If I were to transport a kayak on its side on special saddles on my roof bars would I experience adverse effects such as increased wind resistence if the cockpit was open/uncovered? Does the use of a cockpit cover reduce wind resistence or will I lose the cockpit cover? What are the effects of wind resistence when transporting the kayak on its side or upside down?
Expect Less MPG
I carry mine upside down thinking that I would rather have the wind pushing down on the boat rather than lifting it up. I used to carry rightside up with cockpit covers… Until I loss them. So upside down, I don’t worry about water getting in either. When I carry more than two boats, then I have them up on the sides. I can really feel them in the crosswind.
I haven’t done a systematic analysis of gas consumption in the different configurations… And won’t! Would not matter. If I am paddling, I gonna be driving, whether I like the gas mileage or not.
thankfully, I tied my
Cover to one of the deck bungies… I was driving to the Adirondacks when the cover for my Loon 138 came off (I was speeding - over 75mph on I81). After that I left it inside my car. I couldn’t tell either way when I was driving though. My cover may have came off because the Cockpit on the 138 is so big.
My cockpit cover for my QCC
has a clip which Wendy thankfully poited out to me the other week. I didn’t even see it. I clipped it to the bungee on my deck and when I got to Tilbury to check the security of it all I found the cover had come off but it was still clipped to the bungee.
Gas milage and carrying boats
I can’t tell you about gas milage, but I can tell you that two years ago driving home from Cape Cod with my Loon 100 and Dagger Zydeko on the roof of my Toyota Corolla anytime I was over 60 mile an hour it sounded like someone blowing across the top of a coke bottle. What a terrible six hours.
Discussions with friends about covers have been equally frustrating. It appears from the forums here that Loons are not real good about keeping their covers on.
I only had this problem on the trip to the Cape, other trips to the Adirondacks have resulted in no problems. Go figure!
But your original question is a good one since gas prices have been soaring. I suspect there is some decrease, but driving at a steady rate of speed and keeping your speed below 70 would mre than compensate for the increased drag and added gas comsumption.
Danu LLC covers will protect your yak
while traveling and won’t come off. Don’t sell them or get a commission-they were a good investment.
right side up with covers
My wife and I have P&H boats (capella & sirius). We rack them in Yakima Mako Saddles, right-side up with “Brooks” (I think) cockpit covers which I hook to a deck bungie with a carabiner.
Once, on a particularly long drive (18 hours), I had one fly off, but other than that, they’re pretty secure (you can tighten them down pretty well).
I bought them mainly because of water, so if I carried them upside down as someone on this thread suggested, I wouldn’t bother with them at all.
Haven’t tried carrying them sideways, and my mileage is so horrible (less than 20mpg in a Ford Focus Wagon that usually gets 30+) that I have stopped even thinking about that component of my trips.
If you look at a hull like it’s a ski - then right side up it would seem the air would push it up - upside down would seem to be pushing it down. This is only two dimensional thinking though.
If instead you look at the hull as a wing - inverting the boat can actually cause it to rise. Wings are flatter on bottom and more curved on top (like most upside down kayaks). Causes the air to go over the longer distance of the curved surface faster - dropping the pressure on that side - creating lift.
At highway speeds - most hulls will push down when carried right side up. The bow may lift - but overall the boat should be experiencing down-force. Three dimensional thinking.
The “wing” spoiler on race cars - is actually inverted when compared to an airplane wing. It’s curved side is down.
Boats shapes are different, so amount of lift or down-force is different too. Some may be better upside down - but most not. This is only one factor, and other considerations (deck/hull strength, saddle/bar location, etc.) may make one way better regardless of the aerodynamics.
Has anyone seen wind tunnel tests?
Eveyone keeps referring to the shape of the boat and upside down versus right side up and no one seems to be considering that the thing is sitting on top of a car or truck. The wind hitting our boats is all over the place, including a downward angle as it curves up and over our vehicles. I would want to see wind tunnel testing for basic car shapes and truck configurations before I sound off too much about what the differences would be wind-wise. I pack mine sideways when carrying two or three up there and the ride is fine. You should consider tie downs on standard cars and longer boats too.
What about Yakima Hull Raisers?
Anyone have these? Any issues driving at highway speeds? If you have 'em, do you load the boat with cockpit out or in? It seems if you loaded it cockpit in, the opening would be slightly downard facing, and therefore rain might be less of an issue.
it depends on the vehicle
and boat in question. I know when I carried my boat up side down on my factory rack it howled like mad. add thule rack bars and it was gone.
kayaks aren’t as bad as bikes
Our mpg drops more with bikes on the roof than kayaks or canoes. Anything on the roof is going to add resistance, but 4 bikes is as bad as it gets. We lose about 5mpg with bikes and only 2-3 with boats at highway speeds.
Actually, Linear Thinking…
I am at point A and want to get to point B – where the water is. This is my most important consideration.
Three dimensional thinkers are welcome to evaluate how the areodynamics work when hull is up or down with the downward slope of my hatchback, taking into specific consideration of the hull shape of my surf kayak with highly rockered bow and flat stern vs my highly double rockered trickster, vs less rockered ultrafuge, vs minimally rockered SOF with a flat deck, etc, etc…
I loose MPG…
…with just the cross bars and Malones on a four cyl. car. They are easily removed for trips without the boats…
Note: Shell gas has just wiped out my gas gauge (a little problem in the Southeast with contaminated gas) so it really doesn’t bother me as much… GH
Before we were kayakers…
and lived in the DC metro area, my friend Tim Buckley claimed to get 3-4 mpg better mileage with his S-10 pickup (it had a cab-level topper with two rackbars mounted on it) carrying his kevlar Lincoln canoe.
We were Suburban drivers back then. Tim was kind enough to let us borrow the canoe on occasion, and wouldn’t you know, the mileage went up 2-3 mpg on the Sub!
I realize this flies in the face of reasoned thinking.
Having given it some thought, here is my theory.
Relative wind (air) hitting the windshield tends to hold a vehicle back and provides resistance to push against. The (upside-down, of course) canoe provides a more direct path for this air to get to the low-pressure area behind the truck/Suburban. The back of these vehicles are essentially flat. Lots of turbulence there. Maybe even partial vacuum?
So now if there is a vacuum behind a moving truck and a nice streamlined pipeline to move the high-pressure air there…
I read in a sailing book how sailboats are actually pulled forward more from low pressure air at the front of their sails than they are by the air pushing into the sails. That’s what I read.
I guess if airplanes are deriving more lift from low-pressure areas above the wings (an established aeronautical FACT) then it may follow that a canoe could aid ones gas mileage under the right circumstance.
Don’t know if the same can be said of any decked kayak, though.
Just my thoughts.
I agree, bikes are pretty bad…especially in a crosswind. I notice windshear and such far more with a bike on the roof than when I carried a canoe. Not much difference in noise, though…it’s all noisy. I do recommend a fairing for your rack.
I drove from Indianapolis to southern Utah with a bike and a BOB trailer on the roof of a 1991 Dodge Spirit 4 cyl and averaged 22mpg for the whole trip (including rolling down the windows in Kansas when it was 104 degrees and driving up the front range of the rockies).
Boats of any kind seem to affect aerodynamics less than bikes…though carrying them sideways on a kayak stacker or hullraiser is going to change things a bit.
Some boat/car combos work unusually
well. Carrying my banana-boat 15’ MR Synergy canoe on our 2000 Accord, we got 31 mpg on one tank, Atlanta to NC mountains and back. The following week, same car, same boat, we got 29 mpg cruising at 75 mph coming back from New Orleans.
This canoe, at least, seems to stabilize flow over the car so that mileage is dropping only about 4 to 5 mpg from what it would be with no boat, no rack.
To the extent that kayaks are shorter, they are going to have less tendency to stabilize flow.