Month: October 2015

Covering Canopy

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Before covering the canopy I wanted to ensure there is enough room for the fabric between the canopy and fuselage. I checked by placing a flashlight inside the fuselage and looked at the seam.

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I did need to do a little sanding to get a nice even gap but it was not too much work.

I am only covering the front portion of the canopy. The 1/4″ ply at the rear is too thin to bother with and the bottom RS-10 is covered by lexan and hinges.

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Turtle deck and canopy meet
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Canopy hinge

I have been thinking of painting the bottom 1″ or so of the lexan white so it will blend into the fuselage better and hide the ugly blocks that it attaches to. That would cover these fabric free areas too.

There really is nothing special about covering the canopy, just a little tricky cutting around the blocks.

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Now it just needs primed and painted.

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Root Rib Opening

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So I have access to the root attachment points on the wing a couple holes need cut in the root rib. I cut some 1/4″ sticks and put them around the perimeter of the area I want to cut out then used the flush cut router but to cut the hole.

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The guests did a great job holding the sticks in place.

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After cutting both holes it looks like this.

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After removing the sticks the inside looks like this.

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Covering the Top of the Fuselage

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Covering the rear turtle deck was a little frustrating because some of the stringers bowed when the fabric was shrunk. To correct this I put some MEK to loosen the glue. Then pushed down on the fabric next to the stringer to pull the fabric. Let the glue dry, release and shrink wrinkles with iron. To ensure the stringers are straight I used some duct tape and string.

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Check if stringers are straight

After getting the stringers straight and admiring my work I pulled out a knife and made a big slice in the nice new fabric.

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Cut fabric for BRS bridle exit

If the BRS is ever used the left bridle will rip out of the fabric. To make it a little easier to rip out the fabric is cut them patched. After patching and shrinking it looks OK.

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Patch over BRS bridle

After the first coat of poly brush the fuselage looks good.

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Fuselage

Covering Gear Legs

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Asked David at TEAM if the landing gear legs need covered and he replied that it was optional. I decided to cover them, used one piece of cloth just like the rudder or fin.

I made sure the seam was on the bottom to help hide it.

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Landing gear leg

The outside looks great with no seams.

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Landing gear leg

I just need to do a little ironing and they will be ready for sealing.

Cockpit Opening

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This whole time I have been contemplating what I wanted to do with the cockpit opening. I decided to round over just the top edge and paint the top and sides white.

I think it looks nicer and brightens the inside a bit even with just one coat of prime.

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Turtle Deck Opening

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I happened to have a piece of 1/8″ plywood scrap that was the perfect size to make a panel for the turtle deck opening. After cutting it out and varnishing it I think it looks great.

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Turtle deck panel

The slots are for the seat belt shoulder harness.

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Turtle deck panel seat belt

This does sick out past the rear spar carry through so I glued a block to take up the gap.

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Panel support block

To hold the panel in place I glued a tab on the back of the top.

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Panel retaining tab

Two studs were added at the bottom to hold the panel in place.

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Panel mount stud

Two thumb screws attach the panel.

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Panel retaining screws

Mounting the Radio

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After sitting in the cockpit trying different locations I decided to mount the radio on the dash. I had to make a small spacer of 1/8″ ply because the back of the radio is recessed where the screws are located.

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Spacer for radio
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Back of radio

It fits well in this location with the modified Yaesu adapter I made.

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Radio mounted

This location did block one of the two switches I had on the dash and the one unblocked switch cannot have a cover because the radio adapter keeps the cover from opening. I plan to enlarge the blocked switch hole to feed the radio wires through the dash. I’m undecided on what I want to do about switches. I really only need one switch but if my generator fails it would be nice to be able to turn off non-essentials to preserve battery power.

At this time I will go with just one switch next to the starter key. The dash is looking really nice so far.

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MiniMax dash with radio mounted

Yaesu Radio Adapter

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The Yaesu radio adapter for my MicroAvionics powered radio interface sucks. It sticks straight out the side blocking access to other parts of my dash.

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MicroAvionics MM014DD same as Yaesu CT-91A adapter

The Yaesu came with a really nice adapter but it was made for general aviation connectors making it useless for the MicroAvionics powered radio interface. So I cut the general aviation connectors off of it.

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Yaesu SCU-15 headset adapter with headrest ends cut off

Dropped by Radio Shack and picked up a 1/8″ female stereo cable connector. The white wire connects to the tip and of course the braid connects to the ground.

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1/8" stereo female jack

The other connector is a 3/32 and the Shack did not have any so I stole the connector from the MicroAvionics adapter. Red wire to tip, black to center and braid to ground.

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3/32 female stereo jack

I cut down one edge of each connector to ensure they both fit onto the MicroAvionics MM005 interface cable.

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Cut down to fit MM005
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Connect adapter to MM005

Before:

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Yaesu FTA-550 with MicroAvionics MM014DD

After:

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Yaesu with modified SCU-15 adapter

G-CCAJ crash report

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Awhile back flydog posted an accident report on lonesomebuzzards.com for G-CCAJ. The crash was caused by pilot error but the investigators pointed out two things related to the shoulder harness that seem rather significant.

The most significant thing the investigators point out are the broken shoulder harness cables and why they broke.

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This picture is NOT licensed under Creative Commons and was copied from the G-CCAJ accident report under fair use

The report states that the cable broke where they make a 90° bend in the elevator control bracket.

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This picture is NOT licensed under Creative Commons and was copied from the G-CCAJ accident report under fair use

The suggestion was to change how the cable is mounted to maintain a proper bend radius as recommended by the cable manufacturer.

The other noteworthy item is that the builder did not attach the cables to the shoulder harness according to plan. Instead of one cable looped through the eyelet on the shoulder harness using a thimble this builder has simply put a thimble on the end of each cable and then connected both cables and both shoulder harness with a single shackle. This turned out to be a potential improvement. The investigators noted that this likely contributed to keeping the shoulder harness from slipping off the pilots shoulders.

Not wanting my safety devices to fail when they are needed most I decided to learn from this accident and improve my airplane.

I first started with the elevator cable bracket at the rear of the fuselage by drilling four holes. Two on the top and two on the front.

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Elevator cable bracket drilled for shoulder harness cable

I then cut off the excess material the is not needed.

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Elevator cable bracket

Next I installed the thimbles for the cable.

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Installing thimble for shoulder harness cables
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Both thimbles installed

Both cables were attached and crimped then installed into the fuselage.

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Cables crimped and bracket installed

On the other end both cables were attached to both shoulder harnesses. Getting both cables the same length was a little difficult.

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Should harness attached to cables

Prepare Rear Turtle Deck for Covering

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Some tasks will be much easier if they are completed before covering the rear turtle deck. The first item is routing the left bridle under the center four stringers. This is necessary to ensure the left bridle is on top of the seat belts and so they can easily tear through the fabric when deployed.

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Clamped bridle to stringers holding them in place

Next I used a couple drops of CA to glue some 1/16″ plywood calls over the bridle. These need to easily break away, the fabric will hold them in place, the glue is to keep them from falling off during covering.

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Plywood caps over bridle

After the glue dried I sanded the caps to make smooth transitions. Next bolts were fastened to the BRS mount using some thread locker. The top of the bolts will be inaccessible later in installation so this makes it easy to tighten the mounting nuts later. The gap under the mount created by the nuts also keeps the BRS Velcro straps from being crushed.

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BRS mount

Since the rocket mount was relocated it was bolted in place using thread locker.

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Launch tube mount

The BRS pack was attached to the mount with the Velcro straps.

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BRS assembly

The pack can be installed through the front turtle deck opening, that will be important for future maintenance but it’s much easier to remove the break away stringers and install it through that opening. Washers were placed on top of and under the wood supports and fastened with lock nuts and thread locker.

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BRS installed

The upper bridle was bundled with some wire ties.

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Upper bridle

A hole was drilled into the bulkhead behind the chute and the upper bridle held in place with a wire tie.

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Upper bridle fastened to bulkhead

One end of the upper bridle was connected to the parachute link.

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Upper bridle connected to link

The link was closed using thread locker.

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Thread locker on link

The other end of the bridle is held in place with a wire tie.

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Link closed

The other link was fastened to the white strip on the other side of the pack using wire ties.

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Attached link to white strip

The end of the upper bridle was attached to the link.

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Upper bridle on second link

The right and left bridle will connect to the link as shown below but that step will be performed at a later date.

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I did not like how the seat belt shoulder straps flop around hanging on the BRS. I added a dowel to the two center stringers and used two wire ties to support the seat belts. This is just to hold them, not for any structural purpose.

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Shoulder harness support
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Shoulder harness

You might have noticed that the seat belts are not attached to the cables according to plans. To better understand why read the accident investigation report for G-CCAJ, you can find it here.

TLDR; attaching the shoulder straps together will help to prevent the harness from slipping off the shoulders during a crash.

In that crash the cables broke where they are mounted at the tail. To address that weakness I also modified how the cables were attached.

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These safety changes deserve their own article so expect more about this in the future.

The only remaining task before covering the rear turtle deck is to mount my comm antenna. It is nice to finally see this all come together.