Dowels?

[fender3x]

I am now at about the half way through the construction of at T39, and have run into a question, based on a little experiment. I glued two pieces of the plywood I am together at 90 degrees, and let the PL cure overnight. In the morning I broke the joint, just to see how much manhandling it would take.

It broke far more easily than I would have hoped. I am using maple plywood. The lumber yard guys told me tha the core is poplar, it was staight and has 5-7 evenly sized plies, but the veneer is very thin maple...best I could get (and not cheap) given that I could not find BB in this area... At any rate, the PL held, but the thin maple veneer on the plywood broke away. This made me wonder...

I know that the screws add very little to the actual strength of the joint, and I will be pulling them out anyway around all the edges where I will run the router. I have started to think it might not hurt to pop in a 1/4" dowel into all the places I pull out a screw. Assuming I fill the hole and coat the dowel with lots of PL it should seal well. It should join better than a screw-&-PL alone butted joint. It should not cause problems for the router. So, aside from the hour or so to replace the screws with dowels, and the extra 24 hours curing time... Is there any disadvantage to doing this?

Am I being over-cautious? It has also occurred to me that there are a LOT of butted joints on the sides--not to mention a butt-load of dadoed joints front to back. It would probably take a lot of stress to cause a problem, in spite of the thin veneer.... Still, over cautiousness I can live with...

[LelandCrooks]

Nothing wrong with that idea. I also used some plywood that had a very thin veneer and would pop the top veneer. I biscuited the whole box for that reason. The dowels would serve the same purpose.

[Bill Fitzmaurice]

Dowels can't hurt. In the future you'll know that you should avoid plywood with a thin outer veneer.

[fender3x]

You've got that right. I found pine that met the specs, but thought this would be of a quality more like BB... and the *inner* plies may be. Now I know that poplar-core-with-thin-veneer is a bad trade decent pine/fir with a thick outer ply... I just hope all these lessons are prepping me for the next project: a DR250 <cue scary music here>.

[vexorgtr]

I made a pair of Titan 39's out of wood that would make you cringe. It was some pine plywood that was more warped than the federal government........ I eventually built what looks like two pretty decent Subs... There's very functional, but don't grab the square... you may just find the warp.