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Building a Javron Cub

Dave, you were right about the other primers you mentioned. A little quick research indicates they are definitely high end, high quality primers. Unfortunately my quick research also found they are not easily available, at least in Rockford Illinois. They can be special ordered. My PPG store had not even heard of Super Koropon. It is part of the Aerospace line of paints division of PPG. So for you guys just starting it might be worth your time to line up a supplier of one of these primers, especially if you are not going to powdercoat the fuselage. I think Koropon, properly applied, would be about the very best you could do. The application process is pretty in depth, and takes a lot of prep work to get just right. There is more info in the Vans forums. Good stuff. Thanks Dave.

Super Koropon.......anyone can walk into the local auto-refinisher paint store and buy it off the shelf in Anchorage.....We are blessed :)

As to application.........I would not say that I prep any different for Super Koropon than any other paint prep. As it has been said, "...painting is 90 percent prep..."
Fabric headliner

First the back panel. Then the side panel will go in and last is the top panel.



Here is a little video that might help some


Hope this helps

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I am working on several fronts at a time right now so my updates might be a little disjointed. There are other door latches and other ways to do this, but this seemed to work well for me on my last build so I am doing it again. No sense re-inventing the wheel....

This is the lower cowl brace rod......(note the nutplates and camlock receivers are just laying there for example)


I use 4 nutplates for the lower cowl panel and three camlocks with the butterfly (or "wing" ) top to hold the side cowl door down. They are spaced, from the forward end of the brace rod at 2,9,16,23 inches and the door camlocks are at 3, 12,1/2 and 22. My brace rod is 25 inches long. Yours may vary a little depending on your engine, mount, nosebowl etc. Right now just drill the #40 hole and do not install the nutplates and camlock receivers just yet. This will allow us to use a silver cleco to hold the paper patterns and the sheetmetal in place while we trim to fit and all that. You will need a nutplate on the forward end of the rod to attach the nosebowl (seen in the far left of the photo above) and the rear attach point will be a hole in the rod with the nutplate on the angle brace attached to the firewall. Like this....


Note - it looks like I need to clean up the back side of the drilled holes. By the way these holes in the brace rods are much easier to drill in your drill press rather than with a hand held.
This is the front nut plate.....


You will want to have the cowl brace rod nutplates as AC Spruce # K1100-08. They are recessed/dimpled so the hardware can fit flush. The screws that hold the lower panel on and the nosebowl on must be flush so the top part (door or cowling) will lay flat. So the nutplates must have a slight dimple to allow for this. Your hardware will include a recessed nutplate, countersunk washer and machine screw like this.......
The recessed washers are AC Spruce # 04-00397 for #6 screws -which mate to a #6 nutplate like K1100-0
04-00392 for #8 screws -which mate to a #8 nutplate like K1100-08
04-00398 for #10

And the Camlock #'s are

You will need AC Spruce part #'s 212-12N receptacles
And " " 2600-2W cad plated wing studs



This is the spacing I used for the top rail. Yours may vary a little as mentioned but hopefully this will give you an idea of what to shoot for.


As long as we are working in this area. This will be the rod that will hold the side door Up/open when checking the oil, doing maint etc. It is made from the same material as your fuel line, (5052 .375 X .035) Flatten the end about an inch in the vice, drill the 3/16 hole, and leave it long for now. We will cut it to fit later.

Hope this helps

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I'm working on my cowling now for my -12. There are some slight differences but they are some similar design.

Keep up the good work!
Bill, Great craftsmanship. Clearly a Cub you can be proud of. I can't wait until your first flight. Keep up the good work and she'll be flying this fall. Greg
...Hi Bill, a couple of things come to mind.

1. is that a removable front panel for your upper baggage? ...or is it permanent fabric stretched across there? ...point is......I know if I bought your airplane someday that I would need to remove that to load some types of items.

2. cowl brace rod......an idea.......gleaned from the personal watercraft manufacturer SeaDoo.....they have a cowling prop rod that is simply a long tension spring (not unlike a screen door spring). The spring, at rest with the cowl opened up, is straight, and stiff in compression. But when "pushed" in the middle, it folds easily upon itself as the cowl is closed. It would make a great "cowl-prop-open" for Cub cowls, baggage doors, even windows. The setup on the SeaDoo twin sportboat is supporting a quite-substantial fiberglass "hood".

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Kevin, Wendy, and Greg. Thank you.

Dave - My fabric headliner is not removable but I like your idea. Thank you. Take note of that - other builders - a hinged or removable panel back here would be a good idea indeed. Cowl prop rod - another idea to explore.
Cool - there is soooo much knowledge on this site.


This is where the pulley for the water rudder cable will be installed. The cable will come up in line with the inst panel and will hook on a bracket which will mount on the lower right inst panel attach tab. Shown here with the blue tape..........


I will then make a little hook that will go under the screw that holds the panel in (easy to remove when not on floats) and the whole thing will look like this (crude adaptation for photo purposes only)........


You could have Jay at Javron weld this plate in for you when he welds on your float fittings. Usually the sub boot cowl will work to hold some type of fitting here but I will not have a sub boot cowl, this area will be fabric, so I needed a little structure for this fitting. You could also locate the water rudder on the left sidewall but it has to be located in the right place so it does not interfere with the flap handle. My flap handle has been relocated to the outside so this is an issue that will be a little different between a stock factory cub and a Javron Cub. I think Jay is moving all flap handles outboard unless you tell him otherwise.

I opted to go with the stock 18 gallon tanks to keep the weight down, but I know there will likely (10% Vs 90% rule) be times when I want and need more fuel. So I have gone the pod route. This keeps the weight down low and helps prevent noseovers. One of the serious downsides to having 60 or 70 plus gallons of fuel in the wings is that all that weight wants to rotate around your axle, thus going forward and down, when you brake. I know of several extended fuel tank Smith Cubs that have been stood on their nose and I have no doubt that was a contributing factor. So if you go that route, or buy a SC with lots of fuel in the wings, be careful. Since I know I am going to have a pod I have elected to install a permanent mounting rather than the clamp system commonly used by most pod owners. This will allow easy install/uninstall and also have no slits in the fabric and no tabs hanging off the longerons when the pod is not being used. In a nutshell I made a saddle from the next size larger tubing (.058 x 1) that will be welded on, then the longeron will be bushed, then a nut welded on. Total weight for all this permanent addition to the fuselage is 1.95 oz. This will allow an eye bolt to be screwed in when the pod is being used, and just a small screw to close the hole when the pod is not in use. ( For you that are concerned about an eye bolt and its strength, fear not. A bolt in shear is weaker (about 60% of the bolt tensile strength) than one in tension so the weak link will still be the bolt that holds the strap on, and that seems to work fine, I've not heard of any pods falling off.)
So the saddle looks like this..........


On the longeron it looks like this..........


In place and ready for welding.....


The rear edge of the engine door cowl will look better to the eye if it is exactly parallel to the firewall. In order for this line to "Look" straight it will need to be cut with a curve, due to the bow in the shape. Just something to consider for aesthetics.


Hope this helps
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...Hi Bill, a couple of things come to mind.

1. is that a removable front panel for your upper baggage? ...or is it permanent fabric stretched across there? ...point is......I know if I bought your airplane someday that I would need to remove that to load some types of items.

I like the idea too. It reminded me of a raft paddle I spotted from the air a few years ago and stopped and picked up. It would have been a little long into the front seat area if I hadn't had an extended baggage to poke it into.

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Bill you're coming along very nicely. Wendy and I like to tease a little as we're having fun with the Cubs but next year we'll all have fun. Windy and Terry and Chunky Monkey left this morning for Idaho. I think the idea of a hot shower, laundry and a soft bed had some appeal.


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Get one of these cool little tools. It will make it much faster to set up your rivet spacing and to keep them all lined up. A crooked line of rivets looks really bad. This is well worth the investment.


It will make your rivets look like this.........so easy even I can do it.........


In the last post I was getting ready to do some welding. Well, the truth is I hired a young man that is way more talented than I am. I can weld but I am out of practice and it just is not worth it to get all practiced up to do 30 minutes of welding. So Nick came over.........


He welded up the four attach points for the pod, the window channel (from taking the post out of the left side window), nuts on top of the 2 flap pulley attachment points (fabric headliner will make it tough to access this), and a bracket for the water rudder cable where it comes into the fuselage.

Today I painted. I really don't enjoy painting. Just part of the job. The PPG DP48LF white epoxy primer is a dead match for the white Javron uses when powdercoating. Then I used another 2 part paint from PPG "Shop Line JAU acrylic urethane Galaxy White 91694" to topcoat it all with.

Painting with an airbrush........

Cargo pod mounting point........

Window channel.........

Plate for attaching a pulley for the water rudder cable........

All these things could be done by Javron as part of your kit if you wanted. They are not standard items so you would have to specifically ask for them. I missed a couple of things.....

Hope this helps

Back to the cowling

This is what the screws holding the bottom to the rail will look like......


Do not (really,.... you do not want to do this) put the camlocks in for the cowl doors yet. You will have these things on and off a zillion times fitting, checking, working on the rest of the cowl etc. Once you do the camlock thing you can't use a cleco and that would be a real pain. When you are really sure you are done with everything firewall forward and just prior to paint then take your #40 hole (that is now a little wallowed out from having a cleco in and out a few hundred times) and drill it for the camlock. It will look like this for a while, (note I am still working on the door).......


Hope this helps

Received both a square and a round filter airbox from Javron today. Jay was nice and sent one of each so I could play with them a little and decide which would work best.
First impression was.....wow, they are really nice.



Then I just had to weigh them. :lol: This was with all filters and other associated parts like the dome, or the Bracket housing etc. I tried to keep it as close to apples to apples as possible. The square assembly weighs 32.07oz and the Round unit came in at 47.36oz. Pretty close to a pound heavier. Ouch.

Now the tough part. The 0-360 carb is a lot bigger than an 0-320 carb (and 2 pounds heavier), mostly in how far it hangs below the engine. Couple that with dropping the engine mount 2 inches and it hangs pretty far below the cowling line. Dropping the engine mount 2 inches does not drop the carb (relative to the cowling) 2 inches. Think of it as a parallelogram. We dropped the front 2 inches, but not the back, so the middle only gets dropped about an inch. But it all comes out looking like this.....


Here the top edge of the yardstick shows how it would look if we lowered the back by 2 inches as well....


In a stock Cub like this one the back of the tunnel is almost flush with the bottom of the cowl........


Now a quick look at other 0-360 engine Cubs and you will note the tunnel that houses the airbox/filter hangs well below the cowl...


Another example. Note the back of the tunnel is 3 or 4 inches below the bottom of the cowl......


Note this one, DW curved the back edge a little and it softened the lines nicely.....


Square box on mine...........


Bottom line (pardon the pun) is I just don't think I could make the square box look good at all. It would take a huge angular box and look ugly in my opinion. So a tunnel it will be. I will shape the back end like DW to help the looks. Mine with the round box....


And a little quick cardboard (before I shaped the back end)....


Another angle...


So the bottom line for all this is for others who are building, if you are using an 0-360 you will probably want to use the round air filter. If using an 0-320 and not lowering the engine you have the option of square filter (lighter) or round filter. Just my opinion folks. Take it with a salt lick.

Hope it helps

I realize that this is only a cardboard mock up. You might consider adding a cowl flap behind the tunnel just ahead of the bottom cowl opening. It serves two purposes. One is that it helps the visual effect of the big round scoop by making it look a bit smaller. The other and best reason is that it helps suck the hot air out from under the engine. I can't say by how much except that I do not have any high temperatures on my Cub. The flap generates a low pressure area which draws the air out.
I agree with Peter. I have just remade my bottom cowl with that sort of flap. Also I belied out the rear of the lower cowl so it did not follow the line of the boot cowl. The scoop now blends in alot better, the air gets sucked out better and you won't believe this but I picked up 4 knots of air speed. I'm not even going to try and work that one out. But it is true.
The plan shape of my lower cowl ended up having parallel sides. I suppose it works like the side cheeks in the cowl doors.
Peter, that is a great post! Wish I had to like button to add to it !!! (Steve? :D) There is blog option, I add that to my notes.

Bill, your level of detail and willings to share is unparalleled in the aviation community! THANK YOU!!
I realize that this is only a cardboard mock up. You might consider adding a cowl flap behind the tunnel just ahead of the bottom cowl opening. It serves two purposes. One is that it helps the visual effect of the big round scoop by making it look a bit smaller. The other and best reason is that it helps suck the hot air out from under the engine. I can't say by how much except that I do not have any high temperatures on my Cub. The flap generates a low pressure area which draws the air out.
like coyote uglys orange cub on the home page?
FYI, for anyone wanting a pre-made fiberglass "cowl flap".....(more commonly termed exit-"Lip" around here), There is one available that is often added to certified SuperCub's.

It has been years since I purchased one, but the usual suspects are a likely source (Stoddards 907-272-2327 ReeveAirmotive 907-2728522)
Dave just finished my mold to build carbon ones of course!!! With this weather want to get it on and see what it does.
Cool. I thought it was called a "seaplane lip", Since overheating can be an issue when plow taxiing. Yes, I will have one. Thanks for the inputs gents.

Probably still gathering dust in a friend's hangar.
Don't think I saw it SB. Not needed for 53M though IMHO. I had one from Charlies rear oil cooler STC adaptation on 79H and it did drop CHT and Oil temps. If I was experimental like Bill, I would consider having a fixed or controllable bottom cowl lip (flap). The other thread about O-375 high temperature problems, and the variance of different planes, may be in large part to the ability of the cowling system to create the downpressure through the baffling. The bottom cowl scoop is an important part of that equation. When you have the ability to control the downpressure differential like you can with a cowl flap cowling system (like Cessna 180/185), you would be able to dial in the CHT temps and oil temps would follow. Add a controllable cover on the oil cooler and you could be the mad scientist to dial it all. Talking probably less than a pound of total weight with the cables being the heaviest part.

You can see the Charlie Center lip in this photo.

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Operable cowl flaps. Look at a Carbon Cub. Controlled, efficient airflow. That's the model the experimental guys should consider.

My cooling lip never left Birchwood. I never cared for the appearance so I wasn't motivated to add it.