RV-8 Excess Cabin Pressure - Page 2

jthocker · #11 01-12-2010, 11:16 AM

And whichever moderator kindly does that, please post how you do that so us less than skilled moderators can do it in the future!

Mike S · #12 01-12-2010, 01:30 PM

Quote:

Originally Posted by jthocker

And whichever moderator kindly does that, please post how you do that so us less than skilled moderators can do it in the future!

Ditto on that, I tried, but no joy

db8 · #13 01-12-2010, 02:23 PM

Sorry about the size of the pictures. It has been a while since I have posted any pics, so I used a free program (Irfan View) to resize them to something more reasonable. Then I deleted the big pictures in the post, and resubmitted the smaller ones via Image Shack. I don't know if that helps you moderators or not? I think it does if you can put the picture on your computer through Image Shack, and then resize it, and then finally resubmit in the smaller size, it would probably work for you. The big question is if you can get the picture file on your computer to do this. I am not much of a computer person. Dave

Chino Tom · #14 01-12-2010, 04:15 PM

I'm very interested in this problem. I believe i have a related occurrence.
My canopy skirts are tight to the fuselage and i have foam to seal the
area aft of the rear seat. My passengers tell me that they can feel no
air blowing on the back of their necks. I believe that my the cabin pressure
builds up and then vents out. The result of this is a yaw bump. It also
happens only at lower altitutes and high (+ 140 KIAS) airspeeds. What is
also curious is that it does not occur or is greatly diminished when i have a
passenger. And lately i haven't noticed it at all. I installed an inspection plate
in the aft baggage floor (so as to be able to inspect the bellcrank without
removing the aft baggage shelf). I'm wondering if I remove the inspection
cover (if this works, I'll make it a vent), if it would have the same effect
as the two 1" holes? Both vent air to the aft fuselage, but mine would not
scavange air leaking in the back of the canopy. Comments very much
appreciated.

Ironflight · #15 01-12-2010, 04:34 PM

Quote:

Originally Posted by Chino Tom

I installed an inspection plate
in the aft baggage floor (so as to be able to inspect the bellcrank without
removing the aft baggage shelf). I'm wondering if I remove the inspection
cover (if this works, I'll make it a vent), if it would have the same effect
as the two 1" holes? Both vent air to the aft fuselage, but mine would not
scavange air leaking in the back of the canopy. Comments very much
appreciated.

I am going out to fly in a few minutes to check some new runway lighting at our field - I'll open up my battery inspection port before I go, and see if I notice any airflow difference - great idea Tom!

Paul

RV8TOR · #16 01-12-2010, 04:37 PM

I had a similar issue today but the cause seems to be the reverse of what is being discussed here. Cruising at 6,500 at 175 IAS I got the rear skirt canopy buzz, when I opened the cabin heat valve the buzz stopped. I could repeat this cause/effect by opening the heater valve. Appears that without a little cabin pressure to keep the skirt off of the fuse it wants to buzz.

Thoughts?

flickroll · #17 01-12-2010, 04:45 PM

Quote:

Originally Posted by Ironflight

I am going out to fly in a few minutes to check some new runway lighting at our field - I'll open up my battery inspection port before I go, and see if I notice any airflow difference - great idea Tom!

Paul

I'll be very interested to hear what you find out Paul. If having an opening into the rear fuselage helps, then the mod that DB8 did will be just the ticket. And, if you wanted the ability to close off air flow to the aft fuselage, a couple of Stein eyeballs on the upper baggage panel would be just the ticket.

Ironflight · #18 01-12-2010, 06:24 PM

Well guys, I went out and propped open my back seat several inches to allow airflow into the baggage area, then opened my hatch to my battery - humongous hole to the aft fuselage. I flew normal speeds and felt the same amount of air on my neck as always (I have a pretty well calibrated neck after 1,000 hours in the bird). I tried vents opened and vents closed, cabin heat on and off - felt no real difference.

As to buzz - I have never experienced it. I read about it before I flew my first flight, and that the answer was a good fit and a layer of felt, so I fit the skirt tight and glues on a layer of felt to the edge (about 3/4" wide". I have never had any noise associated with the skirt, so I may not have the same "test conditions" as those experiencing that affect.

Probably not what we wanted to hear - I'd love to solve the wind on the back of the neck problem, especially now that I am spending a little time in the back seat when Louise flies....

Paul

jriblet · #19 01-13-2010, 08:58 AM

I have the same buzz that folks seem to be talking about. Usually happens about 190 mph and happens with the vents closed. What was the result of cutting holes in the baggage bay aft wall?

Jeff Riblet
RV-8

flickroll · #20 01-13-2010, 05:42 PM

Quote:

Originally Posted by jriblet

I have the same buzz that folks seem to be talking about. Usually happens about 190 mph and happens with the vents closed.

And I get mine down low (denser air), and fast, with the vents open, never with the vents closed.....go figure.

When my -8 carries me back to 'ol Virginny late this week I'm gonna do a lot of experimenting when I get home and see if I can figure something out. Thanks for the data Paul, your test flight information is very valuable.