Ribs on 1st Wing - Lower Left

 The first rib is on the spars.  Yeah!

I had to take a plane to the top of the spars in a few spots to remove a couple thousandths of wood.  Ah, the joy of a sharp plane.  My brother David is the expert on sharp hand tools.

 I was finally able to face-time my grand daughter to show her that her first rib is on a wing.  She's "Physical Distancing" in upstate New York.  She helped build ribs during Christmas Break 2008-2009.  She used the picture as part of her presentation to her Kindergarten class on rib building.  She's now stressing over SAT scores and which engineering college to attend.  They do grow up fast.

The Fly Baby in the background was reassembled and is back at the airport awaiting weather, viruses, etc. to get it back flying.  I had to move it out to make room for building the wings.  I also took some time last year to finish the attic, much warmer in the winter.

 Here is the wing with the rest of the ribs in place.  Everything fits perfect.  Time to start actual assembly.

I need a bigger workshop.  I think I'd rather build wings than a workshop.

Prepping Spars for Wing Assembly

The first step was to cut the tapered wing tip ends of the spars.  I had lots of ideas for how to cut these in ways which better control the cuts.  In the end I took the 7 1/14" circular saw and cut them by hand.  I kept the cut just outside the line and cleaned them up with a plane.  Spruce is so nice to work by hand.

My next task was to varnish all the areas where fittings will be bolted on.  All my reading says Oil Based Polyurethane Spar Varnish is the most flexible and longest lasting.  two coats were applied being careful not to varnish areas where glue joints will be made.  The factory did not varnish anything.  This plane was very much based on practices Bruckner and Junkin learned during WWI.  All that work needed to varnish the bits of wood in a wing didn't make much sense if the plane wasn't planned to be in service very long.

The funny thing is that they used a coat of Clear Valspar Varnish as a final finish on the fabric covering.  I assume it gave a nice shine.  Dope tends to be a dull finish.

Routing the spars reduces the their weigh, but it also reduces the wood to attach the wing ribs.  To solve this a piece of spruce gets glued to the spar web to bring the surface back to the level of the flanges.  The blocks get glued and nailed to the spar and the rib glued to the blocks and the flanges.  The small nails are used to hold things in place while the glue dries.

The front spars are routed 1/4" deep, so sticks of the the same 1/4" x 3/8" spruce used to make the ribs works for these blocks.

For the rear spars blocks made form 3/8" x 3/8" spruce are needed.  The flat space between the corner fillets is 7/8" wide.  Such short blocks easily split when driving a nail through them, so I made them 1 3/8" long to help.  This meant I needed to chamfer the the ends to clear the corner fillets.  I figured out I needed the chamfer to end 1/4" from the ends and to slope up 1/8".

I drew a guide line on the table of the belt sander at that 2:1 angle and marked a stop line to control the size of the chamfer.  It just takes a couple seconds against an 80 grit belt.  I do the grind on the fuzzy edge so I get rid of the burr while doing the chamfer.

The grinding leaves a little burr which is easily removed with the sander.  Trust me the factory did not worry about such things as fuzzy burrs.

Most of the line locating the ribs got removed with routing so I made a guide from a piece of 1/2" x 1/16" aluminum angle.  You line it up with the lines still on the flanges and the block sits next to the guide for nailing.

That was a clever idea but in practice I needed a couple more hands.  I found these little spring loaded clamps were perfect to hold the guide in place.  I normally use these when I'm working with aluminum because the rubber ends don't leave scratches.

The one closest to me has the latch handle pointing down because I found you can grip it kid of like a pistol, position it, and squeeze the handle to lock it in place.  The one in the back was easy to lock with my thumb.  This was easy enough, and worked well enough that it was worth the little time it took.

I'm a Resorcinol Glue guy, but I didn't work the webs down 'till they were perfectly smooth so T-88 seemed a better choice for this.

I mix small amounts by drawing 2 circles.  Some of you may still have an old circle template from drafting class.  Circles 1 1/8" diameter worked to last about 45 minutes.

The box makes a nice holder so the glue stays at the outlet end.

Post-it notes make a nice, throw away, work surface for mixing the glue.  I started with this 3" one and switched to a 4", much better.

The popsicle stick works well for mixing and, in this case, for applying the glue.  Get a big box of them.

I put a line of glue on the block and split it with the stick so it would flow out both sides more evenly, to assure a good joint.

The only way to nail these, or most parts, is with this handy, slightly modified, Great Neck Magnetic Brad and Nail Driver.  Really, take the link and go read my old post.  I love this thing.

I found 2 nails (3/8") and about 3/4" from the ends worked perfect.

All the front spars with rib blocks installed.

Once the glue dried for a day I used a metal straight edge to check for blocks that were a little high and ones with a nail sticking up above the flanges.  You find them real easy with a metal straight edge, just slide it along the spar.

For the few blocks which were too tall, I pulled the nails and carefully used the block plane to shave them down.  You just have to hold it firmly and stop it before you get to the flange.

Tall nails are easy to tap down with the nailer, or my cool tack hammer from 7th grade shop class.

When I made the guide I put a notch in the middle of it so it would work with both the front and rear spars.  The clamps just worked with the 1 1/4" rear spars.

Even with the longer blocks for the rear spars I still split about 10% of them.  I used one 5/8" nail in the middle of the block for these.

I also have the 2 existing rear spars done.  The longer Upper spar has the aileron attached to it so most of the aft side doesn't get sticks.  The ribs in that area end at the spar.

Lookin' Good.

I hope I remember all this when the other 2 spars arrive.

6 Spars Done

I set the spars on the saw horses to start varnishing where the fittings will go and to add the sticks in the routed areas where the ribs attach.  It looked so nice I needed a picture.

Aircraft Spruce say the wood should be there in April, then they'll cut the other spars.

Back to work.

1st Rear Spar - Routing Finished

 The first rear spar is done.  This is the upper wing spar.  The aileron attaches to it.

The aileron hinges set in the routed area on the aft face of the spar.  I left the spruce the full thickness on the forward face to give some extra strength to resist cracking.  That may cause a problem with the hinges which may need the bolt end longer.  The aileron spar is only 1/2" thick, same as the rear spar web.  My logic is that it's easier to make a new aileron if the spar cracks than a new wing.

I've realized I need to order glue and bolts if I plan to assemble wings.  Getting close.
I also need to check on my replacement spars.  I'd like to finish them while it's fresh in my mind how I've been doing all this.

First Rear Spar Started and More Thoughts On Routing

 I found there was a lot of leakage of chips even with the airflow in to the vacuum.  A little duct tape to seal the gaps really cut it down. I forgot to include the pictures in the last post.

 I tried using my small box plane to smooth the ridges left from routing.  It scratched the corner 3/8" radius so I mounted the belt sander and rounded the corners of the plane to about a 1/8" radius.  It solved the problem and is much quicker than sanding where it can be used.  It won't fit in the rear spars but works great on the front spars, which are now all done.

 I forgot to say, I'm using 3M Sandblaster 150 grit paper for the final sanding.  It works way better than conventional sand paper.

 To sand the rear spars I needed a block which fit the routed groove.  It turned out a piece of 2x4, I had cut in half, fit perfectly.

I discovered the angle I cut on the top of the rear spars was off slightly and I couldn't quite get the ribs on.  This time I made a gauge to set the angle of the saw blade.  I took 1/32" more off the short side.  When the 2 replacement spars arrive I'll do them correctly the first time.

All the front spars are done and the first side of a rear spar is done.  Looking good.

Some More Info On Spar Routing

I use this stuff on the window in my sandblast cabinet to reduce dust sticking to the window, due to static electricity.  It also helps on the window of the router.  I spray it on a soft cloth and rub it on.  The dust accumulates on the outside so it's easy to do.  No need on the inside.  All the chips blowing around keep it clean.  It's not magic but a couple applications make a big difference.

I also forgot to say I use 2 clamps across the side rail blocks to hold them snug to the spar.  You don't want them to move.  They don't need more pressure than what holds them on well.

Skil makes an optional attachment (RAS 130) to connect a vacuum for the chips and dust.  We ordered one on line but it came without the screws, which seem to be metric.  It attaches to the oval boss on the base and fits a 1 1/2" hose.  Until I find some screws I've made a dust cover which attaches to the base and to the 2 1/4" hose.

I realized there are two 1/4" holes through the base for attaching a guide mechanism.  I decided I could  use one of them to attach the dust cover with a piece of 1/4" rod.

I cut a piece of 20 gauge mild steel, scrap from making the OX-5 exhaust manifolds.  I punched a ring of 1/8" holes with the Whitney punch, split them into tabs with snips and bent them up.  They're to weld to the outlet tube.

The tube is a strip of 1 1/2" wide 20 gauge steel spot welded together.  It fits the vacuum hose nicely.

I positioned it in the the tabs so it was a little farther in than flush with the cover.

Ah the joys of a cheap spot welder from Harbor Freight.

The cover was bent to fit snugly to the base.

A 1/4" hole was punched to align with one of the holes and filed with the 1/4" chainsaw file to allow the steel rod to enter at an angel to the base.

With the cover clamped to the base, and a pin in the first hole to hold it's location, The second hole was center punched with a duplication punch in the rod passage.  This was the same basic process I used to locate where the first hole was to be punched.

A piece of 1/4" rod was cut a little longer than needed and locked in place with the retaining screw and washer in the base.

It works.  I did find I needed to duct tape some of the leaks around the edges to reduce the chips leaking out.  As a result I have very little chips and dust.  I still wear an N-95 dust mask to protect my lungs, but this really cuts down the mess.  When I find the screws I'll see if the factory part works better.

Today I finished the third front spar.  It's all working.