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Don Smith A-26 Build

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Don Smith A-26 Build

Old 11-06-2015, 09:17 PM
  #151  
Eldher
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With the initial joining of the wing done, I want to see how the fit to the fuse is setting up, before making more investment in the wing.
Here I'm separating the section of fuse that goes above the wing.

Now setting the wing on the fuse. Initial fit is not bad, more to do the get it just right.

The top section of fuse needed considerable sanding of the formers to get it to sit even close to where it needs to go.


Now back to finishing up the center section of the wing.
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Old 11-14-2015, 04:57 PM
  #152  
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Construction of the center section is progressing. The right inner flap is complete and the full TE of this section is sheeted. Here's some picts.
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Old 11-22-2015, 04:19 PM
  #153  
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Servos mounted for the inner flaps. They work well. Experimenting with different hinge attachments. Also my wheels and breaks arrived from Century Jet.
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Old 11-29-2015, 07:34 AM
  #154  
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Moving on to attach the wing to the fuse. Now the fun here is that the plans offer absolutely NO guidance on how to do it. The wing is simply sitting on the fuse. As covered earlier in the wing construction I put hardwood blocks in the wing to accept bolts. Now I will put blocks in the fuse with blind nuts. This is the same approach as the wing attachment on my B-25.

The block in the fuse will be beefy 2.5" wide, 3/4" think. The dihedral is 8 degrees so a flat block is not going to work well. Here I've made a block at the correct angle to fit the bottom of the wing. 3 dowels splice the center joint and the bottom is reinforced with carbon fiber.


The blocks in the wing are attached to the rear side of the main spar. In the fuse that lines up with one of the fuse formers. So it will be removed to make space of a wide attachment block. The block is just sitting in the fuse at this point (second photo).
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Old 12-06-2015, 12:13 PM
  #155  
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Mounting blocks put in place. Note they are pinned with 1/4" dowels to the ply "spine" (the load bearing members in the fuse). This way there is a mechanical linkage at the joint, not just relying on the glue to hold it.


The rear block has been set up in a similar manner, Here's the wing bolted down for the first time.
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Old 12-20-2015, 07:33 PM
  #156  
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Now that the wing is mated, I've moved to securing the section of fuse over the wing back to the rest of the fuse. Here I'll use 2 bolts, 1 at the front, 1 at the rear, and some guide pins. For the bolts,I first added ply tabs to the existing fuse and cut notches in the removable section over the wing. Drilled holes in the section and the tabs. Glued in T-nuts to the ply tabs and ran bolts through it. Here's the inside of the fuse, which is *upside down* (looking from the rear gunner area). You can see the bolt, T-nut, and ply tab.

Now the sides of this removable section flex a lot at the rear, just because the section is much taller at the rear than the front. to stabilize this, I've put in 2 pins using 1/4" aluminum tubing and ply. Here's what it looks like:
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Old 12-20-2015, 07:42 PM
  #157  
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Securing the main cockpit canopy was a bit of work. I want to be able to remove this canopy if needed. There will be a pilot and other cockpit details up here and you never know what will come loose! To get a good fit between the canopy and fuse, I needed to add a layer of 3/16" balsa to the top of the fuse inside the canopy area (just behind the windscreen). And then cut a groove for the canopy.


The original A-26 cockpit framing was held in place with flush mounted screws. Like about 61 of them (best guess based on the pictures I have). I can't get a good flush mount, but pan-head screws have a very low profile. Here I've used 61 #0 pan-head screws backed by ply inside the fuse to mount the canopy.
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Old 12-26-2015, 10:58 AM
  #158  
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The fairing around the wing is big. It's easily seen here.


To make this feature I'll start by creating the shape against the fuse and this will become the base for the rest. This needs to fit close to the wing, but not glued to it. It will be glued to the fuse. But the section over the wing is removable. So, this will need to come together in 4 sections. 2 above the wing and 2 below. Here's what 1 of the 4 looks like.


And the completed fitting, below and above.

Still have to do the area sitting on the wing.
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Old 12-26-2015, 01:12 PM
  #159  
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Will you be adding any cockpit detail? Lookin' great! Keep up the good work.
Old 12-26-2015, 01:36 PM
  #160  
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Originally Posted by vertical grimmace View Post
Will you be adding any cockpit detail? Lookin' great! Keep up the good work.
Yup, I'll add some. Still thinking how much (full or partial). However, I will only do a basic framing and painting of the cockpit before the first flight. With the canopy removable I can come back and detail it out later.
Old 12-28-2015, 11:57 AM
  #161  
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Starting on the nacelles. The plan suggests building these like the fuse. Build half on the plan, flip it over and build the other half. Plank 3/4 of it and then mount to the wing. Having these 2 big long nacelles built and trying to align them to each other and the incidence of the wing seems problematic. Or at least not easy. I will be building the engine boxes first, then aligning/attaching them to the wing. Then build the rest of the nacelle around the box. Of course if you happen to be building one of these beasts while reading this, the first thing you'll say is, "There is no engine box in the nacelle." All too true. The nacelle design is identical to the fuse. Half circle formers with a ply "spine" down the middle of the half section. The completed assembly has 2 spines and 2 half shells. However, making a box is easy as there's nothing between the spines. Just add some ply. There is also (included in the original design) a 1/4" think ply ring around the spines. These also help make the initial box easy. Here's the first engine box assembled. I'll make another one and then mount to the fuse. And, yes, there is a left and right, so you have to pay attention to make one for each side properly.

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Old 12-28-2015, 12:04 PM
  #162  
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Here's a bottom view of the box. Note that it's open, but there are 2 3/8" wide strips glued to the edges of the sides of the box. The strips make the sides of the box much stiffer. This will remain open to provide access to the tank and engine mounting bolts. A hatch will be added to the outer nacelle. I had hoped to be able to access the tank from the wheel well as on my B-25. However the retract unit blocks half the opening and the wing's main spar blocks the other. Uggg.
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Old 12-30-2015, 09:51 PM
  #163  
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https://youtu.be/jNyB8k8NTQ0

Eye candy!
Old 12-31-2015, 09:48 AM
  #164  
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You might want to double check your source on the wing fairing. That looks to be the ancient 1/72 Airfix Invader. Try these:

http://www.richard-seaman.com/Wallpa...6Midland07.jpg

http://s358.photobucket.com/user/197...der-1.jpg.html
Old 12-31-2015, 10:03 AM
  #165  
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I have learned that plastic models can be notoriously out of scale. If scale is actually the objective. Verifying scale sources against each other. Actual photos trump all, at least in the scale competitions in the U.S.
Old 01-01-2016, 03:02 PM
  #166  
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Thanks guys for the references! I'll look at them and make sure the fairing comes out right.

And I love the video of Sugarland Express. If it only had a turret on the top, I'd model it!
Old 01-01-2016, 03:10 PM
  #167  
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OK, I've been working for a couple of days to mount the engine boxes/nacelles to the wing. First check that they fit down into the wing. the sides of the boxes grab the main spar front and back. Also lock into the rear spar.

Both nacelles just sitting on the wing and first check to make sure we're in the right neighborhood for alignment (i.e. they better be close to start with).
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Old 01-01-2016, 03:21 PM
  #168  
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The nacelles need to align 6 ways to Sunday
The wing is mounted to the fuse with 1.5 degrees positive incidence. We want the nacelles at 0 degrees (i.e. aligned with the thrust line/center line). they also need to align with each other or be parallel to each other. And they need to hang straight down from the wing (not in the same plane as the wing bottom), this so the gear sticks straight out the bottom. The firewalls need to be in the same plane (alignment), i.e. we don't want one engine ahead of the other.They should be at a right angle to the main spar. The should be equidistant from the center of the wing.

This will be easier if I can jig things to be able to measure everything on the nacelle as 0 degrees or a level bubble. So I set up a jig on my table and got it level in both directions. Then I placed the wing on it upside down at negative 1.5 degrees. Now do all the alignments getting everything to a zero bubble. Here's what it looked like in process. The incidence meter stayed on the wing center the entire time to ensure I was always at negative 1.5 degrees.
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Old 01-01-2016, 03:25 PM
  #169  
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Once it was all aligned, I glued it up. Took several hours to get the alignment just right. Here it is all glued. Used hardwood triangle stock and fiberglass to ensure all the joints are really solid.
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Old 01-03-2016, 10:40 AM
  #170  
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Assembling the nacelle is straight forward, but quite tedious. Key here is to ensure that all the formers align and that the landing gear rails are aligned. I used triangle stock at each former to create a slot that the former would sit it, but did NOT glue the former (initially). This allowed the nacelle to be assembled and disassembled numerous times while all the parts were trimmed, fitted, and aligned. Once set, all was glued up.
This is the first 2/3 of the nacelle there's another 12" of nacelle still to be built.
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Old 01-05-2016, 02:33 PM
  #171  
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To wrap up my Christmas vacation build, I completed the core of the second nacelle and installed the main gear.
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Old 01-09-2016, 07:56 PM
  #172  
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Today I built the right aileron, which completes the pair. Sanded and hinged.
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Old 01-09-2016, 07:58 PM
  #173  
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Sanded the LE of each wing panel. With the gear mounted, I really wanted to see what she's looking like assembled. This is the first time she's been put together and stood up. Mean machine
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Old 01-10-2016, 08:53 AM
  #174  
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Bet you are smiling now!
Old 01-10-2016, 09:08 AM
  #175  
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That really looks great! Awesome job.

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