sepp's second aerocap

[bondo]

Sepp, your aero cap is looking very good! Very nice craftmanship too! It is hard to realize how much work goes into these until you start to build one. There are many different methods to construct an aero cap and if it can be molded from a mold, then you not only get the strongest and lightest possible parts, you have the ability to replicate the part.

Here are some photos of how I constructed mine. The first photo is of the armature, which as in sculpture, is a subframework to support the final layer of clay. Clay is a great medium to use for it is non toxic and can be changed swiftly. The next two photos are of the clay work progression and the last two photos are of the finished clay model and the finished part. Like you, I built the cap right on the truck. I then removed it and cast the mold, which is two part, one being the roof and the other being the sides and front structure.

I have finally sold one of my caps and am in the process of building it. I have another sale pending. Having been out of work since August, it is time to create myself a bailout, because I won't be seeing one from the Government.

Keep on building Sepp, with each you learn more and get better, that is how I learned too.

Bondo

[sepp]

thats great work bondo, how usefull are those side and rear windows in practice? im currently planning of leaving out the sidewindows. but that can be added anytime later. your method has its advantages with the clay that can be reworked more easy. it does look expensive, whats the production cost of such one?
i could have gone that way and allow to make several ones to sell, but making a self baring polyester fiberglass structure would cost many 100's of euros. it cost me €80 just to have a thin coat of it on my first cap. though aluminium is actually more expensive for the same surface.
and in the 4 years that i have been driving this one, i have only ever seen 3 or 4 pickups of the same model. so the market is verry small.

anyway, i made some simulations with a program called flow illustrations, tested and compared different models:

YouTube - pickup truck aerodynamics

though "simulation" is a big word

[sepp]

Originally Posted by aerohead

sepp,I tried a spoiler at Bonneville and removed it after only one pass do to the drag it created.That was with the CRX,but the T-100 is also a fastback with the aero shell and I suspect that it would behave likewise.Allowing the air to follow the teardrop path appears to be the best for fuel economy.If you drive into Germany and get the Nissan onto the Autobahn,you might want some downforce a wing or spoiler could provide,otherwise,at "normal" speeds you should be alright.

yup i abandoned that idea, i did a few simulations whith all the posible types and places for a wing or spoiler, but all they seem to do is build up air in front of them wich disturbs the entire airflow over the cap. they just make it worse.

[bondo]

Sepp, the rear window is of some use while on the road for I can see if there is traffic in the lane behind me. For backing up, I have a camera which really is a lifesaver. The side windows are useful, well the passenger side window is. On those occasions when you are pulling up to a road at an angle to turn left, you can see if there is any oncoming traffic through it.

Your construction method is right on for what you need. Again, you are quite a craftsman and your work looks very professional. I do things in fiberglass because I have worked in it since I was 16 years old.

I include a couple of pics of the smoke testing in a wind tunnel I had my cap in. The first is smooth smoke over the center of the lid and the second is the clean separation at the end of the cap. The third photo is of me (the short guy) and Phil Knox, aerohead himself. You'll have to come to Texas and meet him if you can. He is a great guy and we have all learned alot from Phil.

Best of luck on your second aerocap. It is coming along nicely.

Bondo

[aerohead]

Originally Posted by sepp

yup i abandoned that idea, i did a few simulations whith all the posible types and places for a wing or spoiler, but all they seem to do is build up air in front of them wich disturbs the entire airflow over the cap. they just make it worse.

sepp,the flow illustrator images are great.Thanks! The depiction of the teardrop has me in my latest project.If I follow the work of Jaray,or Lay or Fachsenfeld,etc.,the teardrop tail for the T-100 is ridiculously long for a truck.However I still like to camp.So I'm making a trailer which will extend completely to a point long enough to sleep in,with complete gap-fillers between truck and trailer,to create a continuous flow support structure all the way to the tip.------------ On paper,the truck might see 40-mpg HWY.It would only be for camping and such,or any extended holiday excursion.------- Maybe by Summers end,I'll have something to report.P.S. bondo's cap is a real work of art.You should(everyone should) see it in person.

[sepp]

yesterday i prepared everything and got the cap ready so today all i had to do was make the polyester-fiberglass edges, and paint and it would be done!

but that was verry optimistic, i spent this entire hot sunday in a white overall with cap, gloves, goggles and gasmask sanding and grinding the polyester.
though it went better than last time, the result still wasn't perfect and i had to cut out awhole lot of it that was a bit loose or filled with airbubbles.
but this time i bought polyester body filler! small cans to do touch ups on cars, but i ran out of it and it was getting late so it will be for tomorrow if i get the time.



i did drove it to home and back with the cap on and the flaps open, and visibility is great! the flaps are connected to each other, and i installed a windchield wiper mechanism in it, but still need to connect it to the flaps.



stay tuned!

[LeanBurninating]

sepp, naysayers may have their reasons, but I for one am a big fan of the james bond factor.

Hats off to you to staying true to your original plans and seeing them through. I think it looks great! Keep us posted!

[Jetta90GL]

Very nice job sepp. Good idea with the windshield wiper motor too.

So when your done .. the next one will fit a Ford with an 8 foot box right.

Kidding .... I could really use one like that though.

[FastPlastic]

Looks awesome

[Big Dave]

Good work, Sepp!

Glad you simulated the "straight back" option, as that's what mine is.

The performance of holding the boundary layer is about the same but your curved back looks better.