car topping - frame only

[harwax]

Hi Everyone,

Since I own 2 Folbots, I was wondering if their are any downside to car topping frame only (to cut down on wind resistance - mainly for trips under 10 miles). My reasoning is that it will save some set-up time when I go paddling. If it's a good idea, anyone have any suggestions for doing it on a Camry ?

Thanks... Harold

[Dickc]

On a trip of less than 10 miles, I don't see why you would care. Cutting wind resistance will save gas. Even the empty roof racks cut fuel economy. Since the price of gas went over $4 a gallon some time back I've been folding my GII and carrying it in the car on cross country trips of 300 to 2000 miles at highway speeds up to 75 MPH. I've also removed the roof racks. But your Camry will burn less than $1 worth of gas on a 10 mile trip and you'll probably be driving slower than 50 MPH (unless you experience Toyota's unintended acceleration ) so what's the point? You might save 2 cents worth of gas. I think you should look elsewhere to reduce your carbon footprint and save money.

Dickc

[harwax]

Hi Dick,

My main reason for doing it was to save some assembly/dis-assembly time. I can store frame(s) in extra bedroom. The reason I brought up wind resistance was that I hopefully won't have to be quite as careful with tying it down on car roof. I really wasn't concerned with price of gas.

Harold

[BernieM]

With my Cooper, I would be concerned that a frame part might separate without the skin holding everything together.

[MrPorcine]

I would be surprised if the frame by itself had less air resistance then the complete boat. The boat is pretty aerodynamic but all those tubes and frames have terrible aerodynamics. The rule of thumb is if it doesn't have at least a 3:1 aspect ratio it's going to be very draggy.

As an example, a three inch long, one inch diameter pipe sticking out horizontally from the side of a small airplane has about the same parasitic drag as a complete wing. Hard to believe.

[Ken Hartlein]

Jim your name sounds very familiar to me. Were you ever at Point Arena AFS or Blaine AFS???

[whiskers]

I would be surprised if the frame by itself had less air resistance then the complete boat. The boat is pretty aerodynamic but all those tubes and frames have terrible aerodynamics. The rule of thumb is if it doesn't have at least a 3:1 aspect ratio it's going to be very draggy.

As an example, a three inch long, one inch diameter pipe sticking out horizontally from the side of a small airplane has about the same parasitic drag as a complete wing. Hard to believe.

I agree with this. I am not an expert on aerodynamics, but it is logical that the frame alone will create a lot of turbulence as opposed to having the skin on. As Dickc said, it is known that roof racks cut down your mileage, and roof racks are just a bunch of tubes, kind of like a boat frame. That's why rack manufacturers sell fairings (well, that, and to make even more money off of us outdoor types) to let the air flow around the rack, not through it.

But all it really depends on is your speed. Drag force depends on the square of the velocity, so every time you double your speed, you quadruple your drag. At 25-30 miles an hour you wouldn't be wasting too much gas, but if you are doing 10 miles on the highway, you'll encounter lots of drag and lots of noise/whistling from the tubing.

[PeteS]

I was going to try hauling the Cooper frame on the cartop but couldn't figure out how to tie it as not to injure the frame. Plus I would have to tie the stern section so it didn't fly off. Anyway, I never left the yard with it, but I did figure out why the frame whistled.....IT DIDN'T KNOW THE WORDS!

[harwax]

Hi Peter,

What I finally ended up doing was buying a foam kayak pads & straps kit (I don't have a rack on car roof) and car topping it right side up, using 2 straps wrapped thru left and right side windows (front & back windows), securing straps over the cockpit area only and lightly securing the bow strap to front of car (extra security precaution). BTW- I car topped with skin on but imagine it would work with frame only. I only transport locally and had car speed no higher than 50 MPH. It worked find.

Harold

[PeteS]

That little bow line is VERY important. There was a guy's kayak that actually broke in half when the wind took the front half and folded it over, due to the lack of a bow line. You did well.

[harwax]

That little bow line is VERY important. There was a guy's kayak that actually broke in half when the wind took the front half and folded it over, due to the lack of a bow line. You did well.

Thanks Pete for your vote of confidence. I will always use a bow line. Forgot to mention I basically followed Folbot manual's instruction on car topping.

Good luck in selling the sporty, even though I can't imagine you need it.

Regards... Harold

[BernieM]

Harold
It is better to put the straps through the open doors rather than the open windows. Also, I like to loop the straps once around the kayak rather than just putting them over the kayak to give a more secure feeling.

[Ken Hartlein]

That is good advice from PeteS about the bow line. I would not haul my kayaks 1 mile without a bow line. I've seen what can and will happen!! Not to me but a friend.

[spoonido]

That thing about aerodynamics rings true. I know that motorcycles and bicycles going for a land speed record all use some sort of form around the frame to reduce wind drag. So did the Gossamer Albatross - the first human powered airplane.