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-   -   Roof top tent flow question (https://ecomodder.com/forum/showthread.php/roof-top-tent-flow-question-34433.html)

Nonhog 10-17-2016 07:11 PM

Roof top tent flow question
 
Wondering if its worth trying to smooth the flow over a Roof top tent. The tent itself is about 12" tall and about 4' square (all closed up in travel mode) plus the height of the roof rack it will sit on. This will be on a mid size 4WD truck possibly over a canopy. I see in my minds eye a vinyl tonneau cover stretched with proper angles front and rear to smooth flow. I am sure this will be a one off custom build. I'm o.k. with that. Will the vinyl buffet in the wind? Therefore requiring a molded part?

Thanks for any input!:thumbup:

BamZipPow 10-17-2016 07:43 PM

Keep in mind that vinyl will stretch when under stress and soften when exposed to the sun. ;)

freebeard 10-18-2016 02:21 PM

Make the custom roof rack a "canopy" that's ≤12" than the height of the cab?

Does it open laterally or longitudinally?

Nonhog 10-18-2016 02:31 PM

I have seen racks made to keep the tent under cab height then there are issues with opening the tent. Besides the loss of canopy height.

Here is what I have Ayer SKY | Tepui Tents | High Quality Roof Top Tents

It can be mounted however one wishes.


Thanks for the replys

botsapper 10-18-2016 03:04 PM

Geodectic frame and fabric skin
 
A great reference for 'basketweave' structure? Maybe use light-weight wire mesh decking or wire mesh fencing panels, conformed and tack welded to an aero-shaped framing. http://jncfence.com/imaget.php?image...feale%2014.JPG

The famous Vickers series of Wellington, Wellesley, Warwick and Windsor bombers used Barnes Wallis very strong geodetic structures for its aerodynamic shapes and covered them with doped fabric/linen skin. The multiple stringers would still keep the aircraft airworthy even with huge framework damaged or missing.
https://www.youtube.com/watch?v=qsm9YT_EZWI

aerohead 10-22-2016 02:07 PM

buffet?
 
Quote:

Originally Posted by Nonhog (Post 524984)
Wondering if its worth trying to smooth the flow over a Roof top tent. The tent itself is about 12" tall and about 4' square (all closed up in travel mode) plus the height of the roof rack it will sit on. This will be on a mid size 4WD truck possibly over a canopy. I see in my minds eye a vinyl tonneau cover stretched with proper angles front and rear to smooth flow. I am sure this will be a one off custom build. I'm o.k. with that. Will the vinyl buffet in the wind? Therefore requiring a molded part?

Thanks for any input!:thumbup:

Unless the fabric is doped it will be aeroelastic and will flutter in the airstream.How much will depend on span and tension of the envelope.
Ideally,you'd have a lead and tail fairing to smooth the air on and off of the tent structure,like member Orbywan has done with the rooftop Coleman AC unit on his motorhome.
http://i1271.photobucket.com/albums/...itled14_20.jpg

e*clipse 10-25-2016 09:15 PM

Whoooo Boy! I'm glad you're working on this! :thumbup:

I also have a Tepui RTT, which I've bolted to a work rack on a 4wd 'Yota.

I love the thing for our off-road adventures, but it's such an aerodynamic disaster, I've been afraid to post anything about it. :(

The way our RTT was bolted to the work rack, there was a 6" gap between the cab and the tent. This diverted a HUGE amount of wind down into the bed, making our dogs miserable.

I was working on a thick canvas cover to run completely over the tent, from the front to the back of the work rack. Unfortunately that project's on hold while I build a new diesel motor for it. (long off-topic story...)

freebeard 10-26-2016 03:31 AM

So now that's two roof-top tents and no pictures. :( How are we supposed to speculate wildly without pictures?

Are these single-cab pickups? Could you make a cab-top panel that hinges 6-8" ahead of the windshield header on a sun visor; that folds 'flat' against the roof? Or is that necessary?

e*clipse 10-26-2016 03:58 AM

Good point! I'll dig around and find something. :)
FWIW, my truck is an X-tra cab, sort of 1 1/2 cabs. I was hoping to fold the RTT back down against the back of the cab while travelling, but it fit too tight to move.

Looking at that random aero thread, there are a few pickup wind tunnel shots. It's pretty obvious why the air wants to slip between the RTT and the cab, instead of simply flowing over the RTT. The whole bed forms a giant low pressure area and that air is trying it's best to fix the problem... :p

-e*clipse

Quote:

Originally Posted by freebeard (Post 525669)
So now that's two roof-top tents and no pictures. :( How are we supposed to speculate wildly without pictures?

Are these single-cab pickups? Could you make a cab-top panel that hinges 6-8" ahead of the windshield header on a sun visor; that folds 'flat' against the roof? Or is that necessary?


ennored 10-26-2016 09:50 AM

Quote:

Originally Posted by freebeard (Post 525669)
How are we supposed to speculate wildly without pictures?

I mounted it on a simple rack as low as possible above my bed (Silverado crew cab short box). I left my tonneau in place. It tucks in pretty nicely behind the cab. Yes there's a gap, but with the tonneau I don't think much air is circulating in there. But I've only taken one short trip. And only took one quick picture. It folds forward and the top ends up below the roof.

http://i240.photobucket.com/albums/f...ps6xywsmqg.jpg


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