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Thread OP
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Discussion
Building a balsa sheeted airplane from a styrofoam hand-launch glider toy
I covered a styrofoam hand-launch aiplane/glider with thin balsa sheets. I used high quality carpenters glue to attach the balsa sheeting to the foam. After sanding the balsa, I coverd the whole airplane with 21st century fabric. The job turned out good considering this is my first covering job. There were a couple of areas that weren't factory perfect but this plane had alot of tricky profiles in it's shape. Before sheeting the plane with balsa, I re-inforced the wings, tail section, and fuselodge. I did glue the wings in permanently after sheeting them with the balsa. This was a practice project to pass time and to work on skill level. It was alot of fun too. Now I need help in the aerodynamics, C/G, power-plant requirements and the mounting of the motor. I stuck at a point where I need to mount the motor and battery. I could use all the advice I can get in this area. Another area of concern is wing lift, C/G and weight in relation to size and shape of the plane. Feel free to comment on the project in any way you desire. I know that the cost of the materials and the amount of time spent up to this point is way over-invested as compared to just ging out and buying somthing already made up. I had fun doing this and got lots of ideas for new projects so I feel it was worth what I put into it. What's you opinion? Check out the pictures let me know if you have any suggestions on: Mounting the motor / motor(s), battery - I was thinking brushless outrunner/lipo, Technical engineering in the area of wing loading cals and C/G, etc ... The airplane without motor & battery weighs-in right now at: 1lb - 12oz . 28oz total weight without motor & battery. Thank you in advance, everyone, for your interest and kind regards to all. SC
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Can you also give some dimensions such as wing span, wing chord, (width), at the fuselage and the tip, (to calculate the wing area).
The main enemy of good flight is usually weight, (i.e. wing loading). Actually the model looks ideal as a slope soaring glider. Here's a CG calculator, if you fancy having a go yourself, 25% mac is a good starting point. - http://www.geistware.com/rcmodeling/cg_super_calc.htm |
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Thread OP
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Wingspan: 53"
Wing chord at fuseelodge: 8-1/4" Wing chord at wing tip: 5- 3/4" Fuselodge length: 33" Weight (no motor / no battery): 1lb- 12oz ... 28oz. Your right about the glider interpretation ... it came as a $5.99 styrofoam toy originally. I could have made the wing broader to help with lift. The ailerons were not part of the wings' original design. They are actually the full length of the wing and about 1-1/4" wide. I hoped the extra width might help the lift calculations? The original tail section was on the same elevation as the main wing if you were to look at the side profile. I felt like the change to a T-tail might make the plane a little bit different but I had no specific reason other than looks. The landing gear is kind of heavy and could be removed if necessary. They are retracts and should probably be re-thought as this airplane is most likely more than heavy enough already? |
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The main problem I think is going to be the nose length if your going to put a motor there. And that's because you will need to balance the motor weight to get the CG correct.
If you do motorize it, I would strap the battery in place and see where the motor assembly needs to go to get it to balance, then chop the nose to suit. As BMatthews pointed out, it's not going to be a floater, in fact it it will probably be around 15-16oz/sq.ft. wing loading, and go as fast as it looks. That also means a fast landing speed. There has been quite a few threads on converting styro 'toy type models' to power and RC, if you do a thread title search on the name of the glider, (use Advanced Search), you should find one. |
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Bruce, I absolutely learned so much more than I could have imagined on this project. I'm a State certified Plumbing contractor and I have alot of experience in many aspects of mechanics, electronics, building materials etc. I've worked on automobiles, machinery and just about anything you can think of. I haven't come across too many things that can't be fixed ... even if you have to machine it yourself. I've always worked on things ... I could completely rebuild lawnmower engine by the age of 7 just by reading the repair manual. I had access to the tools and I had all the time in the world to learn. Now at the age of 45 I'm still learning ... how about that? Becuase of the elementary level of this project, I wouldn't have guessed that I could have learned much of anything. As it turned out, I learned one of lifes most important lessons ... how to have fun and enjoy the time we have. so many people miss this point. My hope is that this wisdom reaches every person that reads this thread. By the way I think that I might be having more fun now than I was at the age 7 . If this is even possible.
I bought my first control line cox pt-19 with the 049 engine at age 10. I paid for it with money I earned by cutting lawns. The mower I used was one that was built from several mowers thrown out to our neighbors garbage. I guarantee the cox 049 was taken apart and rebuilt more than once. This is the perfect example of what can happen if you just try. It's fascinating to see how fun life really can be if you just let it. Kind regards, SC |
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Eflightray, you are on track with the nose length. I think it's quite long as well. keep in mind, this plane is tail heavy due to the wood used to re-enforce the tail section. The fuselodge is thin at the tail section. I used some small planks of poplar to build the tail boom,elevator, and rudder. I also used carbon fiber rods to stabilize the rudder, stabilizer, and elevator section. This, along with the cable guide and the placement of the servos, puts more aft weight. The long nose may make the work easier ... It'll be easier to chopp off some of the excess rather than trying to add more? I got one step ahead of myself when it came to the battery compartment and the motor placement. after all the covering was on was when the need to put a "motor and battery" concept appeared to me. another concept that hasn't been completely thought out is the landing gear. Right now it looks like a tail dragger in the photo but my intentions were to go with tricycle gear. Thats not going to be good for the C/G issues that are on the board. I haven't ruled out Twin engines either. The propeller size is critcal as well. Depending on the engineering issues, maybe twin enginges will displace C/G issues, Power requirements, Landing gear needs ... etc? With Brushless motors and lipo batteries available today, the power requirements are easier to achieve. Ducted fan motors may not be as efficient but it might make for an interesting look if they were to be considered. I have to be mindfull of the project cost also. I did try a project like this one a couple of years ago without the balsa, covering, landing gear and extras. That one I just glued the wings in place, taped some carbon fiber rods to the wings (because they buckled due to the weight of battery & motor) and used a brushed 400 speed geared down. It was an old motor from a slowstick. I put a radio, servos, etc,. Nothing planned or calculated but it did fly good with a Nicad pack. It was nice to use all recycled parts and not have to buy anything for the project other than the plane itself ... $5.99. This one was alot lighter so landing speed was probably much slower. With the computer radios today, I suppose a mix of flapperons could bring the landing speeds down a bit? I wasn't trying to build a fast plane but you can't really prove that by looking at these pictures. I'm at a point where the power requirements & battery need to be decided so the modifications can be made to the fuselodge. The nose can be cut off, right in front of the wings and reconstructed as needed. That will also be the time to clear up the landing gear solution. The inside of the fuse is obviously all foam and can be easily removed. New structural design will be based on the battery loction. The battery location probably decided by the method you suggested ... sliding the pack along the fuselodge. I need more advice on the motor requirements at this point to determine the battery size. Power to weight means eveything here. The landing gear with the plane sitting level is about 5" . That might help determine the prop size. I am greatful for any support and suggestions available.. SC
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You'll likely want to end up shortening the nose a bit. Maybe to end up at around 2/3 of what is is now.
Sliding the pack around often isn't as effective as you'd think these days thanks to the light weight of the Lipo packs compared to the old metal cased heavy Nicds and NiMH's of old. The nose would be in keeping with this if you do decide to make it a twin though. That would actually be quite fun. And with the vast variety of good quality smaller brushless motors these days there's heaps of options. To make this a super sporty flyer you're going to want to run it with around 80 to 110 watts/lb. For spirited but not totally vertical climbs keep it around the 70 to 80 watts/lb point. Based on a 40 oz final weight that calls for 220 to 250 watts at full throttle. With a 3 cell pack you're looking at 20 to 25 amps for a single motor or that much total for two motors. Well, maybe a little less total for the twin since dual prop discs seem to end up a hair more efficient overall. And don't forget that for brushless that you need separate ESC's. You can still use one pack but it needs dual ESC's for a twin brushless. No sharsies... And disable the battery eliminator on the one ESC by cutting the red lead where it fits into the Y harness you'll need. |
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The bottom of this airplane has a thin strip of very strong & flexible pressure-treated pine heartwood 3/4" wide X 1/8" thick. The original build idea was to be a belly lander and I thought this wood to be a durable canidate. The strip goes from nose to tail. This wood is probably heavier than recommended but because it is so thin, the little bit of extra weight is not a concern to me. The grain and the cut of this wood is so strong and so flexible that I feel a little bit of extra weight is worth the trade-off. I don't want to add more weight to the plane than we need, but the styrofoam wasn't strong enough to handle the weight of a motor, battery, & electronics ...etc. The balsa sheeting wouldn't provide much structural support either. I think the way to do this modification is to open the front of this bird and make a lateral cut, completely through the fuselodge, from the front tip of the nose, just above the thin wooden strip, all the way to the leading edge of the wings, leaving the wooden strip in tact. The wooden strip is something I made at my radial-arm-saw. The strip of wood is flat against the bottom of the airplane so the structural stregnth is from side to side not up and down. Once the upper portion of the fuselodge is removed, the wooden strip will bend easily up & down but not side to side. With careful planning, I can attatch something structural to the strip that will carry the weight of the motor, battery, landing gear and the airplane itself . The front clip can be hollowed out to make room for a battery compartment and structural engineered framework that we come up with. If all goes well the front clip can be re-installed in a hatch-like manner after the upgrades and modifications have been made. I've put this part of the project on hold until now ... giving time to think about the engineering and surgical technique necessary to dis-assemble the front clip in tact. I decided to stop at the last step when I realized what I was up against. This thread, along with your advice and encouraging tips is the fuel I needed to get back into this project with a positive attitude. Thank you for sticking this out with me. Now that the ideas are flowing, I can start with the front access area. I didn't want to just jump right in... without planning for the motor, battery, and landing gear. I have balsa stock, cabon-fiber, Plastic, etc. I may even have something in the box of old parts that would give structure and fit into this compartment. It's going to be interesting ...I'm excited to see the outcome. I'll try to get busy on this so we can get the C/G calculations and power requirements fine tuned. You support is much appreciated. SC
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I've converted several of these foam gliders to RC, some for slope and some for power. I didn't sheet them, just used a 1/4" wood dowel for the leading edge, and then strapping tape strategically placed to reduce wing flex and increase durability. I always try to avoid adding weight.
I used the plastic tube-within-a-tube pushrods. I sanded them to improve adhesion and glued them on each side of the fuselage to strengthen it. I used them to operate rudder and elevator. I did use ailerons on one of these, and a T-tail on another one. I fly them as free flight models first to determine the CG and decalage I want. Then I attach the rudder and elevators, with control horns installed and hooked up to the pushrods, which at this point reach as far forward as about half way from leading edge of wing to the tip of the nose. I now use masking tape to mount everything- battery, Rx, servos, motor-temporarily onto the fuselage. I move things around until I like it, then I use a soldering iron or hot glue gun to melt cavities for everything. I glue everything in, so that the components replace the strength lost in making the holes. I add little or no reinforcement, preferring to just make repairs as necessary, rather than add weight right off the bat. Hot glue works great and is fast and cheap. 5 minute epoxy is used for field repairs. These planes are a quick and easy and cheap way to get something in the air. I fly hang gliders mostly so that's where my $ goes, so I don't have much of a RC budget. When properly configured they make good trainers. I don't know your experience level, but if you're short in this area you may want to set that nice one aside for a while. Go buy a couple more and a cheap Hitec radio, some dowel for the LE's, and some plastic pushrods. You can make control horns from an old credit card. Add some strapping tape and a few hours time and you've got a trainer. You don't need landing gear- save that idea for later. What you've done is great. In addition to what you've learned so far-how to do things- you will now learn how important it is to keep it light. Light planes have less energy to dissipate in an "arrival". They are also easier to fly. Your glider will do well on the slope, but with that wing loading she's no trainer. Let us know how you're doing. Good luck! |
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Dayhead, I like your advice about the weight issues ... I try to cut the weight factor down as much as I know how. The key words here "as much as I know how". The project gets involved and the materials at hand seem to revolve around each other, then a road block appears. My budget is limited and I like to recycle and salvage parts ... Using parts again on other models or buiding things out of other things seem to be a natural phenomina in this hobby. If it works, and is safely engineered for the purpose intended, then what is to prevent one from using parts to build new things? Thank you for the reply to this thread ... I can see at least (5) things in your comments that I have learned from you. In another regard A couple of your techniques have sparked some ideas in my mind . I did a lot of modifications since the last post I made a few weeks ago12/22/09 . I have some pictures for you to look at ... and critique as you choose. I hope BMathews and Eflightray and others might get a chance to follow up as well. You are all an inspiration to me in this project and I needed the advice and support to move forward. I was reluctant to cut front end of this plane, I was reluctant to deal with the landing-gear, not to mention the motor, prop, & battery issues. Keep in mind the budget restraints and the fact that I'm trying to work with what I have. My pile of stuff keeps getting bigger and I need to use what I have ... I know that it takes more time and energy to fix / repair / rebuild than to thow away and buy new but this is what seperates those who can ... from those who think they can. By the way ... Today this project plane taxied out onto the flying feild and took to the air. My eyes were wide as a frying pan as she lifted off. A good freind as the pilot ... and me ...the builder ... watching with excitement. The take off was so smooth ... I was impressed. The flight was awsome. This plane handles excellent. The power was perfect, the flite characteristics are excellent, even the landing was superb. This report is much different than I would have expected. I was thinking this plane would be a real mess to handle. Once the plane circled the feild several times, my buddy smiled and said "this plane flies really well", maybe you should give it a go for a minute. I took the transmitter in hand and after just a short time, " Yes ... it does", I replied. I let him bring the plane back to a safe landing and we tried another battery. The weather was as good as it gets and the flights topped the cake. I did not take a camera today but I will next time. I'll post the pictures of the recent modifications for now. I'm not 100% complete with the changes. I need to finish the covering and a few other things. When I get a few minutes I'll post the specs on the motor, prop, C/G ... Etc. By the way ... the final weight with battery, motor, landing gear, and modifications came out to a surprisingly heavy "50 oz". Somehow this all worked together for the good. You'll see what I mean when you see it fly ... Expect to be impressed. Thank you everyone this was fun day. Kind regards, SC.
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