Level 3 Project
The Design
As mentioned earlier I have decided to go with an upscale BSD Thor. To what degree did I want to upscale it was the first question. At first I just primarily wanted to build something large, that was K and L flight capable. When I got to looking at prices for larger airframes and materials I figured I might as well go for my Level 3 cert at the same time and kill two birds with one stone.
With that primary objective I decided to go with a 6" diameter upscale. This leaves me with an easy 1.5 multiplier when designing.
The other major decision was with what size motor mount to use. Everyone knows that you can always adapt down, but this time I'm going to back away from that principle. I want to use this bird for the dual purpose of certifying Level 3 but it's main purpose will be flying. I can't afford 98mm motors and will probably rarely fly it on 75mm M motors. So I decided to go with a 75mm mount which would be more easily adapted down to 54mm for high impulse K and some L motors. I still have a small selection available of M reloads from CTI, AT, and AMW that I can choose from for the occasional M flights.
The rocket will be 127" in length, 6" in diameter, and weigh in at about 24 to 26lbs without the motor. Easily flyable on high impulse K, all the way up through the smaller M motors which is what I wanted.
The rocket will be double walled internally the entire length with Giant Leap phenolic couplers, as well as externally fiberglassed with 9.7 oz Aerosleeves the entire length of each body tube. It will then receive an additional layer of 6oz glass over the fin can area for tip to tip glassing of the fins. Lastly a veil layer of 3 oz glass will be applied over the entire length for finishing.
The avionics bay will be similar to the bays I made for both my Mach1 and BSD 38 Special Rockets, only on a much heavier scale.
At this time I am happy with the general design as it will accomplish all of my objectives, low impulse M flights will be kept under 10k' and still be able to fly on both K and L motors.
Parts will be from BSD, PML, Aerosleeves, and Giant Leap.
After about 5 design revisions, this is the zipperless design I'm going to go with. Originally it was a completely "scale" upscale of my 4" kit. Now it has been changed and modified to incorporate a zipperless design of the booster section. It's hard to see in this rocksim image but this is the current and final design.
The picture above is confusing, with that many components and inner workings it's hard to keep things straight. The following pictures should make things clearer.
External Airframe Dimensions and overall dimensions.
Above are the external dimensions of the different airframe tubes. Over all dimensions are 127" in length, (10 feet 7 inches) and 6" in diameter weight is 30lbs without motor.
From bottom to top, booster section is 43", drogue compartment tube 20", avionics bay tube 3", main payload bay 37" and nosecone 24".
Internal dimensions and Compartment details.
Here are the internal compartment dimensions. Couplers are gray in color, centering rings and bulkheads orange.
Avionics bay is held together with 3 pieces of 5/16" allthread. There is an extra bulkhead in the middle of the avionics bay to lessen the amount of volume that has to pressurized for altimeter readings.
5/16" allthread runs from the upper fin centering rings to the zipperless design bulkhead at the top of the booster, these are to help hold/retain that bulkhead that has the recovery system u-bolt in it, so that epoxy isn't the only thing the system is relying on.
Recovery details.
Recovery will be dual deployed. Drogue at apogee, either a R3C or R4C connected to u-bolts via quick links and 40 feet of 1/2" tubular kevlar and 9/16"tubular nylon. Main will be a Rocketman R16C connected to u bolt and nosecone via quick links and 30 feet of 1/2" tubular kevlar and 9/16" tubular kevlar. Recovery ejections will be handled via dual RRC2 altimeters from the avionics bay.
Component details.
Component details are labeled above, in short they consist of 1/2" birch ply for centering rings and bulkplates, 5/16" all thread as needed, 5/16" U-bolts for recovery connections, 8-32 blind nuts for motor retention.
Airframe is Giant Leap non brittle phenolic and couplers are Giant Leap phenolic, nosecone is a 6" PML fiberglass cone.
Adhesion details.
All adhesion was done with Aeropoxy, straight for laminating, with milled fiberglass for all other adhesion.