nauticom

Question for you experts out there.
I am building a Giant Scale(?) Ziroli Corsair. I have read where folks use a "shear web" as a means of strengthening the the outer wing panels. I cannot see an example of this anywhere yet. Please explain what this is and a how to.
Thanks,
Bob Masterson
nauticom

Rodney

A shear web is simply a webbing between the upper and lower spars. It is often just 1/16 or 1/8 inch sheet wood cut to fit between the two spars. Most directions say to make the grain vertical on the web material but: a little delving into the stress books show that this force is always at a 45 degree angle to the wing span, one direction under positive G's and 180 degrees different under negative G's. In reality, it makes no difference which way you run the grain in so far as strength goes but it is usually easier to cut the material with the grain vertical. Shear webs do a great deal of good insofar as strengthening the bending forces on the wing.

scratchonly

They are pieces of vertical grain balsa or ply mounted between the spars and between the ribs. They can also be glued to the face of the spars but in both cases they must be fitted tight to the ribs and dpars. This is to add an I beam effect to the spars. They are more important from the dihedral brace or wing joiner out to just past the beginning of the ailerons than on the outer portion. You could use lighter wood out there. I would Think for large scale at least 1/8 firm balsa VERTICAL GRAIN or 1/16 ply. Use glue on all 4 sides.

Good luck

CoosBayLumber

My Feedback: (1)

Back when sheets of balsa wee cut pretty accurately, the standard 4 inch wide or three inch wide sheet was then set tight between the internal faces of the ribs. You then simply glued in bottom edge, let set, sliced off the sheet at the upper surface with razor blade, and glued that in place too. Then go on to next one. If you were fast, a whole wing half could be completed in matter of minutes.

This made for rib spacing exceeding a standard sheet width by one rib.

Beware too, that if there is a warp already in the wing, it will become even harder into place after adding the shear webbing. Get then out first before gluing.



Wm.

nauticom

Thanks to all for your responses.
I will definetly use shear webbing.
I like using carbon fiber tape ( Aerospace Composite Products Uni-Web) material. It is about .004 inch thick and I usually make a sandwich and epoxy the balsa to it on each side. I wonder; sense the balsa grain is vertical, should the carbon fiber (it's unidirectional) also be vertical?
Thanks,
Bob Masterson

cmoore806

My Feedback: (82)

I wouldnt get too carried away with the CF tape. Ziroli knows what he is doing with the designing and the sheer webs should be more than adequate. Once I replaced heavy balsa and basswood spars with very lightweight balsa and then put a strip of 1/4" wide CF tape on the top and bottom of both the top spar and the bottom spar...but only because I made the switch to the very lightweight wood.



Chris


PS--I dont want to insult you but are you ready for a corsair if you dont know what a sheer web is?

nauticom

cmoore806:
Sorry for my lack of knowledge.
I do have a fair amount of experience building but had not known the proper name for what I had done to reinforce critical areas of my planes. I do have 6 kit built planes, plus the ZCorsair under construction. I have reinforced main spars etc with CF in the past and would have inserted the balsa in the wing to make an I beam effect. Just did not know the correct term when I say it in a post on another site. My Zcorsair build project is on our club web site: www.thebams.org Again, thanks for the inputs. I very much like the Ziroli plans, and am not afraid to ask questions when I need. Thanks.
Bob Masterson

cmoore806

My Feedback: (82)

Just checking =) I would hate to have someone who isnt ready for a corsair to go through the work of building it only to fail on the first flight (or before). Happy flying!