Building a Javron Cub

Bill Rusk · Aug 5, 2011

kevin · Aug 5, 2011

Sounds exciting. I'm not really familiar with this kit and hadn't heard about it before you started your search for prospective kits to build. It sounds like you are going in the right direction. I'm sure this will be a very nice kit for you.

You really didn't mention too much about the wings. Are you planning on stock length flaps, inboard to the frame, extended cord, etc? Stock bows or square tips?

Look forward to watching it come together.

Kevin G.

Bobby Breeden · Aug 5, 2011

Bill,

Its very good to hear that you are moving that much closer to getting your new Cub under way. I have a few questions that may not have been mentioned in your post.

From the sounds of it, it seems like you will be building up a cub to be as light and as durable as possible. Does this mean 0-320/340? or 360/375? I really like the concept of a super light plane with an ample amount of power. I have heard of 320's being "massaged" up to 200 hp...

Regarding the wings, Round tip? Square tip? Extended flaps? I remember the switch from BLRs to Micros and I really thought the latter worked deeper and longer to prevent a stall.

Carbon Fiber: Will you be using any carbon fiber in the Cub? Leading edge, bows, cowling, tank covers, floorboards, etc.

Titanium Firewall?

Tail Feathers: 3" extended or stock? Stock should be plenty...

Brakes: the Calumet Cub Heel Brakes are fantastic. They had enough pressure to lock-up 35s any day of the week.

Tires: Assuming you will not always be on floats, what tires do you think you will use?

Prop: Those Catto props are really light and pull great. Also spin up quite well and cruise faster than Borer equivalent.

Fuselage: Will you be moving the engine in any way? backwards, forwards, up down? And last but not least, Wing Incidence. Have you decided to change it from stock? If you do so, be sure to match the tail to avoid trim complications.

The big list you mentioned above has some FANTASTIC changes and ideas in it! I cant wait to see the progress on your new machine. I know you have put a lot of research into this so I am positive you will absolutely love your kit pick.

Good luck and keep us posted.

Bobby Breeden

Iflylower · Aug 5, 2011

Great to see you started friend! I saw a guy with a Javron shirt on his cell phone at Oshkosh. I've ordered parts from him a few times and talked on the phone a few times. Great guy. I was sure it was Jay, I got busy looking at a booth and he was gone. Sorry I missed him.

I like your list, I'm pm-ing you another secret sauce addition to that frame.

In my build, I'd give a lot to have a carbon fiber round tip on the wings. There is so much tomfoolery on the piper round tips. It'd be a huge time saver. Something bolt on like cc's, if not theirs.

Iflylower · Aug 5, 2011

Scott Berry's in AK.

Thought of another...

Not just tie downs in cargo aera, but little tabs that could hook a net from the front of the rear seat up to the top of the crossbar, right in front of the flap pulleys. Saw it up at the airmens show in AK, and never got it done on my frame. Sad. Also, cc uses tabs to hold a little net against the roof for charts and hats n such. Nice.

mike mcs repair · Aug 5, 2011

my thoughts........

Bill Rusk said:
.....

9. Lift rings for floats - these can be welded in or they could be left out and the brackets bolted to the spars as necessary. There are advantages to each. The spar brackets would only be added if someone went to floats so perhaps a few ounces lighter for someone who is not planning on floats but that then requires cutting into the wing fairing and they are not easy to take on and off so they tend to be left on year round. With the weld in ones the holes in the skylight can be plugged easily and the eyebolts are easy to remove or install when going to or from floats.

would think you want standard location like atlee's ones so most lift bars will fit?

10. Extra tail lift handle - Easy to weigh a piece of tubing to get the weight. T

have you considered just putting them on upper longerons instead, we call them "old man" handles, MUCH better force for pushing....
......

20. Longer seat attach fittings for rear legs of front seat. This will get the bolt up high enough so it does not conflict with the floorboard making it hard to get the front seat out.

I like that!
.....

24. Reinforce/brace outside rib of Horiz stabs to keep the fabric from warping it. Also move it 1/2" closer to fuselage to gap seal this area.

I don't think you have a 1/2 ON the stabs to fix that, I think that will need to be done to(shorten) the tourqe tube mounts on fuselage

25. Extend the arm on the bottom of the stick by 1" where the aileron cables attach. Gives more aileron throw to the stick.

can you do that without hitting knees????????

Bill

NimpoCub · Aug 5, 2011

Bill, good on ya!
Definitely inboard the flaps. makes a difference.
I was advised that extending the ailerons didn't make "much" diff, and lots'a work to add a hanger/hinge. Dunno personally tho.
I did most of what you listed, and WISH I had moved the flap handle some. Didn't think/read about that when I rebuilt.
Make some sort of gizmo to be able to close the door window from outside.
Windscreen defroster. Rear seat heat? Soundproofing under floor & inside boot cowls. AeroSport (Bart massaged) engine.
Tabs for a belly pod. DW in Ore. has 3x3 extended gear fer sale. Do a nice job, I'll be lookin' someday.

fobjob · Aug 6, 2011

A tube from the bottom of the firewall to the top front door frame on both sides to prevent the engine from tucking under in a crash and crushing your legs....

skywagon8a · Aug 6, 2011

Mike,
25. Extend the arm on the bottom of the stick by 1" where the aileron cables attach. Gives more aileron throw to the stick.
can you do that without hitting knees????????

I think that you misunderstood. Extending the arm on the bottom of the stick will move the cable further. The stick throw will not change.

Bill,
My Backcountry fuselage was built by Javron.
The plate which is mounted under the extended baggage floor on which the bulkhead "T" fittings attach for the fuel line drain points, was installed upside down against the fabric. It was impossible to install the "T" fittings and connect the fuel lines without an extension "Rube Goldberg" being added between the plate and the "T". The plate needs to be welded to the top surface of the tubing. This will allow a straight run of the fuel lines without any fancy plumbing.

The tubing behind my firewall is in the form of an "X" instead of Piper's upside down "V". This prevented me from using a constant speed prop had I wished. The governor would have conflicted with the tubing. I do not know why this was done. It was not anything that I ordered. It certainly does strengthen the engine installation.

fobjob · Aug 6, 2011

Tempdoug, you're right, my bad; not enough coffee...

mike mcs repair · Aug 6, 2011

skywagon8a said:
Mike,
25. Extend the arm on the bottom of the stick by 1" where the aileron cables attach. Gives more aileron throw to the stick.
can you do that without hitting knees????????

I think that you misunderstood. Extending the arm on the bottom of the stick will move the cable further. The stick throw will not change.
.....

ya my dyslexia in action

Cub junkie · Aug 6, 2011

This is the beginning of what I predict one of the longest running threads on SC.org. Looking forward to it.

Nocub · Aug 6, 2011

Cub junkie said:
This is the beginning of what I predict one of the longest running threads on SC.org. Looking forward to it.

Agreed. I'm looking forward to this build and second the question of engine type?

Bill Rusk · Aug 6, 2011

Kevin.... The wings will be fairly close to stock, round tip, probably 18gal tanks, etc. Still working on that part.

Bob Breeden.... Folks I have had several long and very informative visits with Bob. He is very sharp and does his homework. It will be fun to see what his next build up looks like as well. But, that said, I will try to hit some of his questions

Engine.... still undecided. Had a long and excellent visit with Bart at Oshkosh. I will talk to Ken at Lycon and probably Monty as well. Leaning toward 0-360 but ?????

Planning Micro VG's on wing, pretty stock wing, possibly Keller flaps, and carbon fiber where it makes sense.

Titanium firewall ...yes. Atlee is predrilled and saves 2 pounds

Standard tail, Dakota Cub Brakes (already have) 31" tires (already have) Catto prop (as before I liked it)

I may make some adjustments to the motor mount. That will depend somewhat on the engine selection. Bob offered a lot of insight into this area.

Cal thanks for the PM. Yes I am looking into a CF wingtip bow with the light mount molded in to save time, weight, and as you say tomfoolery. I agree.

Mike excellent inputs, thank you. I will have to look at the stabs again to confirm the set up. It was that way on my Smithcub and I liked it. The torque tube extension just gives more aileron travel with less stick travel and helps with the knee issue.

Pete Thank you for that heads up. I will make sure it is on top.

Right now most of my focus is on the fuselage as Jay is about ready to start cutting metal so I am trying to stay one step ahead of him and I want to make sure I get all my changes right the first time. Thanks to all for your inputs.

Bill

Bob Breeden · Aug 6, 2011

Bill,

That was my kid. Let me know how I can help.

Bob

Bill Rusk · Aug 7, 2011

Oops, thats embarrassing. My sincere apologies to you both. I'll pay more attention in the future. How cool is that to have a father and son both knowledgeable and posting on the site.

Bill

SteveE · Aug 7, 2011

Bill,, on the extended torque tube extension,,, the bottom stringer will be in the way. I had 6 inches or so cut out so nothing can get caught between it and the bottom of the torque tube/cable attach. Built a square out of the stringer material and turned that into an inspection plate. Of course the pod covers it up now, but if you ever need to get into it, you have a cover there and the bottom stringer does not get in the way if a loose pencil finds its way down there.

aktango58 · Aug 7, 2011

Bill,

Sounds great!!!

Try to think about the tabs above the front gear attach for brake fittings. a flat piece of steel strait above the longeron, put a firewall fitting on for hydraulics. You can put both brake and amphib hookup on.

Aft baggage: try out randy's CF baggage maybe. cables stay in same place, and it uses all the room back there for lots less pounds.

Tabs for rear seats up above the rear seat channel. Much easier to use and less holes for stuff to fall through later on...

Just ideas. Great to see you going.

George

Bill Rusk · Aug 22, 2011

Folks

I went up to see Jay at Javron last week and we went over all the changes and mods to my weldments. I will post more on that later but what I wanted to share in this post are the scales I have ordered to help keep track of things along the way. Both for my use and also so that others may benefit from the data. I look on these scales as tools just as a wrench, rivet gun or torque wrench. So while not directly tied to the cub itself they will find much use in the shop. No bathroom scales for me.

I ordered a small scale that will weigh, accurate to a tenth of a gram, up to 12 pounds...

http://myweigh.com/product/ibalance-5500/

And a second scale that will weigh, accurate to less than an ounce, to 130 pounds....

http://www.oldwillknottscales.com/my-weigh-hdcs-6020.html

I ordered from this company......

http://www.oldwillknottscales.com/

Hope this helps.

Bill

cubdriver2 · Aug 22, 2011

I think the DEA tracks who buys these scales but it shouldn't be a problem for you, unless you also happen to own an offroad airplane with big tires that can land anywhere and has LED lights to find little fields in the middle of nowhere in the middle of the night. So you should be alright

Glenn

kevin · Aug 22, 2011

Bill, I was just thinking to myself how your project was coming because I haven't seen any info from you in a while. Thanks for posting your update.

A while back ago, I was thinking about buying a scale from Wal Mart. I thought I could probably find one there.

Bill Rusk · Aug 30, 2011

Folks

Jay has started the welding so I should have weldments in pretty short order. We changed the top x brace a little to accommodate the dual inertial reel shoulder harness set up. This should help with the neck pinch and chaffing of the typical V shaped shoulder harness.

We also set up a lip around the lower door opening such that the interior panels will tuck under this lip for a cleaner and more durable door area. I have seen interior panels bent and torn from sitting on the door sill when getting in, then also the front panel gets caught by the boot as you try to get in thus pulling it away from its attachment and bending it. This mod should take care of that.

We discussed how to get the radio PTT switch on the throttle. Done.

I will be using the lower longerons for the floor boards. Should save a couple of pounds.

I will take pictures of all the mods, and weigh the fuselage both, before and after, paint.

I should mention that a lot of the mods mentioned above in a previous post are really standard mods that Javron does for no extra charge. I just put them all here so folks who are not familiar with all this stuff could learn a little. I must say again how easy it is to work with Jay. He will pretty much build it any way you want.

Mark (MMR) found a different trim motor for me. I have not tried it out yet but on paper it has twice the torque, and spins a little faster. The last one worked just fine but this one should be even better. I will post more info after I try it out.

I am currently working on some weight data for mags, engines etc

I can say a 0-320 Carb, MA-4SPA weighs 52.28 Oz and a 0-360 Carb, MA-4-5 weighs 83.085 Oz. That is very close to 2 pounds heavier for a 0-360 carb. We are going to nail down just how much the weight penalty is when going from a 0-320 to an 0-360. More to follow.

Spoke to Univair

Std rear strut = 7.25 pds
Std Front strut = 11.45 pds

HD rear strut = 9.9 pds
HD Front strut = 14.4 pds

Thus the difference is 11.2 pounds added to the airplane for the Heavy duty struts. You may decide that it is worth it, all I am trying to do is let you know honestly just what you are adding Vs rumor and hearsay.

A Slick mag set up with 2-4347 model mags, harness, and 8 REM40E plugs weighs 189.05 Oz
A Bendix mag set up w/ 2-20 series model mags, harness, and 8 REM40E plugs weighs 238.95 Oz
Thats three pounds heavier for the Bendix. Is it worth it? Thats up to you but now you know.
Working on getting accurate Pmag and Lightspeed info now.

Hope this helps

Bill

Douten · Aug 30, 2011

Saw a throttle body type carb on a exp.180 hp. SC that is tiny and looks like may save a few pounds and now the plane starts easy when hot, only been on a short while but looks like it works great.

Iflylower · Aug 30, 2011

Bill, I remember from a thread a long time ago... HD struts are for heavy snow loads in AK, not for flying. I bought the standard lighter lifetime ones with the thicker forks.

Steve Pierce · Aug 30, 2011

Weighed a stock factory Piper fuselage that has never been used. Still has the part number in crayon or grease pencil on the front tubes with paper wrapped around the front "V" brace and window and windshield trim strips. 97 1/4 lbs. It is primed in some yellow primer with a grayish green over everything except what is papered. Unfortunately had to cut into a rear longeron from someone mishandling it and a lot of linseed oil ran out. I have been weighing a lot of things as well Bill. Will post some when I get to my notes. I do remember the folding seat mod adds something like 2 lbs.

FdxLou · Aug 30, 2011

Bill

The P Mags start paying you back $$$ the minute you start using them. Even if they are a few oz. heavier it would be worth it in the long run, IMHO.

Lou

mike mcs repair · Aug 30, 2011

Bill Rusk said:
.....
Spoke to Univair

Std rear strut = 7.25 pds
Std Front strut = 11.45 pds

HD rear strut = 9.9 pds
HD Front strut = 14.4 pds
.
Bill

check airframes Inc.,
I think... its +3 per rear, and +.5 per front strut... I think thats going from original piper ones....

I think

I KNOW I always used +7. lbs when putting a HD set on.... whether that has changed or not.....????

mike mcs repair · Aug 30, 2011

Iflylower said:
Bill, I remember from a thread a long time ago... HD struts are for heavy snow loads in AK, not for flying. I bought the standard lighter lifetime ones with the thicker forks.

and for wind from behind....

mike mcs repair · Aug 30, 2011

Steve Pierce said:
Weighed a stock factory Piper fuselage that has never been used. Still has the part number in crayon or grease pencil on the front tubes with paper wrapped around the front "V" brace and window and windshield trim strips. 97 1/4 lbs. ...

and more importantly, you have a virgin as far as plum bob for level flight....

would be interesting to hear some of the angles from it in level flight.. the one I measured like that, in level flight was 1.0 deg trailing edge of wing down, firewall 90 deg....

just kinda neat to see how they were REALLY built, depending on which piper jig, not what the blueprint says.....

AkPA/18 · Aug 31, 2011

mike mcs repair said:
and for wind from behind....

I usually know when I get snow----- can't always predict when I get wind from behind. I went with the heavy rear---piece of mind!!!

Mark

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