how should i fasten this joint?

[Dave Tesch]

i'm building an eight sided box; its not that complicated but its too hard for me to explain. i tried and erased it twice.

the problem i am having is this: i need to edge glue some joints that are cut with a 25 degree angle on a TS; so a 90 degree angle glued to a 65 degree angle (or 25 degree depending on how you look at it). the total angle makes a 155 degree bend. the stock is "3/4" ply and the length of the joint is 28". i spent around 5 hours today making a jig for assembly and about 20 hours making a dummy and cutsheets. i just cant see how to fasten the joint.

the last complicated box (complicated means more than six sides :D ) i made had seven sides and the weird angles were 120 degrees. i was able to effectively use a brad nailer to fasten the box even on the 120 degree angles. i dont know that i can brad nail at 155 degrees as it really is a shallow angle. i also dont know that i can use screws either.

i havent cut any pieces yet as i have yet to find decent stock; all my jigs are made for 3/4 dimensional plywood but i cannot source any locally right now - its all too undersized.

imagine that the arrows point to 3/4 plywood pieces, the flat piece is cut at 90 degrees and the angled piece is cut at 25 degrees.

178760

[Dave Tesch]

this is the seven sided box

http://inlinethumb54.webshots.com/24053/2544257350026985969S200x200Q85.jpg (http://outdoors.webshots.com/photo/2544257350026985969pwboQi)

the eight sided box adds a back, and changes the 120 degree angles to 155 degrees.

like this picture:

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[Chris Padilla]

Add some temporary glue blocks such that you can put a clamp on it.

[Dave Tesch]

i'm not sure i understand. can you explain more?

[Peter Quinn]

Is the plywood being covered? If so simply glue or screw clamping blocks to the faces that create 90 degree clamping faces, then remove them later before skinning the cabs. If you run a few biscuits or a spline it will help things from moving around too much. I haven't made speaker boxes but I have made corner cabs for TV stands with similar geometry using this technique. Another options is to put the total angle on the sides, leave the back square, maybe a slight rabbit, and nail that part or staple it to hold the glue.

[johnny means]

I do this with a technique called V-folding. Imagine what your box would look like if you ran tape across all your outside corners then "unfolded" the box. That is what your going for. Lay the parts inside down so that you can tape all your joints. flip the entire assembly over, apply a nice bead of glue (I prefer caulk) inside the Vs, then fold the entire thing into its finished shape. Rap a little tape around it to hold everything still, let dry. If done correctly the taped joints will pull nice and tight. No clamps or fasteners necessary.

[Dave Tesch]

I do this with a technique called V-folding. Imagine what your box would look like if you ran tape across all your outside corners then "unfolded" the box. That is what your going for. Lay the parts inside down so that you can tape all your joints. flip the entire assembly over, apply a nice bead of glue (I prefer caulk) inside the Vs, then fold the entire thing into its finished shape. Rap a little tape around it to hold everything still, let dry. If done correctly the taped joints will pull nice and tight. No clamps or fasteners necessary.

this is possible with part of the box. the two side pieces could be combined into one piece. i read about this method here before and it was one of the ideas i had in mind. how much material do you leave, and do you have to use water?

i hate to flip flop but i may change my design to something simpler. i have a little bit of time in this project but after reading these answers i have new ideas and am questioning the reasoning behind having 8 sides instead of a six sided trapezoid.

i'm going to sleep on it and see what i think tomorrow.

[John A. Callaway]

make clamping cauls to give parallel surfaces for clamps to hold the joint tight while the glue dries.

[Lee Schierer]

Either the "v-fold tape" method or a band clamp is your friend for odd shaped joints. Glue alone should be strong enough for most applications. Only Norm used brads to hold things in place while the glue dries. You never saw him filling all those brad holes and sanding the filler flush.

[Garrett Ellis]

are you trying to avoid using any kind of internal frame/structure?? that would seem the easiest way, like the picture in post #2

[Ryan Hellmer]

I would use splines and temporary clamping blocks. Additional structural strength would come from the ends (top & bottom) and any internal baffles/dividers. Is this for an install or for road work? Roadies can be pretty hard on equipment and jostling around in the back of a trailer has tested more than one speaker cab. Just wondering, looks like fun.

Ryan

[Dave Tesch]

it is fun.

its for the road, the boxes will spend most of their life in a truck. my plan is to make a pullover style case for the pair out of 1x framing and 1/4" ply so they dont get so banged up.

i also have pretty much decided i am dropping the eight sided idea and am more interested in the 6 sided trapezoid. i had originally wanted the eight sides to make the dado section for the baffle easier plus i wanted the challenge. with the 6 sided trapezoid the baffle is a little trickier in that you cant directly dado it into the non parallel sides, you have to make angled strips to fit into the dado and fasten the baffle in that manner.

and yes, one good drop with poorly constructed cabs will get you the following:

http://inlinethumb07.webshots.com/45958/2783033770026985969S425x425Q85.jpg (http://outdoors.webshots.com/photo/2783033770026985969Lzlqky)

here is the final product of the 7 sided box

http://inlinethumb55.webshots.com/18486/2368416770026985969S425x425Q85.jpg (http://outdoors.webshots.com/photo/2368416770026985969XSOvnw)

note the large knot visible in the picture. probably should have done something about that.

[Rick Fisher]

Dont laugh..

I would try Miter bond glue.. Which is basically crazy glue for wood.. 2 part..

I have used it before, usually in a few spots, with yellow glue in the rest of the spots..

Hold the joint tight for 10 seconds and the miter bond is done.. The yellow glue sets later and gives strength..