REFLECTOR: Rain and top fuselage naca

Tue Oct 11 09:55:30 CDT 2011

Kevin,

There should be a drain going out the bottom of the aircraft that connects
to the fresh air NACA on the top of the fuselage so that water can get out
while sitting on the ground or in flight.  The two large NACA's will allow
water to enter down the engine compartment.  You should have a 1/4" drain
hole at the low point of the bottom cowling up against the flange and
firewall.  To prevent water from entering the cabin you need to do several
things.  First, in the engine compartment you need to make sure that your
wire ducts on the bottom of the fuselage and sealed with an expansion foam
so that the water cannot enter the duct.  Otherwise you will end up with a
floor of water in the aircraft.  The water will also enter the cowling exit
while sitting on the ramp even with the cover on it.  Secondly, you need to
seal the canard cover with either 3M tape or silicone to prevent water from
entering the front.  Thirdly, the elevator torque tubes can let some water
in as it runs down the side of the fuselage.  You can use orange silicone
baffling material to make a seal.  This also will help in colder weather to
seal the cabin.

If you have a fresh air vent in the front of the fuselage on the co-pilot
side of the nose, this can also let water in while flying.

Since this can be an issue for the aircraft, it is suggested to drill a 1/4"
hole on the floor of the aircraft just in front of the rear seats.  This is
about the low point of the aircraft and will allow any water to drain if it
gets inside of your aircraft.  Don't forget to also drill a 1/8" hole in
your strake pockets that the door closes off as well as your winglet
bottoms.

Best,

John

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Tuesday, October 11, 2011 10:07 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Rain and top fuselage naca

Kevin,

I only have two large NACA's that connect to the engine plenum.  I don't
know about a small third scoop.  I've seen pictures of it but don't know
what its for.

Scott

-------- Original Message --------
Subject: Re: REFLECTOR: Rain and top fuselage naca
From: Kevin Baker <flykb at verizon.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Date: 10/10/2011 06:49 PM

> Thanks Scott
> What about the small naca scoop that goes into the cabin?
> Did water drain into the cabin or fill up the back of the channel.
> ??
>
> Thanks
> Kevin
>
> .
>
> On Oct 10, 2011, at 19:33, Scott Derrick<scott at tnstaafl.net>  wrote:
>
>> Sitting or flying the rain enters the plenum and drains down through the
engine.
>>
>> In flight I imagine some of the water exits out the rear openings.
>>
>> I do have multiple drain holes in the lower cowling at the low points and
a drain hole in the ram scoop/filter housing which is below the
fuselage/rear cowling.
>>
>> Interesting story about not having a drain hole in a low mounted intake
scoop.  I was washing my plane last summer.  It was about 6pm and the
airport was deserted. Finished washing and wiped it down with a shammey, got
in and was going to taxi it back to the hanger. I was pretty aggressive in
spraying it down with water and rinsing as it was really filthy.
>>
>> I gave it a 3+(probably 5 I was distracted) second burst on the fuel pump
for priming and hit the starter. It coughed but didn't start?   I gave it
another shot and hit the starter, it made an odd muffled kind of sound and
didn't start?  Hmmm... Not like it at all.  I bent out the door and down to
look back and under saw a fluid dripping from the drain holes in the cowl
which seemed OK, I had just sprayed it with water.
>>
>> I gave it another short burst of fuel and hit the starter, still nothing.
>>
>> Got out and walked back to the rear and bent down to see if that was
water slowley dripping from a drain hole, I rested my hand on the intake ram
scoop below the fuselage. IT WAS REALLY HOT!
>>
>> I thought, SHIT THATS HOT! I touched it again to convince my unbelieving
self that it really was hot, IT WAS!
>>
>> I ran back to the front and opened the throttle, idle cutoff on mixture
and held the starter on for about 30 seconds.  It actually coughed a few
times at about the 15 second mark and seemed like it wanted to start.
>>
>> I ran back to the rear and the intake was a bit cooler.  In a minute it
was definitely cooling off. I removed the rear part of the scoop and it was
partially black in side as was the servo intake tube. The filter in the
front part of the scoop was partially melted. NOthing damaged but the filter
thank god.
>>
>> Without a drain hole the rear part of the scoop filled up with I don't
know how much water, then when I gave it a shot of fuel(probably too much)
some ran down and probably floated on top of the water.  That fuel ignited
somehow, maybe a back fire!
>>
>> I now have a 3/16 drain hole in the lower part of the scoop. I had not
put one in because I was trying to seal it really tight for ram pressure in
flight and sucking dust during taxi.  Now I sacrifice a minute amount of
pressure during flight and probably don't get but a few specks of dust
through that little hole during taxi...
>>
>> live and learn..
>>
>> Scott
>> -------- Original Message --------
>> Subject: REFLECTOR: Rain and top fuselage naca
>> From: Kevin Baker<flykb at verizon.net>
>> To: Velocity Aircraft Owners and Builders list<reflector at tvbf.org>
>> Date: 10/10/2011 04:55 PM
>>
>>> Hi all
>>> As it's raining here in Dallas, finally.
>>> I was wondering about the naca scoops on top of the fuselage and
rain/water getting into them.
>>> More importantly the small center air scoop.
>>> Are folks putting in water drains for rain or wash water to drain from?
Or ?
>>>
>>> Thanks
>>> Kevin Baker
>>>
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>>
>> --
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