back to fEARful
thoughts on a fEARful build topic on a woodworking forum
Spurred by a Woodnet Forums fEARful build topic that has vanished (there were lots of pics)...
I just skimmed the thread, but I did notice author and builder Andy seemed to be inferring, Why Did That Guy Choose Butt Joints Anyway. But(!) as I've always discussed: I designed the fEARrful plans so that anyone could choose any type of joinery they thought they could pull off, with whatever tools they were comfortable with. Early on I decided the plan should be able to go together with butt joints and still have great structural integrity. Drawing the plan that way allows one to change other joint types without cluttering the plan with a lot of additional measurements others would not even be able to use. Experienced builders/woodworkers might have their own preferences for type or depth of join anyway, so drawing only butt joints allows them to transpose to their individual preferences.
¤ ¤ ¤
Andy also makes reference to a weakness where the spine brace meets the port divider in back. Doesn't he realize that there's no stress on that point in the first place? This is because of the area's (1) distance from panel centers, and (2) the incredible strength provided by the glue join between the back panel and the spine brace once the back is put on. PL Premium applied as I describe below certainly needs no additional "shoring up".
This reminds me of so many novice builders (and actually a lot of commercial bass cab builders as well) who put a lot of bracing runners along the edges leading into the corners where rigidity is already there structurally, while neglecting large open expanses of panels as you get closer to the centers of each. Those are the places where the panels are considerably less rigid, and less vibrationally damped. So that's where you need "strength" - and that's why the bracing is designed the way it is.
¤ ¤ ¤
I'm assuming with the removable back idea shown, that the back panel was intended to be glued in during final assembly. Because certainly glue all along the back girdle brace pieces and the spine brace supplies integral rigidity moreso than screws spaced every so often can, and it's essential to seal all joins against pressure leaks. I also find that any internal stuff yet to be done after the back is glued on is easy enough through the woofer hole or the connector cup cutout anyway... I think this fancy inset screw idea was an effort that ate time better spent elsewhere because that back panel needs to be permanently glued on - with PL Premium on all adjoining surface areas.
The way the project proceded does say a lot about the merit of building from front baffle FIRST, and working one's way to the back... placing the bracing and midrange chamber in, and then FINALLY building/gluing the back. Anyway. One can see by looking in the fEARful builds in progress or completed section that there are several ways to successfully assemble fEARfuls. To each builder his own individual approach hopefully has its merit.
why fEARful Cutkits had a few dados
The first guy to actually follow through and make some Cutkits for others was Swift713. We had earmarked key positions where dado cuts would make it easier for newbies to properly assemble the flat-pack Cutkits. These dados weren't for strength - they were there to align key elements easily. Also, we didn't want so many dadoes that the Cutkits would be labor intensive for Swift (or his predecessors). Working toward Cutkits with several different woodworking professionals before Swift713 codified my thoughts on where strength and convenience would result from dado cuts/routing, and where it just would become "fussy bits" and could actually introduce problems.
This is a point to consider: Too many dados actually demands higher accuracy of measurements and cuts in order to make everything fit together well. Arguably (unless you are trying to show off mad skillz) one gains very little for that effort. So (if I recall rightly) Swift713 and I spec'd dado cuts grouping the top, bottom and sides for each other, and the baffle, the shelf, and the port divider. Everywhere else in the fEARful plans, things really don't have any other way to go together - their locations are assured by notches, and the dimensions of the bracing pieces - and defined by the interior provided by the top, sides and bottom. So. Adding dados for say the girdle braces or midrange chamber or the spine brace... well, that just makes one have to be incredibly accurate to get perfect lineup of each and every interior element as it is added. Waste of time.
PL Premium and the butt joint
Instead one could just sail along quickly and let the PL Premium glue work its filling and bonding magic! Just make sure areas to be glued have been cleaned of dust - a lighty damp rag can be used if desired; slight dampness where glue goes down is fine. Later, when dry/cured, PL Premium sands nicely in places where it would show, so don't be too shy with it. Make sure panel joins have adequate coverage.
PL Premium is increasingly used in the very demanding field of marine construction because of its fill properties and strength, often with plain old butt joints - even when angles are not cut to join two pieces that actually meet at an irregular angle. In such cases (which we don't see in fEARfuls) the area where an angle cut would normally be used to get more wood-to-wood contact is instead just filled with PL Premium, and then "filleted". In effect, PL Premium is being used in boat work to replace troublesome angle cuts and large amounts of wood, and when it has just applied it allows one to actually build up an area with beads to get more glue-to-wood contact area which is so much stronger than wood. Quickly done, the beads can be smoothed into trough-like fillets (exaggerated in size here to get the idea across):
In fEARfuls, we don't really need to fill huge angle cuts. But filling and smoothing with a utensil comes in handy where pieces of bracing are meant to form a composite bracing assembly. You don't need bracing cuts that are exact since PL Premium can fill any irregularity and be stronger than wood, so the bracing pieces just need to fit within the enclosure "just close enough". Then dab some glue where sections roughly meet and smooth the glue with a small putty knife, spoon, or butter knife, making sure there is a little "buildup" when done.
The main area where beads being formed into fillets for longer distances comes in handy is within the woofer chamber - where both strength and airtight joints are desired. Much like caulking work, after gluing and joining panels, one can then run a long bead and smooth it with a utensil (see the diagram above). Even along Girdle, Pillar and Spine Braces where they have already been glued to panels, a little of this technique may be used if one wishes.
Below the woofer chamber where the port interior is you can do this too if you want. But make sure you keep the beads small enough to not be unsightly later, and you may not want to bring them too close to the front; I'm not sure how well Duratex bonds to PL Premium. Perhaps for visible exterior smoothing at panel joints and over screw or brad nail heads from the assembly process, Bondo (or possibly Plastic Wood) and sanding is preferable.
back to fEARful