RV-3: Phase 1 Tweaks

[Ironflight]

Well here we sit with 39.0 hours on the RV-3?s clock and the rain coming down in a constant drizzle?.and it?s been low, or foggy, or rainy (or all three as a bonus!) since last Tuesday! Fortunately, we have essentially completed what I consider the legally ?essential? parts of Phase 1 (envelope definition and expansion, climb/glide/cruise performance, aerobatic maneuvers, and normal flight parameter definitions), so when we can get another hour in, we?ll be able to sign it off and start some cross-country work. Then of course, we?ll continue refining our performance tables and doing extensive avionics testing and practice before committing to things like IFR flight.


However, a few notes on things we?ve had to tweak during Phase 1 might interest those who have followed the RV-3 build?.

1) We had a heck of a time keeping the beautiful Aero LED Pulsars (Nav and Strobe) going. This was quite a mystery ? they could be dismounted from the bayonets quickly, and with a little wire wiggling, they?d work again. Then a flight or two later, they?d be dead. More wire wiggly and connector examination. They were installed with the supplied Molex block connectors. When I got serious about troubleshooting them that turned out to be the problem ? Dean was very helpful, and admitted that they really weren?t very high quality connectors ? they are working on something better. In the meantime, I replaced them with D-Sub pins and sockets (we?re talking real low current), and they?ve been rock solid ever since.

2) The right brake went mushy a few times. Back during the inspection, our DAR?s boss (Ann Asberry) noted a drip of red fluid on the tip of the bleeder, so I had tightened it up. I bled them a couple of additional times, and always made sure the bleeder was tight ? but it kept leaking. I finally took the broader view, and realized that the fitting that the bleeder valve screws in to was a bit loose ? it is an NPT fitting, and needed a little additional encouragement to stop seeping.

3) A little wheel pant damage ? we must have had a rock kick up between the left tire and pant, and it took a little chunk out of the rear corner of the tire opening, and cracked the pant about an inch from the opening for several inches. No problem ? this took about ten minutes of work, and a couple of hours of cure time ? then it was back to flying. Just glad it isn?t painted yet! We might open up the clearances another quarter inch.

4) Comm 1 seemed to have a limited transmit range, and it wasn?t receiving AWOS?s very well either. Gee?.you should be able to talk to the moon with a GNS 430W. Of course, it works a lot better if the BNC connector is properly seated on the antenna?..that just took a floor panel pull to chase down.

5) We have had a little cracking of the inboard lower skin of the left flap ? the little piece that sticks out to fair into the fuselage. This is very thin skin on the RV-3, and is essentially unsupported. It started cracking at a rivet in the front, and right at the bend (of course!) at the trailing edge. We stopped drilled both, and had no further propagation ? but we?ll do a doubler or a different configuration before paint.

6) We had to replace the G3X ADAHRS right after first flight ? Garmin was VERY fast in getting this out to us. We had a pretty early serial number, and the problem was just with the Air Data board ? they suspected a connector inside the box, and we haven?t had a single bad hit of data with the new box.

7) The rear-most rivet that holds the canopy hinge to the fuselage popped - the head came right off. I attributed this to having the safety cable a little long, and as the canopy opened past vertical, it induced a ?camming? force that pulled up on the hinge. Shortening the cable help a lot. At some point, we?re going to figure out the geometry for a strut.

8) The canopy latch was getting stiff, and I realized that the shaft was sliding ?inboard? through the skirt hole, binding the pushrods. I added a nylon spacer on the shaft between the skirt and the outside handle, holding the handle in position ? it?s much better now (but still stiff!)

9) Left fuel gauge went ?inop? after a few hours. Seems to be an intermittent connection inside the tank ? Dang! Fortunately, we aren?t painted yet, so when we get some downtime after Phase 1, we?ll pull the tank and replace the sender ? new one is on hand already.

10) I am a bit worried about the ventilation ? the round skirt vents we installed are gorgeous, but seem to be embedded in a bad flow area ? they produce mostly noise, and little airflow. We have a set of RV-10 back-seat vents on order that we might install in the fuselage below the longeron ? one or both of these should do the trick.

Overall, the test program has been outstanding! I have done most of the envelope work, and Louise has been working through performance data collection ? which will continue into Phase 2. I have been amazed at how well thigns like gear alignment and trim have worked out - even with a kit this basic, it is hard to screw it up enough to matter. Random errors do seem to cancel out....

The little tweaks we?ve mentioned above have not diminished our enjoyment and satisfaction one bit ? this is without a doubt, a pilot?s airplane!


Paul

[fatherson]

Thanks for adding even further to all the great RV-3B documentation you've already created, Paul. Based on your writeups as well as Randy's and Rob's, I was just about certain I was going to move forward with starting my own -3B project before the price increase last Weds.

However, I sat in the company -8A in Aurora on Monday and now I have second thoughts. I'm not huge but not particularly small either. I liked the fit of the -8's front seat. I've never sat in a -3, but I've compared the dimensions in the two plane's plans. I'm just anxious about whether the -3 will feel too small for me.

Since you have both, any thoughts?

--
Stephen

[Ironflight]

Originally Posted by fatherson

However, I sat in the company -8A in Aurora on Monday and now I have second thoughts. I'm not huge but not particularly small either. I liked the fit of the -8's front seat. I've never sat in a -3, but I've compared the dimensions in the two plane's plans. I'm just anxious about whether the -3 will feel too small for me.

Since you have both, any thoughts?

--
Stephen

You have to build the airplane that fits your mission, and the -3 and -8 fill different missions, depending on if you fly solo or with a passenger!

As for fit - the -3 fits like a glove - we built it that way. We could have made more room if we went with "stock" interior stuff, but we built a little fighter cockpit. the -8 is definitely roomy. I'm 5'9" and 165.....I saw a picture recently of what appeared to be a much larger fellow with his new (to him) RV-3. you need to sit in one to see how it would feel.

Paul

[David Paule]

On ventilation - would it make sense to install a vent on the fiberglass canopy fairing right behind the forward frame bow? In some photos, it looks like one of Van's NACA scoops would fit right there, especially on the starboard side. The fiberglass to fiberglass bond would be easy and secure.

Perhaps an eyeball outlet could be fitted directly to the inlet. It might be high enough to get out of any disturbed air flow from the cheeks, and would certainly be direct.

It might also be instructive to tuft the area. I'd be very interested in that.

Wheel pants - what sort of clearances are you running at the moment?

Your reports are very encouraging, keep 'em up!

Dave
-3B empennage, wing and fuselage kits on order, expected in April.

[Vac]

Paul,

Data point: The forward fuselage aft of the firewall and below the cheeks is a great high pressure area on the -4 (just outboard of the footwells). We have silver dollar panels (Van's p/n CA LV-3) installed on each side and they work very well. We used a simple push/pull cable acutuator to open and close them. Ventilates the cockpit from the bottom up and works really well in the summer and in the winter as well when you want to mix some fresh air with heated air. These panels can partially open or open backwards to pull air from the cockpit.

Cheers,

Vac

[Ironflight]

Originally Posted by David Paule

On ventilation - would it make sense to install a vent on the fiberglass canopy fairing right behind the forward frame bow? In some photos, it looks like one of Van's NACA scoops would fit right there, especially on the starboard side. The fiberglass to fiberglass bond would be easy and secure.

Perhaps an eyeball outlet could be fitted directly to the inlet. It might be high enough to get out of any disturbed air flow from the cheeks, and would certainly be direct.

It might also be instructive to tuft the area. I'd be very interested in that.

Wheel pants - what sort of clearances are you running at the moment?

On the ventilation, the canopy skirt behind the forward bow (aft of the instrument panel is basically where we have the LV-3 vents. Consultation with my favorite aerodynamacist (not me) confirms that is a pretty bad area to try and get inlet flow, unfortunately.

Wheel pant clearance right now is the width of Louise's thumb joint. We will probably open it up to the width of MY thumb joint - which has worked well on the -8 and the -6. Like just about everyone, we are always trying for as little a gap as necessary, and you always guess too small for clearances....

Originally Posted by Vac

Paul,

Data point: The forward fuselage aft of the firewall and below the cheeks is a great high pressure area on the -4 (just outboard of the footwells). We have silver dollar panels (Van's p/n CA LV-3) installed on each side and they work very well. We used a simple push/pull cable acutuator to open and close them. Ventilates the cockpit from the bottom up and works really well in the summer and in the winter as well when you want to mix some fresh air with heated air. These panels can partially open or open backwards to pull air from the cockpit.

Cheers,

Vac

Thanks Vac - unfortunately, the -3 doesn't have quite as much space down in the leg wells (by the rudder pedals) as the -4. We were first going to copy some great -4 ideas we had, and were disappointed when they didn't fit. I'm thinking of putting vents down in that same area that you mention (under the cheek cowls) but a little further aft. I haven't cut any holes yet though - so we'll see....

Paul

[pierre smith]

How would you rate it as an aerobatic mount? Can you do crisp 4 point rolls in her? 8 points maybe?

If you've flown a Pitts, how does Jr. compare in control response and roll rate?

Thanks,

[Ironflight]

Originally Posted by pierre smith

How would you rate it as an aerobatic mount? Can you do crisp 4 point rolls in her? 8 points maybe?

If you've flown a Pitts, how does Jr. compare in control response and roll rate?

Thanks,

Well Pierre, the Pitts is one lien of aircraft in which I have never had any flight time, so I can't give you a comparison. I doubt that anyone will be using an RV-3 to compete in world-class unlimited aerobatic competition, since it is still a "Total Performance" airplane, and doesn't live in a specialized niche.

Hesitation rolls are nice BTW - I won't say that mine are particularly crisp, but that's not the fault of the airplane....

Paul

[Louise Hose]

Originally Posted by Ironflight

10) I am a bit worried about the ventilation ? the round skirt vents we installed are gorgeous, but seem to be embedded in a bad flow area ? they produce mostly noise, and little airflow. We have a set of RV-10 back-seat vents on order that we might install in the fuselage below the longeron ? one or both of these should do the trick.[/indent]
Paul

While acknowledging that Paul has a lot more hours in the -3, I haven't noticed any problem with ventilation. I have a strong breeze on my face when the vents are open and more ventilation than I really like when the vents are closed. Of course, it also has been pretty cool on all flights, so far.

Remember that Paul is a product of Minnesota and has the air conditiioner on in the house and car all months of the year in Texas. I'm not convinced that this issue is "real" for me or warm-weather lovers.

[David Paule]

I'd sure like to see some photos from another airplane of the cockpit and cowling and wing and landing gear attachment areas with yarn tufts taped on.

It would be very interesting and show us what effects the cheeks have.

Ideally it would be at cruise and again at climb angle of attack and power.

I've noticed that it's useful to take at least a couple photos of the same spot because there's a chance you'll get a prop blade passage and its wash, which is quite localized, will stir things up. In between blade passages the free-stream flow can be seen.

People tend to think of prop wash as a steady but turbulent flow although it's actually quite limited in area. Of course you get three passages each revolution with a three-bladed prop, so they come pretty often. You'll see.

Thanks!
Dave