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Old Apr 05, 2012, 09:01 PM
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tankreefer's Avatar
USA, AL, Odenville
Joined Jun 2010
56 Posts
Question
whats the best way to get tail feathers straight

I got my cub covered, time to glue on the horizontal and vertical stabs. What's the best way to get them straight? Do you eye it or does it need to be perfectly straight?
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Old Apr 05, 2012, 10:19 PM
Build to Fly? FLY to BUILD!
Legot's Avatar
United States, AZ, Gilbert
Joined Nov 2009
1,104 Posts
Quote:
Originally Posted by tankreefer View Post
I got my cub covered, time to glue on the horizontal and vertical stabs. What's the best way to get them straight? Do you eye it or does it need to be perfectly straight?
Don't eye it. Get a proper 90* angle and do it right. If It's not straight, the model will not fly as it should, and even though you may be able to trim it out, it will never fly as well as it would with properly installed stabs. And trust me, eying it doesn't work well anyway, even if you close one eye and be really careful, it would be off by an annoying amount.

For the horizontal, I like to put the plane on a solid (level) surface, and make sure that it the whole top of where the stab goes is perfectly level (sanding) then I do the wing thing with the string, where you mount the wing and make sure the distances from wing to stab are equal on both sides, then I go and put Epoxy or polyurethane glue on and glue the stab, and add weights to the center, not the sides!

After that's dry.........

For the vertical. I pin a string on the center of the plane at the nose, and run it to the center at the tail, then draw a straight line on the horiz- stab along that string. Then I go and use a 90* angle and make sure the vertical stab is ready, then I epoxy it on, making sure it's all lined up, and perfectly vertical.

That's just the way I do it, there are most certainly other ways, that might even work better.

And then, you can eat. (<---idk what that's about) Post pictures of whatever you're working on please!
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Old Apr 05, 2012, 10:39 PM
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tankreefer's Avatar
USA, AL, Odenville
Joined Jun 2010
56 Posts
Thanks for the help legot. I will try it out. Here is a couple pics. It is an alien aircraft j-3. This is my first build and first balsa plane. The build went pretty good, but the covering was a pain. It turned out ok I think. Thanks for the help I will try the string from the wing.
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Old Apr 06, 2012, 01:28 AM
If it flies - I want one!
Petem's Avatar
Werribee, Victoria, Australia
Joined Jul 2008
1,034 Posts
VCR tapes

Tankreefer,
Here is my favourite - about the only use left for old VHS tapes now, but they are nicely square and accurately dimensioned.
The little bag of lead shot keeps the pressure on while the glue dries.
Preferred glue is white glue for all wood-to-wood joining: clean, clear, easy to clean up and gives time to work.
Cheers,
PeteM
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Old Apr 06, 2012, 10:03 AM
Redacted per NSA "suggestion"
dedStik's Avatar
United States, VA, Virginia Beach
Joined Feb 2012
5,419 Posts
Petem that is a phenomenal use of old VHS tapes. I'll have to remember that on my next build.
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Old Apr 06, 2012, 10:50 AM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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Each model is a little different when it comes to jigging them for alignment. But the whole triangulation from the wing tips or alignment with the fuselage center line in some manner is essential. "Close enough" simply isn't close enough for this job.


If you don't have the wings ready to use another option is a center line and 90 degree cross line on your building board. This reference can then be extended upwards using tri-squares, cheap machinist's squares or known good quality tricks like the VHS cassetes. If the fuselage covers your center line up then simply draw two parallel lines equally spaced out at the width of the fuselage and use those to center the fuselage at the cabin area.
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Old Apr 06, 2012, 11:35 AM
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USA, AL, Odenville
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Thanks for all the help! I do have my wing built,I will put it on and try that along with the string down the center line. The vhs tapes are a good idea petem,however I don't have any lying around.
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Old Apr 06, 2012, 10:16 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
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Blocks of wood that you know you cut square work just as well.

The key to all this that we've tried to impart to you is to start with a straight line which you line up the fuselage to and then build up from there in even distances and using right angles or equal size triangles. The diagonal string idea off the wing to the centerline back by the tail is an example of IDENTICAL triangles. To make this work you need to accurately center the wing first and THEN you can measure from the center line back at the tail to the wing tips. If you don't first center the wing then you do not have identical triangles. And if you don't have this part the same side to side then using the diagonal string idea will actually set the wing up crooked.

So keep in mind the basics when you're doing all this stuff. You need accurate measurements and known reference lines and some accurate 90 degree blocking to do all this.

It really is the same as land or road surveying but in a small scale.
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Old Apr 06, 2012, 10:38 PM
Art Schmitz
United States, TN, Crossville
Joined Jan 2012
392 Posts
I use stips of double stick carpet tape to temporarily hold a centered aluminum T bar sanding tool across the wing saddle at a right angle to the fuse. centerline.
Next, I trammel the hor.stab and lightly center mark it to the fuse.
Then I sight past the T bar to level the stab and then attach it.
The v.stab gets lined up with a r.triangle or carpenter square on parallel position lines.
Some times it is necessary to relieve the 90 to accomodate the fuselage.
A strip of masking tape from the v.stab to each h.stab tip is an easy way to hold it til the glue dries.
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Old Apr 07, 2012, 12:14 PM
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hoppy's Avatar
Space Coast
Joined Oct 2000
20,912 Posts
After all the measurements, right triangles, etc, always do an eyeball of the result. Look from the front down the middle of the body, does it look right? Sometimes the tools can fool you but the eyes always tell the truth. I do use the tools to set it up, but the final test is the eyeball.
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Old Apr 07, 2012, 08:50 PM
I'm a pilot... 100 yrs to late
Thermalin's Avatar
USA, FL, Palm Harbor
Joined Jan 2005
3,430 Posts
Agree with hoppy... I take visual refernces to wing or to see it looks right after all the measurements and right angl Didnt see it mentioned but use 30 min epoxy so you have lots of time to duplicate the measurements taken priorto gluing.
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Old Apr 09, 2012, 06:19 PM
Registered User
United States, MS, Columbus
Joined May 2002
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I've seen these used to good effect too. I went out and bought one myself, but haven't built anything since to try it out.

http://www.lowes.com/pd_108923-353-8...vel&facetInfo=

-Al
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Old Apr 09, 2012, 06:36 PM
KE your cub.
Curare's Avatar
in the gutter, again....
Joined Jun 2005
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What legot said.
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Old Apr 09, 2012, 06:45 PM
Build to Fly? FLY to BUILD!
Legot's Avatar
United States, AZ, Gilbert
Joined Nov 2009
1,104 Posts
That's a really clever use for VHS tapes as building jigs. It's great because They're basically all perfectly perpendicular edges. I'll definitely be using that sometime, we have a ton.

That's a nice looking cub reefer! Hope it goes well for you.

Quote:
Originally Posted by Curare View Post
What legot said.
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Old Apr 10, 2012, 09:16 AM
It must have a machinegun
Scaledown's Avatar
Perth, Western Australia
Joined Sep 2004
1,273 Posts
After 20 years of building I've resorted to eyeballs. Admitedly not everyone has straight eyeballs. Some have all the pictures in their house hung crooked.
Anyway I look at the alignment from 4 directions before concluding that its straight enough to glue.
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