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[QUOTE=payne9999;27876668]I checked on the cost of laser cutting a wing kit alone and it is not practical and a full short kit would be almost twice the cost of a commercially available kit. It doesn't seem practical.
Dave[/QUOTE I'm glad you mentioned at least thinking about making it available to us. Its unfortunate that the cost to produce is prohibitive, but after your modifications would you consider offering the laser cut file plans? I have a friend who would cut me a kit and I'd love to build it. I have two of the ARF models and I'd really really really like to actually build one for e-power and if I could shave some weight off of it at the same time that's even better. I know it takes significant time and effort to create the files so I don't expect that you'd just give them away but I'd sure love a set if you'd offer them. In any case, it sure is a beautiful plane and I cant wait to hear more about your flights and maybe see a video or two. John |
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Watching with interest. Good Job, Dave. I'm also interested in a short kit.
Randy |
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I am re-laying out the wing to have all the needed features including the flaps and ailerons (they were not in the original cut files, I added them by hand). So, I am building the whole airplane in 3D CAD to create parts that fit perfectly and have all the features.
Here is a screen shot of it under construction: |
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Congratulations Kudos for such a great build Dave!! I have been smitten by BOT for a long time, ever since I started working on Guppy-II (2M scaled up from plan bought from Mitja). I would be dying to see the DXF released soon as possible from you. Even a initial version with minor flaw is great. I have a day job which leaves little time to Hand cut parts, and my hands in fine cutting is not as clean either. I tried to convert few of the older 'Raster' PDF plans to DXF but the amount of cleanup was just too overwhelming for me (I have AutocCadded few Free PDF plans success fully like Shark etc). Getting a Kit Shipped from US to India is not a economical and logistical proposition for me. I have found few local Laser Cutting service and I have a small stock of Balsa, Lite Ply, Birch etc so a decent DXF plan with Ailerons/Flaps would be way better than Commercially available kit for me. So please please please do share your DXF plan for personal use with 'No liability' ! people like me would be more than obliged for your great work!! Looking forward for the release of the plan.... Thanks Ujjwal John India. |
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Last edited by ujjwaana; Mar 25, 2014 at 04:03 AM.
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I managed to figure out how to program some of the special sailplane features on my Futaba radio. So now I have "crow" or "butterfly" settings. It is so nice for landings. Crow basically sets both ailerons to up and both flaps to down while adding a little down elevator. Makes approaches very easy to control and prevents the plane from ballooning near the ground. It adds a lot of drag and slows the plane for landing while adding significant washout to the outboard panels. Aileron directional control is still maintained. A very nice feature that is possible only with a "full house" sailplane.
Dave |
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Last edited by payne9999; Mar 25, 2014 at 02:55 PM.
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Dave,
I suspect that that your tentative negative assessment of economic viability of a new short kit version of a Bird of Time themed model is correct........ Tower is selling a complete kit of the Bird of Time for $80 U.S. .......if/when they stop producing it, their kit will resale on these forums for a couple of hundred .... smiley) It think the distinctive wing shape of the BOT will continue to make it a classic that will re-appear in various forms.... you are probably aware that the 4m Albatross Classic ARF e-glider, bare bones, at $550, from Esprit, is a BOT clone. btw, for additional weight saving here a neat idea from "rkuntz" from a Sailaire glider build thread in 'Sailplane Talk' on this forum... note that the Sailaire is a 5 meter, 1500 sq. inch wing area balsa model so the diameter of its wing jointer rods are bigger but rkuntz's mod would also work on a 4 meter e-glider: "I'll call it "Sailaire on Jenny Craig" - or- "Every Ounce Counts". This is sure to draw fire from every pure Sailaire driver out there but I can only say I've been flying it for 4 years with zero problems, I'll back up what I'm about to divulge....here goes. One of the big areas of weight in the Sailaire is the wing rods. Made of solid steel they each weigh approx 5.3oz @. That's roughly 10.6oz flying 2 of them. Being an X Marine aviator and a retired IBM engineer it looked to me that this area needed to "go on a diet". Here is the solution I came up with. I replaced the .310 steel rod with a .312 hollow carbon fiber tube. (It fits in the brass wing tubes just fine with a little initial buffing.) Now, the plain carbon fiber tube is brittle by itself, you need to add a stiffner. I went down to the local Home Depot and bought a solid rod of 6061 aluminum in the raw material section. Get one that juuuust fits inside of the carbon tube. Once you get the carbon tube and aluminum rod cut to the same length as the original steel rod you tape one end of the carbon tube completely shut and mix up a good quantity of 30 minute epoxy. Coating the aluminum rod liberally, and making sure you don't get any epoxy on the outside of the carbon tube you slide the aluminum rod inside of the tube. As the epoxy settles add more until you have filled the space between the tube and the rod. What you end up with is one extremely strong, light weight hybrid wing rod. It does not flex much and in testing we did here it seems to have twice the strength of the original steel rod before it even attempts to bend. If you ever force a failure (I've been trying for 4 years now with no luck) the outer tube can fracture, the aulminum will slowly bend, the wing will tilt up a bit.....and you land. No sudden explosion as in a pure carbon fiber rod. All of my flying videos are flying with the hybrid rods, I don't use steel any more. Oh, and the hybrid rod weighs in at 1.5oz @, a considerable weight savings. (You just went from 10.6oz to 3oz total.)" good luck Michael |
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There appear to be several BOT clones or modified BOT designs out there. Skybench being one that has several sizes: http://www.skybench.com/index.html?h....com/home.html Soon I will be shopping for a carbon fiber rod for my modified BOT. Right now even at 39-41 ounces (depending on battery choice) it is quite light but I have really noticed that it flies better than my last one that was 50 ounces or so. Dave |
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Except for the outboard wing panel sheeting and cap strips, I pretty much have the wing laid out and the fit up of parts refined. A few more adjustments and the additon of the flap and aileron parts and it will be done. This type of CAD work takes a lot of time....
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Beautiful, and may I say your color match is near perfect, at least I see no difference in the photos.
BTW, have you tried the flaps in reflex mode yet (upward deflection) for reducing lift? I was toying with the idea of doing the same thing on my BOT for when I get around to building it, but keeping the dihedral and no ailerons (rudder turn). I had lots of different responses on the question, and was wondering how the plane would respond to "negative flaps" in real life. It's one of the main reasons I subscribed, besides it being a BOT, that is. |
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Last edited by Fly Wheel; Mar 25, 2014 at 09:32 PM.
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Dave |
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Check out www.acpsales.com for carbon fiber rods and other goodies..... in their 'clearance' page they have some neat 1/4" wide tapered thickness(eg. .042" to .007") unidirectional carbon laminate strips, up to 72" long, that would likely make for good spar reinforcements on big glider wings..... they also give the gram weighs for their solid carbon rods (eg. 12" of .312" dia. is 22/23 grams. I've ordered stuff from them and they were great... shipping was pricey to Canada but likely much better within the U.S. ... register with them first to typically get a 10% discount. Michael |
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Wing plan attached
Here is a preview. I am working on the DXF layout for cut patterns but here is a PDF of the proposed wing design. I will be working on the fuse and tail next. I am thinking of building a second prototype as a final validation. I would be willing to provide a full set of plans and DXF files to one or two folks if they are willing to:
1. Build a prototype 2. Test fly it 3. provide a short build log and video 4. Test fly by approx. 6/01/2014 Dave |
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Last edited by payne9999; Mar 27, 2014 at 10:47 PM.
Reason: UPDATED FILE, DRAWING CLEANUP
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Excellent! That was the result I was hoping for! What kind of elevator compensation did you need (if any) for pitch change?
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I didn't use any elevator compensation with the negative flaps. It descended quickly without any addition of down elevator. If I added any elevator it would be a slight up to avoid Vne. In other words, I was afraid to damage the airframe by using too much negative flap. My guess is it would take less than 10 degrees to get out of an overwhelming thermal. We used to refer to them as vaccuum cleaner thermals. However, I was probably being overly careful because the BOT was originally designed specifically for multi task F3B which included speed runs.
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