drilled or faired ladder racks?

[miket]

My truck cap has racks for transporting ladders. What would make the square tube racks more aerodynamic. Fairings attched to the back of each rack to keep airflow attached or holes drilled in the racks to let air pass through it?

If the racks were round tubes id hit em with a hammer till they looked like golfballs and call it a day. just kidding.

[AeroModder]

Faired. It'll help the air not be as turbulent around it.

[Otto]

Originally Posted by miket

My truck cap has racks for transporting ladders. What would make the square tube racks more aerodynamic. Fairings attched to the back of each rack to keep airflow attached or holes drilled in the racks to let air pass through it?

If the racks were round tubes id hit em with a hammer till they looked like golfballs and call it a day. just kidding.

Easy: Make glue-on teardrop fairings for the racks out of polyethelene foam. Hotwire cut the foam, or get a local RC model airplane guy to do it for you. That's the kind of foam used for round pipe insulation, uber-cheap at Home Depot and your hardware store, comes in various sizes.

D shaped foam at front of square tube, > shaped fairing at the back side. Dunno which glue to use, but somebody does, esp., the RC model guys.

[miket]

Is that kind of foam either strong or flexible? I dont want it to flex in the wind but if a ladder is loaded behind at an angle it could push down hard on the fairing behind the rear rack.

Edit: i suppose it if wasn't i would just leave a gap at the places the ladders contact.

[endurance]

I agree that fairing is the way to go, as drilling will likely give you a truck with a thousand whistling sounds in the wind. How about getting some same diameter pipe as the square tubing, cutting it in half so it's half-round and tacking it onto the back side?

As for foam, I don't think it would hold up to banging a ladder against it occasionally.

[silverinsight2]

Replace the tubing with this:



4130 STREAMLINE TUBING from Aircraft Spruce

[miket]

Aluminum streamline tubing would be ideal but would cost $100+? How much aero improvement would I get for that?

Ladder are lifted from the sides or slid up from behind. I suppose the rearmost fairing could be made of a ridgid and weak material if it was attached on the bottom to a spring so it could bend slide or twist downward from that rack during loading.

[Frank Lee]

FWIW...

if the ladders are absent a lot of the time, have quick releases for the racks and take 'em off.

if the ladders are on there most of the time, it won't matter if the racks are faired or not as the ladders themselves will destroy the aero...

unless you make an enclosure for them.

The hole idea would only serve to make aero worse.

[brucey]

If the pipes for the rack are small (>3/4") then I doubt they're making a ton of difference unless you're regularly going 65 mph+

It might be worth it to do some ABAB testing for yourself at say 55 mph to see how much you're losing by just keeping the racks on full time. With them empty, I can't imagine them being more than 5%, and again that's only in steady state cruising.

Something I imagine a vehicle needing ladder racks doesen't do a lot.

[Otto]

Originally Posted by miket

Is that kind of foam either strong or flexible? I dont want it to flex in the wind but if a ladder is loaded behind at an angle it could push down hard on the fairing behind the rear rack.

Edit: i suppose it if wasn't i would just leave a gap at the places the ladders contact.

Strong, cheap, and flexible. Round polyethelene foam pipe insulators sell at the hardware store for $2 or less for 8' length, depending on pipe size. Google or YouTube for "hotwire foam" keywords. Used to be, RC model airplane guys made wings, etc. out of styrofoam, which is pretty weak and brittle. Polyethelene, otoh, is tough, light, strong, weatherproof, and very cheap, so I'm told the RC crowd now uses that for crashproof planes.

On the whole, though, follow Frank's advice and take the whole rig off the roof if/when able, since fairing the rack will only give marginal improvement to an otherwise atrocious aerodynamic roof rack & ladder setup.