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Post by sean on Aug 7, 2007 18:35:20 GMT 10
The Reaper's moving ahead since my Bat's out of the air pending repairs after the pounding it received last weekend. Here are some more build pics (these are from a while back but I just got around to posting them): Radio Gear. The AAA nimhs are separated into two lots of two cells to clear the ply bolt mount in the centre. The receiver is a JR R77S PCM (came with my TX and never glitches, really happy with it), the servos are Futaba S3102s (they're supposed to offer less slop and better centering than HS-85s and only cost a few dollars more). The switch is soldered directly to the battery leads, and works the same as an NCFM blackjack, but I got it from Dick Smith for about 80c instead of US$10!! The plug cost about the same. It's a bit biiger than the NCFM switch making it much easier to solder (soldering the NCFM blackjack is a little beyond my soldering capabilites ). For those unfamiliar with the Blackjack, pulling the charge plug out turns the radio on, very neat I think. Spackling. I like to apply a very liberal amount of spackle (Red Devil One-time) and then sand right back so it's only filling the holes, not covering the entire wing. Spackle before sanding: After sanding: After spackling it's time to goop. For this plane I decided to goop the whole wing to be sure the strapping tape would stick well. I have found that it's a very good idea to goop the top and bottom of the wing at the same time. I gooped the top of the wing only on my old Halfpipe and the wing went banana shaped -- shortly after application the goop on the top shrunk, severely bending the whole wing chordwise. At the time I thought the whole wing was wrecked and ready for the bin, but overnight it went back to normal again, but I was never sure if it had gone right back to normal though . If you apply goop to the top and bottom at the same time you ensure that this doesn't happen. For the Reaper, I hung the wing on the clothes line so I could do this. It's a really good idea to goop outside anyway as the smell is very toxic and can make you feel pretty nasty the night after a gooping session... (Xylene, the stuff I use to thin my Shoe Goo to make goop is apparently banned in a number of countries). In the pic above you can see the radio gear embedded in the wing, the antenna is especially noticable snaking along near the TE. Those chunky spars can be seen too .
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Post by thevon on Aug 7, 2007 21:30:39 GMT 10
Wow, Sean that's a lot of spackle! Makes me feel heaps better, I was worried about how much I used! I rub the spackle into the EPP quite hard with my fingers to push it into the pores (?? pores - sounds like it's alive ...) then spatula it.
Man, really nice job - love the neat square holes.
That thing's gonna scream. We need a radar gun!
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Post by sean on Aug 8, 2007 11:55:30 GMT 10
Hey Andrew, yeah I figure it's better to apply too much spackle because it's so easy to sand, this ensures you won't need to apply a second coat. I use a spatula and push it in nice and hard too. I do sand almost all of it back though, so the spackle only fills the voids, the surface isn't dead smooth when I'm done. In the future I'd like to experiment to see if goop under and over a thick, dead smooth layer of spackle would be durable. If it was you could get a literally glass-like finish. At this stage I'm guessing it wouldn't be durable enough.
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Post by sean on Aug 12, 2007 17:38:39 GMT 10
Just a quick update... Here are some pics showing the strapping tape and bottom covering. The strapping tape used is from Windrider and came in a Bee kit. I really like this tape, it's light and 100mm wide which save a bit of time applying it, it's the tape I used on my Bat so I know it holds up well. I went with Ezza's recomendation of one layer of tape rather than the two layers recommended in the Reaper instructions. The tape covers the whole wing top and bottom and is layed at a 45 deg bias to aid torsional rigidity. After sticking down the strapping tape I iron it, which helps it adhere to the goop incredibly well and also evens out the surface nicely so your final wing looks a bit smoother. Afte ironing I also lightly sanded this wing with 150 grit which also helps to smooth the wing surface and helps the Profilm bond to the strapping tape. The pic below shows the tape on the top, after the bottom of the wing has been covered with Profilm: The pic above also shows my hinging method. I make my hinges using Profilm. Basically I cover the bottom of the wings and each elevon separately, leaving 10mm of covering forward of the elevon. Then I iron this extra covering onto the trailing edge of the wing. This creates the bottom half of the hinge. Once this is all done I can cover the top of the wings and elevons in one go, so the top covering forms the top of the hinge. The top covering and bottom covering adhere at the hingepoint making a very strong hinge. One advantage of this method is you can cover the entire top of the wing in one go, making it much easier to apply your designs and have them line up where the wings and elevons meet. The bottom of the wings after covering: That black Profilm sure does show the surface imperfections compared to the red or white (although it looks smooth in this pic, I angled the camera to avoid showing the bumpiness). The top of the wings are white and red, and the finish looks much better. Being the bottom it doesn't matter much, but I definitely recommend avoiding large areas of black over EPP, especially on the top of a wing.
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Post by sean on Aug 12, 2007 17:53:44 GMT 10
Here's the top of the wing, I'm really happy with the finish on the top, it looks way too nice to plow into the earth at Mach 1! Something I'm sure I'll do sooner or later .
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Post by jase on Aug 12, 2007 18:24:31 GMT 10
from the pics looks like you did a very neat job of it. can't wait to see it fly.
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Post by ezza on Aug 12, 2007 22:15:10 GMT 10
SWEEEEET!! Looks like a mouldie. Great covering job! Just try and keep it clean like that, until I get up there with my radar gun. Hope next weekend is windy as the weather has been way too nice lately.
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Post by sean on Aug 12, 2007 22:30:19 GMT 10
Thanks guys, yep fingers crossed it's windy next weekend, this bably should be ready by then! I'm waiting on a couple of parts for finishing it off. Soon after they arrive it'll be in the air. ;D
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Post by sean on Aug 17, 2007 19:36:58 GMT 10
The Griffon has flown! While not finished, I decided today to bodge the Griffon up for it's first flight. The wings have been finished for a week or two now, I just needed to mount the control horns and cut the control rods to length, which took about half an hour this arvo. I connected the control rods to one of the outer holes on the control horns which resulted in elevons that are very securely connected, the only slop being from the servos, and they have very little slop. Should remain flutter free while DSing, but roll rates won't be good on the front side, although this machine is meant for speed and DSing so that's OK. The fuse has given me lots of trouble though. The paint I used has been very uncooperative, the primer just didn't harden, and rather than trust my instincts and wait I decided to spray the top colour over it anyway. Bad idea! The top coat bubbled up in parts and generally looked crap. So after it was dry I sanded it right back to the timber ready for another go. I've tracked the problem down to the primer I used. In the past I've always sprayed on lots of primer to fill the grain and then sanded to make a nice smooth finish. But this time round I didn't use a sandable "filler" primer, I wrongly assumed all primers are sandable but this is not the case. The primer I used is meant for thin coats only so the very thick coat I sprayed on just never completely dried. Maybe if I had left it a few weeks it would have finally hardened but I don't have the patience for that! So rather than wait for the fuse to be finished I decided today to give the Griffon its first flight with the fuse unpainted. After connecting up the elevons to the servos, all I needed to do for flight was attach the fin, setup the radio mixes and balance. Because the fin will have to come off again when it's time to paint the fuse, I taped it on using double-sided tape and strapping tape (instead of gluing it in). Surprisingly this created a very solidly mounted fin, the only downside being it looks a bit crummy. Previously I epoxied about 100g inside a channel in the nose to get the CG close. Filled over with auto filler: To get the plane to balance exactly at the recommended first flight location of 44mm from the LE, I had to tape a small amount of additional lead to the top of the nose. Here it is, bodged up for flight . All up weight ready for flight is 950g. With a 15kt northerly blowing, I headed for Brandenburg Rd up here near Maleny. Before chucking the Griffon out I launched my Bat to check out the lift. As usual at Brandenburg the lift was OK but not nearly good as I was expecting given there was a decent breeze blowing, around 10kt+. The Bat would maintain height OK but it struggled to get altitude. After only a couple of mins I landed the Bat ready for the Griffon's first flight. To my surprise my heart was beating quite quickly as I held it up ready to throw out for the first time. I could just see the pine nose hitting the tarmac road below the launch point and breaking in two! But I needn't have worried. With a good throw she left my hands and flew dead-straight with only very slight trim needed. The control throws I used were spot on, the elev being neither too sensitive nor too sluggish. After flying around for a few minutes waiting for my nerves to settle it became obvious the CG was too far forward, it felt too sluggish and the nose was clawing for the sky. So a quick landing, remove a bit of lead from the nose and throw out again. Flew a bit better but needs lots of down in a dive, so bring it in and remove a bit more lead. I kept doing this until it became unstable, then added a slight bit of lead. With the exact CG now found (no lead taped to the top of the nose now) it was flying much better, holding energy well and flying quite fast considering the lousy lift. It was only now that I could sus out how she flew. Trim in a bit of down and the speed picks up nicely, accompanied by a nice howling sound (very similar to the sound of my Bat). Stability is excellent! It tracks beautifully both in pitch and yaw, definitely the most stable plank I have flown, infact stability is comparable to a conventional (ie tailed) glider. In these low lift conditions speed and energy retention seem quite similar to my Bat (that is, very good), but it feels much more solid in the air (the Bat bucks and weaves a bit in comparison). Turns can be pulled quite tightly with no tip-stalls, but the small amount of throw on the ailerons means the roll rate is quite low, but this just adds to the feeling of smoothness and stability. Overall the flying qualities are all that I could have hoped for: excellent energy retention and stability with lots of presence in the air. Also not very manoeuvrable in this low lift, but I expected that. It'll shine in big air, I can't wait to see how it goes ballasted on the back-side! Should really move ;D.
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Post by thevon on Aug 17, 2007 20:08:34 GMT 10
Man, Sean, that's really impressive. You've done a top job and your flight sussing-out is great! It's an achievement to get a plane working so well on its first session.
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Post by sean on Aug 17, 2007 20:22:52 GMT 10
Thanks Andrew . Normally I wouldn't get the CG sorted so quickly but honestly it was struggling to stay up with the CG forward in the low lift. On one occassion it got stuck in sink below the ridgeline. I kept circling hoping the lift would come back but it didn't. I watched it gradually go all the way to the bottom, disappear behind a tree and not come out the other side. As you know it's a long walk to the bottom of the gully and back at Brandenburg but fortunately there was no damage at all. I think I was actually flying it too slow as well, with a bit of down trim and more speed it actually stayed up a little better. Sometimes it's hard to trim down when you want your plane to go up . Also, there was no breeze at all when I walked down the ridge to retrieve the Griffon, even though the wind was blowing straight onto the slope. It seems that at Brandenburg staying up high is a must.
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Post by ezza on Aug 17, 2007 21:11:27 GMT 10
Sean, Amazing build! Looks so slippery and just perfect. Highly jealous. Where did the cg end up? I find around 47mm back flies good with mine. You are going to love ds'ing this thing! I was ds'ing the other night and the reapers just track and hold a circle so well. I turned the aileron rates right down to where they basically did not work on the frontside and was ds'ing pretty much with the elevator only......just too easy! Super keen for some ds this weekend and so is Swoopdown. Have not checked the weather yet, but earlier I noticed Seabreeze showed good easterlies for the Sunshine coast on Sunday. Keep us posted.
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Post by sean on Aug 17, 2007 21:23:33 GMT 10
You were DSing at night? Can't wait to DS it. I think I'm going to glass the nose to add a bit more strength for DS misshaps, not that that would ever happen . I'm very keen for some DS this weekend. Currently the forecast on Seabreeze is for strong SEs all next week. None of our usual sites are DSable in SEs, but the new spots Andrew found up near Pomona sound good for SEs.
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Post by ezza on Aug 17, 2007 21:58:41 GMT 10
Sean,
Yeah not quite it was after the sun had set but before dark.
Andrews ridges sound and look fantastic. Looks like they would work in almost any wind direction.
Might be worth a go?
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Post by sean on Aug 17, 2007 22:03:38 GMT 10
Ah I see, the wind does get nice and smooth around sunset. I wouldn't put it past you to try DSing at night though . I'll be up for a fly at one of the new spots on Sunday if you can make it up here, I really need to be good and get some work done tomorrow.
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