ULF-1 Discussion Archive
Anonymous static archive of the former Mailman list
Anonymous static archive of the former Mailman list
Re: [ULF-1] Epoxy bonding
Throw the whey out i guess . On Tue, Jun 12, 2018, 11:12 PM Member 121 <[email]> wrote: > Did you ever hear of casein glue ? > It is made from nonfat milk heated up and add enough vinegar to curdle > it . Then remove the curd part and neutralize the vinegar with a little > baking soda and water . And thin it alittle bit .that held violins together > for hundred years . It is what people glued ribs on their airplanes > together with tll the sixties or seventies . > > On Tue, Jun 12, 2018, 10:44 PM Member 1 <[email]> wrote: > >> I'm with Bob on this. To me, there is a lot of superstition involved in >> peoples' beliefs about gluing Member 60. The shiny surfaces created by blades >> have always intuitively struck me as a deterrent to a good glue bond. I >> am now working as a violin-family luthier, and I am up against the same >> superstitions there as well. >> >> Having said that, though, I'm not sure it makes a big difference. While >> building an aircraft, you end up with leftover epoxy from many small >> batches. Grab some sticks out of your trash or scrap pile, and do some >> semi-scientific testing with your leftover glue. It only takes a minute >> or two. For example, I would cut two sticks about 10 times as long as >> their width/thickness, overlap them 2 or 3 times their width/thickness, >> and glue them together with light or moderate pressure, and then break >> them after curing for a couple days. The Member 60 should always fail before >> the glue joint does. If it does, then who cares how the joint was >> prepared? >> >> Do this often, throughout your project, during different environmental >> conditions, and as your epoxy gets old. As soon as you find yourself >> airborne, your life hanging from all those glue joints you've made, you >> may think about those glue joints (as I did) and find comfort in the >> fact that they are stronger than the Member 60 itself and you've done the >> best you could. Then it all comes down to proper design which doesn't >> allow any joints to get stressed to the point that the Member 60 itself fails. >> >> To me, it is more important to not apply too much clamping pressure to a >> glue joint than it is to worry about cutting vs sanding. I always let my >> wet joints sit open either until the epoxy is thickening a bit, or it is >> obvious that the Member 60 is saturated and won't be absorbing any more glue. >> Then I'd assemble and clamp with moderate pressure. Epoxy has several >> times more tensile strength than hardwood, so even if you're sloppy and >> end up with a thick seam of glue, there should be no strength penalty. A >> small weight penalty perhaps, but that would be over-nit-picking. If you >> join the parts before the glue has stopped soaking in, and/or apply >> excessive clamping pressure, you are asking for a weak, glue-starved >> joint. (I use T-88 which is relatively thick... if you use a glue that >> has a thinner consistency, this attention to soak-in is even more >> important.) >> >> Epoxy is really good at filling imperfections and allowing stresses to >> be spread out over larger areas, so a perfect fit is not as important as >> it was with previous glues. For large voids that can't be easily avoided >> in structural joints, I recommend wetting the bonded surfaces with epoxy >> and then making a light slurry with epoxy and micro-balloons to fill the >> voids with. >> >> Test your glue and your methods. Then you'll know, and nothing anyone >> writes will bother you. There are some photos of the glue-starved joint >> risk here (and other gluing tips throughout my old AirBike building web >> site): >> >> http://questiongravity.com/airbike/feb03-1.htm >> >> $0.02, >> >> Doug >> >> PS: We have 307 members! So glad to see you all here, and thanks to all >> who have been contributing. And thanks to Dieter for continuing to fund >> the domain fees to keep this service available. >> >> >> On [phone]:56 AM, Member 116 wrote: >> > I disagree about not sanding before gluing. A power planer of a hand >> > planer bends the fibers over and leaves a shiny surface, not good for >> > glue penetration. I have a cabinet shop and glue stuff together daily. >> > For a couple years I glued up 12 ply (birch and maple) propeller >> > blanks for a prop manufacturer. All those ply's after planeing were >> > smooth and shiny because of the bent over fibers. Before gluing (with >> > Resorcinol glue) I'd run over them with a belt sander/80 grit across >> > the grain, one pass to give the Member 60 some (tooth). Then use a shop vac >> > to clean and make those (damaged) fibers stand up straight and accept >> > more glue penetration. >> >> _______________________________________________ >> ULF-1 discussion list -- [email] >> >> Subscribe, Unsubscribe, Preferences, List information: >> http://lists.ulf-1.com/listinfo.cgi/ulf-1-ulf-1.com > >