would a truck cap give me better mpg than nothing?
02-08-2011, 05:10 PM
#12
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thanks guys. ill try it out till we get some warmer weather. 1. because i get snow every whre in there and 2. because i wanna see if i van get better milage. ill just have to wait and see!
02-08-2011, 05:44 PM
#13
Aerospace Engineer
I would be surprised if anything besides that aeroshell improved aerodynamics enough to offset the increased weight and improved fuel economy. It looks like a Prius because the shape of the shell and the Prius are both as close as possible on the two platforms to the ideal low drag teardrop shape for minimum drag coefficient.
From the factory, the open bed with raised tailgate produces a vortex behind the cab to help the majority of the free stream air pass over the back of the truck instead of into it. This limits the separation zone behind the truck which causes drag.
Lowering the gate or installing a turbo net doesn't allow the vortex to form and causes the free stream to "crash" into the back half of the bed, causing extra drag. (This is what the previously mentioned mythbusters episode found) Also, the separation zone may be increased.
A full camper shell adds some streamlining, but this is largely negated by shaping the back of the truck like a brick and increasing the separation zone to that of a full size SUV. Add the extra weight of the shell, and you may actually lose economy with an older, heavier shell.
I would guess a hard or soft tonneau cover would be in between stock and having the gate down. The cover would probably decrease the vortex behind the cab and the free stream would again "crash" into the rear half of the cover, but the stepped transition may limit the separation behind the tailgate. Hard to say for sure without a wind tunnel test. Between the two, a properly tensioned soft cover (one that doesn't flap) would perform better if its lighter.
From the factory, the open bed with raised tailgate produces a vortex behind the cab to help the majority of the free stream air pass over the back of the truck instead of into it. This limits the separation zone behind the truck which causes drag.
Lowering the gate or installing a turbo net doesn't allow the vortex to form and causes the free stream to "crash" into the back half of the bed, causing extra drag. (This is what the previously mentioned mythbusters episode found) Also, the separation zone may be increased.
A full camper shell adds some streamlining, but this is largely negated by shaping the back of the truck like a brick and increasing the separation zone to that of a full size SUV. Add the extra weight of the shell, and you may actually lose economy with an older, heavier shell.
I would guess a hard or soft tonneau cover would be in between stock and having the gate down. The cover would probably decrease the vortex behind the cab and the free stream would again "crash" into the rear half of the cover, but the stepped transition may limit the separation behind the tailgate. Hard to say for sure without a wind tunnel test. Between the two, a properly tensioned soft cover (one that doesn't flap) would perform better if its lighter.
02-09-2011, 06:50 AM
#14
Senior Member
Well said BigIrish, well said.
I would be surprised if anything besides that aeroshell improved aerodynamics enough to offset the increased weight and improved fuel economy. It looks like a Prius because the shape of the shell and the Prius are both as close as possible on the two platforms to the ideal low drag teardrop shape for minimum drag coefficient.
From the factory, the open bed with raised tailgate produces a vortex behind the cab to help the majority of the free stream air pass over the back of the truck instead of into it. This limits the separation zone behind the truck which causes drag.
Lowering the gate or installing a turbo net doesn't allow the vortex to form and causes the free stream to "crash" into the back half of the bed, causing extra drag. (This is what the previously mentioned mythbusters episode found) Also, the separation zone may be increased.
A full camper shell adds some streamlining, but this is largely negated by shaping the back of the truck like a brick and increasing the separation zone to that of a full size SUV. Add the extra weight of the shell, and you may actually lose economy with an older, heavier shell.
I would guess a hard or soft tonneau cover would be in between stock and having the gate down. The cover would probably decrease the vortex behind the cab and the free stream would again "crash" into the rear half of the cover, but the stepped transition may limit the separation behind the tailgate. Hard to say for sure without a wind tunnel test. Between the two, a properly tensioned soft cover (one that doesn't flap) would perform better if its lighter.
From the factory, the open bed with raised tailgate produces a vortex behind the cab to help the majority of the free stream air pass over the back of the truck instead of into it. This limits the separation zone behind the truck which causes drag.
Lowering the gate or installing a turbo net doesn't allow the vortex to form and causes the free stream to "crash" into the back half of the bed, causing extra drag. (This is what the previously mentioned mythbusters episode found) Also, the separation zone may be increased.
A full camper shell adds some streamlining, but this is largely negated by shaping the back of the truck like a brick and increasing the separation zone to that of a full size SUV. Add the extra weight of the shell, and you may actually lose economy with an older, heavier shell.
I would guess a hard or soft tonneau cover would be in between stock and having the gate down. The cover would probably decrease the vortex behind the cab and the free stream would again "crash" into the rear half of the cover, but the stepped transition may limit the separation behind the tailgate. Hard to say for sure without a wind tunnel test. Between the two, a properly tensioned soft cover (one that doesn't flap) would perform better if its lighter.
All the late model pickup truck beds have higher sides and tailgates. This enhances to formation of the spinning vortex you speak of which forms behind the cab and within the truck bed. All the big three have a wide flat top to the tailgates now too. This reduces turbulence as the air flowing over the spinning vortex impacts the top of the tailgate. It is kind of like having an aeroshell made out of air in your bed as you drive but it robs energy, gas, from the engine to keep the spinning vortex going.
Wind tunnel test show that there is an fairly good increase in lift caused by installing the Aerolid. This actually counters the added weight of the aero camper at speed.
Some of the wind tunnel testing on the Aerolid was done in your area BigIrish in Allen Park, Michigan.
02-09-2011, 08:33 AM
#15
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A cover must improve mileage. If one looks at the pattern of snow in the back of a truck, the wind hits the tail gate and causes the snow to build up against the cab with little by the tail gate. When I had a flat bed this wasn't an issue.
02-09-2011, 02:22 PM
#17
Aerospace Engineer
All the late model pickup truck beds have higher sides and tailgates. This enhances to formation of the spinning vortex you speak of which forms behind the cab and within the truck bed. All the big three have a wide flat top to the tailgates now too. This reduces turbulence as the air flowing over the spinning vortex impacts the top of the tailgate. It is kind of like having an aeroshell made out of air in your bed as you drive but it robs energy, gas, from the engine to keep the spinning vortex going.
Wind tunnel test show that there is an fairly good increase in lift caused by installing the Aerolid. This actually counters the added weight of the aero camper at speed.
Some of the wind tunnel testing on the Aerolid was done in your area BigIrish in Allen Park, Michigan.
Wind tunnel test show that there is an fairly good increase in lift caused by installing the Aerolid. This actually counters the added weight of the aero camper at speed.
Some of the wind tunnel testing on the Aerolid was done in your area BigIrish in Allen Park, Michigan.
Bondo, do you work for the company that makes the Aerolid? You seem to know about aerodynamics. You should probably clarify that lift statement. Although it is possible the aerolid produces lift to offset its weight, it can't negate the effect its mass has on the truck when accelerating.
02-09-2011, 06:02 PM
#18
Senior Member
Thanks for the clarification BigIrish.
Having gone to the School Of Hard Knocks, I sometimes show my lack of Formal Education, of which I have a great respect for the latter. I was fortunate enough to land a job a Ford's West Coast Design studio for several years back in the latter 80's and have sculpted clay for heavy truck manufacturers, alot of aero on those big rigs, and other consumer and transportation products.
Having gone to Kettering, you may have had my good friend Dr. Hargrove as a teacher. Good for you for having chosen Engineering as a profession. Me, I am far too right brained. My wife on the other hand set the curve in Differential Equations when she took it!
I agree with those here who don't like the looks of the aerodynamic camper I designed and built. It takes some getting used to. It is a versital product which replaces a generic squared off camper for those who want to cover the bed of their truck and get superior gas mileage to boot. As you can see in the previous pictures in this post, it can be raised up into a cab high camper and driven like that. If a need to haul tall cargo comes up, you can remove the whole roof, leaving the lower part attached to the truck bed. It isn't for everybody, but then just anybody won't want one.
Having gone to Kettering, you may have had my good friend Dr. Hargrove as a teacher. Good for you for having chosen Engineering as a profession. Me, I am far too right brained. My wife on the other hand set the curve in Differential Equations when she took it!
I agree with those here who don't like the looks of the aerodynamic camper I designed and built. It takes some getting used to. It is a versital product which replaces a generic squared off camper for those who want to cover the bed of their truck and get superior gas mileage to boot. As you can see in the previous pictures in this post, it can be raised up into a cab high camper and driven like that. If a need to haul tall cargo comes up, you can remove the whole roof, leaving the lower part attached to the truck bed. It isn't for everybody, but then just anybody won't want one.
Last edited by Bondo; 02-09-2011 at 06:05 PM. Reason: edit text
