FWIW ... & More to Follow -
To add on to Dan's comments re/using PS890 as an "adhesive" for certain steps in the construction process I would offer the following -
The Technical Data Sheet for PPG's P/S 890 Class B Fuel Tank Sealant (available on line) lists its use as "...is an aircraft integral fuel tank sealant". No comment in the Description section as to it's adhesive properties. In the Performance Properties (typical) section it lists its tension strength, standard cure, 14 days @ 77*F, 50% RH as 300 psi - there is no overlap shear strength (most of our "skin" loading) noted in the properties description.
As a comparison, 3M ScotchWeld 2216 Epoxy Adhesive's TDS lists its OLS (Overlap Shear) strength for Aluminum/Aluminum bonding as 1800 psi @ 75*F with the appropriate surface preparation.
In summation - P/S 890 shear strength: Not Listed
3M 2216 shear strength: 1800 psi
Draw your own conclusions ...
I am the "tester" Dan alluded to earlier, and am currently waiting for the trailing edge coupons using P/S 890 sealant to fully cure (14 days), before completing the OLS tests. I can tell you, preliminarily, that the OLS tests on trailing edge coupons using .016" 2024-T3 strips (simulating mating skins), a 1" square section (1/2" x 2") trailing edge material & 3M-2216 epoxy adhesive, produced the following results (to failure) - 750 lbf to coupon failure, not joint failure. In other words, I pulled the test pieces of the .016" 2024 apart before the "glued" joint failed.
As a point of reference - I have been using 3M-2216 to "glue" my builds together since the late 1980's. So I have some experience using this product. I have also been testing all manner of "joint" design with an in-line OLS testing device (of my own design/construction), using a 3K load cell with digital readout. I have tested over 200 joints in that time, proving/disproving whatever my interest was in those particular joint compositions.
I (personally) settled on 2216 early on when I realized I wanted an adhesive that was:
1. Approved for aerospace use (Beech Sundowners used it for wing/skin mating).
2. Had a bit of "ductility" to help in absorbing the micro vibration that our planes go through during operation.
3. (Fairly) simple mixing/application procedures - preliminarily using tooling of my own design/mfg.
4. Rapid cure rate in an autoclave - convenient for smaller parts.
5. Comes in bulk as 2216 or in 1.6 oz cartridges as DP190. Same properties, different formulation for purposes for convenience of mixing.
HFS
Harmon Rocket II S/N 002
Flying 22+ years - no "smoking" rivets & no fuel tank leaks ...
There are many other suitable adhesives out there, subject to personal preferences - 2216 just happens to be mine.
Thanks for listenin'
