Tail feather Gussets

[scottiniowa]

Has anyone really gone over how big is big enough for the tail feather gussets, By this, I mean, say one of those that wraps around the .750 tube- should be say X deep on a rib?  2" or 4" or any other implied distance.

I fully understand the forming process, and using paper templates, but was more curious if this was just one of those areas that builder is just expected to wing it?

I will be showing Examples of the parts, but thought I would check first if there were any applied rules here that I was not aware of for the sizing of the gusset.

I do have the recommended rivet spacings and edge clearance notes.

[joecnc2006]

I was kinda thinking the same thing, I wanted to draw them in solidworks and see the different sizes, I would like to cut them out on the cnc machine, lay the sheet down, nest the parts and hit the start button.
For the proper overlap I was going to see if i could find other control surfaces of different planes and try to determine the length. I was thinking about a 3"-4" overlap, but this will depend on the angle intersection.

[Steve]

Has anyone really gone over how big is big enough for the tail feather gussets, By this, I mean, say one of those that wraps around the .750 tube- should be say X deep on a rib?  2" or 4" or any other implied distance.

I fully understand the forming process, and using paper templates, but was more curious if this was just one of those areas that builder is just expected to wing it?

I will be showing Examples of the parts, but thought I would check first if there were any applied rules here that I was not aware of for the sizing of the gusset.

I do have the recommended rivet spacings and edge clearance notes.

Ways & Means of a Tube & Gusset master - Graham Lee:

[Dan_]

 but thought I would check first if there were any applied rules here that I was not aware of for the sizing of the gusset.

Here is a study on it...  http://arcstructural.com/images/gussetstress.pdf

They seem to be saying that any gusset material outside of the 30 degree line is just adding weight.  (figure 4)

[scottiniowa]

Thanks Dan. 
Now that is the kind of thing that I'm talking about.
While it may seem complicated, it will determine a "reason and what for" to the  size/design of these gussets based on something.

I suspect that a simple formula will be deduced from this.  Such as,  
Tube dia. x 4 equals max length past a change of direction as well as distance beyond this change.  Something simple anyway.

I will do a study and then report for final review.

thanks again.

[scottiniowa]

I will do a study and then report for final review.

thanks again.

Ok, study done and to me it is interesting in the fact that the answers really don't seem to out there. For these reasons it seems to be a owner design preference.

• in view three different folks tail feather gussets, three different interpolation's of the plans were used.  i.e.  all three were different
• .020 was in common use
• While the rivet call out spacings on the .net and books are all about the same, many builders ignore these rules and tend to space rivets further apart than the max recommended.
• I saw no cases where builders spaced to close to edge, but several cases where they were spaced well past recommended distance (basically adding weight with no strength gain)
• I never did find any recommended length of gusset as per dia. or thickness of sub structure,  (i.e.- 3X's thickness for corner gusset or anything like that) Though there are many references to bridge gussets, but the math would not allow to go all the way down to .020 thickness, if applied-- you would have about 1" x 1" corner gussets. I didn't see anyone go that small.
• I searched in vain on my plans and two others, for any kind of dimension, only to find out they are on some plans but not all plans.
• Several applied the warm fuzzy logic of-  If it looks and feels good, it must be good.  I was hoping for more. 
• This area of the aircraft seems to be built with the line above fully in mind as it is lightly covered for the XL and many other birds of similar build.

Conclusion:

• I will design the shape to what I feel is the best shape/size for the job
• I will do the Dawn Patrol way of fastening, which is certainly fast and effective
• I will use 3M 2216 as a epoxy bond, this will allow for minimal rivets but make the tail surfaces "throw away" as there would never be a removal way if dinged. This basically uses the time vs value approach, as I could rebuild brand new fast than repair of just about any surface. Labor vs material cost,  Material cost will win with the lowest score.
• I will design around the Engleman hinge method, again, time vs money thing-vs-what really works well.
• Key here is a little bit of time making patterns will be well made later on during build with NO rethinking later.
• I will try to post these results under the down load section in a few weeks. Under "Tail Gussets" or similar. 

AS always, only then will some come out and tell me "what is wrong", no problem, I will always consider the arguments for and against a design. Of course I will always wonder why the arguments for the "how to" did not come right away.. But that is human nature.  Everyone has a theory, most don't apply theory until after they think they see a problem. But I like theory, with one of the best and most scientific being that the rings of Saturn are almost entirely composed of lost Airline luggage.. its got to go somewhere I think.

[joecnc2006]

Scott,
Looking forward to what you come up with.

[Dan_]

Standard operating procedure apparently is make the gusset larger that the required number of rivets by an amount slightly bigger than the edge allowance.  (twice rivet hole diameter)  

Required number of rivets should be discernible from the plans, usually never less than 3.  

Rivet spacing (pitch) (gauge) is a min of 3 times rivet diameter, and a max of 12 times.

Draw a circle around the rivet holes at the corners of your gusset the size of the edge distance allowance, and simply connect these with a tangent line drawn from each circle.   

No formulas.  

Trim and you have your gusset.  Here's your reference material...


http://www.eaa65.org/downloads/Ch01%20Standard%20Methods%20and%20Practises.pdf

[scottiniowa]

Standard operating procedure apparently is make the gusset larger that the required number of rivets by an amount slightly bigger than the edge allowance.  (twice rivet hole diameter)  

Required number of rivets should be discernible from the plans, usually never less than 3.  

Rivet spacing (pitch) (gauge) is a min of 3 times rivet diameter, and a max of 12 times.

Draw a circle around the rivet holes at the corners of your gusset the size of the edge distance allowance, and simply connect these with a tangent line drawn from each circle.  

No formulas.  

Trim and you have your gusset.  Here's your reference material...


http://www.eaa65.org/downloads/Ch01%20Standard%20Methods%20and%20Practises.pdf

Thanks Dan!  Certainly makes me smile that once I say HOW I am going to proceed, that a simple and concise STANDARD comes forth.   In a sense this is a formula or if one wishes, a method to calculate the size.  AT LEAST it is something to go by. So many thanks.

Interesting, on the statement "at least 3, and discernible from the plans. The very reason I started this, as this very number question was brought up, and has gone un-answered for a long time. That simply being-- does a run comprise of 1, 2 or 3 rivets?.  And if you want to bring the plans into this... hummm,  I have a plan view of a less than 90 degree corner with 4 total rivets (2 each way) another corner with a brace, that has runs of (3 one way, 2 @90 degrees and only 1 on a brace) still another with two braces (2 rivets on the long side, 2 on a brace and 2 on another brace)  So as you can see, there is NO rhyme or reason to the plans drawings that I have. And I  certainly have found that NOT all XL plans are alike.   Thus the very core of my looking into this. 

I will be the first to tell all that my way may not be correct, but at least it will be consistently wrong.  ;-)  But now, it will be consistent to what Dan provided and that is far better than anything else that has come forth.  WE all know it works by many ways. So very true for low and slow aircraft.   Stay tuned.

[Dan_]

 Interesting, on the statement "at least 3, and discernible from the plans. 

I guess the only hard and fast rule is, there are no hard and fast rules...

[Dan_]

Scott,
A thought occurred to me about gussets wrapping around a tube.  I'm thinking of the rudder area.  

From the reading material we have found on it recently, it seems to me a good way to go about it is to make both ends of the gusset the width determined by the edge allowance.  Length of this area decided by desired number of holes and rivet pitch.  Then let the width of tube wrap part be determined by a tangent line drawn from the end hole edge allowance circle at 30 degrees or slightly more.  

I would be interested if drawing one out like this looks to be sized correctly to you.  I'm sure I am not alone on this.

[scottiniowa]

Scott,
A thought occurred to me about gussets wrapping around a tube.  I'm thinking of the rudder area.  

From the reading material we have found on it recently, it seems to me a good way to go about it is to make both ends of the gusset the width determined by the edge allowance.  Length of this area decided by desired number of holes and rivet pitch.  Then let the width of tube wrap part be determined by a tangent line drawn from the end hole edge allowance circle at 30 degrees or slightly more.  

I would be interested if drawing one out like this looks to be sized correctly to you.  I'm sure I am not alone on this.

Dan, that could easily work, but I will try to share what the "Murphy Guide"  showed and found this to be a easy-peasy, though slightly time consuming method.

  It eliminates the 30 degree calculations and gives good shape quickly, though one part at a time. Going to try to post a few photos of prelim work, Now that I have a guide, I think this will work  consistently.

 A second note, if folks feel it should be one rivet larger, (over all size)  it would simple by adding that distance (1") to the outside shape (not the bend area)   All good.

Please note, this is intended to be a guide, unless you machines to precisely bend the center wrap bend on the center line- (I have such machine and it is still hard) This will be a shape than anyone can cut out, do the bend as close as they can to the center line. Do a quick check fit, then mark drill holes, and probably do the Dawn Patrol Method of drill and popping, no clecos. Again time vs wasting time.

[liteflyt]

Scott, just eye balling your ( H stab A-5.jpg (23.63 kB, 1024x532 .)), it appears your rivet nearest
the end of the tube(s) is placed too close to the end of the tube....or do  I need glasses?

[scottiniowa]

Scott, just eye balling your ( H stab A-5.jpg (23.63 kB, 1024x532 .)), it appears your rivet nearest
the end of the tube(s) is placed too close to the end of the tube....or do  I need glasses?

Thanks for observing the photo.
Please view this jpeg, while it looks busy, this shows the edge clearances are NO less that 2 x's D of 1/8" rivet. Both on the ribs and tube. While I don't like this bottom tube start location, it is well beyond .25" from the edge..

[joecnc2006]

Are you coping the aluminum at these areas? I would think this would weaken the ends of the aluminum sine they are not welded and the placement of the rivets at the ends would not help, would it be better to move them outward away from any coping. I'm just wondering since we are discussing this here.