The Cobra drift rig

Before becoming a yak man, my favorite fishing was done on coastal streams in the Fall and Winter.  So, using my kayaks to access these waters seemed only natural.  Necessity being the mother that it is, Fall found me knee deep in the manufacture of a drift anchor for my Cobra Fish-n-Dive.

I leveraged off the groundwork laid by our brothers at NCKA, settling on a design similar in concept to the PVC anchor system by mickfish.   His design fit my needs to a T: Removable, non-penetrative and simple.  But, the strength of the structure and potential for drag and abrasion of the anchor line left room for improvisation.
Being that I'm a cheap bastard, the issue of strength was rendered mute when I found a piece of scrapped Unistrut P4100 (the flatter variety).  Sure it was a little heavy at 5lbs but it offered multiple ways of attaching hardware and was rated to over 1800lbs at 18 unbraced inches.  

Materials List:

~ 5 feet of Unistrut P4100
4x Stainless Screws with lockwashers and nuts
3x Stainless Eye bolts with lockwashers and nuts
1x Single wheel pulley

2x 2 inch J-bolts with large flat washers and nuts
1x 5 inch J-bolt with large 2 flat washers, 1 nut and 1 wingnut
2.5 x 4 piece of 1 closed cell foam

Power Drill

My 1st task was to cut two pieces from the unistrut.  A short piece which would act as a crossmember to counter the lever forces applied to the main strut and a longer piece that would bear the weight of the anchor and keep it far enough away so as to avoid contact with the kayak when not in use.  

Next, I notched and flattened one side of the crossmember creating a pocket that would receive the main strut. Then, I notched the joining end of the main strut so it would fit the contour of the pocket in the crossmember. Once this was completed, the two pieces were fitted together, checked for proper alignment and fastened with two screws.

Time to add the hardware:
I chose to place the pulley on the bottom of the assembly and feed the anchor line down Through one of the regular slots in the unistrut.  This was done to avoid any potential for the line hopping the pulley.  

The 3 stainless eye bolts were then installed with nylock nuts and washers.  The 1st eye bolt guides the rope through the hole to the pulley, the 2nd guides the rope through a turn  to the 3rd eye bolt and the 3rd guides the rope around the milk crate.  (The 3rd was moved over even farther after the test run.)  Surprisingly, this arrangement creates very little friction.

Finally, it's time to attach this assembly to the yak.  The attachment was made very simply.  A 5 J-Bolt was calibrated with a nut and large washer to hold the main strut at the correct height.  Once in place (hooked through the rear eyelet), a large washer and wing nut were used on the opposite side to sandwich the main strut, keeping it at the right height and minimizing shift.  

A small square of closed cell foam was placed between the main strut and the kayak to reduce compression and impact stresses.  Smaller J-Bolts were used at the ends of the crossmember to secure it to eyelets at the back of the rear well.  An unintended benefit of using unistrut is that the crossmember straddles the eyelets perfectly, eliminating contact with the kayak itself.

And voila!  My need for a drift anchor is fulfilled.

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