Riv-Nuts

A number of locations on the aircraft require the installation of riv-nuts. A Riv-Nut metric tool with the ability to set M3 to M6 Riv-Nuts  is required to complete these task. There are many models available with varying quality but this builder invested in a basic Ebay model similar to the model shown below.

For those new to the use of these tools the operation requires that a rivet nut be screwed onto the a pull up stud to suit the selected riv-nut. Insert the nut into its hole and with the flange resting on the skin, squeeze the handle to upset the back of the nut enough to captivate it into the flange provided [see diagram below].

Riv-Nut installation diagram

The best place to test drive your new tool is at the rear access panel located at the rudder fin on the starboard side. Complete the riveting with the 1/8'' countersunk rivets provided in the kit. Fit a M3 pull up stud provided then a M3 riv-nut ,insert and squeeze to upset [expand] the back of the nut. Squeeze until a firm resistance is felt and then stop, inspect . With the tool purchased the depth stop was set to nearly full depth for this operation.

Rear access panel ready to rivet


You Tube Video - How to use a Rivet Nut Tool

Panel Arrangement

After much thought and study the final panel arrangement for this builder's Tucano-R is shown below. The center of the panel is a AV Map V chosen for it size, features, performance and ultimately for weight. It is surrounded with the basic analogue flight instruments, airspeed and altitude being 80 mm [3 1/8] instruments with the ROC and compass being 57 mm [2 1/4]. 

Rev's and manifold pressure are  57 mm [2 1/4]  with all others 32 mm [1 1/4].  Trim indicators and A.O.A. are clustered around the airspeed indicator as is a G meter. in the final  analysis  the AV Map V G.P.S. is the center of the panel and part of the pilots natural scan.

Begin of a well matured vintage I am blessed with excellent distance vision but have the usual problem requiring glasses for close up work. The AVMap dose have every flight instrument available but except for the A.H. its all text and this is a challenge as digital equipment require's you to read them NOT scan as with analogue instruments.

The other reason was to capture the feel of the prototype's panel while lowering weight and complexity, to that degree this builder is happy with the final arrangement but if you want the lightest of panels go full digital with the largest screens you can afford..!

One feature is that the hydraulic and fuel panel will have the circuit breakers are located on those panels so in a emergency the hardware associated with the area of concern should not require the pilot to sort through the conga line of breakers with tiny, tiny labels as in a conventional beaker panel.  

This is always a personal decision for any builder and this will be my personal list of excuses..!

Metal Cutting

With the Australian Quick Build Kits it was decided to supply the rear flight controls in kit form to meet the requirement of AC 21.29 which defines the 51% rule.

One of the tasks assigned is to trim the skins to their correct width. The cut lines are marked at the factory using a standard offset of 10 mm. These could be cut using a guillotine or aviation snips and like most builder's I do not have ready access to a guillotine so snips are the only option. 

A new set of Weiss snips were used on the top turtle deck skin with the lack of skill of the user begin more than apparent. The main issue was the witness mark and local distortion  created near the tip, there had to be a better way.

A Sonex builder used a laminate cutter to open an aileron to add a trim motor - so if it can do that why not trim a sheet. A Olfa [P-CL] Heavy Duty Laminate Cutter was purchased with 2 packets of spare blades plus a length of 25 x 3 mm off aluminum extrusion from the local hardware  store.

The strip was marked at the standard factory edge distance of 10 mm and then three [3] holes drilled using a sheet as a template. The factory punching is on a standard pitch so this should be a one time job.

Scrap from sheet

The first job was to cut a slither off one skin that was not as tidy as this builder would like. The bar was fixed using three [3] clecos and two [2] pieces of dressed 50 x 25 x 600 l/g pine were placed on the underside of the sheet. These are positioned at either side of the cleco pins to support the sheet during the cut. The cuts are best achieved using a 450 mm [18''] strokes. The first few cuts are the most important, be light and accurate, continue the cuts until the sheet is penetrated to a depth of 60% or more. If longer cuts are required, move along the sheet and repeat the operation. At the completion of the cut fold the scrap to break it free, dress the edge with a flat file to remove the burr.

The first and second images opposite shows a slither cut off one sheet that this builder wanted to tidy up.

The photos below shows the rudder skin begin trimmed on both sides ready for installation. The timber blocks in this case offered protection to the other side during the scoring operation.

Overall this builder is very happy with the final result and it is faster to do than write about.

Timber support

Finished rudder skin

Stab Assembly - Part 1

The stab kit consists of a series of pressings, skins and mounting brackets. All holes are matched drilled by the factory so the major task faced by the builder is the correct assembly of the parts. Begin by identifying the parts and their locations by studying the 3D illustrations in the factory assembly manual.

You will need about 150 clecos to fully assemble the frame ready for riveting. All rivets used are 1/8 pop rivets supplied by the factory as part of the kit.

As part of the assembly four [4] captive nuts supplied MUST be fitted to the inside of the rear spar. This was missed by this builder and later required a quick back track to under take the task.

The front attachment has to be now prepared to allow the frame to be installed into the fuselage. Fit a bolt through the single attachment point - the hole on this one was chased out using a tapered hand reamer fitted to the battery drill. Align and clamp then match drill one 1/8'' hole through then fix with a cleco as shown then drill all holes to complete the part.

At this point assemble the rudder hinges. The bracket with the slots are the top hinge. Note: The bracket with the bearings are fitted to the rear stab spar in both cases.

Assemble using a AN4 bolt and nylock nut with a aluminium full washer placed on both bearing to  space  the  brackets clear of the bearing faces. These have too be disassembled  to install the brackets into the rudder later.

Before fitting the rear spar to the fuselage install four [4] to the rear bulkhead and the deck. This builder chose to rivet the skins with the stab installed to the fuselage. The rear spar is fixed at six [6] point provided with AN3 bolts and nylock nuts.  Refer factory assembly manual for details. When complete fix at the front using a single bolt and nut.

The rear rib on this kit required a slight trim to allow fitting. Once correct fit clecos to the two [2] holes then match drill from the front - once done fit the final rib and cleco. Fix all 5 points with 1/8'' pop rivets. Review the factory notes for final details and only when 100% sure fit the skin to the open side in preparation for riveting. If there is any doubt ask your technical adviser to come over and check all the points.

There are two [2] lower infills strips to complete the rear rudder shroud - slip under skin and align as shown then match drill as shown. Both shrouds MUST be drilled before fixing to allow access - see image above. The drill shown is a long series aircraft drill with its primary feature being a short area of fluting compared to its commercial equivalent.

The backing strips located on the inside face of rear spar located at the base shown on the drawings and MUST be installed as in accordance with the factory drawings. The backing strips are pre-punched and will fit either side.

Note: The stab will have to be removed to allow installation of the horizontal stabilizer but this builder decided it would be a good place to start , access would be easier and with this approach the frame is jigged to the aircraft during assembly.

Antenna Installation - Part 1

Locate the port skin removed at the start of the project.

Fully cleco the skin back into position ensuring the the lower skin of the baggage compartment over laps this skin. With this done remove the starboard lower skin and placed with the port side - these require trimming before re-installation.

If the belly skins have been fitted this is the LAST practical chance to install all the necessary cables for the elevator trim and antenna cables unless you are in possession of a very well trained ferret..!

Locate the aircraft antenna - read the notes as some manufacturers place limitation on location. The last practical point is just behind bulkhead eight [8] and must lay between bulkhead seven [7] and eight [8].

This builder located the front mounting hole on the first rivet behind bulkhead eight [8] and then taped the template into its correct position then all holes drilled. The three [3] rivets that the antenna base covers were installed, checked and the effected area primed. 

The antenna was installed with a small but practical modification. The short screws supplied are impossible to engage in a practical sense from the underside of the skin. Studs 30 mm long were fabricated from donor screws and screwed into the base of the antenna. The two [2] center line studs had a star washer - light aluminium washer and a half nylock nut for fixing.

The start washer bites into the spline and ensure the base is grounded at two [2] points. Once ready a suitable sealant was applied to the base and the antenna installed with the two [2] center studs tightened fully. A quick check of alignment and the outer one were run up till the washer touch the skin.

Note: Due to the curve of the turtle deck an aluminum spacer was sourced from Pro Bolt [shown opposite]  The cups are installed inverted too as shown and profiled to suit. The cup area was filled with sealant to ensure a tight seal with the skin

Nylon Clip

The trim cable is a 5 core cable for the MAC trim motor and was sourced with the antenna cable from aircraft spruce. The cables were secured to the side of the bulkheads using nylon clamps and large head pop washers.

   Helpful EAA video related to required task is listed below:
    
    Installing Antenna

Canopy Actuator - Part 2

This builder decided to remove some weight from the actuator bar by drilling a series of 8 mm OD holes at a pitch of 20 mm. Do not attempt this unless you have a drill press and are experience working stainless steel. 

All the working faces were polished using a flap wheel in a drill press. All the parts are reassembled using M4 Hex bolts, washers and nuts. After adjustment it was found that the mechanism was very stiff accompanied with metal on metal grinding. After a quick check the source was located at the back spring mount.

Witness marks from spring stop

After investigation it was determined that the rear spring mount was fouling on the rear tang of the actuator due to a combination of tight tolerances and installation by the builder. As this bracket is only a stop for the spring it was decided to remove it and enlarge the slot width and depth with a 5/32 chain file.

Actuator bar assembly

The assembly is re-installed,  adjusted and tested to be finally rewarded by the "thunk"  of the spring returning the bar.

To mount the handles M6 stainless steel all thread rod is used. Determine the length by ensuring the thread is fully engaged into the handles to provide maximum support to the aluminium. 

The handles threads are treated with Loctite 243 at assembly and allowed to cure.

All working faces of the actuator were treated with "Dry Lube" at assembly.


Do NOT rivet either of the cover panels at this time as the interior cockpit covers are riveted under the top angle on both sides.

Rudder Pulleys - Part 1

Guides:
There are four bushes to be installed at bulkhead nine [9] and ten [10]. The holes are pre drilled in the bulkheads but not in the bushes. Each bush was matched drilled from the hole with the best  access.

Insert bush mark the first hole with a 1/8'' drill, remove and drill through. 

Re install with a cleco and match mark the other [2] holes, remove and drill through.  

Repeat this operation for the other three bushes and install using 3 pop rivets. This builder chose to install the bushes with their flanges facing each other at the last bay - why? - if you ever need access only one skin has to be removed.

Pulleys:
There are four [4] pulleys to be installed at the spar area, again all holes are pre-drilled.

Inspection off the pulleys revealed that some of the clearances are a little tight for this builders personal preferences. The pulleys were dissembled and fiber washers installed on each side of the pulley to limit the travel of the pulley on the bush. 

The fiber washers were manufactured from 1/4''  fiber  washers enlarged with the taper drill by hand. These had to be held with a cloth as it just plain hurts bare fingers. One step is drilled, reverse the washer and enlarge to 5/16'' to clean up the burrs.

The factory M4 x 20 screw were replaced with 22 mm long screws cut from longer screws to provide two [2] threads projecting from the nylock nut. The tangs were flared by five [5] degrees and pulled into alignment with the screw at assembly.

There are left and right hand version at assembly that allow the pulleys too be installed heads up on both sides

Install as shown in the manual

Baggage Compartment - Pt 1

This builder chose to fabricate the components for a closed baggage compartment from 0.025'' 6061 T-6 aluminium sheet. All panels were fitted using 1/8'' x 8 mm pop rivets. To restrain the baggage and front door quarter turn aluminium D ring's from ProBolt Australia were selected. Each clip and ring weigh 10 grams and four [4] points were added to the front and rear. A set of lightweight straps 2 meters long x 25 mm wide with plastic clips are fitted to restrain a load. Maximum weigh allowed in the baggage compartment is 10 kg and is for soft or bagged items only.

Tape skin into position - factory supplied

Prime factory rear panel for installation

Installation of the back panel requires removal of the compartment top skin and turtle deck by drilling out the factory temporary rivets to allow the rear skin to slip behind the factory bracket. Match drill bulkhead from the factory bulkhead - cleco and rivet. The bottom edge should be riveted before fitting the turtle deck skin. This will be a combination of the D ring clips rivets with filler rivets in between at using factory pitch as the guide.

Rear bulkhead

Drill out the four rivets at the back to allow the rear panel to slide behind the other bracket on the other side. Tape the rear panel into position and match drill the holes from the panel through the rear former. 

Match drill through the existing four holes in the bulkhead through the back panel. Once complete reassemble using clecos and rivet using 1/8 x 8 mm pop rivets. 

Creating slot

Connecting Flange

The next task is to adjust the front bulkhead flange to engage with the skin. Start by cutting on the center of the existing holes starting at third hole from the bottom. The top stringer is de-riveted and its connecting flange bent into alignment . 

Cut a V at about 5 degrees at each  side of the initial cut. Use a 5/32'' chain file to open the cut and form a half radius into the edge of the flange. [refer photo]

Bend the top tab into alignment with the spline and cleco. The others are bent using your hand forming a smooth transition from the top to the side. This is not a critical operation, you just need a smooth transition between the tabs.

Front bulkhead      -       Rear bulkhead tabs

Refit the skin using clecos to re-align the front bulkhead. The rear bulkhead has two separate extensions pieces that project into the baggage area. The slots are just slightly visible on this aircraft and were a possible source of leaks as the skins are not lapped at this point. Both were covered with self adhesive aluminium duct tape that was on hand. On the port side simply cover from the base to the center line of the spline. On the starboard side the tab was de-riveted, covered and trimmed to size. The exposed ends had scrap backing reapplied to allow re-installation by sliding the tape between the skin and the bulkhead

At this point preparation for installation of the turtle deck was next.

Elevator Push Tube - Part 1

The elevator is controlled by a push pull tube on bearing mounted bell cranks with all connections made with threaded rod ends fitted at both ends .Begin by removing the front remand which is held in by a series of temporary rivets. The front edge has a angle fully riveted to the panel - do not drill these rivets only the ones into the riveted to the skin and longeron. Remove the panel and place to one side for future installation.

Front Bellcrank

Install the front bracket and bell crank onto the rear spar mount with four AN3-7A bolts.

The rear bell crank on mine required an amount of fine tuning before installation. The mounting centers pre-drill into the mounting bulkhead is a 60 x 20 grid. Measuring the assembled bell-crank assembly unit it was 61 x 20. It was dissembled and the two packer washers between the bearing and bracket filled down by 0.5 mm [0.020''] to achieve the correct centers. Reassemble loosely to aid assembly.

Install rear bearing to ensure a bolts are correct - For information Click Here

Rear Bellcrank

On this kit the top two bolts fouled on the reinforcing brackets on both sides. The best solution was to file one of the bolt heads flats providing the correct clearance at assembly. All bolts used are AN3-7A . 

You will require a large degree of patience or hands with the ability to emulate a snake to install the bolts. The best technique was to insert a bolt through the selected mounting hole and with one hand inserted through the 100 mm fanged hole a washer or nut is guided on to the respective bolt using a combination of both hands - it's really quite easy, really.

Once the bracket is installed time to calculate  the length of the tube. At this point I noted that one end was badly damaged and mild panic set in with thoughts of  "I cannot remember hitting this that hard".  Once calm returned it was determined that the tube was oversize and only one end was damaged.

This leads to a simple warning that this tube is very light and can be damaged easily by striking a prepared edge so exhibit some care in handling.

The overall length has to be calculated and the center so the center distance has to be determined. A cheap tape measure has a hole drilled a 1/4'' diameter at the 100 mm mark, this is secured to the front bell-crank using a bolt and then extend the tape to the rear bell-crank. While holding the bell-crank in its correct location with a bolt fitted into the lower mounting hole, mark its center onto the back side of the tape with a Sharpe pen. Rechecked to verify the marks position and then removed to the workbench to calculate the tube length. The timber block is to lock the bell-crank into it correct location while pulling on the tape.

The calculation is fairly straight forward using a few basic parameters. The threaded length of the rod end is 22 mm and 5 mm was allowed for lock nut with and minimum engagement into the mounting resulted in a nominal 10 mm projection from the mounting with the threaded rod now in its mid position. The assembled length is measured for both fittings and this was deducted from the theoretical center to center measurement taken with the tape. Remembering to deduct the 100 mm from the measurement read from the tape measure.

Mark cut point with a Sharpe pen and then wrap a strip of cardboard wrap it twice, secure the end with a length of tape. Align the edges of the cardboard to create a straight line through the tube - mark the perimeter with the Sharpie pen. 

Following the line a series of cuts are made while rotating the tube in steps, try to cut as deeply as possible without penetrating the tube. Repeat until a full revolution of the tube is completed. At this point use the saw to cut straight through the tube using the groove as the guide. The tube will cut easily so it all happens quickly. To finish off check with a square and carefully dress the edge to remove any inaccuracy's with the cut.  Polish the edges at both ends with 400 aluminium open cut. Remove all the plastic wrap and wash with thinners. Finally polish out any mill marks or scratches with 400 grit aluminium open cut, clean and prime.

Yes it fitted...!

Calculation sheet

With this kit one of the fittings was size for size fit and was therefore quite tight to assemble. This requires a hammer to drive it into the end of the tube. Fit a AN4 bolt fully into the tapped hole then tap the fitting lightly into the open end. Rotate after each few taps and recheck alignment until engaged sufficiently to ensure a straight insertion. At this point a few sharp blows will drive the fitting home. Once installed fix the fittings to the tube as outlined in the factory notes and drawings.

Fixed with two rows - eight rivets in total - both ends