PL premium and GRK lags. Why complicate things?
In answer to your original question, resourcinal was/is used for laminating wooden aircraft parts, and is an excellent adhesive.
We build houses and in our area no glue is needed. its nailed together to put up and then bolts. GRK lags are good.
Casein glue was used eons ago for glulams, but they changed to resourcinal for durabilty reasons. I have used this version https://www.amazon.ca/Aerodux-Resorc.../dp/B00DP5VQD2 , but if you read the MSDS sheet you might not be comfortable with it. Keep in mind the clamping used in glulam production if you are inclined to build it according to standards for beams ( https://edmontonjournal.com/business...gth-and-beauty). That is difficult to replicate in our shops. Sure, I know most of use have built endless things with far less clamp force, but those items were furniture pieces where nothing of significance falls down if they fail. Epoxy requires far less pressure and that is what I would use if I were going to do this.
I would go buy an LVL, PSL, timberstrand, or glulam and move on with life. At a 12'-0" span you should be able to justify a built up dimensional lumber beam. Any decent sized supplier has the software tools to size a beam for you.
I built a 20" truss for my sawmill shed roof to allow long log handling. It's under the roof but exposed to moisture in the air outside. After my research into adhesives resorcinol was it for weatherproof issue. Sold in box stores. In an interior location you have other choices?
I once called Titebond about that warning on label. Tech guy said it was just a liability thing against stupidity.
All of the manufacturers I've viewed literature from, so far, are saying to use nails spaced at certain distances apart. But I would feel better about it if I also used a structural glue. I have used both West Systems epoxy and resorcinol many times for making outdoor signs from redwood and cedar. Of all the glues I've tried they are the best; especially the epoxy. I have done my research on the load capacity for the beams but will do some more; because I may be able to use slightly longer ones. I ended up purchasing some 14' LVL's from this place. http://www.wholesalewoodonline.com/ They are to be delivered next Tuesday.
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Wayne Webb
Webb Signworks
Chipley, FL
Aspire 9.5
Sign Wizard 6.0
CorelDraw 2018 Suite
DevFoam Pro
Mach3
Shopbot Router 4x8
Ioline 24'' Plotter
Mimaki 51'' Plotter
Home-Built 10x7x4 CNC Hotwire Cutter
Various Metalworking and Woodworking Machines