I dove right into it carving a dome off the 3 dome and following TT's instructions documented in his Modeling the SP blog and the SPH&TS Trainline #71 article ran into the first problem of not having done this before. It took a the rest of the afternoon before I gave up trying to get a smooth join for the dome top from the 3-dome car attached and blended with a smooth joint onto the single dome casting. I tried 4 times to get a smooth invisible joint using Tamiya putty for plastic. Each time I let it dry, sanded it and then shot it with Tamiya grey primer. I let that dry and then tried again to get a smooth invisible joint with more putty and sanding. Then spraying and starting over again.
Today after shopping errands I started at it again. This time I dug out an old tube of Squadron Green putty and went over the dome joint line. After it dried I used a xacto blade to shave off as much putty as I could and sanded again. I use some ACE hardware 600 and 1000 grit paper to try and smooth is as much as possible and then shoot it again with the grey primer.
Well this time the results look a bit better. I have however lost any rivet detail that was on the Athearn casting. I have some Archer resin rivet head sets on hand including the Offset Tank Car double row rivets set to repair as needed. I also have a collection of Tichy tank car detail parts to use as well.
These photos shows my progress on this project, the donor 3 dome and my existing Athearn SP tank car with the incorrect dome. Once I am done with this one the donor will give up another dome for conversion of the existing SP car and then I will try to find one more complete Athearn kit. 3 SP 12,500 gallon tank cars will be enough to fit in with all the smaller tank cars used to service the Martinez area refineries.
A lot more to do. Frame and brake modifications and then I still have to find black late 1940's style tank car decals, do all the railings and grabs.
How old was the donor 3 dome car? The ladder was a metal stamping.