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Thread: Lizard Skin or Not

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  1. #1
    Carl carlewms's Avatar
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    Terry,

    Another factor in your decision should be wether you have the compressor to use to spray on the Lizard Skin. I was planning to use Lizard Skin because I really think it has the most flexibility and EdwardB's build thread provided an excellent path to getting it done but in the end I went with Dynamat Extreme because I lacked the compressor.

    I also looked at other lesser products and went with the DE after reviewing some issues with running of the butyl rubber when hot, etc. Like EdwardB said ... your spending a lot of money on the rest of the car so why go cheap now on a critical component.

    If you have the equipment to apply it based on my view it is less expensive and easier to apply than the DE type product. You spend a lot of time templating and cutting the DE type product...and if you screw it up like I did ... you end up with some wasted pieces.

    Just my two cents ...

    Carl
    Mk 4 Roadster
    October 25, 2012 - Kit Arrives
    April 8, 2013 - Build Starts
    August 23, 2015 - Rolling Chassis/Engine & Transmission Installed
    March 26, 2016 - Go Cart

  2. #2
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    wallace18's Avatar
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    I put on the lizard skin with a roller. Note: You must first put on the lizard skin sound deadener then the ceramic heat barrier. That is per manufactures instructions

  3. #3
    Senior Member mjazzka's Avatar
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    Quote Originally Posted by wallace18 View Post
    I put on the lizard skin with a roller. Note: You must first put on the lizard skin sound deadener then the ceramic heat barrier. That is per manufactures instructions
    I think I might go that way if I paint the panels before installation. Your panels look great, so I don't have any qualms about doing that then. Thanks for blazing the trail!
    Michael
    Coupe #675 "Eloise"


    10/14/14 Coupe Ordered - 1/29/15 Coupe Delivered - 5/1/16 First Start
    Build Thread - Flickr

  4. #4
    Senior Member edwardb's Avatar
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    Heat Test Data

    This thread reminds me again how often heat and sound control are discussed, and the multiple approaches guys take with their builds. Everyone it seems has heard about (or experienced) getting their feet cooked in one of these things, so want to avoid that with their car. That part I understand. What I not sure about though is whether we know what's really happening with heat transfer between the engine compartment and the cockpit. Yes, there are some real heat sources up there, and they are surprisingly close to pretty thin aluminum sheet, and our extremities are not too far away on the other side. So we have every reason to be concerned. Thought about this last night a bit, and realized I hadn't seen much real data on the subject. So did a little testing today.

    My Mk4 Roadster has powder coated panels throughout, including the engine bay and firewall. No insulation on the engine side. It has FFR/BBK ceramic coated headers going into 4-into-4 side pipes. No cats. It has Lizard Skin heat and sound insulation sprayed on the cockpit side all over including all sides of the footboxes, floor, plus the inside of the firewall. Then the FFR supplied carpet. Note that this is exactly the same as what I did on my Mk3 Roadster. In both cases, in 3+ seasons with the Mk3, and now starting this season with the Mk4, we've never felt any additional heat from the footboxes or anywhere for that matter. And we've cruised in some very hot and humid weather. But what is really happening? How much heat is actually getting to the sheet metal?

    Today I needed to run an errand and used the Roadster. Was only 10-15 miles total, but the engine was at full operating temp (185+) and warm enough that the cooling fan was running for most of the return trip home. I charted 12 measurement points where the headers are closest to the footboxes. #3 and #4 headers wrap around close on the PS. #7 and #8 on the DS. The distance to the footboxes for these headers is anywhere from 1-1/2 inches to as close as 1/2 inch. Using my trusty HF non-contact infrared thermometer, I measured all 12 points at the end of my drive with the car back in the garage and still running. What I found was the headers were in the 340-350-360 degree range, and directly across from that point on the aluminum, the max was 210 degrees (1/2 inch gap) but most were 150 - 170 degrees. So, not surprisingly, there is definitely radiating heat warming the panels, and it varies by just how close the heat source is. Probably could have figured that out without testing. But even with a pretty small air gap, the drop off in temperature from the headers is pretty significant. But what really surprised me was that these measurements were directly adjacent to where the headers were nearest the sheet metal. Go just a few inches away, and the temps fall off dramatically. Warm to the touch, but definitely not hot.

    Conclusions from this IMO? There are hot spots from the headers, but maybe not as much as you might expect. The balance is warm but hardly hot. Directly where the headers are closest to the sheet metal the insulation panels and standoffs that some install might be doing something. But at least in my experience, that's where the least space is available, and without further testing (e.g. in an unfinished build with nothing on the inside) I'm not sure how much these relatively small hot spots really make it to the inside. For the balance, a reasonable heat barrier on either side easily can handle the slightly elevated temps. For appearance purposes, I chose the inside. I like the look of the powder coat panels much more than some kind of insulation. Belt and suspender approaches (heat barriers on both sides, etc.) are overkill in my opinion, and the data appears to support that.
    Last edited by edwardb; 05-22-2015 at 04:01 PM.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

  5. #5
    Senior Member mjazzka's Avatar
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    edwardb, I think your analysis would line up with an engineering approach taken to it. It would be interesting to see a comparison of heat transfer by radiation vs convection. My quick thoughts on it:

    Radiation: Heat transfer by radiation is largely determined by the effective surface area of the two objects in a direct line of sight. The parts of the Al panels closest to the headers would see the most radiation, and as you get farther away from the headers on the same Al panel there is a larger angle of incidence resulting in more panel area for the the same radiation flux, resulting in less heat transfer per unit area. Also, reflected radiation would have more places to go resulting in a further HT advantage. If you can cut off the biggest source of radiation at the source (e.g. wraps), you can minimize the amount of HT by radiation. If you can't do it at the source, then I would personally try to get as close to it as possible (e.g. heat shields offset from the panels). This also provides an air gap, although these offset panels might need to be fairly robust. Once you get to the solid layer of the aluminum panels, the order of layers doesn't matter except for which you want your foot to be in contact with or see on the interior. This is conductive HT, though.

    Convective: Obviously the air in the engine bay will be heated by the engine and headers. Heat removal from the engine bay correctly is imperative to reducing convective HT. Convective HT largely depends on the flow path of the air, so possible ways to mitigate it would be to break up certain airflows or maximize others to shuttle the heat where you want it to go instead of places you don't want it to.

    Interesting stuff!
    Michael
    Coupe #675 "Eloise"


    10/14/14 Coupe Ordered - 1/29/15 Coupe Delivered - 5/1/16 First Start
    Build Thread - Flickr

  6. #6
    Senior Member edwardb's Avatar
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    Quote Originally Posted by mjazzka View Post
    edwardb, I think your analysis would line up with an engineering approach taken to it. It would be interesting to see a comparison of heat transfer by radiation vs convection. My quick thoughts on it:

    Radiation: Heat transfer by radiation is largely determined by the effective surface area of the two objects in a direct line of sight. The parts of the Al panels closest to the headers would see the most radiation, and as you get farther away from the headers on the same Al panel there is a larger angle of incidence resulting in more panel area for the the same radiation flux, resulting in less heat transfer per unit area. Also, reflected radiation would have more places to go resulting in a further HT advantage. If you can cut off the biggest source of radiation at the source (e.g. wraps), you can minimize the amount of HT by radiation. If you can't do it at the source, then I would personally try to get as close to it as possible (e.g. heat shields offset from the panels). This also provides an air gap, although these offset panels might need to be fairly robust. Once you get to the solid layer of the aluminum panels, the order of layers doesn't matter except for which you want your foot to be in contact with or see on the interior. This is conductive HT, though.

    Convective: Obviously the air in the engine bay will be heated by the engine and headers. Heat removal from the engine bay correctly is imperative to reducing convective HT. Convective HT largely depends on the flow path of the air, so possible ways to mitigate it would be to break up certain airflows or maximize others to shuttle the heat where you want it to go instead of places you don't want it to.

    Interesting stuff!
    Good feedback. You're absolutely right. I was measuring radiated heat, as this is by far the hottest underhood source. My test wouldn't have been too useful for convective heat since at that point I was stopped and with the hood open. My sense with the Roadster is that air moves through the engine compartment pretty well, and stick with my conclusion that "reasonable" insulation is going to manage it. I personally don't have knowledge/experience with the Coupe, so don't know how they compare. Header wraps are a whole other discussion. Don't see them too often on either forum, and it seems a trade-off between maybe saving some radiated heat but causing long term damage to the headers due to trapped moisture, etc. Not to mention they have an effect on the combustion process which is often the main reason they're used.
    Last edited by edwardb; 05-22-2015 at 01:21 PM.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

  7. #7
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    One of the vendors on the FF website has a kit they sell for the Roadster, it includes thermal and acoustic barriers for the firewall, wheelwells, etc. The guy told me it would work fine for the Coupe too, just need a little more for under the headliner, etc. I think it was about $550.

  8. #8
    Senior Member mjazzka's Avatar
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    Quote Originally Posted by carlewms View Post
    Like EdwardB said ... your spending a lot of money on the rest of the car so why go cheap now on a critical component.
    There are a ridiculous number of "critical" components in these cars, so if I had that mindset about all of them I wouldn't be able to build the car due to cost . Tragedy of the Commons, in an interesting way. If I had no qualms on cost then sure, LS or Dynamat or any of the name brand things would be the way to go for everything. It's just another option for Terry!
    Michael
    Coupe #675 "Eloise"


    10/14/14 Coupe Ordered - 1/29/15 Coupe Delivered - 5/1/16 First Start
    Build Thread - Flickr

  9. #9
    Senior Member edwardb's Avatar
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    Quote Originally Posted by mjazzka View Post
    There are a ridiculous number of "critical" components in these cars, so if I had that mindset about all of them I wouldn't be able to build the car due to cost . Tragedy of the Commons, in an interesting way. If I had no qualms on cost then sure, LS or Dynamat or any of the name brand things would be the way to go for everything. It's just another option for Terry!
    Figured my comment might hit a nerve... There's no question these things aren't cheap, and most of us aren't on an unlimited budget. Yes there are a lot of critical components. But there is no one answer. In the end it becomes a question of risk vs. reward, and ease of recovery should be wrong decision be made. I try to think of the end product, and how easy (or hard) it would be to recover from a wrong decision. Controlling heat and sound control makes a big difference in the quality of the end product IMO. Whether on the engine/firewall side, or the cockpit side, adding or changing heat and sound control to a completed car would be a real pain. That's the context of why I wouldn't experiment and pay what I think is a pretty minimal amount to use a proven solution.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

  10. #10
    Senior Member mjazzka's Avatar
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    We're on the same page, I have no doubt! You are right about risk vs. reward, that's the question every builder asks themselves, and there is no correct answer that fits everyone. I personally don't look at sound and heat insulation as mission critical to the functioning of the car (like engine or transmission work are, for example), but others like yourself understandably do. They would be a great addition for me though! So while I understand how you probably wouldn't want to experiment, my point is simply that the technology isn't that complicated and a reasonable efficiency can be achieved for much cheaper for those who are willing. I think this is just another small chapter in the age old DIY debate lol

    Quote Originally Posted by edwardb View Post
    Figured my comment might hit a nerve... There's no question these things aren't cheap, and most of us aren't on an unlimited budget. Yes there are a lot of critical components. But there is no one answer. In the end it becomes a question of risk vs. reward, and ease of recovery should be wrong decision be made. I try to think of the end product, and how easy (or hard) it would be to recover from a wrong decision. Controlling heat and sound control makes a big difference in the quality of the end product IMO. Whether on the engine/firewall side, or the cockpit side, adding or changing heat and sound control to a completed car would be a real pain. That's the context of why I wouldn't experiment and pay what I think is a pretty minimal amount to use a proven solution.
    Michael
    Coupe #675 "Eloise"


    10/14/14 Coupe Ordered - 1/29/15 Coupe Delivered - 5/1/16 First Start
    Build Thread - Flickr

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