: Hi there, guys.

: So, which of these two shapes do you think will be better?

: Assume that: the areas and thickness of each are the same, the front end (at
: the right) point is the same location on the keel, both are adjustable,
: the leading and trailing edges are sharpened to blades, but most of the
: surfaces are flat rather than arced like an airplane wing.

: I'm betting (by actually building and installing them on Cohoes) that the
: longer unit will be more efficient because, a) its drag profile will be
: less, and b) by being longer from the same pivot point, it will move the
: center of lateral resistance more aft for all settings from none to full.

: Mike's idea of having the skeg near the middle of the boat then, according to
: this, should have little effect as it would be too near the center of
: lateral resistance to relocate it much.

that is correct for those criteria

: I sure hope Ross Leidy's new design program will be able to handle this kind
: of playing around... .

: Pete Roszyk,
: in Snohomish, WA

to my way of thinking, they are the same skeg. one is just larger than the other, or just deploys more. i assume that the ctr of area location is the same for both.

there are all kinds of criteria i sort of ponder to establish first so that one has a chance to objectively balance the tradeoffs between approaches. in your words so far it seems as if hydrodynamic efficiency at maximum deployment is the most important. if this is so, i would assume that a shape somewhat similar to those used for rowing shells or oc-1,2s would be the more close and therefore that would be the short deep skeg. my assumptions previously stated are that as you cannot deploy a skeg at greater than the small angles of attack of a kayak(unlike (shell, oc,k-1) rudders), that high aspect skegs would be the most efficient here. The tradeoff (other than the direct down dagger approach- and the dagger may best be a 'V' shape to keep the aspect consistent if hugely variable conditions) would be turbulence caused by the trunk.

just to state some of the criteria( no order) i think of when playing around w/ skeg designs:

-main usage situations - drag, or sideslip, or oversize for quick changes, or subtle only, low profile rounded(rocks) or not,
-or sea state(low waves - move farther back, make smaller therefore size and location)
-(and also, throw and throw location)
-strength and ability to take high side loads
-box volume - deployed non deployed
-sideplay or opening shaping to reduce (or not) jamming by sand/gravel
-direction of actuation
-type of actuation - rod, line, cable,
-actuation protection(lines, cables exposed to jamming, gear, exterior etc.)
-actuation throw or strength
-actuator type (knob, jam, foot - side or gas, knee)
-flexibility to be quickly removed, repaired while by yourself on the water
-or hidden for aesthetics or to reduce catching or for packing etc.
-lots of others.

anyway, going back to the beginning, my guess would be that the short deeper skeg would be successively more efficient on deployment

guesses only