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Post by atmosteve on Mar 12, 2008 13:36:32 GMT 10
I admit there is nothing much new in this build apart from the pull apart system and a couple of other things to come, but here are some pics anyway. This type of spar arangment has proven itself with the Bee, which has taken some mighty impacts without damage to the CF joiners and fly's sweet. The bee used 6mmby5mm CF tubes internally and 5mm solid rod joiners, but with the S15 being heavier and faster I chose 7mmby5mm wing tubes this time. Interestingly, the tubes and joining rods weigh no more than the solid plastic main spar centre joiner that would be used for a one piece version, and they offer a more flex free frame than by just gluing the wings together and joining the two main spars with the chunky plastic joiner, however their weight is further back. I must admit i love building a new model, in the past i mostly just flew them.
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Post by atmosteve on Mar 14, 2008 15:44:18 GMT 10
The glue gun is a good friend when it comes time to pot the servos-a-go-go.
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Post by atmosteve on Mar 16, 2008 15:23:39 GMT 10
After seeing to the spars and internal recesses, fitting the servos and seeing to the timber trailing edge spars (the spruce TE spars need to be planed back like on its little skua brother) The S15 gets a primary application of PU/spackle mix. We need to come up with some sort of name for this filling mixture... How about spewckle? For this i found TheVonster's instructions to be spot-on, the 1:6 ratio seemed to net the best workable results and gives the kwikset a tougher slightly flexible quality while still being sandable later. Andrew you are so right you cant muck about to much once you mix it, mixing a small handfull at a time seemed to work well as recomended. While this cures over a day or three I will muck about with the EZ glider if time allows.
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Post by thevon on Mar 16, 2008 18:45:47 GMT 10
Haha Steve well done! Looks a bit lumpy in parts ... hope you don't have trouble sanding it! I now try to spatula it as smooth as possible. It can be hard to sand if the mix is too rich, but at 1:6 it should be fine. It really makes a great skin on the EPP which can add to rigidity, and helps to heat-protect the EPP too.
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Post by atmosteve on Mar 31, 2008 18:53:50 GMT 10
Hi all, got her done just in time for a trip south down to Mt Coolum and the Glasshouse Mt area of the Sunny Coast. Build basically went like this; - Goop EPP likely contact edges, allowing a LONG LONG time to cure - Spackle:PU=6:1 filler mix (its amazing how much spewckle a wire cut wing will absorb) - 48mm bi-di tape over surface, around 85%, plenty of acetone cleaning between tape layers - I didnt find the time, but sand down the filament tape for a smoother finish before your next chemical application before covering if you can -A thinned coat of goop all over, including elevons and timber surfaces -Profilm covering What really needs to be stressed is the surface preparation between stages of covering, try to make prepsol/wax and grease remover and acetone your friends when using disposable chemical resistant gloves. This is a difficult model to incorporate a pull apart design into due to the thinner wing section, but this is the story for most planky spanky's. CG and a ballasting system were challenging, but thats the price to pay for something that you transport on a motorbike. Will chuck it off top of Mt Coolum tommorow, depending on weather. The Vonster is a current scratching for a Mt Coolum Fools day fly tomorow, sorry to hear it because Andrew originally suggested a few of us do the meet on April the 1st, he's opting for the safer but more turbulent inland pastures of bald Knob to try cut his teeth on a new radio, all the best with it mate . Sean will either be assisting Andrew and friends or up for a fly, either way guys lets hope we all have fun wherever we may be. Happy to be a fool alone up there tomorow, but it will be the very first place SE lift will be found and with this weather the views should just be unbeatable! Not expecting to find any backside at Mt Coolum, but the other sites may have something to teach me.
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Post by ezza on Mar 31, 2008 19:17:46 GMT 10
Hey Steve, Nice build!! I like the color scheme especially. Good luck flying tomorrow guys. Eric
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Post by thevon on Mar 31, 2008 19:21:01 GMT 10
Wow, looks beautiful Steve. All the more so because you went to all the additional challenge of making a pull-apart wing to take on the bike!
Look if yoooz guys are hell bent on Mt Coolum, I won't be a piker. But I might be best to find a friendlier "trimming out" hill first!
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Post by skyboyken on Mar 31, 2008 20:00:07 GMT 10
Good Luck to all!!!
Great looking Skua Steve!
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Post by Vanders on Mar 31, 2008 20:05:03 GMT 10
Nice finish mate, looking forward to hearing the report.
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Post by atmosteve on Apr 3, 2008 18:33:34 GMT 10
Thanks gents for all your comments. The glider was maidened at Mt Coolum on Tuesday, conditions turned out to be ideal for trimming out a spritely planky thing with a steady 12-15knots of lift, although it doesnt sound much, 12-15 knots of breeze = a whole lot of lift up there. The S15 performed really very well up there which was a relief after the rush to finish it. Removing 10g of lead from the nose and a flying weight of 995g had it tearing around the sky nicely balanced fore and aft. Acceleration and straight line speed were better than I expected, it holds speed well through tight fast turns. Originally I had drafted up a largish single central tailfin on a CF spar boom, but the pull apart design made incorporating this into the glider a structural liability. Seeming that the main event of the trip would be straight line speed runs from the impressive height available from Mt Coolum, I opted for the small experimental fins that were angled. They seemed to do what I figured,washing off inner elevon influence at speed but allowing enough airflow at lower speed for the inner control surfaces to take effect, while offering some righting properties, but not a lot as it turned out. Wednesday had the glider flying at a tighter sunny coast hinterland slope with a bit of a backside in light variable conditions. Here the lack of yaw preventing directional stability became more apparent, the little stabilisers just didnt offer the righting action needed for slow speed plank manouvres and without enough airflow happening in manouvres the glider would stall and spin out which was no huge surprise. Inverted performance I reckon is pretty remarkable, in fact it will thermal as well upside down as top side up was my experience. Mine wouldnt do tight inverted loops, spinning out of them which actually looked really cool when kept going. Again another vert stab design could help cure this. The S15 is certainly capable of light DS, but I'm not going to try it at that again untill I have a site with more backside drop and airspace under any sheer turbulance, until then I will have a crack at DS with Sean's more sturdy little bonka's Bat when possible. The reason is that I found the nose of the S15 to be fragile due its poking out and the thin overall wing section. I put it into the backside grass a few times and none of the impacts where particularly hard, but the nose began to weaken and get a bit out of shape. Its a very entertaining glider to fly, as Ken said it will handle light conditions fairly well. A little radio programing will largely cure it of those planky vices you read about and like virtually all RC aircraft it responds best to a smooth and minimalist approach on the sticks; let it find its own grove and it wont bite you. Today on the way home I got my Tx to create just the right differential into aileron function at PV north, the axial roll performance improved out of site (Sean you will be glad to hear this) but still it needs better tailfins for righting moment and a metacentre that has a little broader pivoting mass, if that makes sense. Removable twin fins that extend out the back of the TE are in the making, kind of lengthening the influence of the effect. Sorry to go on a bit, cheers for reading. Steve.
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Post by Vanders on Apr 3, 2008 22:17:28 GMT 10
Nice work mate, glad it all worked out for ya!!!!
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Post by felix on Apr 4, 2008 0:02:20 GMT 10
well done on a superb looking flyer! great lateral thinking on the wing joiners too.......i want one lol
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Post by thevon on Apr 4, 2008 7:29:52 GMT 10
Steve, sorry I didn't get to meet up with you during the week. What you said about the differential is really important, and it can make or break the performance. If I increase the up aileron throws on my Bat it becomes almost unflyable at lower speeds. One time my Optic 6 broke so I quickly set it up on my old radio, with fairly equal throws. Coincidentally it was just after a rebuild, maiden flight. It was so hard to fly, and spun so badly, I honestly nearly decided I'd wrecked it in the rebuild. But when the Optic 6 was fixed I gave it another try and it flew like new again. It was just the up/down ratio. Makes a huge difference with some planes. One trick is to fly straight and level and then bank (repeatedly). If the nose pitches up, reduce the up throw for that turn, but also check it for banking both L and R. I think that's the main problem, when you're going slower and you turn if the turn creates too much up, it stalls out.
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Post by atmosteve on Apr 4, 2008 16:05:17 GMT 10
Thanks guys. Thats it, unless you can program things like ali differential in while flying its best to take a small incremental approach. I finally found out how to do it with the MAX66 by experiment, the manual doesn't cover diff programing outside of flaperon mode and i couldnt make it work for both servos, so it was a relief to learn it can be done but with an odd trick with the right stick, but it cant be done while flying.
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Post by skyboyken on Apr 4, 2008 20:07:15 GMT 10
Great report Steve! I know it's a little late in the day now, but I'm curious about if/how you added any Goop to the LE and the nose particularly? I ask because I had to eventually cut the nose off my S15 and graft a new one on, as it deteriorated over time. Having learned that lesson I applied heaps of Goop to the nose of the next wing I built, which happened to be a combat wing. I've been both surprised and happy at how extremely durable that nose has proven to be. It even survived the Christmas Party speed landing contest in good order . It's now standard practice for me to do 3 coats of thinned Goop to the LE and tips of a wing, followed by tape, sand and a very thin coat of Goop over the whole wing with heat shrink covering to finish. I'm getting really remarkably good results from this process. For instance, at Easter I hammered my Reaper into a tree at speed while DS'ing. It went THUNK!! like an axe chopping wood. The impact left two large, soft dents in the LE, however the plane was flyable so I did! At home, I applied the iron to the 2 spots and kept it moving slowly. It was like magic. The foam relaxed back into shape, as did the Goop. The covering just shrunk back over it and stuck back down and in 30 seconds it was nearly impossible to see any damage at all. Sorry for telling such a long story. I just wanted to illustrate the virtues of Goop etc for a wing like your S15 with its nose that tends to take a regular pounding. I wish you every success and much enjoyment with it! They're a terrific plane. Ken.
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