Wind Wings cracking

[PaulProe]

I am having issues with the clear plexi wind wings cracking. The cracks begin as a slight crack from one of the screw holes and eventually grows to the edge of the wing.

Once that crack is established, it takes very little for the wing to crack all the way across and break in half. So far, I've gone thru two and a third one has now developed cracks.

They are coming from Finishline. The only thing I can guess is to maybe burnish the countersink with the screw in hopes of creating a better contact area. I don't think I am over-tightening but that is really hard to judge on a 10-32 screw.

Any other ideas on how to prevent this?

Paul

[CHANMADD]

Lexan..........

[COBRANIP]

Is there enough material to drill the hole out larger and insert a metal sleeve (tubing), (slightly counter the plastic) and the tubing if it is ever so "proud" could take more of the clamp load?

If not, I really like CHANMADD's suggestion.

[nealgs]

Hi Paul,

I assume the holes in the wind wing material are in the correct location, they most definately shouldn't be cracking. There shouldn't be any stress (or at least not enough) to cause the material to crack, unless it's a bad batch of material that Finishline have been given.

Do you have fibre washers between screw head/plexi and nut/hinge?

May also be worth making some yourself. Very easy to do, using 4mm - 6mm thick lexan, a jigsaw and some varying grades of wet n dry.

I made my own using 5mm lexan, using the original as a template (originals were glass) and made 4 pairs from the single piece of lexan. total cost was < GPB10 ($16?). Current pair have been fitted for around 1yr, no signs of splitting/fractures etc.

rgds
Gary

[Ralphy]

Lexan does age, I'm not sure what grade of Lexan they are made of. You may need to replace, the cracks will continue because they are getting brittle.

Ralphy

[CHANMADD]

I have had lexan wings and windshield for years, and can still take a hammer and tap both with no problems.

[streetrod1927]

I'm on my second set as well. I think it is mainly due to the constant shake of the car in general. I have tried to make rubber inserts for the countersunk hole using modified beveled faucet washers. This seems to be holding up. Time will tell however. Glass or lexan is most likely the way to go.

[Skuzzy]

If it is Lexan, the holes where the screws go through should be stressed relieved. If they are not, it will be a source for cracks to start.

A simple rounding of the edges is all that is needed. Make sure that step was not missed in the manufacturing of the wings.

Just a thought.

[FWB]

when putting holes in plastic care must be taken to not stress the material or it will crack just like you describe. with that being said plowing a drill through a Plexiglas piece takes special care when the drill exits the other side. that is where the stress is greatest.
whether the material is Plexiglas or trade name Lexan is irrelevant,... lexan is Plexiglas...but with optical qualities.

to replace the wings, i would opt for a set made locally, you are more inclined to get better quality. save the old ones for a template. material can be bought through Mcmaster-carr online

[strictlypersonl]

Originally Posted by FWB

whether the material is Plexiglas or trade name Lexan is irrelevant,... lexan is Plexiglas...but with optical qualities.

Lexan® > Polycarbonate
Plexiglas® > Acrylic

Completely different "alloys" of plastic. In general, acrylic has better optical qualities than polycarbonate, which is softer and tougher. You can get hard-coated polycarbonate with better wear and optical qualities.

[FWB]

Originally Posted by strictlypersonl

Lexan® > Polycarbonate
Plexiglas® > Acrylic

Completely different "alloys" of plastic. In general, acrylic has better optical qualities than polycarbonate, which is softer and tougher. You can get hard-coated polycarbonate with better wear and optical qualities.

yes your right.....see what age does... age affects your 'P's

as far as drilling either the same applies...as the drill point goes through, the lands of the drill tend to put the undo stress on the material.

on thin plastic i like to plunge out holes with an endmill or circle mill the hole in......

[lal Naja]

When drilling through Lucite/Acrylic/Plexi-Glass, Lexan/Polycarbonate and Fiberglass you need to use a drill bit that has a point and cutting edge that is designed specifically for these materials.

You can buy these from a supplier like McMaster Carr and is cheaper than the heart break you will experience when you crack your material.

If you know how to sharpen drill bits you can make your own by first sharpening the tip to about a 70 degree point. Then you grind the two leading edges (cutting edges) of the drill bit to increase the angle of the cutting edge. It is very easy to do. In actuality you are giving the cutting edge a less acute angle.

Slow spiral drill bits are also better for drilling these materials with modified tips as I've tried to explain.

Good luck!

[PaulProe]

Did some research on making them from Lexan(PolyCarbonate) and found a real eye-opener. From GE specs:

Do not use countersunk head screws as the ‘wedging’ action of the countersunk head causes excessive hoop stress on the sheet. This can
lead to part failure.

Guess what type of screws are used in the typical aftermarket windwings

Looks like I end up copying how Superformance does theirs and just using a truss head screw on the new Lexan wings I am making. Not as pretty but I don't need to continue to feed the monster.

Thanks for the input

Paul

in case you're curious, this is a link to the GE specs

[Ralphy]

Hey Paul, go ahead and do that and there go your aerodynamics, laughingly. Another way might be to make up a thin small stainless plate. The same dimensions as the hinge and sandwich the wing between. This would reduce stresses over an even wider area.

[CSX3018]

Hello
Not like me to make anybody life go easier.
Buy Saftet Glass wind wings.they don't say Cobra, but don't crack or scratch
and cost more and are hard to find.
Thank You

R.H.M