My next endeavor in scratch building will be to break Mach, the speed of sound, with a "cardboard" rocket. Meaning no reinforcements from fiberglass or any other fibers.
All tubes will be cardboard, centering rings wood, and fins wood, no G10 or fiberglass allowed. The target motors for this bird are the Pro 54 K445, and the AT K550 both will put this substantially past mach reaching a speed of approximately mach 1.2
3" by 60" with a 54mm motor mount.
Building will begin hopefully January or February of 2005, until then here are some Rocksim images of the rocket. Once building begins I'll update here with build pics.
Here is another with a little more information.
***Build Complete Feb, 2005***
This will be a thorough page with allot of graphics detailing almost every step of the build of this rocket. With the target motors this bird will be pushing nearly 30 G's so I did everything I could to strengthen bonds and the build.
Parts consisted of 3 body tubes, 5", 17", and 26" in length. One 17" 54mm motor tube. Centering rings, Couplers, Bulkhead plates for both body tubes and couplers, nosecone and hardware. All construction was completed with Aeropoxy epoxy.
The first step was to build the motor mount assembly.
The motor tube was roughed up using 150 and 100 grit sandpaper to facilitate a better bond between the motor tube and centering rings.
Next the inside of the 3 centering rings were sanded to fit, they were a little tight which is what I wanted so that I could sand them to the tightness I wanted.
Next the outside of the centering rings were sanded to fit the inside of the body tube. Also a notch was made in both the top and middle centering rings for applying the shock cord attachment later.
The fit was then tested with the booster tube.
The rear centering ring was then marked for the installation of 3 t-nuts for motor retention. Then holes were drilled into the centering ring and the t-nuts installed. The flange on the end of the t-nuts was too wide and overhung on both the inside and outside of the centering ring and had to be ground down to fit.
Next I used a belt sander and beveled the fins, I attempted to knife the fins on all sides for better aerodynamics on supersonic flights.
Next the motor mount was assembled and test fit. You can see the t-nut on the bottom centering ring here. After I was satisfied with the fit, the fins were attached using a BSD fin alignment guide with medium CA to tack them on.
Now the middle centering ring and bottom centering rings were applied snug up to the fins. I used a piece of wax paper between the rear centering ring and fins to keep from attaching it to the motor tube so that internal filets could be applied later between the fins and the body tube. Aeropoxy with milled fiberglass was then applied for filets from the fins to the motor tube.
After all the fillets had been applied and had set, I then epoxied in the top and middle, centering rings. The top centering ring was then sanded down more so that it would fit inside a coupler tube.
A piece of 1/4" tubular kevlar was then epoxied to the fin can unit running through the notches in the top and middle centering rings.
Next I took the three pieces of body tube and again using the BSD fin alignment guide marked each piece for 3 fins. The marks would be used for cutting out the fin slots on the booster tube, and for drilling vent holes for the altimeter, holes for the plastic rivets, and shear pins.
Next fin slots were cut into the booster tube.
The fin can was then test fit. I generally cut fin slots a little large knowing the epoxy will fill in the excess hole. After I was satisfied with the fit and very careful measuring I installed couplers inside the booster tube so that it is double walled all the way down to the middle centering ring. Space was left so that the middle centering ring would be epoxied to the actual body tube.
Next the fin can was installed into the body tube. The top and bottom of the middle centering ring was coated with epoxy, the top of the upper centering ring was also coated with epoxy. Later upon installing the bottom centering ring it is also coated with epoxy both top and bottom sides. The design is for the majority of stress to be handled by the middle and bottom centering rings, and also the joints between the fins and the body tube.
After this had all set it was time for internal fillets between the fins and the body tube. This was a little tricky with the minimal amount of room left inside the body tube.
After the internal fillets had set I then took each fin and drilled 5 1/16" holes about 3/4 of the way into each fin. These were placed down each fin near the body tube. This was done to form epoxy nails into the fins when the external filets were made, hopefully for a little more strength.
External filets were then applied between the fins and the body tube. Again done with Aeropoxy with milled fiberglass.
While these dried I installed the rear centering ring and then began construction of the electronics bay. The design is simple. One 5" piece of body tube, two 6" coupler tubes, 2 coupler bulkheads, 2 body tube bulkheads, 2 U-bolts, one piece of 1/4" all thread and one key switch.
The two coupler tubes were centered in the body tube, leaving 3.5" of coupler tube exposed on either end. The section of coupler tubes has holes drilled into it to accept plastic rivets to secure the payload bay to this coupler.
Bulkheads were made by joining the coupler and body tube bulkheads together, a hole was drilled in the center of each bulkhead for the all thread to run through, and then two holes were drilled for each u-bolt, one on each end of the bay.
Wiring was run and soldered to the key switch and to the terminal blocks. Washers were used on the undersides of the u-bolts, since this is the side that would have deployment forces pulling from. They were also epoxied in place. The bottom side of the bay was fixed in place by epoxying the coupler to the body tube and by also epoxying the bottom bulkhead assembly in place, this would help keep any ejection gases from the drogue deployment from getting up into the bay.
The external filets are now dried and ready for sanding and shaping.
A little sanding with the dremel tools and the filets are more acceptable. Now for some filler above the fins where the dremel got a little too carried away.
Body tube is now filled and sanded and ready for final sanding of the filets, body tube, and fins.
Next using the lines that were marked on the body tubes earlier, 3 holes were drilled into the bottom of the payload bay for plastic rivets to secure it to the avionics bay. Vent holes were drilled into the payload bay and into the booster section to alleviate pressure buildup during flight. Rail buttons were also added.
The same was done at the top of the payload bay to secure the nosecone via shear pins. I did something a little different this time in that I installed flat pieces of aluminum into the body tube where the holes were to go. This way the aluminum could assist in shearing the pins without elongating the holes in the body tube.
All holes were soaked with thin CA to keep strengthen and keep them clean. All body tube ends were soaked with thin CA again to help strengthen. The bottom of the booster section tube is double walled with coupler tube below the fins and then coated with epoxy.
Here it is complete and waiting for paint, which should come later this week or early next week. I was going to try to get a professional paint job done on this one but now looks like I'll be having to paint it myself.
Complete with paint and decals waiting for first flight. Decals I had made locally I also used a leftover BSD decal as the majority of the parts are BSD components.
Built February 2005
***Update***
First flight complete 3/19/05 with Thor in Nebraska.
We had a little wind early in the day so we opted for a shakedown flight instead of the full K flight for the maiden flight.
Here she is ready to go, loaded with an AT I284 white lightening motor. Setup for drogueless at apogee and a 45" main at 500' controlled by the RRC2 altimeter.
And up she goes, gotta love those white lightning motors. A great shakedown flight to 4,281' at 484 mph.
8-06-05 at Walcott, Ia under boost from an AT K695 Redline motor...
About 2 seconds into the 2.3 second burn of the K695 things came apart. Appears the ebay coupler may have failed, but still under investigation, it will be rebuilt this winter.
Note the bent allthread that was going through the avionics bay.
Complete details on the 8-6-05 launch page under the launches link.
Flight video shows that the motor came up to pressure and the rocket started up the rail at 50.19 seconds, it started to come apart at 52.21 seconds. As you can see by the sim that has had the CD adjusted to match this rocket that we were right at maximum airspeed or just a hair past it at 2 seconds into the burn.
Diameter 3", Length 60.5", Weight around 60 oz. 54mm motor and Dual deployment recovery.
The Rebuild Jan/Feb 2006
Well I still believe in the project so I had planned since last summer to rebuild and try again. From the original I salvaged the nosecone, and possible could have salvaged the fins, but instead ordered a new set from Big Head Pete Fins Inc., where I got a great set of matched fins.
With BSD somewhat disappearing and in the middle of an ownership change this time I went with LOC parts and components.
The fins installed into the booster section and internal fillets complete. You can see here the multiple 1/16" holes in the body tube and in the fin near the root, this is to give the epoxy something better to grip into.
This rebuild was completed exclusively with AeroPoxy epoxy.
All the parts complete and ready for final details before paint. You can see the original cone that I'm still using, the biggest difference in the build this time is that it is fully double walled all the way up to the cone this time, and then the new avionics bay. This time I went with a Loc extended 3" alt bay. One piece of coupler instead of two, as well as a stiffy tube inside the coupler assembly to assist in stiffness and overall strength. This being where I believe the failure was last time, I think this time we're plenty strong and good to go. Otherwise the rest of the build is essentially the same as last time.
All the holes have now been drilled and reinforced by wicking thin CA into them. 3 holes for the shear pins from the booster section into the alt bay coupler, three holes for the plastic rivets from the top payload bay into the alt bay coupler, and 3 holes into the nosecone through the top of the payload bay for shear pins. 2 holes for vent holes 1 in both the booster section and payload bays.
Here a little touchup is being done with SuperFil on the fillets.
And here we are complete with paint and decals ready for another go round. I'm stoked about the rebuild and think it's going to be good to go, may even purposely target the K695R again for the attempt.