Hatzers,
Another milestone in the books - the HS support structure is welded on.
IMG_20200530_160044 (1).jpg
What I learned:
1. The front and back horizontal 5/8" tube sections that the two HS halves slip over do not have a specific length in the plans. I used 20" and 8" and that seemed good enough (might trim off a bit later).
2. Even though the plans are a bit vague or even specify 0.035", I used 0.049" for the thickness of all support tubes (both horizontals and the two support tubes elevating them above the longerons) both fore and aft, as this is the thickness of the longerons as well as the HS structure in those locations.
3. I started with the front support, and a wood block between the horizontal tube and the fuselage cross member underneath it (station 151) for the right spacing. Then with the HS slipped over the 20" horizontal tube, I measured from each HS tip to the front of the fuselage to make sure I had that dimension the same. It is challenging to get the two HS halves symmetrically mounted. Made sure the two tips are 114" horizontally from each other and centered on the center-line of the fuselage. I used an 8' square and rigid steel tube (the kind they use for street signs) from Home Depot - that is a very good straight edge to clamp to.
4. Once I had the front structure tack welded, I supported the back of the HS with the 8" section of tube at 0.25" lower than the front (which would give a 0.65° of incidence).
Double check the measurements from the tips to the front of the fuselage.
Lots of jigging required, but I am happy with the result.