Alucab RTT Aero Mod

[Rokon]

I've run my Alucab Cap and RTT with 270 awning for 3 years now and love it. The only drawback for me is the bit of a mpg hit I took at 75mph. At 55mph I can still get 19-20 mpg. The added frontal area really adds some drag at higher speeds and kills a lot of bugs. I make a regular 3 hour highway run and see around 16mpg at speed.
Figured it was worthwhile to see if I could make an improvement.
So this is what I was looking at.

It took a few mockups to work things out. At first I considered using roof gutter racks to attach the air dam. Had some advantages but decided it was better to attach to the bottom T slots of the RTT itself. There is definitely chassis flex between bed and cab, and amplified by the cantilevering of the new frame. The cab roof is slightly domed and came to the conclusion that an 1-3/8” was enough center clearance to not slap the roof. Another consideration was trying not to blank out the roll bar antenna or interfere with the front roof panels. This gave the limits for the aero curve.
This is what I came up with.

Also have to account for the opening of the RTT, the roof lip comes forward into the notch of the fairing. Using 8020 for the frame work allows adjustments. The bottom and most of the back is open. All made from aluminum.
Couldn't include the awning in the air dam as it would impact opening the awning. I could ad a tip up filler to bring the top closer to the RTT when closed but being slightly taller it may not make much difference.

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[Rokon]

Here are some shots of the build up.

 

[Rokon]

Scuffed up with Scotchbrite and degreased. Ready for etching primer.

 

[Rokon]

Painted low gloss engine enamel and installed on the truck.

 

[Rokon]

Won't know if there are any mpg gains until next weekend.
Pretty sure I'll see some change though. Looks faster!!

 

[Jaxmax]

I always wonder if putting something similar to a pool noodle under the front edge of RTT and have it shaped like a V to push the air to the side instead of against the front face of camper, or put a bottom on your piece with a rubber piece sticking down close to top of camper. I always wonder why they don’t account for wind drag on the front of stuff like that , hold your hand out the window while driving and feel the drag imagine what the front of the RRT is! Nice, really nice freaking work, sorry I had even doubted you in your earlier post!….Jack

 

[Rokon]

Gave a seal or brush edge some thought for sure. Decided it would be a concern of chafing and spoiling the roof. May try something temporary as an experiment.
Thanks for the kind words. No need to apologize for your opinion! And I appreciate it now.

 

[fourfa]

I did try something like a pool noodle (gray pipe insulation) between the hardtop and my canopy camper. One trip on the highway and the wind blew it out the side. Would need a more durable install than just “shove it in between and hope for the best” lol

 

[Thebigboowah]

Wow. Great build. I simply bought an old snowboard, painted it, and attached with 80/20 45 degree arms and hinge supports.

 

[Rokon]

I'm too old to explain a snowboard on my roof….

 

[madduck]

Definitely looks faster. Ergo: it is.
Good work.

 

[Rokon]

Just an update to this thread.
I'm seeing a 1.5 mpg gain at highway speeds of 75-78 mph. Still lots of bugs on the windshield but very few on the aero mod. Thats my wind tunnel test!
Pretty pleased with the results. Only downside is it does affect Sirius reception so I have to do an antenna relocation.

 

[jensbrown]

Painted low gloss engine enamel and installed on the truck.

nice job

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