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Post by sean on May 18, 2007 21:50:39 GMT 10
Hey Fellas, I'm really happy with how my chopped Bat is flying at the moment, better than I would have ever thought given the way it flew prior to modification, so I wasn't going to build another foamy. But then I realised the Bat might die or fly away one of these days and I'd be stuck with nothing to satisfy my need for speed. So I just ordered a Reaper from South Pacific Models: www.southpacificmodels.co.nz/It was either the Reaper or a Gulp SR from www.stevedrake.com. The Reaper won out because it's sort of local, Ezza seems pretty happy with his, the wing looks just right for high speed flight and it looks easy to modify to conform to an idea I've been hatching for a while... Basically I want to build a nose for it using solid pine that houses only the balance weight, then mount all of the radio gear in the wing, Ubermoth style. This way the nose can be nice and pointy so it's real slippery (and deadly for that matter ) and I can finish it nicely (I just can't imagine being able to apply a good finish to an EPP fuse). The carbon golf-shaft tail will slot nicely into the pine nose too, and by using AAA nimhs and a micro receiver there'll be almost no weight penalty from mounting the gear in the wing. Yes, it won't be as tough this way but I plan to fly this one relatively carefully and use the Bat for the stupid stuff. Also if I'm ever able to find a good DS site it should be ideal. Ezza... looking at the pics of your two Reapers it looks like one has a bigger than standard fin? Is that right? Any other mods you'd recommend? Sean.
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Post by ezza on May 18, 2007 23:41:31 GMT 10
G'day Sean,
Yeah the second one I built (the first one was for my Dad), I made the fin as big as possible with the supplied balsa. Just wanted to try it out, I fugured it would track better while ds'ing.
I believe there is a new Reaper out with a slimline fuse? You can also get one with double spars!! It is probably overkill for our weather.
You are right about not getting a good finish on EPP fuse. Although hard to cover, it looks fine when first built, but after a couple of dodgy landings....not good.
Basically everything, except for the battery and switch are in the wing. The timber idea is interesting. I guess if it doesn't work you can always go back to the epp fuse. It should be fine as long as you land flat or in long grass.
After building the two, I would build the next one lighter. My dads is a standard build and I went heavier on mine. My dads flies in lighter wind better and it can be thrown around a little easier. If you build it lite you can always load it up with lead in the ballast tube. ;D
If you want any tips/help on the build let me know.
Eric
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Post by ding on May 19, 2007 6:55:16 GMT 10
I'm having flash backs here with all this talk of timber fuses. All you have to do now is mention painted bits and I'll go of the deep end! As someone who's been there, remember the reason we went away from timber is because they break Even if the fuse it'self doesn't break it will damage the wing mounting points.
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Post by sean on May 19, 2007 9:44:56 GMT 10
Hi Ezza, what did you do to make your Reaper heavy? I'd prefer it to be as light as possible so the handling doesn't suffer as you say. BTW I have ordered the ballast kit which will add some weight, even when empty... Regading the double spars, I thought the standard golf shaft spars were pretty massive! I won't be attempting the world DS record so I think the standard ones will be OK for me ;D Ding, I figure I can always go back to an EPP fuse if the pine one doesn't work. I've flown a few balsa slopers in my time and the sound of cracking timber is not good! But I reckon a solid pine nose will need quite a hit to break, so to avoid damaging the wing/fuse joint I'll probably add a break point, eg attach the fuse with nylon bolts. What I'd really like is a rubber nose like on the Ubermoth, but he hasn't been selling them for a good 6 months (www.ubercraft.com). Strangely I actually like flying a plane that you need to be careful with, but I also like being able to pick up a relatively undamaged plane after a crash, hence this project
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Post by st on May 19, 2007 10:23:38 GMT 10
Sounds good Sean. I like the solid pine idea ;D Ding, being new to the sport I'm curious as to what exactly you're refering too. Solid timber, balsa etc? What sort of planes/designs? I guess everything used to be made of wood! Sean, any idea on where you might get the nylon bolts? The local hardware here doesn't have them. Perhaps a bolt specialist would. It wouldn't be that difficult to make up a nose out of something tough & flexible like silicone rubber. Could cast into mould (which could take a lot of time to make), or cast into a block and shape, or dip nose for a covering.
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Post by sean on May 19, 2007 10:40:37 GMT 10
"I like the solid pine idea" -- I thought you might ;D You can get nylon bolts from most hobby stores, of course they're pretty pricey that way so you wouldn't want to go through too many. They're also available here: www.bolly.com.au/grp/index.htmlBolly stuff its generally as good as it gets, but I havent tried ordering off their site. They seem to be more interested in ultralight props these days. I read an article by a sloper where he said he actually drills small holes through the top of his nylon bolts so they sheer properly in a crash. Might be worth a try but the thought makes me a little nervous... Hmm, the molded nose would be nice. The Ubermoth uses black Polyurethane rubber. You can buy black liquid polyurehane rubber for making molds but I reckon it'd be time consuming to find exatly the right rubber and make the molds. That kind of work is a bit over my head but if anyone has expertise in this area I'd love to give it a go.
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Post by ding on May 19, 2007 12:06:31 GMT 10
For what it worth, the nylon bolts usually live and whatever they are attached to tears out As to the project. Nothing ventured, nothing gained!
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Post by ezza on May 19, 2007 12:22:54 GMT 10
Hi Ezza, what did you do to make your Reaper heavy? I'd prefer it to be as light as possible so the handling doesn't suffer as you say. BTW I have ordered the ballast kit which will add some weight, even when empty... Regading the double spars, I thought the standard golf shaft spars were pretty massive! I won't be attempting the world DS record so I think the standard ones will be OK for me ;D Sean, I used a bit of extra carbon, on the TE join for extra strength, put the bigger fin on and potted some lead slugs from my M60 ballast kit, into the wing tips, so that I can add tip ballast when the conditions are choppy on the backside. This one came out almost 200 grams heavier with those few changes. It is like any weight added behind C of G, takes about three times more weight on the front, to balance. Carl also recommends two layers of fibre tape, before covering, you could get away with one layer though. Or two layers on the bottom and one on top. You will be amazed at how stiff the spars are! There is a big piece of solid aluminium to join them together. I can only notice the slightest flex at around 100mph and a full elevator turn. With the tapered spars, it is like they load up and 'spring you in the opposite direction, when you do a huge dive and bang a F3F style turn. Carl actually got second place at an F3F event in NZ with his reaper. This was against all kinds of large moulded planes. The Reaper really loves big conditions. It will also fly in the light stuff, you just have to fly flat and fast though. You can't yank on the elevator too much or she will drop out. You will be surprised how thin and sleek the fuse is compared with an M60. If you do build a timber fuse, you could copy the epp fuse where the wing attaches. The fuse wraps around the leading edge of the wing. Maybe then you could attach it with some sacrificial fibre tape, at the front and back? Eric
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Post by sean on May 19, 2007 12:56:13 GMT 10
Hi Ezza, I like the idea of a bigger fin too. Did it make much difference to handling? One thing I don't like about planks is the way they weave in the yaw axis compared to conventional tailed aircraft. That's because the fin's just not far back enough to be truly effective, although the faster you go the less it matters. That's one thing I like about the Reaper, the fact that the fin is mounted further aft than on most plank desings. I'd actually like it to be even further back like on the Gulp SR.
I'll think about the mounting method for the pine nose, I'm definitely going to do it even though it'll be more prone to breaking that way. Although I've seen plenty of pics of broken M60 noses so I reckon a long thin nose is always going to be prone to breaking, no matter what material is used. I reckon I'll either use small diameter nylon bolts (would sheer better than the normal 1/4" ones) that coulod be replaced with steel for DSing, or just goop the fuse to the wing and be done with it.
Do you think the wing's torsional strength would suffer with one layer of tape? Probably not I supppose, My Bat only has tape on the LE and centre section and it's pretty stiff, I think the Profilm helps a lot there.
I'm really looking forward to this one now! I'm not a yank and bank type flier, I like to keep the energy up with nice carving turns, so it should suit me well. I must admit the price was a bit hard to stomach, but then the only other foamy I know of with carbon golf shaft spars is the NCFM HP60, and its only $10 bucks less and doesn't include the fuse, and of course those guys have the advantage of a much larger domestic market.
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Post by st on May 19, 2007 13:15:32 GMT 10
I used to work at QMI, where they do this sort of stuff (rapid prototyping). Unfortunately I was never involved directly in the mould making side of things, more the investment casting. I can help with the process, but not the exact materials involved. If you go the moulded solid rubber route, you'd make a positive first, out of anything really (the same shape as finished product). Coat it in mould release and then cast a polymer (I've seen silicone & epoxies used) around it. If silicone, you then cut through to the part with sharp blade and open the mould. Then close up and pour the desired part via hole in mould. There are little tricks like having risers (extra holes basically) so that air bubbles dont get trapped. If epoxy, you pour the mould in two stages. The process itself is quite simple, the main difficulty would be knowing what materials to use and where to get them. It was 6-7 yrs ago I worked there - could look into if anybody I know is still there if you like (when I get back from holidays...) ........ Hmm, the molded nose would be nice. The Ubermoth uses black Polyurethane rubber. You can buy black liquid polyurehane rubber for making molds but I reckon it'd be time consuming to find exatly the right rubber and make the molds. That kind of work is a bit over my head but if anyone has expertise in this area I'd love to give it a go.
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Post by thevon on May 19, 2007 14:47:36 GMT 10
I use standard Dubro nylon wing bolts in the Minij, and they regularly shear (well, they used to ... I fly it nicer now!)
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Post by ezza on May 19, 2007 20:09:26 GMT 10
Sean, I think the bigger tail helped. Once I had a bad landing and the tail snapped off, right along where it attaches to the fuse spar. I just dug the piece out of the spar and glued the fin back in. About 1 cm shorter in height, but still larger than the standard size fin. I have not noticed any bad yawing with either of the planes. The M60 does not specify even 1 layer of fibre tape and it holds up alright. I think the iron covering helps alot too. The Reaper has a shorter wing chord than the M60, so there is less 'twist'. It is more expensive than a normal epp wing but I think you will be happy. Will this be your first plank? If not, you know how accurate you have to be with the c of g on planks. The instructions specify 44mm but I have found it 'much' better at 46-47mm from the LE. Eric
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Post by sean on May 20, 2007 9:36:55 GMT 10
Hi Ezza, The yawing I've noticed with planks isn't anything too bad it just looks a little wonky sometimes. You can generally see the tail weave left and right after a roll or after a stall turn for example. You can see it in this video of a Birdworks Zipper: www.maui.net/~courtice/zip02.wmvIt's not the best example, but about halfway through this vid he does 2 or 3 fast rolls and you can see the plane rotates around the middle of the left wing, rather than the fuse, and when the rolling stops the tail wags left and right a few times, this is typical of almost every plank I've seen fly and suggests a lack of yaw stability. Do a stall turn with a conventional plane and the tail tracks beautifully with no waggle. It's also a shame that planks don't have very axial rolls too, the Bat was awful in this regard but mixing some down with aileron helped. The Zipper's ripping it up in the vid above BTW! Looks great. Interesting about the M60 tape. I built a Halfpipe last year and it used very little tape, just the LE and centre. I copied this on my modified Bat and it's held up very well. I haven't successfully DSed though, but I reckon it'd be strong enough for the kind of speeds we'd see over here. Thanks for the CG hints . I bet the elev throws you use are pretty small? I suppose this'll be my first really pure plank. The Bat and Halfpipe are planks, just not the really pure kind like the M60 and Reaper. The Halfpipe inparticular was also very sensitive to CG location, and elev throw was about 3mm each way. The Bat CG isn't so sensitive, but positioning it a millimeter or two ahead of the point of instability made it really come alive, at the expense of low speed handling I emailed Carl about the 'efficient fuse' option. He says it's a sleeker looking full length EPP fuse, rather than the nose only. But I rather like the pod and boom style of the original fuse, it's more unique...
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Post by ezza on May 20, 2007 10:21:36 GMT 10
Hey Sean, Yeah, I know what you mean about the yawing. I must be pretty used to it. I have always liked flying planks. Although the reaper probably does it less than other planks.
I have about 3mm of up and down and the ailerons turned down to about 5mm. The lighter one has about 5mm of up and down and the ailerons on full rates. I just found with the heavier plane, it flies great with less travel. I can turn up the ailerons, but that just slows her down. I like to try and do really slow axial rolls, which is pretty hard with a plank. Like you say having the c of g back and a little down stick helps. Yeah, the pod and boom steup does have a unique look. I think the new fuse is ultra smooth, but you will see, even the standard fuse is pretty slim, once you shape it. Shoot me an email and I can send you a photo.
Eric
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Post by ding on May 20, 2007 12:55:04 GMT 10
As a point of interest the yawing is called adverse yaw. If you ever learn to fly full size gliders you'll see that balancing rudder and aileron is one of the first things you have to master. It adds another dimension to things when everything is quiet, then a little bit of aileron and the air is gushing under the sides of the canopy
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