Lizard Skin or Not

[Terry]

Hi Everyone

My name is Terry and I have Coupe number 637. I am contemplating spraying the firewall and foot boxes with Lizard Skin Ceramic coating, in the hopes of reducing heat transfer to the cockpit. I am very close to installing the engine and gearbox and was wondering if anyone had used this product, and was it worth the effort. Any other suggestions for reducing heat transfer would be much appreciated. Should I wrap the headers?

Thanks!!
Terry

[mjazzka]

Terry,

Glad you are in the forum! There are a bunch of great guys here to help.

That's very interesting you bring this up right now because I am going through the same situation. I looked up Lizard Skin and it is EXPENSIVE. In keeping with my DIY build I looked up alternatives and found this link: http://www.hotrodders.com/forum/alternative-lizard-skin-103610.html

While you aren't going to be able to replicate the exact properties of Lizard Skin, thermal conduction and sound deadening are not exactly rocket science. Using micro balloons in a paint will increase the thermal resistance by adding insulating layers, thereby decreasing heat transfer. I've seen a few applications of the DIY stuff and it looks like it could be a very viable option. Try around $30-$40 for raw materials of ~3 gallons instead of $90 for one gallon. Of course you still need an applicator, but that's what HF is for :)

I ordered some micro balloons today from Wicks Aircraft Supply and will be trying it out next week when they arrive. I'll keep you posted if you want, but it'll definitely be in my build thread.



Hi Everyone

My name is Terry and I have Coupe number 637. I am contemplating spraying the firewall and foot boxes with Lizard Skin Ceramic coating, in the hopes of reducing heat transfer to the cockpit. I am very close to installing the engine and gearbox and was wondering if anyone had used this product, and was it worth the effort. Any other suggestions for reducing heat transfer would be much appreciated. Should I wrap the headers?

Thanks!!
Terry

[MVRight]

Used it on my MkIV, but no in car experience yet. Anecdotally while applying and allowing to dry in the sun, one panels without LS were blistering hot on both sides, those with, cooler on one side. There are other products that will do the job, I went with this and likely some thin material on the inside for heat control. Does reduce the tinny sound of the panels.

[MikeJones]

I used Lizardskin - both the sound attenuating and heat product, sprayed both inside and outside. I have about 20,000 miles on the car. The products do a very good job of reducing the drum effect and giving weight to the panels. They also nicely seal the aluminum panels to get rid of any gaps and seams between the panels.

Apart from the drum effect, the reduction of noise is minimal, as there are enough pathways that through the aluminum isnt dominant.

The footboxes are very hot. I like to drive in bare feet. Before adding heat shields, I had to be careful not to touch the side of the footbox or else it would be quickly painful. Last year, we drove to mid-ohio (about 7 hours) and my son melted the soles on his running shoes. One of this years projects will be heat shields on the pass. side. Lizardskin reduces the heat transfer but it won't be cool to the touch and you will need shields. I also did not add the small hood scoops and wish I had to promote cool air injected across the headers. And yes my headers are wrapped too.

It also adds considerable weight so not for a challenge car. Would I do it again? Yes.

Regards, Mike

[edwardb]

Here's a thread I started over on the other forum showing my experience with Lizard Skin on my recently completed Mk4 Roadster: http://www.ffcars.com/forums/17-factory-five-roadsters/342954-lizard-skin-application-experience.html

Are you planning to do the cockpit side or the engine side? It's not clear from your original post. Personally, I would only used on the cockpit side. Then covered with carpet. Works great. The car pictured in the above thread is now legal and a driver. Just turned 400 miles today. Heat and sound control are great. While I'm very happy with the final product, it is still a latex material. So when dry it's hard but not rock hard. Fine for under carpet. IMO in the engine compartment would be hard keep looking nice. It that's important to you. Regarding cost, I guess it's all relative. Personally I'm not going to try to save $50 a gallon (or whatever) for a many multi-thousand dollar project by experimenting versus a proven solution. Other heat and sound products, like Dynamat, etc. will cost just as much or more to do the car. Good luck with your build.

[CJBergquist]

I made homemade lizard skin...micro balloons and exterior latex paint. I used it on all the sheet metal parts except the firewall. I used insulation on the inside of the firewall under the dash and around the outside of the foot box with heat shields. This link has some photos and comments if you scroll down on each photo.

https://www.flickr.com/photos/51103049@N00/sets/72157625554554979/with/5295367158/

[wallace18]

I used Lizard skin on the outside of all my aluminum. Then used Eastwood thermocoustic on the inside of all interior alum. Also made heat shields in the engine compartment. See my build thread. The end result is a very comfortable interior. with A/C even in 90+ degree days here in Florida.

4205742059

[Terry]

Thanks to everyone for all of the inputs!! Basically I will incorporate all of the suggestions, and do everything possible.
1.Lizard skin on the aluminum - definitely on the firewall, maybe inside as well
2. Thermocoustic on the inside for sure, plus carpet
3. Heatshields - I found some High temp 1/4" thick flexible ceramic insulation at Mcmaster-carr - So, I am thinking about making heatshield sandwiches in the engine compartment for both footboxes
4. Wrap the headers
5. install the small hood scoops to let fresh air into the engine compartment

And I thought I was close to dropping in the 427 crate motor with TKO 500 :p

Thanks again to everyone for responding!!

More to come...

Terry

[MikeJones]

Terry, for heat shields, you can also use an aluminum sheet spaced off the footbox by about 1/4 or 3/8". This provides an air gap and if open at bottom and top, will keep cool by convection as well. I don't have any pics', but I borrowed that idea from others so there should be photos out there. Also looks good polished and provides protection for the lizardskin.

Regards, Mike

[Terry]

Thanks Mike! I took your suggestions to heart, I won't be driving barefoot anytime soon!! But I will be installing the heatshields and installing the small scoops to allow air into the engine compartment.

Thank you Sir!!

Terry

[carlewms]

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

[wallace18]

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

[mjazzka]

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 :D . 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!

[mjazzka]

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!

[edwardb]

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 :D . 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.

[mjazzka]

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


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.

[edwardb]

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.

[mjazzka]

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!

[edwardb]

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.

[plschulten]

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.