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Building a Javron Cub

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.
 
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.
 
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.
 
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
 
18a

SuperCub MD said:
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
Click to expand...

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.......:smile:
 
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
 
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.
 
Bill Rusk said:
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
Click to expand...

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.
 
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
 
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

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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...
 
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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
 
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
 
Bill Rusk said:
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
Click to expand...

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.
 
mike mcs repair said:
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...
Click to expand...

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!!
 
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.......

IMG_01601.jpg



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
 
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.
 
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.
 
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
 
Bill,

you could have brought them up here and done it yourself on my mill...

Next time you have a part to take metal off, bring it up and we can talk flying and do machining... not much flying for me for a while
 
Maybe a small chamfer to help wear? What do those race cars do for their drilled disks?

cubdriver2 said:
Bill why not drill out the rest of the hub not just the rotor area

Glenn
Click to expand...

I do like that look. And it does save weight. Maybe make swiss cheese out of that thing?
 
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Bill, I know it is a lot of money for what was done but in the grand scheme of things, it is just about a half pound savings. Another one of these type of savings and you just saved a pound! I have a friend who did this on his SQ2. They look good and they saved him weight.
 
In racing we no-longer run drilled rotors, we machine grooves, this achieves the same affect, allowing gases to escape improving performance, but is less pron to cracking.
Drilled rotors should have improved braking on water assisted landings.

Sent from my HTC Evo using Tapatalk
 
Looking at your pictures, it doesn't seem that you removed very much (volume of) steel. From what I understand, 'properly' drilled automotive rotors have chamfered edges on the holes. Drilling isn't done for weight savings in auto applications - it gives gasses a placed to go under heavy braking as opposed to floating the pads.

Live & learn eh?

I'm learning a lot from reading this thread. Thanks for starting it.
 
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Chamfering yes a must and DON'T use cleveland pads use grove's kevlar pads or Greg Millers. I use Millers more money but at this point I quit counting.
 
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It sucks to not own your own CNC mill

Well since I am the one who is the culprit here for doing the drilling I feel bad that you feel you were ripped off. Just a few things from my own experience with drilling holes in things to save weight. I did it for myself initially and it worked great, it does not need a chamfer from my own experience. I have thousands of landings on my pads and discs (over 1200 hours and have not replaced them). The discs still look new and the pads are probably still 50% today. These holes don't work like a cheese grater because your pads are parallel to the disc, nothing is sticking up to grate.

I have drilled them for others and I think it is about 1/2 pound per disc if you have the thick ones (2 rivet brake pads). The thin discs like Bill Rusk had (3 rivet pads) take less material because the brake disc is thinner to start with.

I would rather not do this for anyone because it is not really worth the effort to drill 2 brake discs. Set mill up with three jaw, touch tools off, center drill a lot of holes and then drill a lot of holes, box parts up and invoice, take parts to post office and make $160.00 Believe me when I say this is a hard way to make a buck.

For those that wish to have them drilled I will still do it but be warned this is as Bill says an expensive way to save weight if you don't own a CNC mill, I do, so it is cheap for me.

Greg
 
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Mauleguy said:
Well since I am the one who is the culprit here for doing the drilling I feel bad that you feel you were ripped off.
Click to expand...

I didn't get the feeling that Bill felt ripped off from his post. I read it as he didn't think the weight savings is worth the cost or effort. Nothing bad about the person that did the work, it all takes time, experience and expensive equipment.
 
The chafering reduces cracking that could originate at a drilled hole. Discs on a Cub probably don't get hot enough for heat stress to cause cracking. After a track day with my car, sometimes the discs were blue from the heat.
 
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