NACA duct installation advise

[L66TEY]

Hi Ben,

Yes - I've unintentionally ended up creating two now similar threads. 

I'll be modifying the pedal box cover, to keep it air tight as such to the engine bay - albeit I'll need to cut it so it's contour follows the inner NACA duct face. 
Then plan is to design and 3D print a single piece of ducting to link the NACA with a hole in the pedal box cover. 

Im trying to make it such that others can replicate it if they'd want to. 

PS The black "sweat band" was on the car when I got it - does the job perfectly. 

[aerobod - near CYYC]

You may have better cooling effect by using the duct the right way around (curvature not withstanding) and pushing air into the footwell, as the inside of the cockpit is liable to be at a lower pressure with the roof off.

[L66TEY]

Reply to #52

Yes, James - I see what you mean, that would be utopia - and more effective due to the low pressure aspect you highlight. 

But unfortunately this Caterham NACA duct only fits the RHS pointing backwards due to its curvature. 

Perhaps this whole idea will end in me asking Tillett if they could make one to fit the RHS (pointing forwards). 

But I suspect that would come at an eye watering price. 
 

[Nigel Riches]

In all my time working with commercial aviation, I have not seen a NACA duct with a flange around the periphery, all are mounted from underside, no boundary layer disruption.

This piece of carbon jewellery is possibly semi useful if installed below skin, but then looses the bling effect, but what do you want to achieve here, form over function?

Many years ago on the x flow motor, I made an airbox, and a remote intake with filter installed, not so much to lower temperatures, but reduce intake roar, 40DCOE's at max noise make plenty , and the intake for this was a hole on the bonnet top, previously used for a 2" SU carb to poke out, on the supercharged engine, and a aluminium box affair to draw air in, with K & N filter installed,  It was fitted with the bonnet scoop used for the old 1600 GT engine installation, this goes back to the early '80s, fitted back to front, all seemed to run ok, infact from what I read the area just before the screen, where the inlet was, is possibly positive pressure when making progress.  

Now having parked the x flow for a zetec, temps are more of a problem, and the continuing story of my ongoing non mobility situation are chewing into the summer time, but not on this day

Have fun  with your car, there is so much which can be made.  

[O.G.]

Chris,
I have watched the video of the "Loud American" extolling the benefits of fitting a backwards NACA duct on a NASCAR. I'm not at all convinced. You could probably cut any old hole in many places on a saloon car that runs at 150 - 200mph and find a lower pressure on the outside than inside. The backwards NACA duct could even have impeded airflow.

Nigel (54) is right, you do not see these ducts on aircraft with a lip/flange on the outside. The duct would fitted from within maintaining the sharp edge that is a part of how ot functions.

They are a triumph of style over function as used on most cars. 

I hope your project, whatever you end up doing, works out well.

O.G.

P.S. How do I increase the font size on this system. 
 

[Jonathan Kay]

"How do I increase the font size on this system. "

The size of the text in your posts, or how posts are displayed on your screen?

Thanks

Jonathan

[ScottR400D]

#54/55 you're both right but we've been through all that before. 

The OP is determined to fit the thing and that's up to him. It would be a lot easier (though not a particularly good idea either!) just to put a hole in the pedal box and a duct to where the standard vent is and it would probably work just about the same. 

 

[BenF]

Seeing as the flange on the duct looks a bit odd (from an engineering eye), would it not be better to trim the flange off, mount the duct to the pedal box and have it mating to the inner surface of the bonnet with some kind of seal?

This would look more like an engineering solution. However might be fiddly and prone to damage when fitting and removing the bonnet.

 

[ScottR400D]

That wouldn't make it worse but that product has other shortcomings as a NACA duct. If you wanted to fit a proper duct, in a suitable place for the right purpose, you'd have it properly fabricated and put on from the inside as you say. 
 

[BenF]

Agreed Scott.

There are some very good small engineering companies (like AS Pro Engineering) who will design components for you for specific purposes, but for a one-off it does not make sense - only makes sense if the cost is spread amongst a much larger number, e.g. 20 participants.

[simon_h]

As long as you remember these were done as a visual trim item to get a larger hole into an air box than the teardrop hole then they are fine. The flange is to make it easier to hide the cut edge and was originally for a bond flange. Someone later decided to fit some bent ally brackets and screws to hold it on. The naca detail was taken from how they should be but had to be tweaked to fit the bonnet shape. Don’t read too much into it being a naca duct proper 

[O.G.]

Jonathan,

Thanks for your reply. I've sent you this message as it would be a a distraction from NACA ducts.

I found that when I was typing on my i pad the font size is smaller than that in a post. I now see, when posted, that it comes up to the normal size so really I do not have a problem. 

Thanks anyway.

O.G.

[L66TEY]

Thank you all for your input. 

Appreciate the constructive comments amongst them 

In hindsight perhaps it would have been better if I had called the thread something along the lines of;

Fitting advise for visual trim carbon jewellery hole in bonnet 

As a side note my 2010 Caterham bonnet doesn't feature the teardrop holes. 

If this ends up being the end of this thread, then I feel compelled to finishing it with "it's been emotional" 

OP aka Chris

[BenF]

Chris, is the heat from the pedalbox not more from radiation from the exhaust?  Difficult to tell from the photos, it looks like you have some heat wrap on the primaries, but is it worth investigating having more insulation there.

I remember with my K-series with the exhaust on the other side, the soles of passengers's shoes would melt due to the heat from the exhaust but on the driver's side it was not too bad.

[L66TEY]

Reply to #64

Hi Ben,

Yes, I suspect you are right. 
The primaries are wrapped - albeit they need redoing as started to fray, so presently they are partially wrapped. 

Hence, I'll either rewrap them or look at ceramic coating as been advised that's even better than wrapping them.

Chris

[L66TEY]

Pics for interested parties

Chris 

[timb2117]

I had my primaries ceramic coated, quite cheap and they quoted - 25-30% heat reduction.

[L66TEY]

Hi Tim,
Whom did you use for your ceramic coating, sounds like you'd recommend them?
With thanks
Chris

[timb2117]

Sorry Chris would love to help but I'm in Australia, it was  a great family business, competition coatings, they only charged from memory $250 and were exceptional to deal with.

Awesome thread BTW (NACA ducts are a thing of beauty/ great purpose depending on your application!) and your handiwork is way neater than mine!

[L66TEY]

No worries Tim.

From the research this morning, in the UK Zircotec appear to be popular.

Thank you for kind words on my Project.

Chris