oldtimer

what glues were used in the 1980's and 1990's for the wood wings in our biplanes?

is anyone flying an aircraft with wood wings using urea formaldehyde glue?
(also known as Weldwood Plastic Resin glue or Aerolite glue)

is there a test to determine what glue was used in the wings of my1992 Acro sport I?

any answers appreciated....larry....




Edited by: oldtimer

SteveN452

I built my Acro Sport II in 1982-1986 and I used Weldwood Plastic resin glue for all of the woodwork. Airplane now has 600+ hours with no wood or glue issues that I am aware of.
As I recall, Weldwood Plastic Resin glue was FAA approved at that time.
Hope this helps.
Steve
Edited by: SteveN452

oldtimer

thanks steve: that is good info to have.my glue joints are brown in color,so i am thinking i have weldwood glue joints.
.........larry..........

Neil

Many of the airplanes built in that time frame used T-88 epoxy and it is still a favorite.

BC12D

My Acro-II (under construction for a long long time) and a friend's KR-2 are both held together with West Systems. It has been around in the boat world for many years. Technically, it has a bit lower glass-transition temperature than many other epoxys, but is a really good general purpose epoxy. It flows better than the rather thick T-88 but T-88 seems to penetrate on glue joints almost as well as Resorcinol. T-88's only (minor) complaint is that being a 1-1 mix, it contains inert fillers. No Epoxy is 1-1 resin to hardener. Folks have always liked the West System's pumps as they make the mixing simple and consistent. I have noticed that as West hardener 206 ages a couple of years it turns brown. West Systems say that the chemistry isn't affected, it just looks dark. But I don't think that even my most elderly 206 hardener would darken a glue joint enough to call it brown.

The Weldwood Urea resin glue has been FAA approved, but is generally considered as surpassed by the Epoxys and Resorcinal. It's not a bad glue however. It has a long history and the mixing is easy. it wouldn't typically leave a brown joint.

The original AcroSport-II book and plans recommended Forest System Laboratory FPL-16. This was a light brown epoxy that might have been used in your plane if the glue lines are brown. I read the reports on FPL-16 as it was run through mil-spec tests (one of the few epoxys at the time to do so) and had excellent properties other than the normal epoxy weakening at high temperatures. It was fairly scarce and expensive, but as it was recommended on the AcroSport plans, it may have been used. The brown glue line hints at it. I haven't used FPL-16 myself, but have heard the light brown colour mentioned.

I am currently building new spars for my Taylorcraft and I am using Resorcinol. It is currently made by Bordon but has been marketed in the past by both Weldwood and Dap. Official name is Cascophen G-1131. it is the best of the FAA-approved glues for wood joints. If your glue lines are dark brown or purpleish-brown, then it is probably Resorcinol. The Resorcinol joint will be quite dark brown where I have heard that the FPL-16 joint will be more of a tan brown.

Having used both Epoxys and Resorcinol, I am a fan of Resorcinol. It doesn't have the heat problems of Epoxy, and it doesn't have the water problems of the casein glues. You do need a good scale to get the 5:1 weight ratio. If I had to splice a spar I would use Resorcinol over any of the Epoxys.

As always, corrections are welcome.

Skip

bf92

I used quite a bit of the FPL-16A on my Pitts back in the 1980's. It was as white as white could be. It was an excellent glue, but rather thin, and I usually let it set in the cup for a bit before using it so it wouldn't run out of the joint. It was a 10:1 mix, and I used a 50cc syringe for the glue, and a 5 or 10cc syringe for the hardener, cleaning them with acetone afterward. I could get about five uses before the syringes succumbed to the acetone and had to be replaced. Excellent glue. A chunk left in the bottom of the paper cup could be machined on a lathe or mill after it set up!

Danny

__________________
Local FAA inspector:\"Remember, we\'re not happy till you\'re not happy!\"

BC12D

The original FPL-16A tests are documented in [Olson, W.Z. and R.F Blomquist. 1962. Epoxy-resin adhesives for gluing wood. Forest Prod. J. 12(2): 74-80] and describe Titanium Oxide as a filler material (100 parts resin, 30 parts Titanium Oxide be volume) which would make it very white! Now I am trying to remember where I got the " brown" filler comment. I don't think that the filler was changed, as the filler was one of the variables in their tests. That's what I get posting in the middle of the night from memory. Thanks for the corrective memory jog!

I need to play with FPL-16A again.

Skip

Knight Twister

I used FPL16A in the '80's as well. The local guru who did all our Pitts upper wing spar splices wouldn't use anything else. It was not the easiest glue to mix and use but I still consider it the best.

TFF1

Resorcinol is the best to use except one thing, you have to be a master joiner and be able to clamp the heck out of your parts. Epoxy wins because of ease for the average guy. It works well for what we do, and you just cant screw the joint up as easy as you can with resorcinol. That makes it safer for the average person.