Tension tube between center section and upper wing panel

A forum about all aspects of the construction and maintenance of the Mark and Sandra Marino inspired modified Hatz Bantam biplane. Here is the place to ask your questions and get the answers from real experts.

Tension tube between center section and upper wing panel

Postby stearmoth » Tue May 18, 2010 2:19 am

Dear Marc,
As you know, we got the drawings from you for your genious aluminum compression struts in the wings (we still have to pay for....). That's a clever thing, we think the weight saving against the steel compression struts of the Classic is worth the change to your system! Now, we have a question:
In teh Classic plans there is a compression strut within the center section and one within the wing panel (each close to the root rib), however you installed a supplemental tension strut between the senter section and the wing panel. What is the reason for? Is it because your compression strut design cannot handle tension loads (the rivets connecting the aluminum tube joining the strut socket would not be strong enough?), or what is the reason? Is it, that the Classic steel compression strut design can also take tension loads? In the Classic, there is only one tension strut per wing panel at the interplane struts position. We think this is because the rigging wires impose some tension.
Your comment would most be appreciated.
Best regards
Hans and Sam, Switzerland
P.S. we still are awaiting details for paying those drawings...
Posts: 227
Joined: Mon Apr 26, 2010 12:47 pm

Re: Tension tube between center section and upper wing panel

Postby Mark Marino » Thu Jun 03, 2010 9:04 am

It is my opinion that the compression tubes are just that...a compression
tube. In the center section of the CB-1 the plywood bottom that holds the
gas tank I believe also acts as a tension component. Since the Bantam has
no plywood on the center section I added the tension tube. This tube
completes a triangle across the top of the cabane struts making it very
strong. I also believe it's better to have the tension tube located as
close to the strut attach point as possible rather than up in the wing. The
plywood on the CB-1 is quite close to the cabanes being located right on the
bottom of the spars and attached to both the spars and butt ribs. On the
interplane struts the tension tubes complete the triangle in the same manner
on both the top and bottom wings. The CB-1 has two tubes in this location,
one for tension and the other for compression.

Mark Marino
Mark Marino
Posts: 4
Joined: Thu Jun 03, 2010 9:00 am

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