Intercooler - Part 1

This blog covers the status of the inter-cooler design

Why.
As a opening comment the developer of the FlyGas supercharger has seen NO need for inter-cooling at the time of writing and historically no problems have been reported.

Australia can see extreme temperatures of 45 C plus so runway temperature off 60 C can be possible as a worst case possibility. Reference to my book on auto superchargers show's a boost of 6 psi should not take an engine with suitable fuel too detonation but at 60 C it would be getting tighter.

Effect of inlet temperature on outlet temperature
Ford Mustang 5 litre

The chart is based on a 71 F which is about 21 C so at a theoretical 60 C inlet temperature could reach 95 C for a short period and this is the problem Jack Riley encountered with his turbo normalized Lycoming upgrades of the 1960s.  

[The writers opinion is that short period, light detention  was the reason it appeared after time in service]

Extract Rotax 914 owner manual Section 4

"This sensor monitors the air-box temperatures. The TCU operating program is designed to reduce boost pressure if this sensor indicates the air-box temperature is above 72ºC (162ºF). In the normal course of running a turbo, the natural compression of air (adiabatic compression) as well as heat transfer from the hot turbo, raises the temperature of the incoming intake air. Testing has shown that intake air temperatures below 60ºC (140ºF) provides an adequate safety margin in preventing detonation in the engine in the event of a lower octane fuel and a high intake air temperature. In cases where the air-box temperature is run between 60ºC (140ºF) and 72ºC (162ºF), a higher octane fuel must be used "

Refer: Tornado Alley Turbo on this subject

"A current technology good inter cooler design can reduce the induction air temperature so that turbocharged or turbo-normalized engines see induction air temperatures that are much more comparable at all altitudes and power settings to a hot day normally aspirated engine than they are to a non-inter cooled turbocharged engine"

So put simply I have a developed prejudiced for the use of a inter-cooler not as a power boost but as added insurance - cost about 2.9 kg.

Design
After reference to my automotive design reference on inter-cooling a Bell Intercoolers  aluminium 14 x 5 x 2.5 inch ordered but at the time weight was not considered and its a little heavy at 2.15kg.

The design of the structure is a major issue as there are no 3D models so all the design is based on 2D drawings and site measurements. After a lot of thought it was  decided to collect the boosted air in the front tank, pass it through the core to a rear tank and finally to the carburettors to create space and flexibility for connection to the engine.

The struts are there as I cannot see a way to connect it to the engine mount but it may most likely end up there in the real world. The current weight as shown is 3.24 kg but involves a lot of turning to remove all unwanted weight and doing it again a 2'' core would be more than adequate and save about 400 grams.

All connections will be done using 2'' OD SCEET hose allowing the blending between the various outlets. It is lighter that silicon, flexible and has a suitable pressure rating. As part of the manufacture a JEGS beading tool will be used to bead all connections and all connections will be double clamped. The completed unit will be load tested to 7g at assembly to verify the design.

A final check will be done on my return and if confident all the components will be machined and assembled at a local engineering shop. The last item to be installed is the inlet pipe as I suspect that it may have to be relocated but that will require installation of the engine and supercharger. 

The final baffle and inlet design is up in the air but one step at a time.

Is it worth while - well if it works I will never know but its insurance.

Draft Design

View from underside

View from top side

Plan View
Tank 80 mm OD @ 164 mm centres  - outlet 462 mm centres
Tank overall 373 mm 
Cut-out at rear is to clear hydraulic cylinder mount
may be relocated to under side

Lights- Part 2

This blog covers the tail group navigation lights

Lights
The use of lights at an aerodrome is covered under CASA CAR 196 [3] and by this builders reading the rear light is required and a red beacon optional. Both were incorporated as this aircraft is in full camouflage and if you assume it works we need to ensure that it can been seen at any airfield.

After a search Avio Lights was settled on based on the weight of 40 grams..!

Rudder Installation
The decision was made to add a additional faring to the rudder lower fibreglass faring. A profile was designed on the CAD system and the STP file sent to China and in a week a pair of ABS plastic faring.

Faring

A notch was cut in the rear of the factory faring to allow the wires and plug to be pulled through. In doing this the rear split open so a plywood wedge was sanded and glued into the opening with 5 minute epoxy to reinforce that area.

The new faring were installed using epoxy and a series of 5/32 pop rivets to secure the pair while drying and for long term security. The finished area was tidied up using blade putty and sanded.

The controller was mounted on a aluminium bracket riveted to both sides with 3.2 mm countersunk pop rivets. 

A connection is located inside the fuselage so a maintenance loop is included for that task.

Ready to install
Faring was fixed with button head M3 S/S screws to allowing servicing

Fin Installation
A red beacon from Avio Lights was fitted to the top faring of the rudder stab.

A no faring could be found so a profile was designed on the CAD system and a STP file sent to China and in a week a pair of ABS plastic faring. Its installation required a lot of filling and sanding to install further complicated by the need to square up the faring covered in Part 3.

Note: A spare one became the faring for the Trim Tab - Part 5

To secure the light M3 rivet nuts were coated with Loctite Black Max ACC and installed at the rear and lightly expanded to prevent pull out.

The controller was incorporated into the top rib of the stab with a maintenance loop.

The faring is fixed using M3 button head screws.

Underside fairing

Controller installation fin

Lights - Part 1

This blog cover the installation of cockpit lights.

Cockpit Lights
Though this aircraft can only be flown VFR as a ultralight it was decided to add some cockpit lights if required.

To keep the military theme up this meant installing two spots lights. A suitable set were located in black with a red light at Aircraft Spruce that were cost effective, small and light.

Tucano cockpit

The mounting is a M3 flanged rivet nut, nylon and spring washer. The first task was to enlarge the washer using a step drill allowing it to fit over the flange. With the rivet nut installed and the spot light bracket removed the assembly was fixed to the side cover. 

Once tightened the spot lights were reinstalled with their nylon washers and the lights adjusted. 

When wired each will have a local switch allowing them to be individually turned on and off.

Components ready for installation

Note: The spring washer was placed under the mounting bracket in the recess created by the washer.

Spot lights

Fuselage Vents

This blog cover the additional of fuselage vents

Outline
In a effort to improve the cooling drag of this Tucano it has been decided at some future point to add gear doors to the nose gear. This however will create a problem with removing the hot air created by the radiator, inter-cooler, engine and exhaust as at this time it all escapes from the wheel well.

As the guide rails for the ballistic parachute are not used on this aircraft with a combined area of about 2.25'' and are there to be used for another task. 

Side vent's used on Jeep's were selected having nearly the same overall width as the existing opening allowing rivets to fix it to the side of the fuselage.

Two models were ordered, a 12'' and a 18'' to be used in the wheel well doors.

Supplier: Run Cool Hood Louvers

Skins
The rip off side cover supplied with the kit were used to create an infill panel riveted to the underside of the existing skins. It was cut 85 mm wide and match drilled to the longeron. 

Outlet ramp

Firewall Seal

A tongue was cut about 125 mm long and riveted at it's end onto the channel face.  High temperature silicone was applied at the edges to seal the air to the ramp created. This area has to be sealed regardless as its a direct channel into the cockpit for unwanted fumes.

A infill piece for the front was cut from 0.016'' 2024-T3 sheet with a cut-out under the louvres [seen in grey in the image  above] 

Finally two small angle were cut to infill the top and bottom edges of the opening at the firewall and then riveted to the longeron faces. High temperature silicone was applied to the face in contact the firewall before riveting.

Louvre's

The louvers were cut to provide 6 vents with the top edge was angled using a set of 4'' duck bill pliers with a small angle was created on the lower flange to ensure a tidy fit. All the edges and rear face were sanded, as the metal is fairly heavy there is adequate to remove all marks and to flatten the back.

Finally 12 and 24 mm radius's were applied at each corner as required then both vent's were  primed and allowed to dry.

Louvre fixed onto top skin

Fitting
The top two holes pick up the existing mounting holes with the lower three [3] to be matched drilled.

Each vent was fixed using 3.2 mm x 10 mm pop rivets onto the side of the fuselage.

Merry Christmas 2015

Well its years end and this builder has no idea where it all went. Like all builder's I hoped to have more completed but taking time to review the blog dose provide some reassurance that a lot of work was completed.

Were are we now?

A lot of tasks are nearly complete and I hope to finally install the rudder and elevators in the New Year once a few small outstanding tasks are complete. It is amazing how long it takes to do the really small things well and to source and take delivery of that final do hicky thing.

At this point I am off for a holiday with the family and will not be back at work until the third week of January but will finish off some of the ten or so blogs in draft form. My hope is that the readers found something of value in the past year and excuse me for some poor grammar.

Next Year?
The cockpit area will begin to take form clarifying the design philosophy outlined over the past year and the quick build wing kit will be mated to the fuselage allowing those two areas to begin their assembly.

Merry Christmas and a Happy New Year
from Australia to all

Canopy Bubble - Part 1

This blog is to cover the work in the installation of the Australian Tucano.
Reference: UK installation

Marking Out
With the frame positioned in the locked position the canopy was installed in its correct location onto the frame. Two [2] cut-outs were made on the starboard side to allow the canopy to fit snugly onto that side.

Note: The canopy lined up well with the frame so this proved a simple task.

To prevent tearing away to much of the canopy's protective cover a tape line was added around the canopy and then the cover rolled up to the tape, then using more masking tape secured it to the canopy. This process was repeated on the inside with the best technique to roll the cover with the fingers until a roll formed which is pushed / pulled up to the same line as the outer cover.

Note: This was done on the aircraft as the builder was one [1] up not by design 

Ready to mark out

The next decision was were to cut the canopy because of the recess in the frame has a taper, this creates a number of options but it was decided to use the external edge which later proved to be fortuitous. 

A cut line was marked using painters tape tracing chosen external edge.

Marked out ready to cut

Cutting
A Dremel motor tool and snake attachment were used in combination with a thin cutting disk running at about 17000 rpm, this is the same method used by the Brazilian dealer to cut their canopy.

Cutting finished

Finishing off
The canopy and frame were removed and placed on to work stands for the necessary finishing. It was decided to block sand the edges using 80 / 120 / 320 grit aluminium open cut paper. 

With the canopy slid back and placed on timber to allow access and starting at the front the first three sides to the back. The hinge side was ignored to allow final adjustment after the opposite side was prepared, this proved to be a poor decision.

Sanding the edges

The canopy was now placed back onto the frame and it was noted that when sitting centrally there was about a 5 mm over lap from the edge. It was realized that with the canopy sitting on the outside of the frame and choosing the external edge as a cutting line that it was oversize when place into the frame's recess.

This operation was repeated many times and proved quite difficult as there was only one person on the task - see comments.

Marking out the front and rear edges for trimming

It was decided to first correct the front and rear relative to the frame recess and this was done using the sanding paper and required a number of difficult refits begin one up.

With the front and rear edges about 1 mm from the outer edge of the recess it was time to trim both of the sides.

Why God chooses to look after drunks and fools this builder builder can only guess but for no reason I decided to look at the other side revealing a hairline crack.

A stop crack hole was required urgently and the battery drill was quickly fitted with a 2.5 mm drill and a stop hole drilled just in front of the crack. Next this hole was chased with a hot soldering iron with a 3 mm OD tip. 

Success or failure will be determined on the return to the hangar next week.

A home builder greatest fear

Analysis

Offset created by rolling 
canopy starboard

After a period of quite thought it was decided to use the excess on both sides to remove as much as the crack as possible. This placed the canopy a little off the marked centre but at times like this, one has to be pragmatic as a bullet had just been dodged.

Had the work continued with no reference to the hinge side this would have become a total disaster with the next move.

With the canopy re-positioned the excess material was marked out with tape and duly cut and dressed.

Final Fitting

The chamfer on the edge of the frame recess prevents the canopy from nesting correctly. With the outside edge used as a cutting reference that had just saved the canopy this builder had by now lost all taste for working on the canopy and it was decided to just chamfer the edge.

A fine sanding drum fitted into the Dremel and a combination off 30 / 45 degree chamfer's were applied to all four edges of the canopy. 

This was achieved starting with the 30 degree chamfer running against the direction of rotation to start the chamfer and to providing the best control. 

Next cutting was done with the against direction of rotation using light pressure and multiple cuts at 30 degrees in the direction of rotation and finally at 45 degrees. 

With the chamfer established it was all finished with 320 grit to polish the chamfer and finally the edges was radiused by running the paper along the edge with the hand. The bevelled  edge was finally blocked with 320 grit to remove any minor scallops

Finishing the edges.

Texta used to mark radius
Chamfer shows as the clouded line at edge

The line was marked using a felt tip pen to highlight the recess radius then the excess cut with the Dremel motor tool , finally the edge was profiled and chamfered using the drum sander. 

Comment
It could have been worse - maybe.

If doing it again,

• You need two people as the excessive handling required by one person raises the risk of damage significantly.
• Using a Dremel the Thin Cutting disks proved to do the best job at about 17000 rpm
• As soon as the cutting is finished sand every edge to the 120 grit stage before commencing any work or buy a panic button.
• The cutting profile would have to move in from the edge to allow for the canopy to grow in the slot when cut.
• Bevelling the edge did create a neat fit but remember on the Tucano the factory intends the exposed face of the canopy to be on display. With this aircraft a shroud to create the unique Shorts T1 look has to be constructed.
• After every task check all edges of the canopy carefully for any signs of a cracking.
• Have a drill ready to stop drill if required.
• Have a small bottle of Acetone and small paint brush ready to glue any crack together  and to fuse the hole smooth.

Shorts Canopy

Baggage Compartment - Pt 2

Finish the baggage compartment to gain the points assigned under AC29.21

Background
What restrictions are placed on the aircraft after completion is a function of having to protect third party's. As an experimental aircraft pilot I am free to kill himself in any manner I chose's but not a third party. In fact a TC only responsibility is to the third party and the only control are restrictions so the closer the project is to the FAR's the less restrictions the builder can expect on the aircraft's use.

Restraint of object's in the baggage compartment is a requirement as tie downs and other items can be free to fly in a survivable accident.

Cover's
The cover's consists of two [2] separate panels manufactured from 0.025'' 2024-T3 aluminium sheet with the lower one hinged and the upper one fixed with three [3] Pro-Bolt quarter turn clips.

The lower panel was cut from the aluminium sheet and a 20 mm aluminium piano hinge was fixed to the lower edge with 2.4 mm [5/32] pop rivets pitched at 30 mm. The upper edge had a piece of 12 x 12 x 1.5 aluminium angle fixed from the top edge and fixed with 2.4 mm [5/32] pop rivet's pitched at 60 mm. 

The location of the rivet line was set to be about the center of the uppers panels channel rivet line to avoid one rivet head resting on another.

Lower panel trial fit

Angle stiffener - short to clear bulkhead

Upper Panel

Bulkhead layout

The upper panel was profiled to suit the turtle-deck and to overlap the lower panel and was fabricated from the same material as the lower panel.

A angle was fabricated  from 0.020'' 2024-T3 - 35 x 10 mm and then fixed to the lower edge using 3.2 x 6 mm pop rivets pitched at 90 mm in two [2] rows.

The fastener's are secured with dome head pop rivets but these stopped the panel laying flush, so the solution was to add a series of rivets series around the bulkhead perimeter to support the panel. 

A 10 mm wide strip of foam was added at the edge of the panel to close the visual gap after painting. 

The top panel was secured using three [3] Pro-Bolt Quarter turn fasteners as discussed in Part 1 of the baggage blog. This arrangements negated the need for any locking mechanism other than the fasteners as the upper panel traps the lower panel and the channel transfers the loads into the lower fasteners.

Final assembly - final details parts yet to be fitted

Comment
The only change would be to locate the lower attachment points to the angle center to create a stronger connection. To solve this an angle stiffener will be added once the clips arrive also the D handle is a little long and may be looked at later.

Upgrade Fuselage - Part 2

With the completion of the upgrade at station 4 the next was station 5. 

This blog is written to record the work undertaken and is standard in the new models as required.

Preparation
The new battery drill was used to remove the rivets securing the existing gussets. To provide better access to remove these rivets a fuselage gusset was first removed then the heads were removed followed by the body's.

To provide a better edge distance at the longeron's new gussets were fabricated from 0.040'' 2024-T3 aluminium. These were dress to fit the odd angle created with the fuselage then primed.

After priming the plate was marked out to match the pattern used on the front gussets and all holes were drilled to 3.2 mm. 

The plates were then primed and painted to match the fuselage and set aside to dry.

Assembly
The gussets were fitted and the first hole drilled from the inside through the fuselage and a cleco added then all the other holes were added, cleoced and finally riveted inside and out. 

Lower packer - tapered

Full Packer

Inside cockpit

Fully Cleoced

Riveted - typical both sides
Both stations shown

Flap Drive - Part 1

The factory-supplied all components for the flap mechanism.

Trial Assembly

Fig 1

The #6 bulkhead has four [4] mounting holes for the bearings, pre-drilled in the lower bulkhead gussets for the bearing blocks. 

Each bearing block was mounted using two [2] AN3 bolts, and after fitting the torque tube, the outer block was fitted, and the assembly was clamped lightly using the bolts.

The arms were located equally from the outside faces of the bearing blocks at a distance of 71.3 / 71.5 mm from both sides of the bearing block's external faces.

With the shaft located, the external faces of the bearings were transferred to the shaft with a felt tip pen.

All components were now removed for painting and finishing.

Painting
The torque tube is manufactured using two separate tubes, which are disassembled by removing the four [4] AN3 bolts securing the assembly. The orientation of the aluminium coupling was noted for reassembly. 

The two bearing blocks are machined from an aluminium bar fitted with plastic shell bearings, these were removed, and the bearing were placed to one side.

Preparation Process

The location of the bearing blocks on the tubes at both sides was offset by about 1 mm, and two layers of masking tape were applied. Next, the area was coated with an automotive paint stripper, and the areas were wiped clean to bare metal. 

The masking tape was removed, and the bare area was covered with new tape painting for the final painting.

The bearing blocks were marked with a centre punch to allow matched reassembly.

The individual items were all cleaned, primed as required, painted with the cockpit colour, and set aside to dry.

Assembly Torque Arm
The torque arm is now reassembled, and the AN3 bolts were tightened lightly to avoid crushing the tube; both bearing blocks were reinstalled with the bearing shell, torque tube and the mounting bolts were lightly tightened. It was noted that the shells would spin in the housings with the tube, and it was decided to lock them into each bearing half.

Note: to assist in disassembly, the mounting holes were enlarged to 5 mm to provide additional clearance

Comment: doing this again, I would look at using floating nuts riveted to the inside face of the bulkhead at the elevator side.

The method chosen was to apply a bead of Loctite Black Max ACC, align, then fit the bearing cap onto the opposite bearing block, and the assembly clamped using a quick clamp to dry. Both bearings assemblies were fixed using this process.

Locking Bearings

The tube did not fit into the bearing on reassembly, so each bearing was sanded using 320 grit aluminium open cut wrapped around a rod the same diameter as the tube. After light sand, each bearing closed around the tube with 0.015'' aluminium shims fitted to prevent lockup at final assembly.

Note: The problem with the fit may have been caused by the application of the ACC closing the gap at the entrance, and we would most likely use the small tube as a spacer when clamped if doing it again.

Bearing block ready to accept torque tube
The installation of floating nuts is recommended for maintenance

The bearing was greased, and the long torque tube was installed with the final operation to fit the short tube, locking collars more than the last two retaining bolts.

The grub screws holding the collars were treated with Loctite Thread Lock on assembly. All bolts were carefully hand-tightened to ensure smooth operation when turned by hand.

Flap Drive Fuselage Mount

Remove & replaced with counter-sunk rivets.

The actuator attachment arm was set at 78 mm, as shown in Fig 1. 

When the cylinder was installed, the mounting bolts for the actuator appeared to land on a set of existing rivets. 

After contacting the factory, it was decided to remove the existing rivets and replace them with counter-sunk rivets to allow the actuator brackets to be installed.

The plans call for the brackets to be fixed with AN3 bolts, but an examination of the upper mounting showed that this would not be practical, and it was decided to mount the brackets using 5 mm pop rivets to secure the brackets. 

The brackets provided suitable clearance to the existing counter-sunk pop rivets.

Drive Attachment
Examination of the mounting points showed that when the brass bushes and mounting bolts were assembled, there were no fixed relationships. It was decided to fix the mounting bolt's relationship relative to the other components.

An AN4 bolt was brazed to an S/S lug manufactured from 0.015'' stainless steel. The upper pin was pop riveted using a countersunk rivet located on the inside face of the outer bracket. In contrast, the lower pin's tab was extended to lock into the exiting slot located through the side of the arm. 

At the assembly, 1/4'' fibre washers were fitted at each face of the brass bushes; finally, an AN4 nylock half nut was fitted and lightly tightened to secure the whole assembly. The fibre washers are to as a washer and prevent damage to the arm.

Upper lug

Lower Lug
Note: Fiber red washer typical on both sides

Final installation

Comment: If the upper lug was fixed using a screw into a tapped hole, this would allow the removal of the spigot bolt like the lower mount.