Indentifing rotted stringer material

Okay... I know another stringer question but my problem is the stringers in my boat are complete mush. I can not tell for the life of me what type of wood there are made from. The boat is a 73 Thunderbird 190c. I understand that there are alternatives to wood but the top of the stringer (the fiberglass ) was compacted and the fibers were all spread apart. This leads me to believe that the sole is supported by the stringer as well as the stringers giving the boat support. So what material was most likely there (it's not plywood) and what would be my best choice for new material. I would like to maintain the structural integrity of the boat.

 

Identifying rotted stringer material

By mush - do you mean firm looking on the outside but 'pulp' under a thin skin ?If so it was possible a soft wood - pine, ash or cedar, or one of the cheaper imported timbers.
Larch, if you can get it, is superior. Elm even better.

 

I'm pretty sure they were Douglas fur or Southern Yellow pine in your boat. A good American white elm will make a nice stringer if you can find it. It's about 37 pounds a cubic foot, not near as strong as white ash (which it is often confused with) nor will bend as well.

Your boat was typical of the era's construction methods, choppered 'glass over some wooden structural elements. The layup of the 'glass was heavy in the hull shell. The stringers did help support the sole, but what you're seeing on the stringer tops, is the random fiber pattern of a chopper gun laminate. These can often appear dry, loose and look crushed, when in fact they just didn't get wet out properly during construction (not uncommon).

You have little choice, but to cut the tabbing away from the hull shell to reveal the stringers. You can save the tabbing pieces for re-installation, or make new ones. It will likely be imposable to save the stringers for use as patterns for new ones, so make reference marks, take lots of pictures and measurements.

 

Berg: by mush I mean that the wood is completely rotted there is no structure left of the wood and it is completely black in color.

Par: You explained what the fiberglass looks like exactly. Yeah there really isn't enough of good material to use in order save anything so I will mark out the outline of the stringer on the hull and measure it all up then start from scratch. Being a newbie at this I plan on taking my time and asking questions so that I get it done right. I will be calling on the assistance from the fine members of this board to make sure of it.
Thanks to you both.

 

I recomend make a template before you cut them out. This will give you proper angle and elevation. After they are cut out, you have to loft from scratch.