Some notes about the materials and parts listed above before I start the assembly photos / comments.
Although the airframe components (body tubes, nosecone and fins) are from Madcow, I replaced or added everything else. I used my Shapoko 3 CNC router to fabricate 56 parts for this rocket. This took me quite a few months since I was only able to dedicate some time on the weekends for most of the past year or so. I spent a lot of time designing and trying out parts in cheaper materials such as plywood before committing the designs to aluminum and fiberglass. While the kit Madcow sells is a great kit and has most of the parts you would need to complete a build like this, since I got this CNC router, I tend to buy the kits as a convenient way to get the bulk parts. A lot of discussion in these forums revolves around using a kit or "scratch" building. I have found that, even if you have a scratch built design or aspirations, you can find many of the parts you want much cheaper in a kit. In this case, the normal price Madcow sells this kit for is already a modest cost savings over buying the component parts individually, but I got the kit on their last Black Friday sale for 30% off, which also meant about 40% off buying the component parts separately. So, even though I had planned from the beginning to ditch many of the parts and make my own, it was worth it to plan ahead and buy the kit on sale just to get the bigger airframe parts. As a bonus, you don't have to slot your own airframe! Another thing to consider is that the individual components are often not available. As I write this, Madcow currently shows this kit as available for purchase, but the 8" airframes, the 8" nosecone, the 4" motor mount and the 8" couplers are all out of stock. So, if you wanted to build an 8" scratch rocket right now, buying this kit would probably be one of your only ways of getting the parts from Madcow at the moment.
The CR's I made have slots for both upper fin guides and lower glue wells, (the spanners for which were also CNCed) and also have holes for all-thread which will be used primarily for adjusting the CRs precisely, but also add some structural value.
I CNCed all the bulkheads, mostly out of aluminum, but one BH in the noscone bay is fiberglass.
The ebay parts include a simple FG sled, a switch bracket CNCed from 3/4" basswood and a number of fiberglass parts and brakcets.
I will go over the recovery system in another post, but I spent considerable time talking with my TAPs about the various strengths and forces that each component would be subject to in a worst case scenario and bought or built the components with those discussions in mind. To that end, the u-bolts used are 3/8" thick from McMaster-Carr and are rated for thousands of pounds. Likewise, all the quick-links used that will be subject to the weight of the rocket are also 3/8" thick from McMaster-Carr and are rated for 3900 pounds each. The bridle and shock cords are all custom made by Teddy from Onebadhawk and are all rated for over 5000 pounds. The Cert 3 XXL parachute is more than adequate for this rocket, but only came with a 1500 pound rated swivel. While the cert flight is designed to be low and slow, so will unlikely generate velocities that will exceed the capability of that swivel, I would like this rocket to fly on bigger motors later, so I had Teddy also replace that swivel with a length of kevlar and a 5,000 pound rated swivel.
The all-thread in the ebay has to hold up the weight of the entire booster section as well as absorb the shock of the various events, so I used 4 lengths of high strength steel 5/16-18 all-thread from McMaster-Carr each rated for 150,000 PSI.
The thrust plate is 1/4" aluminum CNCed to attach the Aeropack 98mm retainer. The holes were all threaded for the screws so the retainer housing can be bolted directly to the thrust plate. Normally, I do this so I can remove the housing and use it on multiple rockets, but since this is my cert bird, I am going to be permanently affixing those screws and the housing to the thrust plate.
All the components were washed and sanded thoroughly inside and out with 220 grit sand paper and washed again numerous times. For anyone that has not built one of these bigger rockets, I would invest in some decent equipment for sanding and finishing. Basically, look for the same tools auto body workers use to work on cars. A good random orbital sander and a good size package of sanding discs seems like a must. There has been a lot of sanding. Also not sure how anyone builds anything without a Dremel tool handy, but I would have been lost 100 times on this build without my Dremel.
I am using a variety of epoxies in this build - West Systems 105/205 is the workhorse, sometimes mixed with their 405 Colloidal Silica when I need to thicken it up. Proline 4500, JB Weld and RocketPoxy will also make an appearance. For 5-minute epoxy needs, I am using both JB Weld Clear Weld and West Systems G5 - literally, whichever of the two is close at hand when I need it. I very sincerely do not want to make this a glue thread, so I am not advocating these epoxies at all - just listing them because people usually want to know, so may as well answer the question up front.
Here are some photos of the CNC process and some of the components. Note, in the photos here, the wood parts shown were all test pieces I used to make sure my designs were correct. After everything was fabricated, sanded, washed and tested, I dry fit everything countless times to make sure I had things right.
The sled is 5" wide and 16" long. It is a gigantic platform for electronics. The RRC3 and SLCF will look tiny on here.
Dry fit of the MMT assembly:
