Canopy Last Jobs

This blog cover finishing the canopy.

Overview
The canopy on this aircraft has been modified in a number of ways some planed and others forced by the execution. Yes, it added a bomb in extra time so be warned.

Installation Shroud
The shroud is the most distinctive feature of Shorts T1 Tucano so this was the first extra item fabricated. While simple on the outside, the execution was a protracted task due to a lack of experience and the risk of damaging a very expensive piece of perspex. After weeks on/off of filling and sanding, the time to fit it onto the perspex and frame had arrived.

The scheme developed seemed /simple enough, the external edge was to be fitted using 18 x 1 mm double-sided automotive trim tape with the rest affixed with beads of SikaFlex Eurthane adhesive sealant. The first issue was that when dry fitted all look great but now all those little issues raised and in the end it was decided to cut the single piece shroud into four [4] pieces and then re-fit them. 

This worked well except for the last one on the starboard side and this turned into a custom fit - why? - who knows but once it was 80% done it had to be finished.

The shroud was a big job and once painted it will now have to have the edges filled as they are not as flush to the perspex as the builder would have hoped. This was caused by the mounding tape as it packed up the edge up by a1 mm and exaggerated any fabrication errors.


Once done the band across the top had to be dressed, while the initial thoughts were for a painted black band at this point something more substantial was required. 

The answer came in a roll of concrete gap foam that was glued together to form a 20 mm thick light flexible strip with the top having a series of lighting holes drilled to create a sense of importance. 

It as glued onto the canopy with a pair of 3D printed ABS covers blending it into the frame.



Handle
The kit did not include an external handle and it was decided to modify a commercial flip out but he the builder saw prices in the $250 plus range back to the CAD system. A flip-out handled was printed and installed. 

This required the cutting of a suitable hole through the side so this was done with a combination of fear and care. In the end, it was secured as planned with two [2] x M4 aluminium screws from the inside of the frame into the handle body. 

The handle will lock using a piece of fridge magnet strip fixed to the inside of the body with a screw located into the handle

Will be made available on the web site once ready for sale.


Latch Cover
One of the last issues was the latch cover through the side cover on the frame. A number of attempts to install the factory slotted stainless steel covers were tried but with deteriorating results. 

It was decided to print an ABS cover and install it covering up the gaping hole in the side cover, after a couple of tries a successful model was developed and a Marwen cover printed with instructions.

Will be made available on the web site once ready for sale.

Canopy Handles

It was decided to print handle covers for the pilots and co-pilot's canopy latch handles for comfort and eye candy. 

They were printed, painted and fixed using M4 grub screws onto the existing handles.












Will be made available on the web site once ready for sale.

Seals
There are no details on seals but it was decided to add a D seal along both of the fuselage sides of the aircraft, Using any sealing material can cause an inability to close the cockpit due to the forces required, do not be filled by how soft it feels as the forces added up quickly making a closure on the latch side impossible.

A D seal will crush easily and the one chose when flattened was the same or slightly lower than the hinges when closed. Will not airtight it should help resist airflow into the cockpit area when airborne. Goliath 15 x 10 mm self-adhesive D seals were selected then fixed using urethane adhesive to the canopy frame. It was felt that the self-adhesive tape may not have the required durability in service.

Explosive Cord
One of the key features of a Shorts T1 is the white lines created by the explosive cord used as part of there aircraft ejection systems. While these were to be painted, the builder was not 100% on board and resulted in a  better product being discovered. This was in the form of 9 x 6 mm D foam self-adhesive door seal material by Raven in Australia. 

Using photos of the Shorts T1 canopy a suitable generic scheme was developed and applied. 

The overall result idea produced a good result on the inside, this builder will have to wait for the unveiling until the painting has been completed.

Canopy Installation General
My canopy was an early model and the new aircraft have larger hinges and a ring [frame] that locates the frame to the fuselage but my issues I will outline for reference.

The first issue was the hinges these required packers to locate the frame into alignment with the frame. Once this was done the shroud was fabricated and this is covered under the category "Canopy" in this blog.

At one point the factory and this builder decided to try installing a gas strut to support the canopy when open and limits its travel, this is now done with a cable. Based on information supplied by the factory on the Brazilian Tucano the builder took up the challenge. 

After fabricating the necessary structure some real issues surfaced with the worst being that the canopy now was 6 mm out of alignment at the front this was traced to the 15 kg of thrust from the gas strut when closed and the clearance in the hinge pivots.

The original canopy was located on pins on the port side, these did not now line up and after numerous attempts at modification and redesign, they were abandoned as a lost cause, at this point, I could remove the strut or burn more time.

Not being very smart it was decided to press on. 

In the end, a roller was fitted to the frame that countered the strut and rollers added to the canopy frame at the from and rear. Bakelite button aligned the canopy as it closed at the from countering the tracking forced generated by the roller with buttons at the rear bulkhead being the last locator. Did it work? - yes - Did it burn time - Yessssss.

Final Clean Up
When applying the adhesive to secure the canopy the dread of all builders occurred - some got onto the exposed area and the time had arrived to fix it. A Novis kit consisting of Part 1,2,3 was purchased along with a sheet of 600/1200 grit wet and dry.


The affected area was sanded with the 600 and then 1200 grit in straight lines crossing at 90 degrees. Next the area was polished using the Novis #3 the #2 revealing a smooth canopy and no mess. 

Finally, the whole canopy was polished using Novis #2 and cleaned and polished with #1. 

When the painting is complete the exterior will be treated in the same manner to reveille hopefully a shiny clear canopy.
 




Comment

Based on the drama this builder has created assembling the canopy I would have the factory fit the perspex if you can afford it. If not fix the canopy using an automotive urethane adhesive sealant and do this with it installed and locked on the airframe and allow it to cure. The assembled unit is very flexible so it is the builders opinion that it would be best to not build in any distortion if possible.

The shroud was a lot of work but in the end, it makes this a Shorts T1 not just a Tucano.

Why are these things not as simple as our dreams -eh?

Headset Sockets

This blog covers the installation of the headset  plug points.

Overview
With diminishing real estate in the cockpit there was no place to install the headset plug points. Locating them on the port side would be a pain as it required crossing over the leads to exit.

Inspiration was found in the prototype when a box was noted on the side of the canopy and it was realized that headset leads plugged in here could be simply hung up at exit.

Shorts Tucano T1
Note box ringed in white

A pair of plastic jiffy boxes were selected from Jaycar and installed onto the side frame using four [4]  #6 x 12mm S/S self tappers to allow removal for painting.

The two sockets were installed on the front cover and interconnected using multi core cable fitted through 10 mm loom tube via the grommets in the image below.

Jiffy boxes ready for cable installation

Note: One advantage of the plastic boxes is they create a floating earth required by the jacks without the need to use insulated inserts

Next the existing side panel was drilled and profiled to allow a RS232 9 pin socket to fit through with the cable connecting the radio with the headset and intercom. The plug cover was fabricated from scrap 0.040'' 2024-T3 aluminium sheet fixed with M3 screws and rivet nuts onto the factory side cover.

Pilots connection point and plug entrance
Hole required bell mouthing to clear plug

Co-pilots connection points
Loom tube will be clipped to the frame after painting

Comment
Why do this in the middle of wiring - well it create's all the necessary fixed wiring points required to complete the cable connections.

A final shot of the cockpit - it's a rough mock up but I hope you can see a cockpit that creates a military feel and not just another GA cockpit and yes, it's so 1980's !

The box on top is the get-out-of-jail card if the compass is unhappy in the panel
So far its looks happy but it will be interesting when the power is applied
and we try to swing it.

Canopy Breaker

This blog cover the selection and installation of canopy breakers

Overview
One of the issues that any canopy aircraft has regardless of how it is opened is it can trap the occupants in a rollover. The military have used canopy breakers since the introduction of this canopy type.

Again RV builders provide a solution.

Installation
The two canopy breakers were fixed to the canopy frame on the port side using the brackets supplied with #6 x 20 mm S/S self tapping screws. 

When finally installed after painting a copper wire tie will be installed over the hammer end locating tab just to make sure that it cannot escape in operation.

Pilots Canopy Breaker

Comment

Hope to never use it

Canopy - Restraint

This blog cover the installation of a canopy restraint

Overview
One of the issues created by the strut is its limited capacity to hold the canopy in a wind. This issue was raised by Franco from Flying Legend on the last visit.

Construction
A 3/32'' cable was selected for the task of restraining the canopy when opened using the existing canopy roller attachment and another point on the canopy spreader for attachment.

The existing pivot needed a machined swivel point from aluminium to allow the cable eye to swivel in normal operation. This required a slightly longer AN3 bolt to be installed with the swivel. 

Restraint attachment

Upper spreader before 
installation

The lower cable restraint was fitted to allow the attachment point to be determined with the o/a length set to hold the cable under tension by the strut when open. 

Once the mounting point was located it was drilled 3/16'' then the swivel was fitted and operation checked. The next issue was to spread the load on the spreader and to prevent the it from being crushed when the bolt was tightened.. 

A flanged shaft was machined 10 mm od allowing the bolt to be tightened allowing the cable to drop into the rear cockpit while not crushing the spreader. 

The cable would initially coil up but after being under tension for a while dropped neatly behind the roll bar.

Comment
Works as planned and in review it actually looks like it was designed not developed.

Another small job finished -- Woo - Hoo..!

Canopy Mod - Part 1

This blog covers locating the canopy in the fuselage and solving the problems created by the installation of the gas strut and is for record only.

Overview
With the latches installed  the movement to starboard of the canopy frame created by the gas cylinder had to be corrected.

It was found that if the the cylinder was removed all the gaps and alignment with the front cowl were correct, confirming that the cylinder was the cause of the alignment issues.

With the cylinder reinstalled and canopy closed it all moved to starboard but if the frame was pushed just past the front hinge a substantial correction occurred.  After a lot of thought it was realized that the cylinder now hinged the canopy frame at the rear with all the clearances appearing at the front hinge.

What was needed was a means to counter the 14 kg of side thrust. While lifting the canopy up and down and considering options it was realized that the inside face of the canopy was close to the roll cage - had a ridged mount.

Installation

Test wheel and longer locating pin

After marking out the location of the base of the frame just before the hook was engaged the location for a hole was marked and drilled through the roll cage frame. This process was difficult requiring the use of a small battery drill to penetrate the hard spot on the front face.

Note: The battery drill slow speed allowed the drill bits ends to survive the pressure required.

An old rubber caster wheel was wrapped in tape, fitted and the canopy lowered - joy of joy every thing was back in alignment on the port side and at the front and rear. There was still a issue at the front hinge but it was felt the installation of the locating pins would address that issue.

A new longer brass pin was installed at the center and with the nose of the hook dressed the canopy closed one handed but inspection at the front and rear showed that the gap between the front cowl had opened up and the rear closed. 

What caused this ?

Numerous adjustments and test showed that the canopy would open and close while picking up the center pin but the front and rear pins were out just slightly. At this point the center pin was removed and everything returned to normal, it was realized that the canopy was being push out of shape by the center pin.

The most likely cause was the new spreader / cylinder attachment with gussets added to control the torque created by the cylinder attachment. Where the original spreader had no ability to affect the frame shape the the new rigid spreader did and locked it in. When these were added no relationship to the locating pin was taken into account, this explained why all points were just out - a new shape had been created.

Spreader & Gussets

Button length determination
and rear button installed

It was decided to start by fixing the canopy's relationship to the fuselage fore and aft before reinstalling the pins. Two holes were tapped M3 in the front cowl frame and temporary Bakelite buttons fitted, next blue tack was fitted and covered with glad wrap and the canopy closed. 

The height was measured and a new buttons were machined and fitted, this process was repeated at the rear leaving about a total of 1.5 mm gap between the front and rear buttons.

The front buttons ensure that the frame squares up as its closed with the latches operation re-checked before moving onto the next task.

The final task was to refit the pins but to reuse the original locating holes required a new mounting point for the center pin. A piece of 25 x 3 aluminium is was fixed in location to the longeron using thin double sided tape then the location of the pin marked using the same technique used originally. 

Revised attachment

The aluminium was anodized then fixed using M4 x 12 hex head screws with the pin fixed using an M4 counter-sunk screw, refitted, tested with the same technique to be used at the front and rear.

Comment
Why all these issues  - probably an operator error - no excuses offered.

Next job is to install the correct wheel and guide cam but right now it works well in fact until the rear hinge was added it could be closed by just pressing down on the canopy with the front hook opening and closing the mechanism on the way down but with both hooks in it closes easily with a reassuring solid thunk after a firm push on the handle..!

Canopy in the 50% open position and balanced

Nearly there..!

Canopy - Latch

This blog cover the installation of the canopy latches.

Overview

The original opening in the side panel for the pilots latch actuator was totally inadequate and a larger opening was required as shown below with a cover to be fabricated later. 

Opening showing brass rubbing plate with the polished area 
showing mating faces with the handle flange

Latch Location
To determine the front latch pins relationship to the hook two AN4 area washers and washer spacers were fitted to the threaded rod then a series of lock nuts fitted allowing the assembly to be adjusted until the hook landed on the center of the assembly.

Verner's were then used to determine all dimensions with the rear pin location fixed no measurement was required.

Front Latch Installation
The original aluminium latch had to be move out into the cockpit about 10 mm supported only on the M6 threaded shaft. Rather than add washers a single piece brass latch was machined with a 1.5 mm fiber washer placing it about 0.005'' from the brass rubbing plate [shown above]. 

Once the correct position was established the brass latch was fixed to the shaft using high strength Loctite.

Note: The intent is to transfer uplift load via the stringer face and the M6 shaft. 

Front Latch Pin

The hook was installed after begin located from the inside of the cockpit using the latch as a reference. Its location is critical as it has to allow the hook to engage with the latch pull fully back and then allow the latch to engage the hook when closed. Initially fixed with four [4] clecos in a triangular pattern to allow the operation to be checked

Rear Latch Installation
The rear hook required a 1.5 mm spacer behind it to clear the latch flange and was located as described for the front latch.

Rear Latch Pin

Note: The M6 threaded rod at the rear was not long enough and the brass latch was used to remedy this issue - make sure there is about 30 mm projection from the face of the stringer then trim as required and the factory catch will fit correctly.

Latch
Operation was checked from the outside and adjusted until both hooks engaged smoothly by using a fine file to adjust the length of the nose of the hook along with the entry ramp only with relation to the latch pin. Only the lightest of dressing is required if the geometry is set up correctly at he start

Both hooks were fixed using tri-fold 4.8 mm pop rivets in a belief that these will resist side loads in a superior manner compared to pop rivets in the fiberglass side.

Note: The smallest tri-fold available is 4.8 mm

Handles
The handles were removed from the original latches with a razor saw and then machined square for re-installation onto the brass latches. Holes were drilled at the ends to allow a Tommy bar to be used to lock up the assembly.

All handles will be coated with liquid red plasti-dip with each component dipped twice [min] to achieve suitable coating. The finished coating creates a tough soft grip but once opened the contents has a limited life so it will be done with a lot of other items at a later date

Comment
Worked as designed with adjustments - see gas strut install re alignment issues.

Why the front latch had to move so far is unknown.

Canopy - Struts

This blog covers the addition of  gas strut aid lifting and holding canopy open.

Overview

ERRES the Brazilian dealer's Tucano installed a gas lift cylinder to support the canopy when open. The factory forwarding the images below as a reference with a cylinder specification of 150 mm stroke / 150 N force mounted onto a commercial 50 x 25 aluminium extrusion.

ERRES

Installation
The first problem was availability of a suitable length of extrusion with only 6 meters offered by a commercial distributor so it was decided to fold two 50 x 25 channels from 2024-T3 x 0.020'' aluminium sheet which is practical for the hand bench folder.

A series of 20 mm holes at a 80 mm pitch were drilled and flared on the front side to achieve a small amount of lighting and stiffening. Holes were drilled on the opposite face to provide socket access to the cylinder nut and a power cable for the passenger I-Pad or other device. 

Note: Weight was a major part of the decision with the fabricated channel & doubler's weighing in at 160 g versus 700 g for the extrusion [3 mm wall thickness].  All weights estimated.

The first task was to remove the original spreader that was now inadequate for the loads created by the gas strut. After removal the channels were assembled by riveting the flanges together using 3.2 mm pop rivets pitched at 40 mm. 

Next the assembly was trimmed to match the profile of the original and as there had been brackets previously installed it was decided to reuse them and add additional ones on the opposite face.  A packer [0.030''] was placed under both ends at assembly to allow the end of the spreader to move freely across the frame and to create a gap between the fiberglass and spreader.

With the front clecoed two new brackets were installed at the back and both the frame and spreader drilled. All brackets were secured to the frame using 4.8 mm Tri-fold rivets then fixed to the spreader with 3.2 mm pop rivets. 

Note: The smallest tri-fold available is 4.8 mm

Aluminium 2024-T3 0.030" gusset was added at the point of cylinder attachment spreading the load with another 0.020'' triangular gusset at the base to control the torque. Another was added on the port side to stiffen the overall assembly.

Note: ERRES used an aluminium angle extrusion as an attachment with high density foam backing to solve the problem of the slight angularity of the canopy side - this is a tidy solution.

Reference only

Trial installation verified the geometry and after tweaking the dummy it was re-made using a piece 45 x 20 x 1.5 aluminium extrusion fixed onto the spreader bar with four [4] x 4.0 mm stainless steel pop rivets. Commercial aluminium was used for convenience and ductility over aircraft 2024, there is a little flex when opening up to the cylinder stop.

All attachments to the gas strut were treated with Loctite thread lock at assembly with the clevis on the cylinder using a reinforced nylon and metal locking clip with a engagement of about 10 mm onto the cylinder - refer notes in comments.

Gas strut assembly

Note: The 343 mm dimension came in at 335 mm and the cylinder has about 10 mm travel left - why ? - the geometry shown is an estimate only of the actual shape. All rivets were primed before riveting .

When installed a problem was noted on the starboard side, the canopy was pushed out about 5 mm plus from the side of the fuselage, it had been aligned as enough filling and sanding had been done previously but it was realized that thrust [140 N] created by the cylinder geometry was creating the problem. 

As a result of this thrust component the center locating pin and canopy latches now do not line up by about the same amount. This is now a issue for this project requiring some additional guidance for the canopy to place it where it has to go.

Comment
Once the drawing geometry was verified it became an assembly task however replacement of the original spreader created additional small alignment issues and will be covered in another blog. The balance with 15 kg of thrust is excellent with the strut balancing the canopy at about 50% closed

The cylinder used has a 6 mm shaft, doing it again would have selected an 8 mm shaft model - use of thread lock is critical as these struts can undo themselves as they do not use a lock-nut.

A safety cable will be added around the strut using 3/32 cable because if the strut was ever to fail at a connection from a gust of wind, the damage would be unimaginable as an open canopy is a huge heavy bucket...!

Doing it again I would look at the ERRES method of canopy attachment and install all the components before fitting the canopy leaving its as late as practical, it's the frame that shapes the canopy but once it's fitted access becomes the real issue, especially one up.

Canopy Skirt - Part 3

This blog covers the T1 canopy skirt

Manufacture

With the shroud roughed out in Part 5 , it was refitted to create the final shape but before doing that it had to be in a fixed reference to the frame. With the skirt positioned correctly a series of 3/32'' holes were drilled into the frame to allow cleoces to be used. When doing this a number of thicker sections were noted when the cleco could not close after insertion.

This will required a rethink on how the skirt will be attached.

All edges were dressed to match the line of the canopy frame using a combination of half round bastard files and 80 grit aluminium open cut paper on blocks. Once the straights were completed the corners were developed by cutting cardboard templates until they fitted the frame and then profile transfered to the skirt for filing. The bottom will be done last once the seals are fitted with the catches.

Fitting clecos with the insert showing the template used to transfer the
angle for the band on the other side

Additional templates used to shape the corners

Curved template to join both verticals - template transferred to other side to create a symmetrical profile. A piece of  cardboard the same width as the verticals was used to create the radius on the front side

Skirt after first coat of high build primer was applied then sanded back
Next job is filling with lightweight macro

Canopy Skirt - Part 2

This blog covers the manufacture of the canopy skirt

Manufacture
After completing the cowl re-work the canopy was closed and re-taped off using brown packing tape with all the skirt lines re-established to allow glassing.

Canopy re-taped

The cloth was cut into panels and laid across the canopy, taped down to prevent unwanted movement. Two separate sheets were requires as the canopy is over 1200 mm over its perimeter at its center.

Laying up two sheets cloth

The epoxy was mixed in small batches in disposable cups then brushed onto the fiberglass cloth starting at the top, allowed to run down the cloth while being squeegeed through the cloth using a soft spatula to create a dry finish with the minimum weight of epoxy. The epoxy was spread to go past the black guidelines on the packaging tape to allow for final hand profiling.

Port/Starboard view of cloth after epoxy has been applied [brown area]

Note: Scrap pieces of 5 mm foam core proved to be ideal squeegees - soft but firm - disposable.

Once the first coat was completed the second layer was applied and the process repeated and then the same for the third.

The completed layup was now allowed to cure for 24 hours.

Skirt Removal
The skirt was now removed by applying a steady pull / lift at one corner allowing the skirt to peel away from the packing tape and was repeated from all for corners until the skirt released. The pliability of the skirt at this point was critical as if it was ridged it may have been impossible to removed.

A Dremal motor tool fitted with a plastic cutting disc was used to trim the waste leaving enough waste for final profiling by hand. Cutting was done on the aircraft very carefully,

The skirt is refitted and tapped back onto the canopy to fully cure over a week. 

Skirt rough trimmed ready to be refitted to canopy
The skirt is floppy but is is anticipated that it will 
stiffen with a application of macro.

Skirt refitted ready to be taped and fully cure
Insert show the profile at the front of canopy

Comment

The finished item is a bit more flexible than was expected but it did allow removal as this was one of the major concerns. I have used this technique before but not on this scale. The skirt may stiffen up when fully cured and macro is applied - standby.

The view from the hangar at Rylstone Airpark
Time for a beer..!