Repair the undertrays???

[LakeSurfer]

Hello,

I'm just curious if anyone has repaired any of the the fibrous under tray junk using polyester resin/fiberglass. I have several years in aviation composites and think it would be a fun project to take them off and repair the road rash but i'm not sure if polyester resin is comparable with the OE material.

I'm not curious about "Just but a new one", "waste of time" or anything unproductive to the question of the post.

thank you in advance

-Mark

[roastbeef]

i haven't seen a successful repair, but there have been several successful aftermarket offerings. i stuck with oem.

https://www.m3post.com/forums/showth...ht=deansbimmer

https://www.turnermotorsport.com/p-3...m3-skid-plate/

https://www.fcpeuro.com/products/bmw...en-51757899820
https://www.fcpeuro.com/products/bmw...8i-51757896419
https://www.fcpeuro.com/products/bmw...ht-51757896420

[deansbimmer]

To answer your question, polyester resin is not compatible with the oe molding. It will not bond well and will peel off in short order.

fiberglass/carbon and resin repairs work great on components originally manufactured as composite. Not as much for plastics. Nor plastics with a bonded felt layer.

[BeaterM3]

Originally Posted by LakeSurfer

Hello,

I'm just curious if anyone has repaired any of the the fibrous under tray junk using polyester resin/fiberglass. I have several years in aviation composites and think it would be a fun project to take them off and repair the road rash but i'm not sure if polyester resin is comparable with the OE material.

I'm not curious about "Just but a new one", "waste of time" or anything unproductive to the question of the post.

thank you in advance

-Mark

You can usually find undertrays for cheap on Ebay.

[Powashiftin]

I repaired my undertray with one jb weld steel stick. It was a minor repair (including zip ties) but So far, so good. I did end up using the whole steel stick.

[SkiFly01]

I've had good success repairing a ripped mounting area using a mixture of aluminum duct tape as a backing on the inside and 3M adhesive 4475 for plastics. Good for small tears like after a sharp driveway entrance scrap but if you splode your undertray into an octopus it may be time for replacement.



Clear 5 oz. Plastic Adhesive,

[pbonsalb]

You can buy some time with a pop rivet gun, zip ties and thin sheet metal (bent/cut into repair strips). I did that for a few years.

I bought a used example of the original version of the deansbimmer plate and think it is the simplest replacement. It has pretty much eliminated the regular scrapings that my slightly lowered car suffered with the stock undertray and side wings.

A careful and patient person could make his own plate, out of aluminum or maybe splitter material, but doing a one-off project takes time.

[LakeSurfer]

Originally Posted by roastbeef

i haven't seen a successful repair, but there have been several successful aftermarket offerings. i stuck with oem.

https://www.m3post.com/forums/showth...ht=deansbimmer

https://www.turnermotorsport.com/p-3...m3-skid-plate/

https://www.fcpeuro.com/products/bmw...en-51757899820
https://www.fcpeuro.com/products/bmw...8i-51757896419
https://www.fcpeuro.com/products/bmw...ht-51757896420

Dang, that aluminum one piece panel would be stupid easy to make. ive got about 10 yards of carbon fiber and could probably knock it out in a weekend.

thanks a ton.

-Mark

[Scores]

Does anyone have a blueprint, or the specs? I feel like I could get the local CNC guy to bang one of these out for cheap.

[CHE///MIST3]

Originally Posted by LakeSurfer

Hello,

I'm just curious if anyone has repaired any of the the fibrous under tray junk using polyester resin/fiberglass. I have several years in aviation composites and think it would be a fun project to take them off and repair the road rash but i'm not sure if polyester resin is comparable with the OE material.

I'm not curious about "Just but a new one", "waste of time" or anything unproductive to the question of the post.

thank you in advance

-Mark

Deansbimmer is correct, neither polyester nor epoxy resin will bond very well to those surfaces, BUT I did manage to fix part of the front undertray (center section) where one of the screws had broken out and taken some tray material with it... by building it back up with fiberglass and epoxy resin and extending the repair far beyond the broken area onto roughly sanded plastic. This was just enough surface area+grip to allow me to build everything back up properly. I also replaced one of the side pieces so it would help hold it all together. So you CAN use composites to fix small sections that screw together, but don't expect large, broad surfaces to hold under road use. Hope this helps.

GM

[roastbeef]

Originally Posted by LakeSurfer

Dang, that aluminum one piece panel would be stupid easy to make. ive got about 10 yards of carbon fiber and could probably knock it out in a weekend.

thanks a ton.

-Mark

you'll still need some sort of grommet between the shield and the oil cooler outlet.
people don't realize the oem undertray plays a critical role in engine cooling. the oem piece is shaped like an airfoil and creates a low pressure area behind the cooler outlet to help with flow. a flat piece would be better than nothing, and should be good for longevity. i don't know how heavy it is. oem is pretty light weight and stout, but its not meant to be a curb feeler.

the turner piece is nice, but appears to be on the heavy side. its the heaviest of the three offerings, just eyeballing it. its complete and is the most like and oem. at $600, its also the most expensive.

[SAMM3Y]

Beef's right. The Turner tray has an airfoil design, replicating it would require some tig work. It's 6mm thick too and hard mounted via some hangers to the subframe. It's a nice piece but weighs about 12lbs, but it's low low weight so lowers the CG too The other draw back is the riveted fasteners for the outer pieces that start spinning and require holding with pliers once you remove it once, which is a PITA. IIRC they're brass rivets with stainless fasteners so I guess they couldn't do it any other way without a lot more work. There's a ton of fasteners... overall I like mine, if I cared about the weight so much It could be modified... It's nice if your cars low though, great protection.

[GRM Scott]

If your existing ones are in semi-decent shape and you've got the raw materials and some know-how, might be worth it to fab up some stronger ones using the stock pieces as relief mold templates.

[Frozen]

Originally Posted by LakeSurfer

I'm failing to see any "airfoil" design in the Tuner part. Saying it has airfoil design implies there is a "wing" shape to the part giving it an amount of lift or down force. I mean no disrespect and I would guarantee it was difficult to create but to me it looks like a flat panel with a couple seals mounted to it. I'm sure I'm making it out to be easier said then done but I'm also sure someone with a amount of skill and fabrication knowledge/tools could pull it off and diy it with time and patience as well a a 6 pack, maybe even a 3 pack.

As a side note It's interesting, the difference from a BMW forum to (insert a less expensive car forum) mentality where the BMW forum typically discourages diy and encourages "just buy a new one" where the other forums are quite opposite.

-Mark

But Deansbimmer already has one that's just about perfect for less than $500 shipped. How much is your time work to you? Do you really think it's worth fabricating one at this point?

[LakeSurfer]

Originally Posted by roastbeef

you'll still need some sort of grommet between the shield and the oil cooler outlet.
people don't realize the oem undertray plays a critical role in engine cooling. the oem piece is shaped like an airfoil and creates a low pressure area behind the cooler outlet to help with flow. a flat piece would be better than nothing, and should be good for longevity. i don't know how heavy it is. oem is pretty light weight and stout, but its not meant to be a curb feeler.

the turner piece is nice, but appears to be on the heavy side. its the heaviest of the three offerings, just eyeballing it. its complete and is the most like and oem. at $600, its also the most expensive.

The "grommet" you're referring to would be simply a 90 angle piece with a properly placed rubber seal. you could modify the flat panel and sort of bend the front of the "hole" up 1/2 inch or so to scoop the air more directly into the cooler. Either way the OEM parts seem excessive and over shaped.

-Mark

[LakeSurfer]

Originally Posted by Frozen

But Deansbimmer already has one that's just about perfect for less than $500 shipped. How much is your time work to you? Do you really think it's worth fabricating one at this point?

Yes, Yes I think its worth it. I get zero satisfaction out of remove and replace of just buying something off the shelf. I don't put monetary value on my time spent working on my cars and im not sure why anyone would. Its fun, its a hobby and the reward far outweighs anything else, even if failure is the end result because at the end of the day you've tried and you've learned something.

Make a carboard template = Free
transfer carboard template to carbon fiber flat panel = free as I already have the material.
make (carbon fiber) or use extruded aluminum 90 angles = free as I already have the material.
Rivet the seals to the the 90 angles = free as I already have the material.

Or use the OEM parts and repair them temporarily and use them for molds to make full carbon OEM replicas = free as I already have the material.

I just made it sound super easy but Im sure the F word would be heard from my garage by my neighbors a few times throughout the process.

Its again not about the money, its about if I can do it and do it the same or better then why not?

I consider myself a little different than most people I know. I've built several hollow wooden and foam surfboards, wooden and carbon fiber skateboards, electric guitars and acoustic, a table saw that cuts more actuate then my dewalt unit and the list goes on. Sometimes I fail and fail hard and other times i win but i always learn so I guess its always a win.

-Mark

[LakeSurfer]

Originally Posted by GRM Scott

If your existing ones are in semi-decent shape and you've got the raw materials and some know-how, might be worth it to fab up some stronger ones using the stock pieces as relief mold templates.

You read my mind. I worked in Aerospace Composites Engineering for several years and acquired tons of tooling and materials.

-Mark

[roastbeef]

Originally Posted by LakeSurfer

The "grommet" you're referring to would be simply a 90 angle piece with a properly placed rubber seal. you could modify the flat panel and sort of bend the front of the "hole" up 1/2 inch or so to scoop the air more directly into the cooler. Either way the OEM parts seem excessive and over shaped.

-Mark

The provision for the oil cooler is not a scoop, it's an outlet. And if you're going to keep it flat, I would try to incorporate a gurney flap in front of it.

[LakeSurfer]

Originally Posted by roastbeef

The provision for the oil cooler is not a scoop, it's an outlet. And if you're going to keep it flat, I would try to incorporate a gurney flap in front of it.

I'm starting to get confused, usually this is pretty easy to do with me. Isn't the oil cooler in the very front of the car and receives its cooling more from "ram air" via the center of the front bumper? and the hole in the bottom of the crappy under panel thing is to allow for air to escape and not necessarily enter through?

[roastbeef]

Originally Posted by LakeSurfer

I'm starting to get confused, usually this is pretty easy to do with me. Isn't the oil cooler in the very front of the car and receives its cooling more from "ram air" via the center of the front bumper? and the hole in the bottom of the crappy under panel thing is to allow for air to escape and not necessarily enter through?

Correct.

[SAMM3Y]

Originally Posted by Frozen

But Deansbimmer already has one that's just about perfect for less than $500 shipped. How much is your time work to you? Do you really think it's worth fabricating one at this point?

They put a dam on the front of the outlet which forces air around the dam and creates a low pressure zone on the other side which helps suck the air though at speeds. I guess airfoil is the wrong word. You could easily make your own with a grinder/welder and a little can do attitude. I've thought of cutting mine up and replacing some of thick ally for some sheet thin stuff to lighten it up but I just don't give a shit enough... I've never seen engine temps above 228 with mine, maybe the Turner tray helps, I have other Cooling "upgrades" though. CSF stuff.

I'm a big fan of diy and make it yourself, do what you want bud. You'll know what's effective by your cooling performance.

[03BeastCharmer]

Originally Posted by SAMM3Y

, I have other Cooling "upgrades" though. CSF stuff.

I'm a big fan of diy and make it yourself, do what you want bud. You'll know what's effective by your cooling performance.

What all have you done? All three coolers or just one or two?