Cockpit modifications

Hangar > SBach 342 > Modifications > Cockpit

SBach 342 pictures


Cockpit base Instrument panel Pilot Latches

Cockpit base

The wiring in the fuselage is fairly tidy but I find it distracting when looking into the cockpit so I decided to make a tinted base. I looked around for thin plastic and settled on some .25mm (0.010") lexan, which I purchased here in Ottawa at Sabic Polymershapes. To the shop!

Measure and cut out the base

Measure the canopy:

base diagram

Mark and cut out the base:

mark and cut base

Test fit the base:

test fit base

Mark and cut out another piece for the back:

back piece

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Tint the base

Spray tint on the base:

tint base

I used Tamiya PS-31 Smoke paint; I imagine automotive tint would work just as well

Test fit the tinted parts:

tint test fit

Add tint until it's dark enough:

tint darkened

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Instrument panel

One of the rules for IMAC competition states "A realistic three-dimensional human pilot and viewable instrument panel shall be appropriately installed in all Scale Aerobatic aircraft." Since the SBach didn't come with a panel, it was time to make one. The SBach 342 is a dual-control airplane and a solo pilot sits in the back, so I made the rear panel.

I was lucky enough to find some panel images and pictures of the actual cockpit online. I made panel outlines of various sizes and placed them under the canopy to determine the best fit. Choice made, it was time to build the panel box. To the shop!

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Transfer the panel shapes

Trace the panel face onto a balsa sheet:

trace panel face

Trace the back of the panel:

trace panel back

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Assemble the panel

Cut out and glue together the front, top and sides:

glue front, top and sides

The depth of the sides and top were estimated by eye based on the cockpit photos

Glue on the back:

glue panel back

Add some internal reinforcement:

add reinforcement

I added reinforcement due to the stress I would place on the box when heating and stretching the covering

Sand the corners of the panel:

sand panel corners

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Cover the panel

Cover the front in white:

cover front

Cover the top, sides and back in black:

cover top, sides and back

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Apply the graphic

Print and cut out the panel graphic:

print and cut graphic

I printed the panel graphic with an inkjet printer and sprayed it with a clear coating; look closely and you'll see my registration letters and the IMAC Basic sequence for 2013

Glue the graphic to the panel:

glue graphic

I used a thin layer of carpenter's glue

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Install the panel

Place the panel in the cockpit for a test fit:

test fit

Glue the panel into the cockpit:

install panel

The block lifting the panel up from the canopy bracing is necessary to clear the cockpit base

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Pilot

The pilot of the SBach was, like the plane, a little the worse for wear. Time for a new one. To the shop!

Remove the old pilot

Use a razor blade to separate the old pilot from the cockpit framing:

remove old pilot

Take a close look:

look at old pilot

Your flying days are over, my friend

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Remove the old pilot

Install the new pilot:

install new pilot

Great Planes GPMQ9005 Pilot 1/3 Sport Red

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Latches

I became interested in canopy latches after reading a thread on Flying Giants. The end pull latches from F3A Unlimited came highly recommended and I decided to go with those.

A first look:

Canopy latch

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Next step was something I could attach to the canopy to engage the tabs... Ultra High Molecular Weight Polyethylene (UHMWPE) fits the bill perfectly - I picked up a 3/8" x 3/4" x 24" bar from Lee Valley:

New parts - UHMWPE bar, 3/8 in x 3/4 in x 24 in

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Next step was a plan:

Canopy latch setup

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UHMWPE doesn't take pen or pencil marking very well... luckily, I have this marking gauge:

Handy marking gauge

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Once the lines are marked, a bit of blue Sharpie shows up fine and the blocks can be cut. I used the band saw:

UHMW - both blocks cut

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I used the band saw again to notch the UHMWPE blocks. The original blind nuts protrude a bit from the canopy mounting tabs so I made recesses for those with a 1/2" Forstner bit:

UHMW - Blocks cut and shaped

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First the port block was installed:

UHMW - port block installed

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Then the starboard block:

UHMW - starboard block installed

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I had to open up the original canopy tab slots quite a bit:

Canopy tab slot opened up

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There's a reinforcing block a couple of millimetres thick where the original canopy bolt passed through, which offsets the canopy tab. The latch needed a plate of the same thickness - salvaged plywood from orange crates fits the bill. Clamped and glued in place:

Port latch mounting plate - glued and clamped

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Another one for starboard:

Starboard latch mounting plate

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I wanted to take some measurements of the latch before I started making holes in the fuselage. The spring is very stiff and it's a job to hold it open and measure at the same time... a spare piece of UHMWPE came in handy:

Latch - blocked open for measuring

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The plan dimensions of the latch, open and closed:

Latch plan dimensions

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With the measurements in hand, I made a template through which I could push T-pins to mark holes through the side of the fuselage:

Latch pin location template

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Template firmly clamped, two T-pins were pushed through from the inside:

Second T-pin through

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Here are the end points of the latch handle travel:

Port latch - end points marked

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The covering for the endpoints was removed with a brad point drill bit:

Port latch - covering removed with 1-8 in brad point bit

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Holes were drilled:

Port latch - holes drilled

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The covering between the holes was removed:

Port latch, centre covering removed

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And the wood between the holes was removed (a little rough, but I cleaned it up with some small files later):

Port latch, rough opening

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A test fit of the port latch:

Port latch - test fit

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Time to mark the holes for the screws that would attach the latch to its base plate. I used a nail to mark them:

Port latch - marking the holes

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If you look closely, you can see the marked holes:

Port latch - holes marked

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The holes (all ten of them) were threaded with a #0 brass screw:

Port latch - forming the threads

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A little CA to harden the threads:

Port latch - CA into the holes to harden the threads

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The #0 screws and flat washers were assembled:

Port latch - 10 ea #0 brass screws and washers

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All of the screws were installed. The washers are a little crowded but it's all good:

Port latch - view from the inside

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Here's a look at the brad point bit taking off the covering on the starboard side. It works best if the bit is spun by hand counter-clockwise; the spurs on the outside of the cutting head will slide right through the covering without tearing:

Starboard latch - removing the covering (spinning the bit CCW by hand)

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To mark the pin engagement hole on the port side UHMWPE block I started by blocking the latch open with a scrap:

Port latch - blocked open

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A little tape over the block to register the pin:

Port latch - tape to register the latch pin mark

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I put the canopy on the plane, pressing down to ensure no gap at the cockpit rim. Then the latch was unblocked and the pin pushed into the UHMWPE block to register:

Port latch - latch pin registered

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A hole was drilled at the mark:

Port latch block - hole drilled

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And the engagement was tested:

Port latch block - testing the engagement

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After the process was repeated for the starboard side, the installation was complete (and yes, the original screw holes have been covered up:

Latch installed complete!

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