Heat and Sound Proofing

Aerogel

Aerogel is an exotic insulation material invented by NASA. They are the lightest known solid and they have the lowest thermal conductivity of any known solid. The monolithic pieces (i.e., solid pieces) are typically very expensive, brittle and not interesting, at least yet, for car builders.

However, aerogel blankets are flexible, comparatively more affordable, light, and resistant to heat (390-1200 degrees F).  They have insulation properties that are three to five times better than polyurethane foam or Styrofoam per unit thickness.

Aerogels seem to be specified by their thermal conductivity rather than their R-value. Thermal conductivity is the measure of how easily heat flows through a specific type of material, independent of the thickness of the material in question. The lower a material's number, the better the thermal performance (i.e. the slower heat will travel through it).

R-value is a measure of resistance to heat flow through a given thickness of material. So the higher the R-value, the more thermal resistance the material has and therefore the better its insulating properties.

The following table compares the four aerogel products available at BuyAerogel.com. Why companies can't do this for you is beyond me! I have purchased samples of Spaceloft, Pyrogel XT and Thermal Wrap.

My plan is to use Pyrogel for anything near the exhaust due to its ability to tolerate heat up to 1,200 degrees F. I think it would be perfect on under the top of the tail. To improve appearances and performance I plan to use thin metal or gold foil on the side exposed to the engine. I intended to test reproduce the blow torch test, but I haven't gotten around to it yet ;-)

While Space loft tolerates a mere 390 degrees F, I believe that it has better insulation properties than Pyrogel. Therefore, I plan to use it for everything not near the exhaust. Specifically:

•  Two 5mm wraps on the 1.5" stainless steel coolant tubes in the side pods, these will then have a thin metal jacket on top
• 10mm between the coolant expansion tank and bulkead
• 5mm or 10 mm in and around the cockpit

Note that the materials will generate some dust and I assume that they loose efficiency if compressed. So I will try to cover it with thin metal or some other material if it's exposed to the passengers, outside elements, etc.

Comparison to Other Insulation Materials

I'm trying to compare the above products to "normal" insulation. I haven't had time to sort it out, but the R-value is calculated by using the formula

R-Value = l / λ

Where:

• l is the thickness of the material in meters and
• λ is the thermal conductivity in W/mK.

R-values expressed in United States customary units are about 5.67 times larger than those expressed in metric (SI) units.The R-value is measured in meters squared Kelvin per Watt (m2K/W)

• 3mm = 0.12"
• 5mm = 0.20"   (1.9)
• 6mm = 0.24"
• 10mm =  0.40"  (2.3)

http://www.designengineering.com/

DEI Floor & Tunnel Shield II

DEI Floor & Tunnel Shield II is constructed with an embossed 10 mil aluminum face bonded to 1/8” composite glass-fiber core and backed with a high-temp super-strong pressure-sensitive backing. It withstands up to 1750°F of direct continuous heat and the adhesive side holds past 450°F. Its improved multifaceted modern aluminum surface offers improved reflectivity and rigidity and allows for ease of installation. At only 3/16” thick (that's 0.188, but I measure it to be 0.125), this product can be shaped and trimmed for a custom fit and is ideal for minimal clearance areas.

Reflect-a-gold (AKA TRUMP TAPE)

I ordered a roll of Reflect-A-GOLD tape today. It's a metalized polyimide laminated to glass cloth which is good at reflecting radiant heat (850°F Continuous, 1500°F Intermittent). When I first saw I thought it was over the top, but it's recently started to grow on me. I'm now thinking about using it on the tube frame in the engine compartment like the car in the picture below.