Guidance for rebuilding our transom

My son and I recently acquired the 14' 1971 Ouachita V hull that my father and I fished with when I was a kid. So we have a new project and the first thing to work on is the transom. Ive seen several transom projects where the board is fully or partly exposed but in our case the board is fully enclosed with two overlapping aluminum panels. The top panel seems to be held in place by the welded in corner gussets. If anyone else has worked on a similar project we would appreciate some guidance as to how to best begin. We don't want to do any unnecessary cutting. Ill try to attach pics.
Thanks in advance for the help.

First rempve the knee and get it completely out of your way.

See sketched. Is that 'shelf' (part 3) located at the bottom piece of the inboard transom a separate piece from the panel (part 2)?

If so, is the shelf riveted in? If so, you may be able to remove the shelf and get it out of the way. This presumes that the panel, at the bottom, is simply 'folded in' to encapsulate the wood transom.

It might be tight, but if you can remove that bottom shelf portion and pry up that panel enough ... you might be able to slide that old piece of wood out. Even if you had to use a sawzall to rip it in 2 lengthwise (across the boat) to get it out. SAVE the pieces as a master, alllowing for the kerf.

If you had to rip it in 2 to get it out ... your replacement transom wood could be 2 pieces, using a staggered joint. See sketch, just for ideas. This should minimize bending of the top of your welded 'cap' on the current transom, although you will need to pull that panel out some for access to the work. All depends if that shelf can be removed.

Just my ideas ...

Oh, and DO NOT use pressure treated wood!

I was thinking going through the bottom as well once the knee is removed. Aluminum flexes and bends easy enough that it may go well without cutting.

Thanks for the thoughts,

The knee was through bolted to the transom but is riveted to the hull. We were waiting to remove the rivets just incase we didn't need to.

The shelf is a separate piece from the panel and it is riveted to the bottom of the transom. Even if the shelf was removed it is at the beginning of the curvature of the bottom of the boat and any wood left in the transom would not be able to be removed in that direction and new solid wood would definitely not go back in.

The top panel was through bolted and once the bolts were removed it is loose and separate from the shelf. At this point the only thing holding the top panel in is the corner gussets and a small weld on the outside of the panel that is holding in to the transom.

I think if the gussets were gone the top panel would simply slide straight up without removing the knee from the hull, slide a newly prepped transom board in and drop the upper panel back on. Seems overly simple. We just wanted to make sure that was the correct direction to go before we got the cut off grinder out and began cutting.

Sounds like your on track. Who is going to weld it? Can they look at it before you cut?

That's the plan, gather as much info as we can before we cut. We have a couple of family friends who are fabricators and welders that we're trying to get to come look at it. Hopefully they won't see too much difficulty in putting it back together.

Little boat is coming along slowly. Had the transom cut open and found the wood to be perfectly formed dust! So instead of replacing the wood, we built an aluminum frame and skinned it with 1/4” aluminum plate and reinforced with 1/2” in the middle. Put the old skin back on and it looks great and should be stronger than ever. A little paint and it coming along.