MetroMPG's Honda Insight boat tail extension (cardboard) tuft video; ABA test +9.7%

[MetroMPG]

This needs to last 6 months before I start on a "permanent" version (so, more realistically 12 months), so I'll be waterproofing it as best as I can with plastic. If it lasts, it lasts!

I'll tuft test it before wrapping it though, in case I discover I need to make adjustments.

[California98Civic]

Neat prototype project. Nice curve on the tail from the bumper cover.

[ultimx]

Man that looks good. I should make one like that too. Ever consider using balsa wood as a frame?

[freebeard]

That's looking really good. I assume the blue tape running off down the side of the car is for alignment purposes?

When you cover the top (he assumes), will you still be able to get to the straps to remove it? I'm curious about the weight.

[sheepdog 44]

You could buy one of the those large poster frames, and just use the clear plastic to wrap the tail light section. One good good 3x6 foot poster frame should do it.

I'm curious what the structural requirements of a boat tail are. I tend to over think, and would go for a much heavier construction (some might even think aluminum would be required). But you seem to have done it, first using only cardboard, and then secondly using a light minimal 1x1inch wood frame. I guess a boat tail is shielded from the wind by the car, and only really needs to deal with vacuum pressure and the wind speed parallel to it. Can you share your insight on this?

[AndrzejM]

It looks great. Can't wait to see some tuft testing videos. Hopefully you'll roll something soon.

[MetroMPG]

I ran out of cardboard.

Originally Posted by ultimx

Ever consider using balsa wood as a frame?

I think I'll use an aluminum platform/structure and foam for the "good" version. This cardboard one's not going to be heavy.

Originally Posted by freebeard

I assume the blue tape running off down the side of the car is for alignment purposes?

When you cover the top (he assumes), will you still be able to get to the straps to remove it? I'm curious about the weight.

Yup, and yup: I'll make a little hatch on top to get at the inside gubbins.

Weight: well, my first tail (hey, I'm a regenerating reptile!), which was much larger but mostly duct tape & cardboard, only weighed ~12 lbs. But with the wood frame inside this one, it's probably more in the 20-25 lbs range (W.A.G.). I'll weigh it when it's done of course!

Originally Posted by sheepdog 44

You could buy one of the those large poster frames, and just use the clear plastic to wrap the tail light section.

I don't think I'm going to cover the lights. I'm concerned that in some conditions, reflections could hide the lights inside.

I'm curious what the structural requirements of a boat tail are.

So am I!

But seriously, it's not the material, it's the design. You could make the structure from chopsticks if you triangulate enough.

I'm not pretending to be an engineer, but I am triangulating for strength, and the way it's going together, the skin & bulkheads become part of the structure as well. (So as long as it stays dry...)

Also, anyone watching me building this will have seen me at different stages grabbing the frame and wiggling at first, then getting closer to wrenching the rear of the car back and forth as it has gotten stronger. (The tail wagging the car.) Seems strong to me.

Just driving down a smooth road, besides gravity, I don't think there are significant forces at play on a properly shaped tail. The bigger issue (I think) is it also has to withstand a lot of sudden bouncing, jolting, jerking around over bumps.

[NeilBlanchard]

Sweet, sweet cardboard engineering! it you can just fiberglass over the cardboard (post testing natch!), then you will have a great boattail. Borrow 3-Wheeler's design for the latch cover, and you'll be done.

[cRiPpLe_rOoStEr]

Originally Posted by NeilBlanchard

you can just fiberglass over the cardboard

I'll second that. I've already done it a few times, often using some random cotton fabric scraps to replace a small amount of the fiberglass for budget reasons.

[Xist]

I am also inclined to think that you will have random people stopping in the parking lot and asking out loud "What the heck is that?!"

Then they start poking it with a stick.