sound post

A sound post crack?ouch! I'm not sure about plywoods, but on carved tops the best way is to do an inlay on the crack,

 

It sounds like a trip to a luthier is required. My guess is that you will need a round patch between the top and post (as you mentioned), but It isn't something you should attempt yourself.

 

Where did you recsive it from?

 

I don't have much (any) experience with removing a dent from a ply top. But you might try using a clothes iron from the back of the plate, while putting preasure on the dent from the front of the plate. maybe a bit of steam, also. It will be hard to get all of the layers of ply to bend back in shape, I imagine.

In theory, this is crazy talk to some degree, you could use a gouge and finger plane to remove, from the inside, all of the layers of ply, except the outermost one. then form it back into shape with heat, fix the crack, then make a sound post patch to fill in the lost layers of ply.

A sound post patched is a pretty advanced level of repair, though.You might want to do some serious googling first.

 

I used a similar approach to this suggestion on a plywood classical guitar top that was split under the bridge and distorted where the bridge was pulling up. I used a steamer and a clothes iron to flatten the area that had pulled up with the bridge. It flattened out real nice. In spite of the plywood being cracked all the way through, the laminates were still joined. I did add some reinforcement cleats inside under the bridge before remounting it. I also filled in some shavings for the splinters that pulled away with the bridge. Another thing that helped was clamping the top under cauls while it cooled and dried. I have used the clothes iron / steamer to straighten warped solid spruce tops as well. It is surprisingly effective. Just heat the wood and push it to the shape you want. Stay away from the finish with the iron.

 

with your finger rub some glue(variety unspecified ) into the crack...cut a piece of clear plastic(so you can see the action)and strong enough for clamping about twice the size of the bulge and something of similar size for the underside to sandwich the top..gradually build heat..clamp through F hole... maybe just before you clamp put a little more glue over crack so it will hopefully get squeezed in. think about relocating the position of the SP after repair ..nothing says it was in the right spot to begin with.
recommended for low value merchandi$e or instruments with questionable esteen

 

bgc, your original instinct i think would be fine, you just need to reinforce the back of the plate at the bulge with something,

Bob or someone else will correct me if I'm off the track, but my instinct would be to use 3-5mm pine or spruce patch about 100mm across, clamp it nice and tight, and when it's glued in nicely, feather the edges with a plane. the crack in the front is only a split and will probably not be a problem. ply basses often have a sound post patch on front and/or back and most I've seen are quite crudely done ... but they work.