RV-8 "improved" ventilation

I decided to get more air into the aircraft this way.

2 spring loaded pins on the slider rails(1 each side) when engaged prevent the canopy from siding back.

High speed taxi(6000ft rwy) and lift off at 60 knots revealed no vibration, so up and away around the pattern.

70 knots on crosswind, no vibration

80 knots on downwind, no vibration

Downwind, canopy can be closed, canopy can be opened at 80 knots

95 degree day, short final with the canopy open " My name is Jose Jimenez" (Al Shepard from The Right Stuff) I say to myself.

That flight was on Friday.

Saturday after being released from our Airport "Hot Standby Duty", First Officer Gene Seiter and I traded one 8 (DC-8) for another (RV-8).

Gene's official duty was to take notes, watch for traffic, and assess the integrity of the canopy at the rear as we explored higher speeds.

Gene has been a test pilot before also, as he has built and flown a Fisher Horizon. (An RV is in his future I believe.)

Our results so far:

110 knots with the canopy open-no adverse vibration, higher ambient noise but not enough to break the normal squelch on the intercom, volume on the radio needed to be increased slightly. Canopy, once started forward closes easily. Ventilation breezy but not a hurricane. No detectable vibration or "lifting" at the aft canopy track or slider block.

100 knots, Gene flying while I opened the canopy, using my left hand to operate the handle I could easily get the canopy open, but due to hand, wrist,elbow, canopy handle geometry it was tough to get the canopy back to the "6 inch stop" so I used my right hand to get it aft to the stop.
Gene said he detected no change in pitch or elevator forces while I opened the canopy.

I will continue to explore further but probably not much faster because
ventilation is good in the 8 above 100 knots.

Nice!

How about some pics of the slider rail mods you made?

Also - I suppose now you'll have to placard the aircraft for max Vco - Velocity Canopy Open....

Canopy stop

Greg

The canopy stops are from Mcmaster-Carr part #8478A3

Plate mount, hand retractable spring plunger .24" nose diameter 1.95-5# end force.

Standard Van's #8 flush screws with the heads inside the rails, rail slightly countersunk, nuts in the cockpit. (Some might say that was Gene and I).

http://www.mcmaster.com/

Very Cool!

I have always wanted to see someone (else!) do a careful flight test build-up on canopy open Ops Jon, and it looks like you guys are working it slowly! I really miss flying my old Grumman with the canopy cracked open, and it would be cool to know that the -8 can do it at slow speeds. I'd be looking for rear skirt corner "buzz" as the speed increases, as well as any signs at all of the canopy lifting in the rear (I have been told it is a low pressure zone, and I'd be a little nervous about the integrity of the Nylon slider block. Perhaps an aluminum backup plate in the same shape of the block, sandwiching it as a safety....just in case?

Good luck, and keep us informed!

Paul

slider block

Paul

Those were the exact issues I had concerns about.
Gene is about 6'3" and had a hard time turning around to observe the slider block. I wanted him to push up on the canopy to see if he could detect the "play" between the rail and the block, he can't recall if he could feel that play, but it was his impression that the canopy was pushing down and not lifting. In any case, the skirts were rock solid, and the faster we went the more pressure to close was felt.

I'll keep you informed.

Regards

Jon

Update

The weather here in Cincinnati wasn't cooperating too well this AM, but it was good enough for a trip around the pattern.

Fellow repeat offender Terry McCann(RV7A, soon to fly RV8)volunteered to assess the aft canopy pressure situation.

Flying in the pattern between 75-105 knots Terry was able to turn around and look at the aft slider block.

What he found, was that the block was pushing down on the rail and was actually depressing the turtledeck skin about a quarter of an inch.

Pushing up on the canopy to relieve the pressure on the rail/skin was very difficult. The downward pressure seemed to increase with speed.

At the same time pushing up on the canopy at the front rollers was easy and you could feel the "play" between the roller and track.

Again the side skirts were solid as a rock.

Back on the ground we found that the only solid place for the aft slider block is directly over a bulkhead.

So the choice will be to fly with the canopy fully closed or half way open.

Or rivet in an aux bulkhead somewhere in between the rear seat bulkhead and the aft baggage bulkhead.

I'm now planning to buy the 2 top piece's for the (807?)bulkhead, let them overlap a little more, and rivet them to the turtledeck skin and to the upper longerons directly underneath the slider block.

Right now I have the stops positioned 7 inches aft of the roll bar flange on the canopy deck.
This yields a 5 1/4" canopy opening, good for ventilation and throwing the empty beer cans out!

This is great testing guys!

jthocker said:

...............good for ventilation and throwing the empty beer cans out!

Click to expand...

Careful, they'd probably hit the fin. A friend of mine threw his McDonalds bag out of his airplane and it was wrapped around the fin when he landed.

Regards,

No canopy testing today.
Stall tests, climb rate tests, descent rate tests and finally lunch and formation practice with "Grease", "Joker", and "Beanie".

On the canopy front though, instead of an extra bulkhead I was thinking that maybe a rib that runs between the bulkheads under the slider rail like the 6,7,and 9 sliders do. Or maybe 2, sandwiching the latch block assembly.

This method would allow testing a range of open positions that could allow "egress confidence" for the pilot or.........a watermellon?

Wadda you guys nuts, or just sitting on big ones? I would think when it lets go, (front rising, back pushing down) its going to hit the vertical. Do you think it will survive the strike?

What happens when you step on a rudder, as in uncordinated flight? What kind of stress is imposed on the rails, and F 816's? How much time till something fails? Have you consulted an aeronautical engineer? Too many questions, I need a beer. But I do think its kind of cool you can litter your way accross the country.

Wow, better you guys than me. Good luck!!! I mean it.

Calvin
Actually the front was NOT rising at all. Thats what we were checking when we pushed up on the front and were able to confirm the "play" between the top of the roller and the guide.

The goal of the "NO YOU CAN'T or SHOUDN'T DO THAT POLICE" is to take all the fun and adventure out of the world.

It is my mission in life to defeat them!!!!

Best regards

Jon,

I hope you do defeat them, I still say you have big ones!!!

Good luck

Calvin

Not big ones, just alot of experience in various RV models.

By the way, the first trip around the pattern with the canopy open I was carefull to stay coordinated. Subsequent trips I did induce some yaw to see the effect. The only detectable change was different ambient noise from the slipstream.

I've ordered an 807B bulkhead from Vans and should have waited because I would like to now put a rib between that new bulkhead and the 808 bulkhead.

Anyone know the part # for a RV7 slider rib that runs under the slider rail between the baggage bulkhead and the next one?

Thanks

Has anyone flown a RV 8 with the canopy removed?

The the thought is definitely crossing my mind!

update

The new 807B bulkhead arrived from Van's.
It was cut in half, and the upper flanges removed. I marked where the slider block was sitting with the canopy against the spring plungers(canopy 5-6 inches open). Positioned the bulkhead half inside to adjust(trim) the new radius/contour. Then, having an extra 803CPP instument panel flange laying around, I layed a rivet spacing fan on it and drilled it to match the existing rivet spacing on adjoining bulkheads. This was next positioned inside the baggage compartment at about 7" aft of the top of the 807 bulkhead and then back drilled so that it was perpendicular to the top longeron and parallel to the 808 bulkhead. Next the new 807B bulkhead halves were positioned against the 803CPP flange and using the existing prepunched holes as a guide the 807B was back drilled, clecoing as I went. While I was riveting the assembly together prior to installation, Sam Marlow(RV10 N540MR builder) fabricated 2 gussets to tie the bottom of the bulkhead to the longerons.
The new bulkhead was riveted in place, the gussets were popped(LP4-3) in place, the canopy reinstalled and we were ready for a test flight.

A pic of the new bulkhead.




And it's location.




Test flight consisted of takeoff with canopy open, and climb out at 80 knots.

Canopy began closing as the plane accelerated.

Canopy will no longer remain open in level flight. It will stay open on climbout with the plane pitched up, but will start to close as speed is increased.
It will not remain open on short final with the plane pitched down.

Sam verified from the back seat that the new bulkhead was doing it's job and preventing skin/rail deflection. Sam also noted that all the air that was entering the cockpit was coming from the rear and moving fwd.

So it appears that some of the force that was trying to close the canopy before the new bulkhead was being stolen by the skin/rail deflection.
The new bulkhead now allows all that force to act upon the canopy in a fwd. direction.
Sam also verified that the canopy in no case was lifing at the front rollers.

Now to see how to keep the canopy open.

Update

In an effort to keep the canopy open, I have been experimenting with stops.
First I made one like the one that is depicted on the canopy plans for the mid stop. A thin piece of uhmw plastic about 3/8" square by 1/16" thick. Placed in the roller track so that after the roller goes up and over it the roller gets trapped between the stop and the spring plunger stop. The tricky part is finding the proper thickness for the plastic. Too thick and the roller won't go over or takes too much force to roll up and over. Too thin and the closing force overcomes the stop and closes the canopy.
After a couple of tries I have come up with this.
With the canopy open about 6 inches and against the spring plunger stops, I drilled a #28 hole through the canopy rail about 1/4 inch in front of the roller.
I inserted a #6 truss head screw in the hole along with a nut and washer and tightened it down.
Now with a slight amount of effort the canopy can be rolled back over the stop and against the spring plunger.

Flight testing subsequently revealed:
Takeoff with canopy open, canopy stayed put until I closed it at 100 knots on climb out.
Level flight at 100 knots canopy opened and now remains open.
Gradually increased speed to see at what speed the canopy would close.
At 113 knots canopy overcame the screw/stop and closed.
On final approach with the plane pitched down canopy remained open at 75-80 knots.

Further observations included yawing the aircraft with nearly full rudder deflection while flying level. The fwd. canopy frame seems to be in "the lee" of the windscreen during slipping/skidding flight as placing fingers outside and along the plexiglass all around the perimiter revealed no airflow against my fingers.

Thus my canopy adventures/misadventures are concluded and I can now participate in "flour bombing" contests.

Next project is a homemade smoke system.

pierre smith said:

Careful, they'd probably hit the fin. A friend of mine threw his McDonalds bag out of his airplane and it was wrapped around the fin when he landed.

Regards,

Click to expand...

A friend tossed an apple core out the little side window on his Arrow. Sure enough, hit caught on the gear pitot tube sticking out of the left side and the gear dropped. He had to land and remove what was left of his apple.

Bump.......

Anybody tried anymore of this open canopy work?

Jim

Good on you Jon...

JT;
I saw this post thru your video. I know it's a bumpitty bump bump BUMP, but I was wondering if anyone flew without the canopy at all, or made an open cockpit skirt assembly? (tu-holer)
And any continuing info on the sider being open in flight?
Every time I get a wondering eye for another plane, something wonderful is discovered in RV-8 land!!

There is a picture floating around of a guy down in Texas flying without the canopy. Maybe someone on here still has the picture.

So easy......

RV-8 Open Canopy

canopy stop plunger

It seems the McMaster Carr plunger is pot metal two broken so far looking for a better stop. Flour bombing is fun in the 8.

Your experience pretty much aligns with other sliding canopy a/c I've seen.

A Swift with the 'Nagel' sliding canopy will open about 4" & stop if unlatched in flight. You can't push it any farther aft during normal flight.

Thorp T-18's actually have the cabin fresh air vent cut into the base of the aft end of the canopy. When opened in flight, the breeze will part your hair in the back & try to blow your cap to the instrument panel. John Thorp was a pretty smart guy...

Apparently, pressure actually goes up on the aft end of an airfoil shape when it's moving through the air.

Charlie