PDA

View Full Version : Cub Leading edge removal question



Quazzi
01-28-2016, 10:09 PM
Hi Folks,

I have a 1946 J-3 project that I have had for too many years and am starting a restoration. I have the wing on a table in the basement and want to remove the leading edges, replace the #3 leading edge and pound out a few dents in the others and slap it back together. A friend who is an IA advised not to remove the #1 or #2 leading edge because it will mess up the the wash out and it will take a large amount of time to get everything back lined up. I am looking at the wing and it looks to me that I could take off the number one leading edge, pound out the dents put it back on then do the same to the #2 leading edge and it would not be a big hassle.

My question to everyone is ...........Can I take the leading edges off, repair them and put them back on without messing with realigning and squaring the whole wing. I can use filler on the little dents but there is one or two big dents.

Thanks in advance for your ideas.

Mark

mike mcs repair
01-28-2016, 11:36 PM
DO NOT LISTEN TO YOU EXPERT FRIEND!!!!

take them off, do what you need, then TRAM(Square up) you wing bays, then set washout before reinstalling leading edge skins...

will only take an hour TOTAL...

mike mcs repair
01-28-2016, 11:37 PM
traming http://dakotacub.com/images/stories/Support/Wing%20Trammeling.pdf

mike mcs repair
01-28-2016, 11:38 PM
Leading edge install
http://dakotacub.com/images/stories/Support/install%20-%20leading%20edge.pdf

Steve Pierce
01-29-2016, 07:34 AM
I assume you have aluminum spars? Just put the wings on saw horses and put a washout block on the rear spar. I usually support the butt rib and outboard aileron rib and put the washout block under the rear spar at the outboard aileron bay rib. Good luck knocking the dents out and not being able to see them, I usually just stretch them and spread it out. You won't need to trammel the wings unless you loosen or remove a drag/anti-drag wire.

skywagon8a
01-29-2016, 08:11 AM
Good for you in doing this. Whatever you do, remember that any imperfections in the leading edge skins can and will present themselves through the fabric. Don't kiss off a small imperfection saying "Oh, that's good enough".

I suggested to a friend that he replace his leading edges before recovering. He didn't want to spend the money and time. Later when he tried to sell the plane a customer walked away because of this. So he paid someone else to do the wings over again. Expensive in more ways than one.

Quazzi
01-29-2016, 12:58 PM
Thank you so much for the advise and the links to the articles. You have given me the confidence and green light to proceed which is what I needed.
If I don't mess with the drag/anti drag wires do I need to tram the wing bays?
I'm assuming that when I take the old leading edges off and knock out the dents that it will fit right back in the same screw holes?
Thanks again

Quazzi
01-29-2016, 01:05 PM
They are aluminum spars.....Thanks Steve for the advice.....Some folks I know use felt on the leading edge to smooth them out besides using filler to smooth out the bumps on the leading edge. Any thoughts on that.

Thanks

wireweinie
01-29-2016, 02:30 PM
Thank you so much for the advise and the links to the articles. You have given me the confidence and green light to proceed which is what I needed.
If I don't mess with the drag/anti drag wires do I need to tram the wing bays?
I'm assuming that when I take the old leading edges off and knock out the dents that it will fit right back in the same screw holes?
Thanks again

What if they weren't set up right, to begin with? It's open right now, check everything! Make sure all measurements are correct before you cover it.

And, depending on the size of the dents, the screw holes may or may not align back up. If the dents are bad enough are you sure you don't want to replace the section?

Web

Steve Pierce
01-29-2016, 06:57 PM
If the wings go on and off good they are usually square but being creative you can verify it with the leading edges off.

MT12
01-29-2016, 10:43 PM
If you're going to New York, don't get off in Chicago. New leading edges from Dakota Cub are right around $284 per side. Cheap since the leading edge is one of the first and most noticeable things on any rebuild. I agree with Mike and Steve, its pretty easy to trammel and wash out, I can even do it. Especially since you're going to want to go through all the steps anyway to ensure you are starting with a good straight and true wing. As I recall using felt requires the use of a sewn envelope and is a p.i.t.a.

skywagon8a
01-30-2016, 06:34 AM
... As I recall using felt requires the use of a sewn envelope and is a p.i.t.a.
Not true. I did it using the Stewarts process. One piece of fabric for the top and one piece for the bottom. Stewart glued around the perimeter. The felt does soak up a lot of glue.

Quazzi
01-31-2016, 01:06 PM
Thank you all for your inputs. You have talked me into doing what I wanted to do in the first place....... Take it all apart, sand blast and paint the non aluminum parts, put on all new leading edges, and have a nice looking wing. Everybody in the forum feels that I can probobly get it back together in one piece, so I will give it a try.

Back ground on my 1946 J-3 is that it hasn't flown since 1965......it is complete with good logs.... I bought it in the late 1990s and told my oldest son that I would have it done for him to learn to fly by the time he was 14......he is now 27. Good news is that I was able to teach him in a friend's super cub, hence the membership in this club. I am dedicating this year to get the plane done....son thinks it will be done when his child is 14 years old (he has no kids yet)
Thanks again,

Mark

12Geezer2
01-31-2016, 07:42 PM
Quazzi : Perhaps I missed it, but you don't tell us where you are. Might be a real experienced person just around the corner who is willing to help. Of coarse some are professionals and might want a token of appreciation. Could be money well spent. Just my 2 cents. Ben down the road and found several life long friends in the search for knowledge of the long wing Pipers. Good luck and make it pretty !!!! geezer Dan

Oliver
02-01-2016, 09:07 AM
Quazzi,

For a cleaner look and stiffer wing,
drill all new holes and replace all rib screws using truss head stainless #4s - lower profile than original screws - even on skins you don't replace (including trailing edge).
Youll find most screw holes are stripped from age and wear. (Try to tighten a few to confirm this)
lay out a drill pattern right next to old holes, keep them neat and aligned, everything will show thru fabric when you're done. (old holes won't show)
Sounds like a pia but goes pretty quick.

ps. If aluminum spars, use regular self tapping #4 (steel) where skins attach to spars. Requires a little more force to cut threads in spar, Phillip heads strip out easily on stainless truss head screws.
Dakota Cubs a great source for wing stuff

Quazzi
02-03-2016, 09:08 AM
Hi Dan,

I live in Charlotte, NC and am a member on the local EAA chapter that has a lot of homebuilder experience that I have already leaned on for advice. There are a couple restoration shops that have mostly been willing to talk to me.

Hi Oliver.......thanks for the response...most of the screws that I have taken out of the wing are very tight. I have bought the new #4 screws from univar, but will take a look at your suggested lower profile stainless.....bought a number of things so far from Dakota Cubs and am going back soon for more......

Thanks again for your time,

Mark

skywagon8a
02-03-2016, 09:24 AM
..... I have bought the new #4 screws from univar, but will take a look at your suggested lower profile stainless.....
Stainless on bare aluminum is a NO-NO​ because the dissimilar metals cause corrosion. You do not want this on your leading edges under the fabric hidden from sight.

Oliver
02-03-2016, 09:39 AM
Stainless on bare aluminum is a NO-NO​ because the dissimilar metals cause corosion. You do not want this on your leading edges under the fabric hidden from sight.

Ss crews are what Dakota cub provides with their skin sets, however
Based on skywagons advise, research a little more, I'd hate to lead you astray.

Oliver
02-03-2016, 10:12 AM
As per Fastneal engineering chart:

on a scale from 1 - 3
1 = Corrosion of the base metal is not increased
2 = corrosion of the base metal marginally increased
3 = Considerably increased

galvanized/zink plated fasteners in aluminum base metal = 1

304 stainless fasteners in aluminum = 2

im sure there are many more variables, alloys, environment, application etc.
but yes, skywagons has a good point.

Oliver
02-04-2016, 01:07 AM
Skywagon,
Not doubting your wisdom
But would running a ss screw thru epoxied alum skin (vs bare) into a rib reduce galvanic corrosion? painted or not, no way to eliminate metal on metal contact between fastener and rib.

mike mcs repair
02-04-2016, 01:42 AM
uuuggg!!

SS or not ..... ugggh!

not = screw disappears in a rust cloud....

SS = ???

use stainless if available....

and USE THE REAL ORIGINAL SPAR SCREWS

skywagon8a
02-04-2016, 05:12 AM
.....But would running a ss screw thru epoxied alum skin (vs bare) into a rib reduce galvanic corrosion? This would be the way to do it. painted or not, no way to eliminate metal on metal contact between fastener and rib. This would be minimal contact and likely would cause little concern.
The corrosion which can occur usually is under the screw head where there is more metal to metal contact. I've seen some very corroded leading edges. Epoxy the skins and you should have little concern.

stewartb
02-04-2016, 06:52 AM
I've heard guys argue about slotted head vs phillips head but everyone I know uses stainless screws in leading edges.

RaisedByWolves
02-04-2016, 09:10 AM
I've heard guys argue about slotted head vs phillips head but everyone I know uses stainless screws in leading edges.

In my experience the slotted gives you a better bite. The Phillips strip easier.

Oliver
02-04-2016, 11:35 AM
If you want to turn a one day project into a three day project, go with slotted.

and Quazzi, welcome to SC.org... :)

skywagon8a
02-04-2016, 11:44 AM
If you are going to use #4 Phillips head screws, invest in several new quality screw drivers. Those small Phillips very easily strip out the X. A partially worn screw driver makes things worse.

cubdriver2
02-04-2016, 11:52 AM
If you are going to use #4 Phillips head screws, invest in several new quality screw drivers. Those small Phillips very easily strip out the X. A partially worn screw driver makes things worse.

This is where Snap On really shines. I fix a lot of Alum triple track storm windows. Some have 4 tiny steel Phillips screws in the corners that are threaded into a zinc/Alum corner. Been taking these apart since 1973 and the ONLY screw driver that works is the Snap On #1

Glenn

wireweinie
02-04-2016, 01:42 PM
Listen to MCS Mike and then go buy several #1 Phillips, Apex type screwdriver tips. The main reason for stripping the screw heads is a worn or incorrect screwdriver. With the Apex tips, when the tip starts to ride out of the screw head, that's your cue to remove it, throw it far, far away, and replace it with new.
I can't atest to the reactivity claims of stainless vs steel but pure experience has shown me that stainless reacts less to contact with dissimilar metals than steel.

Web

N86250
02-04-2016, 02:35 PM
My scant experience on the steel vs stainless issue is moisture. If moisture gets to SS and aluminum-the aluminum corrodes. If moisture gets to steel and aluminum- the steel rusts. If everything stays dry-no corrosion, no rust. jrh