26 replies to this topic

[AndyR]

I hate to be pedantic, but GRP found in automotive will NEVER shatter - it will always "green-stick".  If it is shattering, it has way way way too much resin.  It will however fail catastrophically, with a sudden crack.  There are circumstances where GRP will shatter, but i see no point in creating such circumstances with glass fabric. 

 

As mentioned, composite materials for race cars - not for the road.  It may seem attractive as it doesnt require welding and specialist skills/tools to get ok results.  But safety wise (both pedestrian and driver/passengers) i would put my faith in metal and maintaining original structure.  And lets be honest, nobody likes pulling fibre glass splinters out their arse after a crash!

 

I have had GRP and CRP on my mini and after a short time and considerable amounts of cash later - i went back to metal - for the point made earlier, its a classic car.  I can totally understand the fascination and some of the amazing projects with loads of carbon, but for specific purposes.  But each to their own.

 

Andy

[Cooperman]

For the GRP enthusiasts on here, let me ask a simple question:

If you were going to fly in a small aircraft and the pilot said,

"We had a bit of a problem with some corrosion in the rear fuselage where the tail-plane attaches. We cut out the aluminium and replaced it with moulded GRP and fitted it on with Dzus fasteners. We didn't do any stress calculations, but we've put a few strengthening bars in and we think it will be OK".

Would you want to fly in it?

[mini93]

Seems difficult for some people on here to comprehend that some people infact like composite panels for their car... if you dont like it, tough tittys!

[Cooperman]

Seems difficult for some people on here to comprehend that some people infact like composite panels for their car... if you dont like it, tough tittys!

If having composite panels with doubtful crash-resistance in an already somewhat vulnerable car is acceptable, then that's a personal issue.

Don't say 'tough titty's', it is the responsibility of some of us on here to point out any safety issues, and fitting parts which may lack structural integrity is a safety issue. If we failed to point out the risks and simply said "fit them" and someone was killed or seriously injured due to the reduction in structural integrity then we would be morally responsible.

Saying 'tough tittys' is, quite simply, a very immature statement to make and we don't want that attitude on here, thank you.

[AndyR]

Depends how many dzus fastners!  But i get your point....

 

No i wouldnt.  To expand, I think the problem stems from the lack of understanding of the fundamentals of composite materials and their limitations.  There are many facets to what make a composite strong and light.  Get it wrong and its weaker than balsa wood.  Everybody thinks Oooo carbon fibre (and for some reason GRP as the cost effective equivalent) as being their stepping stone to a race/F1 car.  Just like metal, the structure is as important as the material.  You cut a hole in something and fill it with something different - you have weakened it.  But yes, lightened it.  Wet layed up composites are never going to attach well to metal.  Even a pre pregged joint will fail eventually - just ask competitive cyclists!  Composites should never be used as replacements for otherwise welded panels.  However, i cant see the problem with a properly manufactured boot lid or bonnet (double skin of course).  But not much else.  Accessories like pods, door cards, covers etc are ok. 

[Ben_O]

My problem with FG flip fronts is that they cannot be structurally attached to the steel body.

 

Most flip fronts are just bolted to the a panels and front of the subframe and in most cases the inner wings get cut out too.

 

so basically, beneath the FG front is a couple of lengths of box section or tube to support the front of the subframe.

 

Forget it's crash resistance because in an impact, it will most likely just detach itself from the car.

 

I just added my opinion for the same reason as cooperman, if someone is weighing up the pro's and cons of fitting a composite front end then it is important to point out the cons, especially if they relate to the safety of the structure.

 

Ben

[mini93]

 

Seems difficult for some people on here to comprehend that some people infact like composite panels for their car... if you dont like it, tough tittys!

If having composite panels with doubtful crash-resistance in an already somewhat vulnerable car is acceptable, then that's a personal issue.

Don't say 'tough titty's', it is the responsibility of some of us on here to point out any safety issues, and fitting parts which may lack structural integrity is a safety issue. If we failed to point out the risks and simply said "fit them" and someone was killed or seriously injured due to the reduction in structural integrity then we would be morally responsible.

Saying 'tough tittys' is, quite simply, a very immature statement to make and we don't want that attitude on here, thank you.

 

 

There's pointing out the safety aspects of it... then there's saying things like the above with the plane hypotheticals which isnt the same thing,

Thats like saying "anything fiberglass is going to make you crash and die and your car will career off the road into a school" so perhaps be a little more constructive with your replies, like I have seen before you can infact be.

The guy mentions the front end, but asks about panels in general... Fiberglass bonnets arent going to be against the construction rules Bungle mentioned, nor is it going to be as detrimental as fitting a full front. There's the pedestrian side of things but really, composites tend to flex more so could infact be better in this situation as long as you dont end up deflecting the bonnet so far as to start impacting the engine components, rocker cover etc. but with a car not designed for pedestrian protection your alwasy going to come off just a little bit worse for wear

I'd have no problems fitting either a fg bonnet or bootlid to a road mini (apart from security when it comes to the boot)

 

 

Thanks.

 

Mr Immature

[GTIAlex06]

I don't agree with the argument about devaluing the car or ruining a true classic etc as my mini is my mini.

My mini is mine, and I can honestly say it will never be anyones other than mine so the value is not important to me as it has more sentimental value than anything.

 

As regards to strength, the mini is not a strong car you want to be having a crash in, whether it be metal or fibreglass.

 

The most important aspect is how sound the mini is in the first place, it rather have a bump in a fresh prepared fibreglass front end mini than a rusty scabby metal front end mini.

 

If i had the choice of both, Id probably go for metal front for piece of mind in terms of safety however,

 

 

Im considering the fibreglass front route, I like the weight saving and the fact it will be removable, although mine will have a full FIA cage anyway and wont be a daily drive. It will be a sunday car I use for sunday drives and the occasional hillclimb type event, not a show car so the final finish wont bother me too much as I wont be polishing the underside of the car every Sunday trying to win a show and shine

Edited by GTIAlex06, 30 July 2014 - 09:37 PM.

[Cooperman]

I fly 100% Glass Reinforced Plastics sailplanes and I have no issues with this. In fact, during my working career I worked with two major moulding companies as a consultant and we did such composite vehicles as the Lucas Electric Taxi, the DB7 body panels, some of the De Lorian structure, a lot of aerospace stuff, so no, I'm not anti-composites. In fact, the company which I owned did the chassis & sub-frame detailed design for the famous Ford RS200 Group B rally car.

However, with a steel monocoque you cannot safely use composite structure in place of the steel monocoque. Nothing will change this.

Ignore this if you will, it's not my life which is at risk but, like it or not, that is the engineering truth.

Bonnets, boot lids & doors are not part of the primary monocoque structure by the way.

Edited by Cooperman, 30 July 2014 - 09:46 PM.

[samsfern]

Both the minis I've had always had proper steel front ends, I never liked the idea of a fibreglass front. I did however have really flimsy single skin fibreglass bonnets on both of them.

[Carlos W]

The OPs original question was asking about opinions of FG front ends, so far a qualified panel beater, an MOT tester and a member with 60 years rallying experience as well as a lot of engineering experience has commented. 

 

That's a fairly good response in my eyes.

 

Comparing a rusty metal front end to a fibreglass one is not a realistic comparison, no-one is going to replace a rusty front end with another rusty front end.

 

Whatever anyone decides to do to their car, it is your responsibility to ensure you have obeyed the law and notified your insurance company of any modifications. If you crash a car and hurt someone and your car isn't legal and the insurance company are not aware of the modifications you will serve time in prison.

[samsfern]

As an mot tester, there's not much I can think of for it to fail on really. Thinking off the top of my head, the only possible failures which would arise from it would be, insecure wiring, subframe inadequately mounted and probably subframe or suspension component mounting inappropriately modified, depending how things had been done, and provided the car had the side indicators fitted if it should do for the cars age. I also suppose it would be highly possible to find fractures/cracks around where the brace bars were mounted, if not done properly.