RV-8A Building Tips and Ideas

Armrest braces

I give credit when I steal an idea from another custom builder, but this is my idea, as far as I know. I noticed in Van's demo RV-8A that the aft "arm rest" consoles have "No Push" decals on them so I assumed there was a problem with passengers using them to push themselves up when exiting the plane. So, I decided to add braces under those rests to carry some of the weight in case a passenger should inadvertently put weight on them. It is even more of a possibility in my plane since I'll be building wider consoles.


This shot shows the location and construction of the brace. I lightened it as much as possible.	A shot from another direction. This was taken after the shot to the right. I had done some priming of the interior at this point. Notice I opened up the relief opening on the arm rest so the console angle can fit.	The console angle has nutplates attached that allow connection to the arm rest. You can see how the brace will strengthen the console. I plan to add more braces forward to support the consoles. You can also see my floor cut to permit removal of the floors.

Magnetometer Mount

I wanted a magnetometer mount that would not flex (and thus introduce erroneous indications) during any maneuvers. Additionally, I needed to position them at least 24" from ferrous metal. The aft fuselage above the upper longeron was the only place that fit the bill. Working in the aft fuselage of a RV-8 quickbuild is, to say the least, interesting. The mount is a bit heavy at about 1 pound, but I'm willing to spend some of my "weight money" that way.

	I'll have dual magnetometers because I have two independent, redundant EFIS systems - the BMA EFIS One and the BMA EFIS Lite. BMA says the mags need to be mounted at least 24 inches from ferrous metal or electrical interference. The only place was just forward of the tailcone bulkhead. I sacrificed some weight to have a stiff mount and to raise the mags up as far as possible from interference.
Here's my design for the magnetometer mount. Should withstand 9 G's, don't you think?		A view of how it will fit into the fuselage

Removable Cockpit Floors

Van's plans call for the rear baggage and cockpit floors to be permanently riveted in place. However, I want access under the cockpit floors for maintenance and inspections. For example, my aileron autopilot servo, aileron trim, comm or transponder antenna mount, wiring connections, rudder cables, and who knows what else are under the cockpit floor. It seems prudent to me to have reasonably easy access to those items. Drilling out rivets to gain access under the floor is not reasonable, at least to me. So, I installed nutplates instead of the proposed rivets for the rear baggage floor and the cockpit floor. One issue regarding the cockpit floor was the flap mechanism. Removing the floor meant also removing the flap mechanism. I wanted a removable floor without the hassle of removing the flap mechanism (which probably would have necessitated the flap motor removal, as well), so I cut the rear cockpit floor to make removal possible without removing the flap mechanism.

	I carefully planned the floor cut to leave the seat back hinges in place, avoid cutting the under floor stiffeners, and allow good edge distance for the attachment screws. I could have riveted in the under flap portion of the floor, but I had already installed part of the nutplates when I realized that option. I recommend other builders using this technique rivet the portion of the floor under the flap weldment.
	I used #6 screws and nutplates, but were I doing it again, I would consider using #8s. They are more robust and are less likely to strip out. If you use #6 screws, then I recommend the Torx (6 lobe) head screws from Microfasteners.com. Also, apply a bit of Boelube to the screw before inserting.	Steve Metzger recently suggested that I may want to consider adding a stiffener to the long span in the middle of the floor cut. I tested the center of the floor and agreed with Steve that it needs a stiffener. Should you decide to use this idea, I suggest you add a stiffener similar to the one described below. Additionally, you could hide the entire gap by adding a flange to the bottom of the floor all the way across.
	I started with 3/4" .050 angle and removed most of one side to reduce weight - shown at left. Right: I used 470 3-3.5 rivets to mount the stiffener

Photos above show detail of the cut, stiffener, and location of screws	Photos below show the RCP floor installed. I know the floor panels are opposite to the plans. Some more of the sloppy work the first owner did. I decided it is not structural and could stay that way.	Use of the #6 Torx head screws is much better than Phillips head. They don't strip and can be reused. I recently bought a nut driver that is very handy for driving the screws.

	These final photos show the baggage floor in place. Notice that I made the baggage floor removable (for the same reasons as the rest of the floor) and thus there are no fasteners along the aft edge of the cockpit floor and leading edge of the baggage floor. I may go back later and add some nutplates to the bottom of the baggage floor and connect the floors together using #6 CS screws.
	Well, those photos weren't so final after all. After some discussion, Nelson believes we should add back in the strength removed when the floors were cut. So we added the nutplated braces shown in these photos. This will easily add the strength back to the floor.

Consoles

While several builders have added consoles to their planes, I haven't seen one yet that extended the consoles to the rear cockpit. After careful measurements, it became obvious that the angle of the rear armrests could be continued along the same angle and the line would intercept at the edge of the center instrument panel. Perfect for my plane since I'm also planning hinged access behind the center instrument panel. The instrument panel is hinged (see next item on this page) and thus it would have to clear the proposed consoles. By continuing the line of the RCP armrest to the instrument panel, a pleasant appearance for the consoles was established. Yep, the consoles add a little weight, but I removed a little weight by eliminating the original throttle quadrant. Anyway, for me, it is weight well used. The space under the consoles will be used for some of my other ideas. Those ideas will follow later.

	Building the console frames is proving to be challenging. To insure they aren't too flimsy, I'm bracing them in several places.
	I was able to make the right console top cover from one piece of .032 and got it to fit reasonably good. Once I like the fit, I'll duplicate it for the left, although the left side will have to be cut into several pieces to fit around the throttle.
	Left photo shows angle added to bottom of console side cover to strengthen it. I rode in another guys -8A and despite being careful, I caught my toe on the bottom of the normal Van's console and the edge easily bent slightly. This angle will help prevent that. The right photo shows the new aft cabin covers in place. I ordered new ones from Vans without the "crease" vertical bend.

Hinged Instrument Panel

The center portion of my instrument panel hinges for access behind the panel. I believe ease pf maintenance and convenient access are important and contribute to the overall pleasure of owning the airplane. So, I'm trying to design in features that will improve maintenance access. I've seen a number of -8's with the access panels cut in the aft side of the forward baggage compartment, but I'm not a big fan of that approach. It appears to me that access will still be clumsy through those doors. I studied how to make a hinge that would allow the instrument panel to pivot as much out as it did down. That would permit any deep instruments or radios to clear the top of the panel opening without touching. That was achievable, but I decided it wasn't worth the time and effort to design and construct the hinges - it was just getting too complicated. (I'm willing to share the ideas if anyone else wants to attack the problem.) Instead, I took the KISS method and installed a simple piano hinge on the bottom on the center panel. It is much simpler, lighter, cheaper, and still permits good clearance of the deep instruments. Since I'm using EFIS most of the things in my panel will not have a lot of depth. I'll build in service loops for the wire bundles and pitot lines behind the panel.

	Left is one potential layout for the panel. The entire center portion of the panel is hinged to allow access to the avionics. I made avionics mockups to test the fit of everything.
	The test fit revealed a problem with the longer boxes not clearing as the panel is hinged out. Pete Rafferty suggested solid mounting the long boxes and fitting the panel to them.

Horizontal Stabilizer Attachment Nutplates

I learned a trick from another builder that will make life much easier when it comes time to reinstall the HS. He mentioned that it is very difficult to put the nuts on the forward HS attachment bolts once the fuselage is closed. I studied his remarks and it is apparent to me that I would have to climb into the fuselage tail cone from inside to be able to put the nuts on the HS attachment bolts. That would have been virtually impossible. He suggested adding nutplates where the nuts would normally fit. Why didn't I think of that?? I followed his lead and added the nutplates.

	The rivets were long to reach through lots of metal. I used the bolts to hold the nutplates in place while I squeezed the rivets. My Tatco squeezer was perfect for the job. The bottom photos show that I had to use a one lug nutplate and install it at a slight angle to get everything to fit. I suppose I could have used two one lug nutplates and had more edge clearance - although mine is sufficient. Below is a shot finished with bolts removed.

Autopilot Aileron Servo Mounting

I stewed a long time about where to locate the BMA aileron servo. I couldn't find a suitable location in the fuselage so I had resigned myself to mounting it in the right wing. I didn't really like that idea though because 1) 2.2 pound servo out past the aileron bellcrank, 2) attaching to the bellcrank would be clumsy, 3) I didn't like the potential of the servo linkage coming loose and interfering with the aileron bellcrank, 4) I would have to work through a wing inspection hole to install the servo, 5) removal for maintenance of the servo would be challenging, and 6) I would have to mount the servo on a wing rib. Just too many things bothered me about mounting the servo in the wing. Fortunately, I talked to Bob Northrup from Blue Mountain at Sun n Fun 2004 and he said the servo could be mounted under the cockpit floor aft of the aileron trim. I went to the shop and studied the possibility for awhile and convinced myself it would fit. That was a relief because it brought that weight back to the centerline, eliminated the bellcrank issue, and shortened the servo linkage. I then had to devise a servo mount that would accomplish several things. It had to strengthen, by use of a doubler, the under seat rib where it would be mounted, it had to allow for fluting of the mounting rib, and it had to provide a barrier to prevent the aileron servo actuator arm from coming out of the servo during flight. I also needed an attach point on the control column weldment for connecting the servo linkage.

	Left: Initial part design Right: Mount after lightening holes, doubler, and primer.
	Left: Shows how the mount will prevent the actuator shaft from coming out of the servo. Right: The mounting location in the fuselage. More photos will follow to show the linkage and control column attachment.

Photo shows where I had the servo linkage attachment welded on	Servo installed with linkage	Looking aft at aileron servo linkage.

Instrument Panel Overlays

I plan to put plastic overlays on the entire instrument panel and part of the consoles. The overlays will be reversed engraved plastic. I'm still considering EL lighting for backlighting the panels. If the new LED flat panels become available, I may use those.

	Left is an example of the China Blue Gray reverse-engraved overlays that will cover the panel and consoles. I bought this panel at http://www.aircraftsimulators.com and I'll likely use them to make all my panel overlays. Update: I discovered a local engraver who can supply the same colors and has experience doing aircraft panels for local pilots. I'll try his product and report back here with the results and any recommendations.	Below shows the EL lighting used to backlight the reverse-engraved panel. I will dim the backlights and also use the EL lighting for flooding the consoles. Next I plan to mount neons under the wings and put hydraulic lifters on the landing gear. I'm gonna look really Rican.

Symmetrical Footwell I prefer symmetrical F-889s for a number of reasons. One is appearance. Another is that it provides a place to hide the electric fuel pump and associated plumbing. It will be removable for maintenance access. The right F-889PP will likely hide a/the battery and will have a top cover to separate the baggage area and provide access to the battery. Even if I don't use it for a/the battery, I'll run wiring in it and probably install the common ground panel there. I'm still deciding whether or not to have one battery or two.	This view looks down in the footwell from above.
	Left: After initial bends and before priming Right: Here's what is will look like when finallly installed. Gives a finished, symmetrical look.

Hidden Circuit Breakers

I want the cockpit to have a very uncluttered appearance. To help achieve that, I intend to hide the circuit breakers (yep, I'm using CBs instead of fuses) under the arm rests. The arm rests will be hinged inboard to reveal the trays underneath that contain the CBs. I'll also have some of the rarely used switches and the ELT remote switch there. Here are some photos to give some idea of my plan.

	Left is the right console CB Tray with 21 holes for CBs/switches. To the right shows the tray inverted. I don't plan to use these CBs because they aren't pullable. These came with my kit so I'm using them as placeholders.
	The consoles will be slightly wider than four inches. That will do several things: retain the roomy feeling in the cockpit, provide extra panel space for switches, and still permit full lowering of the main instrument panel for maintenance. The left tray will have only 9 positions (so as to not interfere with the throttle linkage) and the right side will have 21 positions.

Well, I'm going to plan B. There isn't enough room under the left console to insert a tray for circuit breakers. So, I'll only have the right console tray (21). That means I have to locate some CBs in other places. Since I don't want CBs showing in the cockpit, I'm going to use P&B W31 CB switches for protecting some of the wires. I think under the left console I'll build a 1" x 5" x 10" tray to hold charts such as sectionals.

Showing the cutout in the original armrest and attachment to the console frame. It is remarkably strong.

Showing the CB tray with console top cover installed

The chunk of 2x4 simulates the planned armrest. The armrest will be this size and will hinge inboard to reveal the CB underneath.

Autopilot Pitch Servo

There are several places one might locate the pitch servo and many ways one might connect it. Here is how I did mine. There was a method to my madness. I wanted the servo aft for CG, I wanted as short a connection as possible between the servo and the elevator assembly, I wanted to connect directly to the bellcrank rather than tying into the push-pull tube, I wanted the servo to sit level, I wanted it to not interfere with the magnetometers, and I wanted it to be clear of the rudder cables passing below it. Although the mounting bracket is a bit heavy at about 1 pound, it is solid and I'm happy to spend some of my "weight money" that way.

Interior Lighting

As you can see above, my original plan was to backlight all of the plastic overlays in the cockpit. Further investigation found that installing EL lighting behind the panels would be difficult to accomplish, fragile in use, and a headache to replace. So, I began looking at front lighting the panels instead. The best choice to light all panels came in the form of LED strips designed for 12v and with resistors already built in. The LED strips are relatively sturdy, produce little heat, provide even lighting, are dimmable, and last thousands of hours. I need to light the instrument panel, the FCP consoles, the RCP consoles, and the baggage compartments. I found 12-LED strips at theledlight.com which can be split into four 3-LED strips if desired. I decided to use one full strip for each side of the FCP, a 9-LED strip for each side of the RCP, five 3-LED strips for the instrument panel, two 3-LED strips for the switch panels, two 3-LED strips for the aft baggage, and two 3-LED strips for the forward baggage. So, now I needed some way to mount the LED strips. I bent some .025 sheet to make mounts that will attach the switch panel LEDs to the forward side of the F-804N channel cap and, those for the consoles, under the canopy rail on each side. The console light mounts use the canopy rail screws for attachment.

The LED strips as they arrived from theledlight.com. They can be separated by scoring the backside and breaking them apart. The resistors are already installed to make them 12v compatible.

Left shows the LED mounts inverted. The top one is for the FCP consoles, the middle one is for the RCP consoles, and the bottom one is for the switch panels

Right shows the FCP LEDs in action


	Left shows the FCP left console flood LEDs installed. I'm using Perihelion Design dimmers to control the LEDs - if I can figure out how to install the dimmers.

Rudder Cable Clearance

In the A model, the left rudder cable rests on the mounting tube of the external step. I called Van's and they are aware of the problem and suggested adding UMHW tape on the contact area and just check it periodically. I'm not too keen on that idea so we're had our favorite local welder cut a groove for the cable and weld back in a trough for it to pass through. We'll add the tape for additional insurance.

Even with the mod to clear the rudder cable it still has the possibility of rubbing, so we're still going to add some tape to protect the tube and rudder cable.

Power Receptacles

Here's an idea for installing two power receptacles that will keep them out of sight yet make them easy to access. I intend to use them for gooseneck map lights at night and for any use in the day - such as handheld GPS, small 12v heater or blanket, cell phone charger, etc.

Nelson built an L bracket of .040 that fits neatly behind the F-817 Seat Back Support Plate. The right photo shows two of the four screws in nutplates in the bracket and the left photo shows the power receptacles from below.

OAT Probe

Locating the OAT probe where it will provide accurate readings can be challenging. Many custom plane builders mount the OAT probe in the fuselage NACA duct. Some have mounted them in the underwing NACA duct. Both locations can be subject to heat from the engine and are in the prop wash. I've decided to locate mine out in the wing where the original aluminum pitot tube was intended to be. In the quickbuild kit, that hole is already drilled for the aluminum pitot tube. Since I am using a heated pitot, I had no use for the the hole. In this location the probe gets no direct sun and is out of the prop wash and away from the engine. Time will tell if it works.


The bracket made to fit the OAT probe in the wing	Showing how the probe projects through the wing. It's held in place by an adel clamp and a grommet in the wing.	Another shot showing the relative location of the probe on the wing. The nearby heated pitot will rarely be used and, when used, it would only be detected by the OAT when no air is flowing past the wing - i.e., sitting on the ground.

Wingtip Lighting

A lot of guys have put the landing lights in the wingtips, but I haven't seen tip lights like these before, so I'll claim this as an original. I intend to have wig wag halogen recognition lights and HID projector lights. In addition, the wingtips will enclose the position lights and strobe lights. My goal is to increase reflectivity of the lights as much as possible. So, I am making a fiberglass foundation to hold the lights and I will cover the fiberglass with polished .032 sheet. I will ask about chroming the sheet, but if that is not feasible, then I'll polish them. The strobe effect will be greatly enhanced and the position light will be somewhat improved. Here are several photos showing my progress on the wingtip. This is only the prototype.

	Left is the concept with a teardrop shaped plexi cover. The bent metal in the front was an experimental idea to increase reflectivity but it was discarded as too work intensive in relation to any gain realized. To the right is my first fiberglass work. THAT is ugly!
	I used scrap metal on the prototype, but all .032 sheet metal will be flat and polished to maximize reflection. Right photo shows the wig wag light on. The wig wags will be able to flash or burn constantly as a landing light. The wig wags have to be halogens because the HIDs don't like to be flashed and don't show up well in daylight.
	The prototype revealed some things that need to be changed. Still, it gives a good idea of how the wingtips will look. Prototype to right gives a good indication how the final wingtip lights will look. I like the RMD Lenses, but I'm getting this one scratched, so may have to beg them for another one.

Looking at the right photo, the large reflector will be halogen recognition lights that can either be flashed or burn steady. The smaller opening to the right is for the HID projector lights. The tip will be highly reflective so the forward strobe and the position light should be significantly enhanced. For a pair of Whelen wingtip strobes ordered from Aeroparts and Supply, the cost was $300. I got the power supply and tail strobe on sale at SnF and paid $350 for both.

The wingtip has evolved. The original concept had to be modified because of several issues - there was not enough room, finding round HIDs of the right size was difficult, separating the position light and strobe light used too much real estate and the halogen projector light for the recognition/taxi light was heavy and ran very hot.

So, next I considered using an automotive reflector and modifying it to fit, but that involved a lot of cutting and compromises. I didn't like the look of what I was getting. So, I finally realized that the best option was to go with high dollar aviation lights and quit trying to save money.

I settled on using Whelen LED lights for recognition/taxi and Precise Flight's (http://www.preciseflight.com) new rectangular HID for landing lights. I also bought the Whelen combination strobe and LED position light. All of this was expensive even though I scrounged around for the best deals, but the weight is reduced and I'll have the light combinations that I want. I spent close to a thousand dollars on all the lights. Ah, it's only money.

To provide a mounting for the lights above, I needed to make a fiberglass insert into which the lights could be mounted for installation in the tip. Here is how I did the insert. The initial wingtip layup was okay - not great, but okay. One was good the other had some lumps. I had to do some filling when I removed them.

The piece of foam is to hold the fiberglass wingtip at the correct opening as if it were attached to the wing.

Next I made styrofoam pattern to lay fiberglass over to make the actual light mounts.


To make the foam inserts for making the light mounts, I started by using the end of the wing to press foam on which made an impression of the wing and then I cut them out. I used the spar as a reference point.	This shows how the cut foam fits into the freshly made wingtip inserts	I cut more pieces to an approximate shape for the wingtip and glued them together. A hot glue gun works fairly well.


I added a layer of foam to the inboard side of the foam to give it some strength. My work with earlier prototypes indicated that a single layer of foam was too weak to work with. Here I've done the initial shaping and sanding.	Next I cut back through 3 layers of the foam to form two mounting areas - one for landing lights and one for taxi/recog lights. Here you can see approximately where the foam will fit inside the wingtip insert.	Here the foam has its final shaping and is ready for the fiberglass layers.


The first layer of glass on the foam. Later the foam was removed leaving only the fiberglass form. I'm using S glass which can withstand 1500 degree heat and is a little stiffer than E glass. The glass that meets the inside of the wingtip will be only one layer thick. The other faces will get 4 layers since they will be the actual mounting locations for the lights.	Here the peel ply is coming off the second layer of forward facing foam.	The final (fourth) layer of glass is curing. I used fast hardner in the West system and I had to work quickly to get it done before the resin began to gel.

I want to cover all of the fiberglass with aluminum for several reasons. The aluminum covers can be easily removed and attached for maintenance. They can also be polished to increase reflectivity. They also blend in with the concept of a metal aircraft.

I'm planning to use #8 SS Torx head screws to attach the aluminum covers and I'll put nutplates inside the fiberglass for attaching the aluminum overlays.

Here are all of the aluminum overlays cut to fit on the fiberglass wingtip inserts. I drilled them to the inserts using #40 bits and later opened them up to #6 screws. I hate #6 screws, but used them here because I don't have much room and they will rarely be removed.


Left is the template, then the original light cover. I made a mistake on the original so I made a new one. The new cover is marked on the wingtip insert	Here all of the covers are cut and the cuts in the fiberglass are marked.	All of the metal cover pieces for the wingtip lights. I've scotchbrited them and primed the backs. The front sides will be polished.

Weight and Balance

I intend to operate my RV-8A in multiple weight ranges with restricted G limits as the gross weight increases. This will allow me to takeoff with a higher gross weight for flights that require limited maneuvering and G loading, such as a cross country flight. As weight is reduced higher G limits are permissible. Regardless of gross weight, normal CG balance must be maintained.

I plan to fly my RV-8A with the following weight and G limits.

- The Maximum Takeoff Weight will be 2000 pounds and G limits will be -1.0 to +3.0

- At a gross weight of 1800 pounds, the G limits will be -2.0 to +4.4 (Van's numbers)

- At a gross weight of 1550 pounds, the G limits will be -3.0 to +6.0 (the maximums at any weight)

Mud Flaps

Apparently mud/snow/muck can be picked up by the tires and deposited in the aft end of the wheel pants causing them to sag and, potentially, break the mounts. There are a couple of things that can help with the potential problem. First is to add reinforcing fiberglass to the inside of the wheel pants where the screw holes are located. Additionally, adding a barrier in the tail of the wheel pants will block stuff from getting in the far aft end of the pants. You have to make sure the brackets and the tires stay clear of the mud flaps inside.

Here's how we added the mud flaps. In all three wheel pants, we cut and belt sanded 1 inch styrafoam (insulation from HD) to fit tightly and laid fiberglass over it. I like to add a bit of Microlite to the resin mixture to add some color to the clear resin to make it easier to see where it has been applied, thus the reason for the tan color of the added fiberglass.