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Apr 25, 2020, 09:55 PM
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Awesome job, Kenneth. I've never even imagined making precision, matching fairings like your method. Clever idea for the fin servo mount too. Thanks for the detailed photos & explanations.
May 02, 2020, 04:20 PM
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Kenneth Paine's Avatar
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Wing Servo Boxes


Following on from the last photo in post #135, the pictures and comments below show how I made the servo boxes.

The top skins over the servo wells became very weak and easy to push in after routing the servo wells and the structural integrity of both wing panels was compromised as well, rendering all my bluster on structural calculations in post #36 meaningless. I clearly hadn't thought things through when I decided to go down the stressed skin path, a good choice for pitcherons but not so good when you need servo wells cut out. No F3B style shenanigans for this Discus.

Anyway, building the servo boxes offered an opportunity to restore an element of the wings' lost structural integrity.

The first step and crucial to wing structural integrity was to reinforce the top skin over the servo wells. This I did by gluing 1/64” ply to the servo mount and then epoxying the assembly to the bottom of the servo well with the servo in place to keep the 1/64” ply flat (not shown). Now the top wing skin over the servo wells is as pressure resistant as on the rest of the wing.

The rest of the wing boxes were assembled dry with 1/32" ply. Have you noticed what great wicking qualities laminating epoxy has? Most the of the pieces were kept in place by interference fit while the epoxy was applied and set. Follow the comments for each picture.
May 02, 2020, 04:29 PM
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Kenneth Paine's Avatar
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Quote:
Originally Posted by flyingfever
Awesome job, Kenneth. I've never even imagined making precision, matching fairings like your method. Clever idea for the fin servo mount too. Thanks for the detailed photos & explanations.
Bob,

Thank you for your kind words.

Kenneth
May 07, 2020, 04:21 PM
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Kenneth Paine's Avatar
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Canopy Frame


The original canopy and frame that came with the fuselage is rather poor shape so I ordered a new set from Rippin, but something got lost in the translation and I only received the canopy. How to make my own has been troubling me for some time but I finally bit the bullet, made a decision and pressed forth.
May 08, 2020, 01:42 AM
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Jets:)'s Avatar
Nice work on the fillets around the fuselage wing root junction.
I might use that method in future.
May 08, 2020, 08:00 AM
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Kenneth Paine's Avatar
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Quote:
Originally Posted by Jets:)
Nice work on the fillets around the fuselage wing root junction.
I might use that method in future.
Thanks Jets. Keep us posted if you do.
May 08, 2020, 03:43 PM
Everything is broken
JimZinVT's Avatar
I bought 2 fuses last year that were missing the canopy assemblies. A Reiher and a Habicht. I'll need to create them from scratch. So happy to watch how you accomplish this!
May 10, 2020, 12:09 PM
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Kenneth Paine's Avatar
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Quote:
Originally Posted by JimZinVT
I bought 2 fuses last year that were missing the canopy assemblies. A Reiher and a Habicht. I'll need to create them from scratch. So happy to watch how you accomplish this!
Thanks Jim. I am making it up as I go along for I have never done this before. However, I spent a lot of time developing the technique in my head. So far it seems to be adequate if a little laborious.

Kenneth
Jun 07, 2020, 12:47 PM
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Kenneth Paine's Avatar
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Update


I have been plodding along doing all the fiddly stuff that is not worth documenting such as:
  • Rudder hinging
  • Rudder pull pull cables and horn
  • Scratch built tow release mechanism
  • Wing servo wiring and installation which was a nightmare.
  • Contouring the top of the stab to blend in the ripples in the surface due to the thickness of the Kevlar hinge and the prominence of the mounting hard points (see post #57)
I hit a bit of a motivational block with the above. I like the bigger stuff like foam cutting and bagging. Anyway, I persevered and I am approaching the stage of high build primer and block sanding which I like.
Jun 08, 2020, 06:37 AM
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Kenneth Paine's Avatar
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Protecting the wing servos during priming


Because of lack of space in the servo wells and cable tubes I had to cut all the wing servo leads and solder the extensions directly to the stub cables. The six pin Multiplex type connectors used have been epoxied into the plywood wing root rib so the servos are permanently wired in now.

Given that I cannot remove the servos from the wing, the following is the way I intend to protect them from primer.

I thought the covers could be sanded flush with the wing and kept in place for painting as well but the hard-to-sand ply sits proud of the wing surface so the covers will have to be removed after priming and before block sanding.
Jun 09, 2020, 03:56 PM
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Kenneth Paine's Avatar
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Starting the Finishing Process


It has been a long time coming but I finally got round to the first stage of the finishing process: high build primer. It is all downhill from here .
Jun 10, 2020, 06:26 AM
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Kenneth Paine's Avatar
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Just a small comment…


I just wanted to say that I am delighted to see that I have NO PINHOLES where it matters. I will comment on my rudder and stab further down in this post.

My previous project using the same laminating materials as this one was plagued with pinholes which let the primer through to the foam in places causing localised subsidence or deflation of the surface which then needed a lot of remedial work. Many expert vacuum baggers recommend priming the Mylars before laminating to prevent pinholes, but given my circumstances, setting up for spraying is a nightmare for me, so I would rather not prime the Mylars before laminating. Also, I love the sight of blue foam through shiny glass when the wings come out of the bag. With this in mind, on this project my first layer on the waxed Mylar was tissue/silk span like that used by the free flight/control line traditional modellers. This tissue layer has taken care of the pin holes that have plagued me in the past as well as becoming invisible in the laminate. I recommend you give it a try.

The imperfections you see in the last photo are for different reasons:
  • Stab – The pinholes there are bubbles in the splooge that I applied to make good the top surface which was rippled due to the Kevlar hinge ribbon and the mounting hard points sitting proud of the core.
  • Rudder – The big pin hole is a gap where I put a balsa plug in the control horn slot to prevent primer getting in (See photo 2 above). The row of pin holes across the LE are the ragged edge of the heavy cloth sitting on the leading edge ribbon. I was just lazy with the sanding because that area will be tucked into the fin.

To summarise: if you don’t want to prime your Mylars, give tissue a try to prevent pin holes in your lamination.


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