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GRP tub out of flat sheets
smart51 - 27/5/08 at 02:17 PM

I'll be starting my GRP inner tub in a week or two. I've been working on the design of a buck which is quite complicated but made entirely of flat sides. So i've had another idea. Make lots of flat sheets of GRP and bond them together. The problem is I don't know how strong the bonds will be.

If I bond 2 sheets together at 90° using bonding paste or resin thickener and chopped strands with a nice 20mm radius on the inside of the corners. will it be tough enough to withstand general car use? Rescued attachment GRP.JPG
Rescued attachment GRP.JPG


worX - 27/5/08 at 02:20 PM

I think the bonded edges will be very strong.

If you are doubtful why don't you used stronger chopped strands or CF?

Steve


designer - 27/5/08 at 02:43 PM

I think you might have to tape the outside too.


tegwin - 27/5/08 at 02:45 PM

I built a hovercraft using a similar method...

Chop some thin PU foam sheet into the correct shape.....Laminate both sides with fiberglass and vacuum bag it to get rid of the air...

Then join the panels together with a fillet and thin taped seam on the inside and glass on the outside....

By using the foam core you need less glass and get much stiffer pannels!

Worked very well....reaaly strong!


And if you really want light and stiff, use kevlar instead of glass to laminate the pannels.... You car would be bullet proof too

[Edited on 27/5/08 by tegwin]


smart51 - 27/5/08 at 02:52 PM

What do you mean "tape the outside"? Do you mean grinding the pointy edge back and glassing over it? Rescued attachment GRP.JPG
Rescued attachment GRP.JPG


Mr Whippy - 27/5/08 at 02:57 PM

quote:
Originally posted by smart51
What do you mean "tape the outside"? Do you mean grinding the pointy edge back and glassing over it?


yip do the insides first then grind the corners round before laying the outer tape as the cloth will pull away trying to do a 90 angle. This is also how some boats are built.


Volvorsport - 27/5/08 at 04:33 PM



all that tub is flat sheet bonded to the spaceframe with polyurethane , then laminated into the tubes with kevlar carbon . the whole tunnel is kevlar .

i could (and may still) infill with one inch foam heet and make it into sandwich construction .

a much better idea is to use grp/ally honeycomb sandwich and laminate that in .


turbodisplay - 27/5/08 at 05:05 PM

If you need a large raius a 90 mm coving length would do the trick.
You can get expanded polystyrene ones to do the job, just cover it in foil to prevent melting it with the resin.I used this stuff to make long curved sections on my car body- very good!

Darren