[NeilBlanchard]

I am going to reinforce the attachment points for the suspension subframes, of course. They will be sleeved through to reinforcements on the back, and they will cradle the weight.

The bottom and the sides of the chassis form a giant 'U' channel and the continuous fiberglass surfaces on the outside and the inside, is going to be one of the stiffest structures imaginable. The only openings are the windows, so the entire side of the foam there is about 6" thick and this is orders of magnitude stronger than most other structures. There is a airplane with a composite sandwich fuselage that has just a 10mm thick foam core...

The longitudinal dividers in the battery bays will form ribs in the floor, and the 1" thick floor panels are going to be screwed into the chassis, strengthening it further. If needed, I can have long metal 'U' channels fabricated to "line" the center battery bays to act a long box beams in the floor.

With just the plywood subfloor I had inside, the chassis of foam alone was strong enough for my 245 pound self to be inside.

I've worked with epoxy glue and it is also somewhat bendable and it too softens up in the heat. So I don't think I am giving up on much strength - if any at all - by using Titebond III.

The glue is soaking into and adhering to the fiberglass very well indeed, and glass is 7X a strong as steel in tension. The glue is what I have been working with all along and it is a great match with this foam. The joints are far stronger than the foam itself.

Oh, I have used this glue with old cloth to make the rear wheel covers on my xA - I stretched the cloth over the plastic wheel covers, daubed on the Titebond III, and spray painted the outside only, and they have totally been fine through rain and snow and ice for almost a year, now.

I'm going to test these pieces and I will improve things as I go along, if needed. This is a malleable process.

I REALLY appreciate all of your concerns, and I am taking lots of advice from people on this forum and others, too. The roughened surface idea came from someone here on EM, and way back at the beginning of the process, I worked in the Smart ForTwo windshield (instead of a totally complex custom one that I had originally come up with) - and a whole lot of other smaller things along the way. ALL of those discussions were invaluable to me and this design; whether or not they get used.

One of the strongest suggestions I got from many people was to start with an existing car, and modify that - like what Dave Cloud did with his Dolphin. And I may still regret not going that route! But with my skill set, and the fact that I started with the 3D computer model (which is unusual, I think?) I am glad that I have done it the way I did.

I went back and forth several times between doing a composite sandwich and a tube steel chassis. In the end it came down to an excellent suggestion (probably from someone here on EM?) to get the Phlatboyz PhlatPrinter III kit - that made it possible to translate the virtual 3D model directly to a physical reality. So, at every step along the way over these past 3+ years I have been working on CarBEN EV5, I have been working through each and every challenge along the way. And working with this glue over the last year and half, I am confident that it will work with the fiberglass, too.

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The link that Galane posted on the three Titebond glues mentions that Titebond III is 4,000 PSI. And the Dow XPS foam is 25PSI - it is quite springy and quite strong right up until it pops.

How strong is epoxy? And what about typical white EPS or closed cell polyisocyanurate foams?