Lucky Boxes ? ? ? ? ?

[Bill Diedrich]

Getting back into control line and have ordered a few plans, I see
on a couple of them they show "lucky boxes" on flaps and or elevators,
would someone please explain what they are and what purpose they
serve.  Hopefully not a dumb question 

Thanks,

Bill D.

[Ward Van Duzer]

First: go here and look at HORN CLIPS

http://www.stunthanger.com/tips.htm

Second: look at my signature block!

W.

[Allan Perret]

Purpose is to strengthen that part of the flap so you can tweak the horn to get wings level.  
Balsa alone is not strong enough to allow tweaking.  
I build my lucky boxes from spruce or bass sticks. 
Might have some pictures filed away if you are interested.

Where abouts in Louisiana is Ventress ?

[WhittleN]

Bill
They are what Allan said, reinforcement for the flaps and elevator surfaces.  They are called “Lucky Boxes” because Lucky Pyatt first came up with this style of reinforcement and Eric Rule (RSM) coined the term.  Just in case you needed more information than required.
Norm

[Tim Wescott]

If you're building a plane that has dihedral or sweep at the flap hinge line, then a rigidly mounted flap horn would have to flex.  This works for a slight angle, but for larger angles you build a box into the flap that the flap horn works in.  The horn can sweep an angle in the box, while still actuating the flap with low friction etc.

This plane http://stunthanger.com/smf/index.php?topic=18714.0 works great with lucky boxes in tail, for instance.

[Steve Helmick]

Not only to adjust for dihederal, anhederal, or swept hingelines, but also to allow removal of flaps and elevators by using a single music wire pin for all hinges on each surface, i.e., one pin for each flap, two for both flaps, and same for elevators. There are a few variations on the theme, but the basic idea is the same. Some folks use round tubing mashed into oblong tubing, some use rectangular tubing, and some just have an open slot in the end of the flap.

I used MapQuest to quickly find Ventress (45 minutes NW of Baton Rouge) and Slidell  (40 minutes NE of New Orleans). Y'all are not exactly neighbors.  Steve

[Peter Nevai]

Additional detail.

If you examin  the plans, lucky boxes allow for horizontal movement of the flap or elevator horn within the box but do not allow for any vertical free play. Like mentioned allows for non perpendicular trailing edges of wings and stabs. A easier solution to implement than split horns (A seperate horn for each flap or elevator)

[Bill Diedrich]

Where abouts in Louisiana is Ventress ?


Yes Ventress, La. is approx 32 miles NW of Baton Rouge, approx 45 min
drive 1 hr 35-40 mins to New Orleans depending on which route you take
almost 2 hours to Slidell, La.

Thanks for the info on the "lucky boxes", guys reaslly asppreciated.

Bill D.

[FLOYD CARTER]

I've found that "Lucky Boxes" made of birch ply don't hold up long, because of the necessary sliding between the box and the wire.  I use 1/16" G-10 glass-epoxy (circuit board material), which does not wear at all.

Floyd

[Bob Whitely]

Hi Guys,

The reason for the "Lucky Boxes" came about because many years ago I had
built an aircraft with an andedral stab and had to figure out how to make it work
using just one elevator horn. It was obvious that the horn wire had to slide in the
elevators so as not to bind.  I used phenolic for the top and bottom of the box
and 1/8" ply to make the sandwich. Worked just fine. Lucky was my draftsman
and that is where they first appeared and  got their name.  They were never meant
to do anything more than make the flaps or elevators that had any angle to them
work without binding and still work without any slop in the system. RJ



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