Flying Roof Panels
Discussion
quote:
i've never noticed it when i was at 150mph... on a track that is... can't think when else I'd do anything near 120mph so this isn't a problem for me... maybe i'm just a big girl's blouse... or like my license to stay completely clean?
Both
You've never driven in France then? Those autoroutes are soo tempting.
OK call me thick here.. but how can one not fix the roof in properly.. the slot in the roof goes round that little peg thingy at the front and the back comes up to put it all together... how is it possible to get the back struts up withought the roof being in place "correctly" ??
Anyone?
Matt.
Anyone?
Matt.
quote:
You are a braver man than me Leadfoot, 120 plus I'm usually like this not enough time for me to go looking around the cabin for gaps!
I've used the Griff on the continent a fair bit, you become acclimatised to higher speeds (& 120's not really shifting is it now?).
Didn't need to look for the gap either - the howling gale
next to me lug'ole gave it away. quote:
OK call me thick here.. but how can one not fix the roof in properly.. the slot in the roof goes round that little peg thingy at the front and the back comes up to put it all together... how is it possible to get the back struts up withought the roof being in place "correctly" ??
Anyone?
Matt.
Matt - you need to drive it a bit more quickly. Do a quick blast to say 140 (should only take a few seconds)
and then report back. If your door top seals stay intact and don't howl a gale then I'm coming round one night to nick your doors and roof 
You do need to make sure the front edge is nicely seated before clicking the rear into place, but you're right, this is not rocket science. I completely believe that the roof can pop out at a decent speed, maybe the rear stays are looser on some cars. Typical TVR response.
T/.
quote:
quote:
OK call me thick here.. but how can one not fix the roof in properly.. the slot in the roof goes round that little peg thingy at the front and the back comes up to put it all together... how is it possible to get the back struts up withought the roof being in place "correctly" ??
Anyone?
Matt.
Matt - you need to drive it a bit more quickly. Do a quick blast to say 140 (should only take a few seconds)
You do need to make sure the front edge is nicely seated before clicking the rear into place, but you're right, this is not rocket science. I completely believe that the roof can pop out at a decent speed, maybe the rear stays are looser on some cars. Typical TVR response.
T/.
Hmm... yes there was quite a gale at 130.. and the buffeting of the doortops convinced me to slow down.. I'll give 140 a go at Anglesey if the track allows
Cheers,
Matt.
Must agree with Matt and say I'm perplexed about this 'miss-alignment' hypothesis. It's obvious when you apply pressure to straighten the supporting strut whether the panel's properly seated along the front edge, or not. On a couple of occasions it wasn't, as was clear from the additional force that would have been required to straighten the strut. So ease off the other strut and reseat the front edge.
Assuming a chim of normal rigidity to maintain the spatial relationship between the top of the screen and the leading edge of the rear panel, what force would be necessary to break that relationship and release the roof panel? Could that force be provided by the difference in pressure between the inside of the car and a space immediately above the roof [i.e. lift] or from a sudden rise in the cabin pressure caused by some structural airflow-induced deformation in the bodywork leading to a sudden pressure surge inside the car?
Anyone got access to one of the F1 wind tunnels?
Hutch
Assuming a chim of normal rigidity to maintain the spatial relationship between the top of the screen and the leading edge of the rear panel, what force would be necessary to break that relationship and release the roof panel? Could that force be provided by the difference in pressure between the inside of the car and a space immediately above the roof [i.e. lift] or from a sudden rise in the cabin pressure caused by some structural airflow-induced deformation in the bodywork leading to a sudden pressure surge inside the car?
Anyone got access to one of the F1 wind tunnels?
Hutch
quote:
i've always been intrigued by this two piece chimaera roof... http://ourworld.compuserve.com/homepages/shpub/wcat18.html
Only £400 (prolly gone up) which I think is pretty good... except only comes in black or blue... which might explain why TVR needs to make one individually to match the roof colour!
Wedge Automotive no longer produce the two piece roof but will do again (so they have just told me) in a few months. They have changed their name (cannot remember to what) but can still be reached on the number given on the website.
By the way, I too would have thought it impossible that someone would not know/realise/have a reasonable suspicion that the roof panel was not properly on. Before last Thursday that is! I just hope that someone does not get hurt through this and that a driver (or TVR) do not find themselves slapped with a negligence claim or worse...
quote:
Must agree with Matt and say I'm perplexed about this 'miss-alignment' hypothesis. It's obvious when you apply pressure to straighten the supporting strut whether the panel's properly seated along the front edge, or not. On a couple of occasions it wasn't, as was clear from the additional force that would have been required to straighten the strut. So ease off the other strut and reseat the front edge.
Assuming a chim of normal rigidity to maintain the spatial relationship between the top of the screen and the leading edge of the rear panel, what force would be necessary to break that relationship and release the roof panel? Could that force be provided by the difference in pressure between the inside of the car and a space immediately above the roof [i.e. lift] or from a sudden rise in the cabin pressure caused by some structural airflow-induced deformation in the bodywork leading to a sudden pressure surge inside the car?
Anyone got access to one of the F1 wind tunnels?
Hutch
Actaully thats a good point... the roof is most probably sucked off the car by the air over the top of the roof moving so much faster than the air underneath, along the lines of the aeroplane wing effect..
Anyone a tecchie on this here ??
Matt
Edited to say:
..plus considering how flexible the roof actually is as a whole I reckon a constant upward "pulling" force in the center of the roof could shorten its overall length front to back by 1/2 an inch or so...?
>> Edited by M@H on Monday 7th October 16:49
Having just come back from my private airstrip (hoccifer) I can say I did notice a half cm gap appear between the top of the window and the roof at around 140ish in my 4.5, my first thought was ooops, I havent shut the door properly, but upon inspection it was fine, so, I dutifully carried on following my m8 in his m5 (for reference, m5 and 4.5 chim are neck a neck to 130 then the m5 leads)
Does worry me a little about the roof, but not overly, as it DOES seem to be solid in place...
Does worry me a little about the roof, but not overly, as it DOES seem to be solid in place...
After recently having a new windscreen fitted, I noticed the gaps were wider on the roof than before.
It hasn't caused any problems yet(leaks or flying off) but I suspect that an ill fitted screen could cause the roof section to fly off, maybe have a look at that before putting another new roof on.
heliox
My roof is as tight as a badger's arse and I can't imagine it coming off at whatever speed. However, we all know every TVR is different, so for those with roof-lifting worries, could you not fit a couple of s/s roof catches from Leven that are designed to hold the S roof in place at the front?
quote:
My roof is as tight as a badger's arse and I can't imagine it coming off at whatever speed. However, we all know every TVR is different, so for those with roof-lifting worries, could you not fit a couple of s/s roof catches from Leven that are designed to hold the S roof in place at the front?
Hmmm. Could we do this? I must say that "once bitten" etc. I am now very nervous at driving [at speed] with the roof up. This may be a way of settling my nerves...
quote:
... the roof is most probably sucked off the car by the air over the top of the roof moving so much faster than the air underneath, along the lines of the aeroplane wing effect..
Anyone a tecchie on this here ??
That is the basis of an aeroplane wing, the air travelling over the top is moging faster and so reduces pressure thus causing lift (it is all the fault of Physics)
In the case of the plane wing, the top surface has more of a curve than the lower surface thus increasing the distance and so increasing the speed.
In the case of the car roof, the air travelling over the roof at xxxmph is a lot faster than the air inside the car travelling at 0mph (unless the fan is on, then say 2mph
) and so you get lift Just look at any of the soft top convertables as they drive along, the roof is pulled up.
I used to have a very early Suzuki Jeep with a canvas roof, the front would be pulled up by the lift but the very back of the canvas rof was pushed down, I guess by the turbulance
MB.
A postscrpt to this topic:
I have just taken delivery of a (second hand) roof panel sourced by David Batty (thanks, David).
Now TVR told me that a new panel would need to be shaped and fitted by a dealer, covered and rubbered (all in all a days labour) which would have meant the thick end of a grand. Ouch.
Yet the panel I now have fits better than the original and needs no shaping!!!
What I have now noticed is that the original simply never fit properly - the lip never fully fit into the windscreen groove. I had no reason to suspect anything was wrong until I took a closer look at other Chimaeras/Griffs and saw how snug the panel should actually be!
So check yer panels, lest you lose 'em!
I have just taken delivery of a (second hand) roof panel sourced by David Batty (thanks, David).
Now TVR told me that a new panel would need to be shaped and fitted by a dealer, covered and rubbered (all in all a days labour) which would have meant the thick end of a grand. Ouch.
Yet the panel I now have fits better than the original and needs no shaping!!!
What I have now noticed is that the original simply never fit properly - the lip never fully fit into the windscreen groove. I had no reason to suspect anything was wrong until I took a closer look at other Chimaeras/Griffs and saw how snug the panel should actually be!
So check yer panels, lest you lose 'em!
Just a thought, when you follow some soft top cars that are travelling fast you can see the top of the roof almost inflating. As far as I know this is caused but the ventilation air coming in faster than the exit vents can let it out. Anyone tried dropping both windows a tad as the roof starts flapping at 150mph whilst lighting a fag and ringing someone on the mobile? 
If it is the same problem as above it may stop it from happening, I am too attached to my license to try it myself?
Ivan
If it is the same problem as above it may stop it from happening, I am too attached to my license to try it myself?
Ivan
The same on my Griff, which was why I did not understand this thread. The roof fits into the window well enough, that this alone will hold it up. Then when it is all assembled, there are no gaps along the roof edges.
David
David
zumbruk said: The roof on my Chim (98 450) fits into the top of the windscreen so snugly that you can let go of it while you put the rear section up. I cannot imagine it coming out... But then, I've not gone over 120 yet.
Just had to add my 2c worth. (wedge related, but on-topic!)
The issue boils down to how well the roof fits.... but you have to know how good is good!
by way of explanation, I've had a 'roof loss' twice - once on the day of purchase (which I put down to not having fitted the roof properly - as I assumed I _must_ have mis-fitted it).
It happened again on track day recently - was doing poss 90/95.... and on chatting to the marshals, and looking at some other wedges, discovered that my roof 'fit' was significantly worse than others.
turns out the "1-2mm" movement was enough, combined with windscreen flex and the not-insignificant Venturi effect of 95mph wind, to lift the roof off.
(the Venturi effect is the main culprit - remember it is the same thing that keeps 747's in the air, and they 'only' travel 4 times faster - they weigh a LOT more!)
I'm now looking for a new roof panel - anyone recommend a supplier/salvage (have identified Douglas Valley - but somewhere in the South would be nice!)
The fabric is torn, the corners are crunched, and the panel is squidgy, suggesting terminal internal fibreglass problems.
cheers
The issue boils down to how well the roof fits.... but you have to know how good is good!
by way of explanation, I've had a 'roof loss' twice - once on the day of purchase (which I put down to not having fitted the roof properly - as I assumed I _must_ have mis-fitted it).
It happened again on track day recently - was doing poss 90/95.... and on chatting to the marshals, and looking at some other wedges, discovered that my roof 'fit' was significantly worse than others.
turns out the "1-2mm" movement was enough, combined with windscreen flex and the not-insignificant Venturi effect of 95mph wind, to lift the roof off.
(the Venturi effect is the main culprit - remember it is the same thing that keeps 747's in the air, and they 'only' travel 4 times faster - they weigh a LOT more!)
I'm now looking for a new roof panel - anyone recommend a supplier/salvage (have identified Douglas Valley - but somewhere in the South would be nice!)
The fabric is torn, the corners are crunched, and the panel is squidgy, suggesting terminal internal fibreglass problems.
cheers
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