I've been meaning to start a discussion on the differences between the early Argosy (74-76) motorhome cockpit windows and the Classic (including Argosy 77 & later) cockpit windows. So here it is
This first picture shows the cab structure and floor configuration for 74-76 Argosies. Note the cockpit floor does not extend past the inner wall. In 77 and later Airstream extended the wood floor all the way out to the outer wall.
And this one shows what the structure is like for an 86 Classic 345. From examples that I've seen from 1977 until sometime late in the Classic construction this should be the norm. The only variation would be the lack of drain tube in the 77-78 Argosies and possibly early Classics. Note the wood floor does extend all the way to the outer wall.
Next I've made a couple of detail sketches showing the wall structure differences. This first sketch shows how my 74 was configured.
This one shows from 77 and later. The only variation that I know of is the lack of drain tube in the later Argosies.
Something I should mention is the cockpit wood floor in my 74 is original, is still solid and I didn't bother replacing it when I was rebuilding that area of the cockpit since it was in such good shape. Why mine is in such good shape I can't say for certain because it still had a flaw in the design in how the water drains from the cockpit windows. If you look at the 74 sketch, in the upper cab frame channel I have an arrow indicating where water collects if the weep holes are plugged or otherwise not draining. I have no idea why the water that collects there didn't drip down the inner wall and onto the wood floor but it didn't. I have a hunch it's because the water actually drained at the back end of the channel and then ran down onto the floor by the door which is lower than the cockpit floor. It also just so happens that area was rotted out!
In a discussion with Martin as to why the water wicks through the window seals he had an interesting theory. I'll let Martin I'll let him discuss that issue as he understands it a whole lot better than I do!
The simple fix for the 74-76 Argosies is to drill a few holes where the water collects in the aluminum channel. The water will then drain down and out and since there is no wood floor there to block the flow of water there is no harm to any flooring. This is the fix I made to my 74 and after drilling the holes I no longer had water draining onto the floor by the door.
If you look at the second sketch you'll see how the floor was extended out to the outer wall. Airstream changed the structure of the cab framework somewhat but nothing that affects how water drains. The 77 and later models had the same drainage issue as the 74-76 models and it was only made worse by extending the wood floor to the outer walls. After X number of years Airstream realized they had a problem on their hands and added a drain tube in the same area I drilled holes in my Argosy. The only difference is since there was now a wood floor they had to use a tube and hose to get the water out of the window channels.
After hearing Martins thoughts on why the weep holes don't drain well I now feel the size of the tube and hose Airstream installed isn't large enough to do the job properly. I'm curious as to how many later Classic owners still have water drainage issues with the cockpit windows. The problem would manifest itself by the presence of rotted cockpit floors.
So to sum things up, for the moment at least, the 74-76 Argosies have a cockpit drainage problem that is easily corrected by drilling holes in the channel as shown in my sketch.
For 77-78 Argosies and possibly some early Classics a drain tube will need to be added which requires partial removal of the inner wall skin to gain access. A drain tube of about 5/16" or 3/8" needs to be added to get the water to drain down and away from the floor.
On Classics that have the drain tubes you need to make sure the tube isn't plugged and if possible you might want to consider enlarging the size of the tube as well.