Dumb Question

[914pete]

I hope you all are patient for I fear I'm going to have a lot of dumb questions on this journey.  I received my 4130 tubing this morning and had a little time to lay out the lower longerons for LEXL-F-11.  Question, I've seen online where they are BOTH coped and joined on the center line.  Is it acceptable to just cope one and not the other as in my pic?  Both longerons are in line on the rest of the table, it seems there would be more meat at the tail post and as mine fell into place the width is 3/4" which would be perfect for the tail post.  (be gentle, first time builder here)

[Vince Carucci]

My guess is the only down side to your approach is a weight penalty, and that would just about be negligible. For example, 4130 steel at a thickness of .035", a 1 inch square would weigh approximately: .01 lbs., .16 oz., 4.5 grams. 

I would be remiss if I didn't repeat the conventional wisdom regarding changes, "add nothing but lightness". But then Leonard left us a whopping 10 lbs. Good luck.

V.

[Tom XL-7]

914 PETE
I have to ask 914 means Porche-vw based and all. I wish I had one
Also rotax water cooled reduction 4 banger
 I would assume the aircraft application but one never knows .
you could be some old curmudgeon.
If you are look out for steel roofing salesmen.
 And if you have a clue as to what thet means your from the old Yahoo Site
 I have two observations on your post. 
 # 1   I plan to do the same  as in cope one let the other tube be a tube.
I like the strength. However if you fear the weight and we all should at every turn.
Cut a "V" out of the tube. Leave a good quarter everywhere.
#2 You have your tubes laying flat. That is common practice on the LE,
however,  the XL drawings to my understanding  are station distances.  As in plumbed down to the table.
Meaning your tail post should be a measurement above the table- being slightly longer.
 The normal practice of an LE is to tack up the rear : heat both tubes  and pull the whole assy. into place. I like that.
See mike's u-tube
It seems to me and I  could be big time incorrect that I bend longeron one and then longeron two to a station above the build table.
Much more difficult but as I work mostly alone one at a time works for me. 
The only real issue is a matter of distance.
I could be out to lunch but be sure.
Tom XL-7

[Tom XL-7]

by the way -no such thing as a stupid question- only stupid answers
old saying but absolutely true

[JLee]

I like that idea I just wouldn't do it on entire fuselage.    It would definitely add strength to a  place that could use the extra help.

[914pete]

914 PETE
I have to ask 914 means Porche-vw based and all. I wish I had one
Also rotax water cooled reduction 4 banger
 I would assume the aircraft application but one never knows .
you could be some old curmudgeon.
If you are look out for steel roofing salesmen.
 And if you have a clue as to what thet means your from the old Yahoo Site
I have two observations on your post.
 # 1   I plan to do the same  as in cope one let the other tube be a tube.
I like the strength. However if you fear the weight and we all should at every turn.
Cut a "V" out of the tube. Leave a good quarter everywhere.
#2 You have your tubes laying flat. That is common practice on the LE,
however,  the XL drawings to my understanding  are station distances.  As in plumbed down to the table.
Meaning your tail post should be a measurement above the table- being slightly longer.
 The normal practice of an LE is to tack up the rear : heat both tubes  and pull the whole assy. into place. I like that.
See mike's u-tube
It seems to me and I  could be big time incorrect that I bend longeron one and then longeron two to a station above the build table.
Much more difficult but as I work mostly alone one at a time works for me.
The only real issue is a matter of distance.
I could be out to lunch but be sure.
Tom XL-7

Hi Tom, yes, my other on going project is a 1974 Porsche 914.  My plan for it is far from original but rather a street legal track car.  I have a small block chevy 350 mated to the 914 transaxle on an engine start stand I made in my warehouse.  (I got the engine and trans adapter for 1/2 what the cost of rebuilding the boring flat four would have cost)  I like to fire it up once in a while in the warehouse to keep it running and piss off the neighbors (open shorty headers)

So, back to XL F-11.  Now you've got me thinking.  Reviewing the written "fuselage" section of the plans Leonard states "tack up the bottom to the no. 3 station. That is where your first bend will be."  So I did lay out the longerons flat on the table and was planning on tacking in the cross tubes and THEN bending at station no. 3.  But your right, that will make things a bit shorter.  I haven't tacked anything yet.  Am I doing this wrong??

Also, I decided to grind the other longeron at the tail post, it was bugging me.

[914pete]

I took some measurements.  If tacked up flat on the table to station #3 and bent up 16 3/8" off the table at the tail this would move the tail post forward 1 1/8".  (essentially shortening the fuselage aft of station #3 by 1 1/8").  Hmmm, so I'm thinking I can tack the tubing flat on the table to the cross tube prior to station #3, brace the longerons with a piece of angle steel 1 1/8" forward of where I have station #3 drawn on the table and bend there.  Then move it all back?  Each cross tube should plumb down to the original center lines (tubes) I have drawn on the table per plans.  Is that right?

[Tom XL-7]

Thanks for the pictures. I really like the tubes terminating in one circle. Looks great and appears to fit up perfectly.
Didn't mean to open up a can of worms for you. Just wanted to mention what I saw in the plans. And I would read the plans as station locations.
It certainly would be easier if they were marks on the longerons. 
 I am not surprised that the difference is so small. I had a bit of disbelief when I did my takeoff. Allowing both for the upward bend and the movement to centerline I was not seeing  the growth in length I expected. Well, you can redo the math a second and a third time and in the end, you have to decide do I believe in this equation or not. As many as have been built I am sure we have both flying as well a few outliers. The truth is they are probably all outliers in one way or another. 
Unless we are popping parts off the same jig there will be variances.
 One more thing to ponder. Should you just put the station 3 cross tube in(your new improved location). Clamp away from the heat with something simple like plumbing or conduit clamps? I try to avoid heavy heat sinks unless I need them.
What happens to your nice fit up when you move forward an inch and eighth and reset to 24 inches at station 3?
Don't mean to be a trouble maker.
Enjoy your build and it would be nice if someone else would chime in.
Especially if I am off base.
Tom XL-7

[914pete]

Hi Tom, I guess I'm hung up on tacking the bottom pieces in on the table prior to bending the longerons thinking it will be easier.  (not so sure) But I did move back the longerons  1 1/8" from where I drew everything out on the table then I positioned a piece of 4130 from the center cross tube at station #3 to the end where the longerons meet and I marked off on this tube the centers of the cross tubes as they were drawn on the table.  Then I raised the tube up 16 3/8"  off the table at the tail and secured to a jig.  I plumbed down from those marks to the table and as expected it does change the placement for the cross tubes I originally drew out on the table.  So, I left that tube in place and plumbed down to the table to the centers of the tubes drawn on the table and marked it on the raised tube.  Put the tube back down on the table and from the tail the cross tube placement was off by 7/8" for the first cross tube (closest to the tail post).  See pic.  As you move forward to station #3 the originally drawn cross tubes are not as far off.  The third cross tube is within 1/8" and the 4th dead on.  I'll re-position the cross tubes on the table.  This will work but there has to be an easier way LOL.

[joecnc2006]

I did the same thing, and when raised the length was about 1.25" short, I asked Lenard if it would make a difference he said no, it is common. so many people have built theirs that way.

[Tom XL-7]

I would guess more made short than long.   ( Most?)
There is something inherently difficult in a 3 tube fuselage. You end up building in 3D. No matter how you deal with the bottom longerons; in the end, you will hang or support the top longeron and build in space.
It is the price to pay for the reduction in weight, not just the weight of another longeron but a whole set of cross tubes as well.
On the other hand, in a box fuselage, one side can be completely tacked up and usually the second side on the same table and locations.
stand them up and fill in the top and bottom. There are also structures that do the top, then bottom, suspend the top and fill in the sides.
An advantage if you have a really busy bottom and or top of the fuselage.
  I will just bite the 3D bullet and bend the tubes up and fill in the ladder from center line marks.
This one just doesn't lend itself to much flat table work. Look at the wing tube, the cockpit and out to the firewall. Keeping it all square and true will be a learning experience.
Tom XL-7

[Tom XL-7]

Find "19 steps to a legal eagle XL frame build".
It is by Scott (in Iowa/ Iron Design)
I found it on the old site in files. He has laid out a build sequence which should be reviewed.
Whether you follow his prescription or follow your own it is important to think the sequence through.
I will incorporate the concept of station 2 and 1 being built up and square. That really give a nice foundation for the rest of the build.
After seeing the lower part of station 2 built up "Square", I can't see a better way.
Tom XL-7

[914pete]

I did the same thing, and when raised the length was about 1.25" short, I asked Lenard if it would make a difference he said no, it is common. so many people have built theirs that way.

Hi Joe I was kinda thinking the same thing.

[JTMaze]

Saw “dumb question” and figured this would be the best place to start. I’m new to the forum, heck new to flying period……bucket list thing! So be prepared for some really dumb questions.
I have plans for the XL and DE but I plan on building the XL. My first dumb question is, where in the world is everyone getting their bottom fuselage measurements to lay out the template on the table? The DXL has a nice drawing (page 2) that gives some good measurements but I can’t find a similar layout for the XL. Do I use a combination of page 6 and 7 to lay it out?

[Tom XL-7]

If you have decided you must build on the table and want to convert the page 6 numbers to their flat table values here is one method that requires no math skill beyond reading a ruler. Put paper like from a roll 24' wide on your table.
Make a line as per page 6 from tailpost to station 3 with all distances indicated. Go to the tailpost end and with a square mark the raised height.
A new line is generated between the raised point and station three.  You should have a long skinny triangle.
Now using the square transfer all your dimensions to the raised line.
Those are your new converted centerline measurements. who cares what the inches and fractions are. Just use them on the centerline.
Even a dummy can do it.
If your not a dummy then do it all with equations or a computer and lay it all out.
Welcome and enjoy.

There are no dumb questions,
Tom XL-7