Make a Rib

To try and spice this blog up a bit, I thought I would outline the process of cutting and fitting the rib parts.  I have already discussed my gluing-up process.

I apologize for the varying color balance of the photos.  The primary objective was to get the rib built.  I have various lighting sources in my shop, and the camera was thinking on its own regarding operation of the flash.  I am sure there are adjustments in the camera to force flash on every exposure.  But I was not interested in taking the time to figure it out. 

The very important first step is to clean off the jig.  Usually, the problem is just a bit of dust and wood chips.  It is very important that the capstrip snuggles down flat onto the jig surface.  It is also important to make sure no dried glue drips are lurking where capstrip will go. 

After cleaning things up, it is time to place the blocks.  This rib is an "aileron" rib, so it has both a nose block (shown in this photo) and an end block (shown in the next photo).  It is important to get the block fitted properly in the jig.

Here is the tail block placed on the jig in its proper location.  Due to a minor discrepancy in the jig used to cut these blocks, they all need a bit of adjusting to fit correctly. 

The first longitudinal member to be cut and fit is the bottom one.  It fits into a notch in the nose block at the front end.  The end of the capstrip is carefully marked to match the angle of the notch.

The tail of the longitudinal member needs to be marked for cutting, too.  This is not a critical dimension.  The capstrip just needs to extend beyond the last securing cam beyond the tail block.  The capstrip will be trimmed to final length after the first gusset is in place.

The bottom longitudinal is cut to rough length on my cute little miniature table saw.   This is a handy tool for rough cutting where both ends of the piece are longer than the throat of the band saw.

The angle on the front end of the bottom longitudinal is trimmed to shape on the disk sander.

And the bottom longitudinal is in place.

Just like the bottom longitudinal, the front of the top longitudinal needs to be trimmed to fit into the notch in the nose block.  Marking is a simple process of lining up the capstrip and extending the notch angle onto it.

The next step, after trimming the longitudinal, is to secure it in the jig using the cams.  What you can't see here is that my fingers are pushing the capstrip down firmly onto the jig.  All the capstrip has to be completely flat on the jig.  The tail of the top longitudinal is measured for the rough cut with the capstrip completely installed in the jig to make sure the curve of the top longitudinal doesn't result in cutting the capstrip too short.

I mentioned earlier that the tail block needs some final trimming.  In this photo I am making a pencil line along the bottom edge of the block.  The idea behind a lot of these pencil lines is to serve as an indicator.  By sanding off just to the point where the pencil line disappears, I avoid taking off too much material.  If too little is taken off, I simply make another pencil line and repeat the process.

Here is the tail block being trimmed.  Because the front edge of the block is perpendicular to the bottom longitudinal it makes sense to use the miter gauge. 

Perfect fit!  It is important that these parts are friction fit between the longitudinals without pushing the capstrip out of position. 

Here are the two longitudinals installed on the jig ready for the verticals and the braces.

This is a glimpse of the shelf on my work table.  I keep the hand tools and buckets of gussets handy so that I am not wandering around the shop looking for parts and tools.

Marking the first vertical for trimming.  This is a pretty simple process of lining the capstrip up, sighting down onto the top longitudinal, and marking the vertical-to-be aligned with the bottom edge of the top longitudinal. 

The vertical-to-be is trimmed.  Note the penciled arrow.  I mark parts that have only one orientation with an arrow pointing to the top of the part.  This really helps keep things straight.

The bottom of the vertical is marked to length at the bottom longitudinal.

The vertical is cut to length, at least the first cut, is done on the band saw.  I always make this cut on the waste side of the pencil line.  The part always turns out a little long.  Thankfully.

And, predictably, the vertical is just a bit long. 

I make a pencil line right at the end of the vertical, just a lead-width wide.

And it is trimmed. In these instances I just sand down until the pencil almost, but not quite, disappears.

Still just a bit too long.  So another pencil mark is made and back to the sander.

Perfect fit!  The business card is serving as a shim.  Tony Bingelis recommends that when installing the verticals next to the spars (represented by the 3/4" plywood filler) an allowance of .010 to .015 be made so that the ribs can be slid onto the spars.  The business cards measure out to .013. 

The 1/4-inch shim between the cam and the vertical is there because some of the ribs require double verticals at the spars. 

All of the verticals are cut and fitted using the same process.

Now its time for the braces.  I place a length of capstrip in the location for the brace for marking.  This first mark is aligned with the vertical.

And a second mark aligned with the top longitudinal.

I rough cut the braces to length so that they are easy to handle and the bottom angles can be trimmed on the sander.  The sander works much better for these angled cuts than a saw.

The bottom of the brace is rough cut on the band saw.

On the top of the brace, first one angle is cut...

Then the other.  Again, note the arrow to keep straight which end is the top and which the bottom.  When one is cranking out braces, it can get confusing as to which end is which.

Then the bottom end is aligned and marked for final trimming...

Like so...

And, after a couple of trips to the sander, a perfect fit.  Well, almost. If you look closely, I have made a mistake (not an unusual occurrence)  that will result in my having to make another brace.

That's right.  The shim on the vertical next to the spar is on the wrong side of the capstrip!  I have to watch myself all the time.

The rest of the pieces are simply repeats of these steps down the length of the rib.  Once all the pieces are in place, gluing gussets can begin.

First Tool List

Since I am well into fabricating wing ribs, I think it is time to outline the first tool list.  When I get inquiries about homebuilding, what tools will be needed is always in the list of questions somewhere.  As I get near the completion of each stage of construction, I will generate a list of tools I used. 

This list is what I have used in the construction of the wing ribs.  It includes tools needed to build not only the ribs, but also the jigs.  The list isn't in any particular order.  It's just as the tools come to mind.

1.   Table Saw:  This is indispensible tool for ripping plywood to size and mass producing gussets.  I have two, but the one I use the most for this project is my Ryobi.  Pretty much a standard homeowner saw.  It makes very accurate cuts, but a lot of the bits and pieces are plastic and the saw requires a bit of careful handling.  Fortunately, Ryobi has been very helpful in providing replacement parts.  If I were shopping now, I would probably look for something less fancy (the Ryobi has lots of neat features) and more robust.  I would look at Grizzley Industrial.

The second saw I have is an ancient Rockwell.  They also made the Craftsman table saw of the same era (1940-50's).  Though a small saw, it is very hefty cast iron and steel.  It takes two people to lift it.  Because it doesn't have a rip fence I use it when I need to set up cutting jigs to make multiple parts.  I haven't used it for the airplane. 

2.   Band Saw:  You gotta have a good one.  You will use it to cut some pretty heavy stock for jigs, as well as some very small parts. So it needs to be both sturdy and precise.  Mine is an ancient Craftsman that is no longer offered.  One of the lightweight, made in China benchtop models is not going to do the job.  If I were shopping for one today, I would look closely at Grizzley Industrial, especially the new one they just introduced.

3.   Belt/Disk Sander:  You will use this tool a lot.  Most of my ribs were fabricated using a very old Craftsman.  In the 1940's and 1950's Sears offered a line of less expensive tools that were very bare bones, but were extremely sturdy.  For a very a reasonable price you get a hefty tool with no frills.  On most of them, you had to figure out how to mount it, and provide a motor.  I wonder how many of these tools were powered by used washing machine motors.  Mine (the sander, not the motor)  finally wore out.  "Reasonably priced" tools are now mostly Chinese junk.  I replaced my sander with a Porter-Cable unit that so far is working fine.  If you can afford it, get a sander from one of the companies that advertise in the high end woodworking magazines, and made in the USA.  You will pay a lot of money for it.  I will keep everyone informed on how my Porter-Cable holds up.  But I don't expect it to be working 60 years from now.

4.   Router:  This is a handy tool for making jigs and one-off parts.  Mine is a 3/4 HP Ryobi.  You don't need one that hefty, but it pays to get a good one.  I know some folks use laminate trimmers.

5.   Drill:   You can certainly drill holes using a hand drill, but a battery powered electric drill speeds things up a lot.  I have a had several of these and either the batteries reach the end of their cycle life, or the charger smokes.  It seems it is cheaper to replace the whole drill than buy new batteries and/or charger.  My current one is a Ryobi, but its batteries are about dead. The last expensive one I had (DeWalt) didn't last any longer than the cheap ones.  You will also need a collection of drill bits.  A small set will do.  In assembling plywood jigs you may need to fasten into the end grain.  You don't want to use sheetrock screws for that.  When you buy standard wood screws, get the counter sink bit to match.

6.   File:  I use just one.  It is a double cut bastard file.  I find it more useful for cleaning up fuzzies and doing minor trimming than sand paper.  Be sure and get a handle for it.

7.   Steel rulers:  I have two.  One is a foot-rule, the other is 36".  Get good, solid steel rulers.  They are expensive, but worth every penny of it.  DON'T USE THEM FOR STRAIGHT EDGES.  Use them only for measuring.  The EAA site has a good article on accurate measuring. 

8.    Mechanical Pencil:  I keep two or  three floating around the shop.  Building this airplane is not like rough framing a house.  The carpenter's pencils are not fine enough. I use Pentel P207, the blue ones.

9.   Staple Gun:  I have a small collection of these.  I don't know where they all came from.  I just seem to have collected them over the years.  All are sturdy Bostich guns.

10.  Scissors:  I use a sturdy pair of scissors to cut up old business cards (glue spreaders, shims, etc.) and to make final trims on gussets.  They also open up packaging, clip the ends on glue bottles, and cut the full size rib patterns from the plans.

11.  Side Cutters:  I use mine to pull staples.

12.  Some kind of small saw:  There are occasions when you need to trim capstrip and both ends are longer than the throat of your band saw.  You can use a razor saw, marketed by X-Acto.  Get the finest teeth available.  I have a small, cheap, made in China table saw (the table is about 4" square) from Harbor Freight.  It works great, though the power switch is starting to fail.

13.  Clamps:  I am a clamp junky.  You simply cannot have enough clamps.  I have a substantial collection I have personally collected, and I "inherited" a bunch from my dad and from a friend's dad.  If I encounter a garage sale, I always drop in and poke around.  If they have clamps, I buy all they have.  Big ones, little ones, C-clamps, spring clamps, pipe clamps, it doesn't matter.  You can't have enough.  I also have a bag full of spring type clothes pins.  Try and find the old wood ones.  The plastic ones aren't much use.  Poke around in your grandmother's laundry room.

14.  Six-way Screw Driver:  I love these things.  They are the ones with the interchangeable shafts and bits. They used to be expensive.  Now you can find pretty decent ones in displays next to the checkout counter at the hardware store for just a few bucks.  I have quite a number of these squirreled away in handy places.

15:  Chisel:  A 1/2" is a good size.  Keep it sharp.  You don't think you might, on occasion, glue a rib to the jig?  Riiight!

16:  Sanding Block:  I keep a sanding block around with fairly course sand paper in it.  It is useful if a bit of capstrip is slightly out of spec and you need to sand it down a bit.

17.  Measuring Tape:  For rough measurements.  Like doing the initial ripping of a large piece of plywood.

18.  Razor Blades:  You want to scrape accumulated oxidation and grime off of surfaces to be glued.  I buy these by the 100-count box at Harbor Freight.  Let me clarify.  I bought a 100-count box from Harbor Freight several years ago.  Maybe I have used 10 over the years... You sure wouldn't want to shave with them, but they work great for what we need.

19.  Carpenter's Square:  To make sure things that are supposed to be square are.  I also use the straight edge as a straight edge. 

20.  Hammer:  Just a plain carpenter's hammer will do.  Mine is a high quality one I have had since Adam was a pup.

21.  Whatever supplies are appropriate for whatever adhesive you are using.  I have a bunch of graduated mixing cups and tongue depressors ordered from SystemThree along with the T-88.  The quart size (1 pint resin, 1 pint hardener) is plenty to do the ribs on Wag-a-Bond Traveler.

I also have a radial arm saw, which I have used for some things in airplane construction.  But you don't need one.  The table saw will do what needs to be done almost as conveniently.   

I think that covers it.  I will add items if I think of something else.

Important production tip

Always let the adhesive set up sufficiently before removing the rib from jig.   :(

Keepin' on keepin' on

Another day, more ribs.  So far today I have spent 2-1/2 hours building ribs.  One is complete, one has all of its gussets glued and is setting up, and a third is in the jig with one side glued up waiting to set up. 

Sander & Jigs

After spending most of last evening and much of this morning researching belt/disk sanders, I came away more than somewhat discouraged.  In my price range whatever I was going to get would be made in China.  Even some of the higher end units are Chinese. 

After reading lots of reviews, I narrowed my choices down to a Skil belt/disk, a Port Cable belt/disk, a Master Mechanic belt/disk, or a Harbor Freight disk only sander.  But I wanted to look at whatever I was going to purchase. 

The Harbor Freight unit was on the list in desperation, as I could not find a local source for any of the others.  I like having the belt, but the disk is essential.

I had business in Belfair, so decided to head for Tacoma and the local Harbor Freight after finishing up with the business.  On the way, I decided to stop in at the Lowes in Port Orchard and see what they might have.

Weellll, they had both the Skil I had seen on line, and the Porter Cable.  Upon examining the Skil, I decided it was not satisfactory.  But the Porter Cable unit looked good.  The work tables were sturdy (a common failing for all the other Chinese tools), and most of the cover plates were stamped steel instead of plastic.  It also had a 3/4 HP motor as opposed to the 1/2 or 1/3 HP on most of the sanders in my price range.

So here it is, ensconced in my shop:

I have built a rib with it, and it works just fine.  I had to get used to doing things kind of turned around.  The disk and belt run opposite direction from the old Craftsman.  It also turns a lot faster.

It also has a dust collector that actually works. 

I have been a bit tricky on the power.  It seems the Chinese have not mastered the skill of manufacturing basic on/off switches.  Almost every unit had at least one review featuring power switch failure.  My old sander was powered by a 3/4HP motor mounted under the table with a powered outlet connected to hefty switch.  I plugged the Porter Cable into that outlet and turn it off and on there, just leaving its installed switch on. 

Speaking of being tricky...

What do we have here?  Well, that gusset with all the staples in it is a replacement for the first try.  As I pulled this rib off the jig, I discovered that this long gusset had cupped during the gluing process with little of it in contact with the capstrip or the plywood block.

I had designs on cutting and fitting the capstrip for another rib, so I didn't want to tie up the jig while fixing this one problem.

So, I nailed a piece of 1/4 plywood, the piece at 90 degrees from the rib, in place cramming the capstrip up against an alignment block on the jig, thus holding the capstrip on the offending rib firmly in place.  I then buttered up a new gusset and stapled it in place. 

Jigs don't need to be fancy, they just need to get the job done.

Stack-o-Ribs

Here is a stack of finished ribs ready to be moved up to the hangar.   Things are coming along.

I was corresponding with an internet friend a couple of days ago who is a lot further along on his airplane than I am on mine.  He let me know that he had built all of his ribs in 10 days.  At my pace, I will be lucky to finish all my ribs in 10 months.

Of course, he had some advantages. He is retired and he lives in Arizona.  The advantage of being retired is obvious.  Arizona?  The curing time of the adhesives is highly temperature dependent.  He could glue up a rib and set the jig in the desert sun.  The rib would be safe to pop out of the jig in no time.

Here are a couple more setting up on the jig.

My venerable old sander quit this evening.

I have been nursing the old girl along, but the bearings finally packed it in this evening.  I took the belt off in hopes of getting a few more hours, but it just wasn't going to happen.  They don't make them like this anymore. 

And More Ribs

I spent the afternoon working on a couple of ribs.

What you see (if you look hard) in the above is one rib in the jig with all of the capstrip cut and fitted, and one rib out of the jig.  The rib out of the jib has its gussets on the down side all glued in place.  You will also note that all of the gussets for both ribs are laid out ready to glue in place.

My routine is to take a rib whose gussets on one side have been glued and place, and set up long enough to handle, out of the jig and flip it over ready to glue the second side gussets.  Then I cut and fit the capstrip for another rib in the jig.  When that is complete, I install the gussets for both ribs.

Just the opposite view of the same thing. I always wear latex gloves when working with the epoxy.  Fortunately, T-88 does not have a strong odor.

This photo shows my mixing setup.  The little medicinal cups came from SystemThree, who are the manufacturers of the T-88 epoxy.  So did the mixing sticks.  I found the mixing sticks a bit of a problem.  The are quite wide (obviously tongue depressors) and have rounded ends.  The rounded ends make it difficult to get into the corners of the mixing cups.  So I cut the mixing sticks in half and sand one end square.  You can see a cut stick lying across the full stick that has had that treatment.

I mix 5 ml each of resin and hardner in the cup.  The graduations on the cup make it very easy to accurately measure the 1:1 ratio specified for the T-88.  It takes two batches to do two ribs. 

This last photo, taken as the sun was heading down, shows the completed ribs.  The rib on the right, not in the jig, is totally complete.  The rib in the jig, on the left, will be removed from the jig when the glue is sufficiently set up to handle, and flipped over for application of the gussets on the "bottom" side.

Off & Running Again

My EAA Technical Adviser came over to my shop to take a look at what I am doing and to discuss adhesives. 

We tested some Titebond III joints and determined that the Titebond III will give a satisfactory joint.  However, I am still switching to the T-88 epoxy.  There are some definite production advantages.  The T-88 manufacturer (SystemsThree located here in Puget Sound country) specifies that the product cure with zero clamping pressure.  That means no more staples.  While it doesn't take long to install the staples, pulling them is a time-consuming pain.

The conclusion that the Titebond joints are satisfactory eases my mind on the ribs I have built so far.  There is no need for me to start over.

The adviser is very please with the quality of my work so far.  I was even able to give him a tip.  He has used an Exacto razor saw to miter his capstrip.  I have found that cutting it roughly to length and then doing the final shaping on the disk sander to be both faster and more precise.