Whatever you do,
watch the oscillation approaching transonic speeds.
That’s right
Minimizing the interference between the roof and canoe would be my best technical guess.
Guess number one for improving mileage is to set the canoe directly on the roof with no gap. The next most likely improvement (which is pretty much unworkable for any of use) is to mount the canoe 3 ft. or so above the car on a skinny pylon so that the car and canoe behave aerodynamically as independent objects.
Your time is best spent canoeing rather than thinking about this stuff.
gonna need bigger engine
Transonic! you know too much…
Don’t you love …
… those occasional pickup trucks you see with one end of a long open canoe in the bed and the other end angled way up high over the cab.
thanks, folks
?
Would snugging the boat close to the car top create a boundry layer disterbance? Does mounting a boat above the boundry layer of the car top produce superior arodynamics similar to pod mounted turbofans??
Turtle
Just bite the bullet and…
stop at every other gas station when you are in a full size 4x4 pick up with a 100 pound tandem 23 foot long kayak along with an 18 foot kayak and a 16 footer on the roof pulling a 25 foot 5000 pound travel trailer with another 1000 pounds of gera in the bed of the truck and in the trailer.
-50 percent decrease in MPG !
Jack L
Quora!
– Last Updated: Apr-30-12 1:13 PM EST –
Rather than wonder amongst ourselves (probably not many fluid dynamic engineers on this forum) I posted this question on Quora (which has lots of every profession!)
If you have never been to quora.com I highly recommend it. You can ask or answer questions on any topic and get answers from experts in the field. Some on the more interesting ones I read were "what was G.W. Bush like in private?" that was answered by a couple of aides who spent time with him. Also I love the theoretical physics forum to help me understand the Large Hadron collider. Many physicists, professors, and nuclear engineers help explain this stuff both very scientifically and in plain English. the best of both worlds! They have topics on anything you can think of from canoeing, to food, self defense, war, philosophy, everything really... and get unusually intelligent answers.
Anyways I posted this question over there in the canoe forum. If it doesnt get any responses in a few days ill repost it in a science forum. Check it out:
http://www.quora.com/Canoeing/Is-there-any-way-to-improve-aerodynamics-for-transporting-a-canoe-car-top
actually gain in highway mileage
Actually get slightly better mileage with the surfski on the roof. I carry it directly on the cross bars, upside down.
I believe the gain is coming from having the teardrop shaped tail sticking back six feet through the low pressure area since I have a wagon. Helps keep some of the air from going turbulent.
that is an eye-opener
Psst…
Don’t give away our secret.
Slow Down
My mileage is worse with a canoe or two on top(hull up, no covers, roughly 4" between car roof and gunwales). But it’s 3-4 gpm worse when I drive at 70-75 mph than when I drive at 60-65.
It can be scarey driving that slow on New England highways so I don’t know if slowing more would help.
I wouldnt follow truck
The most important reason not to follow a truck are STONES. If you have ever driven a motorcycle on the highway you know its not a good idea to follow a tractor trailer. Unless you like getting pelted by small stones coming off the rear set of tires, enough to really hurt and draw blood at times has happened to me.It can be real bad at times depending on road. So unless you want a nice small whole in your air conditioner condenser don’t follow trucks plus nice stone chips off paint all over the front of your car. Not worth any gas mileage increase if you ask me.