I'm just venting, not looking for advise:

I ripped the vertical stab off of my rummage-sale Skyray and put a new (non-offset and non-warped) one on in time to fly the 1st.  It flew very well, but at the end of the day as I cleaned the plane the thing snapped right off!!!  It's way cold in my shop and I used 5-minute epoxy rather sparingly, so either there just wasn't enough glue, it didn't harden properly because of the cold, or some combination of the two.

@#$%.  Got it home, sanded everything flat, put it back on with 30 minute epoxy this time.  In the process I noticed that in my hurry to get to Delta Park with a flyable airplane I had put a cutting mat on top of the rubber power model that was displaced to make room for the Skyray work -- I bent it's vertical stab over 90 degrees.  Argh.  So, let the Skyray sit out in the shop for two hours, then decided that I should put it somewhere warm to finish up.  The glue was firm, so I took the clamps off, hung it up in my office -- a couple of hours later I notice that the stab has fallen off.

%$@#.  Peeled the glue off (it hadn't set completely), redid the whole thing, hung it up in my nice warm office with the clamps on.  Guess what!  While the clamps were plenty sufficient to hold things straight with the plane upright, they weren't enough to keep it straight while hanging.  @$#%, *&^%, @&$% and *@#$.

So, once again, I need to clear the indoor rubber model off the bench (carefully), cut the #&^$ stab off, and do it again.

Some people build well because they're good.  Some people do as well as they do because they're pig headed.

Oink.

I haven't had too much problems bonding epoxy to old epoxy as long as the surface is sanded.  This didn't snap off at the old glue line -- it was more like the glue itself was porous and brittle.

At any rate, this time things got sanded down to bare wood in several places, and clamped thoroughly so it can not move thank you very much.  I'm not bringing it in here to set up, though -- I think I'm better off chancing it setting up in the shop (which is less cold today than the last few days) than I am chancing things moving from hanging it sideways.

So hopefully it'll be fourth time a charm!

I know that you guys tend to shun PVA adhesive but I use high-solids, high-quality PVA almost everywhere that does not require sanding—so long as I can leave components jigged to stay in place while the adhesive cures.

I still remember a demo given by my woodworking teacher in junior high school.

PVA was only just becoming readily available and I remember that only a year or two earlier, my dad was still using a hot pot of casien glue.

Anyway, this teacher had written the curriculum textbook for the New South Wales junior high school woodworking course.

He took a few strips of timber, planed the edges smooth and square and then glued them edge to edge to make a wide board, cramped them together and set them aside until the next lesson.

When the glue was fully cured, he invited students to try and break the joints. Try as they did, nobody could break the board along the glue joints. The glue soaks into the timber and reinforces the timber around the joint.

So long as I have the time, can clamp or weight the pieces together and ensure correct alignment and the joint will not need sanding, I use PVA. It produces very strong, slightly flexible joints—so long as you keep the amount of adhesive to a minimum. Years later, as development engineer for a building products company, I had to do some confirmatory tests and found that there was an optimum level of glue cover, after which the joint strength declined. So long as the PVA is high solids/little water and you apply sparingly, there is no warping. I used this technique with Randy Smigh-style balsa and carbon fibre doublers where I was able to leave the assemblies weighted down on a sheet of glass until the glue was fully cured and they came out flat. I have not yet tried it with ply doublers but I am about to.

Much cheaper and cleaner than epoxy.

FWIW the wax formed by the epoxy is called amine blush, can usully be cleaned with soap and water or alcohol. After cleaning, epoxy will stick to epoxy.

Oh fine then.  I just brought it into my office.  If I really have 12 hours, I should be OK.  It's clamped more thoroughly than before, so that should be fine, too.

(I think it may be cold that brought down the 5-minute stuff, so I am paying attention).

What the heck is "PVA" adhesive?

White or yellow water-based goopy stuff.  Elmers, Titebond, etc.  Most folks use "carpenters" glue, like Titebond.  If you can make a good tight wood-wood joint it's nearly as strong as epoxy, and much nicer for a variety of other reasons.  If I'm not in a hurry I use it for everything except exterior joints (it doesn't always sand nicely) and some motor mount jobs, depending on the details.

Original Titebond is an aliphatic resin glue like Sig Bond and the first Elmer's glue.  Titebond II is PVA (poly vinyl acetate) glue.
Titebond III is a proprietary polymer glue.
Alan Resinger

hi Tim,

Just curious:  Thin Medium or Thick CA wouldn't work on the fin/rudder??

Big Bear

Just curious:  Thin Medium or Thick CA wouldn't work on the fin/rudder??

There was epoxy slobbered all over the top of the fuselage, and I've never had good luck sticking balsa to epoxy with CA.

I'm not sure that I would have wanted to use CA for that joint anyway -- and I'm not sure why that is.  That sort of joint where you're butting a thin piece of balsa onto something always seems to cry out for epoxy or carpenter's glue.  I suppose I could make five sample joints with each of epoxy, CA and Sig Bond, then test all fifteen joints to destruction to see which one is best.  But that would be a pain in the behind!!

I would note that my last 3 or 4 planes were constructed entirely with CA (except for some thinned epoxy to fuel proof pipe tunnels and the like). Seem to be holding together fine.

Tim,

I understand. I've gotten to where I have to use a mask if I'm going to be doing a lot of CA work (like gluing down a wing skin or something). I've developed a certain sensitivity.

I too have serious sinus reactions to regular CA!!  Odor free does help, i pay the extra and haven't had the sinus thing since.   

Get the air circulating better when using CA.  I use CA to spot glue and white glue for final gluing.