Battery Isolation

This blog covers installation of the battery and isolator

Overview
With weight an issue it was decided to look at one of the heaviest accessories on the firewall with the typical battery weighing about 5 kg [11 lbs]

A Odyssey 625 battery for a Rotax weighs in at 6 kg [13.5 lbs] offering 200 CCA and18A hrs capacity.

After checking various recommendations for batteries it was decided to install a Lithiumax Red Top Ultralight battery offering a installed weight of 500 grams [1 lbs] using the more stable LiFePo4 Lithium architecture which according to reports have none of the tendency of the earlier Lipo batteries to burst into flames.

A load analysis showed that the 15AH would be marginal in a emergency with a failed alternator so it was decided to double up. 

Installation
The battery mounts were fabricated from 0.020'' 304 stainless with the usual lighting holes punched through the structure, assembled using 1/8'' stainless pop rivets and fixed to the firewall with the same.

Dual batteries and isolator

Note: Retainer straps are yet to be installed and will be fabricated
using 0.015'' stainless steel but these will have to cut at the
local sheet metal shop to obtain a neat edge
Total weight 1.0 kg / 30 Ah / 220 CCA

While I trust all these reports on the new batteries if anything was to go wrong it's a spectator sport for the suppliers so it was decided to install a battery isolator to allowing the battery to be removed from the aircraft load in an emergency. 

The isolator switch body was modified to allow flush installation onto the firewall and then connected to the cable with the actuation ring fitted at the outer edge of the lower panel. 

A red/green led will be installed above the ring to indicate the switch position using the integrated contacts seen at the rear of the switch body when wiring is underway. 

I doubt it will be required but just in case.

Red ring is the switch actuator

Revolution RaceGear remote isolator

Repair revisited

This blog cover the additional work done to the repair damage created in transit from the airshow.

Overview

Best not talked about

Final inspection of the repair displayed unacceptable gaps between the skin and the rib at two locations.

Initially packers were added but the realization was reached that application of rivets created all types of issues

I had been too optimistic after the repair and now had to accept this task was at the limits of my ability but it had to be fixed to my satisfaction.

Rework
A lot of time was lost rethinking on this issue and putting pride aside this was as a tough job as this builder has ever undertaken. 

After a lot of soul searching it was decided to remove the tabs that were creating the issue's and rivet new ones on. This position was reached after fitting the skins to both sides, inspecting the fit it was concluded the core of the issue laid in the curves.

With the rib exposed the curved tabs were removed and dressed then a replacement set fabricated. To allow the component to be fitted the side was cut creating tabs on the mating faces and these were then drilled allowing three [3] rivets to be installed at the top and bottom with a couple in the middle. 

The original full length stringer doubler was replaced with two [2] 0.025'' 2024-T3 custom folded channels. These were tapered on the flanges and staggered to each other to create a smooth path for any loads to transfer between members. The flanges were riveted to hold the assembly straight while lining up the members.

New outer flange

Top fixing of new bulkheads

With the part ready the tab was slid between the bulkhead web and skin and with the location marked onto the web, next the holes were drilled and all the components clecoed to the bulkhead and then riveted. The operation was repeated until all bulkheads were modified, finally the skins were fitted but it was difficult to drill the align ribs for drilling from the skin side one skin had to be off to allow the necessary drilling to be undertaken. 

To create access the damaged port skin was cut open near the rib and fitted to the starboard side and that access allowed the operation to be repeated on the starboard side.

This is one idea that allowed the positioning of the rib correctly for pre-drilling

The jig was manufactured using the damaged skin, match drilled using the new skin and fitted to the aircraft, holes for the rib could be drilled, position checked
through the whole process.

Note: Each check involves the installation and removal of one of the side skins multiple times not to mention the installation of both skins to confirm alignment which consumed the better part of each day given to each task. A jig was developed as a result of the time lost doing this and not begin able to reach the rib to control its position for drilling

Blue Stuff
The aircraft was leveled using the water tubes  at points along and across the fuselage plus the the elevator stab with a small amount of weight applied on the elevator stab to tweek the alignment before riveting with the final task to pull rivets.

Note: Both skins are clone's of the original factory skins with all factory pre-drilled holes reused.

Mid-night and the lower skin's are installed
with the next skin to be installed for riveting

The final task next week is one final check, remove clecos and fill all the empty holes with pop rivets. 

Comment
How a small amount of damage in real terms had cost the builder 75+ hours of work. rework and more rework is hard to fathom. That this much time could be consumed and not achieve perfection is beyond me but the task was like a game of chess, every move had significance with unseen consequences and with each move, options reduced in a game with no visible guidelines.

The description of the work is at best in this case an overview and dose not go close in covering the time lost in fitting, re-fitting, checking and re-work.

Ready to close

Panel Cowl - Part 4

This blog covers the finishing of the instrument panel cover

Finishing

After priming imperfections were filled with blade putty, sanded smooth with 400 grit wet & dry. Next the exterior and 75 mm on the inside lip were painted using a  Satin Black spray can. When fully cured it was then rubbed back with 800 wet & dry, resprayed Satin Black then two coats of spray statin clear applied.

Fixing
The panel was fixed to the fuselage using the factory tabs fitted to the cowl bow using M4 rivet nuts installed preciously. The lower edge was fixed using four [4] M3 screws installed into an aluminium angle riveted to the fuselage longeron fitted with rivet nuts.

Edge fixing - typical both sides

Edge Protection

It was decided to add edge protection and a search on Ebay found the the profile shown below with a integrated hollow that would seem to offer superior protection over a rubber U channel. 

Link: 3M Car Rubber Edge Trim Black U Channel Anti-rub Mouldings Strip #60

If link broken google the description

Exhaust - Part 1

Blog covers the exhaust selection

Overview
One of the issues that this build is facing is weight gain in the engine bay created by the installation of the intercooler with a estimated weight of 3.5 kg.

After looking for alternatives and rejecting them because of weight with one at a 5.5 kg. Searching the net resulted located CFT Trading Sweden who stock a titanium exhaust that is 1.8 kg lighter than the standard standard Rotax exhaust at 4.0 kg. 

Removing weight from any aircraft is either a lot of work or expensive - in this case it's the latter but at least it just bolts in.

Exhaust system components

Titan Exhaust System
Examination of this image in conjunction with one of the supercharged 
UK Tucano has convinced the builder that this should fit without modification

The weight of a complete system (4 exhaust pipes, 2 3-way connectors, 1 muffler, 1 exhaust pipe from muffler, connectors and springs) is 2,4 kilograms and $AU2200 - as I said not cheap.

Comment
Are there any issues - we will find out in time. This is the last major component that needs to be purchased so no excuses.

Dorsal Fin

This blog covers the dorsal fin install

Overview
The fin installation was covered in the blog on Stab Faring leaving the final task of securing the fin to the air-frame.

Installation
The holes drilled in the previous blog that secured the dorsal fin with 3/32'' clecos were all enlarged to 5 mm and fitted with Countersunk thin sheet M3 rivet nuts. These allow the dorsal fin to be screw flush with the skin of the aircraft unlike the large flange type supplied with the kit.

Note: All these specialized items were purchased from Fastener Kits Online in Australia

Rivet Nuts installed in previous 3/32'' holes

Note: the large head rivet nut was installed in error and replaced

Fixing

M3 Wafer Screw

Fixing is always a issue with cheese head screws chunky, countersunk are not a practical option and the fin has to be removable for heavy maintenance, pop rivets are not a option.

Having used wafer washers previously, a quick search on the net located a supplier in China who supplies these screw in a bag of a 1000 M3 x 12 for $24 with free but very slow postage.

Wafer head screws fitted to port side

The screws have a profile similar to a 3.2 mm pop head rivet and using a 3.5 mm mounting hole allowed the dorsal fin to be secured tightly to the fuselage skin.

Profile Modification
The top edge of the dorsal fin had a flat edge and while filling the side faring with dry macro the excess was applied to the top edge and once it reached the plastic stage the application was adjusted by hand to resembled a radiused edge. Once cured a combination of 80 / 120 / 240 grit aluminium open cut paper were used to achieve a final profile. The rough edges were filled with blade putty and sanded with 120 / 240 aluminium open cut paper to a smooth profile.

Comment
Happy with the final result with the screws working as well as hoped.