PA-18 wing rebuild

[Gnarly]

About 1.5 years ago I posted about a 1979 super cub that ground looped in Tok Alaska. We had a collapsed right gear and the right wing was damaged. After tearing down the wing we are looking at replacing fore and aft spar’s, five ribs, center leading edge skin and the two outer sections of false spar. There is other minor damage to repair, some resulting from the 2100 mile trip in a uhaul. I know all the answers I’m looking for are on this forum or the internet, but this forum seems to have the best gouge out there. I’m looking for wing diagrams/schematics and any other blueprints or manuals that will help me get it back together. I have an A&P who will help/supervise time permitted, but I really want to learn to do it. After ordering parts from Univair they told me I have to order the two types of screws individually? Is that normal. We’re going to use steward systems for fabric. Is that a good way to go? Thanks for reading.
R/
jason

[mike mcs repair]

Doesn’t dakotacub have a wing build manual online?


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[mike mcs repair]

Regular screws for most of it. Then spar screws to attach ribs to spar on right


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[BC12D-4-85]

FWIW you are not alone in having a bad experience at Tok. Others have both before and since. Some's due to the runway crown, others from the raised runway edge in spots and the typical crosswind mainly from the South towards the Tok River valley. I asked a FAA examiner recently about that paved strip. He said the locals often land on the adjacent gravel, or if the wind's strong, use the cross taxi apron or the other Tok Airport to the south a couple of miles along the highway. Best wishes for your repairs.

Gary

[Gnarly]

Fortunately it’s wasn’t me that looped it but I was the lucky one who got to pick it up. Everyone I talked to up there said exactly what you said, which made me feel better towards the person who did it. There are those that have and those that will.

[Gnarly]

I kept all the screws but my feeling initially was that I would buy new for the repair. After univair guy told me they sell them individually I was forced to reconsider. Can I get those screws in bulk?

[Amy]

Doesn’t dakotacub have a wing build manual online?


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There are some wing documents here (scroll down to the wing section): https://dakotacub.com/index.php?rout...ormation_id=12

—Amy

[mike mcs repair]

I kept all the screws but my feeling initially was that I would buy new for the repair. After univair guy told me they sell them individually I was forced to reconsider. Can I get those screws in bulk?

Yes aircraft spruce has them. I forget the part number. ???529?? AN529??


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[mike mcs repair]

https://www.aircraftspruce.com/catal...ages/an530.php


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[Gnarly]

Awesome. Thank you very much.

[supercub]

You can buy a complete wing hardware kit from Dakota Cub. It will include the two different screws mentioned above plus all the nuts, bolts and washers. There's info if you do a search on what to do on rebuilding. Make sure you have a flat surface to start with, but be sure to shim the rear outer wing for the wash out before you start installing any of the skins. There's good info online on how to trammel the wing too, just do a search. There's some good info on you tube too. I just hung my J-3 wings yesterday that I rebuilt, one wing I installed new spars. Lots of good info and help here too. Parts manual is a good source too. Good luck.

[Oliver]

Re screws, the oval head “pk” stainless are great for attaching sheet metal to ribs, use plated steel screws when attaching to spar cap. Stainless screws will strip and break off in if used in spars.
Also, consider drilling all new holes when re attaching old skins to ribs, it will make for a stiffer wing as older holes tend to wallow out a bit and will be tough to get screws tight without stripping a bunch of them in old holes.
Snap a line a 1/4” or so below the old holes.

[stewartb]

https://www.aircraftspruce.com/menus...talscrews.html

Truss heads. Type A are the sharps, B are the blunts. I'm pretty sure my planes have used stainless. I know for certain that's all I keep in my own bins. I'm lucky to have aircraft parts stores nearby (including Spruce) but for screws and such I always go to Spruce.

[Steve Pierce]

Drawings are here. Take it to Kinkos and get a print made to hang on the wall. http://store.straight-level.com/nort...-cub-drawings/
I use the Dakota Cub spar screws, they fit right and don't snap off in the spar like the stainless steel ones Univair sells. You will need several hundred T4x4 stainless screws from Aircraft Spruce for leading edge and false spar skins. I like the Dakota Cub ribs because they fit like the Piper ribs and you don't have to figure out where and drill new holes in the spar like you do for some of the Univair ribs. Paul Babcock has a Super Cub wing build video that I believe Univair sells. Lots of photos and discussion on this site about wing repair and wing rebuild. Use a key word in a Google search followed by "site:supercub.org"

[Bill Rusk]

You might find some info that will help here. https://www.supercub.org/forum/showt...avron-Wing-Kit

Although it is experimental it is very close to a stock wing. Lots of pictures.

Hope it helps

Bill

[dgapilot]

https://www.aircraftspruce.com/menus...talscrews.html

Truss heads. Type A are the sharps, B are the blunts. I'm pretty sure my planes have used stainless. I know for certain that's all I keep in my own bins. I'm lucky to have aircraft parts stores nearby (including Spruce) but for screws and such I always go to Spruce.

Stainless is the wrong way to go with the screws. Stainless and aluminum are farther apart on the galvanic table than plain steel and aluminum, so you will have more corrosion faster if you use stainless. Stainless is softer, so once the corrosion starts, it is more likely you will bugger up the head when trying to remove them the next time around. Stick with plain steel! You can get them at McMaster Carr and pretty much any commercial fastener outlet.


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[stewartb]

Mike turned me onto this screwdriver a few years ago. Handy. Slower than typical drivers. Most broken and stripped screw problems are eliminated. Very handy. https://www.homedepot.com/p/RYOBI-4-...P44L/205975772

[Charlie Longley]

There are some wing documents here (scroll down to the wing section): https://dakotacub.com/index.php?rout...ormation_id=12

—Amy

Thanks Amy that’s helpful! I’ve been looking at my wings hanging on the wall trying to decide on the rebuild.

[mike mcs repair]

Mike turned me onto this screwdriver a few years ago. Handy. Slower than typical drivers. Most broken and stripped screw problems are eliminated. Very handy. https://www.homedepot.com/p/RYOBI-4-...P44L/205975772

That’s a little different then mine. Mine has clutch settings on nose.

But still well worth it.


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[Gnarly]

I’ve got a similar skill screw driver. It’s awesome. Surprising amount of torque but somehow I end up stripping fewer screws.

[tempdoug]

get univairs wing assembly cd. https://www.univair.com/manuals-vide...-assembly-dvd/

[tempdoug]

stewarts system. im at the bottom looking up, but the biggest thing i had to learn was to let the glue dry before putting heat to it. dont be in a rush there.

[Gnarly]

Stewart’s seems like it’s very straight forward. I’m getting ready to paint some metal parts including the spinner which hasn’t been touched since 1979. Any tips or tricks would be greatly appreciated. Thanks to all for the great information.

[Charlie Longley]

Stewart’s seems like it’s very straight forward. I’m getting ready to paint some metal parts including the spinner which hasn’t been touched since 1979. Any tips or tricks would be greatly appreciated. Thanks to all for the great information.

I am going to start on covering a flap for a Pawnee next week using the Stewart system. It’ll be my first time using the system. I’ve been doing a lot of research and talking to friends who’ve used it. Two important points I’ve learned is the recommended air pressure is too low and using a viscosity cup is critical.

[Hardtailjohn]

Stewart’s seems like it’s very straight forward. I’m getting ready to paint some metal parts including the spinner which hasn’t been touched since 1979. Any tips or tricks would be greatly appreciated. Thanks to all for the great information.

I've been using it since the mid-90's...long before it was Stewart Systems..... Just remember, it's a waterborne, so clean everything and etch the way the instructions tell you, not the way all the "experts" tell you, and you'll do fine. You're dealing with water as a solvent, not a chemical. It's not difficult, just different! Holler if you have any issues, we can get you through them.
John

[boarfish]

I’ve done two airplanes in Stewart Systems now. I mix by weight on an electronic gram scale. It’s much easier and more accurate than screwing around with a viscosity cup. I’ve done fine with a line pressure of 80 and a setting of 22-25 at the gun. You need to have a good quality 3/8” hose and high flow fittings. Never had any problems.

Don’t get in a hurry applying your top coat. When your painting something small it’s really easy to lay the pain down too fast. Be patient and don’t try to lay the paint down to heavy. It will flow out.
If you follow their instructions carefully you shouldn’t have any problems.




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[Douten]

I'm building extended wings for my ex pa-11 ordered Dakota ribs for the extensions my question is how do most attach the wingtips anchor nuts, clip nuts, tinnerman plates? my other 11 has the Ferguson extensions with a wooden end rib so that was easy to put the wingtip on. Thanks for ideas Douten

[Bearhawk Builder]

John, have you mechanically etched aluminum instead of using ekoetch before ekoprime? It's a little hard to pressure wash a wing in these temperatures.
Talked to Andy about it a little but wondered what your take is on it.

I've been using it since the mid-90's...long before it was Stewart Systems..... Just remember, it's a waterborne, so clean everything and etch the way the instructions tell you, not the way all the "experts" tell you, and you'll do fine. You're dealing with water as a solvent, not a chemical. It's not difficult, just different! Holler if you have any issues, we can get you through them.
John

[Hardtailjohn]

John, have you mechanically etched aluminum instead of using ekoetch before ekoprime? It's a little hard to pressure wash a wing in these temperatures.
Talked to Andy about it a little but wondered what your take is on it.

I use the EkoEtch and do a small section at a time, and rinse with hot water on a sponge. I haven't blasted or anything. I just did tank covers the other day for a Smith Cub and leading edges not too long ago (we're cold too) and used the sponge and hot water and it works ok. I thought about the pressure washer, but it's a pain to get it all put back when it's this cold!
The biggest thing with the etch is that you're getting rid of any oils and contaminants, and that's paramount with a waterborne.
John

[skywagon8a]

I'm building extended wings for my ex pa-11 ordered Dakota ribs for the extensions my question is how do most attach the wingtips anchor nuts, clip nuts, tinnerman plates? my other 11 has the Ferguson extensions with a wooden end rib so that was easy to put the wingtip on. Thanks for ideas Douten

This is an extension project I did last year. https://www.supercub.org/forum/showt...+wing+tip+test
You need to give us more description of what you are doing in order to have a proper answer.

[Douten]

I'm squaring the wings and installing fiberglass wingtips so two full length ribs outside of the aileron rib (24 inches) I've spliced the spars and ordered full length Dakota ribs and want to be sure when I install the wingtips that I don't crack or break the rib or have the holes wallow out over time. I'm thinking 6-32 anchor nut riveted to the rib.

[skywagon8a]

If I understand correctly, you are going to cut off those tapered spar caps, install a full sized rib at the tip then screw on a squared fiberglass wing tip similar to the tips in my pictures? From a structural perspective 2 or three screws will hold it. However you will need more to just hold down the edges of the tip. Also 6-32 seems too small a diameter because of the bearing loads in the tip. It is easier for a small diameter screw to pull sideways in the fiberglass than a larger diameter like a 10-32. My tips use 10-32 machine screws in plate nuts spaced about every 6".

How much additional span are you adding?

[mike mcs repair]

Think we always used just #6 pk screws for installing tips. No need to get any bigger or nut plates. You will have many screws holding on the tips


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[Douten]

I'm just basically squaring the wing outside of where the farthest point of rounded tips would be then the fiberglass tips which are about a foot each side. going to place the last rib at 24 inches from the aileron rib which will be about two inches wider each side than the 11 I have now. I would like to go a little more but I am the slowest plane out there already. I checked the tips I have and 6-32 fit the holes already in the tips so instead of doing a bunch of fiberglass work I plan to just use the old holes also trying to keep the plane as light as possible so 6-32's weigh less than 10-32's (Thanks for messing with my mind Bill Rusk). Thanks Mike I just don't want to break a rib down the road is why I am asking. I guess I've seen some messed up ribs that you wouldn't know about until they were uncovered and flew just fine.

[skywagon8a]

That should work fine. I doubt it will slow you down.

[TurboBeaver]

Are you extending your aileron's as well ???
If your not, you may want to consider that carefully.......... Long wing Cubs with short ailerons have caused lots of excited moments with some Very experience Cub pilots. Pretty undesirable combo in most cases. May wanta make a quick call to Reid or Dwight to consider this??? I am pretty sure both will advise you to extend your ailerons.
Good luck with your project should make a nice "Cub Special"
E

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[mike mcs repair]

Are you extending your aileron's as well ???
If your not, you may want to consider that carefully.......... Long wing Cubs with short ailerons have caused lots of excited moments with some Very experience Cub pilots. Pretty undesirable combo in most cases. May wanta make a quick call to Reid or Dwight to consider this??? I am pretty sure both will advise you to extend your ailerons.
Good luck with your project should make a nice "Cub Special"
E

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Never squared off wings without lengthening ailerons or moving them out. But have been hired to make wings back to round wings after severe crashes from lack of aileron control on squared off wings. (I’ll look for a picture)


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[Douten]

My 11 doesn't have extended ailerons and squared / extended wings been flying it for 20+ years so won't be doing this one.