Front Spoilers for P6?

jp928

Active Member
#46
Got the LH side fitted. Found some anti-slip rubber mats the missus had, made gaskets out of that. Bit hard to glue on because its a bit floppy, and spoiler edges are thin, but should be OK. One bolt would not engage with captive with the big washer, due to small fold near edge of panel, so I had to leave the washer out. Muffed one of the holes for the RH side, so a bit of rattail file work needed. Also on RHS the lower edge of the valance seems to be curved upwards and I had to squeeze it to the spoiler to get the bolt started. Will see how it looks leaving the spoilers black before worrying about painting them body coloured - no sign of Mexico Brown spray paint out here, not sure if such cans can be posted?
The gasket is hard to cut cleanly, so its coming off again, and I will sand the edges to get it clean. I find with this stuff, and fibre glass things, that wet-n-dry paper gives a good result if knives or scissors dont achieve a clean edge.

PS. The RHS valance lower edge is subtly different from the LHS, and I am going to need some slightly longer bolts, and maybe a thicker gasket there - visible gap with the two outer bolts done up as tight as I dare, considering the captive nut mountings. Will see if I can find some beading to fill the gap and look better, as some others have done.
 
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#47
I have a fibreglass V8 front valance which is probably going to be used on Bruiser Mk2 and which we'll probably be modifying, part of which will likely be the attachment of something similar to these spoilers.
 
#48
If it’s a case of getting aero advantage from the spoilers and not originality you can make them out of sheet alloy. I was thinking of scanning a 3500 front end and modeling some myself as I can make them at a pretty reasonable price I reckon. Would that interest anyone?
I'd bite, but getting them to me will be the big issue.
Post is a non starter and couriers will break the bank.
 
#50
I think I bought the last of Scott's front spoilers, it is modelled like the Torana A9X front with two big brake ducts in the front. They look very cool but I haven't put it on as its one piece and goes right across all three panels and I haven't finished playing with the front yet.
Man I'd love to get my hands on one of those spoilers but I'm way too late! I knew I recognised the air-ducts but couldn't place it - thanks for the info :)
 
#51
They were made by Purvis Plastics who made the Eureka kit car. I rang the Eureka car club a few years ago and they said they bought up the molds and parts for the car but to their knowledge the rest was junked. however the reason the spoiler looks like a Torana one is because purvis also did the plastic bits for the racing cars (A9X/ SLR etc.). It just occurred to me that; given its similarity, the mold may be with stuff collected by the Torana / Holden clubs if they also collected their stuff.....

There is actually two reasons its not on my car yet. the second being I would like to get a mold made in case a kangaroo wants to take a close look at speed. I'm happy to supply it if you can find a suitable mold maker? I'm mid north coast NSW so not that far from SEQ
Mike
 
#53
So these front spoilers obviously work as has been confirmed by the many people who have them but as an aerospace engineer, I wonder exactly what they do? Clive's awesome car has bumper, overrider and foglight right in the airflow to the spoiler itself so direct airflow would be extremely turbulent. These items in the airfow would upset it enough for the to just dissipate randomly I expect so not causing any specific impact. I expect however that at speed the air flows downwards from above and behind the bumper and is also pushed outwards by the bulge in the front valence. This airflow must cause a pressure on the valence and result in an upwards force at speed which makes the car wander. The spoilers break up that airflow resulting in the weight of the front of the car firmly planting itself on the tarmac at any speed.... Just a thought!!!
 
#54
So these front spoilers obviously work as has been confirmed by the many people who have them but as an aerospace engineer, I wonder exactly what they do? Clive's awesome car has bumper, overrider and foglight right in the airflow to the spoiler itself so direct airflow would be extremely turbulent. These items in the airfow would upset it enough for the to just dissipate randomly I expect so not causing any specific impact. I expect however that at speed the air flows downwards from above and behind the bumper and is also pushed outwards by the bulge in the front valence. This airflow must cause a pressure on the valence and result in an upwards force at speed which makes the car wander. The spoilers break up that airflow resulting in the weight of the front of the car firmly planting itself on the tarmac at any speed.... Just a thought!!!
I think they don't greatly enhance the aero in terms of overall drag. I think what they do is prevent pressure building around the valence and front wheelarch causing lift at high speeds. Lots of BL cars of the era got something similar like the Dolly sprint. Even late Allegros. Basically welcome to the motorway age for old designs in the late 70s.
 
#55
So these front spoilers obviously work as has been confirmed by the many people who have them but as an aerospace engineer, I wonder exactly what they do? Clive's awesome car has bumper, overrider and foglight right in the airflow to the spoiler itself so direct airflow would be extremely turbulent. These items in the airfow would upset it enough for the to just dissipate randomly I expect so not causing any specific impact. I expect however that at speed the air flows downwards from above and behind the bumper and is also pushed outwards by the bulge in the front valence. This airflow must cause a pressure on the valence and result in an upwards force at speed which makes the car wander. The spoilers break up that airflow resulting in the weight of the front of the car firmly planting itself on the tarmac at any speed.... Just a thought!!!
I would agree with that, I think the spoilers push the air out sideways, instead of letting it continue under the valance.
One way to test the theory is a roll of tape and ball of wool. Stick a load of tell tale strips of wool all over the front valance, even better would be to only have one spoiler fitted, do both sides and then drive a decent distance behind a camera car and film what happens.
 
#57
Well there is only so much theorising you can do, sometimes you just got to go and try something and see what is going on.

Off on a tangent, I worked for a company building replicas of the Jaguar SS100, these were fitted with an XK 4.2 lump. The cars had twin SU carbs with individual mesh filters, they would not rev beyond 3500 rpm.
This was driving everyone nuts, we could not crack the problem. I removed the filters and still no good. I was convinced it was a carb issue, so I got the bonnet removed and laid on the front wing and running board so I could watch the carb air slides and someone belted the thing up the road, sure enough the air slides were not going past half way.
After mulling this over a thought occurred to me that the air was rushing past the carbs so hard that maybe they could not pull any air in, I made some crescent shaped covers to fit on the leading edge of the filters to create a negative pressure area in front of the carb venturi, the car went up the road and revved to nearly 6k. This taught me to never be afraid to try anything no matter how daft it seemed.

We have better tech nowadays, you can put a go pro under a bonnet or wing and record all you need.
Short of hiring a wind tunnel I cannot think of another way to find out the airflow over the front end.
I have no complaints regarding my rather over size spoilers, the car is rock steady at 100 mph plus, but I have not taken the car to that speed without them, so who knows, they may be just good rabbit catchers. I guess I need to find a ball of wool !
 

sdibbers

Well-Known Member
#58
Well there is only so much theorising you can do, sometimes you just got to go and try something and see what is going on.

Off on a tangent, I worked for a company building replicas of the Jaguar SS100, these were fitted with an XK 4.2 lump. The cars had twin SU carbs with individual mesh filters, they would not rev beyond 3500 rpm.
This was driving everyone nuts, we could not crack the problem. I removed the filters and still no good. I was convinced it was a carb issue, so I got the bonnet removed and laid on the front wing and running board so I could watch the carb air slides and someone belted the thing up the road, sure enough the air slides were not going past half way.
After mulling this over a thought occurred to me that the air was rushing past the carbs so hard that maybe they could not pull any air in, I made some crescent shaped covers to fit on the leading edge of the filters to create a negative pressure area in front of the carb venturi, the car went up the road and revved to nearly 6k. This taught me to never be afraid to try anything no matter how daft it seemed.

We have better tech nowadays, you can put a go pro under a bonnet or wing and record all you need.
Short of hiring a wind tunnel I cannot think of another way to find out the airflow over the front end.
I have no complaints regarding my rather over size spoilers, the car is rock steady at 100 mph plus, but I have not taken the car to that speed without them, so who knows, they may be just good rabbit catchers. I guess I need to find a ball of wool !
That’s a great piece of problem solving. To your point of the wind tunnel I’ve used CFD software along with a 3D scan to solve aero issues in the past. I’m looking at solving an issue with heat flow from the radiator on an XJR-15 at the moment. The heat from radiator in the nose follows the nose and around the A pillar and into the tiny opening in the window. The cad cooks the driver in about 15 mins. So I’m looking at ways of disrupting the laminar flow along the surface to the window.
 

cobraboy

Well-Known Member
#59
That’s a great piece of problem solving. To your point of the wind tunnel I’ve used CFD software along with a 3D scan to solve aero issues in the past. I’m looking at solving an issue with heat flow from the radiator on an XJR-15 at the moment. The heat from radiator in the nose follows the nose and around the A pillar and into the tiny opening in the window. The cad cooks the driver in about 15 mins. So I’m looking at ways of disrupting the laminar flow along the surface to the window.
Maybe one of these on the window ?
Window Scoop A - ACW Motorsport Plastics, Polycarbonate Windows

Pics of the Jag would be cool !
 
#60
This is it on car
1610876159642.png
doesn't look quite that square in real life. picture nicked from another post elsewhere. It goes over and under the original front panel

re airflow, try dimples like a golf ball (or nulka the hovering rocket)
 
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