Designing a tail extension for the first-gen Insight

[RobertSmalls]

I meant "Is 13° a sufficient departure angle?"

I think 13° will be fine. A quick Google search shows city buses for sale with 8°-12° departure angles, so we'll have no problems on the road. Driveways should also be okay, I think.

[Wonderboy]

I hope you've got some places you know are larger than normal dips and road angle changes that you can test on. There are some pretty beastly aprons I can think of down here. One I nearly deployed my old subaru's airbags on for approaching too quickly and whacking the tow hooks (that's the public library entrance too - you'd think they'd fix that potential liability, being public property and all), and the other one is my own driveway. If you need to do extensive testing, you can either make the 4 hour trek down here, or kiss some ass for me to get out the laser sight and measure the public library's entrance angles

[jime57]

Originally Posted by RobertSmalls

I meant "Is 13° a sufficient departure angle?"

I think 13° will be fine. A quick Google search shows city buses for sale with 8°-12° departure angles, so we'll have no problems on the road. Driveways should also be okay, I think.

A city bus is a poor example to use when considering an Insight. The wheelbase of an insight is 74.5 inches. The wheelbase of a city bus might be 300 inches, or more. And the length of the overhang on the bus is unknow, but on a percentage basis is much smaller than you are considering.

If it were me, I'd work the actual math and look over the conditions in which you will be driving. But then again, it is your material cost and time

[3-Wheeler]

Originally Posted by Wonderboy

...or kiss some ass for me to get out the laser sight and measure the public library's entrance angles ...

Actually, I measured the angles on my driveway by making use of a bubble level that has an adjustable angle on it.

My entrance is angled a total of 8 degrees, combining the angle of the apron and the dip in the street, where they meet.

I'll try to work up some "math" to address the issue, but from the streets and aprons I've seen, everything looks pretty doable.

Jim.

[dremd]

Originally Posted by 3-Wheeler

Does anyone know the source of these tail lights?

I like the large size, square shape, and that they have back up lights built in.

Or how about some other lights that are similar in shape and size?

Also noticed that the license plate light is similar to Basjoos. Where are these from?



Thanks, Jim.

All of those lights are available from a trailer supply. We have 3 of them here if anybody cant find a set, hit me up.

[dremd]

Originally Posted by 3-Wheeler

Actually the cost of cardboard/fiberglass versus foam/fiberglass is almost the same.

The glass will cost about $30.
The foam board will cost about $30 (1-1/2 sheets at 2in thick)
The epoxy resin will cost about $100 (one gallon)

you should be able to get a gallon of epoxy resin from Epoxy : Epoxy Resins and Hardeners shipped well under $100
I've purchased almost $ 3000 worth of supplies from them in the last few months, and they haven't failed me yet.

But if it were me, I'd lay it up with vinyl ester Polyester Resins
and woven roving or better I use 7725 for moulds, but

I do however believe you are underestimating you materials for a boat tail.
If you want to come on down, I have a chopper gun now :-)

[dremd]

Originally Posted by jimepting

ort. I also know from personal experience that resin is not compatible with styrofoam. I have tried to mix it in syrofoam cups and it just disolves the cup. A while back I discussed this with someone in the ecomodding community who indicated that this problem could be sidestepped by painting the finished styrofoam shape with a water based latex paint before fiberglas overlayment. No direct experience, but I've heard it.

depends on the resin, the styrofoam, the release agent(s) and if you sprayed gelcoat first.
I've had good luck with using Urethane Foam , Expanding Marine Polyurethane Foam in a laminate as long as the resin kicks quickly, and you don't try and vacuum bag it (crushes foam cells).

I have also sprayed gelcoat / enamel paint over that foam then a mould release and have 0 issues pulling the mould.

[dremd]

Originally Posted by 3-Wheeler

Robert,

You won't have any trouble with the epoxy resin. I've used both over the years, and West System makes a very good product.

I'm with you 100%' but can also see no differeance between the west system, and the us composites epoxy.

Originally Posted by 3-Wheeler

I bought the mixing plungers with my order. The epoxy has it's own plunger/dispenser, and so does the hardener.
Highly recommended/ totally worth the$, if you are doing much work at all, otherwise use a scale.

Originally Posted by 3-Wheeler

One pump from each container into a Glad-Wrap plastic cup, mix up for a minute, and you are set to go. I purposely mix bubbles into the mixing operation, and then smooth out to remove them when I wet out the cloth.

Just fyi, i've been using all sorts of off brand plastic cups with Epoxy and never had an issue, just don't sweat it.

Originally Posted by 3-Wheeler

Make sure to wear a protective glove when handling, so as to make clean up much easier. Although the epoxy is easier to clean up.

If you don't have disposable gloves, dont start. I've used vinyl (last about 20 mins with epoxy exposure), nitrile (as far as I know last forevor), latex works good, but tears easily, and nitrile/ latex which are my personal favorite.

Originally Posted by 3-Wheeler

Over the years, I've had way more trouble mixing polyester, because I can easily lose count of how many drops of hardener I put in when interrupted for some reason. To me it's much more tedious. Some of my mixes have turned out, well, let's just say, not too good!! Either it goes too quickly or takes days to set up properly.

Been there many, many times and pounded my head everytime.
few recommendations
1) work polyester in warm weather >50F !!!!biggest one for me!!!
2) measure twice, pour once. a decent scale is killer for polyester.
3) get an external mix gun, I like mine, but you have to pay close attention to resin output as well as MEKP output, otherwise you are screwed.
4) too much is every bit as bad as too little!
5) use epoxy

Originally Posted by 3-Wheeler

The epoxy is a little thinner, and but wets out the cloth fine, and really is very easy to work with. Plus like you said, the smell is much better with epoxy.

Epoxy wets out glass like a dream, if thin is an issue use a filler, my 2 favorites are 3m glass bubbles, and milled fibers.

Originally Posted by 3-Wheeler

I have noticed on sharp corners, the epoxy does not hold the cloth tightly around the bend like polyester does, or even Elmers Wood Glue for that matter, and that's where vacuum bagging comes in. But if I'm going to vacuum bag, I try to keep the vacuum down to just enough to hold the material tight. Too much vacuum can distort the shape of the part, especially if it's relatively weak foam. Then a heat lamp comes out to accelerate the setup time.

If you have something with tight bends that you don't want/ cant bag put down a thin coat of epoxy, let it tac up, then use the tackiness of the epoxy to hold your glass/ fiber in place.


I don't mean to pick apart your post at all, I just saw it as a way to share some of what I learned in the last few months.

[dremd]

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for anybody concerned with where to fit license lights, these always wor and require 0 space

[jime57]

To take the boattail discussion in a very slightly different direction, does it make sense to construct the boattail in sections? I'm thinking of about three sections, a top, a bottom, and a back, with a clean seam between. This approach potentially has disadvantages, but it also has several advantages:
1. It obviously facilitates the tweaking of the contours of the various sections separately,
2. It allows for the rapid testing of alternate "sectional" ideas, even the total length. The pieces could be ready,
3. It facilitates an essential goal, IMHO, of keeping the road clearance within realistic bounds, while significantly improving performance.

At the end of development, one could simply bond the sections together and lay a final layer of fiberglas over the whole thing.

The risk, it seems to me, is that the improvements in Cd from such an approch might be disappointingly small.