Eagler's Nest

Airframes => Double Seaters => Topic started by: Peterross on October 18, 2014, 10:38:54 AM

Title: DE spars
Post by: Peterross on October 18, 2014, 10:38:54 AM

I'm trying to figure out how to begin the spars for the DE.
Page 40 of the plans leaves me with a few questions.
First, what wood is used for the vertical spacers between the upper and lower spar caps?, and second, what is the spacing dimensions for these spacers? On the drawing they look unevenly spaced, but I have no idea how they are spaced.
I'm also not sure how to make the spar doublers, or how they attached to the spar caps.
Any help would be appreciated.
Leonard, is there another drawing that has this additional info?

Thanks

Title: Re: DE spars
Post by: ParQld on October 20, 2014, 05:24:33 AM

Hi Peter,

I am about to start mine as well, The vertical spacers I believe are the same spacing as the ribs shown on page 29, ie most are 15 inch centres.
Not sure of the timber size but will come back to you as i am studying the plans also.

cheers Paul

Title: Re: DE spars
Post by: Peterross on October 20, 2014, 06:22:56 PM

After staring at the drawings a bit more, I do believe you are correct. It does become a bit more clear. So we still need to determine what size the wood pieces are.
Also, the spar doublets make a bit more sense. It appears the wood strips for the top and bottom are the width of the spar caps. Spruce filler is used to space the center out, with 1/8" plywood on the outside. I assume this is to give strength to the steel plates. Not sure where to start yet, but I may start with the doublers.
Let me know if you have any further insight. I'm not quite ready to start, as the basement is a disaster, and I need to clean so I can set up my building table. Winter in Wisconsin tends to get a bit cold. At least I will build the spars downstairs. I may cut and fit other pieces downstairs this winter, then in the Spring haul it outside to glue everything up.
Thanks for the feedback.

Pete

Title: Re: DE spars
Post by: Kiwi55 on October 20, 2014, 07:32:43 PM

Don't take this as gospel as I am just going by my interperation of the plans. The vertical spaces are 1/4 wide, the same as the rib thickness. The ribs will attach to these vertical spacers.
As mentioned they are 15" apart. The 1st rib spacer is 16 3/4 from the fuselage end because of the extra at 1 3/4, then 15" each except the last which is a little less because there is another rib and spacer 1 3/4 from the wingtip end.

Title: Re: DE spars
Post by: Bob S. on October 26, 2014, 08:45:48 PM

Not sure exactly how the DE does the 1/8" spar web, if it is 1 piece or multiple. The joints of the Legal Eagle are just butt joined centered over a 3/4" x 3/4" intercostal (the vertical "spacers" in the spar) every 3rd main rib. Where there are no joints in the spar, yes, they are 1/4" x 3/4".....
ALL rib spacings should be 15" (PLUS the 1-3/4" at the root and at the tip) OR that's they way they are on the LEU... .. giving a total wing panel length of 139" out to out. 
NOTE: the 1-3/4" is center to center of the outer two ribs each end (root & tip)... or 2" out to center.
THUS you have: 2" + (9 x 15") + 2" = 139" total wing panel length.

Title: Re: DE spars
Post by: ParQld on October 26, 2014, 09:38:13 PM

Quote from: Bob S. on October 26, 2014, 08:45:48 PM

Not sure exactly how the DE does the 1/8" spar web, if it is 1 piece or multiple. The joints of the Legal Eagle are just butt joined centered over a 3/4" x 3/4" intercostal (the vertical "spacers" in the spar) every 3rd main rib. Where there are no joints in the spar, yes, they are 1/4" x 3/4".....
ALL rib spacings should be 15" (PLUS the 1-3/4" at the root and at the tip) OR that's they way they are on the LEU... .. giving a total wing panel length of 139" out to out.
NOTE: the 1-3/4" is center to center of the outer two ribs each end (root & tip)... or 2" out to center.
THUS you have: 2" + (9 x 15") + 2" = 139" total wing panel length.

Hey Bob The DE spacing is 15" also but the total span is 168" There are 1-3/4 +10 X 15" and one at 14.5 + 1-3/4 = 168" if I am correct. The outboard Rib spacing has a question mark on the plans. Don't take it as Gospel but that's what I calculated, any other Double Eagle guys care to chime in here.

 I think the webbing works the same way ie Multiple pieces butt joined (except for the those that may scarf . the old running debate).

cheers Paul

Title: Re: DE spars
Post by: Bob S. on October 26, 2014, 09:50:36 PM

Sounds good to me.... I was SURE there was a span difference between the LE & the DE.....

I was intending to point out that the splices were on a wider intercostal (3/4" x 3/4")... I GUESS that if you were to scarf the joints, you may not even need the wider verticals........  I know I stewed on the spacing for a while when building my wing....(LEU wing shows 1-7/8" for the first two/last two (root & tip) spaces, but that is ctr to ctr). 

your dimensions total just fine!

YMMV

Title: Re: DE spars
Post by: DTeague on October 27, 2014, 06:34:24 AM

Hi folks,
Don't know if this has been covered in earlier posts..  (this is my first post on the new site..)

Anyhow...  a word of caution when you put the taper the ends of the upper spar caps on the forward spars...
Be sure to add enough material available / left at the ends / wing tips (approx. double - about 1/2")..
This allows for the front to back taper of the upper spar caps that will end up blending into the top of the leading edge ribs.. 
If you don't, you'll only have a sliver (if any) of wood left on the end of the front edges available to glue the spar webbing..  Can you guess how I found out?

I imagine this might also be true with the other Eagle front wing spars..  
     
Regards,
 Dennis Teague   

Title: Re: DE spars
Post by: Peterross on November 30, 2014, 11:55:39 AM

Thanks for the info on making sure there is enough material left after the taper and bevel. I made a rough drawing and measured, and you are right. You need to add about 7/32" to maintain the 1/4" at the tip.
I guess that leads to the question: What is the purpose of the taper on the last 46" of the spar caps? Is it for weight? Does it change the flexibility at the tips?
Leonard, can you answer why there is a taper on the ends of the spar caps?

Thanks

Title: Re: DE spars
Post by: Steve on November 30, 2014, 03:29:28 PM

Quote from: Peterross on November 30, 2014, 11:55:39 AM

Thanks for the info on making sure there is enough material left after the taper and bevel. I made a rough drawing and measured, and you are right. You need to add about 7/32" to maintain the 1/4" at the tip.
I guess that leads to the question: What is the purpose of the taper on the last 46" of the spar caps? Is it for weight? Does it change the flexibility at the tips?
Leonard, can you answer why there is a taper on the ends of the spar caps?

Thanks

Comment from Leonard follows:

Hi Steve,
The taper is for lightnes and is onthe bottom of the top spar cap and the top of the bottom spar cap. There should be plenty of room for the angle cut as the tip is 1/4" thick. Leonard
 
---- Original Message ----
From: "skiblinger@cox.net" (skiblinger@cox.net) <skiblinger@cox.net> (skiblinger@cox.net)
Sent: 11/30/2014 2:16:49 PM
To: leonard@lemilholland.com (leonard@lemilholland.com)
Subject: Topic: DE spars (From: Steve)

Dear leonard,
I want you to check out "DE spars" on Eagler's Nest. To view it, please click this link:

http://www.eaglersnest.com/forum/index.php?topic=630.0 (http://www.eaglersnest.com/forum/index.php?topic=630.0)

A comment has also been added regarding this topic:
Inquiry from a DE builder

Thanks,

Steve

Title: Re: DE spars
Post by: Peterross on November 30, 2014, 05:37:16 PM

Thanks for the feedback. It helps to understand what the thought is behind the design.
I have my table set up and am about to build the spars.
I thought I would hand plane to rough taper into the spar caps, then use a belt sander to finish it. I will be using T-88 on the spars.
This I can do in the basement, then when Spring arrives I'll be able to finish the wings in the garage.

Title: Re: DE spars
Post by: DTeague on March 30, 2015, 08:28:38 AM

Hi again folks,
In my post last October (sorry for the delay), I may not have been as clear as I should have been.. I used the word "add" in referring to the material that I believe you need to "leave available" at the wing tip ends of the front, top spar caps.
The reason I suggest leaving about 1/2" (15/32" total as reported by Peterross) is that there are two tapers (or a taper and a bevel) that intersect at each of the wing tip ends of the front, top spar caps.
This represents the order that I used cut them...
The first taper is obvious and is clearly detailed on sheet 40 as starting 46 3/4" in from the wing tip, running to the wing tip end of the spar.   It is in the vertical plane.
The second, a little less obvious, taper is also detailed.  It is shown in the detail in the top left hand corner of sheet 40.  It is in the direction of front to back of the spar and on top of the top, front spar cap in the horizontal plane.  It runs across the entire length of the wing and allows for the smooth transition from the main rib to the leading edge rib profiles.

Note:
The above describes the order that I used to cut the two tapers..   If you reverse the order of cutting the tapers, the adjustment required will probably be much more obvious..  and you would most likely leave the correct amount of material at the wing tip.
  
Regardless, if you want to maintain a minimum of 1/4" of material on the leading edge, wing tip end, of the front, top spar cap, I believe the builder will need to leave about 1/2" of material at the tip when cutting the "first" taper as I describe above.  Doing so should end up leaving at least 1/4" of material on the front edge of the spar cap and 1/2" on the back end of the spar cap at the wing tip.

I'm including a scanned copy of my sheet 40.  It includes my construction notes.  It is only my interpretation and is not intended to replace or modify the official sheet 40 as released by Leonard.  Use at you own risk..

I hope this will be of help,
 Dennis