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Scratch Designed/Built Sailplane Fuselage
This is a continuation of a couple of build threads I've been working on...
<ul>[*]Scratch Designed/Built Sailplane[*]Sailplane Wing Design Round II[/list]My original design flew beautifully but suffered from a design flaw in the wing (consequently it folded in half mid-flight). Since that fun learning experience I've redesigned & rebuilt a better wing. In fact the new wing turned out so nice that I'm reluctant to fly her with the original fuselage. So I'm going to redesign/build that also. This thread will document that process. Subscribe if you're interested. |
RE: Scratch Designed/Built Sailplane Fuselage
A new look
While I liked the profile of my old pod-n-boom design, seeing as I'm rebuilding this from scratch I have the opportunity to change the design if I wish. Here's a few "out there" ideas for the new pod. I'd love to hear your thoughts on which if any you like... http://www.scipie.com/rc/vee-gull/3D...ng_010_700.jpg Let me know which you like & why. |
RE: Scratch Designed/Built Sailplane Fuselage
I'll be watching. Really enjoyed the first two, especially the rebuild of the wing.
Personally, I liked the original fuselage profile the best. It looked the sleekest and the neatest. But, since you asked, out of the new ones, I like B because it is the slimest, and sleeker of the bunch, and I like E because it looks like a bird. |
RE: Scratch Designed/Built Sailplane Fuselage
A looks like the rear of the pod is a little abrupt to me.
B or F, leaning to F because it looks like a motor with 3° or 4° of down-thrust would blend in well. C,D,G, H, and I might disturb the air over the center-section causing more drag. The C might not need down-thrust due to the high thrust line. I don't get E. |
RE: Scratch Designed/Built Sailplane Fuselage
Making it really tough to pick just one. I would have to go with F. The lines blend in better as soarrich put it.
A and B look like something you find on some of the scale ships today. I reminds me of some of the designs back in the 50's and 60's. All good. Something of an elongated tear drop would be cool. |
RE: Scratch Designed/Built Sailplane Fuselage
Of the lot F and B are the sleekest to my eyes. And truth be noted there's precious little difference between them. It also sets the fuselage at an angle that will be decently close to the airflow coming up to the leading edge of the wing. Second in looks and streamlining, but not by much, is A.
The rest are either angled to promote too much "belly onto the wind" or simply look odd for no purpose. For example D is simply an act of desparation calling out for an intervention.... :D Funny yeah, but it's ugly on so many levels at the same time. Same with the "bird's head" on E. And the lump on the belly of I looks like a tumor..... |
RE: Scratch Designed/Built Sailplane Fuselage
I prefer I as it increases the wing tip clearance on landing and has the thrust line on the wing centre, it also give a skid type underside for landing on.
Mike |
RE: Scratch Designed/Built Sailplane Fuselage
Great feedback, thank you all.
I've pooled the opinions from this & my mirror threads on other forums & as expected, the more modern sailplane profiles (A, B, F) were the most popular. I could certainly go with one of those & end up with a very nice sailplane. However after thinking about it some, I've realized I'm not necessarily looking for the most efficient, most sleek design. I'm now leaning towards doing something a little out of the ordinary. Something that'll stand out in the crowd. The gull wing achieves that goal to a point but I'd like a "quasi-vintage" fuselage to go with it. So here's another batch of doodles... http://www.scipie.com/rc/vee-gull/3D...ng_011_700.jpg A2 Modern sailplane profile, while sleek, lacks uniqueness. B2, C2 Has a subtle avian feel (looks a little like a bird's head). I think these tie in wonderfully with the gull wing. Flying a giant bird might be fun. D2, E2 An under-slung pod design. Inspired from some vintage sailplane designs I've seen. Again these work with the gull wing & would be a little different. Once again I welcome comments & thoughts. |
RE: Scratch Designed/Built Sailplane Fuselage
E2 with the boom moved down to the back of the pod would be kind of Supra-ish.
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RE: Scratch Designed/Built Sailplane Fuselage
A2 with the E2 pylon. Sort of what soarrich had in mind. Think you are on the right track for something unique.
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RE: Scratch Designed/Built Sailplane Fuselage
That's an interesting idea soarrich. Here's how that might look...
http://www.scipie.com/rc/vee-gull/3D...ng_013_700.jpg Under-slung pod I'm leaning more towards an under-slung pod design, pretty sure that's where this is sailplane is headed. Its fun, different & I can't see any major reasons why it shouldn't workout. So here's a new set of doodles... http://www.scipie.com/rc/vee-gull/3D...g_012a_700.jpg http://www.scipie.com/rc/vee-gull/3D...g_012b_700.jpg |
RE: Scratch Designed/Built Sailplane Fuselage
Nodd,<div>L3 would make my day! Although you'd need much more tail fin for it to fly nice.</div>
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RE: Scratch Designed/Built Sailplane Fuselage
Nodd, your creativity is outstanding. Like the under slung pod design. Partial to E3 also.
Would be more dependent on keeping a smaller frontal area so as not to induce any more drag then needed. Then again, any of them would draw attention at the field. |
RE: Scratch Designed/Built Sailplane Fuselage
I may have to make a chicken plane some day but not this day *grin*
Enough doodling I could go on for weeks playing around with exotic pod shapes but I'd like to move on. Taking into account everyone's input (thank you) I've settled on this design that's a mixture of E3 & F3... http://www.scipie.com/rc/vee-gull/3D...ng_015_700.jpg Artistic babble While I like some of my more excentric designs, I think this one with its modern canopy merged with a retro pod works well. It has a few curves to keep things interesting without coming across as over-the-top. Well I'm off to the LHS to pick up some wood. Time to start the build. |
RE: Scratch Designed/Built Sailplane Fuselage
ORIGINAL: Nodd Well I'm off to the LHS to pick up some wood. Time to start the build. |
RE: Scratch Designed/Built Sailplane Fuselage
Yeah I know what you mean... "Balsawood? Do we look like a lumber yard? We do have over priced lumps of foam shaped kinda like airplanes though".
Well I'm back from the hobby store & bah (big surprise) they don't have the sizes I need. I'll have to hit the other store tomorrow, either that or order some online. Thankfully I do have internet *grin* |
RE: Scratch Designed/Built Sailplane Fuselage
Fleshed out
I did a little more work in CAD, here's how the pod looks fleshed out in 3D... http://www.scipie.com/rc/vee-gull/3D...ng_016_700.jpg |
RE: Scratch Designed/Built Sailplane Fuselage
Bounce Bounce Bounce
A guy over at RC Groups pointed out that my pod fuselage may cause ground handling issues. Specifically he felt the design would be prone to skipping during landing. Once the pod contacts the ground the tail will hit next raising the nose alarmingly & back up she goes, hop hop hop. So to fix the issue I'm thinking a small tail-skid should keep the AOAfrom getting out of hand during landing. It looks kinda cool too... http://www.scipie.com/rc/vee-gull/3D...ng_017_700.jpg |
RE: Scratch Designed/Built Sailplane Fuselage
Construction begins!
Enough design work, time to start building this thing. I printed a set of templates from my CAD software... http://www.scipie.com/rc/vee-gull/20120911_0001.jpg Used the templates to cutout the various parts then started putting things together... http://www.scipie.com/rc/vee-gull/20120911_0003.jpg She's starting to look like something... http://www.scipie.com/rc/vee-gull/20120911_0010.jpg Filled in the rear of the pod with scrap balsa... http://www.scipie.com/rc/vee-gull/20120911_0014.jpg A little pre-shaping of the hardwood nose blocks. Once installed I'll finish carving these until the motor fits... http://www.scipie.com/rc/vee-gull/20120911_0016.jpg I'm using 1/4" plywood for the pod support (the piece that connects the pod to the wing)... http://www.scipie.com/rc/vee-gull/20120911_0020.jpg Test fitting the support. I won't glue this in until the pod has been shaped & sanded as it'll just get in the way... http://www.scipie.com/rc/vee-gull/20120911_0024.jpg That'll do for today. I'm headed to the NEAT Fair so will get back to this when I return next week. Cya there. |
RE: Scratch Designed/Built Sailplane Fuselage
If you have the wheel behind the CG it wouldn't bounce, as long as the wheel touches first.
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RE: Scratch Designed/Built Sailplane Fuselage
ORIGINAL: soarrich If you have the wheel behind the CG it wouldn't bounce, as long as the wheel touches first. |
RE: Scratch Designed/Built Sailplane Fuselage
There's no doubt the first part of my fuselage to touch the ground is way out near the nose. Here's how she looks compared with a random collection of other sailplane fuselages...
http://www.scipie.com/rc/vee-gull/3D...ng_018_700.jpg It'll be interesting to see what happens when I land her. |
RE: Scratch Designed/Built Sailplane Fuselage
Not a lot to show today, started sheeting the top & bottom of the pod...
http://www.scipie.com/rc/vee-gull/20120920_0005.jpg Will have more soon. |
RE: Scratch Designed/Built Sailplane Fuselage
Your's is better looking than the others. Keep going.
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RE: Scratch Designed/Built Sailplane Fuselage
A-15 looks nice too, especially at its time (50 years ago). Great craftsmanship! Can't wait to see some flight videos..
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RE: Scratch Designed/Built Sailplane Fuselage
One month later...
Okay I'm done building my silly Piper Cub Sailplane, time to get back to working on a "real" sailplane. So where were we? Building a pod-n-boom fuselage that's right. I taped up the top profile template... http://www.scipie.com/rc/vee-gull/20121022_0002.jpg Then using the belt sander (love that tool) sanded to my marks... http://www.scipie.com/rc/vee-gull/20121022_0006.jpg Set the sander's guide plate to 45<font size="-1"><font face="Verdana">°</font></font> then began the rounding process... http://www.scipie.com/rc/vee-gull/20121022_0013.jpg I need to get the motor installed so I can shape the nose so it blends nicely with the spinner. I broke out the Dremal & started carving out the nose... http://www.scipie.com/rc/vee-gull/20121022_0017.jpg Major OOPS! I got the motor in & then to my dismay discovered that some nit-whit (me) had installed the firewall way to far forwards. Look at the size of that gap! NOT GOOD!.. http://www.scipie.com/rc/vee-gull/20121022_0021.jpg Move the firewall back? ...not happening. So the next best thing is to build up the nose so it matches the spinner's new position... http://www.scipie.com/rc/vee-gull/20121022_0025.jpg One nice thing about the belt sander is that it makes nice clean flat surfaces that I can easily glue scrap balsa too... http://www.scipie.com/rc/vee-gull/20121022_0028.jpg Glue scrap wood in place, trim with the sander... http://www.scipie.com/rc/vee-gull/20121022_0031.jpg ...& glue more wood in place... http://www.scipie.com/rc/vee-gull/20121022_0033.jpg Now to take care of the gap. Added a piece of hard-wood to the nose... http://www.scipie.com/rc/vee-gull/20121022_0041.jpg Some more sanding & we're looking good... http://www.scipie.com/rc/vee-gull/20121022_0070.jpg That looks better!.. http://www.scipie.com/rc/vee-gull/20121022_0043.jpg I still have lots more shaping to do but I'm happy with today's progress... http://www.scipie.com/rc/vee-gull/20121022_0065.jpg That was a bit of a PITA but on the up side I now have a nicely reinforced nose. Its good to be back working on this, fingers crossed there'll be no more distractions or hick-ups. |
RE: Scratch Designed/Built Sailplane Fuselage
Thinking Ahead - Wing-Saddle
I should probably start planning how I'm going to mount the wing to the fuselage. Here's roughly how she'll look... http://www.scipie.com/rc/vee-gull/20121023_0002.jpg The challenge here is to securely but temporally mount this huge wing to a dinky piece of 1/4" plywood... http://www.scipie.com/rc/vee-gull/20121023_0004.jpg Whatever I use to mate these two together needs to be bullet-proof strong but lightweight at the same time... http://www.scipie.com/rc/vee-gull/20121023_0008.jpg Traditionally this sorta thing is done with a wing-saddle... http://www.scipie.com/rc/vee-gull/3D...ng_019_700.jpg Making a wing-saddle from fiberglass & thin plywood shouldn't be a problem. What I need to figure out is how to attach that to the 1/4" plywood pylon so its strong. Any ideas would be appreciated. |
RE: Scratch Designed/Built Sailplane Fuselage
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Hi Nodd, boy is that ever looking sweet!!
I saw over on RCgroups some guys had suggested using small screws and fiberglass to get the strength on the pylon/saddle joint. Iagree with you that the length of the wing may cause the glass to crack, or perhaps even delaminate from the wood over time. The screws idea is nice though. Here is a little picture I drew up quick to show you how I would do it. Look at Pic #1, you will see Iadded some large triangle stock, you could probably even get away with hard balsa to keep it light. The, in pic #2, you will see Ihave neatly "rounded" the triangle stock. This would give you a lot more "glue" area for that saddle/pylon joint, a fairly nice brace, and possibly even provide a bit of aerodynamic help by giving a smooth radius where the two pieces meet. Probably would add less weight than glassing the whole thing too. Idon't know, just a suggestionhttp://www.rcuniverse.com/forum/js/f...ades_smile.gif |
RE: Scratch Designed/Built Sailplane Fuselage
Cover the bottom of the wing with packing tape and wax it. Laminate 3 layers of 6 ounce glass to the bottom of the wing. Once cured scuff the bonding area and bond the 1/4" plywood to the glass laminate. You want to build a fillet at the junction between ply and glass laminate. You can make a filleting compound by mixing your laminating resin with micro-spheres. Then glass the joint with 1 or two layers of 6 ounce glass on each side. If you glass the entire side of the wood then you could use 1/4 balsa instead of the ply to lighten things up. The glass would go up the side of the balsa, around the corner and extend to the edge of the glass laminate wing saddle. The saddle laminate would end up being 5 layers thick and the sides of the balsa would be two layers. When you are all done, the wing should release from the laminated saddle.
Use a true laminating resin to fabricate the saddle and joint. A "minute" epoxy, that is used for bonding, will perform rather poorly in this scenario. |
RE: Scratch Designed/Built Sailplane Fuselage
Good suggestions for the wing-saddle, thank you. I still have lots of other stuff to do before I tackle that job so will think on it some more, appreciate the advice.
Shaping I spent a couple of hours today rounding off the pod... http://www.scipie.com/rc/vee-gull/20121023_0022.jpg You'll notice I deliberately didn't round off the line running along the lower edge. I kinda like the ways it looks, helps accent the pod's curves... http://www.scipie.com/rc/vee-gull/20121023_0024.jpg Looks a little like a flying boat hull in some ways. Remind me not to try landing on the water though... http://www.scipie.com/rc/vee-gull/20121023_0037.jpg Canopy Those that have seen my other build threads will be familiar with my canopy making process. First I start by outlining the canopy... http://www.scipie.com/rc/vee-gull/20121023_0040.jpg Then on goes the two liter soda-bottle... http://www.scipie.com/rc/vee-gull/20121023_0042.jpg Starting along the bottom the bottle is heat-shrunk around the fuselage... http://www.scipie.com/rc/vee-gull/20121023_0048.jpg Draw some dots with a permanent marker before removing then cut her out... http://www.scipie.com/rc/vee-gull/20121023_0055.jpg Rough cut the fuselage... http://www.scipie.com/rc/vee-gull/20121023_0060.jpg Sand to the template & test fit... http://www.scipie.com/rc/vee-gull/20121023_0070.jpg Now she's starting to look more like a sailplane, getting excited. |
RE: Scratch Designed/Built Sailplane Fuselage
.............
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RE: Scratch Designed/Built Sailplane Fuselage
I reckon you could fly that thing through 30 missions to 1940's Berlin and there wouldn't be a scratch; Looks tough !
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RE: Scratch Designed/Built Sailplane Fuselage
Like my old man taught me, build it strong or don't build it at all *grin*
[ ( { brackets } ) ] So I took a leisurely stroll around the Home Depot today & stumbled upon these nifty little steal brackets... http://www.scipie.com/rc/vee-gull/20121026_0026.jpg I really like these as they have a bump that should add significant strength... http://www.scipie.com/rc/vee-gull/20121026_0010.jpg These are a little longer, no bump but they still feel really strong... http://www.scipie.com/rc/vee-gull/20121026_0008.jpg I'm liking the look of that. Simple, relatively lightweight & should be very strong... http://www.scipie.com/rc/vee-gull/20121026_0014.jpg These look like they'd work nicely too... http://www.scipie.com/rc/vee-gull/20121026_0018.jpg So not sure which of the two I'll use but I figure if I glue the brackets to a plywood wing-saddle then embed the whole thing in fiberglass I should be good to go... http://www.scipie.com/rc/vee-gull/20121026_0020.jpg The brackets are fairly lightweight but I can see maybe drilling some lightening holes here & there. That'll save some weight & give the fiberglass/epoxy more to grab a hold of. Simple, strong, sounds like a plan to me. Talk me out of it if you like. |
RE: Scratch Designed/Built Sailplane Fuselage
Forget the STEEL brackets. Simple fiberglas reinforcement would work and is going to be much lighter. Remember how the dense foamy flew? How would it have flown with additional stiffening. Or more exactly, how did it fly with additional stiffening that could have been lighter.
Read up on interference drag. It's the problem aircraft designers have with unstreamlined, 90 degree interior corners. The solution is often fairings. The fairings are perfect where you want the corner brackets for providing reinforcement that is economic of weight. Consider also a wider structure from the fuselage to the wing saddle. The present slab of plywood introduces an interference drag where it joins to the fuselage, and compounds the problem just above there where the wing is going to be strapped on. Remember the WWII Corsair? It used the identical engine the Hellcat used. The Hellcat's wing to fuselage joint had an interference drag problem along the upper connection. The Corsair, thanks to it's distinctive bent wing, joined the wing to the fuselage at right angles. Right angles aren't the perfect solution, faired joints are. Yet, the Corsair was significantly faster than the Hellcat. Everything else was basically equal. Not only was the Corsair faster, but it easily carried significantly more stores at higher speed as well. It wasn't the gull wing, because they actually are less efficient. Was it the Hellcat's less efficient wing to fuselage convergence? There really isn't anything else that differs between the two. Consider again the TWO joints. Fuselage to pylon. Pylon to wing. BTW, interference drag is also a minor consideration when deciding on where a wing's dihedral breaks should be. Every little thing can matter. |
RE: Scratch Designed/Built Sailplane Fuselage
Stubborn Bugger
I've not weighed the brackets but they're nothing I'm worried about, especially once I've "Swiss-cheesed" them. I'm getting lots of suggestions to just use fiberglass & I do intend to FG the heck out of the joint but I want something else in there too. Fiberglass is good stuff no doubt but from experience I know it also has its limitations. For example look at what happened to my fiberglass four meter sailplane after a moderately bumpy landing... http://www.scipie.com/rc/vee-gull/20120821_0005.jpg Fiberglass is rigid & cracks, metal is substantially inflexible but when it does move it just bends. I think a combo of both will be perfect for this application. I know you folks already know this stuff but I'd like to explain my thinking here: This all comes down to leverage. Archimedes famously said, "If you give me a lever long enough and a place to stand, I can move the world." While I have no Earth moving aspirations, my understanding is because I have just 1/4" of pylon to work with here Vs a normal fuselage with its wide wing mounting area, there's going to be a lot more force on this joint than usual... http://www.scipie.com/rc/vee-gull/3D...ng_021_700.jpg I did a little math & was astonished to learn... http://www.scipie.com/rc/vee-gull/3D...ng_020_700.jpg So with that in mind, yeah I'm going to stick some steal in there along with some fiber-glassing. So here's a rough diagram of what I'm building... http://www.scipie.com/rc/vee-gull/3D...ng_022_700.jpg Anyway not sure exactly when I'll get to this. Situated directly in the path of hurricane Sandy I'm expecting some "interesting" weather over the next few days. At the very least I expect I'll lose power for a while, will have to see how I feel about working in the dark *grin*. Anyway see you all later this week I hope. Stay safe. |
RE: Scratch Designed/Built Sailplane Fuselage
ORIGINAL: Nodd Stubborn Bugger I've not weighed the brackets but they're nothing I'm worried about, especially once I've ''Swiss-cheesed'' them. I'm getting lots of suggestions to just use fiberglass & I do intend to FG the heck out of the joint but I want something else in there too. Fiberglass is good stuff no doubt but from experience I know it also has its limitations. For example look at what happened to my fiberglass four meter sailplane after a moderately bumpy landing... [img][/img] Fiberglass is rigid & cracks, metal is substantially inflexible but when it does move it just bends. I think a combo of both will be perfect for this application. Anyway, some fiberglass IS rigid and cracks. Very few modelers make theirs with polyester resin. What we reinforce with it really isn't going to be brittle. And that's not the real problem here. And it's not the more important detail of the structure you're wanting to create either. Just like having carbon fiber reinforcement anywhere in a model like a glider that normally flexes visibly in lots of places, having absolutely rigid structures anywhere in the glider fights that normal bending. Where the absolutely rigid support stops is where you're going to find your next crash damage. And sometimes it happens very shortly before the crash. But what the heck. I'm not a terminally stubborn bugger. I'd like to see how your steel works out for you. I'll still suggest stubbornly that there is absolutely no value in having all that steel in the brackets. Drilling more holes in them than there will be steel left really would be worth the effort. BTW, if your fibergalss 4M sailplane broke like the picture shows as a result of a moderately bumpy landing, I got twenty bucks says it was made with polyester resin. And the exposed section of cloth at the forward most damage suggests polyester as well. Good thing is that epoxying inside the fuselage from the wing mount forward with a couple of layers of cloth will cover the area where the stress risers from the impact did the most damage, and you'll be not only reinforcing where the stress won the previous battle, but you'll be moving the place where the next stress risers might happen farther out, reducing their leverage. |
RE: Scratch Designed/Built Sailplane Fuselage
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The real problem isn't at the very center of the wing, but everywhere along the wing that resists the wing from naturally dealing with the forces from root to tip.
Using the 208 lbs for a start, where the unmovable cradle stops a couple of inches out from the center of the wing there is going to be pretty close to 208 lbs of force trying to snap that wing off right there where the most vicious stress riser will be. There will also be some mean stress risers out on the dihedral joint outboard on the wing. Everywhere we reinforce the hell out of things, those things experience hell when the entire system is stressed. The hell will be focused where the flexing is stopped. BTW, the saddle will of course be strong enough to shift a lot of stress elsewhere. (the stress isn't absorbed by absolutely rigid structures) So where could the stress go? How about where the pylon enters the fuselage? and there is no steel to completely pass the stress to somewhere else. |
RE: Scratch Designed/Built Sailplane Fuselage
Hey, Fairfield is right on the ocean. Hope you live on a hill.
All kidding aside, hope the really important things work out for you and family. |
RE: Scratch Designed/Built Sailplane Fuselage
I should probably clarify the "Stubborn Bugger" title is in reference to my die-hard insistence on using these metal brackets. I'm the stubborn bugger not you. Re-reading my post I can see how that'd easily be taken the other way which was not my intent. My other mirror threads are worded exactly the same (RC Groups, Wattflyer). My apologies.
Yeah I'm no expert when it comes to fiberglass but I've sure seen my fair share of beat up, cracked, weathered, & UV'ed to death glass in my day. Just to add to my distrust my flying buddy just shattered his rather expensive DG 1000's glass fuselage yesterday during an aborted aerotow. The stuff while lightweight is far from indestructible. I like indestructible. After spending a lot of time building a bullet-proof Kevlar wrapped carbon-fiber wing-spar, I think it'd be daft to not continue at least some level of overkill in joining that wing to the fuselage. A strong wing does me no good if its not attached to the plane *grin* As far as drilling holes in the brackets to keep them light, if you notice in my last post's first sentence I cryptically alluded to doing just that (Swiss-cheesed). My four meter Discus has been repaired & is flying great. Two layers of heavy glass inside fixed her up. Anyway enough time spent explaining my self. Time to get back to the workshop. |
RE: Scratch Designed/Built Sailplane Fuselage
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