I-Beam Construction

I-beam wings are very flexible compared to a D-tube wing especially before the wing is covered. Is there any light weight way of impoving the structural rigity if I-beam wings?

Go down the page to the topic Wings and look at the picture of the warren truss I-Beam wing.People have been building them this way since the 50's and it will not twist.
Ed

>I-beam wings are very flexible compared to a D-tube wing
>especially before the wing is covered. Is there any light
>weight way of impoving the structural rigity if I-beam
>wings?

Get the videotape by Bob Hunt at Robinsview that has Billy Werwage building an I-beam and reinforcing it with CF tape.

I havn't noticed excess flexability. I use a D-tube trailing edge and, usually, a laminated leading edge. I use a box spar rather than an I-spar. I did make an I-beam with carbon fiber top and bottom for a plane I have never finished. It was much less rigid than a Box spar made out of about the same amount of material. I still use silkspan or silk rather than monocoat. I figure the covering carries a lot of the load so I triple cover the first bay and double cover the next couple of bays. One reason is to strenthen the covering where helpers tend to hold the plane and also to strengthen the covering where I think the stresses are highest.

I don't doubt that D-tube is the best, but I enjoy building I-bean type wings. One thing I have gone to is using moderately hard bals for the stripped ribs. With contest balsa I spend more time repairing ribs already installed than putting in new ribs.

You have a great idea on the triple and double covering the first few bays. I did that once, strong wing, fuselage shattered! As to any plastic films, an absolute no no on I beamers. The covering is where the stiffness in the wing comes from and plastic film tend to stretch in the sunlight. Thus a wiggly wing.

Hi Eggy,

Well, I know Eddy R. has great ideas on his I-Beam construction techniques. I saw his Juno with the Warren truss set up, and it was pretty solid.

But, as to the plain jane I-Beam, the best bet is to face the inside of the spar caps and the TE w/.007 carbon fiber strips. This negates the need for a rear support spar on the 35 size planes. You can then just glue 3/32 X 3/16 uprights about 1/2 way back between the spar and TE to keep the ribs from sagging under tension of the covering.
I have built 4 I-Beam planes this year, and all have held up well with plenty of strength when finished.
Bill <><

Here's an idea I've considered, but have not yet tried...

Internal rigging of the structure with Kevlar thread.

Bi-planes were often externally rigged, by having wires in tension diagonally bracing the wooden compression struts.

You can do the same inside a naked I-beam structure by threading the Kevlar (or Dacron or Nylon) with a sewing needle, through the ribs from spar-bottom to TE to spar-top and so-on all the way down the wing at 45-60 degrees and then all the way back up to get the other diagonals.
When its all threaded you hang the wing vertically and tension all the threads by hanging say an ounce off each end and the set the thread at each peircing with a drop of cyano.

I'm going to try it later in the year, so I'll post details of how it goes then.

A.