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I was concerned about two things: 1) stability 2) range impact. The longest leg between charging is ~120 miles, but I didn’t want to arrive with only 10% charge…
As for stability, we used the racks from Tesla, which are made by Yakima, and the Yakima “BigCatch” saddles. The rack is rated for 165 lbs, and the saddles for 150lbs; our boat weighs about 90 pounds. The rack mounting points are only three feet apart (90 cm), so I carefully measured where the balance point of our boat was and set the saddles 18″ (45 cm) fore and aft of center, I also centered them side-to-side on the rack, guessing this might improve aerodynamics.
I never was much for bow and stern lines attaching a kayak to a roof rack, they can put too much stress on the boat if you are not careful. I have car-topped this boat up and down the Alcan (to Alaska from Seattle) several times without ever using bow and stern lines, and never felt the least bit concerned. However, once we got the 24′ beast on top of the Model S, it was clear that bow and stern lines would be needed to stabilize the boat. There is just too much front and rear overhang from the racks to hold it from bouncing up and down too much. The flex in the bars of the roof rack was also a little disconcerting, but hey, the rack is supposedly rated for 165 pounds, and flex is a great design characteristic: our skin-on-frame kayak relies on it over ocean swells (nylon over aluminum tubing lashed together in Alueut style)!
So I was in your dilemma, but maybe a bit more extreme version of it! How to secure bow and stern? The BigCatch saddles come with nylon webbing with a loop and a fastex ladder-slider buckle on one short strap for attachment to the boat (loop the buckle end though the loop and the carry handles on the kayak and cinch down with the buckle hanging), and a long one with only a loop and a short length of plastic sheathing-like clear polyethylene tubing- to protect the car paint for closing in the hood and trunk. The other end of the long webbing is secured through the fastex ladder-slider buckle hanging from the boat. We tried this, but the frunk webbing kept slipping out, the line got loose at 45 mph or so. The frunk wouldn’t close properly with the webbing secured to the metal loop on the hood.
So, we installed the front tow-eye (reverse threads!) and didn’t worry too much about those wires. If my interpretation is correct, they won’t be carrying any current, unless you have jump-start cables attached to them! The liftback held the stern line securely, but still, it seemed an inelegant solution that needed to be re-secured every time the liftback was opened. I ordered another tow-eye by searching the web and finding one at an auto parts store in the San Fernando Valley (P/N 1077570-00-D, the same for Model 3, and refresh S, and probably Y). I’ll use it in the back to secure the stern. The nylon webbing has a loop sewn in the end, the user simply loops the other end through both the tow-eye and the sewn loop and cinches it down. Since the entire webbing strap needs to be threaded back out upon dis-assembly, I decided to purchase some stainless-steel snap rings, like carabiners but used for commercial halibut fishing, to clip the loop end of the webbing to the tow-eyes.
Be very careful not to tighten the bow and stern lines too much! A little bounce is not a bad thing! The stern line counteracts the bouncy forces on the bowline, and vice-versa, which really minimizes movement even when the lines are only just snug.
Since I won’t be doing this a lot, I’ll remove the tow-eyes and pop the plastic covers back in place for most of my driving.
My brother-in-law tells a range-anxious tale of car-topping a Christmas tree on his Model S, so I was very concerned about reduced range with all this stuff on top of our car. I had been driving around town without charging for a little while to gauge baseline efficiency without the racks and kayak. I got the car in October, so haven’t put many summer-type miles on it. (I was skiing last week, it’s just starting to be spring here now!) I drove 88 miles and had an efficiency of 228 Wh/mi. I loaded up, adjusted, blah blah blah, and drove 24 miles over the same roads I’d put the 88 miles on. Efficiency with the kayak on top on this quick, uncontrolled experiment (weather was *pretty* similar throughout) was 264 Wh/mi. Speeds not much over 50 mph… I was very pleased. Although my wife looks somewhat uncertain about this whole experiment in one of the pictures, we both agreed that the 200 mile trip with this arrangement seems highly doable. We’ll definitely be flagging the stern, because it overhangs 5’4″ from the rear of the car. The front overhang is less than 3′.
Hope this helps you and anyone else trying to push the limits…
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