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Thread: Rear bulkhead suggestions

  1. #1

    Rear bulkhead suggestions

    I'd like to pick the brains of all the fibreglass experts out there please...

    I've tried to limit the amount of body shell cutting required for the new chassis, but it's mid engined, and most shells will have either a back seat or a bulkhead moulding where the engine wants to be, so some cutting is inevitable - as in pic 1.

    Pic 2 is a simplified representation!

    I've got a bit of experience with fibreglass, so could probably muddle through making a new bulkhead, but ideally I want to simplify and demystify it as far as possible, for someone who has never had the pleasure of mixing a pot of resin.

    The plan is to produce a simple "one sized fits most" adaptable bulkhead (pic 3), that drops over the back of the chassis tunnel and bulkhead, that can be trimmed to size relative to the body shell (pic 4).

    My question is, what's the easiest way to bond it in? Obvious enough from the back (uneven) surface I suppose, by sanding back a couple of inches or so on the shell and new bulkhead and then laminating over the join (pic 5), but this would look messy on the smooth inside surface (pic 6). Is there an easier/neater way that I'm missing- maybe just grind out the join on the inside by 1/2 an inch or so and fill with fibreglass filler?. Is fully laminating over the join on the inside absolutely necessary if the outside is done adequately? Is there a relatively easy way of making a neat L shaped flange to cover the inside join?

    Sorry about the barrage of questions. All suggestions very welcome.

    Ed
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  2. #2
    And picture 6...
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  3. #3
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    You could bond a moulded fibreglass panel to the existing body tub by scuffing up the gel coat and using Tigerseal or some other polyurethane adhesive. The mounting flange could be internal (i.e. hidden when viewed from inside the car) to tidy up the visuals. You could also bolt through the flange at intervals for extra security, which would only be visible from underneath the car.

    I think the "one size fits most" approach is a good one, because the basic bodyshell moulding around that area is pretty much identical for all models of Nova. The only minor difference might be the additional 1" of depth which we believe was added to the Mk2 (the other 1" came from the "eyebrow" over the windscreen header rail).

    I don't think fibreglassing the panel into place is necessary, provided the mating surfaces fit closely enough.

    Lauren
    only Pythagoras can save me now!

  4. #4
    weld in flat steel sheeting with returns,,,body could then be bolted to it

  5. #5
    If you glass in the panel you lose the unusually-easy-access-to-alternator-adjustment that the chassis design had created... Lauren's bolt assisted suggestion sounds fine - most of that area has bcome more cosmetic than structural. I wonder if the MG soundpoofing/heatsheids will transfer over?
    It's a 52 year old car and everything works, just not always at the same time.......and it's probably about to get jealous!
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  6. #6
    Senior Member bushboy's Avatar
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    I'm with Alex. Make the panel a "bolt in place" affair as that will then maximise access to the oily bits when needed. A nice neoprene seal could be incorporated to seal out any fumes and once trimmed with carpet, if your that way inclined, you wont see the counter sunk Allen head bolts any way.

    Just a thought

    Bushboy
    "Always do what you are afraid to do"
    "I can accept failure, but I can't accept not trying"

  7. #7
    ***Euro-Nova Supporter*** Peter's Avatar
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    Definitely go for 'bolt in'. Although not an engine cover I do have my Triumph 2000MkII fuel tank there and I can remove the 'false bulkhead' which I uses for speaker and amp mounting and have the tank out in 5 minuets giving access to the transmission, or in your case the service area of the engine. If you make a neat 'plug' followed by a mould and then a final casting you can make it very smooth, I wouldn't worry too much about a smooth finish on the engine side, you could use a stick on heat shield anyway like what one our RV guys has, looks very neat.
    heat sheild.jpg
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  8. #8
    Thanks very much for all the replies, and a very definite conclusion. Bolt in it is!

    I'm still wondering if there's an easy way to make the flange between the bulkhead and inside of the body shell (partially represented by the brown parcel tape in pic 6..!).I'd envisage the one size fits most bulkhead to fit between the chassis rails, floor and around the chassis tunnel, but simply have a flat top section that is trimmed to suit whichever body (Buggy, Nova, Karma, Bonito, Eagle ,356 etc etc) is used. Then the L section flange between it and the inside of the body shell could be made separately; bonded onto the flat bit of the bulkhead panel and bolted to the body.

    Using chopped strand mat would be the obvious approach, but it might look a bit rough and ready. Is anyone aware of a prescribed method for this job, maybe using fibreglass tape or a more evenly textured fibreglass cloth?

    Ed

  9. #9
    Woven tape is a great way to get strength neatly - I made a double-cranked kayak paddle shaft using it and it's nearly as light and rigid as a carbon one. It drapes and conforms very easily, not too expensive either thoiugh nothing is as cheap as CSM...
    It's a 52 year old car and everything works, just not always at the same time.......and it's probably about to get jealous!
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