Adjusting Lauzon Center Section Cabanes

[Ebby]

In tweaking the rigging on s/n 37 to reduce a heavy left wing issue, measured at the outermost full wing rib, I discovered the stagger on the left side is 25" and the right side it is 22", To me this is no longer tweaking and a major concern. I have the Lauzon cabanes built to plans and would like confirmation/information on how to correct this stagger issue. This is my story with the top wing panels installed and I didn't want everything to come crashing down.

If unfamiliar, here is a description of the Lauzon Cabanes. There is a fixed length center 'leg' attached to the forward CS spar on top and a weldment on the fuselage at the bottom. Attached to the forward side of the center leg is an adjustable leg with a clevis end at the upper end and a through bolt at the bottom fixing it to a weldment on the fuselage. On the aft side of the center leg is another adjustable leg with the upper end attached to the rear CS spar via a 'universal' hinge. A clevis end on the bottom end attached to the lower end of the center leg completes the assembly. I believe the clevis ends are mainly for rigging the center section incidence to 0 degrees fore and aft and 0 degrees laterally. The roll wires are to center the center section over the longitudinal axis and keep it there.

I built the cabanes at the same time and evidenced by the left wing, a 25" stagger is attainable. I am struggling with how to move the upper wing right side 3" forward to match the left upper wing. All the flying wires have been loosened, all but the forward landing wire has been loosened and the roll wires are still holding the center section centered. I did loosen the roll wires hoping tightening other items would move the right wing. I've tightened and loosened, pull and tugged and can't get any movement near what is needed. So after spending the better part of the day unsuccessful I left. That night I kept mentally analyzing what each component actually did with regard to moving things and could not theorize anything else I could do.

Starting a sleepless night I thought of something I could try. Your input is welcomed. Loosen the bolts under the cowling attaching the cabanes to the fuselage and the bolts at the clevis ends and hinge ends of the CS cabanes and all the interplane strut bolts on the right wing and then use the right wing forward landing wire to move the upper right wing forward. Essentially to untwist the upper wing. By loosen I mean just enough to allow movement. I may not get the full three inches, it may cause the left wing to move back but if I can get them equal I would call that a success.

Regards to you all. I know it's a bad time to post as many will be at Airventure. But it was therapeutic writing this post.

John 'Ebby' Ebensperger

[mmarien]

The stagger on the wings should be 23". It's not easy to see on the plans, but if you calculate the stationing of the CS upper spar from Drawing 15 - Cabanes, you will get Sta 22.00 for the CS main spar. This is the same as the stationing for the main spar of the upper wings. The stationing of the lower wing main spar is given as 45.00 from the location of the spar attachment - Drawing 11 - Fuselage. The difference is 23". The drawing for the Interplane Struts is just wrong in so many ways that you can't get a lot of information from it. I have attached a copy of my AS-Built drawing for the Interplane Struts. It shows the stationing for the main spar on the upper and lower wings.

A couple of things you might want to check. First I would measure the diagonals from some point on the lower wing to the vertical post the rudder is attached to. This should be equal for both wings. If not, some of the stagger error is because the the lower wings are not square to the frame. You can also check to see if the upper wings are square to the frame. Plumb down from some place on the upper wings and measure from that point to the vertical post the rudder is attached to. These also should be equal.

If the lower wings are not square to the frame there is probably little that can be done. You would have to modify one of the spar attachment on the fuselage to square up the wing. Not an easy job. If the upper wings are the problem, you may try and adjust the CS so that the wings are square to the frame or at least parallel to the lower wings. However, I don't think the cabanes were made to adjust the upper wings that way.

So, I guess I'm not being a lot of help here other than suggesting a method to identify where the problem might be.

[Ebby]

You have given me some alternatives I hadn’t thought of. I have a set of CB-1 plans and there is a direct statement that the stagger is 23” not 25”. I’m measuring stagger at the outermost full wing rib and to reduce the 24.5” stager to 23” might not require that large a change in CS rigging. Im sure there is a way to calculate how much movement is required. I appreciate your analysis and will let you know how things work out.

[ssearle]

Helo Ebby
Saw your plane in sportaviation and it is beautiful. I'll tell you about H0162. Oringinaly with a rotec and 2 forced landings due to engine failures I re-engined to 0-320 lycoming and shortened gear to plans. Due to flipping over in a bean field I had to build a new right cabane strut. Since then I have been struggling with a slightly heavy left wing. I've rerigged right upped wing to o incidence and left left to 2 but made it slightly worse. I've try'ed to tuned ailerons to no avail.You got me thinking about the center section. Mine is close to centered but I think I'ts slightly to right. Also I gained 70lb on weight and balance on the right side. Once again thank you for you"re input.I'm thinking about shifting the top wing gradually to the left. Definatly don"t want to add trim tabs.
Stee H0162

[Ebby]

Thanks for sharing your story. I am at the edge of frustration with the Luazon cabanes. I have the Hatz Classic and am not sure those were meant for the Classic. For some reason, (I know it's me) I cannot find page 15 of my Makelan Plans sheets for data. So I have no data regarding the angles the Cabanes make to provide the 23" of stagger. I got that number off my CB-1 plans.

At this point it is the stagger that I am frustrated with. The right wing measures 22 1/2" and the right wing 24 1/2". To me that means the top wing is twisted forward on the right and back on the left if stagger is 23". As the wings are attached to the center section the center section most likely is also twisted (yawed about the vertical axis).

The data I do have:

Top wings 0 incidence, 0 dihedral
Bottom wings: 0 incidence, near 2.5 dihedral
Center Section: 0 incidence, level laterally, leading edge parallel with the firewall frame.
Center Section: 27" above the top longerons.

I am in the process of looking for my page 15 and getting a reprint from the source (Makelan or their printer). If I cannot get the Lauzon Cabanes to rig correctly I will fabricate according to plans.