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.  

Major Setback

While doing a bit of net surfing today, I ran across some structural tests on the adhesive that I am using, Titebond III.

On balance, all the test results were not conclusive either way.  But "not conclusive either way" is not good enough for an airplane. 

So, I will be changing adhesives.  It appears that there is little choice but to move to T-88, an epoxy adhesive with all the strengths, and difficulties, of epoxy.  It also means that I will scrapping the ribs I have built so far. 

Bummer.

Gluing, Gluing, Gluing

I spent 3.5 hours in the shop today.  I confirmed an important safety lesson.  There is a theory that attempting to hold a very small part, with your finger tips, against the belt sander fence is almost guaranteed to result in considerable pain and bloodshed.  But part of my brain was not satisfied with theory and was determined, in the absence of empirical evidence,  to go ahead with the attempt. I am pleased (well, "pleased" is not exactly the best word) to report that the theory works out perfectly in practical application.

I have here a photo of a gusset glued up and ready to install.

This view also shows the bit of business card I use to spread the glue and the razor blade whose function is to scrape the parts prior to gluing.  The objective of the scraping is to remove oxidation, grime and what-have-you that accumulates on the wood surface and can weaken the glued joint.

The reason the entire back side of the gusset is spread with glue has to do with the need to seal the wood parts against moisture.  Once all of the wood parts are fabricated and generally assembled, they will be treated with a high quality spar varnish.  However, getting to the backside of the gussets with the varnish will be essentially impossible.  So, a layer of glue is applied to the entire back side, thereby sealing that side of the gusset.

The next photo shows the gusset stapled in place.

The number of staples used for any particular joint depends on how well the gusset snuggles down onto the cap strip.  I try to use the minimum number of staples possible in order to make the job of pulling them out easier.  Yes, the staples are removed once the glue has dried.

There has been considerable discussion within the Wag Builders Yahoo Group, resulting from confusion on my part, regarding the number and location of reinforcing blocks to be installed on the #1 rib for the purpose of attaching the wing root fairings. 

After much poking around, photographing Piper rag airplanes, and just plain scratching my tummy, I came up with an approach.  The following photo shows the 1"X1" blocks that I have installed.

Though the plans call for only 5 of these blocks, it is not made clear whether that is 5 per rib, or 5 total.  In any event, 5 does not appear to be enough.  There are actually 14 per rib on my airplane.  Is that the right answer?  I don't know.  One of the challenges of building from plans is that there will be problems that require solutions before one has a complete grasp of the problem.  This is one of those situations.  We will find out if it is the right answer when it comes time install the wing root fairings.

Routine

Well, hopefully, it is back to routine life.  I hope to work a bit on the Traveler today.  But the Alvord trip seems to keep on giving.  All who attended are still excited about the event.  It was definitely a high point adventure for me.  One last shot...here is a photo taken of my arrival.

After a final leg of flight, from Burns, Oregon to the Alvord Desert, the landing was picture perfect.  I was definitely paying attention to the landing on the dry lake bed. It is a bit tricky.  But I pulled it off as if I had been doing it all my life.

Back to the shop!

Alvord

I promised photos of the Alvord Desert fly-in.  It was a great adventure, made more so by learning that my airplane has a performance problem not obvious in low-altitude flying. 

These are not in any kind of order.

Baby Steps

I promised to make some effort to keep something on the blog through the process of fabricating wing ribs.  It is, as I said, a highly repetitive process.

Plus, there have been quite a few demands on my time and I haven't spent the time in the shop that I have wanted.  Still, on Sunday afternoon I was able to sneak into the shop and get a rib built.

One other adventure that has been slowing work is preparation for the annual Alvord Desert flyin by a bunch of 150 guys here on the west coast.  The flyin is completely casual with no organization except the selection of a date.  The weekend of 9/15 this year.  This will be the first year I have been able to attend, and I am very much looking forward to it.

The Alvord Desert is located in southeastern Oregon.  There is nothing there.  The flyin is to the dry lake bed that comprises most of the desert (yes, there is desert in Oregon).  The weekend is a camping event, but it is completely primitive.  There are no facilities beyond some ramshackle buildings around a hot springs and a pipe installed in one cold spring. 

I will post photos on this blog and the 46Juliet blog.