horizenjob wrote:
I do mind you saying. You appear to enjoy these straw man arguments about people you've never met or spoken with.
Sorry, it's just an observation based on the posts on this forum: I see a level of over-analysis that seems strange, coming from a country where we've been building lightweight sportscars for many decades, without benefit of the facilities and computer analysis that some posters on this thread are trying to tell me are 'essential'.
Until about 5 years ago, FEA was so expensive and experimental in its results that it was only used at the very highest level. The majority of UK kit and self-built cars are still designed without it, and torsional testing is uncommon, yet the end results lead the US by miles in this sector of the industry.
your resident 'expert' wrote:
First here is what you will need to have....
1) LOTS of money
2) A lot of experience with molds
3) LOTS of money
4) Extensive experience with carbon fiber layup and resin flow
5) one hell of a build shop
6) a hand full of experts to double check what you did
7) expensive software
... yet we designed and built the world's first carbon monocoque race cars in the UK, with access to nothing more sophisticated than a pocket calculator and the most basic composites facilities, and they performed (and a quarter of a century later
continue to perform) just fine. The people who did it became 'experts' only because they were the only ones who had tried it.
Maybe the lesson is that you learn more by actually doing it than by endless speculation on why it might not work?
horizenjob wrote:
If you need a part to be strong and light IN A SINGLE DIRECTION then use unidirectional style "cloths".
Edited for accuracy.
What I seem to be struggling to get across, despite repeating it several times, is that the stresses in a monocoque tub are distributed through it in a way that it needs
multi directional strength,
except where there are localised point loads. Adequate beam strength is pretty much a given, for any chassis structure that delivers sufficient torsional stiffness, so is not a primary consideration.
Add to that the fact that the robustness of the skin to impact damage becomes the limiting factor if you try to use the material to its highest level of efficiency, and layers of simple, bidirectional cloth become a perfectly acceptable - in fact optimal - solution.
The simple, flat sandwich panels I'm using personally have skins of 0.03" thickness and are about as thin as you'll want to go for a road car. They are capable of turning out a chassis several times stiffer than a typical spaceframe, for about half the weight (albeit at about 2-3 times the cost, when you include for labour). They perform perfectly adequately in a crash, as the honeycomb core stabilizes the carbon and makes it disintegrate in a progressive fashion, absorbing
massive amounts of energy in the process; some companies actually manufacture crash boxes out of the stuff for this very reason. Quality control is not an issue, as it's not especially difficult to ensure consistency in a thin, flat panel of uniform thickness, but in any event the manufacturers I'm using work to aerospace levels of quality control.
Certainly, if you are building F1 cars and have an unlimited budget, carefully optimized design with extensive (though far from universal) use of directional fibres will pay dividends, but by then you're so far into the realm of diminishing returns (unless you have the massive financial incentives that go along with the F1 circus) that you can't see the real world even on the clearest of days.
It's been proven many times, on this side of the Atlantic, that you can achieve a substantially better stiffness:weight ratio than a steel spaceframe, even with very crude wet lay-up monolithic glass fibre monocoques.
Even fairly basic carbon fibre construction, built to the practical limits of everyday robustness, is capable of delivering such massively stiffer structures that spending time, money and effort further improving them by extensive use of unidirectional reinforcement has very limited additional value at our level...
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