Copied from other thread to here - should I erase the others, Thevon?
The Duck is dead - for the time being.
I took out one of the boys, who'd been short-changed on buddy-cord flying recently, to Barolin Rocks, but the wind was wrong, so we moved to Elliott Heads. The wind direction was close to right, but strong and gusty. We were there for buddy-cord training, so buddy-cording we did.
At first he was only in control for a second or two at a time, but after a but of practice he was able to hold it for 15s or so at a time - which was pretty good going for a beginner in those conditions, with a very limited space to fly in, and huge horizontal wind.
I stopped for a while and chatted to a bystander who turned out to be a fuel powered RC flyer with 20 years experience. As we were chatting, the wind increased to a crazy speed - he said it would be 30 to 35 knots. I told my son there would be no more buddy cord today, and he was happy to go down the beach 200m to annoy the lifeguards. The wind stayed strong, though not at the crazy strength of a minute earlier.
I had the first chance in a while to fly for myself, rather than instructing, so re-trimmed the Duck for inverted flying, which I have had limited practice with. I had some success, but even re-trimmed it was not quite sustainable, as with even full elevator the inverted nose wasn't held quite high enough. I've learned now that with bigger lift, the nose stays up better, but at a small slope like EH that doesn't usually happen, even when its windy. So about the 4th time inverted, with the nose down a touch, losing height, with the tide full in below me... Well, in the strong wind, there is only one direction the nose can be pointed for more than a second - seawards. And when the nose is below the horizon, and lift isn't bringing it up higher, the Duck gradually loses height. And, when you're losing height, the glider flies forwards in the direction it's pointed.
So, there I was, inverted, gradually losing height, pointed seawards, already over the water.
I waited for precious seconds, in vain, for a gust of lift to give me more time and height.
With only 5m height over the sea, there weren't many options. There wasn't room to half-loop out of inverted, nor even to half-roll out.
So I kept the elevator as far as it would go to try to keep the nose up, and began a very gentle turn, still inverted, back towards land.
Once over the rocks, with relief I began the half-loop to get out of inverted. Of course, at such a low height I had no chance of completing it, but that didn't bother me - just as long as I wasn't in the ocean. But flying briefly downwind from the water to the rocks had given my quite some groundspeed (you can see where this is going, can't you?). The end result was that the Duck hit at a fair speed, directly on its nose, directly on the rocks.
My son was running back up the beach, calling (I couldn't actually hear him till he got right to me, as I had climbed down to my stricken Duck) something like, "Nice inverted flying Dad!" I had to explain to him that actually it was very UN-nice flying, but he seemed still impressed.
Anyway, he went back to disturb the lifeguards again, while I took the Duck back up the little cliff/slope to the picnic table. I noticed that the elevons didn't seem right - the left elevon was up quite a long way. I thought that odd, as they still responded to the radio OK, and I hadn't changed the trim. So I re-trimmed the aileron and elevator settings as far as I could, which still didn't seem right, but I gave it a launch anyway.
The Duck shot straight up, then back over my head, and didn't seem to be responding to inputs, even though the elevons were moving OK to controls before the launch.
Luckily Elliott Heads has a huge backside area. Even so, with just a little response to the Tx, I was barely able to stop it going out of sight beyond the trees, onto either the road or the houses. It came down just inside the backside field, luckily, so I walked to retrieve it, looked again with puzzlement at the strange position of the elevons, and decided that, given the lack of any further trim from the Tx end, and given the (again) rapidly rising wind, it was time to retire for the day.
Later, at home, I was able to see more.
Over recent months, the nose has been getting very mushy. This final impact made it feel quite gel-like. But also I saw the cause of the elevon mystery - the left servo had popped out of place, and was pushing a bump up under the servo cover. Both servo covers have been broken for months, with fibre tape holding them together.
This evening I began to strip the nose of the Duck for a front-end rebuild, but this is now going to be a total rebuild. My camera wasn't working at the start of the strip-down, but I got it to work at the end of tonight's work.
The Nose is split in the middle, with 4cm either side of the split almost broken free. The ballast compartment has broken right through into the battery compartment. The top CF spar behind the battery compartment is mushed, and also broken around the left servo (in line with the end of the bottom main spar, which was supplied shorter than specified).
The clevis joints are rusted. There is the trademark tear in the EPP at the joint between Ducktail and elevon, especially on one side. The rear CF spars seem OK, and the fins (reinforced with bamboo skewers) seem OK.
So a complete strip and rebuild is called for. And some improvements.
I need a tougher nose, and generally less cut-away from the centre section. Perhaps I should use a split battery pack. All the foam in the centre, from the receiver forward, needs to be cut out and replaced with new EPP. Does anybody have a spare bit?
I need fibreglass spars, perhaps in conjunction with some carbon spars. Carbon is no good under compression.
I need dragspars, complete or partial, to prevent the Ducktail tear issue.
I'm not sure what else I need. Maybe Felix, Thevon, or others might have some suggestions?
I don't think I'll be buying my fibreglass rods locally.
Pij, sounds very familiar - a my Duck had similar issues! You're on the right track I think. I have various scrap bits of EPP from old wing beds that I use for repairs like that. I glue bits together with 3m77 or 5 minute, and sculpt them to shape. Even make replacement fuselages for Reaper/ Ozprey out of them - quick and easy. I could send you some if you're desperate but hopefully you can track some down locally? Also the kite spars - I'd suggest the 2.4mm glass rods. I don't currently have any but they're a very bog standard kite accessory, so maybe try some other kite shops?? I never managed to eliminate the tearing in the inner elevon corner entirely. Don't use dragspars - just embed some sort of stiff spar about a cm in front of the TE spanning well past the corners, and glue it in firmly so it takes the stretch rather than the TE. And bog up the nose liberally with Goop to give it lots of doink factor! But you will find that the Duck will lose some performance as it gets bulked up with repairs. Great for stronger wind but the light wind performance does start to suffer.
Hey pij sad news about the duck but all very familiar damage lol…..flying at sc this sort of thing is a regular occurrence.
The nose on the beelix I rebuilt with layers of that very soft epp that computers come packed in. shoe gooed together and with a final thick coat of shoo goo it was outliving the normal epp around it! The tearing on the duck tail I managed to solve completely. I used hardwood drag spars, the wood they use on planking of model ships of all things? I simply shoe gooed it along the trailing edge and about 1” past the duck tail junction. Worked a treat. Also supplies a very good surface for silicon hinging to bond to.
Spars I really recommend forgetting about carbon and go with FG solid rod shoe gooed into a slot…..did I mention I love shoe goo? If you mange to break them you’re doing better then me haha.
Onto covering I would definitely recommend laminate 100%. Do away with the the bi tape (you won’t need it) and generally it ends up lighter then the average tape job, vanders bee is proof of that. Will be stronger,quicker to apply ,more durable and much slipperier. Going to post a how to on how I colour the stuff shorly too if the naked look turns you off.
Thanks TheVon and Felix. Felix's suggestions match pretty closely with what I had in mind. I know the drag spar adds weight, in the critical behind-the-CG location, but I had been thinking about laminating film to cover, with minimal fibre taping, to save on weight overall. Andrew, were there other issues against the drag spar?
What about the split battery pack? I wanted to have less cut-out directly on the centreline, and also thought 2 small battery packs would let me put it all well forward, while keeping the ballast compartment on the centreline without any batteries up close behind it.
My plastic servo covers, from the UK, just didn't stand up to the job at all. One broke within the first few days, and spent months reinforced with fibre tape - actually pretty good then. Are there strong ones available, or should I make/modify covers myself with fibreglass?
I'm impressed with how the servos survived, right up to the point of one popping out of the foam instead of stripping a tooth. I think they were HS65HB's.
BTW Andrew, neither EPP nor kite shops exist locally. I have some scrap foam, which I'll investigate for the job. Will have to get FG rods from afar, or pay the local price!
Pij, I'm no expert really and what you've said sounds OK. My understanding of dragspars is they extend full span, but you only really need to reinforce either side of that inner corner area.
What do you mean by servo covers? Do you mean fairings over the servo arms? I don't have any covers - I do it the way Kye described in the Duck instructions. It's an advantage to use standard size servos as their size makes them more robust. I think split battery is a great idea.
Yes, I meant covers over the servo arms, and the first little bit of the pushrod. I also have some that extend some way along the pushrods, but haven't used those. By doing it as Kye described, do you mean fully exposed arms and pushrods? Or did you keep your servo arms short, avoiding them protruding?
Nah, I can't really be bothered with things like servo arm covers, unless they come with the model, or under the wing where they'll hook up on things. I'm happy with fully exposed arms and rods on foamies. Even my Reaper and Bat are like that and they're pretty quick. If you have a big prang and bend the rod a bit you can just bend it back straight.
Skyboyken turns his servos upside down and runs the rod up thru the wing so it joins a top mounted elevon horn.
I got those covers after having trouble with sand in my servos. I can still bend the rods straight again. The covers are taped on over everything else, so can be easily removed. Good idea I thought, but turned out to be too weak.
I saw the upside-down method on Ding's combat wing. Looks good to protect from combat damage, and aero-slicker. I remember reading from overseas that some places won't allow exposed gear in combat, on the basis that one hit can mean lack of control by a bent rod.
Wat about doing a goldern rod desing in it
Any thoughts on that people....i am thining of doing that in my duck
im getting it today YERS!!!!!!!!!!!!!!!! ;D