Now those are the pics I saw! Awsome build. My b-day is 4/2, which is why I sorta remembered also. 1988/1996, sheesh, I got into rockets with my dad in 92/93 when I was 11 or 12.
On your 'death of a SR-71' was that before you added vents to the kits?
I didn't add the steel heat disks, I will load up a bunch of wadding in the nacells. I am hoping that with friction fit on my C6-0s fit they will self eject. The intake cones have a bunch of CA holding them also.
You listed the stock nose as 15g, and in another pic you list that you added 30.4g. How did you come up with that conclusion if you remember.
Do you remember which rod you used to use? What about getting all three motors to fire? What about your chute, what size/type was it?
I know it's going to be a long walk with D and 2xC. Luckly we launch in the desert with nothing around, and in the mornings there is no wind.
For my first launch I may just run a D and see how it goes.
If I build another one of these I will probably make it 3xC and will add the vents.
The Death of an SR-71 was before adding the pod venting. it was my First Clustered SR-71. I'm now on my 4th. 2 & 3 were litterally warn out by flying. #2 logged 23 flights, burned thru the main body tube at several places on her last flight. #3 logged 27 flights. I reinforece the area around the vents toward the front with Medium CA during construction which seems to help on this model the main motor mount burned thur the BT-50 and shroud..... Guess Nothing lasts forever with that much after burn LOL!!!!
#4 only has a few flights, and was reinforced in the motor mount area with CA as well.
Yes NO matter how tightly you friction fit the pod C's they will Self Eject at burn thru. B6-0's do as well
To return the models CG to it's original postion I added nose weigh that was equal to ALL the added materials, rings, discs, vents etc. and 1/2 the Max. extra motor weight, In my case the mass of a single C6-7, you'll need to add the extra mass difference between C6-5 and D12-5 or 7 as well. Over all for my model these added up to 30.4g. Each of my altered Clustered SR-71's has varied a bit in E-weight because of variences in epoxy used, and other material masses. I feel it is important to get accurate weights of everything before assembly so our added mass numbers comes out correctly. So far each of my 4 have been vary stable in flight even on the windest of days, showing very little of the weathercocking we hear so much about with the unaltered model.
My models have all flown from 1/8" x 36" stainless rods. This model leaves the rod Very fast, I have not had any problem with rod whip or tip off on any flight.
Believe it or not I alway use the Stock 18" Estes plastic chute with my SR-71's I do substitute my own trim monokote silver tape discs for the supplied discs and tie an overhand knot in the end of each shroud line about 1/2" for the end, which is coiled around the disc in a half loop then burnished down under the tape disc with a round end tool to the canopy. As the motor extends well below the wing/fins on this model it takes any part of a hard landing. but the 18" chute seems to bring them down at a gentle enough rate to prevent damage.
Getting all three motors to light is generally not a problem as I ALWAYS use a relay ignition system with a HD 26amp/hr Gelcell at the launcher. Remember the rule of thumb is still 2amps/igniter even with the new Quest Q2g2 igniters. It is also wise to use the heaviest/shortest clip-leads you can manage. May I suggest down loading Tech-Tip 006 "Clustering BP motors" from the Library section of narhams.org. I wrote this tech-tip to answer many of the clustering questions you've just ask. This Tech-Tip will help explain what has to happen in that first split second to make all these things work. The Death of a SR-71 was completely my fault as I did NOT check the igniters for that flight...BEFORE and AFTER installing them in the motors and one last time on the pad. Had I done so I might still be flying SR-71 #1
I wish you luck on recovery, I can't imagin how high it's gonna go with a D12 and a par of C6-7's in the pods. I'm sure it will still be moving UP at a pretty good clip at ejection. For that reason you may want to go with a sawn nylon chute but the Core BT-50 is pretty tight so you may have to reduce the size to say 14"?
Good Luck I hope to hear some interesting flight reports real soon...
Happy Clustering
