Progress on my wood wing

[Marty57]

I haven't posted much in a while but finally have moved forward. The cables and pulleys nearly did me in! To say the plans are "lacking information" is an understatement. My wing drawings only showed one dotted line and one pulley on the rear spar for the entire wing! That's it; nothing more. So, what did I do? Got help here of course. Lets see, Christian, Laz, Duane; thanks. I also looked at lots of pictures. One thing I have found is that the wood 2+2 wing is a mix of just about everything Piper has built over the years. Anyway, I have the cables run and finished in the first wing. The wood cove needs a bottom piece of ply when I flip it over but is otherwise finished; cove ready to install on second wing. The second wing hangs from the ceiling ready for the same steps. Like every repetitive step the second one seems to take about 1/10 the time. Everything is made and ready to install on the second wing so that should go relatively fast. So what next? Close off the leading edge? Build the fuel tank hangers? Complete fuel tanks before leading edge? I also need to figure out something under the tank to create the bottom profile of the rib at mid tank. While I decide on what sequence to do next I'll finish the second wing to this current set up and than go from there. I sure am curious how much these wings will weigh. Everything in wood so far has been lighter than metal. The ribs (full aileron bay ribs) came in at less than 8oz and that seems to be pretty light compared to some of the rib weights that Bill posted. I will say that building up wood wings from scratch with the limited info in the plans has taken me way longer than expected. I will have a great set of wings when finished and really nice CAD drawings for the next guy to work from! Here are some pictures of the pulley set up. I made all the hangers from scratch (way too much time in hind sight) and all the pulleys are bearings.
Marty 57

pulley 1.jpg

pulley 2.jpg

pulley 3.jpg

pulley 4.jpg

aileron stop.jpg

[skywagon8a]

Marty 57



pulley 3.jpg

pulley 4.jpg

Marti,
Pictures #3 & #4 seem to show that the upper pulley bracket is attached to a flat metal tab which is bolted to the spar and bent above the bolt to align the pulley to the proper angle. If so, when you tension the aileron cables and then apply the flight loads this tab could bend towards the aileron. This means that you will only be able to get as much tension as the spring action of that tab will allow. In other words that tab needs to be more secure.

[Fortysix12]

Looks good Marty. I'm a tad concerned about the overall height of the top aileron guide pulley, the pulley covers are standard height and the clearance for the cable over the spar should be at a minimum when fully deflected.This will insure no conflict with the plastic or metal wing escutcheons. It might be just fine jbut be sure, I guess you could always shim the covers higher.Not really knowing how much clearance there is I put mine as low as practicle. I used the factory part here and it is double bolted to insure no rotation side to side.

[wirsig]

Did you run the you're cable up the cabin wall and into the wing vs. up the strut? Do you have any pics of how you did that?

Thanks,

[Marty57]

I consulted an aero engineer friend (he is also an A&P) about angling the upper front pulley. He suggested the bent bracket to establish the correct angle. I asked about the proper thickness and he suggested .063. I made a bracket from that but felt it was too flimsy so I made a second one out of the .090. After everything was assembled he came out to look things over and felt the set up looked good. I have to say that the short bracket requires a lot of force to bend. I wonder how much tension is on the aileron cable? Without any experience in rigging it seems to me that for the cable tension to bend that short a piece of .090 the cables would have so much tension that there would be a lot of binding in the control system even with the ball bearing pulleys that I used. How much tension is on the cables when installed? If necessary I could weld a side gusset to the bracket. Christian used a similar set up on his wing with a thicker bracket; .125 4130. That would also be an option if necessary.
The rear pulley is on a stock bracket. The height just clears the cable over the spar so if it is too high I’ll just need to make the cable fairing a bit taller.
There doesn’t seem to be much side load on the rear bracket so I’m not too concerned about rotation. After I get it rigged before covering I can add a small side bracket if necessary.
Regarding the cables in the cabin, I haven’t done that yet. It looks like one pulley on an angle just below the front wing attach point should work. That will direct the cable to a second pulley where the cabin side bends in then to the bottom pulley to the stick. I made up a couple of the cable routing tools that Mike shows on his videos and positioned them inside the cabin and it looks good. After I have both wings finished I’ll need to hang them on the fuselage to figure out the remaining cable routing including the flap set up.
These are great questions and comments; helps me to double check my set up before I move on. Keep them coming. Thanks

Marty57

[Bugs66]

As Marty said, I have a similar setup on mine. Doesn't budge a bit under tension. You would deform the pulley brackets before this bracket would bend. Nice job Marty! Glad you can move on now!

102.jpg

[Marty57]

Fortysix12,
You got me thinking more about that rear pulley bracket on the rear spar. I could make a simple straight piece of .040 with two holes and a slight joggle in the middle. I could slip it inside the bracket with the first hole lined up with the bolt and the second hole about an inch away outside the bracket for a second bolt. That would keep it from rotating. Thanks for the idea.

Marty57

[Fortysix12]

I will email a photo of mine. But you got the idea. All looks good.

[kevin]

Looks great Marty!!!

[wirsig]

That's Great! I may copy your idea on running the cables in the wing vs. up the strut.

Thanks again for posting the pics,

Wirsig.

[Check Six]

Great job, Marty! Would greatly appreciate it if you would weigh the wings before & after covering and post your results.

[Marty57]

I will do just that. I am very curious as to the weight of the wings as compared to metal. These wings will be as close to a wood duplicate of PA18 wings as possible so it should be interesting. I hope to have the wings finished excluding the fuel tanks late winter.
Marty57

[Check Six]

Great. Looking forward to your weights! I have a pile of very straight grain 2x3s that I scored from a local lumber yard. I have them slated for wing ribs for a project I have in mind. I'll use aluminum spars, though since I have them in stock.
Tom

[Marty57]

Been a while ........ but progress for sure. After a three month break (family stuff) I got back at it and finished up a few things on the flaps and ailerons. With these ready to cover I can now finish installing the second false spar/cove, pulleys and a few other little things on wing #2. The next big project will be the fuel tanks; I plan on fabricating my own. I have been debating using a sheer plate (wood) rather than the set up with the diagonal tube through the tank bay. I need to make a decision but should be starting tanks here in a few weeks. Here is a picture of my finished flaps and ailerons.

Marty57

flaps and ailerons with sandy.jpg

[Tim]

They look good Marty

[Steve Pierce]

Looking good.

[Superchub]

Marty, i hate to see you cover up all that hard work!
It sure looks great..

[skywagon8a]

The next big project will be the fuel tanks; I plan on fabricating my own. I have been debating using a sheer plate (wood) rather than the set up with the diagonal tube through the tank bay. I need to make a decision but should be starting tanks here in a few weeks.

Marty, I used to own a Cessna T-50 (Bamboo Bomber) which had an all wood wing. Granted it was cantilevered and supported the landing gear and engine however the fuel tank was in a wooden box which was built into the wing root area between the engine truss and the fuselage. The two ribs on either side were built up plywood box type structures. The bottom was two layers of plywood separated by wood strips. The top was a built up removable box with ribs inside with a curved airfoil shape on top. My only complaint was in the large number of long screws which held the top on. Usually, since it had been many years since the top had been last removed, some of the screw threads became rusted which made it virtually impossible to remove without damaging the wood strips which held the plates nuts.

The rest of the wing had stainless steel straps and turnbuckles for interbay ties rather than the tie rods which the Cub uses.

I know, before someone comes down on me, that the T-50 is a totally different design in that the wing is one piece and the fuselage is just bolted in the middle of it. My point is only to give you food for thought. Those screws were a pain in the derriere.

[Marty57]

Skywagom8a
What you are describing on the T-50 is kind of what I had in mind. I found reference to a Skymaster 185 on YouTube showing "how to" wing covering videos. I pulled a couple screen shots of the tank bay area; it looks promising for a Cub type wing. I think it is very doable and similar to the metal sheer plate on some of the exp. Super Cubs. The video talks about the tank cover being aluminum. I could use nut plates to attach the cover pretty easily. This sure would make it easy to remove a tank if necessary. I need to figure out details but thinking of using 1/8" ply for the shear plate. I'm going to see if I can get any additional info or pictures of that wing. I attached the screen shots so you can see how similar it is to a Cub wing.

Marty57

[skywagon8a]

Marty, I found the video to which you are referring. It is about a Commonwealth Skyranger 185 wing rebuild. 300px-Commonwealth_185_Seattle_17.05.89R.jpg
You could consider shaping the top of your fuel tank to match the curvature on top of the wing. Then you could eliminate a cover plate. I believe that the Attlee Dodge tanks are made in this fashion.

Take a look at this, http://www.rearwin.com/sparsmain.htm or http://www.rearwin.com/index.asp You may find some good information.

[Bugs66]

Hey Marty, good to hear from you again. Nice progress! The D&E wing uses the shear plate. It works perfectly and eliminates the diagonal tube through the tank. You can then use the plate as the shelf for your tank. I ran two straps on the bottom for good measure, but probably was overkill and not needed. Put two straps on top with tensioners to immobilize the tank. Another benefit is you can make your tank take up the full center rib profile for more capacity. For the aileron balance cable, weld in a pass through tube, or just notch the top corner of the tank. Now you just have to translate on how to do it (shear plate) with wood. The Skyranger method looks ideal.

[Marty57]

Hi Bugs,
Yup, been busy these past few months. I like the idea of a couple of straps on the bottom and top to support the tank. I plan on shaping the front of the tank so the aileron cables will clear the tank. I like the idea of being able to remove the tank without having to remove any bracing or cables. On your set up, do both aileron cables run through the same tube in the tank or is the aileron cable (not the balance cable) run somewhere else? My set up on the spar at the pulleys is very similar to yours.
Thanks,
Marty

[Marty57]

Skywagon8a,
I found the sites you posted, thanks. I sent a couple of emails to them to see if I can get any additional info. I think the pictures I have give enough detail to start. Bugs suggested a couple of straps to support the tank similar to his wing, again real easy to build. I will be securing the top cover with screws and nut plates as this adds another shear plate to compensate for the bottom only plate vs the current diagonal brace in the middle. A tank eliminating the extra plate would save some weight. What I like about this set up is I will be able to remove the tank without taking apart any braces or removing any control cables. Simple is better for sure. I have some design to do but not much. I hope to dive into this late this month after finishing a few other things with the second wing.
Thanks,
Marty57

[Bugs66]

Hi Bugs,
On your set up, do both aileron cables run through the same tube in the tank or is the aileron cable (not the balance cable) run somewhere else? My set up on the spar at the pulleys is very similar to yours.

No, just the balance cable. The other runs down the strut same as regular Cub.

[SpainCub]

Hello all, I was just re-reading this thread as I am gathering info for my 2+2 project.

Marty, did you weigh your wings?

Also, how did you move on the fitting the gas tanks and the idea for the shear plate that Bugs was talking about? Any picture?

Bugs, is yours build the way you mention?

Regards and happy holidays to all!

JM