CarBEN EV5 Full Sized Prototype Construction - 5 Seat Electric Car From Scratch

[HydroJim]

Any idea what the foam itself weighs in it's current state?

[NeilBlanchard]

The glue is part of it - I used about 3.5 gallons, and the dry weight of that is probably about 4lbs/gal so say 15 pounds of glue? The glue and the foam together are maybe about 100 pounds? Total WAG, you understand. I'll attempt to weigh it without the plywood later this Spring.

I can hoist the back up with one hand, and the front can be lifted, as well. I made a litter frame out of 1x3 wood strapping, and two people can carry it with that.

[TheEnemy]

Originally Posted by NeilBlanchard

The glue is part of it - I used about 3.5 gallons, and the dry weight of that is probably about 4lbs/gal so say 15 pounds of glue? The glue and the foam together are maybe about 100 pounds? Total WAG, you understand. I'll attempt to weigh it without the plywood later this Spring.

I can hoist the back up with one hand, and the front can be lifted, as well. I made a litter frame out of 1x3 wood strapping, and two people can carry it with that.

Thats a pretty impressive weight, when I built the roll cage (Tight for 4 people and a small cargo area) for my Jeep I used 4 20' sticks with about 10' of scraps left over. At 2# per foot that comes out to about 140-150 lbs, and that doesn't include any body panels that I plan on adding to it.

If I was building your project out of tube, I would use 1" .095 wall, approx 200' of it at 1# per foot, so about twice as heavy without even body panels.

[Jyden]

I guess, that you will use epoxy and fiberglass for covering the foam out side and inside? At least that would be my suggestion for making it stiff, wheatperproof and strong. Also the epoxy shuoud not react with the foam.

[NeilBlanchard]

I hoping to use the same glue I have been using - Titebond III waterproof wood glue with fiberglass fabric. I will be testing, and I need to figure out the best method and glue consistency.

[Galane]

Glue won't have the strength needed for covering the foam.

The majority of the structural strength of this vehicle will come from the resin impregnated covering. The foam mostly just keeps the covering braced in position so it cannot buckle under loads. All the compound curves you have will also contribute a lot to the rigidity of the body.

Glass is strong and relatively inexpensive but heavy. Carbon fiber is stronger and lighter than glass but expensive. Kevlar is a possibility, lighter than glass but IIRC not as stiff.

If you could dissolve the foam and glue out after encasing it, the body very likely wouldn't lose anything but the weight of the foam and glue.

[NeilBlanchard]

I want the foam to stay inside the chassis, for thermal insulation at least, and I think it needs to stay in there for structural reasons. The foam *alone* is strong enough for me to stand inside on the plywood temporary floor panels.

Folks here on EM have used similar glue with success. It is glue just like epoxy is glue. I'm using a waterproof glue, and it should be able to work well enough for my purposes. I love that it has no fumes and cleans up with water.

[Vekke]

Looking sweet and nice progress on the sanding going on. I know its hard sometimes to find power to do things as there are so many things to do and just one man doing them.

Someone asked a question how many hours it will take to manufacture fully working consept car from scratch its around 30000 manhours. This car is looking so nice that its at least that much when project is finished.

I would also keep the foam inside composite structure because its stiffens the body a lot plus the insulation help.

For glues testing I would make at least simple beam test. Take two or three similar size beams and and cover them with various adhesives. Meaning that at least test also real Epoxy resin. Cross dimensions 50mmx50mm and length 1.1 meters. Put so many layers of glas as you plan to use in the body. It might be more in corners but rough estimation about 6 layers of 300 g/m2 is at least enough (thickness about 2mm) twill glass fiber. you can also make one pillar so that you take out the foam from inside and see what is the effect to rigidy.

Let the pillars cure according to instructions and test them at the next day. Put the pillar laying on top of two stands which gap between is that 1 meter and start putting weight on top of pillar right to the center point. See how much stress it can take before breaking.

That wood glue might not soak into glas fiber as much as needed. that can be seen in the end of the test. So if there are glass fiber that is not hard your glue is not working properly. You can see something also from the cured part color it should be clear at least with epoxy resing. If its still "white" its not working properly.

[Jyden]

Originally Posted by NeilBlanchard

I hoping to use the same glue I have been using - Titebond III waterproof wood glue with fiberglass fabric. I will be testing, and I need to figure out the best method and glue consistency.

I dont think that will work.

I suggest that you apply tekniques from kayak or boatbuilding, where you cover both the inside and the outside of the foam with glass cloth and resin. I would choose a marine spec resin (epoxy). That would give you a very strong and light composit shell, that are totally wheater proof, and very impact resistant.

I've used these materials in kayk building, and it gives a very strong body with a low weight. I dont think the glue will hold up ind everyday use, or give you the nessesary impact strenght.

[Jyden]

Originally Posted by Vekke

I would also keep the foam inside composite structure because its stiffens the body a lot plus the insulation help.

. It might be more in corners but rough estimation about 6 layers of 300 g/m2 is at least enough (thickness about 2mm) twill glass fiber. you can also make one pillar so that you take out the foam from inside and see what is the effect to rigidy.

It's enough with one layer of glass on each side, when foam is still in the middle. Extra laysers of glass cloth in corners, stress points ect. 6 layers will add too much wheight, and is not needed when the foam is encapsuled with glass and resin on boths sides.