A forum about all aspects of the construction and maintenance of the Billy Dawson inspired modified Hatz Classic biplane. Here is the place to ask your questions and get the answers from the real experts.
I spoke to the engineer next door today and he had some RV4 plans. We looked up the bell crank material. It's 063 2024-T3 aluminum. I check my Glasair and it's the same thickness. The Glasair plans don't mention the material as the bell cranks are pre made. So I think I'll use 063 2024-T3 aluminum to make the bell crank. I'm going to try and machine the parts on my CNC router.
The other thing he mentioned is that aluminum tubing can be substituted for the steel push rod tubing as long as the thickness is doubled. The RV4 has some push rod linkages made from 3/4" 035 6160-T6 that are 65" long. All of the Hatz push rods are less than 65". I'm going to make my push rods from 065 6160-T6 aluminum tubing. The weight is half that of steel even with double the wall thickness. The threaded rod end inserts are still made of 4130 steel rod, but are riveted to the aluminum tubing. Both the RV4 and the Glasair II use the same method.
Tube Inserts 0.75 6160 x 0.065.png (68.77 KiB) Viewed 2426 times
So I did put the wing together before gluing and drilling. I have two ribs (#2 and #8) that interfere with the drag/antidrag wires. I thought about moving the ribs but decided to just cut the cross piece and patch them. I also may be able to bent the compression tube strapping to get the clearance. I did that on the upper wings.
I have a slight error in my compression tube locations. I assumed the stationing is referenced to the center of the ribs. I don't think it is. The plans show measurements to the inboard side of the ribs. That puts my compression tubes out by 1/8" both on the bottom and top wings. I'm not going to sweat it.
I also built the aileron control system out of 3/4" wood doweling to see how it worked. There are some problems with the aileron system. I ended up redesigning it. I documented the changes on my blog: http://myhatz.blogspot.ca/2017/09/2017- ... -wing.html
As always I analyze things to death. I had drawn up the drag/antidrag wires once before to get the lengths. I finally figured out how to draft the drag/antidrag wire conflicts with the ribs without a 3D model. The attached schematic predicts where the conflicts will be if the wing is built exactly to plan dimensions. On the schematic if the wire crosses the black line within the area of a rib cross member, there will be a conflict. I have circled the three possible conflicts on the bottom wing. When I trial fit the wing together, I thought there were only two. And there may only be two depending on how close I am to plan dimensions with my construction.
drag-antidrag conflicts (small).png (87.36 KiB) Viewed 2362 times