Honda Insight Tail Extension Project

[Varn]

Hi Donee
The biggest parts that I have made with vacuum bagging is probably on the order of 20-30 square feet with 20 oz of material. The fun begins when you can't get a vacuum because of leak. For the larger parts such as this, I would use a slow or ultra slow set epoxy. The trick I have found is to spray glue the reinforcement cloth to the mold. I have only had one time where I couldn't get vacuum and my part, a recumbent bicycle seat came out with too much epoxy.

If I were doing some production work vacuum infusion might be an advantage but thought it to be unnecessary for the size of and thickness of parts that were being made. Perhaps you might share some of your projects.


From an ecological point of view, composites are bad. Lots of hydrocarbons are used to make the epoxy Lots of industrial operations into make the cloths Lots of waste between the layup and final product.

In addition it is hard maintain a healthy work environment. The work should be done outside. 3wheeler knows.

Originally Posted by donee

Hi Varn,

The issue (for the benefit of others) is how fast you can mix, and apply it. Its open time is short, and defenitaly variable based on the shape of the mixed container, and the final shape of the part. The practicality of this, is that really good parts can only be made so big by a single person. If the epoxy is not at the same state of cure in layers, its not going to make a good part. That is, if you have one end of an object half cured, and then apply freshly mixed epoxy on the other end there is going to be a
"knit" line that is prone to failure.

Allot of the problem can be eliminated with the vacuum bagging technique called "vacuum infusion" The epoxy is pulled into the matrix uniformly and quickly by this method. Two people can impregnate structures up to 50 foot long in a matter of hours, with a superior build quality. There was a video on the internet of this done by a Dutch boat builder. It was quite remarkable how straightforward and undramatic the impregnation was, in comparison to traditional techniques such as hand-lay-up.

[alohaspirit]

read through all 29 pages just now


what a great project!

your pictures and write-up are great and very easy to follow

and im sure there were a lot of mad scientist laughs as everything came together


i look forward to updates when the numbers come in and everything gets smoothed out



note:
have you ever considered back up sensors?
(theyre light, install flush and would take the guesswork out of reversing)

[3-Wheeler]

Originally Posted by Varn

....From an ecological point of view, composites are bad. Lots of hydrocarbons are used to make the epoxy Lots of industrial operations into make the cloths Lots of waste between the layup and final product......

Yes, from this limited viewpoint, composites may not be the most eco-friendly, however there is another viewpoint...

Take any device that will allow us to live environmentally friendly over the long-term - such as wind generators.

Any company making composite blades for these generators has several issues to consider...

1) The process of making the blades is not the most eco-friendly as you have pointed out above.

2) However, if we don't make blades for these turbines and harvest "green wind", how long before we run out of fossil fuels? What about the impact of that on the environment?

3) Over the long-term, I think the fossil fuel tail-pipe emissions far outweigh the small amount of hydrocarbons from making blades that can provide power for 1000's of people in the area of the wind generators.

No, the decision to use composites to help mankind over the long haul will mean that more of these will be designed and built to achieve higher levels of sustainable energies for everyone's future. And we must do this while the cost of fossil fuels is still reasonable to allow this to happen.

Let's not wait until fuel cost is so high we can not afford such sustainable forms of energy.

Jim.

[3-Wheeler]

Originally Posted by alohaspirit

....note:
have you ever considered back up sensors?
(theyre light, install flush and would take the guesswork out of reversing)

Ah yes, the backup sensors have been looked at several times now, and I think that will be an addition made to the tail next year, when the weather is again warmer.

Thanks, Jim.

[discovery]

Hats off for this project. That is what we need more people like you Jim, to share and show the world how is done. With small amount of money great results in FE. Good job and keep it up.

[3-Wheeler]

Last night after getting home, it was obvious how little wind there was outside. Now the question became... Shall we make a mileage run or not.

After supper, I jumped in the car and headed out to check a road that was exceptionally flat for at least one mile. After driving about 8 miles, I found there was quite a bit of traffic there. In fact too much to attempt any runs.

Next another longer road, but not a flat, was checked and again found way too much traffic at 7:00pm.

So I drove all the way back home and checked the congestion of another road, that while possessing a flat section of about two miles long, was slightly up-hill the entire way. Lo-and-behold, this road had little traffic, with about 1 or two cars every minute or so. This road looked doable, so I turned around at a good spot, got up speed and pressed the Insight "reset" button for the Fuel Consumption Display.

I repeated this process three times each direction, recording the fuel mileage after each run. At this point in time I had the tail installed and now it was time to drive back home to remove it, and place the stock Honda lights back on. I did not bother putting the rear bumper facia back on as this would take too much time, since the rear wheel covers need to come off as well just to mount it. This also meant that I had no rear license plate or illumination light.

I found that the two miles really only allowed me to track mileage for about 1.3 miles or so, and the Insight seems to only update the FCD display every 0.6 miles or so. I could not use the ScanGauge to get accurate readings since the lean-burn feature of the engine plays havoc with this reading.

It seems that the only way to really get solid readings would be to discover a flat, unpopulated road that is 5 miles long or so, and drive there for a testing period. That would also mean detaching the tail and leaving somewhere while the "stock" configuration is tested.

__________________________________________________

Last night's conditions:

Speed: 56 mph
Temp: 52°F
Wind: Calm (maybe 3 mph wind at times)
Road: runs mostly East-West
- Freshly paved five years ago
- Reasonably flat with slight grade (10 ft over two miles)
- Low traffic in my direction with several cars traveling in opposite direction
- At no point was I closer than 1/4 mile to car in front of me in same direction
- I tried to hug the right side of lane to minimize wind disturbance
- Only had time for A-B testing, not A-B-A
- Test section flat only for two miles
- Marginally long enough for run of 1.5 miles
- Insight has limitation of display updating every 0.6 miles or so
- Finding longer road is highly desirable (Insight limitation)

The tail shows an increase in fuel economy of 10.27% at 56 mph over a short course of 1.3 miles.

This table shows the difference is fuel consumption with and without the tail. Note that underside of the car is 90% smooth, and the original design of the body shape is highly optimized by Honda, so the improvement due to the tail is smaller than MetroMPG's, as has been expected by several forum members.



But how is this mileage increase affected at other speeds?

The following table makes several assumptions about the relation between rolling drag (Crr) and aero drag. It assumes that the mix between the two are equal at 45 mph. With this assumption made, we can then establish how much fuel we will save at other speeds besides 56 mph.

Note that the table below works on the premise that Crr changes directly with road speed, and that air drag changes as the square of the speed.



And this is a graph of basically the same information in the table.



EDIT: parting note: some of the table and graph information still looks funny to me, and I will post another, more clear description later, but in the mean time I hope this helps.

Jim.

[wyatt]

Not to get picky on you Jim, but your graph should say FE increase on the y-axis, not Drag Reduction (%). The % Drag should be approximately 2 times as much as the FE increase (maybe 21% drag reduction at 56 mph), and would be measured by coast down testing. With that being said, very impressive! I was guessing 12% myself, just based on the SedanKamm I had built earlier this year, and figuring you would get double the results (yours is both top and bottom, and tapers on the sides)

EDIT: I retract my previous statement, I see what you were doing, your posting showed the first picture twice, and I never got to see the second one.

[3-Wheeler]

Originally Posted by wyatt

Not to get picky on you Jim, but your graph should say FE increase on the y-axis, not Drag Reduction (%). The % Drag should be approximately 2 times as much as the FE increase (maybe 21% drag reduction at 56 mph), and would be measured by coast down testing. With that being said, very impressive! I was guessing 12% myself, just based on the SedanKamm I had built earlier this year, and figuring you would get double the results (yours is both top and bottom, and tapers on the sides)

EDIT: I retract my previous statement, I see what you were doing, your posting showed the first picture twice, and I never got to see the second one.

Hi Wyatt,

Actually I have to say a big thanks for you getting "picky"!

Why?

Because you just reminded me that a 10% increase in gas mileage is really due to roughly a 20% increase in body shape aero efficiency.

I had forgotten about this "little" detail in my attempt to qualify this effect more succinctly in the table and graph above.

I will try to rectify the current situation in a further post, and hopefully make it more clear on how the aero drag reduction interacts with the rolling resistance and yields total vehicle drag.

Thanks again Wyatt.

Jim.

[ultimx]

Wow, over the course of a couple days I have been reading this thread in awe of the amount of work done. I am now intersted in the actual making of the boat tail for my car, unfortunitly, I don't see it done anytime in the near future but I would like to make the attempt and figure out a design that works well for my car after more research on this site. Thanks for the insight on how u actually made the boat tail as I am probably going to be doing the same thing somewhere down the line, just of matter of when. Great job and I can't wait for more information on your build.

[discovery]

Wow 91.43 MPG at 56 MPH that is Wow