NACA Ducts: Where Does the Water Go?

We're in the rainy season here in Florida and in heavy rain, water continues to be a problem for SPF P/2192. I've begun plugging holes and gaps in various places but it also appears that water is entering through the NACA ducts on the hood forward of the passenger and driver.

For example, I suspect that the duct in front of the driver is allowing water to enter into the dash and onto the steering rack. This can't be good for the electricals and would explain why, after driving through a rain shower, I have water running down onto my legs whenever I turn the wheel.

My question is simple: Does anyone know where the **** the ducts duct?

Thanks!

Kim
 

Randy V

Moderator-Admin
Staff member
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I don't have an SPF but they can't be too different from mine. The 2 outside ducts will simply dump the water on the front suspension - unless it's driven back by force where it will land on top of the chassis in front of the windshield base.
The center duct will just dump the water on the base of the windshield / spider area.

Until you cen get things sealed up properly - I might suggest the use of some "Duct" tape from the inside of the ducts to seal them off..
 
Did the original 40's have water traps? On this forum some owners have built their own, but I'm curious about the original set-up.

Dalton
 
In a pneumatic or steam curcuit, they create au U system (similar to the S bend on the sink / basin). This low point catches water which you can then plumb to a drain.

Hence the water is trapped at a low point which is lower than the outlet and large enought to cath water flow in and the air will rise back up and come into the cabin (without the water) provided the bottom of the U bend does not fill up - if so increase size of drain.

Easier to draw than write. ------I_____I------

Regards
Jason
 

Steve C

Steve
GT40s Supporter
Kim,

On my SPF MK11 the NACA L & R fender openings are connected to under fender ducts like the original cars (no center duct on the MK11 and I think if you have a center opening it is probably blanked off). Passengers front bulkhead has a faux connection that is blanked off but, the drivers side is open and feeds outside air into the A/C// heater plenum when the door AC recirc switch is set to the outside air setting.

Even with the switch set to recirc water can enter the A/C// heater plenum and leak into the car.

On my car with the front clip off I drilled drain holes in the under fender plenums at the low point to drain any water that enters. I also fabricated a mesh screen to prevent debris from entering the A/C system and installed it in the through bulkhead housing (see pic in the SPF section under P2125 on the road ect...

Steve P2125
 

Jack Houpe

GT40s Supporter
This is a little off the subject but I took the front off to put some of that pipe insulation on the area where the fender meets the tub where the brake and clutch reservoirs are, small rocks and water gets into that area where the fuel caps are located and this should cure the problem. But while I had the front of I decided to check the fresh air vent that comes off the NACA scoops on the front of the car using a shop vac set to blow not suction. When the light is lit for recalculation it is OPEN not closed. When you turn if off it goes to reticulation. So when your driving down the road and want to cool yourself with air that is already conditioned you are not getting it with the switch depressed. Its wired backwards or someone changed the vent system around at the factory on my car, would be a good thing to check. As far as water, I haven't driven in hard rain yet but will let you know when I do.
 
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Jack Houpe

GT40s Supporter
I am on my way to Michigan with my wife and car in tow, we hit a bad rain storm in Missouri and now know what your talking about with the water. I left my computer on the floor of the Gt40 and that was a mistake. Looks like someone turned the hose on in the car.
 

David Morton

Lifetime Supporter
NACA ducts are widely used in aeroplanes and often an associated device
is a heated "coalescer" to aid , guess what, - Coalescence. (the meeting of two water drops to make a larger one ) So it is technically possible to seperate the water and leave only the airflow with a slight decrease in pressure that the NACA duct generates. Equally, air can be extracted from the cabin with similar low pressure ducts so incoming air to replace it can be sourced without necessarily using the existing ducts on the front bodywork.
 

Steve C

Steve
GT40s Supporter
Jack,

Hope you see this post.

In order to correct the operation of your door Recirc Switch you need to reverse the leads to the recirc door servo. The servo can be found under the faux oil tank ...trace the lead from the servo to a two wire connector and reverse the blue and yellow wires.

Regards, Steve
 

Steve C

Steve
GT40s Supporter
John,

Assuming you have a later car with the left NACA duct fender cut out connected through the firewall to the HVAC system just take a vacume cleaner nozzel on push air and with the door switch lit see if air comes into the cabin...If it does your OK...If not reverse the leads to the recirc servo as discussed above.

Clear?

Steve
 

Keith

Moderator
Jack,



The servo can be found under the faux oil tank ...Regards, Steve

I thought these models were supposed to be faithful continuations of originals and so numbered? Therefore, presumably thus perhaps preserving some kind of extra value. In this context I am puzzled by the term "faux" anything on SPF "continuations".

Not trying to be pedantic, just trying to understand the whole "continuation" deal....
 
as a practical matter, Hi Tech made several mods to the cars for the available and expected market, which of course was not a race driver market. Better brakes, better electrical parts were also included for safety reasons. 40 years has past, so some changes are to be expected I suppose.
 
Keith,
The faux oil tank is a cover for the air conditioner evaporator. Yes they could omit the cover or to be more realistic the entire A/C system. You may get away without A/C in the U.K. In parts of the U.S. that would be foolhardy for road use. The SPF is still probably the most faithful replica, but obviously not 100% identical. LHD, cable shift, and brakes are differences. If you want to be pedantic MkII's should only have big block 427's with dry sumps and a T44 trans.
 
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