| Manufacturer: | Shadow Composites |
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The Sprint ABM was supposed to be the worlds fastest missile and got so hot the casing had to be ablative. The acceleration was 100+g.
Construction
The model from Shadow Composites (kit #21 and the first in the UK according to the manufacturer) is 1:12 scale and is constructed from two shrouds over a simple motor tube and ring assembly. The inner sheath is Nomex® paper the outer is a fine, glossy, printed card. The construction depends mainly on forming the two shrouds into cones by curling and taping them. This was very hard as the Nomex® shroud was thick and sprung back even from masking tape. I eventually curled this shroud very tightly and used rubber bands, when I released it after about 3 weeks it stayed curled and I was able to work it. The designers had got their math right as, when glued along its edge 'tab', the Nomex® shroud fitted the motor mount centering discs perfectly. To add the outer shroud you use spray glue (3M spray-mount type stuff) and fold the shroud onto the inner. This requires a steady hand and nerves, cos you don't get 2 chances! |
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The shock cord is plaited Kevlar® which looks like a shoe lace and has some elasticity. There is an inner Nomex® reverse cone that goes into the very tail end. I used CA for this and it went in easily. The nose cone is solid bass wood, turned needle sharp. Extra weight in the form of 4 washers is added behind the screw eye, instead of this I weighed the washers etc. then drilled out the nose, filling it with lead shot and epoxy which also anchored a Kevlar® cord loop to connect to the main recovery system. I had seen newsgroup postings suggesting the model was unstable, this mod added about 1oz to the nose, about 1" further forward. To finish the model off as near scale you need to construct the 4 tiny control fins which live half way along the body. I can't get the balsa bases to look smooth enough and curved to fit the body, so I left them off for the time being while I have a think about making fresh ones.
Flight
I flew the Sprint on the only motor stated in the instructions (a D12-3) on a calm day . It seemed to accelerate noticeably as the flight progressed as opposed to the woosh and coast of a normal model. The motor note is hollow and most unusual to fit this very unusual kit. All who have seen it fly (4 times now) are very impressed. This is not a kit for inexperienced modelers.![[NAR]](/images/archive/images/link_nartitle.gif)
![[Sport Rocketry]](/images/archive/images/link_sr_logo.gif){kind=logo}
The following excerpt is from "Sport Rocketry". The intention is to allow guests to get a basic feeling about a kit. We strongly suggest that you get a copy of the referenced Sport Rocketry and read the entire article. Inside you will find many helpful hints in construction as well as other useful information. For more information, use the two links above.
(Sport Rocketry - July/August 2002 - Page 25, 35 - by Jack Hagerty - 12/20/02)
"The Sprint ABM kit from Shadow Composites is a real nostalgia
trip for anyone who remembers the '60s."
"...hand-drawn isometric illustration in the instruction sheet."
"The Sprint kit is deceptively simple with only six major parts: a core
tube, two centering rings, nose cone and a two-piece conical shroud body."
"...extreme care is required when assembling the centering rings to the
central tube...."
"The body shroud consists of two pieces, an inner cone made of Kevlar®
fire resistant paper, and an outer cone made of heavy card stock with the
surface details printed on it. The inner cone is pre-cut for you, but the outer
cone must be cut out of its large rectangular sheet."
"...the entire kit is made up of paper and wood with one exception. The
launch lugs are carbon fiber tubes!"
"There is almost no finishing to be done on this kit....only things you
have to take care of are the second stage fins and the incredibly pointy
basswood nose cone"
"Flying the Sprint ABM requires careful attention to the CG."
"A stack of steel washers is supplied to place under the screw eye in the
nose to further move the CG."
"...the Sprint ABM is a fun kit....enough challenge in a few places to
keep it interesting."
Overall, the article states this is a good kit that provides some challenges. The article also provides an alternate method of gluing the cones together that allows you to "dry fit" the cones until you get them correct. In addition, the authors suggests an additional means to shift the CG forward.
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