Stringers end then foam?

[flipbro]

I recently started a restoration on a 1989 Tempest 23 footer cabin cruiser. I've gutted the cabin and to my suprise the stringers only run to a bulk head just in front of the cabin entrance. From there it's a big cavity of foam. And fuel tank . Then at back of boat about five feet another bulk head stringers and motor mounts. Why don't the stringers run the length of the boat? There not just rotted they were never any there. Above the foam is a small after cabin. Then deak up top. The deak is solid but cabin and engine bay are toast.

 

[Peter Eikenberry]

They don't run the full length of the hull because the hull is stiff enough to maintain it's shape and not twist and flex much under speed. At least that is the theory. The only place they are required is in the way of the engines to provide secure mounts and reduce the torque and vibration transmitted to the hull.

 

[flipbro]

So I would have to assume that the foam in this boat is structural and not flotation foam since the boat is over 20 feet? And if so I should use the 4lb density 2 part foam?

 

[ondarvr]

2 lb was used when it was new, and it didn't fail, so 2 lb is fine.