Bubble canopy / solar heating

Bill,

Tom Dixon had a simular situation iwith his old LS-6. He solved the
problems by placing a pack of large diameter soda straws in the tube.

Wayne
HP-14 "6F"
http://www.soaridaho.com/


"Bill Daniels" bildan@comcast-dot-net wrote in message
. ..

This discussion prompts a question.

The nose vent in my Nmbus 2C glider is very noisy - at least noiser than I
think it should be. With the vent closed, the glider is almost totally
silent. With the nose vent open, I have to turn up the radio volume.

The design is a ~2" hole in the very tip of the nose with a ~10" straight
pipe to which a corregated flexible tube (think scat tubing) takes the air
through an "S" turn to a vent door that is controlled by a pull knob on
the instrument panel. Nothing in the inlet tube or control door suggests
anything is making noise. The flex tubing with the circumferential ribs
is the lead suspect.

Is there a quiet replacement for the flex tube I could try? Maybe some
sort of muffler?

Bill Daniels


"Wayne Paul" wrote in message
...

This is from a sailplane pilots perspective. I fly under a very large
bubble canopy. Since I almost always fly on hot afternoons, fresh
cockpit air is a very big deal. I think you'll want to completely
replace the cockpit air several times a minute.

The advice to concentrate on the air exit is very sound. It's easy to
scoop in ram air but it has to eventually go back outside to achieve
cockpit ventilation. Try to think of an exit in a low pressure area.
When you think about it, this problem is just like cooling airflow for
the engine on a smaller scale.

Also worry about scooping up rain with the air. A bad vent design can
soak cockpit electronics in seconds. Water droplets have a harder time
turning tight corners than air so an elbow or two can act like a
separator.

Finally, worry about noise. It's amazing how much noise an air scoop
can make. A scoop behind the prop will transfer pressure pulses into
the cabin. Maybe think about an inlet scoop under the wing outside the
propller arc.

Bill Daniels

The ventilation in my HP-14 (http://tinyurl.com/yvrghx) is far from
optimum. It gets very warm on a hot summer day at lower altitudes.
However, with bit of altitude (10,000+) I am comfortable.

Your point on rain is well taken. This summer while scooting along under
a cumulus cloud I encountered. a bit of verga. It turned out to be a
combination of snow and hail. It came through the vent and hit me
directly in the face. I am sure it also was soaking the instruments.
The solution was to close the vent.

This is a bit off subject; however, while flying in an aircraft with a
bubble canopy you should take precautions to protect yourself from UV
radiation exposure.

Wayne
HP-14 "6F"
http://www.soaridaho.com/

"Ernest Christley" wrote in message
...
Wayne Paul wrote:

This is a bit off subject; however, while flying in an aircraft with a
bubble canopy you should take precautions to protect yourself from UV
radiation exposure.

UV treated plexiglass is only slightly more expensive than the
non-treated. Being a 'homebuilt' group, I would think that most of us
would handle the UV problem while building.

Ernest,

You are correct. Ray Poquette of ThermoTec (http://www.thermotecusa.com/)
makes great canopies. The UV blocking characteristics of his canopies are
shown at http://www.thermotecusa.com/UV%20Block%20Info.htm. These canopies
are more expensive then the standard clear canopies; however, well worth it.

My old HP-14 came with a clear canopy. When time comes for me to replace
it, I will definitely go with a gray UV canopy. (I only fly during
daylight.)

Wayne
HP-14 "6F"
http://www.soaridaho.com/

"Ernest Christley" wrote in message
...
Wayne Paul wrote:

This is a bit off subject; however, while flying in an aircraft with a
bubble canopy you should take precautions to protect yourself from UV
radiation exposure.

UV treated plexiglass is only slightly more expensive than the
non-treated. Being a 'homebuilt' group, I would think that most of us
would handle the UV problem while building.

Very good point, and I will make sure to use either anit-UV coated acrylic
or scratch resistant polycarbonate when I build.

I am no a doctor, and I do not play one on TV, but I have read that the skin
cancer risk from sunlight may be greatly exaggerated--at least for most of
us.

OTOH, having switched to polycarbonate eyeglasses, I can definitely saw that
the UV reduction is a *major* advantage. Reducing the UV level is a real
benefit to vision in bright daylight, with no discernable loss of night
vision, and might be usefull for heat reduction.

If anyone has a comparison between tinting and UV reduction with regard to
heating, the results would certainly be of interest.

Peter