Sunday, January 19, 2014
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.
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.
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.
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........
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
Nails and pre-nailing gussets
Gussets need pressure after the epoxy is brushed on the part and set on the rib when it's on the jig. This pressure can come from 3 primary methods.
1.) Weights
2.) Nails
3.) Staples
I decided to use nails. The nails came from Aircraft Spruce and they are 20 ga coated aircraft nails 1/4" long. I ordered a pound and that's a few thousand nails.
After giving this some thought and asking some questions on the Biplane Forum I decided to pre-nail the gussets. I did this because the nails act act as a handle when brushing the glue. The basic idea here is to find a small scrap block of wood and nail in the nails just enough so they poke through a tiny bit, this keep them from sliding.
It was kind of a learning curve and at first I actually marked out a 1/4" line on the gussets so I could hit the center with the nails. But after a few of those I decided to forget the pencil line and just use my good eye. It worked just fine and took a lot less time.
So I pre-nailed all the gusset pieces for the facing side and the back once it's pulled out of the jig. The nails are small but once I found my groove I moved pretty fast. I put a small hammer on my right side and a small needle nose pliers on the left. The nails I put in the middle. I developed a habit of grabbing a nail with my right hand and holding the pliers in my left hand. The gusset sit on the block and I hammer them in....lightly!
Once the entire rib assembly had enough gussets pre-nailed to produce a rib I moved to the next step.
1.) Weights
2.) Nails
3.) Staples
I decided to use nails. The nails came from Aircraft Spruce and they are 20 ga coated aircraft nails 1/4" long. I ordered a pound and that's a few thousand nails.
After giving this some thought and asking some questions on the Biplane Forum I decided to pre-nail the gussets. I did this because the nails act act as a handle when brushing the glue. The basic idea here is to find a small scrap block of wood and nail in the nails just enough so they poke through a tiny bit, this keep them from sliding.
It was kind of a learning curve and at first I actually marked out a 1/4" line on the gussets so I could hit the center with the nails. But after a few of those I decided to forget the pencil line and just use my good eye. It worked just fine and took a lot less time.
So I pre-nailed all the gusset pieces for the facing side and the back once it's pulled out of the jig. The nails are small but once I found my groove I moved pretty fast. I put a small hammer on my right side and a small needle nose pliers on the left. The nails I put in the middle. I developed a habit of grabbing a nail with my right hand and holding the pliers in my left hand. The gusset sit on the block and I hammer them in....lightly!
Once the entire rib assembly had enough gussets pre-nailed to produce a rib I moved to the next step.
Epoxy break test before building wing ribs
I decided to use T-88 Epoxy for building the wing ribs. But before I started using it I ran some test samples. The mix ratio I used was done visually, so I cut some scrap cardboard and made two circles in equal size of both parts. Then I mixed it and glued it. After a couple days I pulled a gusset off and studied where it broke.
In the photos you can see the wood broke and the epoxy didn't. This is exactly what you want a test sample to look like and it's time to move forward with building.....
In the photos you can see the wood broke and the epoxy didn't. This is exactly what you want a test sample to look like and it's time to move forward with building.....
Using the patience stick & sanding gussets
So here is how I used the Patience Stick.
After clamping in a pair of rough cut gussets, made with the scissors, I started up the disk sander and just gently rolled the tool left to right (clockwise) until the inked line disappeared. It's just that simple. The entire process takes about 4 seconds. This tool makes these gussets at lightning speed.
Sanding -
Once the gussets are sanded on the disk sander I wanted to break the outside edges of the gusset and smooth them off. Is that required? No, I guess not, but if i'm gonna spend thousands of hours building an airplane I want to build it to the best of my ability.
With the fine grit sanding sponge I simply rolled each piece across the sponge. It worked great and the edges are extremely smooth.
Below are the photos showing what I did. Click and zoom in on the photos to see better detail.
After clamping in a pair of rough cut gussets, made with the scissors, I started up the disk sander and just gently rolled the tool left to right (clockwise) until the inked line disappeared. It's just that simple. The entire process takes about 4 seconds. This tool makes these gussets at lightning speed.
Sanding -
Once the gussets are sanded on the disk sander I wanted to break the outside edges of the gusset and smooth them off. Is that required? No, I guess not, but if i'm gonna spend thousands of hours building an airplane I want to build it to the best of my ability.
With the fine grit sanding sponge I simply rolled each piece across the sponge. It worked great and the edges are extremely smooth.
Below are the photos showing what I did. Click and zoom in on the photos to see better detail.
The "Patience Stick" - A tool to grind gussets and learn patience
The Patience Stick -
I needed a tool to expedite the sanding and finish process. There's a ton of the round gussets and because they are round it makes finishing these extremely time consuming. Because I have a 12" disk sander I wanted to use that, it's a great tool and it's a productive tool when used properly.
The Patience Stick is a tool that holds 2 half round gussets at one time. It's a stick that has a notch cut in the end to capture both parts and a clamp that holds them tight to the backstop so they don't move.
On the notched portion I glued down some sandpaper to keep them from wanting to slide off. It works perfect, in fact, it worked better than I had imagined.
I needed a tool to expedite the sanding and finish process. There's a ton of the round gussets and because they are round it makes finishing these extremely time consuming. Because I have a 12" disk sander I wanted to use that, it's a great tool and it's a productive tool when used properly.
The Patience Stick is a tool that holds 2 half round gussets at one time. It's a stick that has a notch cut in the end to capture both parts and a clamp that holds them tight to the backstop so they don't move.
On the notched portion I glued down some sandpaper to keep them from wanting to slide off. It works perfect, in fact, it worked better than I had imagined.
Marking and cutting gusset patterns
I took a 2' x 4' piece of 1/16" Mahogany and ran it through a table saw so I had manageable strips of wood to mark the patterns on.
Once I had those cut I simply marked them out using a fine gel pen that doesn't bleed ink and keeps a fine line.
The I took a sharp scissors and cut them reasonably close to the inked line. I did this for all the pieces that make up the wing rib.
Once I had those cut I simply marked them out using a fine gel pen that doesn't bleed ink and keeps a fine line.
The I took a sharp scissors and cut them reasonably close to the inked line. I did this for all the pieces that make up the wing rib.
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