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Building a Javron Cub

But the elevator cable system is a "closed loop" with tension at all times no matter the elevator/stick position. not like the rudders thatare not "closed loop".

John Scott
 
But the elevator cable system is a "closed loop" with tension at all times no matter the elevator/stick position. not like the rudders thatare not "closed loop".

John Scott

just patched more than one belly fabric from elevator cables rubbing through from sagging(though NOT set up high like his, in those standoffs... that's why I ask..)
 
Mike

I agree, just to be on the safe side I'll do a little UMHV in there.

Olibuilt Factory was .020, Javron uses .025, and Backcountry uses .032.

I am looking into Carbon Fiber, researching.......

Bill
 
Bill, Randy at Plaschem anc has a 3 piece carbon fiber boot cowl that I used with Clyde's ss firewall. It works great for access behind instrument panel and saved about 4 lbs
 
Bill, I never heard of Plaschem but it sounds good. PM Paul Romine. I think he made a complete carbon fiber boot cowl.
 
There are a couple of ways to do it. Titanium firewall from Atlee Dodge that has a 90 degree angle crimped in it going backwards. Building one now and takes a little extra fluting to fit the contour of the boot cowl channels. You can cut the bootcowl off of you existing firewall leaving an 1" or so lip to rivet flat sheet metal to. Another is to buy a stainless firewall form Clyde Smith and a have him rivet an aluminum angle on the back side to attach the boot cowl sheet metal to or if you have a shrinker make the angle yourself. 3003 aluminum works well for the angle.
 
There are a couple of ways to do it. Titanium firewall from Atlee Dodge that has a 90 degree angle crimped in it going backwards. Building one now and takes a little extra fluting to fit the contour of the boot cowl channels. You can cut the bootcowl off of you existing firewall leaving an 1" or so lip to rivet flat sheet metal to. Another is to buy a stainless firewall form Clyde Smith and a have him rivet an aluminum angle on the back side to attach the boot cowl sheet metal to or if you have a shrinker make the angle yourself. 3003 aluminum works well for the angle.

Thanks Steve. Interesting to hear your techniques. Did the shrinker thing on my last one but that was around the bottom, wanted screw on panels. The top was soft with the crimps or flutes as per Piper. Tend to make everything here rather than buy from US due to the cost of shipping and the exchange rate.

Andrew.
 
I got a SS firewall from Clyde Smith Jr. for my -12. He uses the flange riveted to the back of the entire firewall. Instead of riveting, the front of the boot cowl to the firewall, I nut plated the flange so I could screw the bootcowl. It was way more work and cost but in the end, I think it is worth it. My thinking was that if I had to take it off, I could unscrew everything. I used countersunk screws so my boot cowl would fit nicely over the flange of the firewall. I believe this flange is 3/4" wide. Clyde told me I'd have to cut off my cowl attach channels by 3/4" because of the flange. This flange was originally designed on the -14s. He is using these because the flange takes the stress out of the "L" shaped attach brackets that were normally used on the -12s which caused the cowlings to crack in those areas. If you use your own firewall, I believe Clyde will sell the flange seperate. Check them out on his website to be sure.
 
Folks

Finally got around to starting work on this thing. One of the first things I have now noticed is just how fantastic it is to have all the hardware packaged and labeled. The Smithcub did not feature this. Doing a part like installing the front seat? Just get the hardware package labeled front seat and you have everything you need. THIS IS JUST SOOOO much easier and better.

If I were doing a certified rebuild or scratch building I would call Jay at Javron and order a hardware kit.

It has pretty much everything including, cotter pins, washers, fiber washers, bushings, nuts, bolts, screws, etc. Man this would have saved a fortune, a bunch of money, and time from figuring it out, buying a whole lot of unnecessary stuff, waiting for stuff to come in and general grief.

This is just soooo COOL.

Bill
 
Way cool Bill. The next cool thing you will discover is the fit and function of the torque tube, rudder pedals, etc. Good stuff indeed. Have fun.
 
Bill, remember to keep taking pictures and posting them. Like to follow along. I started buying parts from Javron also and sure like what I see.
 
You mean somebody tells you what bolts and hardware to use? What a novel concept. Nothing like that in my "scratch" built plans. By the way, "scratch" means scratching ones head because I often just don't get it!!!
Thank goodness for Super Cub.org :cheers:cheers
Marty57
 
STRINGER INSTALL

Folks

Started out easy by installing the stringers. First thing I noticed was the C channel was a little too long on the left side so I cut off the part I put the black stripes on. Could have left it but hey that saved .120 of an ounce. 8)

P1000107.jpg


Now it looks like this. But notice the bump where the stringer goes into the channel. That will show up as a ugly wrinkle in your fabric job.

P1000108.jpg



So notch the stringer with your belt/disc sander and a file. I prefer to have the stringer just a little proud of the C channel so I can get it perfectly smooth with just a few passes with a file and sandpaper.

P1000110.jpg



I also used a#50 drill and MS24665-132 cotterpins to hold the side and bottom stringers on. If you use #6 screws and nuts it will add about 1 ounce per stringer. Some folks use safety wire but the cotterpins can be put in and out while you are fitting things. One thing about building is that you will put it together and take it apart a BUNCH of times. Don't fight it. Get used to it. There are a couple of places where you can't get the drill in there so you have to use one of these.....

P10001161.jpg


This is an angle drill attachment. You will use it quite often. You will also break the drills often as well so just buy some extra bits up front. I used a #40 bit and a MS24665-283 cotterpin where I could not get the regular drill in there. This is the larger cotter pin in this photo...

P1000109.jpg


And the smaller cotter pin here......

P1000111.jpg



At the rear of the side stringers you will need to bring the stringer inside the fuselage so the fabric will float off the stringer and have a smooth termination. I cut a couple of slits (three in this photo but you really only need two. I used a dremel and a cut off wheel. This allows you to bend the stringer. Looks like this.........

P1000112.jpg


Then take a piece of .020 2024 AL and cut it to fit in the stringer. It will look kinda like this (sorry for the photo).......

P10001131.jpg


Rivit this in the stringer over the slits to reinforce it. I used (4) 3-3 rivets. Sorry I don't have a picture of the rivited part. Thought I did.

Nothing unusual about the bottom stringer.

The top side stringers were a problem. The curves were smooth and looked nice until you got into the right position then you could see a bulge in the middle part. Most people would never see it but I was not happy. I measured all Jays work and as best I can tell it is spot on according to the plans. Sometimes the plans are not good enough. My options were to cut and reweld several doghouses or put small spacers in to make the lines flow the way I wanted. I chose to make some spacers from 1/8th inch thick to 1/4 inch and epoxy them in. You can see the gap in the slot (before I put the spacer in) here.....

P1000115.jpg



I have told Jay about this but the problem is ..... it is according to the plans. So does he fix it then making it non standard? What if you do not see this the same way I do? I don't have an answer....so.....just look carefully at the top side stringers and see if you like the "lines". If not do something like this to make it flow in a way that is pleasing to your own eye.

The top three stringers will probably have to be held on with screws and nuts as there is not much clearance for the fabric so the attachments will need to be low profile. Darn, added 3 ounces.

The top stringer will warp and bow as you try to put it in as it has a pretty good sweeping curve. So you must bend it so that it is not under a bunch of tension. You CAN bend and shape it but it is not easy. I placed it over a garbage can and very gently pushed on it. Move it over an inch or two and press. Keep this up going slowly and carefully until it bends into shape. This will take a while and probably bruise your palms but it can be done without all kinds of expensive tools, just lots of patience. Be very careful that you do not allow it to twist in this process as it will kink in a heartbeat if you are not careful.

Make REALLY sure that your stringers are straight and the lines are pleasing to your eye. The Mark 1, God Issued eyeball is incredibly accurate. You can often "see" variances that you can't hardly measure with a micrometer. Also these are the lines that your cub will have forever. Have you ever noticed that some cubs look really sharp and others just average? You may sit there and ponder it and you can't put your finger on it but one just looks nicer. Well this is part of it. When everything is just right, perfect if you will, the airplane takes on an aura that is greater than the simple sum of its parts and it will move into the "WOW" category.

Just my uneducated opinion

Hope this helps

Bill
 
Make sure the stringer is rock solid at the c channel on the upper stringers. Any movement there will cause the paint to crack. Also, the stringers don't have to bottom out in the clips. Just drill the stringer where it lies and the fastener will hold it true.
 
Those stringers sure look like they could use some lightening holes

Sent from my HTC Evo using Tapatalk
 
I cut a couple of slits (three in this photo but you really only need two. I used a dremel and a cut off wheel. This allows you to bend the stringer. Looks like this.........

P1000112.jpg
Maybe I'm over thinking this but I think drilling holes first to make the slits to might head off some cracking.

Sure appreciate your posts Bill!

Mark J
 
We've always cut the web out of the stringer and then pull the tips together creating the curve necessary. Hold it together with the fabric tape.
 
P1000112.jpg

You could cut a 2x4 with a curve in it, then Cut a slot in the 2x4 just wide enough for the lower part of the stringer. Then push the stringer into the slot to bend the amount that you want. This will keep the stringer from twisting and kinking. Just like a small manual press brake. Then you won't have to cut the relief slots. Of course you won't save the weight of the aluminum which is cut out of the slots.
 
Neat stuff Bill. I like your idea of fitting the stringer to the 3/8" channel. I always hate seeing those cracks in the paint where they transition from the square "U" channel to the rounded stringer. I form the channel at the end with a rounded bucking bar I made that just fits in the channel and allows me to form it with a small hammer into a radius. Here is a picture of how Piper terminated the ends of the side stringers into the fuselage. Great subject because fitting the stringers seems to be more difficult than it looks if you want a really nice job.
98940006 (Medium).jpg
The web of the stringer is cut out and then bent over.
 

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No discussion of annealing the stringer? A wet rag and a propane torch do the job. An eye for a slight "color" change of the metal when heated with the propane torch, then dropping the wet rag over the heated area will accomplish the annealing. In time the extrusion will "re-harden".
 
What about just using wood stringers. The Cub Club offers the diagrams and dimensions of each stringer needed. I used wood stringers for my restoration with no problems. Use a good 2 part epoxy varnish such as Poly Fiber and you will have no problems. I have also been told that a good single part varnish will work well too. Test it out on a piece of wood. If MEK will not take it off after it dries, you should be good to go. The biggest problem I had with the installation was the brackets that hold the stringer in broke so I had to weld some new ones in. The stringer was attached with saftey wire. Using wood will be cheaper and lighter than aluminum but does require a bit of work sanding, routing, cutting, varnishing.
 
Lots of good inputs guys. I appreciate it. I often come out looking like a bit of a buffoon as there are a lot of really sharp folks on this site but if it helps others build a better Cub or learn something new.....oh well. I'll take one for the team.
Kevin, if you want to weigh your stringers it would be interesting to see if they are lighter. It would be good to know.
Here are the weights of my stringers after all trimming etc w/ no mounting hardware. Just the stringers.
Left side - 8.145 oz
Right side - 5.850 oz
Left top - 12.830 oz
Right top - 12.855 oz
Top center - 13.810 oz
Bottom - oops guess I need to get that weight.

BUSHING THE TAIL HINGES

Before we get started on this lets talk a little about reamers. If you are going to build a cub you are going to need a set of reamers. Unfortunately when you drill a hole it does not come out round. It is actually sorta triangle shaped. Not good. We want round holes so the bolt or whatever is equally stressed all the way around. Also works better for things that have to rotate in that hole. So you need to get a set of fluted hand reamers starting from 1/16th inch and going up to 7/16ths in 1/16 inch increments. So you will buy 7 reamers at about 5 bucks each. Give or take. You will use these little suckers ALL the time. Drill a hole a few thousandths undersize then use the reamer to bring it up to size. Thus you will also need a set of numbered and lettered drills.

So all the tail hinges have bushings that go in there. That makes about 18 bushings if I remember correctly. We will first ream out the hinge to get the excess powdercoat paint out and also to make it round again after it got warped during the welding process. The hinges near the edge of the rudder, stabs and elevators are easy to get to. Just put the reamer in the drill or use a reamer handle and put some lubricant on the reamer and go at it. ALWAYS use WD-40, LPS-2, or some lubricant when using your reamer. Not a good practice to do it dry. Go slow and easy. ALWAYS turn the reamer in the clockwise direction only. Reamers are NEVER rotated backwards even when trying to get it out. Always clockwise.
Make one pass only here. We are not trying to enlarge the hole just gently cleaning it out. We want the bushings to go in there with a friction fit, not fall out the other side. If you try to tap the bushing in and it will not go in with gentle taps, back out and ream just a little more until it will go in with a nice fit. The best thing to do here is order the bushing tool from Steve Pierce. It presses the bushing in. But in the event you get in a hurry like me this technique will also work. I use a clevis pin and tap the bushing in with a 4 oz ball peen hammer. What? You do not have a 4 oz Ball Peen hammer? Go hustle your little pink hiney down to Sears and get one this instant. No, a larger hammer will not do. There are going to be a lot of places in this build where you need a light touch. This is one of them. Your set up will look like this.......

P1000120.jpg


We are going to TAP the bushing in. GENTLY Jethro. When it is in the clevis pin should rotate freely and it should come out with no resistance at all. If not....remember those reamer things I told you about? Then next time don't pound the soft brass bushing so darn hard Bubba.

Now the hinges that are not next to the edge of the surface are a little harder to ream. You could spend a bunch of money and buy a long handled reamer, or you could weld a extension on the reamer (if you can do this you should be writing this not me) or you can cheat a little. Use your finger to push on the end of the reamer and to keep it straight, (we do not want it to wobble and wallow out the hole) and you will turn the reamer with a wrench. To all the machinist types out there reading this please don't panic. We are building a Cub not the space shuttle. Remember not to over ream it. Just one pass through, AND DON"T TURN IT BACKWARDS or you will go straight to ..........
Just kidding. Your set up might look like this........

P10001191.jpg


So ...........now you know about reamers. You will use them to clean out all kinds of holes and to make things nice and round. And you now have bushings in all your tail feathers. Pretty cool hugh?

Hope this helps

Flame suit on

Bill
 
ENGINE WEIGHT DATA

This is still a little incomplete but I got these numbers from Bart at Aero Sport Power. Bart is a Cub guy so he understands the weight issue. If you folks don't already know it he is one of the top engine builders out there. Someone told me the top 5 places at the Valdez Short Field TO/LND contest all had Bart engines this last year. He does great work and has an impeccable reputation. Highly recommended.

Weights may vary

All engines have fuel system, 2 mags, starter


ECI O-375-C2A 283.5LBS
ECI O-320-D2A 276LBS
ECI IO-340 280LBS
LYCOMING O-360-A1A 285LBS
SUPERIOR O-360-A1A 284LBS

So a NEW 0-360 is going to be very close to 285 pds, an 0-320 will be 276 or approx 10 pounds lighter.

My 0-360 engine built by Bart (with extra attention to weight) came in at 270. That is with a carb, pmags, flywheel (lightened) and starter.

Bill
 
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