: some varied thoughts: i think a high aspect glider wing has less drag than a
: wide chord wing short wing of same area for a given effectiveness. the
: same thing can be seen in that the foils of hydrofoils are very high
: aspect. why continue to have more surface drag after already changing the
: water flow characteristic? But that would mean a long skinny skeg sticking
: out the bottom of the yak – more prone to breakage and harder to make. So
: to me, one reason that skegs are low aspect is that it has been easier to
: build them that way .

: i would include most(all?) cable and rod deployed skegs here. But here there
: is the added issue of deployment design. How can a rod/cable twist around
: say 90 deg and still work as a compression member? I haven’t seen one yet
: that addresses this issue and that’s why these typically move only in the
: region of 30deg deflection as the more deflection, the more likely kinked
: cable in pushout.

: { as an aside, in gregs design you see that at full deployment he has
: sacrificed a sig amount of potential area(the back cuts out) that could
: either reduce the total size or make it more effective. Hes also noted
: that by raising the skeg rear, that the actuation line angle is reduced.}

: the other reason is that often skeg pivot support is very small for lateral
: forces. you often hear of skeg 'humming or rattling' at speed. (some cases
: it can be just sideplay but has support). there is much less leverage on
: this joint if the leverarm (skeg) is not way out there. therefore the
: typical low deployment angle

: also often at this pivot point skegs are slotted or cut away in order to fit
: (not just gregs) over the pivot pin. This reduces the sideways strenght of
: the skeg itself to less than half what it could be right at the location
: it must be greatest. So don’t deploy too much or wiggle and snap.(or at
: sooner size for size)

: a different confounding issue at this point is that the designer has to
: preselect the amount of clearance betw skeg and box. And more importantly
: between skeg pivot area and box. What is the lateral area of support going
: to be in the region of the pivot?? You have to predecide. Big support –
: greater likelihood of sand/gravel jamming. Less – crappy wobbly skeg or
: high drag box . or vary?: does the skeg top stay wide for a wide pivot
: bushing and narrow blade. Etc, etc, etc. - I want full support, so the
: skeg will be a tight fit, but I know the compromise.

: looking at foil rudder effectivenss max at abt 7deg deployment(vs abt 12-15
: for non shaped(-saw a sealine display)) points out to me that lift plays a
: role in rudders. but skegs are always inline w/ the yak and if
: sideslipping even then the angle is real real low. so slightly(slightly)
: different issues. (there a lots of events when similar - like the
: conditions are variable inthe sea)like an unfoiled skeg has got to be a
: joke and how many of those do you see? want max effectiveness at low
: angles.

: to me the beauty of the skeg and retractable(fully) rudder is that you can
: vary the effect over the whole range of deployment from absolutely nothing
: to something. I would 'never'(bad word, i don't really mean never ever)
: want the skeg or rudder to be only partially retracted or folded. why,
: when the whole idea is variation? same with the amount of deployment. why
: have just enought to turn or go straight - i want as much as i can get -
: so i can play with it and use it in a whole variety of circumstances. if
: it's too much, big deal, i'll just retract it a bit and save it for later
: when i do.

: So using your example for the best of all worlds, supported pivot, long
: skinny skeg, deploy from a low aspect low area to min size you can or your
: yak bottom can live with ( I want nothing – fully retracted) to high as
: possible given the deployment system you choose.

: And you would have to give up most effective drag profile b/c it would be for
: only one speed/condition.

: Anyway some thoughts good or bad.

One thing I have noticed since I first started paddling with my retractable skeg is that I don't need to deploy as much of the skeg blade now. The issue with the blade size and shape depends more on the hull design. The skeg just moves the center of lateral resistance rearward. Typically you don't need a lot of surface area to accomplish that, say 20 square inches tops. The shape determines length of protrusion and more importantly, the linearity of the deployment. Say you have 3 inches of control range, if the useful range within that is only a 1/2 inch, then fine tuning the boats lateral resistance center will be all but impossible. If you calculate the surface area every 5 degrees you will see the rate of increase. The trick is figuring out how much you need and build your skeg blade around that figure. Ideally, I think a skeg that deloyed horizontally without using a pivot pin would work the best.

Greg