From everything you say you've tried I doubt this will help, but you can increase your glue's holding power by coating the scarf cuts and letting them dry first. Then go back later and apply a second coat to both surfaces and reclamp. Also you might try more or less clamping pressure. If the wood is redwood I think some other substance must be interfering with the bond as I have a large supply of reclaimed redwood tha I have successfully glued with Titebond II and other aliphatic glues. You can try epoxy as glue if you have it on havnd already. It would be OK for scarfing but would add a lot of work and timeif you use it for joining your strips edge to edge. Luck, Tom

: I recycled some old tongue and groove siding to make strips for the Great Auk
: I'm building. The wood is absolutely clear, has a reddish tint and is very
: uniform in color. Its light and brittle. I assumed it is Western Red
: Cedar, but wonder if it could be Redwood. I have 9' lengths and am
: scarfing a few strips to start. I made a 'shooting board' to plane 2"
: scarfs. My problem is that they don't want to stay glued. I started with
: Titebond II. When it didn't stick at all after two hours in the clamps I
: went out and bought a new bottle. When that didn't work any better I
: bought Elmer's Carpenter's Glue; same result. I have some tests drying
: overnight, but I'm afraid they won't take much bending. I tried the joints
: straight from the plane, and lightly sanded. The temperature is in the 70s
: with medium humidity. Clamp pressure is moderate. Both glues work fine on
: fir. Could I have some wood/glue incompatibility? Suggestions of
: identifying my wood and glues to stick it together would be appreciated.