I have the LOC 7.5" Doorknob and love it. I completed my L2 with it on an Aerotech J350 (low and slow) and also flown it on a K535 which got it moving nicely. I'd just been using single altimeter based deployment and used a chute release, but on the last flight I narrowly escaped disaster from a tangled chute (complicated by the chute release and my poor preparation). The flight landed perfectly fine, but it was a nail biter waiting for the chute to fully inflate, which it did about 50 feet from the ground.
Ever since then I've wanted to make this a true dual deploy. I also have noticed that the overall length of the rocket is a bit short for the diameter (compared to the scale drawings in Peter Alway's Rockets of the World supplement). The overall length built stock from LOC is 64". Given the diameter of this rocket compared to the original, I calculated a 48.4" scale factor. The real rocket is 143" (not including the probe extending from the nose) so a more scale-like length would be 69.2".
So I ordered the LOC 7.5" avbay kit and a fresh section of 7.5" airframe. My plan is to replace the original 12" upper airframe with a section cut to 17.2". I built my kit originally with the coupler between the upper and lower airframe acting as the separation point for chute deployment, so it is going to be a simple matter of building the new 17.2" section of airframe the same way, but with the addition of the avbay.
Here is the complete stack in the original configuration, and with the nose cone and old upper airframe sitting on the bench.
This airframe was fiberglassed when I first built it, so I repeated the process for the new section of airframe (subject of another thread of mine describing the soller composite sock method). I added a coupler to the bottom of the new airframe section to duplicate the original. Inside this, I glued the stiffy coupler to form the shoulders to capture the av-bay. I made this part of the assembly permanent.
Here are the old and the new upper aiframe sections side by side. Of course, I still need to paint this, but Michigan weather has been way too cold lately, even with the torpedo heater running in the garage (can't paint this in the basement).
I assembled a Missile Works RRC3, RRC2L, and an RTx/GPS unit on the LOC avbay sled. I used my usual technique of copper pipe and caps for charge wells, but decided I'd recess them through holes in the bulkhead to save space on the parachute sides of the bulkheads.
I 3d printed a dual screw switch holder/guide with mounting holes from top to bottom as well to allow the switch guide to be used to bolt the assembly to the avbay sled. The screw switches are from Missile Works and the switch guide I made is basically a "borrowed" design from the guides available from them as well (just without being a double and having avbay mounting provisions).
The only other thing I did was to make a hardwood guide to epoxy into the inside of the avbay and installed a guide pin on the upper bulkhead so that the screw switches wind up perfectly aligned with the holes in the airframe.
Here it is all stacked up! Just need to paint it once we get a warm snap in the weather. I'll be using the same paint I used on the original build: Rustoleum oil based paint (gloss white and Allis-Chalmers orange) sprayed through an HVLP gun. The horizontal stripes on the original are trim monokote (chrome and black). I'm hoping to fly it at Three Oaks this year on an L1000, which will be my largest motor flown to date.
Ever since then I've wanted to make this a true dual deploy. I also have noticed that the overall length of the rocket is a bit short for the diameter (compared to the scale drawings in Peter Alway's Rockets of the World supplement). The overall length built stock from LOC is 64". Given the diameter of this rocket compared to the original, I calculated a 48.4" scale factor. The real rocket is 143" (not including the probe extending from the nose) so a more scale-like length would be 69.2".
So I ordered the LOC 7.5" avbay kit and a fresh section of 7.5" airframe. My plan is to replace the original 12" upper airframe with a section cut to 17.2". I built my kit originally with the coupler between the upper and lower airframe acting as the separation point for chute deployment, so it is going to be a simple matter of building the new 17.2" section of airframe the same way, but with the addition of the avbay.
Here is the complete stack in the original configuration, and with the nose cone and old upper airframe sitting on the bench.
This airframe was fiberglassed when I first built it, so I repeated the process for the new section of airframe (subject of another thread of mine describing the soller composite sock method). I added a coupler to the bottom of the new airframe section to duplicate the original. Inside this, I glued the stiffy coupler to form the shoulders to capture the av-bay. I made this part of the assembly permanent.
Here are the old and the new upper aiframe sections side by side. Of course, I still need to paint this, but Michigan weather has been way too cold lately, even with the torpedo heater running in the garage (can't paint this in the basement).
I assembled a Missile Works RRC3, RRC2L, and an RTx/GPS unit on the LOC avbay sled. I used my usual technique of copper pipe and caps for charge wells, but decided I'd recess them through holes in the bulkhead to save space on the parachute sides of the bulkheads.
I 3d printed a dual screw switch holder/guide with mounting holes from top to bottom as well to allow the switch guide to be used to bolt the assembly to the avbay sled. The screw switches are from Missile Works and the switch guide I made is basically a "borrowed" design from the guides available from them as well (just without being a double and having avbay mounting provisions).
The only other thing I did was to make a hardwood guide to epoxy into the inside of the avbay and installed a guide pin on the upper bulkhead so that the screw switches wind up perfectly aligned with the holes in the airframe.
Here it is all stacked up! Just need to paint it once we get a warm snap in the weather. I'll be using the same paint I used on the original build: Rustoleum oil based paint (gloss white and Allis-Chalmers orange) sprayed through an HVLP gun. The horizontal stripes on the original are trim monokote (chrome and black). I'm hoping to fly it at Three Oaks this year on an L1000, which will be my largest motor flown to date.