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Light wing build

The Wipaire 2000 lb kit allows 13 rib wings. As I recall hearing, Paul Claas's 160 hp Alpha Cub has one 13 rib wing and the other is 16 rib. I think the point when Piper went from a 138 mph to a 153 mph "never exceed speed" was when the PA-18-150 got 16 ribs.
Darrel
 
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So my new cub does about 85/87 mph so I should have went with a 10 rib wing---Damn to late now.
 
I'm planning on flaps (standard size and fabric covered control surfaces) , solid gear with big soft wheels was mentioned. Has anyone ever tried that? If so did straight gear weight savings offset wheel weight? Where the leading edge doesn't wrap all the way I assume it's only the bottom that doesn't go all the way and the top still has a downward 90* (actually 105* I think)flange attached to the spar cap with 3 pk screws in each bay. I saw in the Stewarts video a wing (Colt? I think) that they covered and some of the LE had a partial wrap. I believe it was the one panel outboard of the strut. So I'm thinking .016 along the leading edge except tank bay 32"? which will be .020 and .025 along the whole trailing edge false spar. The aluminum D&E spars with Schneider ribs will be laid out 13 ribs per wing per buggs site. I will purchase the sheet aluminum for the TE and LE next week and bend it myself. I would still appreciate more discussion about the tank area, strut through the tank or bottom "torque" plate. I know bugs likes it and I like the idea of not having the strut inside the gas tank. BUT spars fail by twisting I have read and since the support is only on the bottom is it as strong as the strut? Also I'm wondering if that big piece of .040 sheet is as light as the strut and pipe thru the tank. I can answer that with a little research. DW if I may ask how did you decide how much material and where to cut out the spar web? When I purchased my spars I had 6' of "H" spar spacer material sent along. I have noticed in several pictures and in the Piper drawings that the spar web attach fitting to the fuse wing hangers looks to be the same "H" spacer aluminum material. Am I correct in that observation? I originally thought there was an outside re-inforcing plate of steel on both sides of the spar web??>
Here is an interesting wing failure test: http://www.youtube.com/watch?v=Ai2HmvAXcU0 . Whats interesting is it fails almost everywhere simultaniously. That means they are not carrying any extra weight around for the life of the aircraft when there is a weak link. That would be the gold standard. Dave C. I know building light and compromising is less safe and not as strong. The FAA made the weight rules and life established my budget. I figure I'll rebuild wood or CC ribs after I ground loop this thing in the first ten hours after I get my Tail dragger endorsment. Seriously that is why I'm getting as many thoughts as I can on this. I don't mean to dismiss any ideas and am weighing all of them. If I had my druthers I'd be building a CC kit. Thanks for all the participation in this thread and Merry Christmas ...dave
 
My point about the CC wing was simply that not everyone is aware that very lightly built stuff is great for flying, but can't take a little 'hangar rash' or ding like the "heavy" stock stuff. And certainly cannot be flipped back rightsideup, re-lift-strutted and propped and reflown like a SuperCub. It is NOT NOT NOT a safety issue, the light airplanes are plenty SAFE!

qsmx440, consider that every bit of your struggle to save weight elsewhere is offset by the ribs you have chosen.

What do YOU weigh? Can you save there? How about less fuel, fewer or no interior panels, less floor, fewer instruments, lighter prop, no boarding or fueling steps, fabric seat bottoms rather than wood or composite or springs, no cowling, minimal baggage area, fewer windows, remove the "extra" fuselage bracing diagonals that some folks have added to a Cub.

The snowmachine racing crowd once echo'ed "...anywhere there is steel, use aluminum..." to save weight. I think we skipped that and have moved right to Carbon Composites.

The partial leading edge wrap I had in mind is identical to the SuperCub leading edge outboard section. It does not wrap to the spar, neither top, nor bottom..........carbon fiber skin would be great in this location.

I hope this is food to promote more thinking.DAVE
 
Roger, they work for this unflapped Cuby.

I did some testing and posted the data some time ago. The improvements are for real. I'd like to do more testing to get more accurate or precise data.

D
 
What about a carbon fiber leading edge, has anybody messed with that or carbon fiber ribs, what about the fuel tank.

Glenn
 
What about a carbon fiber leading edge, has anybody messed with that or carbon fiber ribs, what about the fuel tank.

Glenn

If you a SC.org member go to photo gallery's and search user name "gander". He has some great pictures of CF work. Ribs and leading edge of carbon fiber. This is kind of an example of what I said in the first post. The pictures are good and I found some of his posts talking about the build but I wasn't able to find out how it flew or the weight or any specs. I think I recall the wings came in at 66# but I really don't remember. Looked strong as heck.
 
What about a carbon fiber leading edge

Like this??:lol:

CF Leading Edge Profile.jpg

It has 45 deg weave sandwich that gives it incredible torsional stiffness, thereby eliminating nose ribs. It can be bonded or riveted, and can be joined to make one long leading edge. Heat the seam to release the bonding tape between pieces to disconnect the for repairs.
 

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Just when a guy begins to get this stuff straight in his head, he gets "Bushwhacked". No noseribs??? Nice, very Nice ;-)
 
Problem is, Steve, that that the tooling is about $4200!! Making them to sell for $300 a 63" piece makes for an expensive wing. Working on a better price right now - should be able to make the pieces for < $200 each and hopefully save on some tooling costs.
 
Dammit Chris. I was ordering aluminum sheet on monday, think I'll wait. Hmmmn 2,4,6, x 2. yep that should be enough so 1200 + 60-70 shipping... maybe cheap shipping since light... hmmm 1270.. yep I'm down for that.. Seriously. though I would want to hear,a real good discussion about dynamic strength:cycling, attachment, are the rest of the wing parts overstressed because of LE stiffness, etc. Not criticising just trying to be careful. One of the reasons I'm building to cub plans is it's tried and true and the problems are known. BUT I would be willing to try something like this in a heartbeat if certain questions were answered. 1200 a set would be a good target price in my case and I'm one of the cheapest consumers around. Wait, wait, what is the weight savings? Wow key point. That would be a real big point with me. Like I said earlier, before I spend money on saving 6# in the wing at CG, I would spend it on the nose (start at spinner and work back) since 6# forward of CG will benifit me more. Another thought for you Chris: wouldn't a "no ribs" but really strong flap/aileron reverse cove false spar with molded in hanger supports be a better (though not as flashy) CF build also? Maybe both LE and TE. I bet if you got this done and it saved 30# folks would be ripping their exp wings apart to add these and since building to 1320# is just slightly out of reach (I think carbon cub saves a 200# practical) I think this would be a great profit center. Just realized Steve said all of what I just said with "hope your ready to ship" :)
 
One more thought on this product: The nose ribs add another attach point on the front of the spar cap. I would think those attachment points would have added strength to the spar to resist the "failure mode, twisting. Maybe an inside added flange that the builder could notch out except at each location where the "old" nose ribs would have been or just leave the whole thing? How about aileron/flap leading edges. Cheaper for a first product? Easier to engineer without catastrofic consequences? Failure mode likely to happen over time etc. If I had any of these I wouldn't want to cover them. Almost as good as bush wheels for "man mode" ;-)
 
Roger, Your wing looks awesome. I too am a wood wing fan. Some of the highest performance aircraft in that weight class have had wood spars and some with wood ribs also for years. The Bellanca Decathlon is a high speed, high G, aerobatic ship with a spar that's pretty close to the Champ spar of 70 years ago. Wood is good. What engine will be on your ship Roger? I guess my question is if you're going to build a 150+ hp SC with flaps, would you use the typical wood spar Piper internal bracing hardware? In other words would you use the J3/J5 style compression members and trammeling wire and so on? Would you need to beef anything up?

Good Job Roger, looks great.
 
Thanks. I just like wood wings. They have a lot of give where the alum take a set. I put alum Dakota Cub wings on my first PA11 and it ended up heavy. Great Flyer, but heavy. Have a 1940 J3 with wood spars, and alum ribs. I think wood spars and ribs are about as strong as you can get and yes I would go wood on a experimental SC. I call my first one a PA11 because it doesn't have flaps and has the long front spar. Other than that, I wouldn't hesitate to hang a 180 on it. I fly it at 2000+ all the time with a 0-200 with a 588 cam and 9.5/1 pistons. Same engine I am putting in this one. Don't think you need the extra ribs unless you plan on going fast. Can't tell much difference in the bulge on top or the indent on the bott from 1200# to 2100#. I do use SC struts and forks though. I really don't see any use for anything over a 0-200 though as it is just going to burn more gas. I can haul all I can pack in it as it is. Also I run a 4 into 1 exhaust with no muffler so I can make as much noise as a big plane. I think the extra noise helps you get off the water quicker.
 
We, too, do not want to stray too ar from the Piper plans for the same reason. My thinking on Carbon Fiber is that Piper didnlt have it back then, or they would have used it!

The elimination of the nose ribs is due to the torsional stiffness of the LE. By being able to carry some load on the LE, you should be able get by without them.

Using the diagonal drag/compression arrangment saves some weight too and take the spars out of tension mode - not so sure how much weight is saved, but our no-flap, 15' wing panel weighs 58 lbs w/o aileron. Hard to do an apples to apples comparison because it is different.

Mike O' has been my weight-savings inspiration, and everything is being scrutinized. No if I could only eat right!! :oops:

working on a nice wing tip and want to do the false spars also. One thing at a time!
 
Jeeze Chris. Everyone does wingtips but carbon fiber leading edges?? :) I'm being selfish. I want em tested and ready to ship next week! I agree, Piper would have used them if they'd had em..
 
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D.A.
I am building a wood wing for my 2+2/PA14, same as Rogers but with flaps. The flaps and ailerons will also be made from wood. The only reinforcement I have added is a second piece of ply 3" x 4-1/2" x 1/16" on the inside of the spars at each of the aileron and flap hangers. The leading edge will be 1/16" ply, extending all the way to the spar top and bottom. I will have to build up the spars to the top and bottom of the ribs with cap strip material (1/4" x 1/4" spruce) but that will be pretty light. Flap hardware will be the same as the Super Cub with the hangers being modified J3 wood spar aileron hangers. Right now, the wing seems very light. I will weigh the wing after the leading edge and cove are in place in a few weeks.
Marty 57

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Marty57
 

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That wing build is looking good Marty. It's a little hard to believe (but I do accept) that the wood wing is lighter considering the spars. I can see that the ribs would be lighter and I also can see there are a lot less parts in the compression struts/drag wires. What did your spars weigh bare if you have that figure? I'll try to weigh one of my bare aluminum spars today if I get to the hangar. Other than the ribs the wood wings you are building appear to have a lower parts count (braces etc) than the aluminum ones. Ordered a set of parts from Dakota yesterday for one compression strut (very helpful folks). I'm gonna try to make the aluminum inserts (plugs) when I get the square tube to check dimensions. I gotta go edit my above post to Chris on 12-26 since you have bumped this thread. Don't know what I was thinking posting that business about carbon fiber LE and it's attachment to the spar. Doesn't make sense when I read it now?
 
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My next task will be to find a clear myler film duarable enough to cover a wing - it will be a shame to cover your wing, Marty!

Great job.
 
Marty, great looking work! When you say you'll be using modified wood spar aileron hangers, how do they need to be modified to be used for flaps? Will you be using 40 degrees of flap?

Looks great.
 
One more thought on this product: The nose ribs add another attach point on the front of the spar cap. I would think those attachment points would have added strength to the spar to resist the "failure mode, twisting. Maybe an inside added flange that the builder could notch out except at each location where the "old" nose ribs would have been or just leave the whole thing? How about aileron/flap leading edges. Cheaper for a first product? Easier to engineer without catastrofic consequences? Failure mode likely to happen over time etc. If I had any of these I wouldn't want to cover them. Almost as good as bush wheels for "man mode" ;-)

The PA-14 had the highest gross weight of all the long wing Piper's and didn't have nose ribs. Neither did the J-4, J-5C or PA-12.

http://www.dakotacub.com/images/pricing - wing & rib assy.pdf

Crash
 
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D.A.
The difference is very slight. The flap hinges are a bit shorter and at a different angle than that of the aileron hangers. The picture below shows the CAD drawing I made showing the two overlaid. The lower hanger is for the flaps; longer one is for the aileron. If you look at the jig picture you will see the hole marked "FLAP". The only difference between the two hangers is that the bushing end location for the flap makes the tube a little shorter and the hanger is angled down more than the aileron but all the parts are the same. All the measurements were taken from stock S.C. flap hinges, overlaid on the aileron hinge to determine the difference. I sure love using CAD. I use it to make all my jigs and the bend patterns for fittings and figure in the bend allowance data so my "U" shaped brackets come out spot on. These hangers are pretty simple but did take me a lot of time. The lower angle bracket gives it the extra support necessary for the wood spar.
Marty

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The PA-14 had the highest gross weight of all the long wing Piper's and didn't have nose ribs. Neither did the J-4, J-5C or PA-12.

http://www.dakotacub.com/images/pricing%20-%20wing%20%26%20rib%20assy.pdf

Crash

They had stamped nose ribs, FYI.

P2240544.JPG


Tim
 
Marty, I sure like the looks of your wings. Nobody realizes the work you put into them until you have done a set from scratch. Great job.
 
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