If you are making one for yourself you shouldn't be worried about someone coming after you. If you plan on selling kits you need to be careful. I don't know the details, but Randy at eRockets/Semroc has contacted Estes about making OOP kits.Hello,
I'm wanting to produce an upscale kit of an old OOP Estes kit. Has anyone ever thought of doing this? If so did you run into any problems or any legal issues.
If you go to page 21 of that thread, you'll see that Carl ended up with an agreement with Estes. So it seems that it is possible (maybe not for everyone always in all situations, but possible in general) to sell kits of Estes designs with full knowledge and approval of Estes. I do not know the terms of the agreement.
tep 1 should be to talk to Estes. Contacting Jumpjet here is one way, or just going straight to Estes corporate is another.