The Bertha is an outgrowth of the Ranger. The Ranger was, as noted, a payload rocket, and it had the cluster mount as a way to lift modest payloads when only 18mm motors were available. The design was then simplified a little later to create the Big Bertha. I strongly suspect that although the fins may be marginally different, a lot of that was probably the result of cutting variation from model to model, since the early versions required the builder trace out and cut out their fins on sheet stock. I'd bet that they probably were intended to be the same, but just evolved through iteration. Another note along those lines, the Ranger (and early Bertha) used a BNC-60L nose cone. That was changed, and the modern Bertha uses a PNC-60M. Purists would have to have the original cone, not only because its balsa (which to me is inconsequential after its painted), but there is a visual difference in the length and shape. The -60L is about an inch longer, which is a lot when the cone is only 3.5" exposed.
So, if you wanted to clone the Ranger from a Bertha reasonably accurately, you need the cluster mount, a structure change to allow the payload compartment, and a replacement nose cone. As I recall, eRockets has Semroc BNC-60L cones, but also have a few PNC-60L molded cones as well.
depends on how close you want your 'clone' to be, I built my 'wannabe' from a Big bertha kit. the additional parts used; a 24mm motor mount(with Estes retainer), a bt60 tube coupler, and an 1/8" plywood bulkhead to close off the tube coupler. I chose to paper the fins. it flies quite well with a 3.5 ounce payload using a D12-5. I also used a 2-56 machine screw to secure the nose cone. recovery uses an 18" thin mill chute.
Mine is similar to RexR's. The only difference is that I didn't have a BT-60 nose block, so I took a JT-60 coupler, and cut two disks of 1/2" foamcore to turn the coupler into a plug. Worked great, and my Ranger flies like a champ!
Fantastic info guys, thanks. I'm constantly amazed at the knowledge that resides on this forum!
My initial interest was in building a cluster motor rocket. Couple that with a bit of a nostalgic streak and a Ranger is a natural. Of course, finding that the original parts are available from Semroc and the accurate fin pattern provided here, my nostalgic bent demands a genuine clone.
Searching eRockets for the proper parts also revealed that Semroc dose sell a Ranger kit. Anyone have any experience with it?
I don't have experience with Semroc's Ranger, but their other offerings are top notch. I am just a satisfied customer. Semroc has done an excellent job with recreating some of the old designs of the past.