Building the (old) FLYLINE Great Lakes 2T-1A kit (18)

All those bits and pieces are beginning to look more and more like an airplane in the process of becoming, and I’m getting anxious to see how she’s going to look with covering on the bare structure. However, there are a few details that have to be attended to before I get to break out the fabric and dope. Let’s go through them one at a time.

The small stuff counts. The tailpost, or vertical fin trailing edge, has to be relieved (cut out) for the elevator joiner to fit in place so that the elevator will lie up against the trailing edge of the fixed horizontal tail. I could have done this earlier, but overlooked it. I cut out a rough notch with a No. 11 blade and then rounded and cleaned up the opening with a wood rasp.

We need control horns on all the control surfaces. Instead of molded plastic fittings, this kit employs horns cut from 1/16" ply printwood. At the expense of a bit more work this is a perfectly good way to make control horns for a model this small and light. In relation to the forces generated in flight and transferred through the control connections, 1/16" aircraft plywood with carefully drilled holes is plenty strong enough, but I would not use this option on a bigger model. This is the elevator horn, inset into the reinforcing gusset on the underside of the right elevator half and glued securely into place. I drilled clevis attachment holes as you can see, along with two more holes that are hidden down inside the glued joint to improve strength.

Same game with the rudder. When you add a control horn (or any other protuberance) this way, be sure that there is some flat/level structure extending away from the attachment line to provide a secure base for the covering to be added later, otherwise you'll end up with a wrinkled mess instead of a smooth transition. I added the aileron horns in the same way.

The kit provides material for a scale pilot's headrest as two halves on a printwood sheet. I have cut those out, glued them together, and carved/sanded the headrest to shape. However, the kit instructions made no provision for mounting the headrest other than showing where it is supposed to go and implying that you might glue it in place on top of the finished covering. That would be guaranteed sloppy building...glueing any structure to covering instead of to solid structure is always a bad idea. In this case I needed to add structure where none had been called for, so I included a few more filler insets a bit longer than the ones already in place to fair in the top deck stringers. I'll fit the covering around the headrest later.

I found an oversight in the original engineering. Look at the top right corner where the cut-out lower wing base plate forms part of the fuselage side structure. As designed, the kit made no provision for the step, or discontinuity, between that base plate and the outer surface of the balsa sheet covering on the side. Trying to do a fabric overing over that would have been another guarantee of gross wrinkles and sloppy work. I added a filler/fairing of 1/8" sheet balsa to blend the sheet with the base following the curve the covering will naturally take from the surrounding structure.

Here's another look at the same fairing from the side. It's easy to see how the covering will be supported everywhere to provide a smooth surface that looks like it ought to be part of an airplane.

The kit instructions suggest mounting the rudder and elevator servos on plywood plates, but don't offer much detail. I don't really have any problem with this, since there are so many RC equipment options out there that no two modelers are going to use the same stuff, and you must do a bit of design work to fit what you have. This is a piece of 3/32" aircraft plywood cut to fit inside the rear cockoit area from the bottom (through the lower wing base opening) and to provide some extra structural stiffness to the fuselage assembly along with a place the hang the servos.

I used Airtronics 94803 Micro Digital BB servos for this airplane. Here the rudder and elevator servos are in place on the mounting plate. You will notice that I have cut off the extra/unused arms from each of the servo output wheels. This is a judgement call...these two will forever be one-armed outputs, but I have elimated a bit of exces weight and, more important, extra protruberances that might otherwise have a chance to snag on anything loose inside the compartment.

This is a piece of 1/64" aircraft plywood which will become a locating/reinforcing plate for the outer tubes of the concentric rudder and elevator pushrods. A old-style paper punch works very well for making neat holes through this very thin plywood if you can find one of the correct size to match what you need done.

This is the control tube locating plate in place.

I am using two aileron servos, eacn on its own channel, for complete, independent adjustment of each aileron. The servos will mount to the floor of the open bay built into the lower wing center section and drive the ailerons through concentric tube-and-cable pushrod assemblies. Here I am inserting the right outer tube through the inboard ribs where they are covered by the center section sheeting. I have fed a thin, stiff wire through holes drilled in the ribs and am using it as a guide to thread the tube into place.

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Comments (3)

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  1. Bart Hunt says:

    Looking good, this is one of the best build sites I’ve seen on the Web.

  2. Mike says:

    You mention not gluing structure to covering but aren’t the louvers on a successive step glued to a precovered cowl? Could you precover the turtledeck then sand the silkspan and still get a good bond? I also noticed you glue the control horns in prior to covering, is there an advantage to this vs after covering? Thanks for all the great tips!

    • Robert Benjamin says:

      Mike,

      You get points for catching that one. I should have mentioned why I did that. Gluing structure to covering is always going to result in a compromised joint. The classic case might be a sheet balsa vertical tail glued directly to covering on a pre-fabbed fuselage…the fin will fall off at the first opportunity. Structural strength was the least of my concerns in making those louvers. I doubt you could put enough pressure on one of them to break it off without crushing and tearing the balsa first. In that case I was more concerned about maintaining a decent base finish in the area between the louvers and wanted to keep the previously doped and sanded silkspan intact to that end. Same game with the headrest…you can tolerate a less than perfect joint there in the interest of a better finish, as there is never going to be enough load to worry about on the fairing.

      As for the control horns, it’s my habit to put them in early so I can see exactly what’s happening and not worry about alignment and glue wetting. You could do it the other way just as well, if you wanted to.

      Bob

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