Rivets and downforce

[rickb99]

So there we were post race. Jeff had a nice run finishing 2nd overall and we were preparing to put the car on the trailer. Low and behold, as I was removing the rear wing ( man them bolts get HOT! ) my brother notices something amiss. All the rivets that attach the bottom element mounting plate have sheared through!!! Only thing holding the element in is the mounting plate thickness inside the wing cord and the compression of the wing side panels. The wrong bump or vibration and the entire lower element could have detached!

I'm sure this failure took years to accomplish and I think all we need to do is re-rivet.

But in the course of the discussion, the question came up. Without a major aerodynamic discussion, about how much downforce does the 2 element (upper and lower) develop at say 130 MPH? Yes angle of attack and design is everything, and I realize this will be a plus/minus number but ball park please?

P.S.
Reminder to self. Remove wing elements and inspect rivets a couple of times a year

[Charles Warner]

One major cause of this is that the wing gets so much more working while being trailered. Think about it. Especially if the car is not secured through the suspension system and is locked to the trailer, transmitting every bump throughout the car. Rear wings should be removed before transporting for best life. It sounds as if you do this so the damage may have been long-standing.

[Stan Clayton]

We have seen this happen many times on alloy FA rear wings, to the point where we are abandoning them in favor of composite wings at the rear as well as the front. (See our new all-composite rear FA wing at the Sprints... )

And once one rivet fails, the rest will tend to let go too, zipper style, so look at them after each event. If a rivet has failed, drill it out and replace it right away.

[rickb99]

One major cause of this is that the wing gets so much more working while being trailered,,,,. It sounds as if you do this so the damage may have been long-standing.

Charles,

This was the 1st race of the year for Jeff and the FIRST race we've removed the wing for towing. The topic of towing stress on the wing came up on the Forum over the winter which is the reason we 'now' do it. Good thing we didn't make this tow with it or the failure would have happened sooner!

We have seen this happen many times on alloy FA rear wings, to the point where we are abandoning them in favor of composite wings...... And once one rivet fails, the rest will tend to let go too, zipper style, so look at them after each event. If a rivet has failed, drill it out and replace it right away.

Copy that inspection and replace thing, Stan. I've never seen this before or read any comment about rivet failures in the wing mounting plates on the Forum. It will certainly be a part of our pre-race inspection, NOW! Composite wings. We can only dream of such things

BUT.. BUT:
Nobody has answered the second question. About, approximately, ball park how much down force do the rear wings typically generate at about 130 MPH? Just roughly, plus/minus? Is it 300 pounds or 400 pounds or 600 pounds??? Assuming a good wing design.

Or are we all adding subtracting down force of unknown value to see if we go faster with no quantitative info?

[Stan Clayton]

BUT.. BUT:
Nobody has answered the second question. About, approximately, ball park how much down force do the rear wings typically generate at about 130 MPH? Just roughly, plus/minus? Is it 300 pounds or 400 pounds or 600 pounds??? Assuming a good wing design.

According to our CFD studies a current popular aftermarket FC wing package should net you a bit over 200 lbs df at 130 mph from the front and rear wings combined.

[RobLav]

My lower rear wing mounts are made of aluminum plate screwed into wing ribs in double shear. I made a very long SHCS socket and extension to fit through the side of the wing to mount them. No rivets. So there are alternatives.

In my view, there is too much vibration there for rivets. If you must, then try some real aircraft rivets. I was able to hand pull about 700 of the 5/32 and 3/16 versions for my belly pan.

[rickb99]

In my view, there is too much vibration there for rivets. If you must, then try some real aircraft rivets. I was able to hand pull about 700 of the 5/32 and 3/16 versions for my belly pan.

I didn't take a close look at the damage Sunday as we were trying to get home. Will take a serious look next Sunday and decide if we can "SAFELY" repair it ourselves or send it off to a "pro".

[Peter Horvath]

Where the rear wing bolts to the back of the gearbox, with three long bolts, through three holes cast into the gearbox cover...
You may want to check this area too, Rick...
I found the upper cast hole to be cracked almost through, during my winter inspections.
Just a thought, not a hijack.

[formulasuper]

My lower rear wing mounts are made of aluminum plate screwed into wing ribs in double shear. I made a very long SHCS socket and extension to fit through the side of the wing to mount them. No rivets. So there are alternatives.

In my view, there is too much vibration there for rivets. If you must, then try some real aircraft rivets. I was able to hand pull about 700 of the 5/32 and 3/16 versions for my belly pan.

Rob is right, by all means - use aircraft blind rivets where you don't have access to the back side for installing solid rivets. Those screen door pop rivits are good for just that; screen doors!

[rickb99]

Where the rear wing bolts to the back of the gearbox, with three long bolts, through three holes cast into the gearbox cover...
You may want to check this area too, Rick...
I found the upper cast hole to be cracked almost through, during my winter inspections.
Just a thought, not a hijack.

Hmm... We have a MK8/9 and the cover has bosses for 2 long bolts, not 3. Is that on an LD200?

In any case will inspect

Yes on rivets. I do NOT intend to run down to Home Depot for them

[kea]

Yes, the original LD200 rear cover had those cracking problems. The Mk8/9 covers available (most were a custom welded version) do not.

[jabro1000]

WHOLEY FREAKING RIVETS!!!

This isn't Jeff, it's Rick. I'm at Jeff's house and was looking for something else when I came across this video by Belling.

Watch the rear wing. NO WONDER we have wing rivet failures! Actually looks like it develops a harmonic oscillation in the vertical plane on some parts of Pacific Raceway.

http://www.strimoo.com/video/1214639...ART-Vimeo.html

[kea]

Rivets alone won't last very long that's why we "glue" it together at the same time during construction.

[rickb99]

Keith,

I figured glue or epoxy also. What kind do you recommend? JB Weld comes to mind but I'm guessing it's NOT a good idea for future repairs

[kea]

I use Hysol

[Peter Horvath]

That wing vibration can't be good, for the downforce as well as the wing.
Making the vertical panels out of carbon fiber should fix it, but that would violate the GCR.
Still, some supports or cross-members might be in order.

[rickb99]

That wing vibration can't be good, for the downforce as well as the wing.....

Still, some supports or cross-members might be in order.

Yes, was thinking the same thing, Peter. With all that shake going on the air flow over the upper element has to be disturbed. Not sure how you'd brace it though. You'd want to keep any cross member really slender so as not to cause drag or ruin the air flow over the wing elements.

Maybe diagonal guy wires? I have a vague memory of seeing wings with guy wire bracing in the past.

Wish I could find a similar angle video from Portland International. Bet it's smooth as can be.

Carbon fiber probably but ouch on the cost!

Maybe this will all get better if the pave the track in about 4 years

[kea]

This was taken two years ago at Grattan. The car turned in a little to early and cut the corner. When I took a look at the wing and it's end plate in the paddock later, you could not see any evidence of what the photo shows it went through.

[rickb99]

Yikes! That looks like Scotty hit about Warp 9.6!

How do you feel about guy wires on the diagonal between the upper and lower elements for us guys who have to run ultra-rough tracks, Keith? Although we don't run it often, Bremetron (old airport runways) is just as bad as Pacific Raceway.

[azjc]

This was taken two years ago at Grattan. The car turned in a little to early and cut the corner. When I took a look at the wing and it's end plate in the paddock later, you could not see any evidence of what the photo shows it went through.

I've been guessing that some flex is normal? Not the direction it's (sideways) loaded & no flex means it's either way overbuilt or going to break instead ?

[RedRacer27]

Att pic shows the damage just using some kerb does at most tracks. This is a slow speed 2nd gear chicane at Snetterton (UK).. but give you an idea of the abuse they take.

I would recommend changing lower wing and supports every season..

Attachment 14890

[rickb99]

I would recommend changing lower wing and supports every season..

Wow, interesting photo. I guess watching from track side you really can't see what's happening to wings under racing conditions. Would be good to see some more snap shots of wings taking abuse.

Until that Belling video and these still shots, I've never seen any other pictures of wings going through flex like that.

Red,

As to your suggestion. Could you UPS a medium sized cloth bag filled with Euro's? The lower element and end plates are 80% of the cost of an ENTIRE wing! Big hit on our annual budget to do that.

[GK Gent]

Jeff, we run a 89SF and have seen exactly what you are going thru. If you could send me a pic of your lower lug/spar design, (without the skin), I can help. We found alot of flex in the lower section due to poor fitment, weak design and generally somebody not thinking about how it was assembled. We also found that our endplates and upper wing assemblies were way out of line in the weight factor that really worked the lower lug/spar HARD in a 2g corner. Let me know.

GK

[RacerDave51]

I use Hysol

Which one--there are a zillion formulas...

[kea]

I use Hysol 9430 most often.

[RacerDave51]

Thanks. I'm adding small Alum strakes to my diffuser...

[rickb99]

We seem to have fallen in to a pattern of NOT getting ready too far in advance of any given race weekend. With Jeff's next event being Aug. 1/2, I took the wing apart yesterday afternoon (too late to call Averill).

Interesting failure. There are 'inserts' in each end of the wing in the shape of the air foil that are riveted/epoxyed in and have floating rivnuts to fasten the wing assembly to the wing end plates.

Oen had all the rivets sheared off except for 3. On the section that did not shear off, the stress's caused a fracture to develop and broke the 'tab section' off that had the rivets on it (in two areas). So, it's in three pieces. This is the one that brought the failure to our attention when it pulled way loose at the end of the race in Portland.

The 2nd one has suffered stress fatigue in 2 areas around several rivnut plates and two sections of the insert fell out when removed from the assembly. So it's in 3 pieces.

As soon as I finish my 4 cups of coffee and get to my turn station (working a lapping day) I'll be on the phone to Keith Averill to see if he stocks these parts. If not, it will be a JB Weld job for the race until we can get some new ones

One more reason to disassemble and INSPECT the wings at least every winter!!

[Steven L]

I use Hysol 9430 most often.

Anyone/Everyone,
At about what angle should I start running the front and rear wings on a RF 94-95 I just got before I start committing to different tracks?

Steve

[rickb99]

Hi STEVE ! !

Totally missed your question there. We are running with IRDC at Pacific tomorrow and Sunday. COME ON OUT!!

We are paddocked right across from the snack bar on the 'sorta' access road way. Next to Al Carton and Dick Boggs with their D/SR's.

Wings:
We're using the Averill wings on our Reynard.. about 0 to 1 degree on the front and somewhere between 8 and 12 on the upper rear.

I'm guessing the Van Diemen wings are different as it depends on the cord design and what people have found out about the way they react in the air flow.

Not sure if Mike Lensen will be here this weekend but I'm SURE he would tell you what wing settings he's using on his VD.

Anybody have a good answer for Steve on starting wing angles for the VD???

WING PARTS:
You can ALWAYS count on Keith Averill. Called him and he fab'd up a couple of the internal wing ends. Had them shipped within 2 days and we're off to the track !!