Spruce To Rebuild The Monoplane Wings For Fly Baby

 In January 2020, pre-Covid, I found one of my rear spar blanks for my 1926 WACO NINE project was defective.  I also drilled a hole in the wrong place on another rear spar,  I ordered 2 new spars from Aircraft Spruce, not realizing 1 1/2 years later they wouldn't even be able to give me an expected date for them to have spar quality spruce.  While I was at the Antique Fly-in, Blakesburg 2021, a fellow Fly Baby builder, Kurt Gubert told me about an old lumber yard in Detroit who had some spruce that might work for my WACO spars and a new set of monoplane wings for our Fly Baby

Our Fly Baby is currently a Biplane, but it's licensed to switch to Monoplane wings, or back, with a log book entry.  Unfortunately the wings were ruined in a hangar fire years ago.  One of my projects is to rebuild the wings, but I need more spruce.  I want the monoplane wings because it's easier to trailer to events.  The monoplane wings fold or unfold in about 5 minutes.  That was the reason Fly Baby won the EAA design contest back in 1960.  The biplane wings take at least an hour each way.

Before you get crazy, Sitka Spruce is a small part of the several woods they stock and it has not been Certified as spar quality wood, that's up to you to resolve.  A good reference is ANC-19, Wood Aircraft Inspection and Fabrication.

That lumber yard is Public Lumber.  They've been there since 1927.

They're at 7 mile and I-75.  I took the picture of their store form the other side of 7 Mile Rd.  Look to the left 90 degrees and there is the entrance ramp to I-75 northbound.  It is in Detroit, in a residential neighborhood.  I met Craig and Tom, both super to work with.

It's a real lumberyard and full-service millwork facility, the smell of fresh wood, and the sounds of cutting and milling.  They even make their own custom cutters for their millwork.  People after my own heart

The spruce is in the lower bay of the rack at the left of this picture.  The boards are rough saw, 2" thick, 6" - 12" wide and mostly 16' - 20' long.  

They left me to sort out what I wanted.  The aisle is about 12' wide so it takes some thought to pull boards all the way out.  I had a great time examining and restacking boards.  I believe I found enough wood to make my WACO Spars and rebuild the Monoplane wings for our Fly Baby.  It was very fairly priced and I was dancing happy when I left.

It was cool when I got there.  As I worked and warmed up I took off my sweater, Christmas present from my wife.  I left it setting in the bay above the spruce with a tape measure I found laying under the rack.

I went on from there to visit my parents up by Flint.  The next morning I realized I'd forgotten the sweater.  Tom boxed it up and shipped it to me.  Thanks Tom for saving me from some serious dog house time.

I borrowed my son's Transit van to pull the Fly Baby trailer.  It's much nicer than my 24 year old Chevy van with 355,000 miles.

The weather was sunny and dry so I didn't worry about protecting the wood from the weather.  It all stayed strapped down and towed very well.

The round trip was almost 1,700 miles, well worth it.

The wood is safely home in my attic workshop.  

The next step is to pick out boards for the WACO spars.  Then the scary part, cutting them up.  Once I have the WACO wings done I'll start on the Fly Baby wings.

Rudder Stops Installed, New Upper wing Fittings & Upper Wing Hand Holds

I discovered a small problem when I installed the tail surfaces so I could locate the Nicopress stop on the cable.  My Nicopress tool won't squeeze the round stops, I thought it could.  I had to redo the cables with regular oval Nicopress sleeves.  They're designed to squeeze around 2 pieces of cable so you need a short piece of cable, about 2" to properly squeeze them as a stop.  I carefully cut 2 pieces of cable with the Dremel tool cut off wheel.  They worked fine.

 You need to position the short piece of cable so it doesn't stick out past the end of the sleeve where it hits the wooding block.  You want the sleeve hitting the block not the end of the cable.  This all would have been easier before installing the gas tank and center section so you can undo the cable from the rudder and rudder pedal to squeeze the sleeve.  The Nicopress tool handles open too wide to use inside the fuselage.  Fortunately I had an old manual tool from my hang gliding days.  It was awkward but it worked.

The plans call for a 1" gap at the trailing edge of the Elevator when the pedal is pushed to the stop.

The other problem I ran into was the lack of a hand hold on the upper wing center section.  Once I had the wings on I decide to sit in the cockpit for a picture.  My foot snagged on the edge of the cockpit getting in.  I lost my balance and landed on the ground on my injured hip, major pain, and cracked a rib, more pain.  I had removed the old machine gun mounting system without realizing I had used it as a hand hold to stabilize myself getting in and out of the cockpit.  I hold onto the cabane strut with my right hand but I'm tall enough I can't reach the other strut under the wing with my left hand.  The hand grabbed wildly for something on top of the wing which was no longer there.  Even if the gun was installed with the new mount there would have been nothing to hold.

 Before installing the hand holds I removed the wings and moved them to the airport.  With the wings off I could see the Upper Wing Attach Fittings were bent at the center hole.  I decided to remake them from 0.125" steel instead of the 0.095" on the plans.  The bending had to do with a slight compression of the wood on the center section due to tightening the bolts.  This made the fittings closer together on the center section.  When the wing panels were installed the outboard ends of the fittings bent up slightly.  It didn't seem like much with the wings on but looked much worse with them off.  I've put some washers under the fittings to shim them up to prevent the bending and feel safer with the thicker steel.  Only the top fittings seem to have bent.

The 2 small fittings on the left are for attaching the hand hold to the inboard bolt on the wing fittings.  I carefully marked the wing fittings and duplicated the hole locations so the wing bolts should all line up properly when reinstalled.

 The hand holds are made from painted door handles, big enough to fit my hand.  One end is bolted to the fitting which attaches to the wing with the fitting bolt and the other end is screwed to the trailing edge wood.  I used 2 #8 stainless steel wood screws 1 1/2" long.  There are some washers under the handle to screw holes to carry the loads to the wood and the fitting rather than the edges of the handle ends.

 There is room under the fitting for the bolt heads because the fitting sets on top of the wing attach fitting.  They shouldn't press into the fabric since you pull up on the handle in use.

OK the are a little odd looking but they work.  I don't need them pulling myself up out of the cockpit.  The cabane struts work fine for that.  They're just for stability getting your feet in and out of the cockpit.

Center Section Cabane Strut Leather Boots

 I needed some way to seal up the gaps around the Cabane struts where they pass through the cowling.  The old seals were a piece of aluminum with a plastic edge.  I wanted something older looking like these leather boots on the Bucker Jungmeister.

 I made each boot for the front struts from 4 pieces of Goat Skin.  I worked out a pattern using paper towel since it bent and formed the closest to the leather.  The pattern was drawn on the back of the leather.

The 2 inboard and 2 outboard pieces were sewn together.  Then those were sewn together on the aft seam.   I wanted to be able to install them without removing the struts, again so I needed a way to wrap it around the strut.

 To hold them in place I made an aluminum plate with a split at the front, so it can slip around the strut.  The front picks up 2 cowling screws and 2 Tinnerman nuts were added for screws inboard and outboard of the strut.

 The leather boot was glued to the top of the aluminum plate, slipped around the strut and under the cowling.

 Because everything is symmetric, left and right, the patterns work for both forward struts.

 I wasn't sure I wanted the seam in the front but it did make it much easier sewing it closed.

 The boot closes the hole nicely and has the look I was after.

The screws hold the plate snug to the cowling so it should be moderately water proof.

 For the aft struts I just made a plate with leather glued to it.  I couldn't come up with a simple boot design which fit snugly and would stay in place.

It closes the hole for the Monoplane landing wires.  I'll need to make some different ones to close all 4 holes when I put the Monoplane wings back on.

Wing To Fuselage Pitot Static Lines

 The last thing needed to hook up the Pitot and Static lines is to connect the aluminum tubing in the wing to the Nylon tubing in the fuselage.  It turns out there don't seem to be any ready made connectors for joining these different materials.

 I decided the solution was to do this like the connections at the Pitot Static Head using a piece of soft rubber hose.  Before making each piece of tubing a bead was crimped to each piece of tubing.  Then the appropriate nut and ferrule were installed on each end.

The hose was safety wired as before.

The aluminum tube for the static line was made a little longer so the hose would be clear of the nose rib hiding between the bulkhead fittings and the root rib.  The lines end about an inch inside the fuselage.  They're attached to elbows in the fuselage and will be joined to the wing when the wings are installed.

New Pitot Static Probe

The Pitot Static probe on the Fly Baby Biplane is mounted about 2/3 of the way up the left wing strut.  It's a home made probe similar to this factory one I saw at Oshkosh.  Our old one was made with fairly light aluminum for the mounting braces and screwed to the strut.  The light braces have been bent several times and just like on the landing gear water has gotten into the screw holes.  I decided I needed to make a new one of sturdier aluminum, that clamps to the strut, more like the factory probe.

The old one worked so the original idea was to just make a new mount for it.

As I disassembled it I realized I probably should just make a new one using some of the same concepts.  The old one was taped and safety wired together.

The tube connectors are pieces of 1/4" I.D. brass tubing which was splitting.

The probe tubes are separated by a piece of wood, which I liked.

The static probe was A piece of 1/4" aluminum tubing with the end hammered closed in a bullet shape, with a pattern of air holes.  To make a new one I used an Oak block to support the tube while rotating it and slowly hammered the end closed.  The tube wanted to slide along the block as I hammered so I leaned a piece of wood against my vise as a stop.  It worked fine.

The last, tiny bit of closing was done by hammering straight down on the end.

It was fairly smooth but I decided to lightly file off any slight bumps.  I aligned the tube at an angle with the cutting edges on a smooth mill file.  By gently holding the end of the tube between my fingers I was able to rotate the tube and nicely clean up the hammer marks.

It was easier to form this end than I thought it would be.

I prick punched a pattern of holes, 1/4" on centers, 3 holes on the 4 quadrants and 2 hole between each set of 3.

The smallest drill I have is 3/64".  The only chuck I have that will hold a drill this small is the little chuck on my angle drive.  I had just gotten this chuck a couple weeks before so it was my first chance to use it.  It worked out very well.

The hard part was deburring the holes.  I used a piece of 3/32" welding rod to work the burrs until I was sure I had removed them all.  It was mostly a matter of knocking them off or having them close the hole and then poke the hole clear until they all fell off.

The tube was bent so it would be parallel to the bottom of the upper wing, same as the old one.  The joggle in the tube is to allow a piece of soft rubber tubing as the connector.  I thought about using AN tube fittings but I wasn't sure I could make both tubes fit perfectly.

The Pitot Tube was formed like the old one but with a joggle to the side so the connector tubes would clear each other.  I also made it longer so the connector hoses wouldn't be beside each other.

For the block of wood separating the tubes I used a scrap piece of 1/4" spruce.  I used an Exacto Knife to carve notches for the tubes along the edges.  I also rounded the leading edge to be streamlined.  I just couldn't leave it square.

To help the connector hoses seal I crimped a bead on the end of the tubes using a hardware store compression fitting.  They sell extra rings so you only need one fitting.  You need to drill out the hole in the nut so it will slip over the bends in the tubes or you'll have it stuck on the tube.  You could put the bead on before bending, but I find it easier to bend and then cut the tube to length.

I also Alodined the tubes to give them a little corrosion protection.  I like the Gold Alodine better than clear for these things because I can see it working to judge when it's done.

To hold the tubes in position while I made the remaining parts I glued them and the wood block together with some 5 minute epoxy.  I used a piece of non-stick aluminum foil to wrap everything.  This minimized any trimming of excess glue and held the parts in position while the glue set.

The next piece was the strap which clamps the tubes to the strut.  I worked out the shape with a piece of card stock.  The aluminum is 0.032" 2024-T3.

After Folding it in half, so it would fit snug to the tubes, I Clamped it in the vise with a piece of 1/4" rod.  The piece of Oak has a 1/8" radius on the corner to make the bends to fit the front of the strut.

Back in the vise with a piece of 7/8" tubing to from the sides to the strut leading edge radius.

It makes a nice fit to the strut.

These pieces will replace the fragile side braces with some more 0.032" aluminum.  To help hold the tubes from coming loose in flight, I rolled the edge over to make a "J" shaped piece.  The length of the "J" section is less on the piece which hooks around the bottom than it is for the piece around the top.

The "J" shape fits snugly to the tube.

To form the hook edge I pounded the aluminum around a 1/4" rod to make a 90 degree bend.  Then I clamped the short end in the vise and continued to increase the bend in small increments until I had a 180 degree bend.  For each added bend you have to loosen the vise and rotate the part a little than hammer a few more degrees of bend with the wood block.  It works just be patient.

The aft ends were bent out, like on the clamp strap.

Then the second bend was marked to fit the strap.

The second bend was made to those marks using the piece of 7/8" tubing.  These side braces will get riveted to the strap to stiffen it all.

I trimmed up the braces, Alodined them, and glued them to the tube assembly.

The strap was glued and clamped in position before drilling the rivet holes.

I wanted the probe clamped to the strut without screws and with the ability to tighten the strap so the probe pointed straight forward.  For this I needs some little angle brackets on the sides of the strap, and also on a strap around the back of the strut.  This way I can pull the strap tight and adjust the screw on each side to pull the probe left or right as needed.

The brackets are made form some scraps of 1/8" x 1" 6061-T6 aluminum angle.  I drew cut lines and punched all the rivet and screw holes before cutting.

I didn't cut the parts off until I cleaned up one edge on the belt sander.  It's much easier to hold the stick than the little parts, which easily get very hot while grinding.

After grinding the first side, the part was cut off, the second side ground, the next part on the stick ground, etc.

When I Fit the first bracket on the strap, I realized the bracket on the back strap needed the screw hole 0.032" further from base because there is only 1 layer of aluminum vs 2 on the front strap.  Normally I make drawings to avoid remaking parts, but this was one of those figure it out as you go projects.

I needed to use flush rivets from the inside of the strap so I dimpled the aluminum and countersunk the bracket holes.  The dimpling would have been better with all the pieces apart but the front rivets had to be in place to hold the pieces tight enough.

The front half of the probe almost done.  I added a screw through the side braces and the block of wood to assure nothing comes apart in flight.

When I made the rear strap I realized I needed the front strap cut off at the back of the brackets to leave some gap for adjustment.

The finished probe.  I added a small piece of aluminum tape in front of the static holes.  I had done this on the old one to give a little turbulent flow past the holes.

Temporarily in position on the struts to make the tubes which connect the probe to the tubes in the wing.

The tubes were formed, and Alodined.

To secure them to the struts I lashed them on with cotton cord like I did on the landing gear legs.

3 coats of varnish fills the cords and glues them to the struts.

I filled the old screw holes and varnished over them.

To keep the probe from moving, I applied friction tape under the strap pieces.

To hold the Connector hose to the tubes, and assure a good seal, I wrapped them with safety wire on both sides of the bead.

I found it best to start at the free end of each to to assure I was close to the bead and still on the end of the aluminum tube.  I snugged the twisting just tight enough to slightly squeeze the rubber.

A few twists are enough to get to the other side of the bead and repeat the snug twisting.

The ends of the safety wire, as always, are folded over to help prevent injury on the sharp end.

I probably could have made the end of the Pitot Tube a little longer since the rubber tubes overlap slightly, the mistakes of not having a drawing.

In the end I like it.  It's solid.  There are no screw holes in the strut and I can adjust right or left if needed.  I also like the Industrial look, very cool.