BillFitzmaurice.info

Hello Forum,

I am currently in the process of having x4 24” wide Tuba 30s built. I am overseeing and helping with the build process where I can.

I would like to ask what type of fastener is best to secure the access panels?

I have considered installing T-Nuts in the flange and using cap head allen bolts (countersunk). Would there be a risk of the bolts backing-out over time if I went down this route?

I understand that using coach screws would be simple and effective, but I’m concerned the screw holes might degrade slightly with every time the panels come off, even if this may not be a regular occurrence.

Aesthetically, the cap head screws will look more professional, and small aesthetic details in like these are important to me, admittedly.

My second question is with regards to alleviating the gap and slight overhang that is present when fitting metal (stacking) corners to the top front corners of the Tuba.

This gap I describe occurs because the ply width is slightly too thin for the corner and because panel 7 slopes away, so the corner is left overhanging, if this makes sense.

Would there be any problem (sonically or otherwise) If I were to fabricate a piece at the top of panel 7 which will fill the slight gap behind the corners? Maybe a lip that runs across perhaps? I would rather check before making even this small modification to the design. This is a very minor aesthetic detail, but the look of the overhanging corners really bugs me!

I will say I have specifically chosen metal stacking corners over the plastic ones, so using plastic corners instead and shaving them down isn’t a viable solution for me.

Any advice or wisdom would be most appreciated.

Thanks,

J.

Hi, and welcome to the forum!

If you insist on using recessed bolts, then I would suggest using 3/4' or 18mm plywood for a cover since you would have to add a flat washer and a lock washer. Since the cover would be thicker, then the flanges would have to be set in farther to accommodate it.

Using screws is plenty fine. When reinstalling the cover, back off the screw slowly and gently until it "falls in" into the screw groove from before. Having said that, how often do you intend to remove the cover? Others can share how often they have removed the screws from their covers, and if they have any difficulty. Besides, if the hole gets stripped, then it can be filled in again with a splinter and adhesive, and redrilled.

If you want to fill that gap behind the corners at the top of panel 7, it is no problem.

I put more thought than necessary into the access panels pre-build, but in the end just used black drywall screws to attach them because I was under the gun to get them ready for an event. I've since gone back and replaced them with truss head screws. Since you're so close to the edge, the countersunk heads can mess with the top layers of the plywood, making splinters and such. I have since though about framing the access panel with aluminum angle but haven't tried that. As for t-nuts on the back side, I'd stick with wood screws. Like Tom said, easy to repair if necessary, and much easier than getting all those t-nuts to align perfectly.
With regard to corners, I used the big plastic ones. However, along the bottom and up both sides of the mouth, I laminated in a couple inch deep strips of 3/8" BB. At the top, I trimmed it to match the slope of the panel. This makes the front edges of the cab look like it's made from plywood thicker than 1/2" - just an appearance thing. But it made the corners look better too. There should be a picture somewhere back in my build posts.

Thank you both for your quick responses to my questions.

I am going to take your advice and just go with wood screws to begin with to keep things simple. Framing the access panels with aluminium angle is something I may consider in the future however.

Himhimself, I have indeed seen your build, employing the strips around the mouth of the cab. I like how this looks, and it would solve my corner gripe. I am planning on staining and varnishing my cabs, do you think I would still get away with having strips around the mouth without them standing out too much? I’m imagining they could be physically contoured to help them blend in?

Thanks,

J

I cut the back side of the strips at an angle for that very reason. The front will just look like more plies of wood. So I think it could look fine, although I am a huge fan of duratex - hides so many little blemishes and oops. The top edge of the mouth is still a little weird with the way the cabinet is designed. I may put some extra material there when I build my next two. I like the way that area looks on my truck tuba much better, as there is a larger front surface after cutting off the angled panel. Then again, not much to notice on black T30s in a dark room with the distraction of monstrous bass blurring your vision and shaking your soul...