHANGES in current are, and only then is trim a factor.



Hope that helps. This is soooo easy to explain with pictures, but that’s not an option here.


You better keep your eye on that level
prior to the 90 miler.

Some gremlin just might raise one end of it in the middle of the night.



Cheers,

JackL

Not on the level
Jack,

It could happen, there are varmints that come up North each year, and head back South with the geese. We keep a sharp eye on them and New York has an open season on Varmints. And every time i drop the canoe in the water i check the zero on the level.

The same Varmints that tamper with levels have been known to partially drill out the rivets on seat hardware in their competitors canoes. And wipe paddle grips with DEET.

They are sneaky devils them Southern Varmints.

Bill

The lowdown.
It does appear that the stern is 4" in the water vs the bows 2". Yes I know I need to shed some LBS! When we are moving along at a speed of 3.0 mph and above the canoe performs great. From about 2.0-3.0 I have a heck of a time making it go straight. I stopped paddling to see what happens and with the bow paddler working on the left, the canoe will go to the left. With only the stern paddler (me) paddling, my “J” strokes have no effect and I must use heavy correction strokes. Slipping through a creek at 1.0 it is flawless.



It seems that if the bow were deeper in the water it may help in tracking instead of just hanging there in the wind.



Tom