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Post by thevon on Nov 12, 2007 8:37:33 GMT 10
I wonder if we should put stuff like this in a "chit chat" forum? I'm keen to keep the build threads or dedicated subjects fairly undiluted so they can be useful as a reference. Eg Swoopdown is going to use this thread for a Bat Build soon, also Gerard, plus Ming from Windrider and Karl the Predator from US (Superfreak Bat guru) are keeping an eye on it too. People give up on reading a thread if there's too much junk in it. Sorry for sounding pushy but it's probably worth trying to keep the info threads clean and to the point.
I'm having trouble loading photos and need to sus out the ftp problem, too busy to do pics just now. But any camping shop has the burners - about $8 for a canister and the screw on burners start at about $15 I think. The expensive burners cost more because they're super-light so you only need a cheap one unless you plan to take it bushwalking!
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Post by thevon on Dec 4, 2007 7:13:42 GMT 10
I decided to get stuck into stripping the Bat back. Getting pretty beaten up, not helped by being shot down on Sunday.
When I was ripping the covering and tape off, one very key finding is that the areas where I sprayed 3M90 (near the LE's, tips) the covering has stuck MUCH harder than the other areas. The main parts where I sprayed with super 77, it's easy to pull off but it's really well bonded to the 90 areas.
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Post by skyboyken on Dec 4, 2007 19:05:17 GMT 10
Hi Andrew,
great to meet you and Sean last Sunday! You have really got Paul and I revved up to get into DS and we are both looking to get Bats as a starter plane.
So, some questions which will hopefully be relevant to this thread:
1. Could the round internal spars be omitted? As they are not joined through the centre all the flight loads are being carried by the ribbon spars which are obviously doing that job very well. As I understand it the only benefit of the internal spars is to limit flex in each wing panel and between the flat spars and the drag spars you seem to have that really well covered.
2. Why did you use carbon drag spars rather than the traditional hardwood? I ask because I'm thinking that hardwood would be easier and less messy to sand to match the wing profile (this may or may not be so, it's just what I'm thinking), and also that it has less tendency to flex and splinter as you describe earlier in this thread.
3. From where did you source the Bat in the first place?
Both Paul and I were really impressed with how well your Bat flies. Because of the truly vicious interference we get at Bald Knob I'd like to offer our experience that Schulze receivers work really well for a lot of us who fly there .
Go Great!
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Post by thevon on Dec 4, 2007 20:22:38 GMT 10
G'day Ken, yes it was great to meet you guys up there. Yes I think the Bat's the way to go for a starter DSer. Some answers: 1) I'd definitely leave the round spar in, but do it like I did, boring the hole and fitting the spar full length to the tip. It's a huge benefit when you spear the wingtip into the deck in cartwheels, absorbing the end-on impact. I think without it, the wing would bend more and smash up your lighter surface spars. The other better way would be to run decent-sized (5 or 6mm) round spars in trenches, full span, top and bottom, above each other.
By the way I wouldn't say that the flat spars have done the job very well. Mine are too thin and have kept "popping" which I think is not due to flex, but due to head ons where the nose stops and the wingtips bend forwards ... the sort of bend that tears the inner elevon cutout corner. There's a big discussion about this on RCG where I was critical of the vertical spars and after all that, I've changed my opinion. I was thinking that the worst forces were "wing load" type, but in fact I think now that the more commonly destructive impacts cause the horizonal bending. The flat spars can't handle big tearing force so if you put them vertically in pairs, they should do their great job of giving enormous vertical load stiffness, but they'll just bend with the nose-ins. So I'd suggest a combination of spars, not just relying on one type. In my current rebuild I stuck some vertical ones in to supplement the flat ones.
Regarding the centre join, yes you need to brace it for some distance either side of the midline and again, I think multiple vertical paired ribbons are great.
2) Re: the drag spar, you don't need to do anything really, but I knew other guys used dragspars, and I'm a bit of a novice really so I've never used hardwood. Probably it would be great. I wanted to use carbon so it acted like another spar. The Bat's TE is quite deep , nearly 10mm, so there's a lot of depth for the carbon strip to create a good stiffener. It definitely added stiffness straight away when I stuck the original 0.5mm one on. . Last night I ripped it off as it had a couple of breaks and I've put a 2mm thick carbon one on! Probably excessively heavy, but it adds lots of strength. Much less chance of breaking ailerons too. As for the wing spars, they meet in the centre, so I put an offcut of the dragspar carbon across the middle as a bridge, and shoe-good it in. Very effective!
3) I got my Bat direct from Windrider- I think it was $80 AUD landed at my door a week after I ordered.
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Post by sean on Dec 5, 2007 10:14:30 GMT 10
Hi Ken, it was good to meet you on Sunday . Glad to hear you're looking to build a Bat! I used hardwood on the TE of my Bat, I find it easier to get a nice square hingeline that way and like you say the hardwood doesn't shatter as easily... Sean.
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Post by thevon on Dec 5, 2007 12:52:53 GMT 10
Forgot to say, I trimmed my carbon dragspars to shape with an angle grinder! (very gently!).
Edit: (much later ...)
The Bat rebuild is finished and it's ready to DS again!. All up weight is 1.14kg (gulp!!) without ballast! I had to add a fairly big lump of lead to the nose to get it to balance at the (approx) CG.
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Post by thevon on Dec 13, 2007 19:20:41 GMT 10
Well I got to fly the rebuilt heavier Bat today. Should have got a photo of it, sorry. But the flying performance wasn't so great really, unfortunately! Not helped by the fact that my Optic 6 radio mysteriously stopped working when we got to Bald Knob. Naturally we first thought it was a plane or RX problem but not so - the radio looked like it was working but it didn't work on any plane, and changing the crystal didn't help.
So I got out the old Flash 5 radio and set it up to fly the Bat. But it was a bit rough - I've never been good at programming that radio so the settings weren't right, which may have contributed to the flying problems.
I had to add quite a lot more noseweight to get it to fly stable, but it didn't soar as nicely as before (the lift wasn't great either). When I slowed it down in a turn it fell into a violent spin which I couldn't recover from! Tried some different aileron settings but it still kept happening if I wasn't careful. One time it plummeted way, way down to the bottom, spinning like a leaf and there were 3 other lesser crashes. But at least it's tough! No damage.
DS wise, it was just like before. Heaps of speed retention. The conditions weren't great, but I got close to 80mph. It carves really nicely. But it's much harder to get height off the front now, for the dive-in. Sean got 111 with the Reaper.
So it's a similar outcome to when Sean re-covered his Bat last time. I wish I hadn't put so much more beefing up and glue and goop near the back end. I'm definitely a bit sad that it's not able to fly in milder conditions and that it's now developed some bad habits. I hope I can get the Optic 6 fixed and maybe it will behave better with its proper settings. But I'd recommend not rebuilding these too heavy - seems to be a recipe for disaster. It was flying beautifully before I rebuilt it so I now wish I'd left it as it was!
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Post by sean on Dec 13, 2007 20:31:30 GMT 10
Yes I think the lesson is don't build a Bat heavy! Mine flew beautfully at 800-900g but when I rebuilt it to be over 1KG it became a real dog. A very fast dog while DSing but flying it is stressful and it's too hard to avoid tip stalling it into the ground - it rarely leaves the house these days.
Despite not flying as well as it used to, Andrew's still flies better than mine - has a bit more wing area and less sweep.
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Post by ezza on Dec 13, 2007 22:32:54 GMT 10
There is a point where too heavy is not good. These planes will still fly good but only in strong conditions, which are so rare in our neck of the woods. I think only build heavy if you have to. Glad to hear you guys got some decent speed today. Was it straight South? Sean did you wind up the Bird? I took the Jw up to the lighthouse tonight and ds'ed all over the place. It was best off the back of the hang glider launch. Unfortunately I found a tree down in the jungle below the road 5 minutes before dark. Initially I just thought 'that is the end of the JW'. But then I tore into the bush and found a way through. When I finally got down to where the crash happened I was amazed to see the JW sitting on the ground right in front of me. Very lucky again! The zone is really sweet, but there are so many trees it is hard to witness the entire lap. Eric Yes I think the lesson is don't build a Bat heavy! Mine flew beautfully at 800-900g but when I rebuilt it to be over 1KG it became a real dog. A very fast dog while DSing but flying it is stressful and it's too hard to avoid tip stalling it into the ground - it rarely leaves the house these days. Despite not flying as well as it used to, Andrew's still flies better than mine - has a bit more wing area and less sweep.
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Post by st on Dec 14, 2007 6:29:03 GMT 10
Good to hear it is back in the air. Just a little whinge now...... What country are we in? What units do we use to measure speed? What is the international standard for measuring speed (aside from m/s ...) Please, we are Americanized enough without having to use a stupid speed measurement such as mph. We should ban the use of mph on this forum (at least as the primary indicator - put mph in brackets after the proper units if absolutely necessary....)! end of whinge ;D
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Post by thevon on Dec 14, 2007 7:08:45 GMT 10
Guys the extra weight I reckon is coz I got too carried away with goop etc. I gooped everything after spackling (quite thickly) and then after taping I gooped it all again, including the elevons because the yanks were saying that the covering sticks incredibly well to it. Also I went a bit overboard putting epoxy and strengthening under where the sticky tail fin coreflute mount attaches. Also Shoe-Gooing the bridge between the dragspars, and the dragspar itself is pretty thick ... the one I used on the Reaper is lighter but heaps strong enough. I put lots of tape for the elevon hingeing, etc, etc, etc. If I did it again I'd be more careful! I thought it would be OK coz I was flying it ballasted with nearly 300g of lead, which is heavier than it is now. But it was nice to have the option to remove it on milder days!
LATER EDIT: I got the Optic 6 radio fixed ... it was the buddy trainer switch. It felt gammy and soon as I unsoldered one of its wires everything worked. I flew the Bat again today briefly and it was definitely behaving better with the original radio.
Another benefit of pulling the radio apart was that I found the spring adjustment screws so I've increased the springiness of my control sticks. PLUS: I found how to set up the throttle control so it springs back to centre! I love that!
Simon we talked about the MPH issue before and chose to stick with it since the DS speed records worldwide are quoted in MPH. I bought my radar gun to read MPH too (with the Prospeeds you can't change the readout).
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Post by sean on Dec 14, 2007 13:17:48 GMT 10
Hi Simon, I'm not keen on Americanisation either (I notice you spelt that with a Z - was that deliberate irony?). But the international standard for airspeed is knots, and mph is also commonly used, the only people who use kmh for aircraft are the east Europeans.
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Post by st on Dec 14, 2007 17:12:08 GMT 10
.............................. (with the Prospeeds you can't change the readout). Looks like I'm were going to be hearing mph for a while then......... Of course it was deliberate Sean, glad you realized so ;D
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Post by thevon on Dec 17, 2007 16:19:55 GMT 10
Guys I've got some pics of the Bat rebuild. Firstly here is the mess after ripping off all the covering and tape.
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Post by thevon on Dec 17, 2007 16:25:42 GMT 10
Next here is the extra engineering ... carbon ribbon strips vertically and horizontally in various places! This is the topside close up. The black everywhere is from trimming back the thick carbon dragspar with a grinder! Lots of carbon dust. Be careful, it makes your skin prickly and itchy! Best to wear protective stuff. But I've found you can plane carbon with a wood plane instead. Bottom close up Whole wing, top and bottom Then applied PU/spackle mix - here it is being sanded:
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