As per advice from my local kayak dealer I place my sit-on-top kayak upside down on my vehicles roof bars and secure with 2 tie downs across the car and bow and stern lines. However the Kayak slides across the roof bars from side to side. How do I prevent this from happening?
suggestions…
hi …some suggestions …1st …run your tie-down straps in a X pattern across the boat,right front to left rear and vice versa, fasten the ends of the straps directly to the cross bars as close to the boat as possible, cinch tightly but not enuf to bend or warp the boat and use bow/stern lines.
2nd…add old rug pieces or something similiar, to the bars to provide a slip-resistant surface for the boat to ride on, still using the X pattern straps or …
3rd …use j-bars to carry the boat.
PS: i can’t believe the vendor didn’t try to sell you J-bars to begin with !!!
I had the same issue
When I was too lazy to add bow and stern lines on short trips. I even talked to a manufacturer at Paddlesport about it. The first thing he sais was “Are you using a bow line?”
So to solve your problem, use at least a bow line, a stern line for belt and suspender protection.
BTW, the kayak gods like the cockpit up.
foam blocks
Another solution is to get the foam blocks that cover your cross-bars, and have a shallow vee-shape to hold your hull (cockpit up). When you strap the boat on these they will prevent any side-to side movement.
(if you want to get fancy, you can even cope the blocks to match the curvature of your hull, and then you’ve got a custom-molded yak rack for $14) 
I have a concern about the X pattern.
The X pattern tends to pull the bars toward one another, putting a twisting force on the towers. In some cases, towers may slip.
The X pattern is safe only for those whose crossbars are clamped securely to factory roof bars, or for those, like me, who have put fore-and-aft struts between the front and rear bar.
As for the sliding problem, if one hunts through the various Yakima or Thule parts, one will find clamp blocks that can go on the bars and keep the ropes from sliding. If the ropes don’t slide, the boat can’t slide much.
Bow and stern lines do not cure this
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problem. Even double lines at each end, triangulated, do not cure it, though they will alleviate it.
Oh, and the kayak gods notwithstanding, most whitewater paddlers carry kayaks on edge or cockpit down. Carrying kayaks cockpit up may invite hull distortion.
The foam blocks are an improvement,
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but having used them on long trips, with bow and stern lines, I have not found them adequate to control shifting of heavy kayaks. Any sort of clamp, even stainless hose clamps, that stop shifting of the foam blocks will also stop shifting of the boat.
Here’s an option
Use an extra strap (or rope) at each bar. Run it through your other straps before you tighten them, just below the bar. Tighten your straps. Then tighten the 2 new ones (one under each bar) running through your primary straps. This will cinch everything down and it won’t move. You may even get away with just doing this on the front.
I don’t know if my explanation is understandable or not. Wish I had a picture of it.
Ok, I’ll clarify
Bow and stern lines in a inverted V, will stop the boat from sliding from side to side.
No, they will not. One can improve
the effect of bow and stern lines by using separate lines to each side, in and inverted V. But if you use a single line at each end, the boat will slip on the line at the attachment point.
On long trips, I do use four lines at the ends of the car, each one going from a tow line on the car to one end of the grab handle. Even this does not completely eliminate boat wiggling in the wind. That’s where cradles for kayaks, or gunwale brackets for canoes, come in.
An additional note. One should check the fore-and-aft angle of the end lines. For shorter boats such as SOTs or many other kayaks, end lines from the tow eyes or bumpers will lie at an angle that prevents the boat from sliding forward or back. With longer canoes or kayaks, the rear lines may run vertical or slant back, and this can result in boats sliding forward. Sometimes adjustment of the position of the boat on the racks can allow a favorable, stable, angle of the fore and aft lines.
Buy some cheap
stackers or cradles and be done with it.
jim
Simple if you have scupper holes
Tie a rope(s) through the hole(s) and then to each side of your vehicle rack.
That is what I do with my SOT
Cheers,
jackL
I had the same problem
and solved it by tieing two bow lines tothe kayak, then running each line to the front-side of the car.
Today I have webbing bolted to the front-sides of my car hood that stick up when I need them.
The problem is aerodynamics. the wind will push the boat and if you only have one bow-line, that will allow the boat to move back and forth as the wind changes.
BUT, if you have two bow lines like this -----^ where — is the kayak and ^ are the two reverse-v lines, these two lines force the bow to remain ion one place. the rest of the boat then follows like a streamer.
A way to demo this is to tie your kayak by one bow line to a tree in a river and watch is move back and forth.
Then tie the bow to two trees some space apart and the bow stops moving.
If you want to tie two stern lines, it helps but I find that redundant.
Hullavator
This is some what related. I recently purchased a Thule Hullavator because I got tired of banging up my jeep while trying to throw my kayak on top. Some of my friends have Hullavators. When they load the kayak on the Hullavator, they put it cockpit down. However it is much easier for me to lift it on the hullavator with the cockpit facing me. Does it really matter how it is placed on the Hullavator? Cockpit up vs. cockpit down?
If in doubt, cockpit down.
SINK - transport cockpit down
SOT - transport cockpit up or down
Carrying a SINK or canoe cockpit up is asking for trouble if it rains and fills with water.
cockpit up
Cheap cockpit covers keep all but a couple of cups of water out of your boat even in the heaviest of rains.
Chris
transporting
I can’t believe the dealer didn’t try to sell some kind of carrier as well as a kayak. Relatively cheap foam blocks work ok and specific carriers work better. For a SOT plastic boat I would recommend a J style carrier, but almost anything will work better than putting the boat on the bare bars. Bow and stern lins should be used, but their main purpose is to keep the boat from becomming an unguided missle in case of a sudden stop and they aren’t too effective for side to side slippage.
You have to tie the middle of the kayak
to the underside of the car with at least 2 straps
The most secure method, …
…other than saddles or good-fitting side blockers mounted to the bars (side-blockers work well when placed against canoe gunwales, but I have my doubts about getting a good fit against the rounded hull or deck corners of a kayak), is THREE tie-downs per cross bar.
Yes, 3 tie-downs per cross bar.
The first tie-down is easy - it’s the one you already do. The second one starts from the right side, wraps around the boat and comes BACK to the right side where it is tied off. The second starts on the left, wraps around the boat and comes back to the left, where it is tightened up and secured. Unlike inverted-V bow and stern lines, with this method the sideways motion of the boat is directly in-line with the force that is applied to prevent that motion, and further, the ropes or straps can be made tight enough to overcome whatever stretch might occur due to the sideways force exerted by the boat, so it works perfectly.
The inverted-V tie-downs at each end can only be partially effective since the motion of the boat is much greater than the “degree of lengthening” required of the tie-downs during that sideways motion (it’s a geometry puzzle worth thinking about). Thus, there’s a great mechanical advantage in favor of the boat, and the slightest amount of stretch in the rope will therefore allow quite a lot of movement. You can’t prevent this by over-tightening those tie-downs to overcome that stretch without over-stressing the boat with downward force that’s too far from the cross bars. Only a totally non-stretch rope would actually work in this situation, and there is no such thing, so the inverted-V works some, but not completely.
I’ve carried my Tarpon 160 upside
down on my racks many times. I use the wrap-around rack pads most outfitters sell. Snug the straps right up against the hull and use front tie-downs. It will move a little, but it won’t go anywhere.