Original Posted By: Matt Naiva
Gezz, I hate to say this...It depends upon what plywood you used for the gussets. If Mahogany plywood, then you are probably ok, as it is really poris stuff. But, if you used birch...you could be in for trouble.When i started using birch ply, with hemlock for capstrips, I did some distructive testing, and found that the birch would pull away from the hemlock with little trouble, and the t-88 joint failed at the glue joint almost every time. Hemlock doesnt glue as well as spruce however.The problem with birch plywood, is the smooth glassey surface. It doesn't take glue well...no tooth.After that I roughed up my gussets on a sanding wheel with a few good swipes, and the joints went from weak, to very strong.I also ended up throwing out about 7 ribs. And the truth is, I still have a few gussets (5 or 6) ...(not ribs) that are not sanded, but I think there is enough redundancy to take care of it.On the plus side, I read once about an airplane that had been glued with casin glue that had all dried out, but was still flying, held together only with the nails.ocb>From steve(at)byu.edu Fri Feb 5 17:50:50 1999>Received: from adena.byu.edu ("port 1660"@adena.byu.edu [128.187.22.180])> by EMAIL1.BYU.EDU (PMDF V5.2-31 #31181)> with ESMTP id for oilcanbob(at)hotmail.com;>Date: Fri, 05 Feb 1999 17:51:32 -0800 (PST)>From: Richard DeCosta >Subject: Help... do I have a major problem?>Sender: Maiser(at)adena.byu.edu>To: Pietenpol Discussion >Errors-to: Steve(at)byu.edu>Reply-to: Pietenpol Discussion >Message-id: >MIME-version: 1.0>X-Mailer: Mercury MTS v1.44 (NDS) (via Mercury MTS v1.44 (NDS))>Comments: Originally To: "Pietenpol Discussion" >X-Listname: >>I just got my copy of "Aircraft Building Techniques" from the EAA and>have read 3-4 chapters. I am now on rib #25, meaning I have done 24>ribs before reading the section of the book on plywood. >>I am a little concerned now, as I have not "scuffed" or sanded my>plywood before gluing to the ribs as the book suggests. I did the>water test as described in the book, whereby one pice of scap plywood>is scuffed and the other is not, then water is placed on both. As the>book predicted the water soaked readily into the scuffed piece but>kindof beaded on the un-scuffed one, meaning glue would not soak in as>well either.>>Is this a major factor in the strength of my ribs? Should I scap the>25 ribs I have built? or will they be strong enough without this>scuffing?>>Concerned,>>Richard>>>==>http://www.wrld.com/w3builder>Now you can buy my CD at MP3.com:>http://db.mp3.com/Visitor/order.php3?cd ... __________