Kayaks on SUV roof can act like Wings!

Had an incident that we wanted to share with others who enjoy kayaking so they are at least aware of this happening.



We have been actively paddling for the past 5 years in upstate NY. We use a 2004 Honda CRV to transport the kayaks with Thule fold down saddles on the factory installed roof racks. We have never experienced this before in the 5 years we have been doing this.



Driving north up the interstate (I-87 Adirondack Northway) to Fish Creek Marina several weeks ago, an 18 mile trip for us. The steering wheel suddenly became very sloppy - almost acted like a broken tire rod. Upon inspection at the side of the road all was intact. Thought I might have needed a front end alignment.



Talking to the local repair shop that next Monday who services our vehicles, they told me that placing kayaks on top of your vehicle can drastically change the aerodynamics of your SUV. It can cause the kayaks to act like wings, essentially lifting up the vehicle.



There have been several reported serious accidents on interstates around the USA, where a tractor trailer going by has flipped the SUV over with it’s kayaks on the roof. This is due to the amount of air that a semi trailer displaces as it travels and the winged effect of the kayaks.



Our pair of WS Pungo 120’s are especially wide ones at close to 38" inches of width at their widest point - we have them on edge in the saddles on the roof racks. We have since changed over to our kayak saddles being mounted to an Aluma utility trailer. If we had not owned the trailer already we might have looked into replacing the current saddles with a set that would transport the boats in a flat position (like they are used on the water).



Just wanted to share this so others could avoid a similar situation, or at least be aware of the possibilities.

semi-suck
a brief search for SUV kayak accidents yields news story links merging SUV accident with …kayak…but the stories/incidents are within the link but unrelated in real time on the ground.



Post your references ?



The roof rack holding the yaks would not support the vehicle’s weight. Surly not a Thule or Yakima.



Nor whatever holds those contraptions onto the vehicle.



You’re prob experiencing a low pressure area under your vehicle then responding to this variation in driving reality with the wrong moves: semi-suck.



As with loss of adhesion over snow, tail going right, steer into not away. Just ‘catch it’ with a wheel twitch then ease back to straight ahead.



Bronco owners ?



Could be roof kayaks on a specific vehicle shape exacerbate semi-suck ?

I actually agree with datakoll

– Last Updated: Jul-14-14 11:35 AM EST –

Imagine that!

You'd pull the mounting bolts right out of the roof with far less lifting force than it would take to substantially unload the front wheels. That is, if your straps or ropes didn't break first as the boats tried to rise.

Oh, and I'll add another thing. You've noticed how much your plastic boats get pinched and deformed if you pull the straps too tight? That's just double the tension due to of pulling with one hand (double on account of the pulley action of the buckle, but actually the friction would make it a lot less than double). Now imagine how squashed and damaged the boat would be due to strap tension once this lifting force became strong enough to do as you describe? Your boats would be junk afterward.

Things can get squirrely as big rigs go by. I think most of us know that (how much so depending on what sort of boats we carry). As the cab comes up alongside you, you'll get pushed away from the truck much more so than normal with certain kinds of boats on top, and as the cab passes, you can either get sucked back, or the sudden loss of pushing force has the same affect until you "undo your countersteer". Once the tail of the trailer gets in front of you, your car can get knocked every which way as it is buffeted by little blasts of curly-cue air flow.

If you think it's bad carrying boats, try it with a lightweight motorcycle that has full luggage racks and a windshield (it's not any more dangerous, but it's much easier to understand what's going on when you can feel the turbulence in this "more personal" manner).

poppycock

It’ll never fly…
“You’ll never get your SUV’s wheels off the ground Orville; unless you mount at least 3 Pungos on your roof rack”!



Not enough lift; seen it right off!

BOB

Never saw or heard of such a thing.
Your advisors are speaking to you out of ignorance.



The main thing is that the boats be firmly tied in place.



Canoes and kayaks don’t generate much lift, but I suppose SUPs might. Maybe.

would not blame the kayaks
I have to agree that the kayaks are unlikely to be the prime source of such instability. Since I have relatives up that way I drove up the Northway lots of times (many times to Fish Creek, in fact) in my previous vehicle (a Hyundai Santa Fe) and experienced what you are describing WITHOUT kayaks on the car as well as with. There can be strong crosswise gusts along there, as there are on several other highways I regularly traverse with and without kayaks.



This is a common problem with high SUV type vehicles and vans (used to feel it with the Dodge Caravans I owned as well, even literally had a gale force wind move one sideways on an interstate.) And it’s one reason that I don’t care to own or drive such vehicles any more. Good tires with the proper inflation help, but nothing is going to keep a car with a high center of gravity from getting highly squirrely in gusty crosswinds.



Did you have bow and stern bumper lines on the boats? I’ve driven behind cars carrying various boats with no bumper lines and seen the loads wobbling and abruptly shifting – unless I can quickly pass them, I drop WAAAAY back when such cars are ahead of me.



I’ve also had the experience of being a passenger in a vehicle (GMC Jimmy) towing a trailer that was poorly balanced with a heavy load (a gymkhana race car) and where the car tire inflation had not been adjusted to compensate for that load. We were driving on an interstate on a long downhill grade and the car began slow oscillations from side to side, of increasing amplitude until you could feel the thing starting to tilt up on alternate sides – a friend following us reported afterwards that he could see the car and trailer whipping back and forth and was sure we were going to roll the whole shebang and be seriously hurt. As I began to react instinctively by bracing into a crash position (while slowly chanting “oh sh***t”) I suddenly realized the panicked driver was pumping the brakes – I screamed at him to “punch the accelerator, the trailer is trying to pass you!”. To his credit (and to my surprise, since it is the first and only time I have ever had a boyfriend listen to my driving instructions), he floored the accelerator and the car surged out of its sine wave dance and it and the trailer straightened out. We pulled over at the next rest stop and unloaded the sports car and drove it and the emptied trailer the rest of the way. Before going back after the race, we adjusted the load and the tire pressure and had no such problems on the return trip. You should not have such an issue trailering with a load as light as the kayaks, but be aware of the potential if you haul heavier loads. And be aware that braking can be the worst thing to do when you feel like a vehicle is being pushed by the wind or feels like it is going to skid on wet or dry pavement. Also a bad choice when a tire blows at speed.



Maybe being a bike and motorcycle rider gives you better body instincts of that – I’ve noticed nervous automobile drivers, especially those with little experience with high speeds or other sorts of vehicles, will default to stomping on the brakes at any sign of unusual performance.



Perhaps a digression in this conversation, but it occurs to me that there are a lot of people on the road who really are not all that well trained to drive, especially with high balance point vehicles and their unique handling issues. One such person crashed his Ford SUV into my house in Michigan, causing nearly $10,000 worth of damage (some of which could not be fully repaired) and scaring the bejesus out of me at 2:00 AM. He tried to take the turn at the T intersection across from my yard too fast, braked in panic at the turn apex and threw the car into a countersteer skid, plowing down 20’ of chain link fence before ramming an 8’ railroad tie landscape timber through the concrete foundation of my house like a scud missile.



I admit I learned a lot of what I know about driving from taking several high-speed driving classes from SCCA members at race courses. I would recommend such training to anyone who wants to increase their safety on the road (many sports car clubs offer them). Once you’ve had a qualified instructor take you through some real skids and near rollovers at speed under controlled conditions, you gain a much better feel for controlling your car.

1 Like

bow wave


There are websites and images for your viewing



http://goo.gl/sEV2Hi



Know a hull/water bow wave ? Air flow off a few tractor/trailers does the same but not traveling very far in a 3 dimension path.



Your vehicle moves sideways away then back as the side then the bottom of your vehicle enters, peaks, then moves into a lower pressure area than the standard pressure the vehicle was in before passing thru the bow wave area.



These transient pressure(s) are more than your vehicles suspension design parameters yet some suspensions/bodywork slice thru that air with a wiggle n some are truly a handful. In the ‘do pigs fly’ area, trucks are slower in the snow than we are. Be thankful.



Kayaks on the roof aren’t supporting stability or are they ? IMSA and Lemans prototype coupes sport a single rear section fin.



My Rendezvous’ bow foil of paneling n 4 coats Rusto is ready for sawing. From bow gunwale to first thwart. A triangular diverter under and before the R is possible.



I’ll report.

Are J-cradles worse?
Like others have said, I also doubt roof mounted kayaks could aerodynamically lift your CRV. That said, I’m wondering which is aerodynamically worse for for a tallish lightweight car on the freeway. I’m driving a Honda Fit with my large, but lightweight Pygmy Arctic Tern 17 on the roof with J-cradles. With it’s angular hull turned sideways and up higher than saddles, I feel like this is much worse for semi-truck crosswinds. Is that generally true?

j-cradles
I’ve felt stress from wind-buffeting was more when hauling with J-cradles on the highway than my current choice of loading the boats deck down/hull up flat on pool noodles sleeved over my Thule bars. A sideways boat at an angle isn’t very aerodynamic. In such cases I am less worried about wind affect on the car performance than I am the uneven stress on the rack components and straps and on the boats themselves (I haul set-up folding yaks half the time.)

i left a voicemail
For physics, but I suspect they will disagree. Aside from the shape not supporting lift, the weight is all wrong.



Turbulence from semis, bald tires, wind, all bad for handling. Kayaks lifting vehicles, nope.

Agreed
I’m also less worried about car performance, but more concerned with the wind from a passing truck damaging or ripping my whole kayak(with rack) right off. I do however think the J-cradles have decreased my mpgs slightly more…

Training for High-Speed Driving
And if you become really good at high-speed driving and inducing near-rollover conditions, there might be a job waiting for you at Consumer Reports the next time they are ready to intentionally publish falsified data on SUV stability in support of their very NON-scientific political agendas.

more is less
Adding positive effect ‘aerodynamic devices’ is difficult. More area gives more drag. Fashioning more area into positive drag given a mobile platform exposed to a dynamic environment…good luck.



story: there is a pedestrian bridge across a straight at Sebring. During evening practice traffic was solitary. A Lemans Ferrari 512 drove thru several times, a clubman’s racer, equipped with various aerodynamic devices. The bridge swayed several times in the 512’s wake.



Porsche brought a hillclimber 917 covered by a smooth round minimal body. Bridge didn’t move.



This is big time racing here !



I came back remembering most frequent and forceful displacements from the desired line of travel occurs on double lane raised approaches to bridges/overpass and cut n fill roadway’s as the one near Ebey’s Head. If traveling on the outside passed by a semi, forces can be much greater.



A kayak mounted from the side hull is effective running in a straight line tho the asymmetry is less but when the vehicle turns, and the vehicle is ALWAYS turning then positive pressure drag develops on one side, negative pressure drag the other…so that’s where you are…in drag ! Self inflicted headwind.



Less is always more. Take a look at the Self Propelled LSR websites and Images.

well stated
Hah, I think the OP was a nice troll. In addition to the impossible physics, the poster is WAY off on the width of his Pungo 12 kayaks. 38 inches! No, they are 29 inches wide.

Consumer Reports
You’ll get no argument from me on the inanity of much of CR’s analyses of the drivability of various vehicles. SUV’s are what they are, specialized for certain functions. They are not inherently dangerous IF ONE KNOWS HOW TO DRIVE THEM PROPERLY and is willing to accept their limitations and quirks.



The problem is that fewer and fewer people really know how to drive well any more, particularly this type of car. My biggest bitch about SUV popularity is that too many drivers think that buying one immediately makes them better prepared to navigate roads in bad conditions, both geographic and weather-related. A high riding 4 wheel drive vehicle does NOT handle the same as a low center of gravity 2 wheel drive car. Having one without having the skills to negotiate bad terrain or weather hazards will not protect you and may put you at worse risk than if you had a regular car and would normally stay off the roads in those conditions or would exercise more caution in a standard car.



In years past I used to love driving in bad snow storms because I had been taught by my father how to handle any car in such conditions and because few other people ventured out in them – when the streets had few cars on them it was far safer to drive in the snow. But once people began buying SUV’s they developed a false sense of security – now you see tons of people without a clue how to drive on snow and ice (and who should stay home during storm conditions) out there sliding around in their big unwieldy trucks, rolling them into ditches, locking up the brakes and skidding into other cars.



And I see them all the time bogged down and spinning their wheels in the mud at river put ins. These cars will also lose traction in dry conditions if you don’t handle them correctly. If you know how to drive them they can be great vehicles for remote rough roads and snow slick highways. But the fact is that most people who own them would be better served with a standard 2 wheel drive station wagon or minivan.

It’s a long story
The story has been told many places, and I’ve referred to it here before. They did NOT test the one vehicle which was already known to be the most rollover-prone SUV of all, the Ford Bronco II, because Ford was a big company which had the money to fight back, so they picked on Isuzu and Suzuki instead. On the test track, Consumer Reports pushed their targeted “roll-risk” vehicles MUCH harder through the turns than any of the comparison vehicles, and this was scientifically proven by an independent lab using frame-by-frame analysis to determine speeds and G forces of all the tested vehicles. There was even a video of the “test” proceedings that was discovered during the ensuing investigation where a test driver was heard to say something like “it’s no use, it’s only sliding” (not tipping), and the track boss threatened to fire him on the spot if he didn’t make it happen in front of the cameras as ordered.



What Consumer Reports did was absolutely criminal. I have no argument with their stance that truck-like 4x4 vehicles are beyond the needs of most buyers and thus waste gas, but their chosen method of trying to discourage sales of such vehicles was as dishonest as could possibly be, not to mention the fact that a supposedly unbiased testing outfit wouldn’t venture into the business of attempting to mold public opinion to suit some guiding principle that their management believes to be correct. I will never again trust Consumer Reports, as they showed their true colors with that fiasco.

Same here
I owned an '87 Samurai, long after the CR hatchet job. It was perfectly decent on curves and turns, in fact felt more stable than some rental cars I’ve driven that are very, very popular.



The worst thing about the Samurai was actually how it behaved in gusty cross-winds, thanks to its light weight relative to height. Cornering was NOT a problem.



It was probably the only true 4x4 back then that got 28 mpg highway.

wings
The cool part is flying you get 55 mpg.

The 38" is a Sidesaddle Kayak
There’s an extra seating option at that width, so you can sit sideways and watch the shoreline without craning your neck while drifting down the river… comes with a hand operated rudder, you just steer with one hand, and drink with the other…



Flight Division Honda has been working with Pungo, and is coming out with deployable pontoons for “In-the-Lake” landings to get your party on the water, faster, without having to deal with the messy boat launch ritual.