Don, I will have to agree with you on this spar. I was thinking about it cautiously after I read it and my gut feeling is that this would be a bad move. Larry Flesners mention of cloth between layers struck a chord with me in that if you had an area like the bowed wing tip having to be clamped tightly that a strand of S glass roving inbetween the layers might hold them apart just enough to retain enough T88/or wood glue to do a nice job. I do mean a single strand of roving in the center for example, like the engine cases silk thread. One idea that has come to me while thinking about tight clampings of wood is ? Why do Prop makers tighten their layers of wood together so tightly when making a prop if it is a bad idea ? Have you ever been in a prop shop. There used to be one near me here in Caddo Mills Tx and they used house jacks to tighten the wood together and left it that way until the resin/glue cured. I have no idea what glue they used but what takes more of a beating than a propeller taking pulses from the engine and air it is moving through, besides trying to sling itself apart. Just wondering ? Maybe their glue is really thick resin ? and will not all squeeze out. Larry H.
Don Chisholm <chizmsupholst...@rogers.com> wrote: I'm not going to profess at being an absolute expert on the subject here but I'll express an apprehension here about using a layer of fibereglass cloth in a glue joint. It has been my experience with a cloth and resin layup that it is strong in tension and has some compressive strength but has no peel strength. If you do a lamination to just about any surface, you can peel the layup off easily, the resin matrix will not bond it down. Try it and you'll see what I mean and to use it in a glue joint where there will be torsional loads is something I'd want to be sure of Barry Kruyssen wrote: Where I have broken the tip off my wing in my recent force landing, about 8 inches of spar was damaged. I plan on scarfing the top and bottom spar timbers and the 3/32 ply with a layer of 2oz cloth between them using Araldite epoxy specially for timber (my brother and I have been using it for 30 years on boats without a failure, we have made test pieces this way and only the wood ever brakes, never the joint) Here is an extract from http://www.casa.gov.au/airworth/AWB/02/011.pdf#search=%22araldite%20timber%2 2 on Araldite. The following adhesives are commonly used for aircraft wood gluing: a) Resorcinol Formaldehyde Synthetic Resin Glue b) Urea Formaldehyde Synthetic Resin Glue, and c) Epoxy resin Araldite AW 134 and Hardener HY 994. Regards Barry Kruyssen Cairns, Australia k...@bigpond.com http://www.users.bigpond.com/kr2/kr2.htm -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net] On Behalf Of Larry&Sallie Flesner Sent: Friday, 25 August 2006 8:36 AM When I laminated my windshield bow and turtledeck bows from ply strips I used West Systems epoxy with a layer of KR cloth between each layer of ply. Light clamping pressure kept from squeezing out too much resin and the glass layer between each layer of ply has to add to the strength considerably. At least I assumed it does. So far no problems at 250 hours of flight time. Larry Flesner _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
