D Boost Glide Boost Glide combines the challenge of building and flying a glider which can boost relatively well (and hold together) on rocket power, and transition to a long gliding flight. Boost Gliders often use a pop-pod, or sometimes are attached to the side of a larger rocket (parasite) for the vertical boost portion of the flight, then separate for the glide back to earth. If the entry kicks out an engine, the engine needs to have a streamer on it. A free-falling engine casing will be DQ'ed. The glider portion is timed. The glider must be returned for one of the two flights allowed. Flex-wing (Rogallo/hang glider) type gliders are not allowed. For the full rules for this event, please see the Boost Glide Rules on the NAR web page. Scoring - For Boost Glide, the scoring is the sum of the times from the two flights allowed, with at least one of those flights having the glider returned. Design considerations - Trade-offs of high glider performance, visibility, surviving rocket boost, and shooting for a reasonable boost altitude. It's not very practical to modify the proverbial 49 cent balsa glider to fly this event since the wings probably would rip off. Best to go with a kit, or with a plan. With experience, you might later develop a knack for designing your own gliders, but it's best to learn from a proven design first. For D power, it is more difficult than usual. A classic D12 boosted glider has a lot of stress on the wings. Some models shred the wings because they are just too weak to hold up to the velocity of a D12 boost. Also, it can be harder to get a model to boost straight on a D12 than with lower power. A list of plans and kits is included further down on this page. Unfortunately, there is not a lot in the way of plans for D Power Boost Glide. It is flown so rarely that not many plans have been made up of the successful models. Also, some of the more experienced glider fliers are using Radio Controlled (R/C) models. There is one good proven plan. Trip Barber's D-Light Boost Glider. It took 2nd, 3rd, and 4th at the last NARAM to hold D B/G, in 1997. If you are up to building a good glider from a plan, this is a really good one to use. UPDATE June 29th, 2008 - Sweepette 19
HLG Conversion page, and Hand Launch Glider website.
Of the kits available, the QCR "Neverloop IV" may be the most competitive. Some might want to try the Edmonds "Arcie-II". It could even be simply built as a free-flight model, with the ailerons locked into neutral. But it would be more fun to try it with the R/C gear. Other strategies involve the use of gliders designed C power. One way to do it would be to cluster a C6 and 1/2A3 engine, to nudge the model over 10 N-sec (a 1/4A would not be enough). That is a little bit risky, and if the 1/2A does not ignite the flight will not be qualified. Another way would be to stage a C powered glider with a C6-0 to another engine, ultimately another C6. Possible problems there are that the pod might strip at staging, and that the model might not boost straight. Worst-case it could even shred the wing. A final strategy is to "piggyback". Use a relatively large normal D powered rocket and just add a glider to the side of it. The glider will not boost really high, but it will have an easier ride up. With a reasonable choice of big rocket and piggyback glider, this is a fairly reliable way to go. One engine choice to consider is a D9-4 reload. The thrust curve puts a bit less stress on gliders than a D12, and is a full D engine. Drawbacks are the need for a reload casing, and that the 4 second delay may be a bit long for some gliders. Attention R/C Fliers: Please check out the NARAM-50 website's Range Rules Page for procedures involving Frequency Control and flying of R/C models during NARAM, both in competition and Sport flying. Update note: Greg Stewart has converted a small R/C sailplane, the Blue Arrow "Venus" to be capable of flying on D and E engines. The conversion is posted to the R/C Groups discussion group, and titled: Mini-How-To - Converting Blue Arrow Venus DLG to Entry Level Competition D/E Rocket Glider. Now, you really NEED to learn and know how to fly R/C first before you could safely be able to boost and fly this model. So if you are not into R/C, it is pretty much too late for you to try this in time for NARAM. The following are General Tips for Boost Glide, regardless of engine power:
Building Gliders - Ed LaCroix created some fantastic instructions for the Maxima A Boost Glider kit, from the time when Ed owned and ran Apogee. The instructions are for an "A" model, but the building tips and trimming tips are useful regardless of what size of glider. Kevin Wickart wrote a nice short article on how to do quick and easy airfoils, on the WOOSH section's website. Click here to read it. A VERY nice sanding block, useful for gliders, helicopters, and any rocket really, is an all-metal 2-piece clamp-type sanding block made by Red Devil, carried by most Ace Hardware stores (look near where they stock sandpaper). It has a 1/8" foam rubber backing sheet, which should be removed since it allows rounding things too easily in 3-D when you usually want to shape in 2-D at a given time (as with a wing). So, remove the rubberized portion. That sanding block holds a 4.5 x 5.5" sheet of sandpaper (quarter of a 9 x 11" sheet), with a 3.5 x 4.5" sanding surface area on the block. This works far better in most cases than a narrow sanding block. Of course, the wings (or fins) should be shaped and finished before they are glued to the fuselage or model. When doing very rough shaping for wings, 80 to 120 grit sandpaper is good for grinding off a lot of wood in a short time. Don't over-do it though by sanding off too much. Next use a finer grit like 180 to 220 for finer shaping. Beyond that, 280/320 paper, is sort of a cross between final shaping and setting up for a final finish. A final finish for bare balsa is sanding with 400 grit paper. Get the "black" type wet or dry sandpaper, it sands better and lasts longer than the reddish types. If you use any clear dope, use 320 to 400 grit paper before and after. Trip Barber's D-Light B/G Plan also has a good article that describes construction, sanding an airfoil, tissuing, dethermalizers, and even a launcher. So even if you do not build this model, it is worth reading for techniques and ideas. Glider Finish - Never use paint on a contest type glider. For newer fliers, no finish is usually fine. You don't want to weigh the model down too much and maybe having warping problems. If you want to improve the finish, use some thinned clear dope in one or two light coats, sanding before and after with 240 and 400 grit sandpaper. The idea it not to add weight or cause the wood parts to warp. Some fliers like to use a Japanese tissue finish. Trip Barber's D-Light Boost Glider plan has information how to tissue a wing. Coloring - OK, so bare balsa (even with clear dope) is not easy to see in the air or on the ground. Use a large black magic marker to color the bottom of the wing and tail surfaces black, as black shows up against the sky pretty well. Use a large red or orange magic marker to color the top surfaces. If you can find true fluorescent markers (not to be confused with wimpy fluorescent highlighters), an orange or red/magenta fluorescent color is highly recommended. Glide trimming - It is an understatement to say that it is very important to trim the glider to glide properly. It's not easy to describe just how to do so. One mostly universal tip is to have the tail of the glider and the wing to NOT be parallel to each other (there should be slight positive incidence). There ought to be a little bit of "up elevator" angle in the tail, relative to the wing, to make the nose pull up a bit. Some plans/kits may be quite specific, and in those cases go with what they say. Note that free flight model airplane experts sometimes prefer zero incidence, but they are deeply experienced (usually) to have just the right touch and experience to get away with it. The above being said, one of the simple ways to achieve slight up elevator effect (without adding too much) is to build the model zero-zero (wing and stabilizer parallel to each other), then warp the trailing edge of the stabilizer up. Make sure that the fuselage itself is not warped "down" - if it is warped at all, better to be warped "up" relative to the wing and stabilizer. Here are a few links for trimming tips from a number of different sources: Estes Boost Glider Technical Report, written by Tom Beach (pdf file from Estes Educator website). An excellent article with many illustrations that cover a wide range of areas involving Boost Gliders and Rocket Gliders, including trimming. HIGHLY RECOMMENDED. Kevin McKiou's Basics of Design and Trimming of B/G's and R/G's. Items 1 thru 5 are useful only if you are designing your own, or modifying an existing plan/kit. Items 6 thru 9 are useful for trimming gliders for optimum glide performance. Again, Ed LaCroix's instructions for the Maxima A Boost Glider has trimming tips. The instructions are for an "A" model, but the trimming tips and some other glider assembly tips are useful. Hand Launch Glider trimming tips for beginners, from a British Free Flight model airplane site. The latter portions about hard throws (necessary for contest HL gliders) is not too relevant for rocket boosted gliders (since the F/F HL glider flyers’ hard upward throws are their equivalents to our rocket "boosts"). Note the basic glide trim info and illustrations at the top of the page. Launching - Set up the glider on the pad so that it faces into the wind. This means the wing bottom faces upwind, and the wing top faces downwind. Actually the dihedral effect will usually try to make the glider face that way. Apply a flag of masking tape to the launch rod, so the flag holds the pop-pod high enough for the glider tail to not be touching the bottom of the launcher. Some people prefer to make their own glider launcher that has the launch rod mounted onto a 3/8" or 1/2" dowel, so that the whole rod can be used for guidance. A classic launch problem is for the micro-clips to fall at ignition to grab onto the glider wing or tail, causing damage or even disaster. Some prefer to tape the clips to the rod so they can't fall, which is effective but a bit messy. Others like to use an umbilical approach. They arrange for a separate launch rod, dowel, or other structure to hold the micro clip wires away from the glider, so that when the clips fall they will not fall straight down, but will swing away in an arc from the glider. A simple umbilical is to use a piece of 1/4 x 1/4 spruce 18" long or so, and cut the bottom at a very sharp angle that is about 30 degrees from vertical. Then glue a launch lug to the angled part. That way, the spruce umbilical can be slipped over the launch rod, umbilical angled at 30 degrees from the rod, ready for the micro-clips to be attached to it. Put your name on it, since the next person to use that pad will probably want to remove your umbilical. More Information:
Last Updated 5/28/2008 |
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