The Tomahawk: This is a sport-scale model of the Surface-Launched Cruise Missile (SLCM) used by the US Navy, painted in colorful red-white-blue that was probably for marketing but not very likely used on the missiles used in service. I believe that this model is not to-scale as it appears to be a bit too long and has smaller wings and a smaller air intake so that this model will fly well as a rocket. It also doesn't usually explode at the end of its flight like the real thing (one would hope).
The view here shows the newer (but now obsolete) configuration, with the added payload section just past the nose of the rocket. It is clear what was added because of the duplicated decal pattern. It may look funny, but it was plain white and I had to do something with it!
BUILDING:
The air-intake is made from a light cardboard. I considered re-making this out of a thin balsa wood, but figured it was unlikely to get damaged during flight because of its location. As it happened, I pressed a little too gingerly on the rocket while applying decals, and bent it a bit. It returned to shape, but not before it cracked the white gloss finish on it. The cracks are not very noticeable on the photo. If you build this model, I suggest soaking the folds of the cardboard with CA glue to harden them. Mine started to split while handling the rocket while sanding the finish.
The air-intake is made from a light cardboard. I considered re-making this out of a thin balsa wood, but figured it was unlikely to get damaged during flight because of its location. As it happened, I pressed a little too gingerly on the rocket while applying decals, and bent it a bit. It returned to shape, but not before it cracked the white gloss finish on it. The cracks are not very noticeable on the photo. If you build this model, I suggest soaking the folds of the cardboard with CA glue to harden them. Mine started to split while handling the rocket while sanding the finish.
This view shows the "stock" configuration. You may notice I tapered the launch lugs on this model; partly for cosmetic reasons, and partly because it might reduce air drag, but I don't know that it's been scientifically proven. The air-intake adds drag I'm sure, but I am banking on it not being that much of a problem, so I didn't go through with my thoughts of providing vent holes on the back of the scoop, which would make the model look a bit odd and would not entirely reduce the drag anyway. We'll just have to see if this model can hit the 600 foot apogee as claimed by Quest.
FINISHING:
The color difference in the blue Testors paint and the decal's blue shade doesn't look too bad in this photo, but in person you will be able to see the shade difference easily. Take a close look behind the air-intake where the square panel decal is. Behind that there was a gap in the blue decal which I covered with the blue from a second set of Quest decals. Even in this photo, you can see the obvious shade difference between the two blues of the decal sheets from Quest. The purple-ish square is from a set of Quest decals I didn't use. If you build this kit, I wish you the best of luck getting the paint and decal shades to match, but don't count on it.
The color difference in the blue Testors paint and the decal's blue shade doesn't look too bad in this photo, but in person you will be able to see the shade difference easily. Take a close look behind the air-intake where the square panel decal is. Behind that there was a gap in the blue decal which I covered with the blue from a second set of Quest decals. Even in this photo, you can see the obvious shade difference between the two blues of the decal sheets from Quest. The purple-ish square is from a set of Quest decals I didn't use. If you build this kit, I wish you the best of luck getting the paint and decal shades to match, but don't count on it.
Quest's instructions do not tell you where to place all the decals. You have to get a little creative. Also, the geometry of the rocket and decals does not match, so you will have to be careful and flexible when applying them. The locations of the decals and the air-intake, wings and other features do not line up as shown in the illustrations (which don't exactly match themselves!). I used Testors spray paints. The red came out as a very close shade to the decal shade, but the blue was pretty far off the mark. I had a second set of decals from Quest, and the blue on the decals looked quite a bit different than the blue decals I used on this rocket. I think color matching the decals and the paint will probably be something of a crap-shoot.
Here is a view of the left and right sides in the original configuration.
Sadly, I also applied a clear-coat on top of the decals to protect them. This was also Testors brand, the same as all the paint. Perhaps I sprayed it on too thick, but even though the decals had several days to dry, the clear-coat seemed to soak in to the decals and wrinkle them all up (after the photographs at least). So while this model looks good from a distance at launch, up close it's more like a wrinkled old man.
FLIGHT TESTS:
As expected, this model didn't perform close to Quest's prediction. In light winds with a C6-3, it reached 492 feet, on a B6-4 it only reached 132 feet. Flights were made with an Altimeter 2 inside clipped to the nosecone. In spite of the altitudes, the flights went very well and were quite satisfying; I expect to be flying this model a lot. This model has flown higher than the Saturn V Apollo spacecraft, and the Milwaukee City Hall Building.
As expected, this model didn't perform close to Quest's prediction. In light winds with a C6-3, it reached 492 feet, on a B6-4 it only reached 132 feet. Flights were made with an Altimeter 2 inside clipped to the nosecone. In spite of the altitudes, the flights went very well and were quite satisfying; I expect to be flying this model a lot. This model has flown higher than the Saturn V Apollo spacecraft, and the Milwaukee City Hall Building.
I never got to fly it with this modification. I was concerned that the added length and especially the added weight would make this too heavy for even the C6-3 motor. It also looks pretty stupid the way I painted the payload. Luckily, while beginning construction of a Quest Harpoon, I had an inspiration. The hollow plastic nosecone was used as the payload section to house the altimeter. This is the same part as used on the Tomahawk. I had much difficulty designing this feature, as normal glues don't adhere to the plastic, even plastic cement and CA glue. I did discover almost accidentaly that hot glue bonds very well to this plastic, so I was able to construct a small compartment with a secure door. The Tomahawk SLCM is being outfitted with this design also, so other than a little weight of the compartment, performance should be very close.
SPECIFICATIONS
Serial Number: 22
Number of Stages: 1
Stock Length: 19.25"
Payload Length (obsolete payload section): 5.25"
Total Length with payload: 24.5"
Diameter: 1.575"
Payload Internal Diameter: 1.56"
Payload Internal Length: 2.875"
Payload Volume: 5.46 cubic inches
Wing Circle Span: 5.75"
Tail Fin Circle Span: 3.7"
Stock Empty Weight: 95.7 grams
Iris Payload Weight: 24.5 grams
Total Empty Weight: 120.2 grams
Liftoff Weight Range: 145.9 - 151.1 grams
Motor Diameter: 18mm
Motor Length: 70mm
Motor Retention Method: Clip
Altimeter Capable: Yes
Recovery Method: 16" Plastic Parachute
Typical Descent Speed: 9 mph
Recovery Protection Method: Nomex 6"x6"
Shock Cord Elastic Length: 21"
Shock Cord Mount: Kevlar
Nose weight: 14.7 grams of clay
Number of Fins: 4
Number of Wings: 2
Fin Material: Paper Laminated Balsa Wood
Launch Lug Size: 1/8"
Kit Brand: Quest
Completed: Nov. 19, 2011
FLIGHT LOG
2011, December 4: Penn Manor, Steady 10 mph wind
B6-4: First ever flight for this model. I thought I was a little careless sending it up in the 10 mph winds on a minimum power motor - It just doesn't look like it can fly that well (looks aren't everything). The B6 burned for 0.9 seconds and pushed this light model to a peak acceleration of 16.4 Gs, averaging 3.1 for the burn. In this time it hit 57 mph before coasting for 3.1 seconds while arcing to horizontal to an apogee of 132 feet, looking very much like a real cruise missile heading towards its target.
1.4 seconds later as it descended to 94 feet it deployed the chute and came down at 9 mph. Flight time was 11.6 seconds.
Another successful first flight! This flight had that un-explainable "great flight" quality to it that can't be seen in the numbers.
C6-3: Since the maiden voyage went so well, this model got an extra flight using a higher power C6-3. Acceleration was only about 3/4 as much, peaking at 12.5 but averaging only 1.8 Gs. I could see this model fighting off the winds as it wobbled a couple of times during the 2.3 second burn, yet it still continued straight up, reaching a speed of 90 mph.
Then in a long, beautiful arc it coasted for 2.9 seconds before ejection a tad early at 321 feet. It still reached an apogee of 389 feet before the chute opened, and then it descended at 7 mph, landing 33 seconds after launch. A very good flight and a highly recommended model to fly!
2012, March 18: Penn Manor, Moderate wind
C6-5: The Tomahawk flew well with a C6-3 in stronger winds, but in light winds it was even better. This time I used a C6-5, and it burned for 2 seconds, accelerating at 7Gs peak, 2.3Gs average. It reached a speed of 100 mph and coasted up for an additional 4.4 seconds to an altitude of 459 feet.
The ejection charge was 1/2 second early, and it apogeed 1/10 second later 33 feet higher at 492 feet. It then descended under a good chute at 9 mph for a total flight time of 39.7 seconds. It landed apx 300 feet away, a total success.
Unusually, I mounted this rocket upwind of the launch rail to get a better angle for photography. Video analysis showed that as it lifted off the 4' rod, it rotated around 180 degrees to the downwind side before it left the rail. It continued its rotation after it left the rod until it was out of the video frame. Normally I position the rocket downwind of the rod to prevent this. The $100 question is: Does this spin hurt the performance (altitude/speed) or does the slow rotation help with stability? This is science fair project stuff, but not for me - I'm too old. Maybe your kids?
2012, May 6: Penn Manor, light wind
B6-4: 144’ Last flight of the day. I was being pressured into making a quick last flight because the club wanted to pack up for the day. I abandoned my plans to launch a more complex composite-motor flight or a 2-stage flight, and instead opted for a simple flight with a reliable rocket that has historically flown well in any conditions: The Quest Tommy. It flies in any winds and does not travel too far up. The wide body makes packing a parachute easy, and with a Nomex sheet inside it doesn't even need wadding.
After ignition the rocket accelerated at 13.5 Gs, averaging 3.3Gs for the 0.8 second burn. It was traveling at 60 mph and coasted for 2.7 seconds to an apogee of 144 feet in a wide arc. 1.1 seconds after apogee, having descended 25 feet, ejection fired and the parachute opened cleanly.
It settled to the ground at 8 mph to within 100 feet of the launch pad. The flight was over after 20.2 seconds. Perfect success.
More importantly, I ended the day's flying with 6/6 opened parachutes, compared to last month's flying where I had six parachute failures! (The 2-stage wreck had a streamer - ha!)
A side note: Analyzing the flight video showed that this model spins fairly quickly during boost, that may be what helps it fly straight up in wind, but it may also reduce its peak altitude. I don’t plan on correcting this characteristic, but I will continue to monitor it in future flights.
2012, June 10: Halifax, near calm
C6-5: I wanted to give this rocket one more test flight on a C6. It did seem to be the best motor for this model, but a third flight would nail that assumption down. I expected in light winds the rocket’s flight path would remain vertical and not turn to the wind as it always has done (and like a cruise missile would do anyway).
This flight peaked at 12 Gs, heading up quickly. The motor burned for 1.9 seconds with an average acceleration of 2.7 Gs. It reached a speed of 111 mph – a new record for this model. Even with very little wind this model curved over and started flying more horizontal than up. After 4.5 seconds of delay (another short delay time!!) the ejection fired at 290 feet, still moving quite fast. It reached its apogee 1/10 second later at 338 feet.
The Quest Tomahawk SLCM is now the Tomahawk SLCM Iris! The (long awaited) addition of a payload bay is complete. Since I couldn’t find an off-the-shelf coupler or bulkhead for this odd sized T40 body tube (Quest doesn’t offer one, and Quest has their own unique tube sizes not supported by third party suppliers), I had to turn my own from a block of balsa. It came out a little off, but useable. Also, I did not get the white shade of paint right, and I used the backup-set of decals which are not exactly the same color shades. Also, I did not clearcoat it to prevent the wrinkles I got on the main rocket, so the looks do suffer a bit when observed up close.
Iris adds a lot of weight – over 20 grams – and length to the rocket. Like my older X-15 model, Since I already flew this model and collected a bunch of flight data already, this will be an interesting experiment to see how the Iris addition affects the rockets flight, in terms of speed, altitude and the general trajectory. My worry is that I won’t be able to fly it with a B6 motor to beyond 100 feet.
My gut feel is that performance will suffer significantly with the added weight and length. I have come up with an alternate plan for this rocket. I may just remove the payload section without ever flying it, and instead carry the altimeter in the hollow nose cone. I am currently working on another Quest kit (the "Harpoon") which uses the same nosecone as this model. Not wanting to increase the length of the Harpoon, I am building a custom holder inside the hollow nose cone and using a small plastic door to keep it in there safely. If this works OK, I will do this to the Tomahawk also. It promises to be a lot lighter and eliminates the added length of body tube and bulkhead. Frankly, I think the added Iris section on this previously sharp-looking rocket makes it look pretty stupid, and I would like to get rid of it!
The plan described above is being implemented! The Tomahawk will now fly without the payload section I laborously added to the rocket.
2013, August 31: Fort Indiantown Gap, 5 mph winds, 86 degrees
B6-4: I made a slight modification to this rocket by installing an altimeter compartment into the nose cone, and not using an extended body tube/payload section that was much heavier. Performance is expected
to be about the same as before, but I thought I would test it with both lower and higher power motors anyways.
This flight began with a motor burn pushing it off the pad at 8 Gs, strangely a lot less than normally. With a burn time of 8/10 seconds, it averaged 2.9 Gs which was normal. This got the rocket to a weak 50 mph top speed, and then it coasted for 2.3 seconds to an apogee of 112 feet. After turning over, another 9/10 seconds passed before the ejection fired 8/10 seconds too late. In this time it dropped only 18 feet.
The 14 inch parachute took over and helped it to the ground at 10 mph - a bit faster than the old Quest-supplied 'chute. It landed maybe only 50 feet away from the pad, and almost on top of me. Flight time was only 9.8 seconds - the fastest ever. Both the apogee and speed were also the lowest ever for this rocket, but still, it came back undamaged.
This flight landed so close to me that I couldn't fit
the whole rocket & parachute in the frame with my long lens!
C6-5: So I tried the low-power for this rocket, now to test the high-power with the new nosecone altimeter compartment. I was expecting about 400 feet from this flight.
As the burning propellant began spewing out the nozzle, this rocket lifted off the rod at 5.6 Gs acceleration. The motor burned for 2.2 seconds and it pushed the rocket to 96 mph with a average acceleration of 2 Gs.
Compared to the three previous C6 flights, this was all normal although the burn time was a bit long.
It began turning as this rocket always seems to do, and coasted for 3.8 seconds. At that time it reached an apogee of 430 feet. Another second later the ejection fired after it fell only 16 feet. The ejection was close - only 2/10 seconds early. It was now at 414 feet and the parachute un-reefed to bring it back to earth at 10 mph. It landed about 600 feet upwind (while the previous flight went downwind).
Again, this rocket seems to always pick a random direction to travel regardless of the wind direction. I suppose it has to do with the internal guidance system being programmed for a specific target...now THATS a scale-model feature!
No comments:
Post a Comment