Hi, and thanks for the nice words all, this won't be a sodmeister build, he sort of put the bar out of reach on his very nice hellfire, this is just an attempt to make a very light one
Answers:
Can I have a copy of the ork file, yes in the first post it is attached. I've removed the boat tail for now.
Do I need all those centering rings: They weigh approx 0.1 oz each and are foam, just to support the stringers and skin....the reason there are so many is that I'm using a 2mm skin, the skin tends to flatten out between stringers and I'm hoping that this will give them enough support to stay round...the only wood is the bottom 1/8" thrust plate and the top centering rings and nose plate just because I need to attach the recovery to them.
Nose weight: The plan is to have the weight all the way at the end of the plate that is attached to the coupler in the parachute cup; the coupler will act as the shoulder of the cone, and the weight on top of that, as far forward as I can go.
Progress: I found a great deal on bt-55 tubes and couplers for $6 total, two leftover pml 6" long 3.9" coupler sections for the parachute section for $3 each, and a 29mm motor mount for 4" for $6...that got me all the tubing I needed and three centering rings I could trim down to fit into the couplers to center the tubing and make the nose cone shoulder. I had a spare piece of 38mm tube that I glued to the side of the parachute compartment which will hold the altimeter, there will be a door on the side of the rocket I can open, insert the altimeter from the bottom of the bay, and route the ejection charge through a tube up into the chute compartment. All up weight for all the tubing, coupler and altimeter compartment and altimeter is right at 12.7 oz which is just what I estimated, so far so good. Most expensive piece was the aeropack retainer....Foam cost was $55.The center tube will act as backup motor ejection and give extra support to the structure, and tie the whole thing together under recover and flight load. BT-55's were dirt cheap. You'll see a ring around the parachute compartment. I was only able to find the pml couplers. So I cut 1" off of one of them, and then cut the rest in two 3” long pieces. I spliced one of the 3" pieces to the parachute compartment, and then split the 1" ring and glued it on the outside to support it, so I would up with a 10" chute compartment. I then split the other 3" piece and trimmed a section out and re-glued it back together with the cut out piece on the inside to make the perfect fitting shoulder to go inside.....It also turned out the bt-55 coupler fit exactly around the 29mm motor tube to center it in the rear. I used the rest of the 29mm motor tube in the forward end of the bt-55 tube because it already fit the ply centering rings that came with the motor mount from sunward.
parts used:
3 18" lengths of bt-55
5 bt55 couplers
one 29mm motor mount for 3.9" tubing
two 7" long pml 3,9" couplers
one piece of 38mm motor tube.
small aluminum tube to route the ejection charge from the bottom into the parachute well.
Frank
Very cool... Always been a fan of the Hellfire design. Definitely a different shape than the standard 3FNC rocket. Stubby, round nose, small fin diameter... Very cool.
I'm curious, Do you really need all those centering rings? Also, you mention the probable need for nose weight, have you thought about adding some weight in between some of those bulkheads?
Finally... If you're willing to share, I'd love to get a copy of the file so I could do maybe a 1/2" scale! Been looking for a scratch project!
