Building the butt ribs for the upper wing - 5

Once everything was cured I pre nailed the entire butt rib profile so I wouldn't have to deal with this while spreading the epoxy.

I did not let the nails poke through anywhere on the rib plate.......yet!

Once the nails were all started I very carefully positioned the nose tip / cap strip pre-glued assembly on 1/8" bobbed butt plate making sure it was aligned perfectly. I then set it on the table and tapped on 4 nails on the back side of where the nose block goes. This helps in assembly once the epoxy is on. The nails self alight with the divots.

Click to enlarge

Building the butt ribs for the upper wing - 4

Once I was sure the bobbed reinforcing block was sized correctly I glued it and nailed it.

Click to enlarge

Building the butt ribs for the upper wing - 3

The trailing edge, which is the bobbed profile, has a reinforcing block glued and nailed to it. The block is 1/4" plywood.

Instead of trying to make the actual part I made a pattern from 1/8" plywood to see how well it would fit. It was an unnecessary step but it did work well. Once the pattern was made I just traced it to some 1/4" plywood and made 2 of them, one for each wing (right & left).

NOTE: I made the upper and lower surface of the 1/4" reinforcing plate a little fat so when it's glued it sticks past the actual butt rib pattern that was made earlier. I did this so once the entire butt rib was made I could could sand it to match the butt rib on the 12" sander making a perfect surface edge profile.

Click to enlarge

Building the butt ribs for the upper wing - 2

With the bobbed profile complete the next step is similar to the way I did the other ribs. Remember how I pre-glued the capstrips to the other nose rib blocks? Well, this method of using the jig is similar except the cap strips get notched to mate up with the nose rib. The photos do a better job of explaining it than typing.

What's really important here is to make sure the cap strips are glued flat, or parallel, with the nose block.

Click to enlarge

Building the butt ribs for the upper wing - 1

With the 14 normal ribs for the upper wing complete the next task is to build the butt ribs. The butt ribs for the upper wing are made from pieces of 1/8" mahogany plywood reinforced with a 1/4" nose and tail block. For the cap strips the plans call for 1/4" x 3/4".

I made the special cap strips by cutting them out of an old piece of spar material.

The profile of the 1/8" plywood butt rib was made by holding a normal with rib on top and tracing it with a fine pen. To make it accurate I decided to leave the gussets off the normal wing rib so the surface would lay flat and make tracing easier.

Once traced, I profiled it on my 12" disk sander and fine tuned it with a mill bastard file.

The profile of the butt rib is unique because the trailing edge has a bobbed profile. This helps make the half circle cut out in the middle of the wing that sits centered with the cockpit. I pulled measurements for the bobbed profile to give me a length but I drew the curves free hand with a pencil and gently ground it using the disk sander.

Below are the photos, click on the photos to enlarge.

Building ribs - Rinse, Wash & Repeat

Just keep on trucking, almost done and then off to build the wing root ribs!

Up close photos of gussets and ribs after epoxy dries

Photos of wing ribs completed. The goal is to produce the 14 upper wing ribs first and then move on to the two wing root ribs. I want to build and assemble the upper wings complete before doing the the lower wings.

Final nailing and assembly of ribs (back side) - Part 2

Once the top side is done I pull the wedges out and gently pry/lift the wing rib from the jig. The back side is similar except you are starting out with no gussets sitting on the rib itself. Instead, and you can see in the photo, I just have a pile of remaining gussets to pick from.

I started out putting the rib on a piece of cardboard until I could pick up the mess and re-boot my thoughts for a minute. Then I set it on a piece of craft tag board and finished it up.

Final nailing and assembly of wing ribs (jig side) - Part 1

Nail it home and let the kids have fun!

Right side is nailed, left side is still dry and waiting for epoxy. One gusset at a time until the top side of the wing rib is 100% nailed and ready to get pulled out of the jig.

Spreading epoxy on gussets and rib cap strips

The Baby Great Lakes is a small biplane and because it's small so are the wings. The wing cord is 36" and the jig itself is only about 38" long so I elected to build the ribs on the kitchen table.

This process is so simple that I won't write much about the process. What I will do instead is right down a few notes on what to look for in the photos.

• Acid brush to spread epoxy. I bought a bag of a hundred at Harbor Freight. I cut the bristols short with a scissors over a trash can so it became stiff enough to spread epoxy.
• Epoxy both sides, the gusset and the cap strip.
• See the pencil marks? 
• See the nail divots in the cap strip? That makes the mating process so simple you don't have to think.
• See how the nails poke through?

Pre-assembling rib gussets on the rib jig (no glue yet)

Alright, there's a lot going on in these photos. As you can see in the photos all the gussets are positioned into place. This allows me to double check everything before the epoxy is mixed, in fact, often times I get it to this point and put it up on a shelf until I have time to mix epoxy and assemble the rib.

But the pieces are not just sitting on top. It's hard to tell in these photos but once the gusset is eyeballed in to position I gently tap the nails so they make a divot in the capstrip.....then I just let it be. I work on all the gussets until they are all semi-tacked in to place.

That divot is important. When the epoxy is brushed on the gussets now have a home to fall into position without even thinking. The last thing you want to do is hold a small part with glue on it and try and figure out where it should go.This worked out really well and made assembly a breeze.

So when the epoxy is mixed all the gussets on one side are already on and it becomes a matter of gluing one at a time and nailing it home. And because the gussets are gently poked in to the cap strip when you nail they don't vibrate off.

Lastly, and this is the last step before mixing epoxy, take a pencil and make marks around the gussets on the cap strip so when it is taken off you know where to put the epoxy.

Photos - 

In the following photos you can see a lot of what I discussed in previous posts up to this point. Here is a list of things to look for........

• Wedges
• Shims
• Nail pins holding the cap strip pieces
• Tooth pick used to spread the trailing edge tight to the jig
• Pencil marks on the jig edges used to locate the gussets
• The bevel I put on the jig where the gusset goes to keep epoxy from touching the jig

Click on the photos for close up views