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Thread: RRC fibreglass bonnet

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    RRC fibreglass bonnet

    Does anyone make a fibreglass bonnet for a classic.
    Other than working on my one rep max for overhead press, is there any reason why the bonnet has to be so heavy

    Phil

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    A fibreglass one may be heavier.

    LR originally tried making them out of aluminium but the draw in the dies was too deep and the aluminium sheet cracked.
    Ron B.
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    Quote Originally Posted by p38arover View Post
    A fibreglass one may be heavier.

    LR originally tried making them out of aluminium but the draw in the dies was too deep and the aluminium sheet cracked.
    The steel ones crack in the front corners for the same reason.

    Adjacent to the original 'mirror mount' positions where the sides meet the horizontal flange underneath.

    DL

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    I'm guessing short of having a good straight clean bonnet to use as a plug to start with (the most expensive part) - the mold would also consume a significant space. For this reason I never went ahead with making one. In hindsight of course, I wish I had both the space and a good plug. I *had* a good bonnet, but didn't have space. I had space for smaller parts some time ago, but no longer.
    Currently have neither as we are in the middle of relocating.

    Fwiw, fibreglass would not be ideal, and there are a couple of reasons. One is weight, the second is the commonly available resins' suitability.

    To achieve the desired strength, prevent sag and maintain a performance structure that will incorporate the crash protection structural component, the finished article in glassfibre would also carry more bulk than the sheetmetal bonnet.

    Ideally, the most strength would come from a composite carbon-aramid lay up, which would need to be vac bagged and autoclaved. The reason for this is the resin used in this kind of application requires an elevated temperature cure process that is tightly controlled. The resin used has to withstand the target environment operational temperatures - and a basic epoxy or vinylester would not be sufficient in thermal stability for this application.

    Lastly, you *could* in theory apply a thermal barrier to the underside- and a heat rejection foam/reflective material would possibly achieve this, but that in turn reduces clearance, adds mass and does little to assist with underbonnet temperatures - in fact likely would increase by a significant amount - which may in turn accelerate the perishability of hoses, wiring insulation and the like. It's a common issue in current model vehicles from all manufacturers and certainly was an issue with european manufacturing from the early 90's through to the late 2000's - ruining many a vehicle through engine bay thermal cycling and heat retention.

    Great idea in theory - and completely doable. Careful material choices may get you there with the evolving technology in resins, but none of it is cheap, and carbon-aramid can be wet laid up... but you'd still need absorbtion mat, peel ply and vac bagging to get the correct material density and structural strength.

    It always sounds easier than it is to actually do.

    Then there is the cost.

    You could buy a new part and have it painted up for less than ther cost of the above exercise.

    You'd need to become a small manufacturing enterprise to make it cost efficient. by my estimate you'd need to manufacture about 20 units at the current price of a new pattern part bonnet before you broke even on the costs on the plug, mold and materials used to make the bonnet.


    lastly - there are these guys...
    Search: 1 result found for "range rover"
    – The Fibreglass Factory


    1050inc.
    plus shipping.

    for that $ I'd still go with a used metal one, even if I had to refinish it.
    Roads?.. Where we're going, we don't need roads...

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    Hi Mercguy
    Yes I have seen the bonnet listed in the link you provided, and agree, it’s nearly the same price as a new metal one.
    I was considering woven rovings and epoxy resin as I have had good success with them in the past.
    The boot lid below was from a mould I made off a standard boot lid and then cut down to suit the Bini tail lights. While the boot lid was still in the mould I then “glassed in” stiffeners in nominally the same location and style as the original so it kept its shape.
    B7973329-92BF-41D2-81E2-F6973D070D97.jpg

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    Quote Originally Posted by Phil 850 View Post
    Hi Mercguy
    Yes I have seen the bonnet listed in the link you provided, and agree, it’s nearly the same price as a new metal one.
    I was considering woven rovings and epoxy resin as I have had good success with them in the past.
    The boot lid below was from a mould I made off a standard boot lid and then cut down to suit the Bini tail lights. While the boot lid was still in the mould I then “glassed in” stiffeners in nominally the same location and style as the original so it kept its shape.
    B7973329-92BF-41D2-81E2-F6973D070D97.jpg
    Fibreglass doors, roof, guards, no issue.

    IME a fibreglass bonnet would be a waste of time because:

    It would be around the same weight as the original steel version. (there are threads of successful air strut fitting to overcome the steel weight issue)

    Heat does strange things to the glass reinforcement (woven cloth or chopped strand) where it will expand slightly and you can see the texture through the gel coat.

    I can remember being shown a glass body Ferrari (could have been carbon fibre) a long time ago and the texture was very visible. Ferrari were successful spraying the paint on the mould, then glassing over it back then. Saved a heap of time prepping for paint.

    I've been glassing for 50 years............. mostly surfboards, which are a very high standard.

    DL

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