fitting tubing to top longeron

[misterbill1964]

how do you fit two 1/2 " tubes to a 5/8 tube? I'm thinking that you miter the ends to make them both come out as a 5/8 round tube when added together then cope to fit  top longeron . is this the correct way?

[Dan_]

I'm not sure I understand the question, but in general make sure the centerlines of the 2 smaller tubes intersect the centerline of the larger tube. 


The angle the smaller tubes "hit" the larger tube will decide if the smaller tubes have to be coped to each other as well as being coped to the larger tube. 


Below they are coped to each other where they touch each other in the "V" or "crotch" of the joint as well as the third tube.

[misterbill1964]

I an talking about where the tubes meet at the top of the tail triangle( circled in red in drawing)  with 1/2 ". I'm looking at 1 inch (2 half inch tubes ) trying to meet with 5/8 and don't see how to mate them without removing 3/8" ( ground flat on the insides ) from the center v, then they will meet on the center line of the 5/8.
 I might be  over thinking this as its my first plane I don't know.

[Dan_]

Yes sir you are correct in your approach.  The pic in my earlier post actually shows the tubes coped where you are talking about. 


Be sure to put a center line on any tube that will be coped on both ends.  This way you won't get the notch on the second end rotated with respect to the notch you have made on the first end and cause a gap you will have to fill.

Just lay 2 tubes down on the table hold them touching each other and run a sharpie marker down the crack.  The tubes don't even have to be the same diameter...

Enjoy your welding and fabrication...

[Tom XL-7]

I always viewed clusters as a one at a time thing. So in this case one tube would be simply fish mouthed to the top and lower 5/8 tubes. I would place one of my tacks where it will be covered by the next tube. That second tube will almost always need to be cut to fit the 5/8 and the previously tacked 1/2"
Make any sense?

[Dan_]

Here is some reading on it from EAA (part-8)


They don't mention the center line.  They advocate lining up a thumb on the first notch.  Seems like the line would help with lining up a thumb...







From the begining: (part-1)

[scottiniowa]

I always viewed clusters as a one at a time thing. So in this case one tube would be simply fish mouthed to the top and lower 5/8 tubes. I would place one of my tacks where it will be covered by the next tube. That second tube will almost always need to be cut to fit the 5/8 and the previously tacked 1/2"
Make any sense?

I agree with Tom, for two reasons,

1) the strength is the same or better done the way he mentioned
2) It just is simpler to install the first verticule tube with welds that won't hinder the second one. And then only the second one has somewhat more complex coping, instead of both.

And being new to this frame building, perhaps you haven't read or been told..but very important is all measurements are always to center line of the tube. (not matter the size of the tube) There are plenty that have spent time trying to calculate measurements to outside diameters or the like

Best of success.
Scott

[Theodore]

I'm not sure I understand the question, but in general make sure the centerlines of the 2 smaller tubes intersect the centerline of the larger tube. 


The angle the smaller tubes "hit" the larger tube will decide if the smaller tubes have to be coped to each other as well as being coped to the larger tube. 


Below they are coped to each other where they touch each other in the "V" or "crotch" of the joint as well as the third tube.

I get it, the center line measure, and maybe over thinking this but never hurts to ask right?
Fitting the tubing into a closed rectangle already tack welded, BOTH ENDS FISH MOUTHed, isnt the tube longer than the net opening?
The piece your adding one end contact/slips right in, the other end is blocked by the radius of the tube that is there already.
I not an engineer, just mechanic, welder and i sleep at Holiday Inn most everynight...
Thanks
Theo
Scott? have you welded this fuselage? I sure love your CAD work just wondering if you've ever built one? Peace.

[scottiniowa]

I get it, the center line measure, and maybe over thinking this but never hurts to ask right?
Fitting the tubing into a closed rectangle already tack welded, BOTH ENDS FISH MOUTHed, isnt the tube longer than the net opening?
The piece your adding one end contact/slips right in, the other end is blocked by the radius of the tube that is there already.
I not an engineer, just mechanic, welder and i sleep at Holiday Inn most everynight...
Thanks
Theo
Scott? have you welded this fuselage? I sure love your CAD work just wondering if you've ever built one? Peace.

Yes, I have welded this type or size, and many larger frames (super cub size, the process is the same. Race car frames too but that is a completely different kettle of fish and I might add not nearly as fun.
I just don't know about the "rectangle way" of  thinking.  I personally have never thought of boxes or rectangles in any of this. Not saying that is wrong, just something I have not done.
But there are simple things to note

• If your going to support a load, you would support directly under it, not off to the side.
• Almost every  frame design, is designed with the loads directly in line with the way the tubes are laid out. i.e. a compression tube would be where the compression is the highest, not off to the side.
• Almost every cluster is far stronger than the surrounding tubes just from the shear nature of the size of the cluster.. Think of one man trying to hold a sign in 50 mph winds vs 3-4 kids, half his size...I will bet on the kids every time, if they are told how to do it.
• There would never be a partially welded cluster.
• Almost everything in life can get over complicated, if you help it get that way. YOU DON'T HAVE TO

Hope this helps
Scott

[Tom XL-7]

Scott, I hate to speak for others but I think I know what is being asked. Something I think you may have spoken of in the past. So lets imagine working on the boom. Starting at the tail and working forward you try your best to tack in an order that keeps the forward end free even if you have to pre fit a diagonal before you do a ladder piece. Sooner or later you may run into something fixed where your double ended piece is longer than the opening. Say I am doing the floor between station 2 and station 3 and I tacked the cross members 2 and 3 without the diagonal. The diagonal no longer goes in without cutting one of those "fish lips" off. Shouldn't happen often but it may from time to time. Maybe in a busier cluster

[scottiniowa]

Scott, I hate to speak for others but I think I know what is being asked. Something I think you may have spoken of in the past. So lets imagine working on the boom. Starting at the tail and working forward you try your best to tack in an order that keeps the forward end free even if you have to pre fit a diagonal before you do a ladder piece. Sooner or later you may run into something fixed where your double ended piece is longer than the opening. Say I am doing the floor between station 2 and station 3 and I tacked the cross members 2 and 3 without the diagonal. The diagonal no longer goes in without cutting one of those "fish lips" off. Shouldn't happen often but it may from time to time. Maybe in a busier cluster

I see now,  So in that case, I make both, not all one (the majors) then come back and make the minors (diagonals)  I make both, fit both and keep working forward or rearward. it actually helps a lot with the fitting of the diagonals.  AS long as the center line marks are observed and noted, this should work well.  Keep in mind, once a major is made, you should not have to change that again, to get the minors to work into place. Nothing is tacked in the cluster until your happy with the fits.

This is not say, that the above hasn't happened to the best of tube fitters.. I won't tell.