i want to add a skeg to my 17’ s&g greenland style (4 panel hull) kayak. options are to lop off 5" of the stern, add a vertical transom, and add a necky style drop skeg… or to add a skeg box behind the rear hatch. my question is about handling. what are the boat handling implications of the different skeg locations… one on the stern vs one half way between the stern and the seat. help!?!
put it a couple feet forward
A rudder or drop-skeg attached to the stern is prone to damage, hinders towing and rescues, and will come out of the water when the stern is lifted by following seas.
I’d definitely locate your skeg under the hull a little ways forward of the stern. I have no idea exactly where that should be located though. Maybe experiment with a duct taped skeg mock-up, to see how it handles in different positions.
that was my question
when I converted a ruddered kayak to skeg.
I did not know where to put exctly the skeg.
In the end I just put it soemwhere where I could still reach from the rear hatch hole.
http://gnarlydognews.blogspot.com/2009/02/shop-kayak-mods-fabricating-skeg-box.html
I had to work through the hatch to install it but it seems to be working great.
I believe that the further back (towards stern) the skeg is the more will be effective in correcting weathercocking but, as mentioned above, if too far back it might stick occasionally out of the water in heavy seas.
If the kayak weathercocks a lot than a bigger skeg blade is needed.
The kayak I modified needed only a small amount of correction (slight weathercock).
I did like Gnarlydog
and put my skeg far enough forward that I could install it through the hatch. It’s about 8 or 10 inches further forward than a stock skeg would be.
It stays in the water in all but the steepest seas, and corrects weathercocking every bit as good. What I have noticed is that I retain more maneuverability with the skeg deployed than a stock skeg, and it’s harder to force the boat to leecock by dropping the skeg all the way. But overall, I’m very happy with it where I installed it.
In my experience
– Last Updated: Mar-17-09 8:14 AM EST –
locating the skeg at the rear of kayak, it will be easier to get jammed from sand and gravel, will only help tracking in mild condition and it makes the kayak yaw in rear quartering waves. By placing the skeg closer towards the middle of the kayak you will be able to correct weathercocking, greatly reduce the problems with the skeg being jammed from sand or gravel and also reduce the yawing that occurs from rear quartering waves, giving you better control and less correction strokes. I still can't figure out why manufacturers still insist on placing a skeg at the rear of the kayak. Maybe they do it to for loading purposes only. Why not make a kayak that handles better.
If you have a maneuverable kayak, you can play around with taping a temporary skeg in different locations along the keeline and paddle in different conditions and see how the kayak handles.
Why would putting it farther forward…
…reduce jamming with sand/gravel? If anything, I would think it would make the problem worse, since you’d be sitting on the skeg more when doing beach launches. In a hull with any appreciable rocker, you’d have less contact with the beach with the skeg further aft.
what about implications for handling? nm
CLR
my understanding (translated from sailboats mostly) is that a skeg is designed to move the Center of Lateral Resistance (CLR) further aft. If a boat is pushed sideways through the water, it will pivot on it’s CLR.
To me it would follow that to get the same change in CLR you would need to use a larger skeg if it is placed 1 foot behind the cockpit, compared to one placed 3 feet behind the cockpit. Consider that inconjuction with the fact that the stern may be out of the water from time to time, and I figure that’s why most production boats have their skegs just a few feet forward of the stern.
i am wary of the slot
how much drag is involved. i remember to what lengths we went to seal off the slot in my 21’ sailboat, it had dacron ‘flaps’ along the centerboard case that closed the centerboard case slot…
Handling
Have had three boats with differences in skeg implementation, here are my observations:
CD Caribou, triangle skeg a bit closer to the seat than to the stern. Effective for tracking and weathercocking, only caused leecocking in really strong crosswind. Consequently whenever I used it there wasn’t any reason to not put it down all the way.
Impex Force 4, triangle skeg quite near the stern. This one really had leverage, could cause leecocking in even mild crosswind. For just tracking it really felt like the stern was locked side-to-side. With this one I spent much time fiddling with the deployment angle depending on the direction I wanted to go and the wind effects. And for any turning I wanted to raise it.
P&H Capella 167 (current boat), a rather smallish fin skeg, located about midway between stern and seat. Similar to Caribou in effectiveness, seems unable to cause leecocking. I don’t always deploy this one all the way though, since it’s more likely to collect weeds.
Personally, I prefer the more gentle effects of the first and last examples, they require less adjusting and allow reasonable turning ability even when in use.
Mike
Skegs and Tracking
In short boats the further the skeg is moved towards the rear, the stiffer the boat becomes, in other words it will want to track straight. Closer to the center of mass (under your butt, and the boat will be easier to turn (which is probably what you don’t want.) My long boat has the skeg very near the stern, it tracks like an arrow. The only experimenting I have done with moving fins around a lot is in surf kayaks which are between 7’6 inches and 9’ and are planing when the fins are important. A little experimenting will convince you why the big fins on a rocket are near the tail.
detachable mock-up
build a prototype to play with. Use a material that you can hack on (cut & trim) w/o difficulty. Doesn’t need to be pretty (at this point). A thin wood of any breed should work. Start w/ a triangle, say 3 to 4" deep & 9 to 10" long. Come up w/ a couple of nice elastic bands (blown bike inner-tubes works great) and attach towards the ends of your skeg w/ small wood screws. Tie the skeg to the aft of your boat in various locations to get a feel for it’s impact. Take it off, trim it down a bit, try it again. Takes away the ‘guess’ work.
If your boat is tracking well enough on all but the windiest of days, you may find that you’ll be quite happy w/ simple detachable skeg (nicer version of your prototype) that can simply be attached on the days you need it. Just a thought.
Todd
It’s hard to say…
…but there are many thousands of kayaks in use that have skegs and nobody is complaining about drag from the slot in the hull. When conditions are such that you need the skeg, it saves more energy than the drag it creates requires.