New member building a PA18-95

Build three and have a family squadron.

Wife and three boys can take the 172. She grew up outside of Chicago and is used to evasive maneuvers and a lot of tailgating. Following a Cub in a 172 is a lot like creeping along in heavy traffic. She'll know what to do. I'll have to install a horn. Daughter and I will take the Cub. We'll be typical rural folk taking our time getting lost and gawking out the windows. It will be perfect.

Possible nose rib

Took some time before work tonight and bent up a prototype nose rib just to see what it would weigh. I used .016 6061T6 an inch wide and mimicked the capstrip from Carlson. The intercostals are the same .016 2024T3 that I used in the other ribs. It is light, .99oz. Seems like I saw on Bill Rusk's thread originals were something like 1.1oz. It's not near as strong as the extruded capstrip, but my gut tells me it won't need to be if it is between the other ribs, rivited to and supporting the leading edge. Trying to decide if I want to experiment with making a CF leading edge and leaving out the nose ribs if it can be made stiff, light, and strong enough, or just doing something like this. If I can come up with something light enough that I can bend up easily and cheaply, maybe playing with CF for the leading edge won't be worth it for me. Looking for some thoughts.

Thanks,

Jim

Jim,

I'm just learning about composites in airplanes. I have been playing with vinyl ester over CF and glass. I haven't been able to do hand laid parts that are lighter than their alum counterpart...but I may not be the right person to ask. I think I need to try vacuum bagging before I really make a decision. I have a few hundred dollars invested in "stuff" and it would be another several hundred to get a basic bagging system which I guess I'll do to make sure before I give up on composites. It must be lighter...I just need to learn to do it correctly. If you do it, please share what you learn.

Field repair might be easier on an AL leading edge. Just a thought.

Marc Davis said:

Field repair might be easier on an AL leading edge. Just a thought.

Click to expand...

The other side of that issue.. Carbon is a lot more resilient.. we whacked a 1" willow top (at the wing tip) last fall hard enough that it turned the aircraft. After landing we noticed no damage (except) the broken willow top!

One guys opinion ;-)
frank

BTW Jim.. that's looking like a f_u_n family project.. just the way it's suppose to be. Now you need to get started on the next one so you have one for yourself!

Grounded youth pilot/builder

Frank,

It is fun. For many reasons. This memory is priceless. Wife told Ellis he wasn't allowed to help in the shop last night because it was too late. Needless to say, he was displeased.

Milestone reached

All of my ribs for both wings are done. Both sets of ribs weigh 19lbs, 10oz.

As I posted earlier, my aileron ribs weigh 9.6oz.

My full ribs weigh 11.4oz.

I decided to make the capstrip for my nose ribs out of .025 6061 T6. Anything lighter wouldn't make the bend without fracturing. Weighed 1.3oz.
In the end, fluting pliers made the bend.

I am using three types of ribs. Full, aileron, which I will also use in flap bays, and nose. Going to use original style LE wrap. CF would be lighter, but for me, old school seems the best option for weight/cost.

Storing the ribs for now, going to make ailerons and flaps before I order my spars.

Thanks,

Jim

Nice work and well done!

I pretty much came to the same conclusion regarding carbon parts. If you are in a production mode and have the time and money to make the molds then carbon may be worthwhile. I played with it and found the carbon nose ribs I made weighed more than the aluminum ones. I'm sure they were resin rich but that was the best I could do...back to aluminum and rivets.

I've worked as an airplane design engineer for 30 years and the only chance you have of making a part lighter with carbon fiber is if you use an autoclave. If you are hand laying up parts forget it aluminum will be lighter. If you are designing a part using a clean sheet of paper you might be able to make it lighter in graphite. Black aluminum (which is what we call aluminum parts manufactured using carbon fiber) will never be lighter in weight.

Sent from my Galaxy Nexus using Tapatalk

Some alloy choice questions

I have some questions concerning Piper's choice of different alloys and where/why. Some of these questions may seem a little stupid, I don't care, I'm just trying to get a better understanding of what can be used where and why. I'm also curious as to whether anyone has ever tried some of these ideas.

Why was 3003H14(3S1/2H) used for the wing and aileron/flap leading edges? From what I read, most guys use 2024T3(24S-T) now on the wing leading edge. I understand it's the strongest, and less likely to dent, but it's also the heaviest. If one was able to form it, could 6061T6(61S-T) be used for the leading edge? It would be slightly lighter still than 3003H14 and more dent resistant. What are the problems with using it here?

.032" thick 3003H14 was used for the flap and aileron spars. Why would you use a weaker material that bends easily here? Could .025" thick 6061T6 be used instead? Once it's boxed in with the leading edge and all the bulkhead ribs, I wouldn't think it would twist. Why the choice of 3003?

The plates(gussets) that are at the top and bottom of the aileron/flap ribs where they join their spars are also 3003H14 .025" in thickness. The ribs they attach to are .020" 2024T3. From some simple testing that I did, the small plates fail first. This tells me that maybe the ribs could be made from .016" 2024T3 and fail at the same time the plates do. Has anyone ever done this with success?

Not deviating from the plans would be the obvious "right" thing to do. I'm not suggesting anyone do anything I've suggested here, nor am I saying I will. Again, I'm just curious if anyone has tried anything like this before with good results in the pursuit of weight savings. I'm also trying to learn a little something about what alloy can be used where and why. PM me if you don't want to share publicly.

Thanks,

Jim

I have been putting more than a little thought into aluminum types as well. Here is what my experience has got me thinking:

I will only use 3003 for interior panels. It is one of the easiest to shape, bend, form but is also one of the weakest of the aluminum alloys.

6061 is about tne strongest of the alloys. But dont try to put any sharp radius bends in it as it will just crack. The best applications would be gussets, structural braces or brackets. I wouldnt use it on the leading edges just for fear of it cracking when / if dented by those pesky willow bushes.

2024 has some outstanding strength and corrosion resistant attributes. I think it would be my choice for leading edges, cowling doors or anything else that requires bending, breaking or forming to produce the part.

Now a fourth option that airplane guys dont often talk about is 5052. I use it almost exclusively. You can bend, form, draw, extrude and weld 5052. I build tool boxes,cabinets and fuel tanks with it on a regular basis. I dont see why you couldnt build all the aluminum parts on cub with it. 5052 is used mainly in marine applications because of its strength, corrosion resistance and weldability. It's also more readily available at your local steel/metal provider. My fuel tanks instrument, panel and maybe my cowling will be 5052. The other thing about it is it anodizes really well. How cool would an anodized panel look?

As an Al-Cu alloy, 2024 is terrible in corrosion, absent the alclading. And 6061 is good for corrosion and easily weldable. Here's an interesting document - - http://www.alueurope.eu/talat/lectures/1501.pdf

My LE's are all 6061t6

The Zenair machines are built from 6061-T6 almost exclusively. It s a bit weaker than 2024 so you have to design with that in mind, if it's a load carrying element.

Progress after one year

Here are some pictures of what my scratch build Super Cub looks like after one year. Nearing the point where I can put stuff together so other people can actually see an airplane here. I can see it. Can you? One down, three to five years to go. Watching a guy scratch build an airplane is probably like watching paint dry or grass grow. Need to get in front of an 8' brake and slip roller to bend up flap and aileron spars, finish leading edges, etc.

Thanks for all your help,

Jim

Looking great Jim. There is a tremendous amount of well done tedious work shown in your pics.

Jim

Fantastic. Great job!! Thanks for posting pictures. Looks like a wonderful family and a great project.

Keep it up!!

Bill

What a wonderful start with what looks like high quality parts!! I understand the frustration of plans building but there is also a strong feeling of accomplishment when you finish each little part. Keep the faith!!!

Question on thickness of false spar

On the Northland plans, the false spar for the aileron bay is shown to be .016 with bracing. In the flap bay, .025 without bracing. I have aileron ribs throughout and I don't want to do the bracing to the false spar. I have quite a bit of .020 3003 that I could use here. .016 in a different alloy would definitely be lighter, but I assume then I'd need the bracing. I'd like to know what other people have used for thickness of their false spars without bracing.

Thanks,

Jim

Had to do some necessary improvements on my tax burden this Fall and early Winter. In case you need to know or are curious, the life span of TYVEK in Northern Minnesota is 6 yrs. The shop looks a little goofy, but I plan to extend the roof out in the next few years to shelter my stuff. I also reorganized/finished the inside of my shop to make it more user friendly. I moved my table to a better location and put everything that was heavy on casters so I'm not fighting my work area so much. If anyone has not tried the incandescent style LED light bulbs by the way, I recommend them, really nice bright light.

I also spent what my wife feels should be airplane money on some tools that I've been doing without that will come in handy for the build. Used cheapy horizontal bandsaw that can be used in the vertical position, a plasma cutter for stainless and other heavier non-ferrous parts. I also bought a couple of smaller torch kits and new regulators. My old regulators needed new innards and were obsolete. My old torch kit was better suited for bridge work, (Too big and heavy for welding).

I've nearly completed fabricating all my aluminum parts for the wing. I have posted some pictures of flap/aileron spars, cove pieces, trailing edge for flaps/ailerons. Gage and Ellis are holding those. I decided to go with 8' ailerons and 8' flaps of standard chord. I showed the boys how to put a plug in a flat tire on Sunday. Both were relieved it was a screw that was extracted and not one of their nails. I am working on my drag stuts, N-braces now. I plan to order my spars and drag wires very soon. I can then put most of the wing together, make the tanks, so on and so forth. Hopefully by June 1st, I'll have something big and unhandy to hang up somewhere in my shop.

If someone has a stock drag strut and just a drag tube plug lying around and would weigh it for me, I'd appreciate it. I had to make some changes because of availability of materials and I'm curious how mine compare.

I've been following everyone's progress since I posted last. Hat's off to Bill Rusk, Lowrider, Olibuilt, and Larry Vetterman (and of course everyone else I failed to mention).

Thanks,

Jim Allen

Jim,

Looks like progress to me!!

It's great you are involving your boys, they will learn a lot even at that age and you will reap rewards from their help. My youngest 2 were about that age when I was working on my RV-4 and it was a circus at times but wouldn't have changed a thing. I'm still learning too so keep an eye on Bill's work...it's a thing of beauty for sure!!

Good looking work. I like your shop. I believe in a separate building to keep the fumes of covering , painting, welding etc out of momma's house. I'm a career night person in my job and my life so I work on the back side of the clock most the time. Air drills at 3 am aren't good for the rest of the sleeping family. You probably have real winters compared to me but I just traded for a wood/coal stove and love the heat it makes. Also glad I'm not buying propane anymore. Keep the pics and progress reports coming.

Primer/Paint question

I am working on what seems to be a mountain of steel parts for my wings. Making good progress. My question/questions are: For the steel parts that are in the wing, is just primer acceptable, or do they need a coat of paint as well? I would prefer not to paint them if not necessary for weight savings. Most everything is 4130. For the parts that will be seen, they will get primer and paint. I am planning Oratex fabric with no paint over the top. Is there a good rattle can primer that someone can recommend? Lots of small parts that won't require a ton of primer. I will post pictures soon.

Thanks,

Jim

SEM products self etching primer is the best I've found in a rattle can. Most epoxy primers don't need a topcoat, Polyfiber's epoxy is tough as nails, PPG's DP epoxy is another good one.

I just blasted all my wing hardware, tank straps etc, primed and painted. All the wire hardware is getting sent off to get cad plated. Going to prime the whole wing once it's assembled. It was primed before I tore it down but there was rust where the primer was worn down or missing. Piece of mind for me to prime and paint them.

http://www.ebay.com/itm/Moeller-Zin...Parts_Accessories&hash=item1e9a9a0353&vxp=mtr Ive used this for some things, hopefully you can get it without freezing. Lots of Moellers stuff on ebay. Just a light coat. Make sure your parts are clean, clean. Wear some thin plastic gloves. You keep that thing off your highways there in Minnesota you shouldnt have any problem.:lol:

http://www.semproducts.com/automotive-primers/self-etching-primer

Always worked good for me.

tempdoug said:

http://www.ebay.com/itm/Moeller-Zin...Parts_Accessories&hash=item1e9a9a0353&vxp=mtr Ive used this for some things, hopefully you can get it without freezing. Lots of Moellers stuff on ebay. Just a light coat. Make sure your parts are clean, clean. Wear some thin plastic gloves. You keep that thing off your highways there in Minnesota you shouldnt have any problem.:lol:

Click to expand...

I thought they stopped making zinc chromate.