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Wings for my 2+2 project

RVBottomly

PATRON
Asotin County Washington (KLWS)
I'm starting to source materials for the wings on my 2+2 build. That, of course, got me thinking too much and caused me to realize how little I understand.

The quick summary: The mission for the airplane is moderate cross-country ability with option to access reasonable rough strips in our area (Idaho and Washington). I'm not going to be gonzo, I don't think, because my wife will be flying with me most of the time. We like to go to fishing holes and plan to go to the Seattle area a few times a year (Paine field or thereabouts--280 miles from us). Floats are in the semi-distant future.

The source of doubt: My Wag Aero plans are for a wooden wing, but you can buy a "wing kit" in aluminum from them. I want to keep the option open for Keller flaps--I contacted Performance STOL and they discouraged use on a wooden wing. Fair enough. I'll go with aluminum.

I have no drawings for a metal wing for my project (other than Northland's), but the 2+2 plans indicate 2200 GW. My issue is I can't see for myself what is required for a for that GW. I've read fairly exhaustively here about GW increases with spar doublers, etc. I'm nervous about what seems to be a cavalier design.

I'd like to scratch-build my ribs, and it seems like I could fit a 4.5" rear spar in instead of a 4" one. Is that even done? Can someone point me in the right direction for research?

Otherwise, after looking at Stewart's Wildcat Cub build, I'm starting to think I want something like that. http://www.supercub.org/forum/showthread.php?52224-Another-which-kit&p=704442&viewfull=1#post704442

I guess the basic question is: how should I scratch build a 2200 pound gross weight wing? What should I look out for, etc.

Thanks,
Vic
 
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I would emulate the PA18 wing approved for higher gross wt. If you want the keller flaps they fit. I think Javron is the best deal for any exp parts. If you use the PA18 wing planform I would start on them early. You will need to change the wonky designed control cable runs from the 2+2. All personal opinion. Your rate of climb may vary.
 
A 2 x 2 empty weight should come in around 1300 pounds. Two people +50 gallons of fuel (cross country) is a little more than 700 lbs, that leaves you with minimal weight for baggage, camping gear, camp chairs, stove, cooler, etc. A taller spar is not the answer to the problem. It fails from a twisting motion. Look at Bill’s thread on his cub build and you can see how Jay did it. I would go for a gross weight of no less than 2200 pounds. Also recommend the larger squared wing.
DENNY
 
The 2+2 will take any PA18, 12, or 14 wing. You will need to run the cables according to the wing so you will need wings built before finishing the fuselage. Flap handle and pulleys will need to be added for the flaps. On my 2+2, I built the wood wing with stock Super Cub flap bellcrank set-up and I ran my cables inside the wings. The 2200lb gross weight is for the wood spar; had an engineer run the numbers for me and the wood wing is way over built. Weight of my wing without the tank, tank cover or cables came to 64 lbs with all other hardware installed. AOA of the 2+2 is different than the PA18 so you won't get the same short field capabilities but that different AOA gives the 2+2 a faster cruse. I have stock length flaps and ailerons, also all wood. I haven't flown yet, currently working on firewall forward and covering. Scratch building is a big job. Is your fuselage welded up yet? Everything I've done so far is on my web site.
Marty
 
I want to keep the option open for Keller flaps--I contacted Performance STOL and they discouraged use on a wooden wing. Fair enough. I'll go with aluminum.
A properly braced wood spar wing should support the flap loads. It is the bracing which supports the loads, not the spars. I'm curious as to why they discouraged a wood wing. I helped a friend get an STC to install stock -18 flaps on a wood spar J-3.
 
Cub junkie, thanks for keeping me grounded (in a good way). After I read your post I remembered not to try to reinvent the wheel.


Denny: Thanks for the good points. BTW, one small correction: My wife's small and the two of us weigh around 270. But that 30 pounds doesn't take anything away from what you say. I'll look over Bill's thread more carefully. 900 pounds useful load sounds like a lot, but I know better.

Marty: Thanks for chiming in! I've studied your website obsessively. I really appreciate the amount of work you've done documenting things. I wish I could do the same, but I'm so short of time. I'm aware of the AOA differences and am fine with that. I suspect magical flaps might help some, but I'm not looking to enter contests, etc. Cruise is at least 50% important to me.

Yes, I've welded up the fuselage and am working on the landing gear right now. I've been having a pretty good time of it--it helps me decompress from the rest of the demands on my time.
 
A properly braced wood spar wing should support the flap loads. It is the bracing which supports the loads, not the spars. I'm curious as to why they discouraged a wood wing. I helped a friend get an STC to install stock -18 flaps on a wood spar J-3.

I think it was because it was an unknown. I like wood and am comfortable with it, after having built lots of wooden boats.
 
I think it was because it was an unknown. I like wood and am comfortable with it, after having built lots of wooden boats.
That's exactly why I went with a wood wing; many years building wood boats, guitars, teaching woodworking, etc. Nothing wrong with wood. I have everything on my web site to add wood flaps to the wood wing, all the drawings are there for all the parts.
Marty
 
floats, water, you might like aluminum better.

Hah! I have a 22 year old scrap-wood dory that sits outside year 'round. Still runs the rapids, but I did epoxy-encapsulate it with fiberglass reinforcement. Needs paint from time to time.

But I'm still leaning toward aluminum because, for one thing, it would be a new fabrication skill to acquire.
 
For my 2+2 I went with Dakota Cub PA12 wing parts and added their flaps according to their drawings. The parts and drawings are first rate in my opinion. They may be able to supply spar doublers. Plenty of work to assemble them and modify them for flaps and their 24 gallon tanks which you may want for cross country and backcountry flying. PA12 wings have the cables inside as opposed to PA18 being external.
 
Areonef out of Quebec has aluminum spar blanks they are beefier than the standard piper spars and I think they are load tested to over 2400lbs. My project came with their ribs and I think I’m going to go with their spars as well. They have a website and you can have a look.


Sent from my iPhone using SuperCub.Org
 
Areonef out of Quebec has aluminum spar blanks they are beefier than the standard piper spars and I think they are load tested to over 2400lbs. My project came with their ribs and I think I’m going to go with their spars as well. They have a website and you can have a look.


Sent from my iPhone using SuperCub.Org

Thanks. I saw that referenced somewhere in an older thread, but I now I can't find anything. Maybe Olibuilt has heard of them?

I've looked over Bill's thread on the Javron, and see the reinforcing on the spar. I've also noted reinforcements offered by most of the other wing folks. But I'm sensing (from lack of interest in my inquiries) that I'm expected to buy a wing kit before getting to see details.

Which is fair--someone goes to all the testing trouble, they ought to get reimbursed. But, I'm not really interested in a kit. It's tempting, but right now I'm still in scratch-built mode.

I'm willing to buy drawings, but so far I'm running into silence. That does not mean I've exhausted my options in trying to communicate--just that I'm too swamped to get very far right now.

And, to reveal how double-minded I am, I started looking closely again at the wood wings in the drawings I have. I'm getting drawn back in--I love working with wood.
 
Ollibuilt used his ribs for sure. That’s how I found him.( I have the same ribs and couldn’t identify them at first) marcelblanchette@videotron.ca is aeronef.
As far as drawings go wouldn’t you be able to use the drawings on Buggs’ site or the Northland drawings-or is there that much of a difference on the 2+2?


Sent from my iPhone using SuperCub.Org
 
Ollibuilt used his ribs for sure. That’s how I found him.( I have the same ribs and couldn’t identify them at first) marcelblanchette@videotron.ca is aeronef.
As far as drawings go wouldn’t you be able to use the drawings on Buggs’ site or the Northland drawings-or is there that much of a difference on the 2+2?


Sent from my iPhone using SuperCub.Org
The Northland drawings are good for a standard wing, up to 1750 gross wt, I think. But the 2200+ gross weight wings seem to have additional reinforcement.

The wood wings on the Wag plans go with the 2200 GW, and Wag sells a kit for aluminum wings--no flaps. When I asked for a drawing, I was told they only sell kits....no drawings or custom changes.
Vic

Sent from my SM-J320V using SuperCub.Org mobile app
 
And, to reveal how double-minded I am, I started looking closely again at the wood wings in the drawings I have. I'm getting drawn back in--I love working with wood.

I had an engineer friend run the numbers on the wood spars in the 2+2 wing; they are way over built. Flaps are included in the 2+2 plans as an option but most of the detail is missing. I drew the wood wing layout with the flaps and all the measurements in CAD, here's the link: http://www.marty2plus2.com/wing-layout.pdf

Next, you will need to modify the aileron hanger for the wood wing slightly for the flap hangar, another link to those drawings: http://www.marty2plus2.com/flap-hanger-outboard.pdf

The wing attachments on the wood spar change the hinge locations on the flap, another drawing you will need: http://www.marty2plus2.com/full-flap-drawing.pdf

and the flap hangar at the bellcrank .....http://www.marty2plus2.com/full-flap-drawing.pdf

I also had the wing analyzed to remove the cross brace that goes inside the tank bay and through the fuel tank. My wing has a sheer plate (1/8") plywood under the tank and the tank now just sets in place on the straps. Removing the tank doesn't require de-rigging the wing. All my cables run in front of the tank, inside the wing for a very clean set up. One other note, with the leading edge skin glued 1/16" ply there are no screw heads under the fabric for a very clean design. When I glued the leading edge on with the washout block set under the outer rib, no drop occured when the block was removed.

I also have drawings for wood flaps and ailerons, they came from another source and I drew them up in CAD. If you decide to build in wood, I have all the necessary drawings and you are welcome to use them. Considering the number of wood wings on the aerobatic side of things still, wood is a good choice. You will spend more time building but the wood wings are very satisfying to build.

Wood is a viable option. I've got all the drawings so something to think about; especially if you are a woodworker. You will still get plenty of sheet metal skill development in the firewall forward so lots to learn.

Marty
 
Wood is a viable option. I've got all the drawings so something to think about; especially if you are a woodworker. You will still get plenty of sheet metal skill development in the firewall forward so lots to learn.

Marty

You are pushing me over the edge, Marty! I love looking at your photos. I still have plenty of epoxy from my last boat project.
 
Vic,
I'm enjoying following your project as I have Marty's. There is something to be said about the beauty of finished wood. Sort of like a piece of fine furniture or jewelry. Wood has been used in airplane construction since day one. The biggest issue as I see it is to protect it from moisture. With the use of modern adhesives and protection coatings, a set of wood wings should outlast you. I've owned old airplanes with wood wings. Pay close attention to where a drop of water could find a home and prevent that location from happening.
Pssst, I'm sure that Marty would be very proud should you use his plans to produce a set of wings. :lol:
 
You are pushing me over the edge, Marty! I love looking at your photos. I still have plenty of epoxy from my last boat project.

Working on it! My entire wing is coated in West System Epoxy, way better than my first boat. When you put a bolt into the wood, coat the bolt with bees wax to seal the inside of the hole ..... that's after the hole was sealed with epoxy. Best source for Bees wax is the hardware store ..... toilet floor gasket. I've learned a lot from the guys who have built wood wings for years ........

Marty
 
Pssst, I'm sure that Marty would be very proud should you use his plans to produce a set of wings. :lol:

Thanks for that, skywagon. His plans have been in my "2+2" folder for over a year. I'll confess to wanting to make a few subtle changes though.... More on that in due course, having to do with flaps.

I've also been giving a lot of thought to moisture accumulation. That's one place have some practical experience from boatbuilding.
 
I know exactly where those spars are.


They are a HD version of stock Super Cub spars. I've use them in my Red Cub







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The numbers bellow are in metric, and French, sorry...

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lkYOK6AoLpNM2l9ST9FeAuOEMgHuScQt9jx25lqH2lQz9ARadVPhwwsCMlXx8EIWkyYTc-t03nTdVD0h9Tjd8j0MBjpRESVqrVo_OHhmaagZqAMfXECvFECH3ZcPWXyIFDga_EMPvhQPEAGdw6knm7ZhEAGaR2P0v9l3R26K9yk8CSGWX94WOAuCsGtAA4X409Kt6E-WPdUxNAOS2FjdyKOoghAgEVXvWXT42hp9bTNyy_PWShD_10PaYztfty5-OYEOSc_UFi184ZAoZKO6KVAKkS0H5gZz7LZFEWYlwokx2fYRlzl_OqnueEvcCaXJ3pbIRyRfXEcCav6d28Hf08InsBlatKj8RUxzzMNAWWAB-kfEALmM3uGmNgUKtvAlTjBHHvH6vnze316yPx8s9OY450QhwWl8h5mp8pFz0ghmxVElU0f8OOXfapQHFI8DAqAyOJe5MUVr5UScZEU91a1K9_S5uDC3jHLfEJUAUp7GrGK4oPNUsiYaXI_MZClaXEzeRiewutVNXyB3ZMsJrJMk-7_m3gu8sZbsTnV0ia-Hu6JmC-9HnN2IVnMwSIJnXEVAIM-SeDrN-M6sm2-oP1gPVXojQW2yBlbQVBJ8Fx49Er2Gqgjy4qPmHRzlTG6bJ5eSYJOdILRaF-kk2ng_aAr6=w2326-h1308-no
 
Oli, thanks!

BTW, I read French pretty well.

(ou, je lis le français assez bien...)

Unfortunately, aeronefmontreal.com is no longer active.
 
I like wood but the down side to wood spars anymore is getting them. Wicks has quit selling spars and aircraft spruce sometimes has a hard time coming up with 17 ft blanks. The alternative to spruce is douglas fir but that comes with a higher weight(about 15% stronger) I feel lucky that I got nice blanks from Wicks in 2016 for my champ, $525 ea. I waited 7 months for them to call me and tell me it was my turn. Bottom line is if you like wood you aren't going to be happy with metal wings. Metal allows a much easier path to the Keller flaps if you want those. If you go with metal and you get burned out building parts you can buy piece's as you wish. The wood 2+2 wings as depicted in the plans use mostly J3 wood wing drag wires, compression struts and fittings. The flap option as you know is a drawing of a flap, otherwise you are doing what Marty had to do and free style the flaps into the structure. The original prototype 2+2 had PA12 wings so all the wood wing stuff was done by field builders.
 
I like wood but the down side to wood spars anymore is getting them. Wicks has quit selling spars and aircraft spruce sometimes has a hard time coming up with 17 ft blanks. The alternative to spruce is douglas fir but that comes with a higher weight(about 15% stronger) I feel lucky that I got nice blanks from Wicks in 2016 for my champ, $525 ea. I waited 7 months for them to call me and tell me it was my turn. Bottom line is if you like wood you aren't going to be happy with metal wings. Metal allows a much easier path to the Keller flaps if you want those. If you go with metal and you get burned out building parts you can buy piece's as you wish. The wood 2+2 wings as depicted in the plans use mostly J3 wood wing drag wires, compression struts and fittings. The flap option as you know is a drawing of a flap, otherwise you are doing what Marty had to do and free style the flaps into the structure. The original prototype 2+2 had PA12 wings so all the wood wing stuff was done by field builders.

Cub junkie, thanks for all that info. I think first thing would be to check availability of spar material. A year ago I started looking and was even considering Doug Fir--I have a friend who owns a tree farm and small saw mill in the Blue Mountains. He has some very nice vertical grain stuff in long lengths, but his wood is even heavier than the standard quoted weights in the tables. I decided against it for that reason. I didn't trust myself to try to fiddle with changing dimensions to account for the increased strength.

I haven't totally foreclosed aluminum, it's just that the equation in my mind works out like this:

Aluminum wings: "Interesting project--I think I could do it in not too terribly long."
Wooden wings: "Really? This sounds so cool I can almost taste it."

As for the Keller flaps, I'm not convinced that there is a real problem. I would probably modify the compression struts anyway, maybe with a truss type system at the flap hinges. But I also am thinking of going with more simplified slotted flaps.

So it goes. I want to check on spruce availability first before I jump in with both feet. I'm not going to wait 7 months.

Vic
 
Marty, what kind of strength do you think that adds? I know my sleigh runners gain a bunch from coating with West System....
John

Not speaking for Marty, but from boat building I know that coating with epoxy and fiberglass you get a lot of increased stiffness (and added weight). Coating with just epoxy doesn't add as much to stiffness, but you get a benefit of keeping moisture out.

But on external curved surfaces subject to flexing forces, it is liable to crack without the fiberglass, and that defeats the water-sealing purpose. That's why wooden plywood boats covered on the exterior with fiberglass and epoxy seem to be a very successful combination. The interior portion is often just epoxied without fiberglass.

Same goes for strip-planking. But traditional carvel planking (broad thick planks) does not do well with epoxy because those planks are designed to swell when wet.
 
Need 17' spruce? That is easy... I have plenty of clear spruce down and decked, and about to take more down. Give me specifications on RPI and size and I bet I can get it cut here in town.

Sitka Blue Spruce.
 
Need 17' spruce? That is easy... I have plenty of clear spruce down and decked, and about to take more down. Give me specifications on RPI and size and I bet I can get it cut here in town.

Sitka Blue Spruce.

That sounds pretty neat! I'll figure out the specs.

Shipping down here sounds like an adventure, though.

Thanks,
Vic
 
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