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kendall, i really like your convertible drop box idea. you should be able to hold a ton of weight in there without stressing the servo much unlike mine (my servo actively holds the load up, one benefit being i can close the bay in flight). it also looks really simple & quick to add/subract. i usually rely on the lhs & toys r us. i bought my last batch of 10 paratroopers at toys r us; 5 for $1, 2.5" tall multicolored/multipose. btw, believe me, i've thought of many things to drop from bbap1, yep... including baggies packed with flour. i've even thought of a few that would be far more, shall we say, spectacular. i probably shouldn't mention them here, as they're probably illegal (& no, i've never done anything illegal with an rc plane... except possibly flying at parks where flying may or may not have been prohibited). ever since i've had a drop box, i often find myself thinking about that next flying session in ways that i never did before. kev [edit: btw, i bought 2 bp21's knowing nothing about them, just to fill up my shipping weight bracket on a uh order a while back. now i don't regret trading one of those motors for some blucor, hehe. i just don't see why the bp21 is so popular, now that you can find a 75%+ efficient motor for about the same cost at uh?] |
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Last edited by Truglodite; Oct 11, 2007 at 09:31 PM.
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kda20-22L test data
just got the new motor mounted so i measured the basic stuff:
KD A20-22L (2.365oz w/mount & prop adaptor) Hwing Pentium 18 esc (med timing) hxt d9 3s2200 (25c) APC 10x4.7sf at WOT: 11.7Vnew auw = 23.1oz (including new motor, 3s2100, & those thicker lg) new wingloading = 4.8 oz/ft^2 it's no hacker, but it's definately an improvement over my bp21! note that the kd motor is heavier than uh claims. i weighed the bp21 after removing it, and it came out to 1.790oz with mount & prop adaptor (slightly lighter than what uh says). anyways, 0.58oz isn't much of a weight penalty on such a large plane, plus i'm losing 2.2A and gaining 9.6oz thrust. iirc current was about 6A at half throttle. kev |
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Last edited by Truglodite; Oct 12, 2007 at 03:38 AM.
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Sounds good, kev, though I think drive calc's thrust estimate may be a little optimistic based on my small experience with it. If I were getting 30oz out of it I would expect it would take my 25oz BBAP vertical and it doesn't. I can sustain a Vx climb at ~60 degrees and briefly prop hang for 2-3 seconds before falling back. I think I'm getting more like 23-24oz. Let us know how it flies with the new powerplant.
I have a HXT 35-36C, 1100kV that's getting bored waiting for me to finish its sailplane. It weighs 3.7oz, but Drive Calc says it'll be good for 40oz, 20A and 74% efficiency with a 1060HD. 34oz, 14A, 78% with a 9050HD. If the goal is to get to altitude quickly, take pics/drop Lilliputian Rangers and come back down without floating around too much this one might be pretty nice. Given what she's done payload-wise so far I don't think she'll care about the extra 2oz of motor. I think I may try it. |
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Last edited by tuppertn; Oct 12, 2007 at 08:46 AM.
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at any rate, even if i'm only getting 24oz thrust it'll still haul loads much better than before. i will post a flight report as soon as i fly it (raining today). kev |
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Well I am back at trying to build a Blue-Baby after my first run and getting a warped fuse. This fuse looks much better! I am building the 33" version with a 4-40 wing and no ailerons. How much dihedral should be on each wing tip for a beginner?
Thanks, Ray |
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tuppertn
Thanks for the encouragement and information. It looks good so far! I would really like to build the larger 42" KF with aelorns next if this works out for me. I already have a motor and larger battery for it! I am off to glue the wings together! Thanks again, Ray |
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What size motor for BB 52"? Is 25amp too much? It is what I have on hand. Also, is the 52" a decent performer of basic aerobatics?
Thanks |
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Another BB takes to the skies!
Howdy all.
Despite windy conditions again today, I took the BBAP2 down to the field for a maiden. It took off in about 2 metres and sailed around the sky very nicely. No need for trim or CG changes. The CG came out just right with a 1700mAH 20C pack. The wind was such that when I cut the throttle for a glide, it was slowly going backwards. It landed nicely on both flights. Am very happy with the performance in the winds today. Cant wait for some calm conditions. The BM2409-18 motor had ample power, most of the time it was just cruising around with one third throttle. WOT the motor is pulling about 20 Amps on the GWS 10x8. I ended up putting balsa aileron stock on the TE of the Clark Y foam wing so that the rubber bands didnt cut into it and to give the TE a bit of strength as the foam edges was a little thin. Might put some CF tube or skewer on the horiz stab to make it a bit more rigid. What has everyone else done with their antenna? Mine is just trailing out the end of the fuse at the moment. Now to mount the camera! Thanks again Tony. Cheers, Glenn. |
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Kev: I had a question about that KDA 20-22L, I am actually awaiting mine in the mail as I write this. Can that little motor handle the 15 amps continous it is supposed to? My guess is not. Also, more importantly how will the amp draw be from a 11x3.8 APC prop vs 10x4.7? I will also have a 10x5E prop as well. |
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I have a KDA-20-20L which seems to be the same as the KDA-20-22L except the Kv is a little higher (less turns). While its a great well made little motor for the price, I found mine got stinking hot if I ran it at 15Amps for 20 seconds or so.
That was with ambient temps of about 25-30 degrees C. Glenn. |
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glenns, i routed my antennae on top of the fuse. it exits just behind the wing saddle, and from there it runs down the back & up the fin. i have about 3" dangling near the top of the rudder. my berg7 is mounted to the fuse side just before the "cliff" in the radio bay (near the top of the camera bay).
kilmerrc36, what kurpal & kendall said: as motor and battery weight/power is increased, you get to a point where high wing loading (aka weight) puts an end to the power party. however, the larger bbap's are designed to carry an extra 6oz or so, so they do handle extra weight very well. for this reason, if you're not planning on adding more payload (say a camera), i'll bet your 25A motor will work just fine. you may want to wait to see what tony says about this. kurpal, with a 10x4.7sf/12A everything stays very cool, but that's 12A and glenns said it gets how at 15A. unfortunately i don't have an 11x3.8 or 10x5e, or i'd spin it up real quick & get some numbers for you. i was planning on a trip to the lhs for some props soon... if my morning schedule works out well tomorrow i'll pick up those props & try them out. i was also very curious about the 11x3.8 as well (i haven't tried a 10x5e yet, since 10x4.7sf's are so dang good). kev |
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