Was there any real data that showed glass spoiler was useful

[alex_gray255]

Does anyone know if there was any real data that showed if the glass spoiler on the back of the Sagaris had any aerodynamic purpose other than acting as a brick wall?

I know spoilers are supposed to give down force at speed to keep the car grippy to the road, but from my ok meager knowledge of aerodynamic design, the spoiler on the Sag is more like a brick wall than anything useful.

Please correct me if I'm wrong, because the people I've spoken about it so far think the current spoiler design is a bit... extreme as well.

Now the automatic bonnet vents are done, been thinking about doing something similar to the glass spoiler. Somehow having it assume a more aerodynamic shape at speed, or just have a spoiler that is made of two lengths of glass rather than one big one and fold over each other at speed or some other insane idea like that.

So, is the current spoiler really useful or just a decorative item?

Thoughts welcome. (other than comments like - you're mad and leave the car alone etc. of course )

[TVR_owner]

Alex,
The factory tested the flap on the T350. That it found it's way on to the Sag suggests it had some function. How functional under normal use it is?

Maybe John Ravenscroft would be able to feed back what the findings on the T350 were?

[clive f]

I met John Statton at Carfest south last year, he told me that the spoiler was put on the back to counteract the effect of the air going over the top of the roof that was being upset by the hump on the drivers side of the roof, without it the car felt unsettled at high speed.

the way he spoke of the subject I assume this was actually tested by the factory in a wind tunnel.

[WolfyJones]

I have tested with high speed runs with and without rear aero, over 120mph car feels a lot more stable/planted with rear aero.

[spitfire4v8]

Some people have reported significant loss of Vmax with the spoiler but I don't know if the reports are reliable or just chest-puffing for who can run fastest sans-spoiler. It's essentially a big gurney sticking up, most of which is probably in the stagnant boundary layer or at least in turbulent air and not doing a great deal anyway. You could always test the car at bruntingthorpe when it's fully run in and do some back to back tests, you could ever try and data log any suspension movements if you wanted to see if there's any discernible forward pitch of the body without the spoiler rather than just seat of the pants feedback.

[alex_gray255]

Thanks for that, folks. Looks like it is try it and see I guess. The anecdotal evidence however seems to be that it serves a purpose, so guess I'll have to go with that for now unless something clearer comes to light or test it myself.

[V8 GRF]

spitfire4v8 said:

It's essentially a big gurney sticking up, most of which is probably in the stagnant boundary layer or at least in turbulent air and not doing a great deal anyway.

I can assure you it does serve a genuine purpose.

Chris Runciman who was the lead engineer on the T400/T440 project was present at the tests of the T350 in the tunnel at MIRA and the addition of the flap removed (iirc) over 30lbs of lift.

[spitfire4v8]

30lbs isnt massive But any loss of lift is welcome.

[alex_gray255]

Thanks, Dave. Ok, I can close that project then as not worth doing.

Back to active exhausts.

[ShiDevil]

Happy Days

[RedSpike66]

I've always thought the VW Corrado automatic spoiler would have been a great addition to the Sag.... just a shame Porsche, Audi, McLaren, Bugatti have made it soooooo common tho

By the way, every car lifts at speed - the basic shape is similar to a wing - the air going over the top has to accelerate to keep in sync with the air flowing underneath, greating low pressure over the top of the car. Obviously, some are worse than others, so the Sag spoiler must make some difference, but it certainly doesn't look like it had hours of engineering thought applied to it's design !!

Edited by RedSpike66 on Thursday 27th June 22:10

[Druid]

RedSpike66 said:

the basic shape is similar to a wing - the air going over the top has to accelerate to keep in sync with the air flowing underneath

That would be the "Equal Transit-Time Fallacy". Although still my preferred explanation!

[alex_gray255]

My problem is I think the Sag spoiler is OTT for the job it needs to do. But I don't have the time nor the bother to pour 1000s into trying out different models to see what was best.

I did have some ideas I was willing to look into if the existing one was pointless, but as it does have some "validation" - I'm not going to get someone to redesign it with something that might only be as good or worse. There is no point

It really depends on if the current one provides too much down force or just enough and without the original data or access to someone who worked on it and thus could comment more, it is not a project I want to look at.

[WolfyJones]

Hi Alex

I remember reading a thread (can't find it now) where you were looking at a sort of pdk/flappy paddle system for a Sag,

Did you get anywhere with that project?

[hman]

Druid said:

RedSpike66 said:

the basic shape is similar to a wing - the air going over the top has to accelerate to keep in sync with the air flowing underneath

That would be the "Equal Transit-Time Fallacy". Although still my preferred explanation!

But would it work on a conveyor belt though ?

[alex_gray255]

WolfyJones said:

Hi Alex

I remember reading a thread (can't find it now) where you were looking at a sort of pdk/flappy paddle system for a Sag,

Did you get anywhere with that project?

I looked at it all, got the costings and decided not to bother at the time. I just got a custom rebuild of the T5 box done instead
that made the gear changes a hell of a lot smoother and a CR box.

I might revisit however as when I compare by Evora IPS system to the Sag manual system... You just lose so much power on the changes. Never tested, but I bet my Evora could thrash the Sag over a short distance just because of the gear changes.

So, yes, it was doable - I found some systems that would work. I went for a sequential gearbox and a flappy paddle system. The systems would have needed some modifications, but was doable (in theory). Of course, the proof is in the final product and I never got that far. If I was doing it now, I might rethink some of how I was originally going to do it as my ideas have changed somewhat.

[WolfyJones]

alex_gray255 said:

I looked at it all, got the costings and decided not to bother at the time. I just got a custom rebuild of the T5 box done instead
that made the gear changes a hell of a lot smoother and a CR box.

I might revisit however as when I compare by Evora IPS system to the Sag manual system... You just lose so much power on the changes. Never tested, but I bet my Evora could thrash the Sag over a short distance just because of the gear changes.

So, yes, it was doable - I found some systems that would work. I went for a sequential gearbox and a flappy paddle system. The systems would have needed some modifications, but was doable (in theory). Of course, the proof is in the final product and I never got that far. If I was doing it now, I might rethink some of how I was originally going to do it as my ideas have changed somewhat.

Yes I think it would suit the speed six engine nicely, did you price up a finished system?

[alex_gray255]

WolfyJones said:

Yes I think it would suit the speed six engine nicely, did you price up a finished system?

Yes, but I would need to see if I can find the details. Probably buried in a project folder somewhere in the spare room.

From memory, I think it was at least 9-10k for the hardware and then get a quote from specialists to do the work.

I didn't get any firm quotes to do the fitting, but it would probably be a few more grand as well on top of it. Then throw in another couple of thousand for things you didn't know about before you started the work and take it from there.

Oh, you would also need to trim it into the existing interior "nicely", i.e. removing existing gear level and replace it with something else - probably a knob (like the Jag) or buttons like the Aston... Another couple of grand to trim and modify the gearbox, plus the paddles so they look appropriate to the Sag/T350 or whatever.

So, yeah, not cheap.

Not looked into fitting cheaper gearbox units as I was looking at the high performance ones like Quaife.

Sure someone could do a more cheap and cheerful option if you looked into it more.

[WolfyJones]

Looks about right, I was thinking about £15k for a decent system

[alex_gray255]

Cheaper option might be to look at converting the clutch to a hydraulic system using the paddleshift to change the gears. That way you keep the existing gear box.

But personally, I hate the T5 gearbox. It is a load of agricultural c***p. I can live with the hybrid/customised version I have now as that is "useable", but...