Building a 4 Seat (4S) Javron Cub

Just for point of reference the Airframes 4 place is 42-1/8" wide at the instrument panel/upper longeron. The floor and top deck are 40-1/2". The upper longeron level is brought out slightly to that 42-1/8" size for a little more elbow room.

Crash said:

Just for point of reference the Airframes 4 place is 42-1/8" wide at the instrument panel/upper longeron. The floor and top deck are 40-1/2". The upper longeron level is brought out slightly to that 42-1/8" size for a little more elbow room.

Click to expand...

Thanks Crash. I guess I thought it would be a little wider than that, so the 39" width on the 2+2 plans maybe isn't so bad.

TB

From Javron:
44” inside width.
Top longerons all the way back with no gingerbread for a huge baggage area.
24” x 25” baggage door on left side.
Folding and removable rear seats.
Uses stock Cub wing, lift struts, shock struts, tail surfaces, gear legs, and front seats.
20” longer than stock fuse to increase the CG envelope.
Single center stick with dual option.
Hanging rudder pedals on both sides with toe brakes on left side is standard.
Overhead flap lever on left side.
HD extruded aluminum lift strut package.
Dual throttles with linkage and cables.
Enlarge round tail.
Composite nose bowl with aluminum cowl panels. We are trying to develop a composite cowling package if time permits.
Sheet metal boot cowl with titanium firewall.
Electric trim.
Routed carbon fiber floor boards.
Tested to 2500 lbs. wings to 2300 Lbs.
Shooting for 1230 empty.
90” flaps and 102”ailerons.
Extended square tip wing with 90” flap length.
24 Gal. fuel tanks.
Clear or tinted windshield and all side glass.
Dual doors; split or one piece swing up.
Conical engine mount with zero thrust angle.
Acme Gen 3 main gear shocks.
Grove 6” wheel and double puck brake package.
3200 tail wheel
Ballast brackets in tail.

Tom

Wow...a 20" extension in length is quite significant! The 2+2 I want to build won't be used for anything other than pleasure flying, so there won't be that sort of requirement (wife just wants to sit up front, mainly), but I know that Jay has put a lot of time and energy into developing this airframe. I saw one being built when I was over there a few years ago, but I don't remember the year. It was in its early stages though--I'm not even sure welding was completed yet.

Can't wait to follow the progress of this project!

Folks. EDIT TO ADD.....THIS COMPANY IS NOT AN OPTION NOW, BANKRUPTCY AND REORGANIZATION. MAYBE AT SOME POINT IN THE FUTURE

Thanks for updating and correcting my width numbers.

Tom - Thanks for posting that. It may change as we work out the details on this build, but it is a starting point.

I have ordered the material for the floor boards. This is the same composite I used on my Cub. It has held up quite well in a pretty harsh environment. It is the lightest I can find. Allow me to pontificate a moment if you will. Just because someone says a part is "carbon fiber" that does not necessarily mean it is lighter, or better. The weight of parts made with a resin is highly dependent upon the quantity of resin. If there is too much resin the part will be heavy, and quite possibly heavier than an equivalent part made from aluminum. If there is too little resin it may suffer in strength properties. Vacuum bagging can certainly help but even that is no guarantee. So.......I am always skeptical when someone brags about all the Carbon fiber they have. I recently saw a post where someone was quite proud of the CF storage box they made. Their posted weight was more than an AL box and considerably heavier than the box I got from Carbon Concepts (Randy Appling). Just please keep in mind the CF is not automatically better. There are applications where it is great and there are many applications where it is not good at all. Titanium is another often touted "improvement" that may not always be better. It is more brittle that steel and may break rather than bend. Sometimes a bent part will still get you home but a broken part will result in catastrophic failure. It is great to have the freedom to experiment but please do so with your eyes open. And if you folks out there (many of whom are far more experienced and smarter than I) see me do something dumb, please call me on it.

So back to the floorboards........

Part of the reason I like this material is the quality. It is a manufactured flat panel that has very strict quality control so it is going to be very consistent on the weight. Unlike custom parts that could easily vary considerably in both weight and quality.

There are three different flat panels that I used on my last cub.

ATR-FP-121F1 - this is 1/8" thick honeycomb panel and weighs .24 pounds per sq ft. I used this on my upper baggage floor

ATR-FP-251F1 - this is 1/4" thick single ply honeycomb panel, weighs .27 pds sq ft - I used it for floorboards and baggage floor

ATR-FP-251F2 - this is a two ply and very strong 1/4" panel, weighs .53 pds sq ft - I used for seat bottoms and front floor boards

We will be using ATR-FP-251F1 almost exclusively on the 4S (I think).

Right now the price for a 4'x8' panel is 462.00 It is going to take 2 sheets for this build. The strength necessary depends on the span encountered. There are places where there are lots of underlying support so the material does not have to be as strong and there may be other applications where an unsupported span is greater and that would necessitate greater strength and perhaps use of the heavier two ply material. We will see as we go and post the results here. You can order direct, but it seems like they prefer a purchase order so you might need to get a friend with a business license to make the order for you. It is also possible that Javron will be able to supply it, and he may also be able to cut it for you....thus supplying your floorboards. I don't know about that part. But you could always ask Jay (Javron) about that option/possibility. He has the floorboard patterns in CAD and the capability to cut pretty much any material you want, wood, aluminum, CF, etc.

The company used to be AAR but recently did a name change to Aeromatrix Composites

their website.......https://aeromatrixcomposites.com

The person I spoke to and dealt with is Barbra. She can be reached at 727-533-3201 (Clearwater Florida)

I was able to download the tech spec sheets from the old website but do not see them on the new site. Here are pictures of the Tech sheets









Hope this helps

Bill

Thoughts on carbon fiber part weights. Yes, CF weights can vary with resin %. Even vacuum bagging it can vary depending on how much vacuum is applied at what point in the process. However, directly comparing one persons part to another when not privy to designed differences can be misleading. Carbon concepts standard width cub under seat storage box is light. Nice box but I wouldn’t mount a battery in it. When I built the box for my wide body cub it was going to be heavier simply because it’s 4” wider. I wanted to be able to mount my battery in the box so added two layers of CF to get the structural integrity I desired. Same with floorboards. A friend bought honeycomb core CF for floorboards. One layer of CF on each side of the honeycomb. Light stuff but dents easily. Don’t take your girlfriend for a ride if she’s wearing 4” heals. I doubled up on the CF when I built my floor. Heavier, yes, but like gluing fabric to your aluminum interior panels, there are reasons to do it, or not. I built an aluminum throttle tunnel. Then I built a CF tunnel. CF was lighter by about 2 oz. In my opinion the weight difference was not worth the significant cost differential. From an esthetic perspective it was well worth it. So, when comparing CF parts ask questions, get a sample, beat on it, drop seatbelt buckles on it, then buy or build what suits your mission.

Excellent post Ed. Well said!

Yes, so important to build to your mission.

Thanks

Bill

Yeah, you can go nuts on this stuff. Most of my buddies know that the stuff I build has so much iron in it that it will swing a compass needle from 100 yards. I compensate by filling the tubing with helium. Gonna call this thing the Zeppelin cub.

A local pilot completed a 4-place Bearhawk last fall and he used .060" Kydex for the floor boards. I was surprised they were as rigid as they were and seemed like they would be suitable. I don't know how much structure was under them but it was enough.

Here's some weight comparisons I found for aluminum and Kydex T:

Aluminum:
.020” .282 pounds per sq ft
.025” .352 “


Kydex T;
.028” .197 pounds per sq ft
.040” .281 “
.060” .421 “

I recently purchased several sheets of .040" T from Curbell Plastics. A 4x8 sheet was just over $100. .040" works well for interior panels but I wouldn't consider it for floorboards. And .040" with color is the same weight as bare .020" aluminum......

Kydex T is an aviation grade Kydex that has been through burn certs.

BTW, the Bearhawk was topcoated by Hardtailjohn with Stewarts and it is a beautiful plane.

"We will be using ATR-FP-251F1 almost exclusively on the 4S (I think)."

For front floorboards too?

Sent from my SM-G965U1 using SuperCub.Org mobile app

Kydex .pdf weight chart

Seat weights:

I am thinking of going with two Cessna seats on a Cessna track. The weight difference seems to be minor from my weight notes. But if someone reading this knows better, please comment. A front articulating seat from my Cessna with Airtex cushions weighs 13.5 pounds. I'm not sure what tracks weigh, perhaps two pounds per side? I looked at the old W&B from my former PA-18 and have the front seat weight at 12.5 pounds with cushions (I think they were Cub Crafters cushions). But I don't think this Cub seat weight includes the base. Perhaps someone can correct me on this? I no longer own the Cub.

The nice thing about Cessna seats is they easily slide back and forth, are made as a folder, and slide off of the track very easily if not needed or wanted. And they're comfortable IMO.

Dan - Thank you for posting the information about Kydex, and also the idea of the Cessna seats. I think there is a lot of merit to that. You would probably want Jay to weld in some tabs to attach the rails to, so that you would have a more secure system rather than simply bolting the rails to the floorboard. But I’m sure you already know that and thought of it.

DJ - Yes, think that right now. You really don't "stand" on the front floor. At least in a cub, so not as much weight is concentrated in a small area. I used the 2ply on the front floor of my current cub and I am thinking it was probably over kill. We will try the single ply and if I don't like it, we can change to the two ply. But my gut feeling is it will be fine. But as someone pointed out, the single ply might "dent" easier, ie a rock stuck to the bottom of a boot, or a dropped tool like an ax, hammer, etc. It is all a trade off.

Getting started on the paint booth. Man materials are expensive right now. Painfully so. But it’s the price I pay for my own quirks and personality flaws. I just don’t like a plastic/visqueen booth. As I said before, it takes the very best for me to get an average job. And I will probably use it for several projects, and perhaps to help my neighbors a little bit. I’m not much of a painter but if I can help a neighbor, fellow builder, I will try.

One thing I noticed about single ply CF with a honeycomb core is that you can see light through it…i.e. liquid passes through it/into it, at least the stuff I used for seat bottoms & backs. Something to consider, especially if you’re going to be on floats.

Mr. Ed said:

One thing I noticed about single ply CF with a honeycomb core is that you can see light through it…i.e. liquid passes through it/into it, at least the stuff I used for seat bottoms & backs. Something to consider, especially if you’re going to be on floats.

Click to expand...

That depends on what fabric was used in the layup, Not all weaves are that way, and if the fabric is wetted out properly it will be air tight.

Folks

A quick update

Brad spoke at length to Stein Bruch of SteinAir. https://www.steinair.com If you are not familiar with this name you should be. They are one of the premier avionics shops for homebuilders. They do a LOT of avionics sales and custom panels for experimental types especially the Vans RV group. They have helped several Javron Cub guys. They are in the Minneapolis area and are knowledgeable of Javron Cubs. At any rate, they will be doing Brads panel. Going with the G3X system. Brad sent a deposit to get in the que. We are expecting a Sept or Oct time frame. Everyone is backed up right now so to keep the project moving forward we have to order stuff in advance to account for the lead times.


This is the panel they did for Mark Fiedlers Cub.

Brad has also decided to have Jay DeRosier build the engine with the help of Lycon. 0-370 with all the bells and whistles at 9-1 compression ratio. We expect to be a little over 200Hp with a weight about 270 pounds. More to follow on both the above decisions.

Hope this helps

Bill

I have know Stein for years, he is well respected in the RV community. I sent him a blank panel, and he cut it out, covered it with a carbon fiber overlay, and silkscreened it. I also purchased the avionics from him. I did the wiring myself, but he will do that too. I was very happy with his service, but there are lead times.

Sorry about the tilted picture, I was getting bounced around.

John

Bill,

Any updates on the project? I’m interested to see how the plane is coming together.

Joe

Bill,

I occasionally make trips to Sandpoint to visit a buddy and would love to stop in to see your project. I too will be ordering a 4 place cub in the very near future, however I still haven't decided between Airframes Alaska or Javron. I think seeing your project and getting a closer look will help make the decision that much easier.

Cheers!

Despite manufacturing, shipping, global material shortage and inflation issues. If Jay can keep costs relatively moderated I think the decision becomes quite clear. The Airframes fuse was ballpark $21,000. It is now $32,000. To be fair, I do not know of Javron's price adjustments if any.

Gents (and Ladies)

I am really sorry that I have not updated recently. I do have a fair amount of progress to report just as soon as I have 20 seconds to myself. Been super ultra busy. I have spent the last couple of days in the shop with Jay DeRosier working on some design issues which I will talk about when I have a moment.


tgatherer- I would love to have a visit. shoot me a PM with your contact info and I will respond.

Standby for updates in the next few days

Bill

I am looking forward to this thread. If things go according to plan, I will be on the list for one myself.

Bill,
Looking forward to this as a first time builder. My kit is done and I got my first look at Jays finished product at Oshkosh. I'll be spending a couple weeks with Jay over the next couple months. Then it will be shipped to Ohio for me to finish. I'll be following your build closely. Thanks.

Herman

Herman,
Welcome to the Javron 4 seater family!
I should get my kit late September, early October.

Bill,
Very interested in the design changes you and Jay discussed.
Tom

Folks

Wow, time seems to just fly by. Pardon the pun, (groan) but it has been a very busy summer.

I spent 50 days in Alaska. Stayed in the cabins 34 nights. Stayed in 19 different cabins. Logged 94 flight hours. Had two new visitors and 5 friends total in the cabins.​

Three cubs, 2 are Javron, one a CC top Cub. On floats in Alaska at a Forest Service Cabin. It was a fun summer.

​

Here is a video of 3 cubs in Alaska. I will try to do a couple of more videos when I have time. I got a lot of footage this year, just need to edit and put it together. Time.....just not enough time....​

Then I flew to Oshkosh, then the upper Peninsula of Michigan, then to Brainerd to work on the 4S fuselage, and had to work in there as well. Then in a few days I will head to the Greenville fly-in in Maine, and finally get my Cub back to Sandpoint in the latter part of September.


As I look back on my other thread I have no idea how I found the time to do all that. I have been going in full afterburner since about the first of April.

So......enough of my issues......lets talk cubs..

There is sooo much info on "how to cover" on Youtube that I will not go over that here. We are using Airtech and there are TONS of videos at the Airtech channel.

The tail surfaces, flaps and ailerons are covered, stitched, taped, and ready for primer. Working on getting the wings ready for cover now. I anticipate Brad can start covering one of the wings this evening.
Although the wings are pretty much built there is still a fair amount of work that must be done prior to cover.

1) Install position/strobe light mounts. We fabricated ours. You can find info on how we did this in my other thread. (You can also order premade mounts from Jay, saves time and they are beautiful)
2) install the wires for the pos/strobe lights
3) install Landing Lights (often shortened to just LL)
4) run the wires for the LL
5) install pitot tube
6) run pitot tube lines
7) install magnetometer (if doing electronic flight display)
8 ) run magnetometer wire
9) put in flap bellcrank access cover
10) cover the wing tip LE fairing
11) install aileron servo
12) install aileron cable and tie it off
13) Install the pocket pieces at the strut attach points

Last Pre-Cover checklist

1) Check every inch for sharp edges
2) Use an air nozzle to clean out all drill chips and other debries
3) Clean any and all ink off - it WILL bleed through
4) Safety wire the tank bay rib
5) Don't drill the landing light trim piece until after cover and paint



there may be others....if you guys see something I am missing please let me know. I will get a little breakfast and elaborate on the above some.

Hope this helps

Bill

And a little 15 second teaser video. This is Mark's recently completed Javron Cub on Wip 2100A floats on a lake in Alaska that you can only get to by floatplane.

​

Folks

Lets talk about the above list one by one.

1) Wingtip light mounts......you can order some from Javron or build your own. Here is a link to my other thread on how I built my own mounts.
https://www.supercub.org/forum/show...g-a-Javron-Cub&p=598590&viewfull=1#post598590
I like to use the Aveo Ultra Daylight lights, but the Javron wingtip mount fits the Powerburst NXT light which is a different shape. Soooo.....
if you order the mount from Javron make sure you buy the right light. I think you can get both from Javron and thus ensure they are matched.

2) Wires - you can run the wires for the wingtip lights shielded or not. I (and others) have used non shielded and had no problems. Shielded is heavier, but it does bundle nice. Also you will need 4 wires if you want to make all your strobes go off at the same time. I have not been able to find ANY data that indicates that synchronized strobes enhance visibility. My own personal observation makes me believe the unsynchronized strobes are more visible. So I just run three wires. Saves weight too.

I like to use these grommets from McMaster Carr for wires, pitot lines etc. They are super light and easy to install. They come in several sizes.
The part number is 5269T12 or 5269T14 so you can look them up. Pretty simple. Drill the hole with a step drill, clean up the edges, and snap the grommet in.3) Landing lights - We looked at a number of options and companies and felt like the Baha Designs Squadron Pro was still the best option.

https://www.bajadesigns.com/products/squadron-pro-black-flush-mount-led-auxiliary-light-pod/

There are brighter lights out there but you also need to look at the amp draw. I do not want to have to put a 60 amp alternator on the front of the engine just to drive the lights. Also, some of the newer high intensity lights will auto reduce as they heat up. The companies don't like to admit this, but it happens and is an issue. You pay for a 60,000 lumen light but you may only be getting 30,000 lumen most of the time. Just a heads up for you to research and consider.

Brad did a little science experiment to see how large the LL lens needed to be. The lens Jay sells is about 17 inches wide. But the angle the light comes out at does not require this wide an opening. So we were able to cut down the size and width of the LL cavity and lens thus saving weight. Our lens is now about 10" wide.




A die grinder and a cut off wheel will work great for cutting the LE out. Go slow. and remember to drill a hole at each corner and cut into the hole.



You can see the corner holes here. Square corners crack so you want to have a nice radius on each corner.


The finished cut out.




The Squadron Pro light


Showing the size of the cut out



Then we will rivet in the channels that hold the lens in place. This is all pretty thin material so you will be dimpling the holes and using flush rivets.
When you are done the lens should lay in pretty close to flush with the leading edge. It is not proud of the LE, and it does not sit "on" the LE.
After you trim (cut to fit) the lens be sure to sand the edges nice and smooth to reduce stress risers and prevent cracking. Get rid of all your "tool marks".



Next we need to put in nut plates to hold the trip piece that covers the lens edges. You can see some just laying on top as we talk about where to locate them. You need about 4 across the top and bottom edges and three along the sides.



Here you can see the trim piece and the screw locations.



With the landing light installed. You will have to make a mount for the light. Use a piece of .025 and bend a couple of edges to make it stiffer (or you can rivet a 90* piece to make it stiffer, you can see my rivets in the photo) then cut it out so there is a tab on each corner, then pop rivet those tabs to the ribs on either side of the LL bay. If you look closely you can see the clecos where the tabs are going to be riveted to the ribs.

Lots of ways to do all this, but this is just one idea. I think Javron also sells a light install kit but I think it is heavier than this method.

Hope this helps

Bill

thaefeli said:

Herman,
Welcome to the Javron 4 seater family!
I should get my kit late September, early October.

Bill,
Very interested in the design changes you and Jay discussed.
Tom

Click to expand...

I'll be getting mine shorty after yours. I'd love to chat and get progress updates as you move along.

I edited and added to the post above




4) Install landing light wires. Pretty straight forward. Two wires....red and black. 18 gauge will be fine for LED lights. I prefer to run these through separate grommets than the wingtip wires. Makes it easier if you have to replace a wire. When you get to the tank bay you may want to run the wires in a plastic tube/sleeve and I use the screws holding the LE on to hold a couple of clips (made from .020) to hold the wires in place. It may also help to separate the magnetometer and other wires as much as possible. In this photo you can see the magnetometer bundle (black sleeved wire) running at the top of the spar cap and the other wires, and pitot lines, at the bottom of the cap (wing is upside down). Eventually they all run together down the door post so you can't separate them all the way, but as much as possible.....





We will add some more holders to keep the wires in place.


5) Install pitot tube
You have a couple of options. The lightest and simplest is to have Jay weld a tube into the jury strut. Light and simple. This is what I did.
But if you are going with a glass set up and you want AOA info you may have to run two lines and install the fancy Garmin pitot tube. The advantage is "AOA is EVERYTHING" and that is how an airplane flies. So having an AOA indicator can be very helpful. The Garmin install manual has instructions on where to mount the pitot tube. You may also want to heat it if you seriously.... PLAN..... to fly IFR. It does add a pound or so more weight if you want the AOA function.

I am assisting/mentoring Brad with his build. This is HIS airplane built to HIS mission. He wanted AOA. Thus we are doing the AOA pitot probe.
Build YOUR perfect airplane to fit your mission.



Brad riveted the mount to the rib just outside the jury strut, and screwed it to the spar cap.




bend the edges down for extra strength.



6) Run the pitot lines. I don't have a picture for this but I will try to describe it. With the Garmin mount you will attach the pitot lines after covering and paint, so they will be sticking out during the covering and painting part. Once attached the lines will need to be pulled into the wing. I recommend you test this before cover and determine how far to pull these lines in (from the wing root) and then mark the line. If you pull it too hard or too far you could kink the lines. So by marking the line you will know just how far to pull it to get a nice curve in the line without getting a kink in it.

7) Install the magnetometer.
If you are going glass you will need to mount the mag before covering the wing. Garmin has a mount but Jay also set one up in CAD and it fits very nice. This will be mounted into the spar web. I DO NOT like drilling into the spar web and recommend you do it as little as possible. But if you must be sure the holes you make are round and clean. A drill bit does not make a round or clean hole. Drill undersize and ream up. Now you have a round hole. Smooth the edges as much as possible to reduce stress risers. Pop rivet it in.

8 ) Run the magnetometer wires

We got this wire bundle remade from Stein with the ends already set up. The downside is you can't feed it through a small hole. So, Brad made tabs with a slit, then riveted those to the ribs. Then installed the grommets. Looks like this. Pretty clever way to do it.


You can see the slit in the tab. This allows you to slip the wire in rather than feed it in. You can also see the little triangle tab riveted in.



9) Flap Bellcrank access cover
You can install the standard rectangular access reinforcement and cover per Piper drawings, that is what I did on my Cub, or you can make it a little larger by just putting some nut plates in the ribs. Larger is better and adds little if any weight. I like better as long as it does not add weight.


You will have to make a little C shaped piece from .020 or .025 and screw it to the spar cap (use existing screws) to get a level point for the front of the access cover plate. Install some nut plates and poof you are done. Don't forget to clean the ink off that little C shape you screwed in otherwise the ink will bleed through the fabric when you cover and make a mess.

10) Optional......,Install wingtip fairings to smooth out the covering.
The wingtips on a square tip wing can be covered as is but the fabric will have some pretty sharp sags and perhaps even a wrinkle. If you want to make it a little nicer you can install some little fairings to make the fabric hold its shape a little better. These are made from .016 material and pop riveted in place. You will not be able to bend the entire edge down because it is going to assume close to a compound curve shape so just cut and leave little tabs (reference the wingtip light mounts we fabricated) if you are struggling to visualize what I am trying to say.



This is a bottom fairing. You can do a top as well but the bottom is the more critical of the two.

I am finding it much more difficult to do as "How to" thread when I am not actually doing the work. Arggggggg

More to follow

11) Install Aileron Autopilot servo
Part of Brads mission involves a fair amount of cross country flying. In that respect an auto pilot can be quite helpful. The way we have configured the fuselage of his 4S there is not an easy place to install the aileron servo in the fuselage or directly to the torque tube as in some other applications. Soooo......we have installed it in the wing. I don't have a picture of the servo install but Brad sent me this little video. Brad made a mount plate that attaches to the upper and lower spar caps and does not attach to the spar web.



Hope this helps

Bill