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RE: Piper Cub Sailplane
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RE: Piper Cub Sailplane
That's a great article there Soarrich, thanks.
ORIGINAL: rhall999 PS....Forgot to mention, the nice shiny red tail on the glider is because the balsa tail is covered in Monokote. Graphics The funny thing about spray painting is you spending hours on end masking & then about 30 seconds spraying... http://www.scipie.com/rc/cublider/20121001_0001.jpg Yet another template, aren't computers great?.. http://www.scipie.com/rc/cublider/20121001_0003.jpg The idea here is to carefully cut through both the template & the masking tape below... http://www.scipie.com/rc/cublider/20121001_0006.jpg Peal away the excess tape... http://www.scipie.com/rc/cublider/20121001_0010.jpg Add the window lines... http://www.scipie.com/rc/cublider/20121001_0008.jpg Then wrap her up like a last minute birthday present... http://www.scipie.com/rc/cublider/20121001_0012.jpg 20 seconds of spraying... http://www.scipie.com/rc/cublider/20121001_0017.jpg And we have windows!.. http://www.scipie.com/rc/cublider/20121001_0020.jpg We're not done yet though. Next is the signature Cub, Flash Gordon lightning bolt... http://www.scipie.com/rc/cublider/20121001_0025.jpg There we have it (the yellow doesn't quite match but what can ya do?)... http://www.scipie.com/rc/cublider/20121001_0040.jpg Looking pretty snazzy in a Cub sorta way... http://www.scipie.com/rc/cublider/20121001_0052.jpg |
RE: Piper Cub Sailplane
SWEET!! Would be great if some of the Manufacturers would take notice. Something for after accidents that happen.
Lookin good............ |
RE: Piper Cub Sailplane
Looks great!<div>I wonder though how it'll perform in the air. It looks like tail could be on a short side and that may bring some stability problem.</div><div>cheers</div><div>Mark</div>
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RE: Piper Cub Sailplane
Your concerns are valid there Mark, this is a very short-coupled design. I'm going for a comical, almost cartoonish, look. I'll need to watch the CG & trim carefully but she flies well on my simulator, if not a tad pitch sensitive. Hopefully a little expo on the elevator will tame that. Kinda funny a guy named longsoar has issues with my shortsoar sailplane :-P
ORIGINAL: Tinkrerpilot SWEET!! Would be great if some of the Manufacturers would take notice. Something for after accidents that happen. Lookin good............ |
RE: Piper Cub Sailplane
1 Attachment(s)
Ahh okay yeah I was looking at the reflection in the tail & thinking how the heck did he get a showroom like shine on a foamie *smile* Your "Cub Glider" is looking awesome. Personally, I don't think that the short coupled tail will be too much of an issue.......providing the CG is correct and the throws are correct (ie: I would suspect that you will not want a lot of throw on the elevator). After all, My Sig Wonder is even more short coupled than the Cub glider, and it flies great.TheWonderjust has a really small elevator with very little throw, and it has lots of authority. Based on my experience, Iwould say that all you will need to do is take care to get the CG in the right place, maybe even a touch forward for the first flights, and then tune the CG and elevator throws to get the flight characteristics you want. Here is a nice short coupled sailplane....full scale. If you want to see an REALLYshort coupled glider, google "Fauvle AV-36." Drawing belowhttp://www.rcuniverse.com/forum/js/f...ades_smile.gif These both fly, fairly well I am told. |
RE: Piper Cub Sailplane
The Fauvel is a flying-wing, which I supose is the ultimate short-coupled airframe. I've flown a few wings & they can be a challenge to setup correctly but once dialed in, I've found they're rock solid. The other two designs you mentioned are in a gray area, sorta flying-wing, sorta short-coupled.
Yeah I think getting the CG set correctly will be key. I've had great success using this online CG calculator. Its been spot-on for a number of my planes, I trust it completely. Well thanks for the vote of confidence, seeing those birds puts my mind to rest somewhat. The Cub will fly again! |
RE: Piper Cub Sailplane
The Tail
After a little head-scratching I came up with an effective way of squaring up the fuselage to my workbench before attaching the tail... http://www.scipie.com/rc/cublider/20121002_0015.jpg This should result in a nice level tail that should align with the wing once that's done (waiting on a longer CF wing-rod to arrive)... http://www.scipie.com/rc/cublider/20121002_0011.jpg The rudder hinge was damaged in a nose-over a while back. I removed it so I could make a proper repair but having it off of there got me to thinking, maybe I should take this opportunity to enlarge the rudder a little... http://www.scipie.com/rc/cublider/20121002_0029.jpg A fat bulbous nose section, a short-coupled tail-moment & an extended wing are all conspiring to make this puppy a little lacking in yaw authority. More rudder area can only help. So I think that's what I'm going to do, make a slightly larger rudder... http://www.scipie.com/rc/cublider/illustration_002.jpg Now that the tail's on I can move ahead & get the rudder & elevator servos mounted & functional. That'll have to wait for the glue to dry though, not sure I'll get to that tonight. We'll have to see. |
RE: Piper Cub Sailplane
BIG Rudder
Well I got a little more done tonight after all. Here's the new enlarged rudder... http://www.scipie.com/rc/cublider/20121002_0030.jpg Figuring a larger surface area will translate into more stress I'm reinforcing the control-horn/tail-wheel area... http://www.scipie.com/rc/cublider/20121002_0035.jpg Reinforcing glued in place... http://www.scipie.com/rc/cublider/20121002_0039.jpg Test fit... http://www.scipie.com/rc/cublider/20121002_0043.jpg I think that should help her track nicely while maintaining the scale tail's looks... http://www.scipie.com/rc/cublider/20121002_0055.jpg I'll put a few coats of paint on her (won't bore you folks with that process) & that'll do for today. |
RE: Piper Cub Sailplane
rhall, Nodd,<div>I just wanted to add my nickel here. Those flying wings usually use special airfoil to be stable. That's the only reason I voiced my opinion.</div><div>As I mentioned - it may be a challenge to fly the same airfoil on a shorter tail.</div><div></div><div>Nodd, those glasses should've been filledequallywith Jack Daniels or so for exact tail alignment :)and we're missing your nice dishes! Why did you disappoint us with something so unpleasant :D?</div><div>cheers</div><div>Mark</div>
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RE: Piper Cub Sailplane
ORIGINAL: longsoar rhall, Nodd,<div>I just wanted to add my nickel here. Those flying wings usually use special airfoil to be stable. That's the only reason I voiced my opinion.</div><div>As I mentioned - it may be a challenge to fly the same airfoil on a shorter tail.</div><div></div><div>Nodd, those glasses should've been filledequallywith Jack Daniels or so for exact tail alignment :)and we're missing your nice dishes! Why did you disappoint us with something so unpleasant :D?</div><div>cheers</div><div>Mark</div> I love these threads. Reading with great fascination. |
RE: Piper Cub Sailplane
Got the tail-wheel installed...
http://www.scipie.com/rc/cublider/20121003_0004.jpg Wing Bolts I used rubber bands to hold the wings on for my last scratch build. I'm still getting grief from my subscribers for that decision. So you'll be happy to hear I'm going with nylon wing bolts this time. Here's a mounting block I came up with for the rear mount... http://www.scipie.com/rc/cublider/20121003_0007.jpg The two dowels will be inserted into holes drilled deep into the fuselage. Its my hope this'll securely affix the block to the fuselage... http://www.scipie.com/rc/cublider/20121003_0013.jpg Here's the cutouts in the fuselage, ready to receive the block... http://www.scipie.com/rc/cublider/20121003_0011.jpg Secured with ample amounts of Gorilla Glue... http://www.scipie.com/rc/cublider/20121003_0023.jpg I considered using the peg method for the front but decided instead to just go with a second nylon blot. There's not enough "meat" around the front location to use the same dowel setup as the rear so I came up with this interlocking design... http://www.scipie.com/rc/cublider/20121003_0029.jpg As you can see the two pointy pieces of ply hold the block in place... http://www.scipie.com/rc/cublider/20121003_0035.jpg I made some cutouts in the fuselage... http://www.scipie.com/rc/cublider/20121003_0031.jpg And in she goes... http://www.scipie.com/rc/cublider/20121003_0039.jpg Its movie night tonight, gonna watch the Avengers with a few friends on my home theater. So that's all for now. |
RE: Piper Cub Sailplane
The Wing
A lot of running out & doing chores today so I didn't get much time to play in the workshop. I did want to get the wing together though as my new, longer wing-rod has arrived from rcfoam.com... http://www.scipie.com/rc/cublider/20121004_0018.jpg Once again I raided the kitchen cabinets, used these glasses to support the wing, plates on top to weight it down... http://www.scipie.com/rc/cublider/20121004_0033.jpg I used Gorilla Glue once again. Not only is it seriously strong glue, it has the added bonus of expanding as it cures. That takes care of what to do about the wing-rod slot... http://www.scipie.com/rc/cublider/20121004_0036.jpg Once that's dry I'll sand the foaming glue flush with the wing. So I'm going to let this sit overnight & let the glue do its thing... http://www.scipie.com/rc/cublider/20121004_0023.jpg Spending 10 minutes to clear the clutter from my work-bench wouldn't hurt too *grin* |
RE: Piper Cub Sailplane
You are simply haveing WAY too much fun... :D
I'm really looking forward to the flight vids. The little pocket soarer would be idea for dropping from the belly of some big carrier model. |
RE: Piper Cub Sailplane
Fun, fun, fun is right, I'm having a blast with this build. A nice low stress, not too serious project to while away the time. Just what I needed.
She's starting to look like an airplane. Well the Gorilla Glue filled the wing-rod slot alright but geesh does that ever looks ugly... http://www.scipie.com/rc/cublider/20121005_0002.jpg We'll address that shortly. Flaps? Well this glider already has everything but the kitchen sink, so why not flaps too? I marked out where I figured they might go... http://www.scipie.com/rc/cublider/20121005_0006.jpg I picked up this nifty tool for cutting strips of balsa but discovered it's also pretty handy for making nice 90° cuts in foam... http://www.scipie.com/rc/cublider/20121005_0008.jpg So here's our flaps. They should come in handy for making precision landings & because this puppy is going to be so incredibly good at thermalling, they'll be essential for getting down out of boomers ;-P http://www.scipie.com/rc/cublider/20121005_0011.jpg Test fitting the two flap servos... http://www.scipie.com/rc/cublider/20121005_0020.jpg That brings us up to seven servos in this dinky plane. She's a lean mean full-house machine! Wing meet fuselage, fuselage meet wing Time to get this wing mounted up. I needed something more than just Home Depot foam to keep the nylon wing-bolts from ripping through the wing. I cut some scrap carbon fiber into short lengths & cut recessed slots in the wing... http://www.scipie.com/rc/cublider/20121005_0013.jpg While I had the Dremal tool out I also cleaned out some of that yucky looking Gorilla Glue from the wing-rod slot... http://www.scipie.com/rc/cublider/20121005_0018.jpg Glued the carbon fiber into their slots... http://www.scipie.com/rc/cublider/20121005_0026.jpg Next I needed to drill holes for the nylon wing-bolts but where exactly should the holes go? Here's a neat trick I learned. Tape some Mylar or something similar to the fuselage & mark the wing-bolt location with a marker... http://www.scipie.com/rc/cublider/20121005_0034.jpg Do the same for the forward location... http://www.scipie.com/rc/cublider/20121005_0041.jpg Flip the Mylar back & install the wing. Measure everything so the wing is exactly centered & square to the fuselage... http://www.scipie.com/rc/cublider/20121005_0044.jpg X marks the spot. Drill away... http://www.scipie.com/rc/cublider/20121005_0051.jpg I probably don't have to mention that carbon fiber dust is nasty stuff. I use a mask & clean up the work area with a damp paper towel immediately afterwards. Lubricating the nylon bolts (mind out of the gutter gentlemen)... http://www.scipie.com/rc/cublider/20121005_0056.jpg I wanted a way to locate the wing on the fuselage so that lining up the wing-bolts would be a snap. The solution was to add a small block that'd index the fuselage... http://www.scipie.com/rc/cublider/20121005_0060.jpg I glued that to the wing then gave her a test fit... http://www.scipie.com/rc/cublider/20121005_0078.jpg Slots, slots & more slots. Time to do something about those rather un-aerodynamic slots in the top of my wing... http://www.scipie.com/rc/cublider/20121005_0068.jpg Glued scrap foam into the slots... http://www.scipie.com/rc/cublider/20121005_0072.jpg A little sanding & we're looking good... http://www.scipie.com/rc/cublider/20121005_0075.jpg Pretty pleased with that session, got a fair amount accomplished... http://www.scipie.com/rc/cublider/20121005_0080.jpg Oh yeah she's starting to look like an airplane alright... http://www.scipie.com/rc/cublider/20121005_0082.jpg A cute goofy airplane that is. Now I'm started to get excited, there's light at the end of the tunnel. She'll be taring up the sky soon enough! |
RE: Piper Cub Sailplane
Painting the wing center section...
http://www.scipie.com/rc/cublider/20121006_0077.jpg This is no way to start an aerotow. With the wheel more or less at the CG I expect she'll flop forward like this during landings & tows. Not good... http://www.scipie.com/rc/cublider/illustration_003.jpg So naturally the solution is an aluminum bar, a coat-hanger & a piece of old rubber piping... http://www.scipie.com/rc/cublider/20121006_0081.jpg If you've not guessed yet, yeap I'm making a nose skid... http://www.scipie.com/rc/cublider/20121006_0083.jpg The coat-hanger I bent into a U shape, that'll be inserted into the nose & act as an anchor for the front of the skid. The other hardware will attach the skid to the anchor... http://www.scipie.com/rc/cublider/20121006_0087.jpg On the rear of the skid I'm bolting this L shaped piece of scrap aluminum... http://www.scipie.com/rc/cublider/20121006_0089.jpg Here's the skid partially assembled... http://www.scipie.com/rc/cublider/20121006_0091.jpg The coat-hanger wires are glued deep into the nose... http://www.scipie.com/rc/cublider/20121006_0113.jpg The rear is bolted to a piece of rubber hose... http://www.scipie.com/rc/cublider/20121006_0108.jpg The L shaped piece of aluminum is to allow a winch line to be slipped over the end of the skid without getting stuck under the rubber pipe... http://www.scipie.com/rc/cublider/20121006_0111.jpg Well that should help with ground handling, no sticking her nose in the dirt... http://www.scipie.com/rc/cublider/20121006_0104.jpg I think it looks pretty cool too, something you don't see every day... http://www.scipie.com/rc/cublider/20121006_0119.jpg Next I hope to get the flaps & tail-feathers hooked up & functioning. Will post more soon. |
RE: Piper Cub Sailplane
What's with the $3 servos?
If I could afford good servos, I probably wouldn't be working with an old wrecked Cub *grin*... http://www.scipie.com/rc/cublider/20121008_0056.jpg These are kinda oddball mismatched servos that I had laying around... http://www.scipie.com/rc/cublider/20121008_0059.jpg Cool, the tail is functional & working nicely... http://www.scipie.com/rc/cublider/20121009_0003.jpg Flaps I've always wanted inboard flaperons (the flaps also move with the ailerons). So basically I have full-span ailerons with the inboard section pulling double duty as flaps. To achieve this I needed to bevel the flaps a tad so that they could move upwards as well as down... http://www.scipie.com/rc/cublider/20121008_0034.jpg I'm trying something a little different here by sticking CA hinges directly to the bottom of the wing instead of into a slot. I'm not using CA glue either as for this application, I need something less brittle. This Welder glue is awesome stuff, its kinda like industrial strength contact cement... http://www.scipie.com/rc/cublider/20121008_0041.jpg With the hinges on the bottom of the wing the flaps have unlimited downward travel. And due to the slight bevel they can also move upwards a few degrees... http://www.scipie.com/rc/cublider/20121008_0045.jpg Hooked up the two flap servos... http://www.scipie.com/rc/cublider/20121008_0053.jpg I still need to mess with the mixing but the wing's four control surfaces are all working... http://www.scipie.com/rc/cublider/20121009_0022.jpg This should be a fun wing, lots of opportunity to mess with flight modes, flaps, crow & other unnecessarily complicated stuff... http://www.scipie.com/rc/cublider/20121009_0019.jpg We're getting close now, not much more to do. |
RE: Piper Cub Sailplane
The last 10% takes 90% of the time
While that's generally true, wrapping up the last odds & ends went smoothly today. The first order of business was to install the radio spaghetti... http://www.scipie.com/rc/cublider/20121009_0007.jpg I hate disturbing the receiver by plugging/un-plugging wires when removing the wing, so I made a bunch of servo extensions. This allows me to plug the wing into those instead of messing with the receiver each time... http://www.scipie.com/rc/cublider/20121009_0004.jpg With all these wires I color coded everything so I don't have to think at the field. We should all avoid thinking whenever possible... http://www.scipie.com/rc/cublider/20121009_0013.jpg A couple of rare-earth magnets hold the battery hatch in place... http://www.scipie.com/rc/cublider/20121009_0017.jpg She was tail heavy when I first stuck her up on the balance stand, needing 6oz to level her out at 10% static margin... http://www.scipie.com/rc/cublider/20121009_0032.jpg To better help balance her I removed the nifty steerable tail wheel. It was useless anyway as the plane rests on the nose skid, with the tail up in the air... http://www.scipie.com/rc/cublider/20121009_0019x.jpg That translated into a few less ounces needed in the nose. I also moved the CG back to 5% static margin & she balanced with just 3 ounces. Much better... http://www.scipie.com/rc/cublider/20121009_0046.jpg Added a custom Cub logo to the tail... http://www.scipie.com/rc/cublider/20121009_0051.jpg Well she's all ready to go. Maiden flight time tomorrow, woohoo! Wish me luck. http://www.scipie.com/rc/cublider/20121009_0061.jpg |
RE: Piper Cub Sailplane
Almost forgot
I know you folks probably want a few stats... <blockquote>Wingspan: 60.25 in / 1530 mm Weight: 40.9 oz / 1159 g Wing Area: 465 sq.in Wing Loading: 11.9 oz/sq.ft / 36 g/sq.dm Cubic Loading: 5.93 oz/cubic.ft Stall Speed: 17.1 mph / 27.5 km/h </blockquote>She's about what I expected, not exactly a floater but not a lead-brick either. Somewhere in the middle for a sailplane. We'll find out how she performs tomorrow. |
RE: Piper Cub Sailplane
It looks like the maiden will have to wait, its raining today :-(
On the plus side this gives me time to install the wing struts. |
RE: Piper Cub Sailplane
Struts
It wouldn't be a Cub without the wing struts. I figured the wheel support was a good strong spot to start with... http://www.scipie.com/rc/cublider/20121010_0027.jpg For the wing mount location I created these hard-points... http://www.scipie.com/rc/cublider/20121010_0029.jpg Cut a slot... http://www.scipie.com/rc/cublider/20121011_0002.jpg Glued & mounted. The struts are lightweight aluminum struts available at most hobby stores. The blue tape is there temporary to keep the glue from getting all over... http://www.scipie.com/rc/cublider/20121011_0007.jpg Now that's looking more Cub-like... http://www.scipie.com/rc/cublider/20121011_0020.jpg Possible maiden tomorrow, although you've heard that one before. |
RE: Piper Cub Sailplane
<font size="6"><font size="3">YouTube video, click to watch...</font>
MAIDEN FLIGHT VIDEO</font> <font size="4">Flight Report </font>(spoiler alert - watch video first) Well as you can see that didn't go as well as I'd hoped although not a big surprise either, given the deliberately compromised design. Here's my thoughts... Issue 1 The placement of my ridiculously big wheel sticking way too far out below the fuselage & positioned right at the CG doomed the aerotow. The nose-skid helped but not enough to keep the plane level & stable while towing. A lower profile wheel positioned properly would let her roll smoothly without generating gobs of drag for the poor tow-plane. Issue 2 Everyone who picks her up is surprised at the weight. She's a heavy bugger, that combined with the short-coupled tail moment makes for some "interesting" flying. I think she'll be manageable if only I can get her in the air & moving along at a good clip. Issue 3 Watching the alarming angle of attack during the high-start launch, I'm wondering if maybe moving the two-hook location further forward would help. Other factors such as CG & elevator trim may have contributed to the problem too. The Next Step After I make the repairs I think I'm going to remove the wheel & nose-skid & just let her slide along on her belly. I'll see if that helps with the ground handling. I may also remove the wing-struts at least until I have a few more test flights under my belt. With the nose-skid gone I can also try moving the tow-hook location forward a little. Seriously this isn't Serious While this may come across as a poor excuse for blatantly bad design, my main drive behind this build was to learn about working with foam. This project has in that sense been a success. I'm now confident enough to proceed with some more serious designs. That said I'm not done with this Cub though, at least not yet. I'm pretty sure I can get her flying. Anyway bring on the theories, suggestions & those inevitable "I told you so's". I have it coming & I welcome it all. Fun Fun. |
RE: Piper Cub Sailplane
You're turning onto the right track now... Glue a spruce strip along the belly, or use a lighter aluminum strip. Steam can make the wood bend as easy as the aluminum does naturally. The spruce dries out and is rigid, the aluminum still bends easily.
Same thought leads to using hard balsa in place of the CF hunks for reinforcing. Thick CF really isn't needed. Thin CF isn't needed either. It's pretty amazing how so many of us go right for the CF when there are hundreds of much cheaper, as light or lighter, easier to find, better suited to the requirement, easier to use materials. Used to work in a plant that had a big sign "Add more lightness." (sign was in the museum hallway between Building 1 and Design building) It'd be great to see your excellent presentation skill document the building of Cub II, employing the lessons learned. It really would help budding designers to see how to make foam fly well. BTW, no way do you deserve any 'I told you sos' or such. You're doing the best presentations seen around the internet. |
RE: Piper Cub Sailplane
Nose up on highstart was towhook placement as you puzzled over. The highstart pulls "down", the wing lifts "up". The two forces try to line up behind the towline. If the pull is too far aft.....
Sorta the same with the drag on the wheel versus the pull on the towline connection. |
RE: Piper Cub Sailplane
The nose down on tow is probably a torque deal. Drag from the footprint of the tire is at ground zero. Towhook was some inches above ground zero. Tow force will try to line up with the source of the most drag. So the footprint tries to be directly behind the towhook, or the tow point will try to move down to get in line ahead of the drag.
Since the plane was forced into a major nose down pitch, the tow plane was basically trying to pull the planform view through the air. The tow plane could be strong enough to suffice if the hook location was more in line with the drag. Interesting aside is the wing drag was zip compared to the drag of the tire, with maybe a touch of help from the stuts in the grass. Were you guys taking off at an angle to the wind? The flag looked like the wind was coming from 10 o'clock or so. |
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