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Post by callun on May 31, 2007 20:52:39 GMT 10
I must say, these wooden creations scare me. Admittedly not so much this one, but certainly the Thorn, and while I wouldn't imagine these things get flown at Shorncliffe or Woody Point, I gotta say, I'm a wee bit anxious about being in the vicinity of them
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Post by st on Jun 1, 2007 7:33:51 GMT 10
Looks good Sean As you say, I doubt that will break, but will dint at times. A lot quicker, easier and cheaper than it probably would have been mucking around and trying different polymer noses. There is something very satisfying about having carved something useful from a plain lump of timber. Thanks Callun Does Andrews Minij scare you too? I'm a great pilot, really.... ;D
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Post by thevon on Jun 1, 2007 7:50:42 GMT 10
Yeah many gliders could be lethal. I wouldn't be as worried about the Minij (light and nimble, pretty fast) as the Drongo. Mainly because the Drongo is so heavy and just goes so fast, it's a bit of a blur as is comes down out of a dive and isn't so nimble, you don't feel so accurate in controlling it at that speed. Particularly in a full speed dive it loses up elevator responsiveness. The Minij on the other hand will turn on the spot anywhere at any speed - it feels like a foamie in that regard, but much more efficient - it also has a slip-on nose cone and the fuse/ cone glass is very thin so maybe it would crumple before your skull did! But the Ricochet is a much more solid glass fuse - a very rock hard nose! You don't want to get hit by a plane like that.
The flying is always most exciting when it's close, I'm as bad as anyone for wanting to do close fly-pasts, but we should keep well away from people, no doubt about it.
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Post by ezza on Jun 1, 2007 9:32:18 GMT 10
Hey Sean, Coming along nicely. It is looking really good! Fuse looks excellent!! Be sure and plug that fuse spar in nice and strong. I find sometimes when landing, if a wingtip clips something, it can have alot of side force(?) impact, from rotating and the tail hitting ground. Might even be worth wrapping some kevlar string/carbon tow, or something around that area, to stop any splits in the wood? If you decide to stick with the wood one, let me know, because I wouldn't mind buying a spare fuse.........or maybe I will be making a wood one too. Eric
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Post by sean on Jun 1, 2007 9:59:36 GMT 10
That's where the layer of glass would have come in handy... (d'oh!). If its gonna break it'll definitely be in that tail junction area, I'll just have to fly carefully . Sure, if you'd like the unused EPP nose I can send it to you, just PM me your address, or if I'm down flying your way I'll bring it along. Simon, you could almost use the timber nose to mould a rubber one, it would be a much better solution I reckon, just an awful lot of stuffing around as you say. Regarding lethality... yes I agree it will present quite a danger so no super close flypasts with this one. I must say that I don't think this kind of nose is unique in being dangerous, a solid carbon bird with a pointy nose would be just as deadly I reckon (those Jarts look pretty dangerous ). Also, imagine the danger of a big, heavy and fast powered RC plane with a hefty spinning propeller on the front for comparison... So yes, no close in combat at Shornecliffe with this bird!
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Post by ezza on Jun 1, 2007 10:26:17 GMT 10
Thanks Sean, We'll give it a while and make sure your happy with the other one first. Hopefully when you are down or we are up we will hook up for a fly. Looks like I have a free pass for Saturday, so my son and I might do some extreme slope searching and then pop into Beechmont, later in the afternoon, on the way home. They are calling light southerlies I think. Eric
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Post by thevon on Jun 1, 2007 18:01:38 GMT 10
Good luck with the searching Ezza. Gerard and I were fantasizing on the way home about hiring a pilot mate of mine for an hour or 2 and flying over the ranges to look for sites!
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Post by sean on Jun 3, 2007 18:25:28 GMT 10
Some more pics after another couple of days work... Here's the pine nose with undercoat and some filler applied to bulk out a slight flat spot: A couple of shots showing it on the workshop floor next to my Bat. The wings look very slender next to the Bat, although with similar tip and fin shapes there's a definite family resemblance. Nose is nice and smooth now with undercoat only. The tail is cut to length and the balsa fin is shaped and sanded close to an aerofoil shape, reay for covering. Once the wings are finished and the radio gear installed I'll figure out how much nose weight is needed and rout a slot in the bottom of the nose for it. With that long tail I hope I don't need too much nose weight... I'm thinking I'll install the wing with a couple of 10-32 nylon bolts now. While its a very tough nose it won't take a hit like EPP, and this thing is going to land fast, especially at Mt Mee where you have to land on the front of the slope, so anything that increases its crash survivability will be a plus...
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Post by sean on Jun 11, 2007 18:26:21 GMT 10
I started building the wing a few days ago. Here are some piccies: The wing just before the spars were glued in. They must be glued in with PU glue, I'm trying Selley's Durabond PU glue for the first time, it seems to expand nicely without bubbles forming (unlike Vise PU glue). Once the spars are covered in PU glue, you slip them into the cores and place the wings on the bottom beds, then cover the wings with the top beds and cover the whole shebang with weights of some kind. Weighting the wing down while the PU glue sets in essential to keep the wing profile intact... without weights the PU glue would expand and cause the wing to bend around the spar cutout. You also need to use glad wrap or something similar to stop the PU glue from sticking to the wing beds: 12 hours later the PU glue has completely set and I can remove the weights. Unfortunately I used too much glue, as it expanded it oozed out above and below the spar, what a mess! This glue expands a lot! Ahh, that's better! The excess PU glue has been sanded off and the wing's looking nice and smooth. PU glue is sandable... but its a bit like sanding leather... I used my Dremel to rout out a slot for the ballast tube. The empty ballast tube weighs about 40g, shame it couldn't be made of a lighter material I'll glue it in with PU glue later: The wing TE was not at all straight, I needed to slice off a thin sliver using a ruler and razor so that the basswood drag spar would have a decent surface to glue to. This is the only criticism I have of the cores, other than that they're very nicely cut and the left and right cores match well.
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Post by ezza on Jun 11, 2007 19:53:39 GMT 10
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Post by sean on Jun 12, 2007 9:30:42 GMT 10
Thanks Ezza, that would be the way to go, but I'll have to leave it for a future project as I don't have a suitable tube to use as a mould. I've just PU glued the ballast tube into the wing, so there's no turning back now!
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Post by sean on Jun 12, 2007 18:48:57 GMT 10
I was having a good look at the wing today and I reckon I can leave out the rear sub-spar, it just seems overkill to me. The carbon spars are more than enough to resist any bending force you're likely to subject it to (save maybe 200mph DS, but that won't be happening ), and there's also the brass ballast tube running through the centre section. The sub spar is probably there to resist twisting forces, but in my opinion twisting forces will be quite low and the carbon epoxied to the drag spar, with a little strapping tape plus the torsional strength added by the fuse will be more than enough. Deleting the rear sub spar saves about 25g behind the CG, which means I'll save maybe 40g in total (allowing for the reduced nose weight). That makes up for the brass ballast tube!
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Post by sean on Jul 20, 2007 0:04:46 GMT 10
After moving house successfully I've finally been able to get stuck back in to this project... As this model is quite different to the Reaper that it's based on I've decided to give it a new name, and the one that seems to have stuck is the "Griffon", inspired by the Rolls Royce V12 that powered later models of the Spitfire. I was quite keen on "Razer" as it hinted at the plane's origin, but found there is already a "Razor" sloper. I also like "Harp oon" (this forum's dirty word filter doesn't like that word, thus the space to trick it) which hints at the lethality of the nose ) but don't like the whaling connotations... First up I'll show the wing tips. These are a new shape compared to the Reaper, and curve around to be quite pointy at the tips. There are theoretical benefits to this shape but in reality it probably woudn't make much difference, and would depend a lot on how well the tips are sanded to shape. I put in a reasonable effort to sand the tips so that the aerofoil shape continues right to the tip, without getting too anal about it. This shape looks like it'd take hits badly but my modded Bat has similar tips and it's taken some huge knocks with few complaints. The rough shape has been cut with a knife, now it's time to sand the profile to shape. The first step was to roughly mark where I need to sand with a texter. I used mesh type sanding paper to rough out the shape. This shows the tip sanded to shape. 80 grit wet/dry was used to finish sand the EPP. I decided to use Matin's PU technique on the wingtips. You can read about this technique on the Ubercraft website here: www.ubercraft.com/PAGES/UC-HowTo.html. This method adds strength and allows for a nice smooth covering job on the tips. Basically it involves mixing a couple of drops of water with PU glue in a cup and pushing it into the foam as much as you can. The water accelerates the glue's drying and makes it expand nicely. In this pic the glue has set and is ready to sand. Here the tip is sanded to shape, it's come up quite nicely and will definitely look better under the iron on covering I'll be using. You could use this technique on the whole wing for a really nice finish, but if you do you'd better enjoy sanding! PU glue is not fun to sand IMO, I even found it a chore to sand these tips! BTW it is smoother than it looks in this pic!
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Post by sean on Jul 20, 2007 0:13:09 GMT 10
The carbon golf shaft tail boom needs to be glued into the pine nose with PU glue: The first step was to coat the tail mount and the area of the tail shaft that gets glued to the nose with a liberal coat of PU glue. These two parts are only a loose fit so the PU glue will expand and fill the gaps, providing a strong glue joint. The clamp is there to keep everything in place as the glue expands. Another shot showing the glue starting to expand. The glue's really expanded now! Actually most of this was just one big bubble, I poked it with a finger and it went right back down again... To get PU glue to expand reliably you need to keep pushing it down as it sets to stop bubbles forming. The glue has set and I've sanded it flush with the rest of the nose. Yep, looks pretty ugly but it's super strong! That shaft will definitely break before the joint fails (probably not a good thing ) .
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Post by sean on Jul 23, 2007 14:08:27 GMT 10
I've decided to attach the wings to the fuse with nylon bolts, mainly because I want to protect the nose from splitting in big hits as much as I can. I'm using two 10-32 bolts for the job. The idea of course is that they'll break in a big hit, but it takes quite a lot of force with a razer blade to shear them on the workbench so I really hope it's worth the effort... If they don't break they'll make quite a mess pulling the mounts out. However it will be nice to be able to dismantle this machine for travelling. There are two plywood bolt mounts PU glued into the top of the wing. They're made by expoxying two layers of 1/8" ply together. The mounts are tapered to distribute the load in an attempt to avoid creating a break point. The rear mount doubles as the drag spar joiner. The pics below show the process of attaching the forward bolt mount into the wing. First I need to rout out some foam: The foam ihas been removed and the plywood is sitting in its recess: The ply is glued in with PU glue, here I have the assembly weighted so the glue doesn't push the ply out while it expands: Once the mount was glued in it needed some filler applied on top so the wing surface remains nice and smooth. I've used PU glue again as it needs to be flexible yet strong enough to provide a good bearing point for the front bolt. I mixed some water in with the glue (as with the wingtips) and applied it over the bolt mount. As it was setting I kept pushing it back down to stop bubbles forming. Once set this created quite a dense, strong yet light filler. It's not evenly coloured though so in the pic below it doesn't look as smooth as it really is (back-lighting it shows it to be nicely faired into the rest of the wing surface): The finished job. The bolt holes have been drilled. The rear hole has a recess so the bolt head will sit below the wing surface to make everything look nice and neat .
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