Aerocap version 3

[California98Civic]

Originally Posted by aardvarcus

Glad to see this being built!

Agreed. Cool project process and write-ups.

[t vago]

Section 1 has finally been skinned. For section 2, the ribs have been glued in. I hope to have section 2 skinned by tomorrow evening - with luck, section 3 will have also been glued in and skinned.

[California98Civic]

Looking good.

[aardvarcus]

I love it! What thickness of XPS is the top skin? Are you getting compound curvature out of that skin? What is your final plan for the finished surface? I am wanting to do something similar for my Tacoma.

[NeilBlanchard]

I think it is 1/4" thick skin.

[t vago]

Originally Posted by aardvarcus

I love it! What thickness of XPS is the top skin? Are you getting compound curvature out of that skin? What is your final plan for the finished surface? I am wanting to do something similar for my Tacoma.

Thanks! As Neil said, the skin is 1/4 inch thick. I would have to say that I am getting approximate compound curves, but for the purposes of what I'm doing, it's acceptable. I intend to coat the surface with an epoxy, then put a few layers of fiberglass on top.

[aerohead]

Looks like money to me! You're back in the oil business.

[t vago]

Sections 2 and 3 have been skinned. It's moving along fairly quickly now, since the worst curves are now gone. Only one more rib needs to be glued in place, then section 4 will be skinned. I will probably also install some anchor foam bars at the base, where the skin ends at the bed.

I finished about 30 minutes ago, hence the night shots of the cap itself. Should have some better pictures tomorrow.

[t vago]

Aerocap is rough-finished. Any further work on it will be to fine-tune the cap and/or harden the shell itself.

I made a mistake with the last rib, didn't catch it in time, and it is sitting about 1/2 inch higher than it is supposed to, as a result. However, I don't think this should substantially affect the reduction in drag due to the cap itself.

The cap itself looks almost identical to the Excel graph representation, which is pleasing to see.

I did a quick test with in-town and highway driving. I have to hook up an MPGuino to get reliably accurate numbers. The built-in trip computer indicates instantaneous fuel economy figures of about 28 MPG at 40 MPH, and 22 MPG while travelling at 75 MPH. For comparison, the truck got around 22 MPG instantaneous while in town, and about 19-20 MPG on the highway.

Once I have the MPGuino hooked up, I will conduct a more accurate A-B-A test of the cap.

I did have a ScanGauge II hooked up to the truck, but it is now with my parents' minivan. My Magnum uses an MPGuino, while our minivan uses the UltraGauge. The UltraGauge does not work with the truck.

I also experimented with using aluminum foil and 3M 78 spray adhesive. It appears to work well enough to seal the foil against the foam skin, and may be easier to work with than the epoxy I bought for the version 2 aerocap. This should allow me to more easily apply one or two sheets of fiberglass to the skin.

Driver's side mirror view


Last rib being glued in


Section 4 skin initial gluing


Section 4 skin final gluing left side


Section 4 skin final gluing right side


Profile view of complete aerocap


Slight rearward view


Left rearward view


Right rearward view


Left forward view, showing curve

[California98Civic]

Originally Posted by t vago

I did a quick test with in-town and highway driving. I have to hook up an MPGuino to get reliably accurate numbers. The built-in trip computer indicates instantaneous fuel economy figures of about 28 MPG at 40 MPH, and 22 MPG while travelling at 75 MPH. For comparison, the truck got around 22 MPG instantaneous while in town, and about 19-20 MPG on the highway. ...

Driver's side mirror view

Those numbers and that picture tell the story well. So if the numbers hold when you get better instrumentation hooked-up you just gave yourself somewhere between a 10% or even 20% increase in FE. That would be pretty amazing.