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........................................---- Spoilers -- Page 8 ---
...................Pictures of different Spoilers/Spill Plates and Skirts.
Spoilers/Spill Plates/Wycer Bills (Gurney strips) -- Here is what I think I know about them. This is not gospel just my opinions based on what might be facts. The allowed spoiler (not all classes allow them) can give you various degrees of downforce depending on there angle. More importantly in some cases they are what you attach the side spill plates to.
The side spill plates will act like a tail and help to keep the car running straight, which is a good idea. Personally in most cases I would make the spill plates as big as possible so that when you look at the car from the side they are as large as possible. I would try and run the spoiler at what ever angle created the least downforce until down force is needed. You have to remember to create the downforce you will also probably be adding drag to the car and drag requires ever increasing amounts of HP as the speed goes up. Having large Spill Plates probably adds no measurable amount of drag, but can do a lot to help keep the car running straight.
Wycer Bills (Gurney strips) according to the 2006 rule book "are allowed but cannot extend above the side
of the spill plates". Basically they are a piece going across the top of the spoiler at it's rear edge that
stick up at an angle and are like a spoiler on the spoiler. There again they are going to make the air turbulent
and while adding downforce are also going to add drag to the car, so are not in my opinion a good fix to a problem,
but might have to be used. The reason you see land speed cars add sometime thousands of pounds of weight vs. more
spoiler or a wing if allowed is it takes less hp to move the weight along at high speed vs. overcoming drag that
is induced by things like spoilers and wycer bills.
Skirts by the 2006 rules are "streamlining devices added to the lower portion of the body for the purposes
of controlling airflow under the body. The skirts can be a maximum 1/2" thick. The skirts shall be in a single
plane, mounted to the bottom of the body but cannot modify the contour of the body. The skirts may extend from
the centerline of the front axle to a vertical plane at the rearmost point of the original body line". Besides
controlling airflow under the body they can help in the attempt to keeping the car running straight as they add
more area to the side view of the car like the spill plates do and this can be especially good if this area is
at the rear of the car.
Any side view area you add to the back of the car is going to help it go straight by moving the center of pressure
(CP) towards the rear of the car and hopefully behind the center of gravity (CG) for the car.
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A spoiler with Spill Plates on a Coupe (competition coupe). This coupe looks like it is running the maximum size spoiler (10 inches long [as of 2006] ) and almost the largest legal Spill Plates on the side (8 inches above and 8 inches below the spoiler). The spill plates could have extended 2 inches past the back of the spoiler (the horizontal piece). The spill plates might come into question as they can not extend past the centerline of the rear axle and they might possible be past that centerline. There is no wycer bill (Gurney strip) on this car.
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This is Hooley's stude being prepared to run in 2004 for the first time (Hooley on the left and John to the right). At this time we had no clue what the spill plates on the side did, so Hooley just made them to kind of look like ones he had seen. The car ran 219 mph like this with a 3000 lb. weight and went pretty straight..
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Between 2004 and 2005 we learned the purpose of spill plates and made new ones that were as large as the rules permitted (see picture). Due to the very rough track in 2005 top speed was 212 at 30% throttle, but Hooley kept the car pointed in the right direction and I give some of the credit for that happening to the larger spill plates.
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A rear view of the spoiler and new spill plates. The spoiler is a little bit adjustable with the supports. For this year (2006) Hooley made some Wycer Bills that can attach to the rear of the spoiler and bent to different angles. We won't attach them unless we feel we need them. We also have provisions now to add up to 1000 lbs. of weight if we feel it is needed...
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In 2005 John also made these skirts at the bottoms of the rear quarter panels to help with air under the car and to hopefully help keep the car running straight.
If you have some spoiler pictures you would like to add send them to me, Sum.