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Building a Javron Cub

I continue to really like the EarthX in my experimental. Having it mounted right close to the firewall like we both have ours really saves a lot of wiring run. Nice job with that crimper tool, geez even the heat shrink looks perfect!

That is the master relay. New technology. Can be found here. Much lower current draw. http://www.ZtronLabs.com/products.php

Mark came over yesterday and we got a few things done, went to lunch, then did a little shooting. Great day.


Riveting the cowl door reinforcement on. I had to remake the right cowl door. I got ahead of myself and riveted this reinforcement on before I finished trimming out the door on the last one and that did not work. Doh! You are going to make mistakes folks. Accept it. Fix it and move on. Some folks make fewer mistakes than others. I make LOTS of mistakes. I have just learned to accept it,....:(


Mistake therapy!! I lowered the engine mount 2" (actually Javron did it, at my request). I really like the over the nose visibility, and the appearance. A little more akin to the PA-11 lines.

Here is a link to a very professional video, 3 minutes, with a couple of WOW moments. Very nice.


Hope this helps

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Looking great Bill. Here is an alternative crimping tool from Harbor Freight for the big wires.
and some wire cutters made by Channel Lock.


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Great input Steve. That is probably less expensive than the tool I got and probably works just as well. After all, for most of us, it does not get used all that often.

att. bill , ref, you post #'S 1326 and 1329

, on looking on the "Ztron labs" web sight , it looks like the ZL-MB50 ,is only rated for 50 amps,
(most starter could draw 500 amps).
and if you look at the their (ztron) elect wiring drawing page on their web sight , you will see that the ZL-mb50 is ,hooked up "ie.getting 12 volt" from the battery contractor , and it looks like the suggested usage is for a it to be used a electronic buss switch.
..please check usage. Good day rick
imho-imbw,,,,,,i my humble opinion,i may be wrong
Hi Rick

The Ztron solid state relay was never intended to be a starter solenoid or feed a starter solenoid. It's for the main power buss only. You still need an old 1 1/2 lb starter solenoid (haven't found a light replacement yet... anyone?) in the system. You don't wire the starter solenoid through it. You come off your battery + post with two leads. One light gauge wire to the buss relay (Ztron) and one larger wire to the starter solenoid.

BTW... http://www.skytecair.com/Wire.htm

Take care,

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At the bottom of there brochure this is what it says

The ZL-MB50 cannot be used between a battery and a starter motorcontactor. It is suitable for use after a Battery-Contactor if one is used ordirectly off the battery and an electrical bus.


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I realize this isn't a 737, but Dave has been teaching me about what happens when you go to emergency power in one with those engines hanging low. Kinda got me to thinking, I know we're not talking huge numbers in any direction (thrust, distance from original concentricity, etc) but what if any changes do you expect with power up, or down? Sort of seems like ordinary power changes may have more impact on frequency of trim???? Also, what about "oh crap" moments, full on, or full off, abrupt and extreme power changes, expect much change there? Has this already been done and I'm just asking redundant questions because I'm to stu stu stupid to look it up for myself? (sorry can't help but throw a Waterboy quote in every once and a while)
maybe; One idea to loose the master relay ,is to “Google”;battery disconnect switch with lever kit.

Or may be look and see if this part will work “via ( JEGS car parts ) part # fr1003-2
a switch would be better than the master relay ,with the master relay drawing almost 50 to 70 watts of power just being energized...

Good luck, good day / rick
thought of the day ' Never get between electricity and where it wants to go. (Red Green)
little wing, That is a valid question. The trim change which you address is related to the distance that the thrust line is above or below the vertical center of gravity/center of drag. In Bill's case it might work out to be just right since he is going to be on amphib floats. Without the floats it may be more pronounced. In Bill's case, I would be more concerned with the prop tip being 2" closer to the water. Water does a lot of damage when the splash hits a fast turning prop.

An airplane like a Lake does have a large pitch change moment when the power is changed, since the thrust line is several feet above the vertical CG.
Excellent post Pete. Actually dropping the engine just gets the prop where it was pre thrustline mod. That kicks the prop up a couple of inches. By lowering the engine I am trying to get rid of the kink in the cowl line caused by the thrusline mod. There is little difference in the trim from std to thrusline and then back. CG would play a much bigger role in trim required. But as Pete mentioned, it does make a big difference when the thrusline is well above or below the longitudinal axis.

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Bill, Until you mentioned it, I have not even noticed that small kink in my Cub. However now that I think of it, lowering the center of the crankshaft at the prop and eliminating/minimizing the kink will change the airflow angle against the base of the windshield. That alone will reduce some drag giving perhaps a bit more speed.
Airframes Alaska is AWESOME!!

Just gotta say how pleased I am with Airframes Alaska. I sent them bits and pieces of three 3200 tailwheels and (using the good parts) they built up two basically new tailwheels at a very reasonable price and in a timely manner. Jason called me to update me several times, on progress, price, shipping etc. In short they treated me very well, and like you want to be treated by any business. I have been, and continue to be, very impressed with these guys. Highly recommend.

Javron Strut Update

Jay made several test struts and took them to Univ Of MN at Duluth, Engineering Dept, and tested them to failure. He lightened the end inserts and they all passed with failures coming in other places, in one case shearing the bolt where it attaches to the wing, at around 18000 pounds. Thus he will have struts that will be very close to the Std Univair/Piper strut weight, but they will be stronger. That is pretty cool. So look for Javron struts to weigh like std struts but have the strength of the HD struts. He still has an engineer going through all the test results for verification and analysis but the initial report looks really positive.

Been kinda busy of late but will get back on the Cub ASAP.


Wheels and Brakes

My previous Cub had the Grove Aluminum Wheels(#60-1) and single puck Grove brakes. The standard package that came with the Nick Smith Kit.


This is a picture of the single puck unit on top and the double puck on the bottom. The brake has a small circular (about an inch or so in diameter) piston that looks like a small hockey puck that is pushed out with the brake fluid, when you press on the brakes, and that puck is what presses the brake pad against the brake rotor and creates the friction that causes you to stop. The double puck unit on the bottom has two of these pucks and thus gives much better stopping performance. You can get by on single pucks, even with 31" bushwheels but the double pucks are much better. So I upgraded this build to the double puck unit from Grove. The single puck unit weighs - 26.9 oz and the double Puck unit weighs - 33.59 oz. Thus for much less than twice the weight you get twice the stopping power. Pretty cool. So.....the switch to double pucks adds 13.38oz (less than a pound). If you are always going to use 26" or smaller tires the single puck units should be just fine.


Other side of the brake calipers. Easier to see the single puck Vs Double puck set up.

Sidebar - ROBBIE GROVE - Robbie Grove makes wheels and brakes. http://www.groveaircraft.com/
He makes a fantastic product, is a brilliant engineer, and runs a good business. He does what he says he will do, stands behind his products, and is a good man. Furthermore.....
HE IS A CUB GUY.........he owns a SuperCub and visits this website everyday. He does not post much but he knows what is going on in the Cub world. And, although it is not on his website, he makes a Brake Master Cylinder set up for Cubs...........Javron carries them........


On my last build I used the Dakota Cub Brakes (unit with the red top) and this time I decided to try the Grove units (part #693-1). Figured if everything else was Grove, and worked, well might as well go Grove all the way. Here are a couple more pictures.....




The Dakota Master Cyl shown weighs 25.67 and the Grove weighs in at 24.28. Not much difference there.
I believe these Grove Master Cylinders are experimental only at this time. Absolutely BEAUTIFUL WORKMANSHIP!


Grove makes wheels in Aluminum and Magnesium. The Magnesium wheels are much lighter but perhaps a little more sensitive to corrosion. If you are going to land on a lot of beaches, or live on the Gulf Coast, you might want to stay with the Aluminum models. If you are willing to take the time to care for the Magnesium units they are considerably lighter and don't cost very much more. These are both 6.00x6 wheels. The Aluminum weighs - 87.61oz The Magnesium unit weighs - 68.63oz. Over 1 pound per side. Thats pretty cool.


Here is where it gets really cool. I called Robbie Grove to ask about wheels and brakes and, after introducing myself, he says "Oh yea, I know who you are"
Like I said he reads this website. So I tell him I am a weight nut and he understands. He says he might have a set of light weight drilled rotors for me. Yahoo!!!!
I don't know if he really stocks these or not, but I'll bet if you called and groveled a bit (you are going to have a tough act to follow - I'm a pro) he might come up with another set.
The rotor on the right is a Grove unit that undrilled weighs 45.05oz but I had drilled out and it came in at 41.0oz.
The unit on the left is the Grove drilled unit and it weighs in at 34.2oz. That is a solid 10oz lighter than his standard unit. And boy is the workmanship beautiful.

So....what does all this mean. By switching to the Magnesium wheels and Grove drilled rotors, I was able to upgrade to double puck brakes and still saved 48.76oz or 3 pounds.
Better,.... and 3 pounds lighter. Ya gotta like that.


This is the window channel. I got it at Stoddards in Alaska. It is very nice and about 1/2 the price of the Univair stuff. They normally sell it in 8' lengths. I have the left window without the fixed forward triangle part so they were nice to sell me an 8' section they cut in half and a 4' section. Thus I got 3 4' pieces. A little overkill but it works out much much cheaper than Univair.


Got my oil cooler from Pacific. It is the 8000081 unit. 10 row and very light. Weighs - 36.59oz The Stewart Warner oil coolers are fine units and Pacific sells those too, but they are MUCH heavier. Like 2 to 3 pounds heavier. This is where guys end up adding weight without realizing it. "Well... my buddy has a Stewart Warner so they must be good so I'll use one too". Buys it without ever realizing he just added 3 pounds for nothing. Anyone?.....Bueller?....Bueller?......

So, I got home from work Wed with a massive head cold. Figured I would at least take a couple of photos and make a post. How hard can that be? Ouch....bad idea.....that 20 minutes in the hangar wore me out. Gonna be a couple more days of R and R before I can function again. I'll get back on it when I can.

Hope this helps


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Wheels and Brakes
This is a picture of the single puck unit on top and the double puck on the bottom. .. The single puck unit weighs - 26.9 oz and the double Puck unit weighs - 33.59 oz. Thus for much less than twice the weight you get twice the stopping power. Pretty cool. So.....the switch to double pucks adds 13.38oz (less than a pound). If you are always going to use 26" or smaller tires the single puck units should be just fine.


Other side of the brake calipers. Easier to see the single puck Vs Double puck set up.


Bill, Did you include the adapter mounting plates in your weight calculations? It seams to me that there would be a small weight difference between the two sizes.

Also it will be interesting to see how the drilled rotors work out. A friend had a set on his EDO amphib Cub which used to eat up brake pucks in short order. His disks came from a company in (Tenn?) which were on the market several years ago. The disks were thrown out, being declared unacceptable.
Thanks for all the info on the wheels/brakes and oil cooler Bill. Jay at Javron has the window channel also.
Tom - When I get this thing flying I will be sure and post what worked and what didn't so I will let you know

Pete - You are right. There is a small difference in the mounting plates. I weighed them this morning. The single puck plate weighs 5.3oz and the double puck unit came in at 6.6oz. So about 1.3oz difference in the mounting plates. I didn't think about that when I was weighing things yesterday.

LarryG - Thank you. I did not know Jay had window channel. Probably cheaper too. Missed that opportunity.

Folks I received the following from Larry Vetterman. (Larry used to own the well known, and respected, exhaust company that Clint Busenitz now owns. Larry has about 10,000 hours in Cubs.)

Bill, I completed the flap gap fairings today and just have to tell someone of
the differences before and after. First the flaps no longer shake when down,
and they did a very good job of that at all three settings. Here is the biggest
difference. Going from the second to the third notch made the nose pitch down
very noticeably. I had never flown a cub that exhibited such a reaction like it
and now it doesn't do that either. I guess the piper engineers figured it out
long ago. Over all getting them on made a good airplane fly more like a cub.
I'm not sure if they do anything for cruise but in my mind they have to help.
This is one great airplane. LV


Picture of Vetterman gap seals (note - Oratex fabric covering)


Picture of the "shooter"window in the Vetterman Cub. Advantage - gets window completely out of the way. Disadvantage - mounting bracket next to your head, and you can't partially open the window.


There are advantages and disadvantages to everything. If you are going to shoot out of the window a lot then this is the way to go. Note that Larry left the fixed forward triangular window in place.

Just more ideas. Lots of ways to build "YOUR" perfect airplane.

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There has been a lot of discussion here about "flap gap fairings" which some appear to call "seals". Am I to understand that a lot of the Cubs are flying around without them installed? I have never seen a Cub which did not have them installed as that is the way they were delivered by Piper. Mine are made of balsa and covered with fabric. That 1/2" gap when the flaps are not up is the key to smoothing the flow over the top of the flap when at large deflection angles. The picture which I posed elsewhere here of mine with the yarn taped on shows a nice smooth airflow up through the gap and downward along the surface off the trailing edge. This in the area outside of the prop blast and at a 56 degree deflection angle. The yarn in the prop blast area waves around sometimes reversing. This indicates to me than there is a lot of clean lift generated by flaps extended outboard. I'm also assuming that by moving the flaps outboard the tip vortex does not shake the tail, since I get no tail shake what so ever.

That picture of the "shooter" window shows a good argument in favor of leaving the window post in place. The back seat shooter will be less likely to shoot through the prop.
Nocub - and I also plan to condense and coalesce the info from this thread into another thread without all the extraneous stuff like.....skydiving, juggling, visits on overnights etc, so that those who are just looking for "how to info" won't have to sift through so much BS to find what they are after. It will be a separate thread so this one remains "as is" for those who are REALLY bored and want to follow all the banter.

Hope this helps


THAT...WOULD...BE...GREAT!!! For future SC builders.
Great. Thanks, I'd like to know once you get flying how you like it as compared to the stock set up. I would like to put the full slider in mine during rebuild.
Mine has the full slider. I never flew with the other one. The full slider works for me.


Weighed the baby Bushwheel tailwheel assembly at 12.6 pounds. The same 3200 assembly weighs 7.2 pounds. If you really need and use the baby bushwheel it is worth every ounce but if you are not really doing hard core off road stuff that is a pretty significant weight penalty. I thought it was just a couple of pounds. What I just weighed is just shy of 5.5 pounds difference. That's a bunch. For some folks that might help a forward CG, I guess. It is amazing how this stuff adds up.

Just thought you might like to know.

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