Aero cap construction: 2008 Toyota Tundra pickup

[bdubnelson]

I used schedule 40 pvc and coroplast... I got 22.5 mpg on the interstate the other day! 08 Tundra 5.7L




[url]http://a1.sphotos.ak.fbcdn.net/hphotos-ak-ash4/315943_10150368965139613_654409612_8214351_1222558 611

[bdubnelson]

http://a1.sphotos.ak.fbcdn.net/hphot...22558611_n.jpg

[bdubnelson]

Do you think there is too much slope there towards the tailgate? It was hard to find anything other than a 45deg elbow to put at the back joint there.

[bondo]

22.5 mpg with a 5.7 liter engine is outstanding! Nice looking Tundra too.

Your aerocap does break off a bit abruptly at the end. You might build up the back with two more sections of pvc on some 90 degree joints above the ones at the lower back about 5 or six inches higher. Just close out the taller flat back with some coroplast. You could even gorilla tape in a couple of light plexiglass windows for better rearward visibility.

By doing this, it would decrease the abrupt aft angle you presntly have giving you better attachment of air. The proof will be if you can better the 22.5 mpg with this modification.

Over all very nice effort!

Oooppps. Hice = Nice I need spellcheck.
Bondo

[bdubnelson]

yeah right now I'm at 28deg slope. I was hoping to keep it close to 19-20deg. I was thinking about adding a window but wanted to keep it cheap right now. I only spent about $60 on the cap supplies. The wife doesn't want to drive it cause she cant see out the back... maybe I won't ad a window after all? LOL

[aerohead]

Originally Posted by bdubnelson

yeah right now I'm at 28deg slope. I was hoping to keep it close to 19-20deg. I was thinking about adding a window but wanted to keep it cheap right now. I only spent about $60 on the cap supplies. The wife doesn't want to drive it cause she cant see out the back... maybe I won't ad a window after all? LOL

Like what you've done,and big thumbs-up!
I did want to mention(since you mentioned it),that 28-degrees is an angle Hucho warned us to steer away from like scurvy.
Evidently,at this angle,the separation line will dance back and forth,with a squareback wake one instant,then a fastback wake another.The whip-sawing wake ends up like 'flutter' in aircraft,which can hammer things to pieces.
The wake is intense turbulence with very high drag.
If you must do a simple 'angle' try and do no more than 15-degrees.
Curves are best,but as you now know,more difficult to execute.

[KamperBob]

Originally Posted by bdubnelson

Do you think there is too much slope there towards the tailgate? It was hard to find anything other than a 45deg elbow to put at the back joint there.

Nice work, bdubnelson.

If you want to tweak your PVC frame you could lower the middle a few inches and raise the back for a longer and less aggressive arch (as Phil mentioned). Note that plumbers use a trick to achieve less than 45-deg bends using a pair of connectors with an out of bend plane jog or offset. Alternatively, you could use 10' pieces without any elbows. Instead, make some nip cuts say 1/2 to 3/4 of the way through the pipe on the inside of the target bend areas. Kerf cuts do weaken the structure some so leave enough material on the outside to hold itself together. Reinforce criss crossed pieces to each other using zip ties, for example, or other means. Cinching down the coroplast skin can also add strength.

I'm curious whether your 08 Tundra is 2WD or 4WD. Also what final drive ratio and wheel size. Or knowing what RPM at 60 mph would allow others to make comparisons. Presumably your 5.7L is paired with Toyota's new 6-speed tranny which I understand can TC lock in the top 3 gears which is a yummy power train. My 02 Tundra (Limited xCab 4WD) has 4-speed and 4.7L and my best highway MPG is 22. That's not with an aero cap but was hyper miled. So your record high score might be even better. (You definitely need multiple tanks to iron out measurement noise - not just run with first fill results after AB change - as you probably know. )

Rock on!

[bdubnelson]

thanks KamperBob. Yeah I had to put some cuts in it to get it to bend to where it is now. I think I'm going to lower the middle framing and make a few more cuts to see if I can lessen that slope. We'll see. The first trip I made with the cap had a little wind and I'm sure that helped. So I think that getting a few trips in the books on the interstate will help to get a true average. Right now my overall average is close to 17mpg. thats up a bit from close to 16 before. Also yes, I have the new 6 speed transmission and 275/70/18 Michelin tires.

[bdubnelson]

I made some alterations this weekend and lowered the middle of the cap. The angles are a little better staying in the teens along the back and hitting 20deg about 2ft from the tail. Over the last foot its about 25deg slope. I'm seeing more turbulence now than before though. I'm considering making some airtabs to help the air diffuse at the tail to lessen wake and turbulence. Anyone else try this?

[BamZipPow]

Suggestion to move bdubnelson's build into it's own thread to keep this thread on it's own track.