Building a Javron Cub

[pittsdriver]

Sam, I laid it up in place. Four layers of 6oz cloth with a peel ply layer. Put a thin skiff of micro on it, trimmed the edges and sanded it.Only took a couple of hours and it fits perfect with no lumps or bumps. Don

[halestorm]

Cool, I'm going to give it a try on my pacer.

Sam

[Bill Rusk]

Engine arrived from Aero Sport Power. On schedule and on price. I am very pleased. I highly recommend Bart and Sue. Thank you guys. Great job.

Perhaps tomorrow, after a trip to the dentist, I will have a report on flywheels.





We did not waste any time with a trial fit. Mark Rusche and Buck (shown here) were on hand to help.







More to follow.

Bill

[Tim]

Nice Bill, I see you using the P-Mags

Tim

[Greg Campbell]

Very Cool Bill

[Bugs66]

Wow, outstanding!

[docstory]

I thought folks on here said red is an unlucky color for an engine.

[Bill Rusk]

Thanks for the nice comments folks. Docstory - geez I sure hope not.

FLYWHEELS

Went down to the engine shop and weighed a bunch of 149 tooth flywheels. They pretty much all weighed the same.

Average normal 149 tooth flywheel = 106.920oz/6.682pds
Mine after cutting off the pulley = 86.915oz/5.432pds
Skydynamics flywheel = 47oz/2.937pds as reported on their website (http://www.skydynamics.com/frame.htm)


So cutting the pulley saves just 1p 4oz. Really not all that much. But going from a full normal flywheel to the flyweight one from Sky Dynamics will save 3.75 pounds. Thats pretty significant, especially since that weight is way out front.

This is my flywheel before trimming the pulley off



This is my flywheel after trimming the pulley off. My good friend Tom popped it on his lathe and had it done in a flash. Some like DW and Doug K have also drilled out theirs



This is a picture of the Sky Dynamics magnesium Featherweight flywheel.



Hope this helps. You will have to decide what works for you.

Bill

[tcraft128]

DW, care to post a picture of your modified flywheel?

Looking great Bill!

[Amy]

I thought folks on here said red is an unlucky color for an engine.

Doesn't the color red make everything go faster?

[docstory]

Doesn't the color red make everything go faster?

Black is for speed, red is just flashy.

[Amy]

Black is for speed, red is just flashy.

Duly noted.

My car is black . . . metallic even. Bill, are you taking notes? Black for speed, mix in some sparkle for flash and you are set.

[aktango58]

if he wanted speed, (like to go to the tee shirt contest you will be participating in next sun n fun Amy) he would be building a -12...

[Bill Rusk]

Yea, its pretty red. As in.... RED HOT baby. As in.... Sexy. As in..... climbing like it is on fire. After I opened the crate, and regained my vision, I decided to name this Cub..... ....wait for it........................Rudolph!

Floor Boards

I have tried to post both the good, and also my mistakes (even though it is embarassing at times) so others might benefit. I wanted to cut my own floor boards so that I could tighten up some of the holes and make it a little cleaner. It has worked a little but it is probably not worth the effort. Like that last 10% that takes 90% more work. If I were to do it over I would just order a set of floorboards precut from Jay. You can still do the composite material, (or plywood) but he has a fancy CAD machine that cuts them right out. Too much time and effort for little measureable gain on this one. Just my opinion of course. There is plenty of work on building a plane without beating your head against the wall for nothing. In that same regard, I am sure glad I let Bart build the engine for me this time. I built my last one, and again, lots of work. There will be plenty to do.....Keep it Simple. I knew this, I just wish I could take my own advice. I will post more this evening if I have time.

Bill

[Roger Peterson]

Know what you are saying. I went to the lumber yard and bought a sheet of 1/4" ply and spent 2 days making proto floor boards. Then I needed a little more for the final ones. Now to cut up the good stuff and hope I don't mess up.

[NimpoCub]

I wanted to cut my own floor boards so that I could tighten up some of the holes and make it a little cleaner.

I "tightened up" some, and opened up the rear seat bolt holes, and then glued on some scrap cover material over the big holes to help keep the crap out'a the belly. Turns out that was a good brain fart.

[Bill Rusk]

Floorboards

So here are a couple of pictures of the floorboards. There are still a work in progress but you can see a little of the tightening up I was talking about. Just trying to make the holes that things go into as small as I can within reason.








Nutplates again

I decided to nutplate the saddles for the rudder and brake pedals. It can be pretty challenging to get the spring, saddle, washer, and nut all together while on your back and working through an inspection opening with two fingers, so....while this was/is pretty over the top it should make future maintenance easier. It also saved 1/2 oz in case you are wondering.

So here is a saddle and a couple of the mini nutplates for the AN-3 (10-32)




Nutplate positioned on the saddle. Note we took just a little off the corner of the nutplate to make it fit better. It is easier to see this in the next picture.


There is no drill jig tool that I know of for this so you will have to use a bolt to hold the nutplate in position while you drill. I had a nut on the back side, its hard to see in this picture, but it made it easier to reuse it for all the saddles. Also the nut plate will shift ever so slightly when drilling the saddle for the rivets and as a result the bolt will bind up on the side of the saddle when it is going through to the nutplate. There are a couple of solutions to this. After the saddle is all drilled, open up the AN-3 hole by 1/16th inch. Or if you forget and find the problem after the nutplate is riveted on then you can run a tap in the hole part way (you don't want to go all the way or you will loose the "locking" feature). You can also very carefully open the hole with a dremel tool and grinder bit.

Here you can see the bolt, stop nut, and also the slightly angled ear on the nutplate. Ready for drilling.



Drill baby, Drill. Seriously, a drill press is a well worth the investment. Even a bench top model will be very very handy. It is amazing how much easier it goes when using a drill press Vs a hand held drill. The drill just goes through the toughest metals sooooo much easier. Please consider it a worthwhile investment in your project.



After you drill the first hole drop a rivet in the hole as an alignment pin. Don't squeeze it, you are just putting it in there to help keep things lined up while you drill the second hole. Looks like this.....



Don't forget to clean up the edges of all the holes. With AL you can just spin a larger bit with your fingers, with steel you will have to use a drill, but don't get carried away. It only takes about 4 or 5 revolutions to clean things up.

It might look like this. Wear cloves to protect your fingers. Be careful folks. Spinning objects can remove flesh, fingernails, and even fingers.



Countersink the rivets like this............



And the finished product. There are 14 of these little saddles. It will pay dividends later. This is a delayed gratification thing.




OK, that is about all I am going to say about how to do nutplates. You should be well on your way now.

Hope this is helping someone.

Bill

[Crash]

Hi Bill

What are you doing for power distribution? Have you considered solid state? These (ZL-BP4) are simple, light, and adjustable to fit draw needs. Also take a look at their main buss (ZL-MB50).

http://www.ztronlabs.com/products.php

Take care,

Crash

P.S. I just TIG a high temp lock nut to the back of the tabs.

[Bill Rusk]

Wow, hard to believe it has been a month since I posted on this. I have been busy with a trip to Front Sight and also to Alaska. Time to get cracking.

Crash - Thank you. Yes I will be using some Ztron products. Seems really good.

TRIM

If you are using electric trim you will want to have limit switches to stop the motor at the end of its travel to keep from frying the motor, wires, or popping CB's all the time. I used these on the last build and they worked great. They are Burgess V4LS micro switches. I attached them to the yoke by drilling and tapping for 4-40 screws. Drilling and tapping a hole is not that big of a deal folks. Get a Tap and Die set from Sears or where ever. You will use it often, even if just to clean up and clean out threads. So you drill a hole of the appropriate size, there will be a chart to tell you what size drill to use for a given tap, then you screw the tap in. Tapping a hole is kinda like drilling except you just go slower. There are all kinds of good instructional videos on you tube to learn about taps and making threads. Don't be intimidated. It is really not hard. So here is a picture of the tapping of the holes in the yoke for the switches. Note the tape wrapped around the tap. This is used so you know how deep you are going. Good for drills too.



Don't forget that when drilling, tapping, and things like that you need to use some type of lubricant, cutting fluid etc. This is one that I like to use. Pretty widely available.



And finally the finished product.




Another thought. MMR (being the engineer he is) pointed out that it would be better to have the switches fixed and let the yoke move to them. This prevents the movement of the wires which can fatigue or be damaged. Good idea, but a little late for this build. You would want to have Jay weld on some tabs to attach the switches to. I did it backwards and I have tabs welded on for the stops. You would want to mount the switches to the frame and put the adjustable stops on the yoke. Either way will work (worked fine on my last cub) but this would be a better solution.
More trim stuff tonight.

Bill

[skywagon8a]

Bill,
Did you tell us what your wing plans were? Recently I have been rigging my BackCountry Cub. One of the things which I have discovered is that there are about 4 degrees more down travel on the ailerons than up. I'm getting aprox 20 up and 24-25 down. Yes, I can restrict this with the stops except, that I like the idea of 20 degrees up. This differs from the Piper spec of 18 +/- 2 degrees for both up and down. Though it does fall within these numbers when using the +/-2 * with more down. The Piper spec implies that both up and down should be the same. I have rigged the ailerons to be neutral with the stick in the center. There does not seem to be any way to tweek it so that both are the same.

I measured the aileron horn pivot point in relation to the cable attach points. It is definitely set up to produce more down than up. This appears to be backwards to that which would reduce "adverse yaw". I would think that the aileron horn should be redesigned to allow more up in relation to down. The up horn can not be shortened for more up as the clearances are at a minimum now.

I would be interested to hear what others have to say about this. Is this the way that Piper did it?

[cgoldy]

I think mine worked out the same as yours mr sky wagon. I will be interested in any comments as well. Maybe they are meant to be drooped!

[Bill Rusk]

Pete

I have not received my wings yet and have not really gotten into that phase of the project.

Jay at Javron has received the first batch of new stamped 3 piece ribs. They look great and weigh in at 8 oz. This is about 8 ounces lighter than some of the other experimental ribs and pretty close to the factory rib weight. This will take close to 8 pounds out of each wing panel alone. Working on some other ideas as well. Jay is planning (trying) to have two wing panels built and on display at Oshkosh. After the show he is planning to load test the panels to failure. The data from that will be used to reinforce the wings, if necessary, to achieve a wing that will handle a 2200 (or 2300, I can't remember which) load. He has been working with an aero engineer on this project. When he is done my understanding is he will offer the wings both as a kit, and also fully built. So, in a nutshell, I will probably not get my wings until this fall sometime. I will look into rigging, control throws, and other ideas and post here as I go.

I played around with the trim a little, just doing the "experimental" part. Using the trim motor from McMaster Carr, I put the scale on the elevator and had a friend press down against the trim to see how much force it would take to stall the motor. It consistently slowed down at 50 pounds and would stall at 60 pounds. Stop to stop takes 23 seconds. I got another motor from the hobby shop (Radio Control airplane motor) and it bolted directly into the gearbox. Shaft size was the same so I was able to use the nylon gear from the McMaster motor. The shaft from the McMaster motor is splined and they drive the nylon gear on cutting the groves in the gear as it is driven on the shaft. The new motor has a smooth shaft so there is no resistance to slippage except friction. The new motor gave me a stop to stop time of 14 seconds. Much faster. It also had much more torque such that it was still turning at 90 pounds of force, but that is where the gear started slipping on the shaft. Bottom line is the motor is too fast, and the drift, after you remove power, is several revolutions. This would make it too hard to fine tune, or finesse the trim. The McMaster motor is fine and worked well on the last cub but it is fun to play around and see what else you can do. It would be a hoot to explore this more but I need to get this thing done so I doubt I'll mess with this much more.
Pictures in a moment.

Bill

[Bill Rusk]

My good friend Juerg came over from Switzerland for a conference (he is a PHD in Aerodynamics) and he managed to spend a couple of days with me before returning home. He is well along at building a Hatz biplane so we took a couple of flights in mine and then I put him to work in the hangar. Guest have to work for room and board at my place.



In order to keep the Jackscrew from riding up and binding the motor I put a bushing in on top of the jackscrew. Here you can see where I have placed a regular washer and also a thin washer on the shaft. After drilling the bushing the thin washer is removed. This then gives a little play so it does not bind.







After the bushing is in I will drill through the frame and bushing and put a AN3 bolt in there. Sorry I don't have a picture of that but I'll get one in here in a day or two.

I also ran the wire to the trim motor and tail light/strobe. Laced it to the frame with rib stitch cord. I used a little shrink wrap at each point and then put a drop of superglue (hobby shop item, Zap- med visc works well) on the lacing to keep it from coming undone. On the last build I ran a Poly-Flow clear tube from tail to cockpit and ran the wires in it. This is great for protecting the wire and also for ease of replacement but my gut was and is telling me this was overkill so I just laced it in this time. If I do ever get a broken wire it will take more effort to replace it but I think that has a pretty low probability of happening. 2 wires for the trim motor and three for the tail light, so 5 wires braided together. The tail/ strobe will need 4 wires if you want to synchronize the strobes to the wing. I prefer to have the strobes flash randomly so I did not run the forth wire.



Wire laced and glued to rudder.







MMR has been super helpful on this build. Here he is working on the wire. Great guy.



Pictures showing the wire lacing.



More to follow

Hope this helps

Bill

[tempdoug]

Bill another possible source for gear motors? http://www.surpluscenter.com/sort.as...c&keyword=GIDD or these http://factory.dhgate.com//miniature...p39616184.html

[Bill Rusk]

Here is a picture of the adjustable, double nutted screw, stop of the micro switch that acts to stop the trim motor when it hit s the end of its travel.



Picture of the bottom bracket with the hole in it but without the double nutted screw installed just yet.




If you elect to run plastic tubing to put your wires in, one of the problems you may encounter is that the tubing is shipped coiled up and it can be a pain to get it straightened out. Put a big heavy clamp on the bottom of the tube, hang it from something and fill it with boiling water. It will straighten out nicely. It may take a couple of shots of water depending on how straight you need it to be.






I have also started on the boot cowl. Here are a couple of pictures showing the use of poster board and cleekos. Normally a Javron Kit will have the boot cowl already fabricated for you, but I wanted to make my own as I wanted to copy Darrel Starrs 3 piece boot cowl idea.






Bill

[Bill Rusk]

Rivits

A little about rivets. Cool little device that has lots of applications including on your Levis.

Here is a photo showing the basic two types we will be using. On the left is a classic round head, domed model and on the right is a countersunk flush rivet.



The flush rivet has one BIG advantage. You can sand over it. The domed rivets are much harder to work around when covering and also anytime you try to sand around that area you will take the primer or paint right off. So with that background I'll be trying to use the countersunk/flush rivets as much as possible. In order to use a countersink the material needs to be relatively thick .032 or better. We will be using .020 and .025 AL mostly so the other technique is to dimple the material. This bends the metal inward and gives a pretty good flush rivet without cutting the metal away like a countersink does. Here is what the dimple dies look like. They are not expensive, 15 or 20 bucks a set.



This is what they look like in a squeezer.





Sometimes the rivets will be too far in from the edge to get the squeezer in there so here is a technique that will work. Put the die in the vice, I used a little bushing to get it up off the vice and it also protects it from the vice.



Then a couple of taps with a hammer on the other part of the die and you have a nice dimple. There are tools for all this but when you only have a few dimples to make it will work to get you by rather than borrowing or investing in a tool. Again I used a bushing to protect the die.



So here we are squeezing some rivets.




And here is what it looks like. This is a brace at the joggle where the bottom side skins will attach to the boot cowl.



And from the inside.



And the boot cowl in progress.




Hope this helps a little

Bill

[fancypants]

Bill,

I don't see the thrustline mod spacers on the bottom engine mount attach points. Is it built into the engine mount? Or are you foregoing it altogether?

[Bill Rusk]

Definitely NOT forgoing one of the best mods ever for a Cub. It is built into the mount with royalties paid to Mark. That is actually just a test mount. Mine is being welded up now and will be a little lower so I can get the nose up kink out of the boot cowl to engine cowl junction.

Bill

[pittsdriver]

Definitely NOT forgoing one of the best mods ever for a Cub. It is built into the mount with royalties paid to Mark. That is actually just a test mount. Mine is being welded up now and will be a little lower so I can get the nose up kink out of the boot cowl to engine cowl junction.

Bill

Bill, Now the lower cowl will be closer to the bottom of the engine. Will you have room for the exhaust? Don

[Bill Rusk]

Exhaust will be in front so I think I'll be OK.

Thanks for checking me.

Bill

[Steve Pierce]

These C frames work nice also. Ask anyone that has built an RV to borrow theirs.
http://www.eaavideo.org/video.aspx?v=1803209366

[Bill Rusk]

Steve

I can't get the link to work

Bill

[Bill Rusk]

Thanks Steve. Lots of good info there.

Bill

[cubdriver2]

What happened to Bill the weight saver, I'm looking at your photo of the double nutted screw stop for the micro switch in the tail. They make some nifty nylon nuts and bolts that could handle that job.

Glenn

[Check Six]

Bill,
Is there a reason you joggled the top cowl instead of the bottom cowls? With the bottom cowls joggled & slipped underneath the top cowl, it would tend to be more weather/rain resistant.
Tom

[Bill Rusk]

Glenn and Tom

Great ideas. Thank you. The first version of that cowl did not come out to my desired level of fit/finish so I will do it again. I will see about incorporating your excellent suggestion Tom.

Bill

[behindpropellers]

I would red loctite the bushing in.

Tim

[Steve Pierce]

Bill, I left the top on this one flat and broke an angle on the side pieces to stiffen the panel and allow the water to roll over. Not sure if you can see it in these pictures. This is in 4 pieces, top, sides and bottom.
DSCF0440.JPG

DSCF0442.JPG

DSCF0443.JPG

You can barely see the broken angle at the top where the nut plates are.

DSCF0444.JPG

[Bill Rusk]

Folks

I redid the boot cowl top a couple of times until I got it right. Part of the problem was that I was over shrinking the edge as I bent it around the firewall and if you then try to open it up to fit it around the firewall it will immediately split at the edge. So shrink a little at a time. Go slow and be patient, or better yet, just accept the very nice unit Javron provides and don't get weight greedy like me.
Here we are putting the instrument panel attach fittings on. Be sure to drill your holes in the instrument panel so that it pulls the boot cowl up tight into the top lip of the panel. Basically drill the holes a little low (further from the edge of the panel).



This is what the fold over part looks like. I used 2024 T3. This is a little too hard to work so I annealed it by using the Sharpie and propane torch trick. Folks, I am not a pro. Like most of you I had never done this so I called someone I knew and he was kind enough to give me a little lesson. When you hit parts of the build where you are into new territory don't hesitate to call in help. Thats how you learn. Then be sure to "pay it forward". This is how it came out.



Most of the "Kit" planes are using .032 for boot cowls and forward cowls. The factory used soft 3003 or 5052 at .020 thick. If you can go back to .020 2024 T3 you will be stronger than factory and your weight savings .020 Vs .032 will be close to 10 pounds. Again, I am not trying to build an airplane that is paper thin and will not hold up, I am just going back closer to the stock cub. Seems like it worked just fine for the last 50 years. Another cowl shot.



Sidebar - I have been given grief for using a cheap piece of plywood on a couple of saw horses for a table. My neighbors lament that I do not have a real work bench. Actually I rather like the fact that I do not worry about my work table. It is nice to just drill right into it, cut on it, paint, glue etc. When it is all over I just chunk it in the trash. It saves a lot of time by not trying to "protect" a bench by always having to have a scrap to drill into etc. Like this........






This is the tool that Steve Pierce was referring to in an earlier post. I finally got off my rump and borrowed it from Buck. He has every tool known to man. Great guy to have for a friend.




Hope this helps. More to follow.

Bill

[Bill Rusk]

If you end up using the electric trim like I am doing you will probably find that you will need to shorten the shaft of the motor and also the jackscrew to get it all to fit properly. We took a little off both rather than try to take it all off one part. MMR is holding the motor so you can see what I am talking about in this photo.



Ok, so now that the boot cowl is pretty well done we move on to the windshield installation. For me this is probably the most difficult part of the build. These things just do not line up worth a flip and it takes a LOT of monkeying with things to get it right.
First, start by watching this video made by BackCountry Cubs.

http://www.viddler.com/v/fac637a1

Thanks and cudos to Wayne Axelson and John Gordy for putting this video together. If you are building or planning to build this is a great video. If you can figure out how to download and save it, I would recommend you do so just in case it gets corrupted, erased, etc. Watch it several times. There are other ways to do this but this is the only video I know of, so if some of you other pros have a better idea please do a video to help those of us less skilled. One thing I like to do is get the top set of holes drilled so I can clecko it in. This makes it sit in the same place each time you put it in and out for test fits. You will put it up and down many many times in this phase.





Drill small now so you can use cleckos but don't forget to drill larger holes later so that as the plexiglass expands and contracts in the wx it does not start a crack at the screw holes. Generally a silver colored clecko will fit in a #6 nutplate (not made for this but it usually holds) and a copper clecko will hold in a #8 nutplate. Hint - be sure to get the sharp point drills for plexiglass. The ones Aircraft Spruce sells do NOT WORK and will crack your plexi every time. The ones sold by by US Tool or ATS work much better.



Sharp point is good. Flat point is bad. I also like the hole transfer pin on the left. You drop it in a hole, put your sheet on top, tap it with a plastic hammer, and it leaves a perfect little dent in the metal, or plexiglass, where you need to drill the hole. I prefer this to a duplicator as it lets you drill it off site rather than trying to drill the hole with the part in place. Opinion. There is a place for both options, but I wanted to mention this one as some may not be familiar with transfer pins. Very handy, I use em all the time.
So now we have put the nutplates in the top channel from a previous post. We have positioned the windshield and used the transfer pins to mark the windshield for the top holes and used cleckos to hold the top of the windshield in place. Do NOT drill the sides of the windshield until all else is done. Trim the sides but don't drill until later.



I like to use a cut off wheel on a die grinder to cut/trim the canopy. Looks like this.





You will also be using a mallet with a rubber end on one end and a hard plastic on the other end. Like this......



Follow the video. Find the center........




I wish I could give really good directions for installing the inner windshield strip but this one is tough. Or at least it is for me. I can tell you from a previous build that you can NOT rivet it in unless it is laying really flat. If there is any gap between the strip and the boot cowl the rivets will pull the two parts together and buckle it and make a real mess. Do over. This is another part where you may want to call in the help. You will be shrinking the center third and stretching the outer thirds. Tapping with a hammer and dolly, stretching again, fitting, bending and generally working it into position. If you are one of those really gifted folks you can get the strips to both fit together with no rivets, just the screws and nuts holding both strips and the windshield in place. I admire you and wish I was that capable. Perhaps you can teach me how to do it sometime. I saw a Cub in Caldwell ID, Joe, Red, Pops Dory and Steve Tubbs territory that was perfect. Don't remember who did it was it was a thing of beauty. I'll see if I can find a photo.

Bill