Anybody made their own composite skid plates?

I’m looking for some guidance. I want to build a composite skid plate for a car I have.

It’s a street car that will see a lot of our local dirt roads, and I’m trying to protect the oil sump, oil filter, and alternator. It may see some rallycrosses later on too.

My question is basically about the thickness of the laminate. Many years ago I helped a friend lay up composites for a skid plate for his VW rally car. Trouble is, it was late at night, we were drinking beers, and it was 17 years ago. I can’t recall how thick we made it. We used primarily kevlar with a few layers of carbon sandwiched in between to lend additional stiffness to it.

It won’t be a flat skid plate, I was figuring some ribs would be implemented into the design to reduce flex.

So...any ideas? 3/16” thick? I really can’t remember what we built it up to, but I want to say it was like 30 layers of 5.5 oz Kevlar, but that could be the beer talking.

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Opel is a 4-letter word...
http://www.flickr.com/photos/10498579@N07/sets/



Edited 1 time(s). Last edit at 03/11/2021 05:56PM by Ascona73.

Go Kevlar with ribs and no carbon layers, don't think more than 5 to 10 layers would be needed since DuPont say soft armor packs use 9 layers + 3mm foam + 1 layer and I don't think your gonna shoot .44s at it.

https://www.dupont.com/content/dam/dupont/amer/us/en/safety/public/documents/en/XP_K520_Data%20_Sheet%20_2020-05-18.pdf

If you really need more stiffness use carbon Kevlar weave.

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Philippe Bellefleur
Go Kevlar with ribs and no carbon layers, don't think more than 5 to 10 layers would be needed since DuPont say soft armor packs use 9 layers + 3mm foam + 1 layer and I don't think your gonna shoot .44s at it.

https://www.dupont.com/content/dam/dupont/amer/us/en/safety/public/documents/en/XP_K520_Data%20_Sheet%20_2020-05-18.pdf

If you really need more stiffness use carbon Kevlar weave.

I know I need more layers than 5 or 10. When my friend made his skid plate originally it was maybe half as thick as the final product and 100% Kevlar. It was very flexible. Kevlar is durable and abrasion resistant, but not very stiff. That’s why we added more and more layers and added the carbon.

It seems most 5 to 5.5 oz Kevlar is around .009” or .010” thick. But I don't know what that equates to with resin and vacuum bagging.

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Opel is a 4-letter word...
http://www.flickr.com/photos/10498579@N07/sets/

Flexibility also depends on the shape, what was the shape of your friends skid plate (flat?), did it have properly placed ribs? It's not supposed to be indestructible, just protect vital components. Also you never laminate materials with different stiffness's because all the stress will be taken by the stiffest layer until failure then the next. Plus, aren't you talking about a street car anyway?

I bent a 1/4" steel skidplate (might be 3/16"... sucker has to weigh 70lb) one night on the Interstate. Don't know what it was that I hit, maybe a ladder or a trailer ramp or something, it was dark and life went from being bored and drowsy to airborne and wide awake.

Plate paid for its weight in spades that day.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Quote
Philippe Bellefleur
Flexibility also depends on the shape, what was the shape of your friends skid plate (flat?), did it have properly placed ribs? It's not supposed to be indestructible, just protect vital components. Also you never laminate materials with different stiffness's because all the stress will be taken by the stiffest layer until failure then the next. Plus, aren't you talking about a street car anyway?

My friend’s skid plate was fairly convoluted, in fact he pulled the mold for his skid plate off a VW Motorsports skid plate.

Yes, my car is a street car. But it will probably see rallycross use as mentioned. It will see local dirt roads too, and I live in rural New Hampshire. Here is an example of a local road yesterday, and we literally just started mud season!

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Opel is a 4-letter word...
http://www.flickr.com/photos/10498579@N07/sets/

At first I thought you'd stolen a picture from my Facebook!!!!

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Andrew Steere
Lyndeborough, NH
KB1PJY

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fiasco
At first I thought you'd stolen a picture from my Facebook!!!!

I saw your pics on FB...yea, pretty much the same all over!

My driveway is all gravel and like 900 ft long. Last year it was a swamp. Hopefully it doesn’t get too trashed this spring.

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Opel is a 4-letter word...
http://www.flickr.com/photos/10498579@N07/sets/

For the record, this is what I built for my never-ending rally car project. I went with 1/4” thick 6061-T65 aluminum. Added a tubular framework up front.

I’d just prefer to use something lighter on the street car, and still protect the oil filter, oil pump, and oil pan.

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Opel is a 4-letter word...
http://www.flickr.com/photos/10498579@N07/sets/

The WRC Evo (?) skid plate that’s on Dave Clark’s merkur stage car is ~1/4” thick laminate using a carbon-Kevlar weave. Ridges/convolutions are probably 1/2” tall and 2” wide.
I can convert that to SI units if desired.

I worked with a shop that also made carbon open wheel race car parts a while. They had nomex honeycomb that was sandwiched in and added thickness to the kevlar and carbon stuff they made. Overall part thickness was maybe half inch in the end but the strength and stiffness was impressive. That stuff would follow compound curves nicely too. Defibrillator sandwich something in there to keep it rigid rather than use more layers.

Rallycross usually doesn't even need a skid plate around here unless your struts are shot.

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Perry

FE570s course bike
KTM 950 ADV
74 Beetle turbo-efi etc..
72 Beetle stage rally project WRX powered
Attended about 15 rallies, usually a volunteer in a course car.