fuselage tube size

[mr bill]

Anyone know the outside diameter of the steel carry thru tube in the lower fuselage of a mk 7 that supports the wing strut attach fittings and the outside diameter of the front spar carry thru tube in the upper fuselage? I want to compare the sizes to my mk 4.

[Dorsal]

Bump.
I do not know this off the top of my head but someone who is building should be able to measure it pretty easily, any takers?
As I recall it is not very large (same as much of the rest of the frame tubing).

[szicree]

On my Super Sport it's 3/4" and 1-3/8".

[mr bill]

Which one is 3/4"?

[Dorsal]

Bottom one

[mr bill]

That is helpful, thank you. It is the same size as my model 4, but your front spar carry thru is larger. I have read in older threads that people had added steel straps to the lift strut tubes in the fuselage for added strength, but no mention of the front spar carry thru tube. I am not as concerned about weight as strength, so I will give this some thought. My wings and tail feathers are covered and am about to start the fuselage.

[HighWing]

Don't forget the wall thickness of the tubing. If you are planning on replacing things to get higher max wts., you will need to know wall thickness. Keep in mind also that the lower tube is in tension while the upper tubes are in compression. The larger diameter on top will help prevent buckling at the top where a simple cable could withstand the tension forces at the bottom - other structural considerations aside. This is why the early factory retrofit to increase the IV 1050 to 1200 lbs was two holes drilled above the lift strut pivots and a rod inserted (inside the the lower carry through) and either welded in place or tapped on both ends for washers and nuts.
Lowell