Building a Javron Cub

[Nathan K. Hammond]

Bill, great thread and what will become an even better airplane.

What are you going to do about hardware? Things like lock nuts; steel, nylon, NASA, or castle nuts with a pin? Stainless or Cad-plated screws? Nylon or metal washers?

Leo Loudenslager was fanatic about cutting as much weight as possible out of his Lazar and the Shark. When rebuilding the Lazer, he would assemble a part, then hacksaw all but one thread off the end of a bolt or screw. He kept every little piece he cut off in a 5 gallon bucket that probably weighed 15 pounds by the time he was done. Ounces lead to pounds.

nkh

[aktango58]

Today we needed some much needed stress relief...

so the razor knife came out and fabric started falling off my old girl. We now have one big inspection hole in the side.

As we look into the plane right now, there is a very noticeable couple of spots where dissimilar metal corrosion is incredible. Were we put the pulleys for the water rudders around the longeron, each of the brackets are corroded, and the one longeron is in really bad shape.

This was on floats starting about six years ago, and was washed out after every salt use. After beach landings I would hose it off.

My conclusion is that one should try to keep all metals the same, or have good separation.

[pittsdriver]

Bill, We machined a few throttle knobs with a PTT in the end. I have a couple I can sell. Email and I can send a picture. Don

dchapton@cableone.net

[Bill Rusk]

I will have to reweigh the mags. I forgot the impulse coupling. If we are going to post data it needs to be accurate. So stand by for a correction.

This came from the Airframes Alaska website ( I hope they don't get upset at me for reposting it here).

The question was about a widebody fuselage....

Question: How much more does it weigh?
Answer: Each customer gets different modifications on their fuselage but in general, the wide-body frame is 12 lbs heavier than our standard fuselage. In a recent comparison, we weighed an original piper fuselage at about 95lbs. A comparable standard fuselage from us with the basic modifications for strength and safety, weighs about 109lbs*. A similarly equipped wide-body frame with steel stringers weighs in at 125lbs*. A business partner recently reported to us that a competing standard frame weighed 127lbs! *These weights include our recommended prime powder coat.


I have tried to get the weights of the Cub Crafters AL struts but I have not had much response.

Nathan - I will be watching the hardware too. Thanks for the info.

Dave - I have considered the no trim issue. I think I can live with it for one flight to get back to a repair point. I would just have to fly at the last trimmed speed for greatest comfort for a while. It is not so much for the weight savings on this item as the convenience. It is really nice to trim without having to take your hand off of the throttle. Personal preference. I would also loose all my avionics too as I will have a glass panel again to save weight. Good idea to set up a connector for the mags. I will add that to the list.

Bill

[kevin]

Bill, Will you be going with a Wide Body?

[Bill Rusk]

Kevin

No, this one is a narrow body. The last one was a widebody, and it was certainly good but in this case I think I will be just as comfortable and lighter. In addition to the weight of the bare frame you must also take into account the wider and heavier windshield, floorboards, skylight etc. I am fairly small in stature so I fit into a std. Cub fine. For others the widebody will be worth the weight and offset by the comfort.

Bill

[tempdoug]

Brake master cylinders up front? No rear throttle lever? 1/2 size header tank, if any? No rear control stick? For saving weight i sure wish J. Burr would chime in here and share some secerets especially on the other subject thats running now. JERRY? doug

[kevin]

Kevin

No, this one is a narrow body. The last one was a widebody, and it was certainly good but in this case I think I will be just as comfortable and lighter. In addition to the weight of the bare frame you must also take into account the wider and heavier windshield, floorboards, skylight etc. I am fairly small in stature so I fit into a std. Cub fine. For others the widebody will be worth the weight and offset by the comfort.

Bill

Thanks Bill. You make a good point with those other items. I am a small person so I would stick with a narrow body too.

[mikeo]

Bob I have a 1.2 amp hr battery back up weighs 10 OZ works great is 11/2 inch Mikeo

[Bill Rusk]

More info on Mag weights

The Slick 43XX series bare mag weighs 63.625 oz
The gear that goes on the shaft weighs 4.24 oz
The Impulse coupling weighs 12.025 oz
The spacer for the impulse mag weighs 4.805 oz
The complete harness (both sides) 26.54 oz
(4) REM 40E plugs w/washers 15.63 oz
Total Slick package (2mags, 1 w/ impulse, harness, 8 plugs) = 210.36 oz, 13.1475pds

According to Brad Dement From the E-mag company the complete and comparable P-mag set up weighs right at 10.0 pds.

A weight savings of 3.14 pounds.

The weight savings over a Bendix set up is 6.2pds

According to Klaus Savier at Lightspeed Engineering his system is 4 pounds lighter than a mag system but that is without a backup battery which would add weight, the amount depending on the size and weight of the battery selected. No back up battery is needed with the P-mag set up (except possibly a 9 volt to get the engine started in the event of a totally dead battery). With the P-mag set up the engine will continue to run with total electrical failure as the P-mag has an internal alternator (that works above 400 RPM) kinda like the standard mags. The lightspeed ignition system does not have this feature so that with total electrical failure the engine would die unless you have a back up battery to keep things going until you can find a place to land.

So basically, electronic ignitions save about 3 to 6 pounds, give or take.

Bill

[spinner2]

More info on Mag weights

So basically, electronic ignitions save about 3 to 6 pounds, give or take.

Bill

There are other advantages to electronic ignition too besides the weight savings. Variable timing with RPM and manifold pressure inputs is the big one. And changing timing means a noticable improvement in fuel consumption and a no-hesitation response when the throttle is opened quickly.

Mags are 1930's technology and electronic ignition is 1980's technology.

[Bill Rusk]

Yes, I was remiss to omit the performance aspect of electronic ignition. Lou Furlong has personally enjoyed the emags/pmags for years and has also shared that info with others. I think this is pretty much a win win. Lighter and better.

Tempdog I agree that those items you mentioned will save weight but I think I will be a little closer to stock in most of those items. I want a stick in the back, throttle, and brakes too. It seems I often fly with others and I want to be able to trade landings, do a little instruction (not for hire, I know the rules), and let my pax fly a little too. But keep the ideas coming.

I had a nice visit with Jay at Javron today. I will have my fuselage completely sandblasted, use a zinc rich primer powder coat, (with emphasis on the most common corrosion areas), followed by a powder topcoat. This will cost a bit extra but I feel this will provide the best corrosion protection for an airplane that I expect to put on floats and quite possibly in salt water as well, ie the Southeast Alaska area. The fuselage will be weighed before and after for the record.

As I mentioned before Jay is interested in building fuselages a bit closer to the original plans. Plans call for all the truss members of the fuselage aft of the cockpit (excluding the longerons) to be .028 wall thickness. Seems everyone has gotten in the habit of using .035 for everything in the aft part of the fuselage. Jay has two fuselages now, identical except for the tubing thickness aft of the cockpit and they will be weighed in the next day or two. This will give us a firm and accurate measure of the weight penalty incurred for this "modification". I put modification in quotes because I am not really sure that it was ever a customer demand, but I think rather the kit companies and aftermarket fuselage guys just fell into it because it was easier to use all the same size tubing to keep things simple. I certainly understand that, but it adds unnecessary weight. We will soon find out how much. Thanks to Jay for taking the time to weigh things out and get back to basics. My fuselage will use the .028 tubing as per the plans.

Hope this helps

Bill

[mike mcs repair]

....will have my fuselage completely sandblasted, use a zinc rich primer powder coat, (with emphasis on the most common corrosion areas), followed by a powder topcoat. This will cost a bit extra but I feel this will provide the best corrosion protection for an airplane that I expect to put on floats and quite possibly in salt water as well, ie the Southeast Alaska area.

one thing I have considered, but not really done/thought threw yet, is drilling bolt hole a little larger BEFORE powder coating, since that seems to be where the corrosion starts UNDER powder coating when you have to drill ALL the powder coating out of a hole to fit bolt in..... in problem areas like tail spring mounts.....

drilling holes slightly larger will allow some powder coating still and hole and keep it sealed......

thoughts??? good idea???, bad idea????

[skywagon8a]

Bill
I understand the idea of keeping it light. Are you also considering what happens to the C.G. when you lighten some areas? For example: Using .028" wall tubing instead of .035" in the aft section will move the C.G. forward. I know not much, but it is part of the equation. The bulk of SC improvements have a tendency to shift the C.G. forward.

Mike
My vote--bad idea. Although there is often slop in a bolt hole should it not be the best fit possible? Just assemble it with a good water proof grease to counteract the corrosion problem. Don't start with an over sized hole.

[Dave Calkins]

Mike, my thoughts follow with skywagon8a on the oversize hole concerns. I'm open to more discussion on it.

Bill, my thoughts follow with skywagon8a on the issue of light tubing in the tail and forward CG tendencies of "improved" Cubs. It takes more than just "lightweight" to have a good flying cub, in my opinion.

[SuperCub MD]

Bill,

Using the lower longerons for the baggage floor is a good idea. I'd run the floorboards flat from the firewall all the way back. You don't have to run the elevator cables under the belly. Cover them with a aluminum hat section and make the rear seat bottom removable like a A model. Less weight and a lot more usable space.

I'd see if this guy would build a A model frame to start with, and finish the turtle deck and windows like Wayne does.

Boz

[mike mcs repair]

Mike, my thoughts follow with skywagon8a on the oversize hole concerns. I'm open to more discussion on it.

ya....

I didn't mean big sloppy over size, just a few thou or so, so when you drill out most of the powder coat, there is some left in there keeping edges sealed.... no different than a bolt cad coating or chrome changing the dimension of something/taken into account.... but alas powder coating is soft.....

[Bill Rusk]

Pete - that is a risk. In a perfect world the CG will be forward in an empty config so that when you stuff all your camping gear in it you do not go aft of CG. But that also makes it a little less pleasant to fly when light as the forward CG impacts the handling and feel. I do not know where the CG will end up right now so all efforts are to keep it as light as possible in every area. Remember, this is not something new, I am only going back to the original Supercub specifications.

Mike - I agree that it hurts to disturb that nice paint and corrosion protection but I guess we are stuck. A good grease is about all we can do. I have contemplated the same thing you are talking about. Perhaps a little Vari-prime in the hole as it is very thin and might still help a little.

Boz - great to hear from you. Been a while. Thanks for the suggestions. I did not go with an A model, guess I could have, honestly did not think about it. But Javron would build you one if you wanted. This guy can, and will, build you whatever you want. No doubt he could do what you suggested. Probably a little late for me but might work for the next guy.

To all - My understanding is Jay now has drawings to a new three piece stamped rib that will be much lighter than the built up ribs from D&E, Carlson etc, and will be used in his wings. This rib will be closer to the weight of the original Piper rib, probably stronger, (I have not seen the engineering data but it was designed by an aero engineer that frequents this site) and should take several pounds out of the wings, again getting back to the original Piper weights. It make take a month or two to get the ribs in production but the wheel is in motion. So, for those of you scratch building and in need of ribs, I think you are going to have a great option available soon. I know Jay is also going to make a complete wing kit available soon using these ribs.

Great things are happening.

Hope this helps

Bill

[Bill Rusk]

Christian Sturm came for a visit. When I last visited him he had turned me on to the little Honda CT-70 minibike (also used by Addison Pemberton) as a great little way to get around the airport. I happened on to a good deal on Craigs List, so I now have..... not one, but two of these little Mini-Trail bikes to play with. These are 1993 models. Great fun, and there is quite a following of the CT-70 on the net, so web sites, forums, support, and parts are readily available. Cool new toys.





Christian and I went to the Midwest Antique Airplane Club (MAAC) fly-in at Brodhead and got to see lots of classic airplanes like this beautiful Travelair 4000.






I got to fly this Marquart Charger. Neat airplane and fun to fly.






Then it was back home where we spent a little time playing with the Hatz.








A great time. I am fortunate indeed to have Christians friendship and I am thankful for his help after my little "splash and stop". (a different way to do a "touch and go").

Bill

[kevin]

Hi Bill, I have a friend of mine who was at Brodhead in his Travel Air. From what he has told me about it in the past, it sounds like a magical place. That is a cute Hatz you have there Bill, the way the front cowl tapers to the engine reminds me of a Travel Air. What engine do you have?

P.S., Those wing ribs sound great!

[Steve Pierce]

Bill, I don't like powder coating myself. Saw an Airframes fuselage after it sat in a hanger at Broadhead for a few years and all the places I use an airbrush on to make sure there is paint everywhere had little rust spots. Epoxy primer and polyurethane top coat work for me. If you use powder coating use a reamer to clean the hole and put grease in the hole or roll the paper you wrap steel internal engine parts in and insert it in the hole till assembly.

I spoke with Airframes yesterday and they are working on certifying an A model fuselage.

[Iflylower]

I'm of the same opinion on powdercoat. I'm not happy with it and wouldn't do it again.

I LOVE the sound of those new ribs! Can't wait to see them.

[kevin]

I have to agree with Steve on the powdercoat issue. I've been told to stay away from it because it adds weight, it is hard to make a repair after it is powdercoated and hard to see cracks under the powdercoat. With that being said, I understand why guys powdercoat. My dad powdercoated his airframe on his Champ he restored in Seattle area. He did it because he couldn't have it primered in time before the rust started to set in after it was blasted. I will say that they look great after they are powdercoated though.

As far as primering is concerned, I used Stitts EP-420 green on my airframe. I'm a firm believer that if a good 2 part epoxy primer is used, such as the Poly Fiber's primer, that will provide superior protection in itself.

[Bill Rusk]

Well after all that input I may have to change the plan. What everyone normally seems to do is, 1) sandblast just the bad places ie welds with a lot of slag, 2) clean with a phosphoric wash, 3) powdercoat

I was hoping to improve on that by....1) sandblasting the entire frame, gives better adheasion and does not coat over already started rust...then 2) primer powdercoat ....then 3) top powdercoat

Have any of you guys had any experience with that? Were the problem powdercoats due to no prep, or no primer first?
It does seem that a lot of powdercoating is done with little to no prep first.
Cal - what was your experience?

Gathering data here and not afraid to make a 180 degree turn if required.

Thanks

Bill

Kevin - Thats a Warner Super Scarab 145hp

[MainlandCub]

Bill,

Using the lower longerons for the baggage floor is a good idea. I'd run the floorboards flat from the firewall all the way back. You don't have to run the elevator cables under the belly. Cover them with a aluminum hat section and make the rear seat bottom removable like a A model. Less weight and a lot more usable space.

I'd see if this guy would build a A model frame to start with, and finish the turtle deck and windows like Wayne does.

Boz

Who is Wayne and how does he finish the turtle deck and windows.

All I've ever had is A models; they make more sense to me than the other kind anyway.......

[Marty57]

It's interesting that certified lifetime lift struts can be purchased powdercoated or not. So, there must be a way to do it correctly. The other problems of not being able to see cracks as easily and repairability still would exist. Has anyone used Stewart's metal primer on a fuselage yet? I have used it on smaller parts and like it but nothing big yet.
Marty57

[kevin]

Bill, I can not tell you on the process. The powdercoater will blast, then powdercoat. I thought powdercoat was powdercoat and didn't know about a primer powdercoat then top powdercoat. I personally would just stay away from it in general and only blast then epoxy primer. I think that would be more than sufficient. If you are on float and in salt, then I would suggest the polyeurthane top coat too. All in my opinon. I'm sure what you choose will be the right thing to do.

[spinner2]

I was hoping to improve on that by....1) sandblasting the entire frame, gives better adheasion and does not coat over already started rust...then 2) primer powdercoat ....then 3) top powdercoat

Have any of you guys had any experience with that? Were the problem powdercoats due to no prep, or no primer first?
Thanks

Bill

Kevin - Thats a Warner Super Scarab 145hp

Bill, I had a fuselage powder coated as you described; sand blast and immediately go to the zinc-rich primer half backed and then top coated. Worked really well. I've had a lot of parts and pieces coated over the years, aviation related and otherwise, and I've never seen a problem with powder coating.

[mvivion]

Just as a reference point, I operated a 1969 Super Cub on floats in summer and some on wheels in the (short) winters in Kodiak. That airplane did a lot of sitting on a bank on floats before I got there, but in the eight years I was flying it, it pretty much got used all year. It was REGULARLY in salt water, with only a splash into fresh water after. In winter, it landed on ocean beaches regularly. No hose, no wash down.

In 1984, the Grade A cotton fabric was getting weak (airplane was never hangared) so it went to Center's shop for new fabric. I wasn't at all sure I'd ever see the plane again, because I figured it would be badly corroded. Turns out that the frame was in great shape, even after a LOT of exposure to salt water and salty air. I was impressed.

Those airframes were carefully and thoroughly coated with zinc chromate.

I think the key is go do a thorough and effective job getting whatever coating you use on the frame.

I'd be skeptical of powder coat just because of the difficulty of repairs.

MTV

[Bugs66]

Hey Guys, I had a fabulous time at Brodhead this past weekend! Bill was a gracious host and made me feel at home. This was my first Brodhead and I thought it was the best fly-in I have been to yet. I took a lot of video and will get some up on You Tube soon.

For those of you interested in Bill's Hatz, I had the pleasure of flying it and I can tell you this is one honey of an airplane! That combination of the Hatz and Warner 145 is a match made in heaven. Beautiful plane that flies superb. Mehlin Smith, the builder, got it perfect with his modifications. Here is a cell phone video I made at Bill's place, will get some HD video of it up in the future.
http://www.youtube.com/watch?v=hDrrojUbPBs

WP_000127.jpg WP_000126.jpg

[mike mcs repair]

Fully blast it, and Powder coat it. I would never go back to primer... Never ever... To repair/weld you just hit area to weld with oxy torch. Then brush of with wire brush. Simple....

All I use. Might call advanced powder coating in big lake and pick their brain. Only place i have used since they opened 15 - 20?? years ago...

[jgerard]

Painting or powder-coating it all boils down the the craftsmanship of the person doing the work. Properly done by the right person there are advantages to both. I myself prefer to prime and paint.

Marty in regards to using the EkoPrime or EkoPoxy on a fuse. Works great and both have a ton of anti corrosion additves. That being said, My self and anyone else whose primed and painted fuselages will tell you it's one of the least favorite thing to prime and paint. FYI never just leave steel in bare primer. Primers, primer sealers, Epoxy primers, are all still just primers and have never been intended to be left with out a top coat of paint. Epoxy primers are not UV stable and break down quickly in direct sunlight.

Jason

[StewartB]

When I received my PA-12 airframe it had piss poor powder coating. That was my one and only bad experience with powder coat. After the crummy powder was removed from the -12 it was phosphated, primed, and powder coated locally. Tough, attractive, and flawless to date. My 180's gear has lived outdoors for the 15-16 years since it was coated by Advanced in their start-up days. Other than the expected gravel dings it's perfect. Where the dings have rusted there's no evidence that the adjoining powder is being compromised. Tons of other parts are powder coated in both my planes. Three different shops have done the coating. Rudder pedals, floor boards, headliner, gear, panels... all perfect. Zero complaints. I'll stay with powder for any aircraft part where it makes sense and I recommend it to my friends who ask.

SB

[MainlandCub]

As I mentioned before Jay is interested in building fuselages a bit closer to the original plans. Plans call for all the truss members of the fuselage aft of the cockpit (excluding the longerons) to be .028 wall thickness. Seems everyone has gotten in the habit of using .035 for everything in the aft part of the fuselage. Jay has two fuselages now, identical except for the tubing thickness aft of the cockpit and they will be weighed in the next day or two. This will give us a firm and accurate measure of the weight penalty incurred for this "modification". I put modification in quotes because I am not really sure that it was ever a customer demand, but I think rather the kit companies and aftermarket fuselage guys just fell into it because it was easier to use all the same size tubing to keep things simple. I certainly understand that, but it adds unnecessary weight. We will soon find out how much. Thanks to Jay for taking the time to weigh things out and get back to basics. My fuselage will use the .028 tubing as per the plans.

Hope this helps

Bill

Bill,

I have the frame tubing from the Northland CD drawings entered in a spreadsheet. Today I changed the .028 wall thickness tubing to .035 wall thickness to see what the weight difference would be. It is 3.4 lbs. It will be interesting what you and Jay come up with as a difference when you weigh the frames.

As for the effect on c of g, I can't tell the difference if I remove the towhook on a Cub, which is more than 3.4 lbs and further back.

Andrew.

[Superchub]

Fully blast it, and Powder coat it. I would never go back to primer... Never ever... To repair/weld you just hit area to weld with oxy torch. Then brush of with wire brush. Simple....

All I use. Might call advanced powder coating in big lake and pick their brain. Only place i have used since they opened 15 - 20?? years ago...

I second Mike. This can't repair stuff is bologna. I have repaired several RV-6 rudder pedals and engine mounts with powder on them and I have always used this trick. Works great!!

[Bill Rusk]

Folks

First let me say "Thank You" for all your inputs.

Lets talk weight and drilling brake rotors out.

A Supercub friend told me he drilled his rotors and saved 1.5 pounds (24 oz). I don't think he is quite as fastidious about all this weight stuff as I am, or perhaps his rotors are much different than mine, but at any rate I had my rotors drilled to save weight. They now look like this.......




The Bottom line.......

The rotors before drilling weighed 45.300 and 45.050.
After drilling they weighed 41.145 and 41.375

Net saving 7.83 Oz.

Not much for 200 dollars. So, I am now of the opinion that this is not a very cost effective weight savings area. Which brings up another point. How much is too much? I think the "cost per pound saved" value will vary from person to person but once you get over 100 dollars per pound you are getting pretty fanatical. With things like light weight starters and alternators you are in the 50.00 dollars per pound zone, i.e. a 500 dollar starter saves you 10 pounds. This effort saved me 1/2 pound and thus the relative cost was at 400 per pound. That is way too much for me and I will chalk this one up as a mistake. But now you know the hard facts and can make your own personal choice.

Hope this helps

Bill

[cubdriver2]

Bill why not drill out the rest of the hub not just the rotor area

Glenn

[Iflylower]

Good point Bill. I'd bring up 10 years ago when I was really into mountain biking, doing some light racing and building as light as I could.

I found two things:

1. Buying light parts.... I made a lot of improvements at first dropping weight drastically. I hit a wall where significant part cost was gaining merely a couple grams of weight savings when lunch made a hellava lot more difference. (Side note: rotational weight paid off tremendously on rims and light knobbed tires.)

2. The lighter I got, the much more maintenance I was doing. I had light components, but they weren't taking the bulldogging through the rides. I was truing wheels a lot more and stretching lighter cables, and breaking chains and derailleurs.

I think the same can apply in cubs to an extent.

But Lord, light is fun! Thanks for weighing Bill.

[skywagon8a]

Bill,
I seem to recall from the back of my memory bank that brake disks of this type were offered at one time. A friend bought a set and found that the brake pucks wore out in less time than the undrilled discs. The edges of the drill holes acted like a shaving tool.

[brown bear]

Bill
Now that you have become a "Homebuilder" you need to start thinking like one!
Why pay someone 200$ to drill 200 holes?
It would be good to hear how the holes affect the brake pad life
Doug