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Oct 25, 2014, 04:18 PM
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Build Log

AMR Trainer 26 - (my) official build thread


I've been in the hobby a few years now and it's time to build my first kit. I chose an AMR Trainer 26 because a used one was for sale at the time I was ready and it looked suitable for a beginning builder. The kit was already partially built (most of the fuselage) which would not be my first choice. But the price was right and to my inexperienced eye it looked good.

The AMR 26 has an 84.5" wingspan and a 66" fuselage. Is is supposed to come in at 12-14 lbs and specified power is a 26-32 cc gasser. I have a DLE 30 to put in it.

I have created a page for this plane on my website (http://www.grosbeakrc.ca/aircraft/amr26/amr26.html) and will update it as I go.

Overview

The AMR Trainer 26 consists mostly of laser cut 1/8" ply with tabs, slots and notches to aid in construction. The wing is built in a supplied jig and the empennage is cut from 3/8" balsa sheet. From a technical writing perspective the manual could use improvement, but with the help of AMR staff, forum members and my own stubborn determination I don't foresee any problems.

My adhesive of choice is Lee Valley Cabinetmaker's Glue 2002 GF; I will be using that unless otherwise specified. The wing will be built on my main workbench atop a section of Sonopan acoustic panel.

Documentation

Manual
My kit is an older edition; the hardcopy of the manual is dated 2008-11-30. The closest available electronic copy is a .pdf file dated 2010-01-10. The significant difference between the two versions is the empennage construction: 3/8" balsa sheet in both cases but laser cut in the latter version and manually cut in the former.

I will be using the electronic copy (2010-01-10) for the build because I will be making references to page, step and part numbers and I want the document to be accessible. Though the empennage construction has changed again since, the rest of my build is still relevant to today's version.

AMR Trainer 26 manual

In addition to the manual I have created a few documents to help me along. The documents are hosted on Google Docs and are shared for viewing; all are subject to change throughout the build.

Questions and Issues
In reading the manual I have run into several snags in my understanding. Many were resolved during the build process or by reading ahead; in some cases I asked AMR for help directly. I have attempted to document all of my questions, answers, issues, resolutions, deviations from the build procedure and explanations therefore.

AMR Trainer 26 - Questions and issues

This document will change often as I progress through the build.

Parts index
There are a large number of laser cut parts in six sheets of 1/8" plywood. Most (not all) are identified on diagrams in the manual on pages 6, 7 and 8. Each page shows a two sheets of parts, one (A) above the other (B). Therefore, my own sheet IDs are 6A, 6B, 7A, 7B, 8A and 8B. Below is a link to a spreadsheet that lists the part number, sheet ID and the steps in which the part is explicitly mentioned.

AMR Trainer 26 - Laser cut parts list

I hope to update the sheet diagrams to reflect the parts that are unidentified. If and when I do I will post links here and wherever relevant throughout the build pages.

Lamination
Most of the parts are 1/8" ply but in many cases they need to be thicker for strength. Such cases require lamination - the bonding of two or more identical parts to improve strength. Most of the build reviews I've read mention that there's a lot of it to be done, and it's scattered throughout the manual. Below is a link a spreadsheet that lists the steps and the parts involved.

AMR Trainer 26 - Lamination steps

It's my plan to do one or two laminations at the end of each build session so that the parts are properly cured and ready when I need them.


First look



You may notice the hangar rash - one of the cheeks was accidentally broken off by the previous owner. No worries - I'll be fabricating a cowl.


Almost all of the parts are laser cut from 1/8" ply; there's a lot of lamination throughout the process so I'm going to identify and tend to that early on. There are a lot of tabs, slots and notches to aid in the building process.

The first step I took was to cut off the remaining cheek. I love the flush-cut saw for jobs like this.




Next, I added some glue where it was missing from the joint on the sides of the fuselage. Here's where the glue went.



Last edited by grosbeak; Oct 31, 2014 at 08:06 AM.
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Oct 25, 2014, 05:56 PM
Illegitimi non carborundum
grosbeak's Avatar
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The first thing I installed myself was the paper servo lead tube, from the cockpit to the tail. Cutting it to length:




Routed from front to back and secured at each bulkhead with cabinetmaker's glue.

Oct 25, 2014, 05:58 PM
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Next - the servo tray. It's not mentioned in the manual; Dany tells me that's because a lot of builders choose to put elevator and rudder servos in the tail. I'm planning on a pull-pull rudder, so I'll use the tray.




After I had glued the tray in I noticed a part, also unidentified in the manual, that looked like a backplate for the tray. I figure it'll work equally well on the top or bottom so I used a pair of servos to mark the hole. Holes drilled, I glued it in place and used servo screws to clamp it for curing.




The next thing I installed was a brace. The doublers forward of the brace push the fuselage out at the top; this part pulls it back together. Identified as F4A in the manual, it was not cut out of the specified sheet for whatever reason. Easy enough to fabricate, though. 1/8" ply.




I ran a thin bead of cabinetmaker's glue along the edges of the joint for a little extra holding power.

Oct 25, 2014, 06:12 PM
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I struggled with understanding how the empennage is built but the light bulb clicked on last night - it's made from 3/8" balsa sheet. There are three 48" sheets in the kit; two get edge-glued together and the last is cut in half; the resulting 24" pieces are also edge-glued.



The next step is to attach the relevant plan sections to the sheets with contact cement. Before I could do that, I needed to cut the plan to fit.



It was only after I'd cut the plans that I got the advice to have them copied first, but the only plans are for the empannage - the wing is framed up in jig provided in the kit.


One of the next steps is to sheet the top of the fuselage aft of the cockpit. As I was contemplating this step I noticed these notches.




Not sure what they're for - perhaps another stiffener to keep the top of the fuse in line? Once again, no mention in the manual and I welcome your opinions. I cut a piece to fit but I haven't glued it in place yet.

Oct 27, 2014, 02:46 PM
ARFs Are Me
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Nice start !

I've looked at this kit as a possible home for my G-26.
Oct 28, 2014, 02:07 AM
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Quote:
Originally Posted by TomCrump
Nice start !

I've looked at this kit as a possible home for my G-26.
Thanks Tom. I'm guessing it'd be a good fit.
Oct 28, 2014, 02:08 AM
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Good progress today. First, I installed that piece I cut for the fuselage notches.




Next came the sheeting of the upper fuselage.



Oct 28, 2014, 02:18 AM
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While the sheeting glue cured I turned my attention to the 3/8" balsa I edge-glued several days before. Time for the empennage parts.

Smaller sheet first. I taped the plans along one edge after checking for straightness.




I bought this spray adhesive at a local craft store.




With the plans hanging from the tape I sprayed the sheet with the adhesive.




After waiting for one minute per the instructions on the can I pulled the plans taut, smoothed them out and stuck them down. Luckily this adhesive allows some repositioning so I was able to deal with the few small wrinkles that occurred.



The lines on the drawings are fine and hard to see in photographs - this sheet holds the vertical stabilizer, its forward fairing, and one elevator.
Oct 28, 2014, 02:26 AM
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The longer sheet was done in the same fashion.




While the adhesive cured I turned my attention back to the sheeting on the fuselage. I cut off the overhang with a flush cut saw.




After a first go with some coarse sandpaper it looked pretty good.




I added a little glue the joint after the cockpit where the angle changes. Smoothed down with a finger - one of the reasons I love working with Lee Valley Cabinetmaker's Glue 2002 GF.

Oct 28, 2014, 02:32 AM
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While that glue cured I took the empennage parts to the band saw to cut them out.




Then over to the sander to shape the edges.




Horizontal parts...




and vertical parts.



There is still a bit of shaping to be done but apparently that is supposed to come later.
Oct 28, 2014, 02:37 AM
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I bagged the small tail parts and put them aside for now. Back to sanding the fuselage.

There was some tearing from the sawing.




Time for some filler.




Mixed up.



I've applied the filler and will sand that down in my next shop session.
Oct 28, 2014, 03:11 AM
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I'll be starting the wing soon but before I can do that I need to address a gap in my understanding.

There are two pieces of ply that are stapled to the work table at the beginning of the building (red arrows). From the instructions: "Locate the wing rib support plate W14 and staple it to your work table through the wax paper." The long piece that extends to the right is W14 on the plans sheet; the short piece at the wing root is not identified; in fact, no reference to this piece is ever made in the manual (scrap?).




At first I assumed they were part of the jig; I still think that's the case for the piece at the wing root. However, the notch in the long piece (blue arrow) appears again later, apparently part of the wing. So now I'm pretty sure that W14 does become part of the wing.




At no point in the manual does it state anything like, "Remove W14 from the work table by prying up the staples".


If I had to guess I'd say that by "work table" they were referring to a large piece of something flat from which W14 could easily be separated - like drywall. Does this sound reasonable?
Oct 28, 2014, 04:01 AM
ARFs Are Me
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I thinkthey are telling you to pin (staple) W14 to your work bench.

My bench has a homasote top. I don't find drywall to be a satisfactory build surface.

The instructions are "unique", but the pictures sre pretty good.

I'd say that W 14 is part of the wing. It looks like the ribs are keyed into, insuring proper alignment.
Oct 28, 2014, 09:10 AM
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Quote:
Originally Posted by TomCrump
I thinkthey are telling you to pin (staple) W14 to your work bench.

My bench has a homasote top. I don't find drywall to be a satisfactory build surface.

The instructions are "unique", but the pictures sre pretty good.

I'd say that W 14 is part of the wing. It looks like the ribs are keyed into, insuring proper alignment.
There's a dealer in Ottawa who stocks Homasote 440 SoundBarrier but they won't have any until next week. Rona has some acoustic panel - thinking it's similar stuff.
Last edited by grosbeak; Oct 28, 2014 at 09:54 AM.
Oct 29, 2014, 05:04 AM
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After a little research I came across acoustic panel as an option so I decided to try that. I found some at Rona here in Ottawa. I wasn't sure what to expect but it is dense, flat and takes staples well so I'll give it a try.



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