ULF-1 Discussion Archive
Anonymous static archive of the former Mailman list
Anonymous static archive of the former Mailman list
Re: [ULF-1] Ulf-1 Digest, Vol 70, Issue 14
Member 67, you are absolutely right! Flocked cotton (flox) is structural, micro is not. Also micro is porous. If you fix a fuel leak with micro the fuel will wick right through. I've built two LongEZ's, ask me how I know - LOL. On Wed, Jun 13, 2018 at 2:03 PM, <[email]> wrote: > Send Ulf-1 mailing list submissions to > [email] > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.ulf-1.com/listinfo.cgi/ulf-1-ulf-1.com > or, via email, send a message with subject or body 'help' to > [email] > > You can reach the person managing the list at > [email] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Ulf-1 digest..." > > > Today's Topics: > > 1. Re: Epoxy bonding (Member 121) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 13 Jun 2018 09:12:17 -0700 > From: Member 121 <[email]> > To: [email] > Subject: Re: [ULF-1] Epoxy bonding > Message-ID: > <CALUQ4rd1+YpvK9Ck0+QsJ1dZ6tMm=4QX6ZpFFAarKzZjKi=b > [email]> > Content-Type: text/plain; charset="utf-8" > > Cool . > Did you ever hear of fiberglass drywall tape? Wrapping struts near > the cocpit to prevent splintering impaling effects ? But some fiberglass > is unravel -ish when cut into strips . Cotton linen was used in ww1 on > propeller tips . > > On Wed, Jun 13, 2018, 9:06 AM Member 72 < > [email]> > wrote: > > > Hi Doug, > > > > All very good advice. One thing we did on our ULF-1 build was to mix > flox > > (floculated cotton) into our T-88 glue batch when we needed to thicken it > > up a bit to help fill some voids in the joint, rather than micro > balloons. > > We found flox to be structural in nature and added strength to the joint, > > while microballoons was more cosmetic, not adding much strength to the > > joint. > > > > Thanks, > > Member 72 > > > > > > > > Sent from my iPad > > > > > On Jun 13, 2018, at 1:43 AM, 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 > > > > _______________________________________________ > > ULF-1 discussion list -- [email] > > > > Subscribe, Unsubscribe, Preferences, List information: > > http://lists.ulf-1.com/listinfo.cgi/ulf-1-ulf-1.com > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.ulf-1.com/private.cgi/ulf-1-ulf-1.com/ > attachments/[phone]/d5c11fed/attachment-0001.html> > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Ulf-1 mailing list > [email] > http://lists.ulf-1.com/listinfo.cgi/ulf-1-ulf-1.com > > > ------------------------------ > > End of Ulf-1 Digest, Vol 70, Issue 14 > ************************************* > --