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Building a Javron Cub

Grounding Carbon Fiber Tanks- This should probably be a subject itself. Can it be done? Does it need to be done? When i built my cub i made a little effort to make sure that the tank was connected all the way to where i put the fuel pump ground strap on. Watch guys fuel up and some use the ground cable, most dont. Now with carbon what happens there? When the tank felts or rubber cushions are put on the straps this seperates the tank from the frame dosent it. So isnt a ground strap from the pump on alot of these planes a waste of time? Most fueling hoses have a ground wire in them but some cases they dont. Sorry for the creep here. I dont believe stock cub tanks use anything either. doug
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Jose - actually we just put a smaller orifice in the sight gauge to minimize the fluctuations in the sight glass relative to the fuel sloshing in the tank.
Pete - excellent inputs but actually the extra bung is for........


I elected to try something on this build that is not very common in the SC community but is pretty common elsewhere. I purchased an electronic fuel sending gauge that will send an electronic quantity signal to my Grand Rapids Flight Display. That is a fancy way of saying I'm going to have both a manual fuel gauge (the standard fuel sight gauge in the wing route) and also an electronic gauge in my flight display. The software is already built into the Dynon, GRT, Advanced, and Garmin displays but you have to give them a signal input. That is what this thing does. There is a wire in the aluminum tube and it measures the resistance between the wire and the tube. It then sends that value (which you calibrate) to your instrument display. If you add the Fuel Flow sending unit in the fuel line you get all kinds of useful info. Like how much fuel will I use between X and Y and what will I have when I get to Z. I think it will also be more accurate at the lower readings.

WHY? You are asking yourself, about now, what the heck do you need that for? Bottom line - you don't. Sight gauges are simple, darn near fool proof, and have worked just fine for the last 80 years or so. But....lets consider this a little more. The two most common ways to kill yourself in a airplane are......
1) flying VFR into IFR conditions - so I have a flight display that gives me attitude and enough info that I can stay upright and not go spinning into the ground if I accidentally go IFR
2) running out of gas - so I will maximize my fuel inputs, use both on the fuel selector, not turn my selector off between flights, and try to make fuel awareness a high priority

This does not mean that I plan to press my fuel or that I will never do anything dumb (again) but I do think it is important to learn from others and then concentrate your energy where it is most likely to generate results. Fuel starvation is a common reason for a mishap. Yes, you can say that stupidity is a common reason for fuel starvation, and that if you run one out of gas, well....you're just stupid. Hard to argue that logic, but buried in that logic is..."I'm not stupid so it will never happen to me." I'm sure all the folks that ran one out of gas thought they were smarter than that, just like you, and I'll bet everyone of them thought "how could I be so stupid?" after they did it. I'll be the first to admit I make mistakes. So I try to figure out how to minimize that possibility, or how to minimize the consequence of my mistakes. Thus, in this case I am trying to maximize my fuel quantity knowledge and awareness.


This is what the probe looks like. Compression fitting where it goes in that tank bung. The black electronic box will screw to the wing root rib. It is quite light. Both probes and boxes, wires,etc weigh about 8.2 ounces.


This is where I got it. You can also get it from AC spruce, and perhaps others.


Compression fitting and extra tank bung welded on by Javron.


This is how the tube will position in the tanks. I will make a 90 degree bend in the tube and then feed it into the tanks so that it angles back to sit near the rear fuel pick up. It does not have to be vertical as you calibrate it like you do with the sight gauges, ie put in 4.5 gallons and mark that 1/4, 9 gallons and mark 1/2 etc.

FOLKS - This did not work out. Due to the flat nature of the tank the probes were not accurate. It would work on a J-3 type tank as it is much deeper allowing for a longer probe. My probe had to be cut down to about 6 inches even at an angle. Neat idea but it did not work. I do not recommend these for this application. The Princeton system seems to be excellent but not for a flat tank like in the Supercub.

Just my opinion, hope it helps

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I like the gauges, are you going to calibrate them with the tail down in taxi position or up in flight attitude?

i am intrigued by the idea of placing the signal tube at such an angle. It would seem that a pickup tube mounted vertically would give the most accurate readings when fuel sloshes fore and aft while climbing or descending. By placing at an angle towards the rear, the same degree of fuel slosh would show more fuel on the gauge when climbing and less fuel when descending. The descrepancy between readings from a vertical tube compared to an angled tube would become more pronounced as the fuel drops below a half tank, which is when it needs to be most accurate.

Also the closer to the center point of the tank the less significant will be the affects of slosh

Finally I wonder if the unit has a dampening circuit to reduce needle bounce.

i have a pair of the same type of capacitance fuel level gauges on a car I built and they work very well. But when accelerating or braking the gauges fluctuate significantly even though the system has some electronic dampening. Unfortunately the tanks are long and the sensor is located at the aft end. If they could have been placed in the longitudinal center point the affects of slosh would have been less.

Another trick is to place the pickup tube within another tube that has small openings so the fuel drains and fills the chamber slowly. The same concept as a pin hole opening for the sight tubes. Not likely an option at this point.

Just some thoughts. I may well be missing something.

I was considering the same thing but was afraid that once I bent the 90 I would not have enough total probe length to reach the aft end of the tank. How long of a probe did you order? I would assume that the 90 will have to be gentle to prevent the core from contacting the outer shell. Can you trim the probes to length?
Chuck - excellent points. If I am not happy with the performance, I guess I could trim the probe and turn it vertical. I'll let everyone know how it works out.

Doug - I got the 18" length but you can get them longer and you can trim them to length.

DRUM ROLL...........


All weights do not include tank, tank lid, flaps, ailerons, lights, covering (other wing weights pulled from posts on this site so I can't be 100% sure of the accuracy)

Buggs66 Square tip wing - 76 (est)
Dakota slotted square tip wing - 89.5
Dakota regular Square tip wing - 83.5
Backcountry Square tip wing - 89.5

Javron Square tip wing w/ CF leading edges - 72.2

I weighed both wings .....left wing 65.6 right wing 65.7 (amazing they were that close, that is literally less than 2 ounces difference)
The Carbon Fiber leading edge material (with none trimmed off prior to installation) weighed 5.52 pounds
Thus the total comparable weight at 72.2 pounds.

The aluminum leading edge will add about 4.8 pounds so figure 77 pounds for a Javron square tip wing.

A stock round tip Piper 13 rib wing in the same configuration weighs 58 to 60 pounds as best I can tell from the posts I have found on this site.
A Dakota round tip wing weighs - 77.15
I could not find an accurate weight for a 16 rib wing.
Marty57 wood wing panel came in at 64 pounds
Jay at Javron says he is pretty confident his round tip wing with aluminum leading edges will be in the 62 pound range. That is pretty darn good folks.

I will post more weights as I go along but at this point I am very pleased with my wing weights.

Hope this helps


(I'm not bashing Dakota - they are great, I just don't have any weights for a Cub Crafters wing, Legend Cub Wing, Univair, etc
If you have any of these weights measured on something more accurate than a bathroom scale - please post them.)

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Those are interesting weight comparisons. I have modified my wing and added a shear plate in the tank bay and removed the diagonal brace. I suspect the weight will be more in the area of 72-74 lbs when finished. That weight does not include the fuel tank straps, tank lid (aluminum) or the control cables. I wonder if some of those heavier weights might include some of the items my wing is missing. The 62 lbs Jay is shooting for, what does that include? Pulleys, cables, tank straps, ???????? Wing weights are difficult I think to compare without knowing what they include. Weights of wings ready to install (flight ready) would be interesting; I'll weight mine before install but thats a long way off for sure. Good info here, thanks. I like your tanks BTW; been following those as I designed mine.


Very nice tanks!! Any idea what thickness they are made from? Also do you know if the ends are flanged and turned inside or just edge welded?
They only fuel gauge I trust is in my truck, I can go 35 miles after the low light goes on, so far. The best aircraft gauge is the wire in a J3 if you calibrate it. The only fuel gauge you should ever really trust goes " tic- toc

Oops ...... missed the first part of the of the wing weight posts. I'll have to see what mine comes in at in that configuration. Amazing how close the different wings weigh.
Bill , if you bend the fuel capacitance sender (90 degrees ) the center tube will touch the outside tube. Do not see how you can bend it and have it work . If you contact princeton , they may be able to do it for you . Maybe ?
Capacitance tube can also be put in ( straight ) and work from the bottom slanted up to top of tank.
That angled probe is indeed intriguing. My first thought was that it's a great idea, for greater sensitivity. Then my second thought was yeah, what about slosh factor; bad idea. Then my third thought was that it sloshes regardless of measuring location (agreed, it's least at the center) so what the heck. And it probably sloshes more on the roll axis than the pitch axis anyway. And my fourth thought is that when fuel is really critical, it's what's at the back of the tank (on average) that really matters so I think that angled arrangement will be real good. And the brain can average out the sloshing pretty well too, while watching the gauge. May I suggest a dual calibration - three point and normal level flight attitudes. If the software won't handle a dual calibration a little placard surely could. Just thinking out loud - - - That's going to be one sweet plane!
Lowrider - I am not sure of the answers regarding the welding on the tanks. I know Jay tried several different ideas, in an effort to find what yielded the strongest welds. Call him and ask. He is super nice, and will share anything. Jay DeRosier at Javron -Phone: 218-829-9320 http://javroninc.com/index.cfm/home

Knuckles - Excellent input. I will contact them. When I ordered them he made it sound like it was no big deal to bend them. I do not know what it looks like inside or how they separate the two (tube and wire).

What will you be setting your wing wash out at or what does Jay set them at when you put the leading edges on. Also Jay was talking at one time about aluminum struts did that ever pan out.

Hope this helps


(I'm not bashing Dakota - they are great, I just don't have any weights for a Cub Crafters wing, Legend Cub Wing, Univair, etc
If you have any of these weights measured on something more accurate than a bathroom scale - please post them.)

I weighed one of my finished Carbon Cub wings prior to putting it on the plane. This is a complete weight including flap and aileron and their larger tanks (22 gallons per side). This was covered with Polyfiber and sprayed with Polytone and Aerothane trim color. It was 76.8 pounds.

The larger tanks add 15 pounds I think, so half of that weight per side over standard tanks. So with regular tanks the weight would be under 70 pounds ready to install.

The 76.8 pound weight also includes the one pound flap actuator rod.
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Looks awesome Bill. I just have one more question (yeah.... right) for you. Do you know if Jay is planning on selling his wings as a kit? Or just pre-built. Just because shipping pn anything so bulky is brutal expensive to get in the Yukon. I was planning on calling him in the next week or two, as withe any luck at all I should be ready for wings this fall.
Dan - That is quite impressive. My wing in the same configuration will be close to, or slightly over, 100 pds. You are 25 pounds lighter per panel. WOW!!!
I don't know how I could take another 25 pounds out. And your tanks are larger than mine 22 Vs 18. Wow....just Wow. If I went round tip, drilled spars, fewer and lighter ribs, etc I might get at the MOST 15 pounds out, but then I would be seriously uncomfortable setting a GW at 2200 or 2300. That is impressive. I did see in the Wing Weight thread that Spinner2 reported regarding his stock cub restoration (not a Carbon Cub)......
This would bring the weight of my finished and rejuvenated right wing to 99.5 pounds complete with all parts including cables, wingtip light and original gas tank & tank cover.
That would put my Javron Sq tip wing(estimated) at about the same as a Std SC round tip wing. Give or take a pound or two.

Buggs66 - if we subtract 12 pounds for your tank that puts you at 76 pounds which is lighter than Jays estimated weight of an aluminum LE sq tip wing. Great job.

Wronghand - Yes. Jay will be doing a kit. He has a backlog of wings to get out right away to folks waiting. As soon as he gets that squared away he will be doing the kit wing. Everything will be pre drilled, spars etc. It should be good. And yes much cheaper to ship a flat box Vs a fully assembled wing.

Jay has been putting in some long hours. He has the steel part of his business pretty well up to speed. In fact, he had a couple of fuselages built up (as far as he can and still accommodate customer changes) so he feels he can ship the weldment components to a kit in about two weeks. Thats pretty cool. That was his goal.
Now he is going after the wing assembly line. He has a part of the shop set aside that he will be putting all his wing building tables, jigs, shelves, etc into and he has hired a full time employee that will be dedicated to building wings. All of the design work is pretty well finalized so I expect to see pretty good progress in this area and I know his goal is to get ahead enough to have a couple of sets of wings in inventory for immediate shipping in the future. It may take him a few months to get through the backlog and accomplish all this but I think it will happen.

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Right on Bill, thanks for the reply. And once again.... Ask him if he needs any welders...LOL, dont think my wife would ever leave theYukon
What will you be setting your wing wash out at or what does Jay set them at when you put the leading edges on. Also Jay was talking at one time about aluminum struts did that ever pan out.

Larry - Jay is still working on the Aluminum struts and he had a major breakthrough this last week. He had some incorrect specifications in his drawings, which he has resolved so I expect to see some progress on that now. It was at a standstill for a while.

Washout - this will normally be built in by Jay when he puts your leading edges on. Since I am doing my own leading edges, I will be setting that in. I read through several threads on this site and HOLY BUCKETS did we manage to make a mountain out of a molehill. I guess it was harder before the advent of the smart level. Now it is an absolute no-brainer.
Put your two saw horses out there. Make sure the tops of the horses are parallel. Easy to do with a smart level. It does not really matter if one horse is higher or lower than the other as long as the tops are level and/or parallel. Now measure the root and zero out the level. Go to the other end and measure that end in the same manner. Block up the rear spar until you get the angle you want. The block of wood does not need to be 3/8" necessarily, and does not have to be under the aileron butt rib. Just do whatever it takes to get the angle you want. Some folks say the angle should be 2.5 degrees, some aver it should be 2 degrees. I seriously doubt 1/2 degree will make a noticeable difference in flight handling. We are not building a rocket ship or going to the moon. Furthermore it can be adjusted with the wing struts; however, it is nice to build it in so that you do not get wrinkles in your fabric, or oil canning of the LE, when you rig it on the fuselage. Some folks in the experimental group have elected to use zero washout. I decided I wanted some but felt I would probably be fine with less than 2.5 degrees. I am going to set about 1/2 of the Piper specs, thus I am looking for about 1.2 degrees, give or take.


Picture of what the Stewart wing tip looks like. This is the standard tip Jay will use on the Sq tip wings. He would probably be happy to mount whatever tip you want. (Might cost a little more.)


Smart level under the root rib. The bottom of the rib has a small curve so this is not the best technique but it is another cross check. Zero out your level.


Out at the wing tip. A little more angle than I wanted. I'll measure from a different place......


You can also use the tops (or bottoms) of the spars. Smart levels are the coolest thing since sliced bread. Zero at the root. see what you get at...........


The other end.


So a couple of cross checks yielded pretty much the same result so I'll use a smaller block of wood.


Block of wood under aft spar near the tip.

Hope this helps

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FWIW, Cub Crafters specifies a 1" spacer, with saw horses 151" apart. Block placed under the rear spar. Distance between the spars will obviously affect the angle and off hand I don't have that dimension. I will measure the degrees when I am next in the shop and let you know the result, just for comparison sake.

Those smart levels are indeed handy.

Started fooling with the CF leading edges today.


Mark and Cal came over. It makes a huge difference when others are willing to help. It pushes me, tough to be lazy when someone else is working harder than you are. They work, then I buy lunch. Heck of a deal for me. About a buck an hour labor. But it is a lot of fun. Thanks guys.


So we fussed around, scratching our heads, trying to figure out how to work the CF stuff. I made a test sample for adhesives. Tried a couple of different two sided tapes and also 5 minute epoxy. I was not all that inpressed. Randy Apling at CarbonConcepts is where I got this LE material and he recommended a 3M brand tape. About 150 dollars a roll. Hi-tec expensive stuff. In my test sample of it I was not impressed. It did not seem like it was much better than your basic two sided carpet tape. Thus lots of head scratching. I called and talked to Randy again. He is very nice and helpful. Excellent product support. He keeps saying the tape will work. Hmmmm, so I tried it. Works awesome!!!! It did not seem all that great when we were just fooling around with it but in the application on the wing, WOW that stuff is amazing. It is NOT coming off. Better get it right the first time.
So now that we have passed the initial learning curve, I think it will go faster. According to Jay at Javron, the use of the CF on the LE and the two wing tank covers will save 12 pounds over the comparable aluminum, total for both wings (6 pds per wing). He weighed out both sets and that is what he came up with. We will see. I will keep weighing as I go.


Figured out the easiest way to cut and trim the CF is with a cut off wheel on the Dremel.


Getting the next piece lined up.

Hope this helps

While I was testing adhesives the 3M tape came out best and easiest to use in my opinion. What I tried was $60 or so which I think is retail. Maybe you have a different tape.

That is a beauitful wing.

Getting the tape on. Clean thoroughly with acetone first.


A section taped and ready. Note - the camera angle makes that first rib spacing look really big, weird.


Probably not the best photo to show my thought but you want to peal back the protective layer just a little and get that section attached, then peal back a little more, exposing the adhesive for the next few inches etc. By doing so you can get it nice and tight.


Attach the bottom edge/lip first, then work up around the rib to the top to the front spar.


I used a 48" level to pull the bottom up. That helps prevent any bulges, sags or oil canning. It did not work going up around the rib but works well getting the bottom lined up. This stuff acts like contact cement. You have to get it right the first time as it is near impossible to separate without destroying the CF.


I overlapped the seams. In order to get a nice straight edge at the overlap, I discovered this worked great. There is enough flex that the foot shear worked without damaging the part.


According to Randy Apling (maker of the CF ) you do not have to put the seams on a rib and he includes the backing parts to create butt joints in between the ribs. I just felt better with making the seams over the ribs with an overlap. This shows a piece after being trimmed to cover 4 rib bays.
It goes all the way up over the spar, it is just positioned here for the photo.


Trial fit using masking tape. You can get everything ready and even attach the back and bottom solo but you REALLY need extra hands to do the wrap. Even a small piece can be a challenge alone. Buy some beer, invite your friends over, beer AFTER the work is done..... :)

Hope this helps

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Alternatively you can use 3M 2216 for bonding Alum to CF. Not sure how price competitive it is to 3M VHB tape...

Wing looks great... to bad it has it has to get all covered up :)

FWIW, Cub Crafters specifies a 1" spacer, with saw horses 151" apart. Block placed under the rear spar. Distance between the spars will obviously affect the angle and off hand I don't have that dimension. I will measure the degrees when I am next in the shop and let you know the result, just for comparison sake.

Those smart levels are indeed handy.


Using your "smart level" technique, Cubcrafters uses 2 degrees of washout at the 12th rib with a one inch spacer block.