Cables and Pulleys

The next step was running the aileron cables and pulleys.  There was no information in the plans as to the location of the pulleys on the front spar; only limited drawings of the rear spar pulley.  Gathering info for the pulleys proved to be very frustrating.  I tried many locations and gathered pictures from other builders before finally coming up with this set up.  I used 3/16" poly rope to simulate the 1/4" cable that will be used in the final installation.  The difficulty was making sure the cables did not very more than 5 degrees off the plane of the pulley.  I fabricated a bracket with a slight bend to angle the upper pulley and that achieved the correct angle so the cables would run correctly.  The picture below shows the final set up followed by close ups and different angles.

The next two shots are of the bracket I made to angle the upper pulley on the front spar.  I used .090 4130 to make sure the cable tension would not deflect the bracket.

The following are some other shots showing various angles of the pulleys and the run of the cables.

This next picture is a view from the top of the front spar looking down.

Side view from inside the wing next to the "N" compression strut.

This shot shows the rear pulley over the rear spar; the cable clears the spar through the full range of the aileron.

The next step was to make the aileron stop bracket.  I first made a stock aileron stop but that didn't work with the aileron horn that I made for the wood aileron.  I decided to make one that was easily removed with two AN3 bonts and flat brackets rather than the 1/2" tubes as shown in the plans.  The new design worked out well to establish the 17 degrees of travel up and down for the aileron.

Finished aileron stop without the aileron installed:

View from the underside with the aileron installed and the lower stop ground to match aileron horn.

Top side view of the stop with the aileron installed:

This brings me up to date on my wings.  The next step will be to build up the second wing to this same point.  The second wing is currently hanging from the ceiling.  I will need to build the second flap and aileron (parts all ready to assemble) and to install the hangers and other hardware.  This should go pretty quickly as all the parts are made but more importantly I don't have any R&D to do on the second wing.  My next new step will be to fabricate the fuel tank and mounting hardware so I can then cover the leading edge of the wing with ply to finish out the wings.  Getting closer every day!  

False Spar Cove

The next logical step on my wing was the false spar/aileron cove.  I first test fitted a piece of metal cove and realized it would not fit well so I decided to make a wood cove by laminating two pieces of 1/16" ply to match the end profile of the ribs.  I made a jig using particle board to laminate the cove.  Laminating was very easy using epoxy resin to bond the surfaces together.  When removed from the jig there was no spring back and the cove fit perfectly.  I was concerned about how the cove would react under the pressure of the covering material so I made a test box representing the wing aft of the rear spar between two ribs.  My first covering showed a lot of bowing on the cove so I removed the cover and added a top edge of 1/16" ply to the cove and re-covered the test box.  The results were much better.  I still had some scalloping of the edge so I decided to make reinforcements for the cove similar to the ones used by Piper.  I used the Piper drawing to fabricate a similar part out of wood and installed after the cove was glued in place.  I followed that with a edge blocking for the final top ply edge.  The cove came out very nice.  I still have to add the bottom edge but will wait until the wing is flipped over when working on the fuel tank bay.

Below is a picture of the trial fit of the metal false spar/cove.  Not a very good fit at all.

Next, the jig and fabrication of the coves.  This step was surprisingly easy.

Here is a test fit of the finished cove.

Next is the test box I used to see how the cove reacted under pressure from covering without any top edge.  It did not turn out well with out the top edge.

The second time around I added a rig across the middle so I can practice rib stitching after I cover the box a second time.

I decided to make a wood reinforcement as per the Piper drawings to help with distortion of the cove.  I installed the pieces between each rib bay.

Lastly I glued on a blocking edge of spruce along the top edge of the cove followed by the 1/16" top ply edge.  All in all I am very pleased with the outcome of the cove.  I tested the wood cove against the metal to compare weight and the wood was lighter by about 20%.  Cost for the wood cove for both wings was about $40 compared to about $300 for metal. 

Next step is installing the cables and pulleys; a major head ache for sure!

Wow!  I didn't realize I hadn't updated since last April; way too long.  I'll try to make some sense out of what I have done over the last 6 months.  I have had a lot of stops and starts and frustrations with the recient steps but am moving forward again.  So here we go.

First I completed the hardware for the flap actuator.  Second, I purchased pulleys with bearing for the for the aileron cables and made cages and guards. Third I made a wood cove for the false spar.  Next I worked on the proper location for the aileron pulleys and cables; nothing in the plans for this.  In the middle of all this I found a set of lift struts for my wings and figured out how to inspect the inside for any corrosion.

Flap Hardware:  I thought the flaps would be difficult to add to the wing as they are not "stock" on the 2+2.  As it turned out, I simply followed the Super Cub drawings and used or made stock parts.  I did locate the hinges different so the bell crank would not have to mount where the wing attachment plates are fitted to the spar.  Basically I used a left flap on the right wing and a right flap on the left wing.  The correct hardware is located appropriately.  To make this work custom flaps need to be made.  My wood flaps were made to fit this mod.  Below is the drawing that I used to locate all the parts for the flaps.

As I laid out the parts on the spar I realized I had to redesign the hanger to clear the bell crank.  Not a big deal; I redrew the hanger using cad and adjusted the jig and rewelded the hanger as per the new design.  The new design is below.

After installing the new hanger I installed the stock bell crank and hanger along with the push rod made to stock specifications.  The spring I used to test everything came from Home Depot but was latter replaced by the stock spring for the Super Cub.

The next picture shows the details of the flap bell crank stop.  This keeps the bell crank from hitting the spar.  The stop is shown on the first drawing but is hard to see at first glance.

The picture below is the finished hardware installed after painting.  The flap moves down very smoothly and retracts and stops in the full up position.   Final adjustment is made bu changing the length of the push rod.

Next is fabrication of the pulley hangers and cages.  If I were to do this over again I would purchase them rather than make them.  The time spent making all the parts was way too much.  The cost is rather high for each part but I have realized that to finish the plane I need to start moving forward at a faster pace and not fabricate every part.  Below are some pictures of the fabrication of the parts:

I spent about 40 hours making all the pulley hangers and cages.  Cost would have been about $400.  Don't make them your self!  Buy the darn things!!!!

Next I'll show the wood cove false spar build up.

I have finished the wood flap to match the aileron.  The fit and finish turned out much better.  I learned a few tricks and the flap went together much faster.  Here's some finished shots:

And the entire wing; aileron and flap mounted together:

and the gap between the flap and aileron:

The major difference between the aileron and the flap was use of the nails.  I made the mistake of nailing the ply on with the heads flush with the ply on the aileron; big mistake.  For the flap, I used the method outlined in "The Sport Plane Builder" by Tony Bingelis, pg. 69 and 70.  This saved me about 8 hours of frustration and mess.  Live and learn.  I also bought a great tool to pull the nails.  It's called a Staple Jack nail puller.  Check out their web site www.nailjack.com.  I bought it through Amazon (I get free shipping) for something like $25 or less.  This tool is an absolute must.  They have a larger Nail Jack, make sure if you get one that you get the Staple Jack as it is smaller and better suited to this task.  I made up a bunch of nail strips in advanced and cut them as needed when I installed the ply.  It worked real nice; don't forget the wax paper.  After everything is dry the wood strip is split with a chisel and removed leaving every nail head sticking up enough to grab with the Staple jack.  How cool is that.  the strips are about 1/16" x 3/8" pine.  I pre-drill and insert the nails before gluing.  It takes some time but way less than digging out the nails.  I inserted the nails while watching TV.  Here are some pictures of the nail strips.

The above picture shows how I cut some of the strips; they just worked better here this way. 

Next, removal of the wood strip when dry.  This leaves the wax paper and the nail head sticking out for easy pulling.

Nest is the Staple Jack in action.  You could use diagonal cutters for this step but the staple jack made no marks at all.

Yes, I removed the nails on the kitchen table and yes, my wife was home and knew about it.  The next picture shows a section of the bottom with the nails removed and ready t shape to match the leading edge.

The final weight of the flap came in just under 5 lbs.  You could go lighter with a metal trailing edge but that just didn't make sense to me on a wooden flap or aileron.  My next step is to install the flap bellcrank and hardware.  I am collecting and making parts and it should go pretty easy.  The below picture is the first step in figuring out the placement.  I am using stock PA 18 hardware but the location is modified due to the type of flap hangers I used.  More to come soon.

Finished wood aileron

I finally finished my wood aileron about a week ago.  I decided to wait to post till I had some time on my hands after another foot surgery yesterday.  I have been posting on the Super Cub site also but wanted everything here.  I just uploaded all my pictures for the aileron build here so you can see how it all went together.  All in all, the build resulted in a great finished aileron.  Like everything on my project, I learned a lot and had some set backs along the way.  I have already put these into play on the wood flap; just about finished and a lot less time and heart ache.  So, first the finished product then the step by step from where I left off a while back.

Let me show the entire process here from start to finish.  These were built from plans I received from another builder.  I plan on re-drawing everything with cad during my recovery these next few weeks and posting them for other builders use.

I will be building these exactly the same as stock Super Cub ailerons and flaps; just out of wood. The hinges are the same; lengths same as stock; and stock cord length. The only deviation is the hinge location. The first hinge is off set about 1/4" to accommodate the location of my hinges. I placed the hinges according to the 2+2 drawings and they intend use of stock Piper ailerons. I added the wood wing tip; not on the plans and that resulted in the 1/4" difference. The difference is from the inside of the tip rib to the first hinge, nothing different from there. So, here we go.

I got the jig ready to start the fitting and assembly process. I will need to do final fitting and adjustments before gluing but I am ready to begin. Lets take a look where I am at.

First; I extended my table with partial board, and set everything to level. I got the length to within 0.1 degrees and I think that is going to be good.

I used the table to adjust and plane the spar for fit. I removed a bit of wood from the edge and made sure the spar was flat. The ribs need to float on the spar so they can be rotated to establish the wash out. If the ribs are tight than they can't rotate forward without twisting the spar.

Next, I set a string line and secured a piece of wood to support the front edge of the ribs as I fit up the ribs.

I made some "T" blocks to hold the spar true to the angle established by the ribs, The blocks will be screwed to the table and the spar clamped in place to keep the spar from twisting when setting the ribs for wash out.

The second strip above will be shimmed to provide the washout. I placed a 3/8" block under the strip at the end and a 3/16" block at mid point to set a point for each rib tail to set on for the wash out. The next picture shows the blocks, spar, and shim all acting together to establish the 3/8" wash out.

Here's a shot of the other end, no shim. I have a 3/16" shim in the middle of the strip. I will put additional shims to keep the strip level from end to the 3/8" block.

So now you get the idea of how I will be assembling the wing. Next, some pictures of other parts of the ailerons. First, some of the finished ribs and the hinges I made.  These are as per the drawings; looks the same as stock Piper. I still need to paint these metal parts.

     

The next step is to fit all the ribs before gluing in place.

The second picture above shows the tip rib set up with a 3/8" block for washout as per the Super Cub aileron drawing.  Next, gluing up the ribs. I secured the spar at the proper angle and the rear strip supporting the trailing edge creates the proper washout. By doing this there will be no twisting on the spar and therefor no binding induced on the hinge pins.

The containers on the ribs hold lead shot for weight to help keep everything in proper alignment. I also used small rib nails to hold the wood in alignment as the T-88 epoxy dries. I should be able to remove it from the jig tomorrow.  This last picture above shows the attachment of the ribs at the hinge point. Nose ribs will be attached latter along with reinforcement ply and the hinges.

This next shot was from one of those rare Saturday's that I was able to work un-interrupted,
so lots of progress.

First, I made all the nose ribs for both the ailerons and flaps. I used a router with a laminate trimming bit to duplicate the parts. I hadn't made them back when I assembled the ribs with the wing ribs during the summer assembly weeks.  Next, after gluing them on in the shop, I brought the aileron inside to cure the T-88 faster at room temp. Yes, that is our dining room table and yes my wife was home at the time.

Next, I made all the trailing edge stock needed for all the control surfaces.
I used the table saw for this step; pretty easy.  The next step was to fit pieces of trailing edge stock between ribs. Again, an easy task.

The last thing I did that night was to make a template to lay out the locations for lightening holes in the trailing edge stock. The top material will be 1-1/16" ply over the edge material so they will be very strong when finished. I drilled the first two pieces and did a test fit with clamps. After finishing up the drilling I glued all the straight trailing edge material in place.

I was able to get out into the shop a couple of hours after work Monday and get some more steps complete. First, I unclamped the trailing edge and did some preliminary sanding. I will need to do a little bit more before sheeting with 1/16" ply.  Next, I cut some strips of spruce for the spar cap. The spar is capped with 1/4" x 1/2" strips to bring the spar up to the level of the ribs for gluing of the leading edge ply.  Here are a few shots.

You can see I used nails to hold everything in place here to speed things up.  Next step is capping the bottom of the spar; same size spruce strips.  If you haven't built a wood wing then these posts may seem like there are lots of steps and lots of pieces ..... and you are right! The total time involved so far is not much; maybe 10-15 hours. That may seem like a lot but is normal for wood wings. Each step has to dry over night, so you have to take your time. To make a comparison to a metal aileron you would have to scratch build everything, starting with sheet metal and forming all the ribs using a wood block, bending your own spar, and rolling your own leading edge material. Time would likely be about the same compared with wood.  The next picture shows both the top and bottom of the spar with caps in place.

Next, the remaining upright spruce for the ribs needed to be cut and glued in place. I left this out so the rib could be rotated slightly to establish the 3/8" washout.  Gussets will be added to tie the upright to the upper and lower cap strip. Although this seems like tedious and insignificant, this piece will help transfer the aerodynamic loads from the surface to the spar.  Before adding the gussets, I needed to cut and glue a 1/16" reinforcement plate at the hinge locations. The ply is glued with the grain vertical over the horizontal spar and over the spar cap. This laminate will make for a very solid point for the hinges. The hinges will be bolted in place with AN3 bolts secured to a rear .040 4130 plate with nuts secured in place.  lots of step-by-step that is not in any drawings but comes by experience from building wood wings.

Four clamps and time to dry over night.

After final sanding on the gussets I glued them in place. Binder clips from Staples make great clamps. 

Everything inside to dry over night in the warmer house ......

Since I made my wing with the wood tip bow I needed to follow the curve into the aileron. the plans call for a stock trailing edge with 3/8" .035 tube bent for the curve. I decided to go with a wood trailing edge to be covered with 1/16" ply. The curved end was evading me until last night. I came up with what now seems to be the only logical approach: duplicate the wood trailing edge profile in a curved piece of wood. First, establish a curve and make a paper pattern.  Then I cut a curved piece of spruce to test fit from the paper pattern and drilled the holes to match the rest of the trailing edge.  This was test fit, sanded and glued into place.

I decided to build up the matching wood flap for the wing. I needed the flap and aileron hanging together determine the proper location of the hinges. My hinges are stock but will bolt to the flap and aileron spars; making them removable if necessary down the line. The retaining nuts will not be directly accessible but a 1" hole could be drilled for access if necessary requiring only a small patch; more on that latter.

This is the first hanging of both control surfaces; the fit turned out great. The only adjustment I needed to do was a /16" shim under the aileron hinge closest to the flap. That was needed to compensate for an extra washer I had to add under the aileron hanger to align the three hinges. The spar already has 1/16" ply glued to the front and back for reinforcement so I just needed to glue on another 1/16" thick reinforcement piece for the alignment issues. I glued those on last night along with the single 1/16" reinforcement on the front and rear spar of the flap hinge point.

The next step required building the aileron horn.  I had been working away for the about three weeks on steps requiring some "learning curve" and some design work. I fabricated the aileron control horn first as per the plans than modified to remove some sharp corners and excess metal. The horn and hinge are one piece on the plans and I wanted them separate and removable from the ailerons easily. The horn is on the back of the spar and the nine on the front with two AN3 bolts going through them and the spar. The set up worked out real well after a bit of work. The design is very similar to that of a Pacer so nothing very different from what has been done in the past.

Next, I added a solid piece to the leading edge and shaped it to fit the profile of the ribs. This will allow attaching the 1/16" ply in two pieces.  Everything needed to be sealed inside with epoxy before attaching the leading edges.

Next I attached the plywood with aircraft nails to hold the skins in place. This went pretty smooth and I thought I was very happy but.........

The nails proved to be a very big problem to remove. I made a small puller that I thought would work but it proved to be very time consuming to get out each nail. Hind sight being what it is I should have left the nails in but I want a very smooth surface so the nails had to go. Next entry will show the trials and tribulations. After the fact I found a method to set the nails for easier removal but not until they were all in place. I have mother idea for the flaps and other aileron that should be easier. We'll see.

So much for a good idea. The nails were a good idea for holding down the plywood but removing them proved to be a tedious task at best. I had in mind a tool to use to remove the nails. I fashioned a little puller from a wood carving tool to be used in conjunction with a small side cutter. although it worked, it did not work well. Most of the heads were popping off requiring digging out the nails. The combo worked well on flat areas but not at all on the curved surface. Here's the tool:

The problem was gripping the nail low enough below the head to not cut off the head. So, I did some head scratching and decided to use a "hollow drill bit" of sorts to cut around the head of the nail. Here's the "drill" made from a piece of hobby shop brass tubing that just fit over the head. It had to be sharpened often but my dremmel with a small grinder and the brass spinning in the drill made that very easy.

This worked pretty well. It exposed enough of the nail head that I was able to get below the head and tease the nail up above the ply enough to use a very small diagonal cutter to do the final removal. My little puller made from the carving tool now worked to get the head up just enough to use the small diagonal cutters to pull the nail out completely.

Now I have to fill each hole. That won't be difficult. I will mix up epoxy and mix in micro balloons to make a very strong and light weight filler. Using a small squeegee I'll fill the holes and lightly sand smooth. So how to avoid this? I found out after the fact in "The Sportplane Builder" by Tony Bingelis (pg. 70) shows a way to use small nail strips with wax paper. Nails are pre set into 1/16" strips of wood and nailed into the skins with was paper to hold down as glue dries (looks like a carpet nails strip). The wood strip is latter removed and any nails left can be removed using a diagonal cutter. On the Biplane builders site I came across this a thread about this and the builder still had some difficulty removing the wood and nails. 

Next, final pieces of 1/16" ply. this brought everything up to level on all surfaces. There are no bumps, rivets, or screws sticking above any surfaces. This should make for a very smooth surface for applying the fabric.  I also added the ply around the hinges.  Just about done.  Time to install hinges and epoxy everything.

  

Here is a nice shot of the hing bolted in place. 

And here we have the aileron before and after final varnishing. 

I wound up having to adjust the ply under the first hinge as it interfered with the clevis pin but that was not a big deal.  I have the flap about done and will post pictures with the nail strips I used and a very cool nail pulling tool that cut the nail removal from 10 hours to 1 hour.  total weight of the finished aileron is 8 lbs.  I talked to builders with metal ailerons and the weight range was from 7 to 10 lbs so the wood is right in the ball park.  My cost to build the aileron was about $100-$200 (this includes everything for all four control surfaces by the way).  I really only had to buy the ply and a bundle of practice spruce from Aircraft Spruce, everything else I had from building the wings.