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What to consider in building my wings

Taltruda

Well Known Member
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I am waiting on my slowbuild RV-8 wings.. what things should I consider? I’m already doing the Newton Aero caps (A30L Vans)

I’m thinking Garmin G3X, so is the Garmin autopilot the way to go? I’m not really sure what other options for an autopilot that I should consider. Should I order some Garmin (or whoever’s) servo brackets to install while building the wings?

What pitot tube is best? I want heated, is the Dynon one the hot setup? Again, I’m really sure what other options are out there, I like the look of the Piper blade though.. Does the Dynon play well with Garmin stuff? Does it have AOA capability?

Thinking about moving the pitot tube outboard one bay to prevent tie down rope clearance issues.. Do I purchase (or make) another wing inspection flange to cut into the next bay?

When building the tanks, should I install a return fitting just I case? I was planning on mechanical fuel Injection from Don at Airflow performance..I don’t know if I’ll ever need the return, but perhaps if I use the purge valve setup?

Any other things that I should consider while building the wings?

Thanks!
 
Locking gas caps

Think about the locking gas caps; the wing part is different i believe. Also think about the lights, are you going to use the FLYleds in just the tips or A leading edge mounted light.

If you are set on the G3x i would definitely put the Garmin servo in when u build the wings. I used the garmin pitot tube with the non-garmin mount ( the one everyone uses)
 
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Something to keep in mind is that you don't have to completely close up the wings before moving on, and in fact it might be a solid idea not to do so. As you're seeing, closing the wings means at least somewhat committing to some systems things, which IMO are decisions best left as late as possible. I still don't have my wings closed up, and I'm about to the point of ordering avionics and finish kit, and getting going on some wiring harnesses. Once the top skins are riveted on, the wings will be sturdy enough to come off the construction stands and go into storage on a cradle if desired.

The fun thing you're discovering, as I did, is that it's in the wings where you start having to think 482 steps ahead. Thinking of the AP servo is good, you'll probably want to at least install the servo mount kit before closing the wings, if not the servo itself. Same thing with the pitot in the left wing.

On the pitot topic, I'm not sure if the Dynon pitot plays nice with Garmin or vice versa, but I wouldn't count on it (at least for AOA...everything else ought to be fine). As far the pitot location, if you're only placing it one bay away from an access cover, I think you won't need an additional cover. You'll likely end up with the connections accessible from the adjacent bay anyway, and that's the big consideration.

Return fitting on the tank is maybe not a horrible idea, though you'd have to cap it or something if you ended up not using it, and so it seems like another potential leak path. I didn't do return fittings, and so while the purge valve seems interesting, I'm not wanting to go add the return fitting at this point, though that has more to do with additional plumbing in the fuselage.

Another thing to consider would be your intended lighting setup, most notably whether you want to go with landing lights in then leading edges. It's much easier to make those cutouts before the leading edge assembly is permanently attached to the wing. If I were doing wings from scratch right now, I'd seriously consider the Flyleds Works kit, which puts the landing lights in the tips. I've got some of Paul's products and both they and he are awesome.

Also, regarding the fuel tanks, you'll have to decide whether you want to put a flop tube in one or both tanks. This is only necessary if you want the ability to do sustained inverted flight. I put a flop tube in my right tank mainly as a "well maybe" consideration.
 
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No flop

Since I don’t plan on negative G, no inverted oil, I don’t want to do the flop tubes. Don’t the flop tubes need to be replaced once in a while anyway to prevent hardening? Also, don’t tanks with flop tubes tend to have more unusable fuel than a fixed pickup?

I didn’t realize that Garmin made a pitot tube! See? That’s why I asked. Which servo mount is the one that “everybody uses” and where do I get it?

I love “the works” all in one light setup, and it’s for sure overkill to do them AND another set of lights in the leading edge, but it would be nice to light up the sky with both! Any aerodynamic penalty with the leading edge light lens and it not being “laminar” compared to not cutting the hole for the lights?
 
I closed up my wings not long ago, so I know the thought processes you're considering now. I pretty much agree with what Phil said above, probably with the exception that I did close things up.

I definitely found it to be much much easier to muck around with the servo & pitot (Dynon Heated Pitot) mounting & wiring with the lower skin off. Fitting and wiring the roll servo would be a real pain with the bottom skin in place, so aim to get that all done first. With the heated pitot there are a couple of considerations - there's a lot of wires to connect, the thermocouple wires from the servo are absolutely tiny and will break off the connectors if you look at them sideways, and you've got to find a nice place to install the heated pitot controller.

Other considerations include how're you going to run wires (snap bushes or conduit?. Drilling the extra holes for the AOA tubing, and your tank fittings. I'm building a -9 so no flop tube for me but I omitted ordering Van's pre-made pick-up tube with the stainless screen. Test your fuel senders for resistance before you fit them, as I had one that was faulty and Van's sent me a replacement pronto.

Get the servo mount kit for the particular servo you're buying. I'm certain both Garmin & Dynon do kits for their respective servos to suit your aircraft.

I've got a works FlyLEDS kit, so all is wingtip mounted.
 
Yeah, I believe the flop tubs does have a service life. We'll see if I eventually end up regretting the decision to install one...

As Goeff mentioned, there are prefab servo install kits you can get. I actually just ordered my roll servo and mount kit, mainly so I could get free shipping on the Spruce order I was placing.
 
NACA inlet in lower skin

I installed a NACA inlet on my -4 R/H lower wing skin using location sketch from an RV-8 plan..not sure if it is shown as "optional" , but I highly recommend doing it. I have a SCAT tubing that routs it to the rear stick well where I put an eyeball vent for PAX. It moves some serious air! I also put electric aileron trim in my -4, and a decent 3/8-1/2 conduit from root to tip will handle all the wiring needs for that and lights.
 
The NACA scoop on the bottom of the left wing is standard on the RV8. I would second the statement about conduit to bushings for wiring. I went with conduit.
 
Since I don’t plan on negative G, no inverted oil, I don’t want to do the flop tubes. Don’t the flop tubes need to be replaced once in a while anyway to prevent hardening? Also, don’t tanks with flop tubes tend to have more unusable fuel than a fixed pickup?

I didn’t realize that Garmin made a pitot tube! See? That’s why I asked. Which servo mount is the one that “everybody uses” and where do I get it?

I love “the works” all in one light setup, and it’s for sure overkill to do them AND another set of lights in the leading edge, but it would be nice to light up the sky with both! Any aerodynamic penalty with the leading edge light lens and it not being “laminar” compared to not cutting the hole for the lights?

If you don’t plan on sustained negative G and have no inverted oil, there is no need for a flop tube.

FWIW, I installed my flop tube circa 2000-2001. My airplane was put in service in 2007. I replaced my flop tube last year, 2019. It was just as flexible as the new one. Maybe it’s because of all the exercise I give it!:)

Before my first flight, I measured the unusable fuel in each tank with the airplane in a level attitude. The tank with the fixed pickup had 4 oz of unusable fuel and the tank with the flop tube had 13 oz unusable fuel. In practice I have purposely run the flop tube tank nearly dry while at altitude and still had 1/2 gallon when I filled up. Yes I did have an appropriate amount of reserve fuel in the other tank.
 
I installed a NACA inlet on my -4 R/H lower wing skin using location sketch from an RV-8 plan..not sure if it is shown as "optional" , but I highly recommend doing it. I have a SCAT tubing that routs it to the rear stick well where I put an eyeball vent for PAX. It moves some serious air! I also put electric aileron trim in my -4, and a decent 3/8-1/2 conduit from root to tip will handle all the wiring needs for that and lights.

The NACA scoop on the bottom of the left wing is standard on the RV8. I would second the statement about conduit to bushings for wiring. I went with conduit.

The HOLE for the NACA inlet is already cut in the wing skin of the RV-8 bottom skin of the right wing so you will install it at some point in the future.
 
My thoughts:
- Autopilot servo; at least for the Dynon SkyView system this can be done after the wings are done, or flying for that matter. We recently did just this on a flying RV-8A.
- Pitot; again for the SkyView the pitot can be deferred but the pitot mount should be done before bottom skins. You can do it after the skins are on, but it is much harder. Also adding some nut plates for the Pitot Heat controller (Dynon system) to an adjacent rib would make life easier.
- All wiring can be deferred. Even adding the conduit can be deferred as it gets in the way when you go to buck the bottom skin rivets. 1/2” cold water plastic pipe (from the aviation section of Lowes) fits perfectly in the per plan wing rib holes, and has enough room for all your wires (landing and NAV/Strobe, Pitot Heat, roll servo and coax to your wing tip VOR antenna).
- Do not install a flop tube as it is useless unless you also have an inverted oil system. Buy the very nice, already assemble pickup tubes from Van’s instead of making your own. https://shop.vansaircraft.com/cgi-b...8-226-705&browse=airframe&product=fuel-pickup
- Do not touch the wingtip until after the wings are on the plane and you have high confidence you rigged the flaps and ailerons exactly correct. This is to mitigate the dreaded “my wing tips don’t line up” syndrome.
- Do not cut out a hole in the leading edge for landing lights. Install two of these on each wingtip, one for landing and one for taxi. Way more than enough light. https://flyleds.com/products/#!/Single-Spotlight/p/108852015/category=0

As your can tell, I fly SkyView and recommend the system.

Carl
 
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Do the landing lights or position lights come with the wrong kit or finishing kit? Thinking about making substitutions..
 
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