Hatz Biplane Association

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.

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

Nice work Murray

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.

Nice!

Thanks Rick. I like the suggestion to put it all together before gluing and drilling. I think I'll do that.

I did come up with a redesigned aileron idler. A few things. It has no welding. Two pieces are riveted to a bell crank bearing that can be purchased. The bearing should have less friction then the bushing. It thinner so compression tube #2 can stay at 1.75" from the bottom of the spar. The brace can be put next to the idler under the compression tube to lend support closer to the pivot point. The bolt holding the idler on can be torqued with a nylon lock nut so the idler is more secure and should have less play.

What I ended up doing is to place all the parts in position, without committing the drilling of the compression strut tube mount bolts.

Once I liked the position of the compression tube, with the bell cranks installed ( bell cranks built per plans) I drilled the holes for the compression tubes. I didn't pay much attention to the lengths of the bell crank bushings on the plans because they are just wrong. Only the diameter was right if I remember. I just made it all to fit.

I also remember for the bell crank mount bushing located on the compression tube, I made it shorter than the plans for maximum clearance allowance. I left just enough material on the comp tube bushing, for it to be a bushing.

I had a couple ribs interfere with drag/antidrug wires on the bottom wing, but not the upper wing. It was not because of the aileron linkage, but because I didn't pay enough attention to rib location prior to gluing them in position. Some of them would be better off not being exactly at 12 inch center to center intervals. I think I saw "approx." on the plans...... later someplace If I were to do it over again, I would leave all the ribs free to move until ALL of the goodies inside were located and clearanced as needed.

Rick

I'm thinking about starting the bottom wings and reviewed this post again. From the description of the bell crank idler on drawing 05 the distance from the center of the compression tube to the bottom of the idler is 1.875". Add the bushing and bolt head and it's about 2.125". If the compression tube is at 1.75 plus the 1/4" capstrip, there is only 2.0" clearance from the center of the compression tube to the fabric.

The plans don't have a dimension for this compression tube but the solution mentioned here is to put the compression tube at 2.0" from the bottom of the spar. The other would be to redesign the bell crank. I was thinking of using a bell crank bearing. The thickness is 0.625 which is half the thickness of the plan design. That would fit with the compression tube at 1.75"

So the questions is, does the 2.0" location of the compression tube cause the drag/antidrag wire to interfere with the cross pieces in the ribs or is it because of the different stationing for the compression tubes that causes the problem? The drag/antidrag wires in my top wings are close but there is no conflict with the ribs.

Great! I'm looking forward to the event!

HC85 wrote: I am headed to Brodhead this weekend, and hope that it is not rained out, and that there are classic builders in attendance! Lots of questions to be discussed!

Thx, Rick

I'll be there.