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Ventilating an RV-3 ?

Ironflight

Ironflight

VAF Moderator / Line Boy
Mentor
Well, we?re moving right along on the RV-3 fuselage, and before we know it, we?re going to be working on the canopy, skirt etc. Most of the cockpit accoutrements have been designed and roughed in- finishing takes a lot longer of course. Before I take up all the minimally available space, we need to give some serious thought to cabin ventilation ? we do live in Texas, after all?.

The instructions are, of course, a bit vague, suggesting small NACA scoops in the canopy skirt. That sound s like a decent option, and I saw a neat way to do it on a blue metal race plane in the antique area at Oshkosh this year. Not simple, but neat, and since we?ll be scratch-building a glass skirt, it might not be that much more work.

I have looked at a number of RV-4?s that put NACA scoops below the cheeks on the forward fuselage, but on the -3, that looks to not be an option due to interference with the rudder pedals. I?ve also seen some folks take ventilation air from the back of the engine baffles, and while I do take my heater air from that location, I have a stainless firewall box to cut that off in case of an engine fire. I suppose I could do the same thing with the cooling air, but I?d rather not ? I?d like the ventilation air to be from somewhere other than forward of the firewall. I like the under-wing vent on the -8, but we have QB wings, and that might be a tough mod?(not sure how to get the air from under the seat to someplace useful either!)

So, now that I?ve said what I don?t want to do?. I?ll see if there are any old-timers lurking here with good ideas or remembrances of what has been done before ? or young guys with other ideas I can examine. Right now, I have a place in the top of the radio stack (between the pilot?s legs) that could support a couple of eyeball vents. Either that, or a glove box?..:eek:

Paul
 
Hi Paul.

We used to own a navion that had vents in the wing roots, centered on what was probably the stagnation point of ram air on the leading edge. They were extremely effective.

I've considered modifying one or both of the wing root fairings for maybe a 0.75" SCAT tube to another air vent in my RV-8.

Is there room for this in the -3? This is very high pressure air, and you don't need larger diameter tubing at rv speeds. Cessnas and cirruses use a similar location for air vents--better recovery than the submerged NACA vents.

The only issue I ever had with these was that they were exactly the spot where the "bow wave" from the nose wheel would impact if you landed on a runway with standing water. They fed an eyeball vent on the floor between your knees, and a puddle would send a geyser of water into the cabin that would hit the roof and drench you if you didn't know to close the vents first. Go ahead, ask me how I know :D
 
Paul,
I read an article on Paul Lipps' Lancair 235 over the weekend, and he has a vent opening on top of the fuselage, right in the middle of the canopy skirt at the front of the windscreen. This is a high pressure area, and he reports good flow from this position. Would this position work for the 3?

And I'm sure you've already thought of this, but don't forget to give the air some way to get out. A vent in the seat back panel perhaps?
 
What Moose said!

My buddy's -4 has an air leak at the base of the windshield fairing and we've tried all sorts of approaches to stop the air....it really flows well there,

Best,
 
RV-3 Vent

Dear Paul:

Order the following parts from Van's:

F-1086 VENT BRACKET $6.30
F-1087 VENT SLIDE $5.15
F-1092 VENT DOOR DOUBLER $1.80
F-1093 VENT DOOR $1.90

These parts make up the RV-10 rear seat vent. I Installed them on the RV-10 as well as on an RV-8. They work great. If you want a fancier latch. Alex D. has them on his web site.

The build instructions are on page 29-19 of the RV-10 plans. If you do not have access e-mail me at dav1111 at suddenlink dot net and I will send them to you.
 
dav1111 said:
Dear Paul:

Order the following parts from Van's:

F-1086 VENT BRACKET $6.30
F-1087 VENT SLIDE $5.15
F-1092 VENT DOOR DOUBLER $1.80
F-1093 VENT DOOR $1.90

These parts make up the RV-10 rear seat vent. I Installed them on the RV-10 as well as on an RV-8. They work great. If you want a fancier latch. Alex D. has them on his web site.

The build instructions are on page 29-19 of the RV-10 plans. If you do not have access e-mail me at dav1111 at suddenlink dot net and I will send them to you.
Click to expand...


Russ,
Do you have a picture of what this looks like?
Thanks in advance.
 
I put an RV-10 vent under each cheek (the plane's, not mine), and the new owner reports gale force winds when fully open. There's no ducting, but I think they do need some type of cable so they can be adjusted in flight.
 
RVator

Paul,
I did a search on "ventilation" in the 27 years of the RV-ator and foud a few hits. Start on page 176.
 
Vents

Hi Paul

My-4 has the rear seat vent pick under the left wing and the front seat vent is on the back of the baffles. the underwing location is far better.
 
Windshield Inlet

Michael White said:
Paul,
I read an article on Paul Lipps' Lancair 235 over the weekend, and he has a vent opening on top of the fuselage, right in the middle of the canopy skirt at the front of the windscreen. This is a high pressure area, and he reports good flow from this position. Would this position work for the 3?

And I'm sure you've already thought of this, but don't forget to give the air some way to get out. A vent in the seat back panel perhaps?
Click to expand...

My early RV-3 had a hole (2" wide by 1/2" high) cut through the windshield at the midline of the lower fairing where it joins the fuselage (as Paul describes above), and a shaped filler plug, sliding fore and aft on the top of the glare shield was used to open/close it and diffuse the flow somewhat. It worked really well and I plan to duplicate it on my current project.

As previously mentioned, getting the air out can be more problematic, and some commercial aircraft use a rear-facing outlet low on the fuselage side above the flap/ fuselage intersection. I'm going an alternate route and plan on using ventilation openings in the upper seatback/headrest area to increase flow into the aft fuselage, and then fit a screen mesh opening in the upper portion of the baggage bulkhead along with inspection covers with louvers on each side of the elevator horn to finally assist the air in exiting.
 
Lots of interesting ideas folks - it's great to capture them for the archives, as well as current use!

Exit air is, indeed, an important consideration, and I'm going to have to think about that as well. I do like the wing root idea, but would have to figure out the routing. It turns out that the "really cool" vents I saw at OSH are indeed available from Van's! A circular hole with a disk in it - you twist a knob to open the disk and point the airflow.

Paul
 
Hi Paul,

Those twist knob vents you referred to are made by Larry Vetterman. Supposed to work great. We have the NACA vents on the side skirts of the canopy per the RV-4 plans and they dont work. The rear one actually blows air out instead of in.
We are thinking of trying the Paul Lipps vent mod (as Moose mentioned) on our flying RV-4 and are putting the NACA vent in the left wing on the new RV-4.
 
Paul,

I struggled with the whole cockpit ventilation thing while building for a long time too. The wing root solution, which is very effective on the RV-8, won't work on a -3 because there's no room under the seat to bring the 2" vent tube in, and even if you could there's not a good place I could find to locate an eyeball vent. Any sort of vent you put below the cheeks on the side of the fuse will likely hit your legs at some point so be careful there. Those not building a -3 need to keep in mind that EVERYTHING is smaller, it's a bit like a 3/4 scale RV really -- what works in a normal RV won't necessarily work in a -3.

Personally, I wanted to avoid any sort of protruding vent aparatus such as the RV-10 rear seat thing or the Vetterman vents because of drag. I know, it's probably not even measurable, but that sort of thing just looks draggy. I was trying to keep the look of the plane clean and unemcumbered too...
DSC_2016_900.jpg


In the end I used the back engine baffle method (info on the Cockpit page and more on the FWF page) routed to an aluminum eyeball in my center console, pic here. It worked ok but did warm the air just slightly. I never did get around to putting an extention on that to take the air from near the inlet, it worked adequately the way it was.

Doing it again I might be tempted to use the Vetterman vents, maybe one down below the cheeks on one side to ventilate the legs and area below the panel, and another up in the canopy skirt for the face and torso. If you don't insulate your firewall you will feel some heat radiation from it so some fresh air down there would help, then of course we all like some fresh air on our faces and torso to make us feel cooler when its hot out.

This makes me miss my RV-3!!
 
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Vent

A 2 inch by 2 inch works great on my -3. It hinges at the back and pops open or closed by hand. Moose... Did you mean to say seat bottom? ;) I'd put one on each side of the canopy, it actively scoops air in and is flush when closed, I'll take pics if you want.
 
Thanks again for the additional inputs. I think that for now, I am going to try the Vetterman vents - they really do look nicely made - and keep a NACA scoop just forward of the canopy with eyeball vents above the radio stack in my hip pocket. I like where you had your vents Randy - I look at your pictures FREQUENTLY - but since my avionics stack is taller, I don't have the room between the fuel selector and bottom of the transponder that you did (since I want to see the top of the radio stack. So for now, I think Louise will get a glove box, and if we add additional venting, the eyeballs could go there.

Oh Randy...my goal with all these RV-3 posts is to make you build another one you know....;)
 
Ironflight said:
Oh Randy...my goal with all these RV-3 posts is to make you build another one you know....;)
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It's crossed my mind. I seem to get the itch to build something every few months or so, I've almost started one of our cubs twice now just to pursue some mods I've been thinking about.
 
brianwallis said:
A 2 inch by 2 inch works great on my -3. It hinges at the back and pops open or closed by hand. Moose... Did you mean to say seat bottom? ;) I'd put one on each side of the canopy, it actively scoops air in and is flush when closed, I'll take pics if you want.
Click to expand...

Nope, I meant seat back. More accurately, the bulkhead surrounding the seat back. Into the baggae area , through another vent into the rear fuselage. From there, out below/behind the wing or out the rear at the HS. Like some of the guys were talking about recently for their RV-8's in another thread.
 
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