what's up with these 'inverted' strakes on Tarpon 160 SOT kayak?

http://www.ebay.com/itm/WILDERNESS-...831?pt=LH_DefaultDomain_0&hash=item565b4aa05f

One of the pics of bottom shows them.

I'm assuming they are both for strength and to help in tracking, and maybe to make the scupper holes work better.

I'm thinking the would improve tracking better if they projected past hull plane rather than inverted, but improve strength more as inverts.

I guess they also allow for minimum draft while still helping with tracking in deeper water.

Maybe they give decent tracking while allowing decent maneuverability, where as projecting strakes of same size would have the boat "nailed to the water" and much harder to turn, much less pivot?

I'm not really liking them for a boat like this that is supposed to be all about effortless fast cruising as I think they would come with considerable unnecessary drag. I've heard a rudder can add an extra 10% of drag and I'd imagine these are much more, and can't be retracted or removed. I think I'd rather have a perfect hull form and flip down skeg, even if it means extra weight of thicker hull or internal reinforcement (can they imbed a "T" of steel or aluminum in Rotomolded boat hulls?).


Any other reasons or boats beside SOT kayaks that use 'tunnels', beside tunnel props?

 

I would guess that they are there to stiffen the bottom.

 

Yes most likely to stiffen the hull. Probably slows down the boat a bit.

 

If this is the image it looks similar to one of my rotomolded kayaks, less the holes as it is not a SOT. The "corrugated" bottom stiffens the material, and seems to dramatically improve tracking on a very short kayak once it gets moving, presumably because of the extra edges. It tracks as well as my other kayak which is almost 3' longer and has a smooth bottom. As for speed, my hard-chine ply canoe leaves both of them in its wake . . .