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Old Apr 22, 2013, 09:10 PM
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First plan build - modifying tail structure

Hi All,

I'm working on my first plan build, the Blue Flash from Fly RC a few years ago. It's a 50" span low wing sport plane. The plans call for 3/16" sheet tail structures, but I'm thinking of changing things a bit and doing a built up tail. I've looked at several other plans to get ideas of how to do it and I think I've come up with a good design, but I'd appreciate any critiques or suggestions.

I've attached my marked up plans. I planned to keep things 3/16" thick. The outer perimeter would be build from 1/4" wide 3/16" strip. The TE of the stabs would be 1/2"x3/16". The LE of the rudder and elevator would be 3/8"x3/16". The diagonals would be 1/8"x3/16".

Does this look ok?

Thanks,
Andy
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Old Apr 22, 2013, 10:53 PM
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Brad looked at this and recommends wider stock for the TE.
You won't be able to be much of a tapper with that narrow
of stock.
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Old Apr 23, 2013, 09:17 AM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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Hi Andy
Use your style of structure all the time on models of around that size. Your plans look fine, would suggest 1/4" wood instead of 3/16"
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Old Apr 23, 2013, 09:47 AM
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Thanks for the responses.

Kimber, I planned to keep it flat, not tapered.

Dereck, So 1/4" square stock for the perimeter. I'll need to modify the slots and tail post on the fuselage plan to match that. Sounds good.

Andy
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Old Apr 23, 2013, 11:34 AM
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I second the idea to use a stronger trailing edge, in fact I would use a 1/4 inch spruce for that member as it will take the brunt of the load and will vary in both directions; i.e. will experience both negative and positive G loads. Your lay out looks good.
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Old Apr 23, 2013, 12:01 PM
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Illinois
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All those nice big curves are really wanting to be laminated!

A friend of mine built one of these at 36" or so, in fact it was the last model he built before passing away. It's a great flyer. You're gonna love it!

Andy
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Old Apr 23, 2013, 01:25 PM
Visitor from Reality
United States, VA, Arlington
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Quote:
Originally Posted by ajreynolds View Post
Thanks for the responses.

Kimber, I planned to keep it flat, not tapered.

Dereck, So 1/4" square stock for the perimeter. I'll need to modify the slots and tail post on the fuselage plan to match that. Sounds good.

Andy
Flat is good. It works for those odd models built from the Sig Four Star ** series.

Laminated curved outlines are The Best! A little work needed, sure, and an overnight drying session, but for light and strong, you can't beat them.

One high stress part is the tailplane TE. I'd use 1/2" x 1/4" for that - stronger and deep enough for the hinges. Really cool is 1/2" at the centre, tapered to 1/4" at the tip, but that's likely me making work

After all, why use one piece of wood when six will do?

D
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Old Apr 23, 2013, 07:32 PM
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Quote:
Originally Posted by Dereck View Post
Flat is good. It works for those odd models built from the Sig Four Star ** series.

Laminated curved outlines are The Best! A little work needed, sure, and an overnight drying session, but for light and strong, you can't beat them.

One high stress part is the tailplane TE. I'd use 1/2" x 1/4" for that - stronger and deep enough for the hinges. Really cool is 1/2" at the centre, tapered to 1/4" at the tip, but that's likely me making work

After all, why use one piece of wood when six will do?

D

I did a laminated curve on the vertical for my stick built stick, and I used CA. I had to be careful, but it worked, and did not require the long drying time.
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Old Apr 23, 2013, 08:43 PM
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Use balsa and sink some end grain dowel rod into the stab, bottom of fuse and fin TE for mounting bracing wires. Looks the part, is stout and lightweight.
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Old Apr 24, 2013, 12:25 AM
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Thanks for all the input. I hadn't thought of laminating, but that sounds interesting so I might give it a shot. I'll also increase the thickness to 1/4". For the laminated outline, I should be able to do each half of the horizontal stab/elevator as a unit, as well as the vertical stab/rudder. Then separate after I've added all the internal structure. Correct?

If I keep with my 1/4" wide outline, should I go with 4 strips of 1/16" or 8 strips of 1/32" balsa? The 1/32 should bend easier I would think. Soaked first of course.

I'll also go with spruce for the TE.

Andy
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Old Apr 24, 2013, 10:29 AM
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Use the 1/32" stock. It will swell slightly when wetted - 4 layers of 1/32" will be about 3/16" thick. There are lots of good helps out there for laminating. Check what epoxyearl has in his giant scale Sparky thread.

Andy
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Old Apr 27, 2013, 02:04 PM
I need a bigger garage...
ajreynolds's Avatar
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I read through the Sparky thread. Good info, thanks. For my project, would 4 layers of 1/32" be good enough, or should I go with 5? I'll be making the tail 1/4" thick.

Thanks,
Andy
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Old Apr 27, 2013, 02:40 PM
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Do the lamination first, the entire outline. Then put the structure in
half of it. As in do the stab, put in all the structure including the
TE. Then cut the lamination and separate the finished part, Leaving
the remaining lamination on the plans. Other wise, you will end
up gluing the TE of the stab to the LE of the elevator.

Don't know if this makes sense??



BTW, any comments about my art work will get you off the
Christmas list real fast.....
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Last edited by Kimber; Apr 27, 2013 at 02:53 PM.
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