simple terminology
good ferry explanation, Pete.
Course- Point A to Point B. easily identified on a chart or map.
Heading- direction that your vessel is ‘headed’ or pointed. On a ferry angle this would be the difference between your course and where you need to point to compensate.
Bearing- the direction to an object
Totally agree on the ‘just do it’ philosophy. I was out in the Columbia last night in the moonlight in 2 knots of current having a blast. Something about a cold, solo night paddle that sets your head straight!
steve
don’t get too
hung up on the MATH. Kayak navigation is based way more on seat of the pants flying then math equations. I teach nav in the San Juan islands, one of the most choice ‘current’ locations around and I try and get the students to understand it’s NOT about numbers, it’s about observations and options.
steve
Yep, neutral balanced hull
Flatpick wrote, “The whole business of boat ferry angles relative to current are even more involved and complicated than wind. This is even more reason to have a neutral, balanced hull. IMNSHO.”
Yep, I think you achieved it in the T180. After the trip on Alsea bay, I was thinking, “I can’t believe I didn’t have more trouble out there,” given my lack of experience, high currents, no rudder. Steering was neutral though in every direction around the bay in various currents and wave directions, except for that one condition described where I should have had the skeg up. As already discussed, I need to use the skeg to trim steering where needed, rather than to add stability in confused waves, especially where the two settings would contradict each other (down for added stability, up for neutral steering). That will come as I get more comfortable in the waves :^).
Paul S.
On the contrary
"But I thought I’ve read about rudders (especially) and skegs being handy when paddling long distances in certain directions relative to CURRENT, not just in wind? No truth to that apparently, at least in a uniform current. Good, one less thing for me to worry about!"
Rudders and skegs ARE useful as they change the boat’s orientation relative to the water. This allows you to comfortably paddle at the proper ferry angle to compensate for the current.
Rudder obviously, but skeg?
Skegs don’t “change the boat’s orientation relative to the water”.
Skegs, when used for their intended purpose, only affect weatherhelm which lets you more easiliy hold course in various wind angles - and can also sometimes be used less correctly to stiffen up the tracking and stabilize the stern a bit in chop.
A skeg will help you maintain ferry angle realtive to wind - but not current (unless you can’t paddle in a straight line without one) as it has no steering component.
wait a minute
why wouldn’t the skeg change the relationship the hull has to current. When deployed the stern has more bite and will be affected more by current. This will drastically change it’s orientation to said current.
Skegs effectively change the pivot point of a hull. wind or current, the hull will be affected by a skeg deployment.
steve
Fisherman logic
Perhaps your high school teacher never wanted to sit in one place and fish for a while. My “outside frame of reference” would be an anchor, given the river wasn’t too deep to reach bottom or the current too great to be practical. In the latter case, the anchor dragging would still give reference to current direction (keep your knife at the ready.) Maybe at times I try to get too simple.
Taj K.I.S.S.
Only during transistions
in and out of currents, eddies, etc. Otherwise the forces are the same accross the hull - it sweeps you along, but imparts NO turning forces unless one end of the kayak is in faster water than the other.
As others have already said - when fully in a current you are completely in it and move with it. The hull will respond the same as in still water. You and the current will be moving relative to land, but the current will act evenly on all parts of your kayak (including a skeg OR rudder).
Skegs compenstate for wind. They will not really help maintan a cross current ferry angle, nor are they needed for that. See other post on course in currents.
Course in currents (vectors, etc.)
– Last Updated: Jan-05-04 11:45 PM EST –
(As in manitaining a course - not taking one)
Vector example:
You are paddling 090 degrees at 4 kts (speed through the water). You are in a current going 360 degrees at 2 kts. Your actual course and speed (over ground/chart) resulting from both motions would be 063 degrees at 4.47 KTS.
Great if you want to be going to a point on a bearing 063. If you really want to end up going 090 you'd need to head about 30 degrees into the current (heading 120 degree) and would lose some speed as your 4 knots paddling speed will now get you 3.46 knots toward 090.
Simple right? Easiest to do on paper/chart with a ruler to mark course and speeds (yours and the currents) creating a current triangle to show set and drift - or just a box to show resultant vector. Pictures are easier than formulas. But on the water things constantly change and plots aren't that practical.
To do this vector stuff by the seat of the pants you'd paddle to the E (the way you ultimately want to go), notice you are being pushed more to ENE, and compensate by paddling roughly the same amount to ESE to compensate (more if angling more against the current since you lose speed, less if angling more with it as you gain some). Visual landmarks for referrence or GPS is needed to pull this off. You can't compensate for what you can't see.
A very good description of natural ranges and drift as applied to kayaks (with animations) courtesy of Guillemot kayaks:
http://www.guillemot-kayaks.com/Technique/Range/
Some other vector/navigation stuff:
http://www.sailingusa.info/course_to_steer.htm
http://www.pa.uky.edu/~phy211/VecArith/index.html
my point is
how often are you fully ‘in it’ and paddling neutral to ‘it’?? While I fully understand the concept of moving along with the water, I find that 99.9% of the time I am on a contrary to the current course and my skeg (or lack of) has plenty effect on my hull performance.
How does the skeg know it’s only for windage use?? Have you ever done a strong ferry angle in 6-8 knots of current with and without a skeg? No friggin’ wind involved?
Dude, I paddle plenty of moving water to know exactly when my skeg is actively causing effect!
steve
What about
when waves are rolling counter to the current. Then the waves are holding the boat back and the current is exerting forces on the boat. That’s what I think was happening in the case I desribed here.
I think probably in practical terms there’s usually some amount of roughness on the water surface exerting forces on the boat independent of the current, which means the boat won’t be just moving along with the current.
Paul
oh yeah
wave energy and swell surfin’ will have a huge effect on your hull performance. The minute you bring the hull to any counter-current movement you will have a boat being affected in a NOT ‘drifting along with the current’ way.
I too think this could be what was going on with you at Alsea.
Paul- More of that icy east wind and we’ll be ice sailing on the Columbia! Cold down south??
steve
a skeg anchors the stern
– Last Updated: Jan-05-04 9:39 PM EST –
whether from wind or current. It's a high pressure low pressure thing, not what's causing it, if there is greater pressure at the bow with a current coming at an angle 45 degrees off from the bow to starboard your tail will skid, if you drop a skeg then your stern is more anchored and will not drift the way it does without. Wind has the same effect.
If skegs don't effect current why are they used on surf boards?
Narrower currents and eddies
transitions between different water speeds. I mentioned that. But if you are fully is a constant flow ther is no turning force to corerect, just a ferry angle to set (and reset as often as needed).
What?
If you are fully in the curent the is NO pressure difference on the hull from the current. Both you and the current are moving, and any added movement from paddling is relative to/in the current, not opposing it. The opposition is only apparent relative to a ground/chart position.
It’s like being on one of those moving walkways. If you built one 40 feet wide, and walked straight across it while moving, you would not really feel and twisting or angled forces. It would feel like yo walked in a straight line, which you did - relative to the walkway. To anyone not on the walkway - it would apear you were moving at and angle - which you also did relative to their position. You can’t experience both at the same time. You are either on or off the walkway. The only twist/wiggle/change of angular momentum you really notice in getting on and off.
Someone who surfs - please explain the function of fins and how surfing a wave face is not like traveling in a current to Kwikle. I know he doesn’t want to hear it from me.
Keith…
surfing a wave is not like walking on a moving 40’ walkway with fins.
The fin anchors the stern on the surfboard allowing the walkway to appear to be standing still.
steve
I think
your ideal example might be close with no waves or chop. But now to simulate the bay, put some waves and chop over your moving walkway that is moving endependent of your walk way. Or perhaps many sand bags hanging by strings moving over the walk way in directions independent of the walkway. (the sand bags are the waves) Now as you hit the continuous barrage of sand bags, you’ll feel the force and torqe of the walk way under you.
Paul
I could be wrong of course
but I would think putting the skeg down in current would trim the boat to point into the current. The current would pull the stern around because the fin in the water would be grabbed by the currrent. I think that’s what was happening to me in the example I gave. Following current was pulling the stern around, causing the boat to yaw to starboard. Not an anchor so much as a fin to be grabbed by the current.
I do agree about the skeg’s roll in anchoring the stern in wind, which would trim the boat to point down wind.
Paul
Way cold up here
The mules are out in the pasture with snow on their backs. I snigger a bit at the East Coasters when they mention cabin fever, but I’m starting to feel it myself. Gotta put chains on for two miles to get out of my little valley and down the hill, then take 'em off, then put 'em back on coming home. Pain in the arse. No work lately though. I went in today just in time to be sent home. Sitting around the 'puter too much lately. Oh well, could be worse.
Boy, Wade’s got some sweet pictures of your T180 in the snow though.
http://tinyurl.com/yqbbv
http://tinyurl.com/3xfak
next time you are surfing
your kayak, try it with the skeg down and with the skeg up and tell me there is no difference. That is the effect of current on your kayak with and without a skeg.