CARGaerO t'ailer; a hitch-mounted boat tail (Pontiac Vibe)

[Weather Spotter]

keep up the good work!

should we have another meet up to help with the motivation?

[eco_generator]

Looking good. Had an idea similar to this kicking around in my head for my work car. Hitch mounted cargo box with flip down caster wheels or something and handles on the side. I can store extra equipment in the box, slide it off the hitch and roll it on site. And in the meantime it helps a little with my aero.

[Tango Charlie]

Let me know when you're headed this way, Ben!

It's supposed to be 70F tomorrow, so maybe I can get my butt in gear and accomplish something.
Here's some pics taken earlier.
Here I'm gluing on a backer strip for the lower/upper side seam.



And here is a rear 3/4 shot showing the upper side going on. Still using jackstands and a wooden stick to hold it up at this point, until both sides are firmly attached and able to transfer the load through the skin and into the bulkheads.



You can also see the zig-zag trusses that I added between the top stringers. Trying to get as much stiffeness into it as I can, without relying on aluminum angle.

[Varn]

Nice shape.

I'm picking out an older photo, Have you extended the metal frame any from this photo? Are you keeping the guy wires. You have attachment points at the top? I thought I read that. When I used to build coroplast bike fairings I would attach it to the bike frame at 6 points. Two at the nose two in the front and two in the back They were stable without flutter at least at the speeds that I used to ride. They usually used about one sheet of coroplast. Perhaps Tony could jump in.

Originally Posted by Tango Charlie

My experience with coroplast is that it starts looking fairly ragged after 6m to a year. Should be nice and light and give you an idea whether you want to continue improving the design.

[Weather Spotter]

It's looking good! It might be a while till I come that way, but He is the only one that knows for sure

[Tango Charlie]

Originally Posted by Varn

Nice shape.

Thanks. The camera lens kinda distorts it a bit, but once it's on and I can take some video of tuft testing, etc., you'll be able to see it better. But yeah, I'm pretty stoked at how it's coming out.

Have you extended the metal frame any from this photo? Are you keeping the guy wires.

No. and no. Going for the monocoque construction. The kite string guy wires are strictly temporary until the skin is fastened in place.

You have attachment points at the top?

Possibly. WeatherSpotter suggested this too, using straps hooked into the top lip of the lift gate. I'll cross that bridge when I get to it.

My experience with coroplast is that it starts looking fairly ragged after 6m to a year.

Perfect. That's all the longer I need it to last. It will be stored in the garage or under a tarp when not in use, so maybe it will last a bit longer.

Sorry 'bout the lousy iphone pic (good camera bit the dust), but this shows the aluminum angle I'm adding to bolster the skin-to-bulkhead juncture. coroplast strips alone proved to be too flexible.

[brucepick]

Nice project!!

That looks like a cutout in rear bulkhead for loading /unloading cargo. True? If so, nice touch!

A year ago I was working on a coroplast rear spoiler. I too found it needed stiffening using either 1/8" aluminum stock or similar thickness lauan plywood. I ended up with Kamm roof extension instead but that's another thread.

A few pounds of weight is not a bad thing but stiffness and strength are valuable. Any added weight will need slightly more fuel to get up to speed but you are rewarded with longer coasts due to the mass. It only hurts you if you must brake and so kill off your momentum.

Do beware of too much weight very far back, causing t'ailer to flex outward in turns. Strength is good, as I say.

[Tango Charlie]

Originally Posted by brucepick

Nice project!!
That looks like a cutout in rear bulkhead for loading /unloading cargo. True? If so, nice touch!

Yup, full use of the luggage platform will be retained by access through the door in the rear bulkhead. While cutting out that door, the knife slipped and I put a nice gash in the palm of my right hand. One stinkin' brain fart + cutting left-handed + cutting toward myself = one Tim Taylor moment. Took about a week and half and several butterflies for it to heal up.
So ya, so far it's been a pretty typical project for me.

Okay, back to the garage now...

[Beau]

Just curious; what are your thoughts about using the center hitch receiver to carry the brunt of the weight, and one small receiver on each side to control the luggage platform side-to-side movement and dipping?

I have had rear receiver-mounted luggage platform racks in the past, and they all seemed to want to dip to one side or the other.

[Tango Charlie]

That could work, Beau.
To eliminate rocking, I drilled and tapped a hole in the bottom of the receiver to take a 1/4-20 bolt. The bolt tightens against the tongue of the carrier/boat tail and holds it nice and tight. IMO it's adequate, and eliminates a lot of extra fabricating.
The coroplast material introduces some flexing in the structure of the boat tail itself, so I've re-convinced myself to triangulate some angle aluminum reinforcements on the front bulkhead to anchor some ratchet straps.
If I weren't such a perfectionist...