PA-18A parts

[meinster]

Looking for the removable top deck frame, Piper part number 13257 (above hopper enclosure) or some pictures and data so I can fabricate one. Any info or help would be appreciated.

My fuselage has been modified several times (none documented or approved), trying to go back to original.

I would really like to see some pictures of 18A fuselages, in particular the turtle deck, hopper bay, hopper floor and structure just aft of hopper bay.

Cheers

 

[S2D]

Do you still have the lid on or are you fabricing over or is this a bare bones project?

 

[meinster]

I don't have any of the original Ag stuff for this frame, alterations under previous ownership had them removed. This started off as a simple project to accomplish a bunch of minor things, of course the deeper one delves, the greater the discoveries that eventually end up turning a project into a lifetime struggle.

See pictures attached for the interesting modifications that were accomplished.

 

[meinster]

In addition to the above the belly panel tabs had been removed and some minor changes were accomplished to accommodate a battery in the tail, again, no paperwork was ever submitted for these alterations.

So I'm leaning toward simply removing all the garbage that was added over the years and reverting back to the original fuselage layout IAW Piper drawings 13220, 13250 & 13255 (that I got courtesy of cub club).

Because I don't have any reference for the battery in its original location (in baggage compartment) I'll probably get under seat STC and do away with any unknowns there.

 

[cubpilot2]

Reinstalling the original Piper "insert" used when removing the hopper is not very desirable as it requires you to retain the original metal hatch and lid on the back of the fuselage. You will find lots of variations that people have used to eliminate this, from a simple diagonal 3/4-inch tube to using an X brace. The problems that most run into is the same as what you have found in having no documentation for the “major structural modification”. You will also run into problems with the FAA in getting an approval as they typically want to see the design go through an engineering review before they will accept it, which is very expensive and time consuming.
To the best of my knowledge there is no STC available to simply install the diagonal or X.
The only STC route that I know of that can help you is actually a very good design, which was originally developed many years ago by an individual by the name of Flanagan who sold it to Cub Crafters. The STC is for the installation of Plexiglas similar to the L21, and requires removal of the D windows and the adding the channels for the windows. The bracing for the hopper bay area requires the addition of two 3/4-inch tubes that originate at the aft corners of the opening and meet at the center of the forward tube which has the wing attach fittings. This is also the point at which most typically install a shoulder harness attachment tab. This now becomes a "supported attachment" point, which is a good thing. There are also a couple of tubes installed that go laterally through the bay as well and can be strengthened to provide for a rear harness attachment.
What I have done is to use the STC for the structural changes and then request an exception from the STC from the FAA in the form of a field approval to retain the original window configuration; which was easily granted.
At first I thought that this was an excessive approach for strengthening the structure but after completing it I have decided that it is the most desirable.
As you rework your fuselage give strong examination to the upper tubing that forms the hopper bay area as most were subjected to internal corrosion from water leaking through the “Rivnuts”. Also check the vertical tubing at the aft of the bay near the upper longerons as I have found corrosion there as well.

The 18A is a very good design and is far worth the effort to keep versus the temptation of replacing the fuselage to a “standard” type as many have done.
I will try to find some photos to add to this post.

 

[Steve Pierce]

Send me your email address and I can send you all the A model fuselage pictures I have. Some might shed some light.

 

[cubpilot2]

The Flanagan STC that I mentioned is SA887CE
From the looks of your photos you have a bit of a mess... Someone tried to loose the A model identity with the floor board changes and stringers etc.
I prefer the original low mounted floorboards which I extend forward to completely close up the floor. With the removable rear seat frame you have a very large cargo capacity. Fabricate a custom metal headliner to fit up to the hopper bay tubing and you gain lots more volume as well vs the standard cub.

 

[meinster]

Thanks a lot gents! I appreciate the info, ill look into that STC, sounds like the ticket!

Thankfully the fuselage tubing has limited corrosion, the rivnut holes were previously welded shut and ground down, I would have liked to put a panel back on there, but if they saved me corroded tubes by welding em, I'm not too unhappy.

Again, I really appreciate the feedback and any information, pictures, illustrations or blueprints you might have would be very helpful.

Cheers
Pete

 

[meinster]

The Flanagan STC that I mentioned is SA887CE
From the looks of your photos you have a bit of a mess... Someone tried to loose the A model identity with the floor board changes and stringers etc.
I prefer the original low mounted floorboards which I extend forward to completely close up the floor. With the removable rear seat frame you have a very large cargo capacity. Fabricate a custom metal headliner to fit up to the hopper bay tubing and you gain lots more volume as well vs the standard cub.

I honestly prefer anything that creates some space. Really like the idea of lower boards. What material can one use for this? Does it have to be plywood or can one use metal?

The L21 window conversion wouldn't so bad, seeing as my D frame channels are rusted out and need to be replaced anyways. What were your reasons for requesting the deviation and staying with original style? Aesthetic or functional?

I do want to go back to metal belly panels. The prospect of access to entire length fuselage from below is appealing.

You'll also note the most severe corrosion is present on all the things that were added post fact. So I have no qualms about removing that stuff and reverting to more unique looking flat back.

Any other recommendations, while she's naked?

 

[MainlandCub]

I have some Piper drawings for the original tin-top. PM me and we'll see how I can help. Might be a few days before I can get back to you, have limited internet access at the moment.

Andrew.

 

[cubpilot2]

The lateral tubing that you see replaced some channel material that was called for in the STC. The two smaller tubes running fore and aft were to support the rear shoulder harness attachment. Looks abit overkill but I wanted more support for the rear harness attachment.

Don't forget to add the front bulkhead X brace. Hopefully you will never need it. (this is a minor change as it dosn't intersect the original tubing to create any structural changes. (per FAA interpretation)

The floorboard extension is a lengthened center board and only requires a couple of extra attachment tabs. (minor change) I perfer plywood for the floor. It is quieter and just feels better.

I chose to not put the additional windows in after I calculated the weight of all of the glass required, and also from an astetic viewpoint.

I perfer to leave off all of the metal belly except for the last panel but typically leave the original tabs installed just in case there is a need. These things do make inspection access easier but they allow lots of dirt and moisture to get inside especially if on floats. Dirt plus moisture equals corrosion. The panels will also rattle loose eventually and cause problems with fastners and screws.

Notice the removable rear seat bar that it is hinged. It is a Roger Borer STC'd design. Most are of the Atlee Dodge variety that lifts out vertically and which I have on my other cub; but have found that my big Black Lab was always knocking it out..(not sure how he removed those little safety pins but he did )

Hope this helps

 

[meinster]

First off, I would like to thank everyone for their input, Andrew, your help is proving invaluable and Ed, your info has similarly proved very illuminating.

I called cub crafters a couple days ago (Vera is always so friendly and helpful) about STC SA887CE, they have the STC certificate but they don't have any installation data or the parts for it. That's somewhat disconcerting. I don't want to try scratch pieces together from all over the place.

I do like the look of that aesthetically, and the larger field of vision is appealing, of course having to lather up in SPF 50 before every flight might become tedious and I suppose, with all that plexi glass, there would be weight implications, but I am the same guy who still runs the boat anchor generator, in fact it might help offset the forward CG (especially after I remove all undocumented crap; turtle deck and relocate the battery via STC).

So right now it looks like I have four options;
1 - try to get it approved the way it is (as a matter of principle I don't really want to go there, that means I am giving my blessing to whomever for whatever they did illegitimately).
2 - get STC and piece together the necessary parts for it to be legit. Was there a flight manual supplement that accompanied that paperwork?
3 - revert to original, but I'll need to refer to factory blueprints (Piper drawings 14100, 13308 & 13312) showing that. In addition to which, all the holes (rivnut and frame mounting) were blanked off with welds, which means some careful drilling.
4 - similar to 3 above, but with some alterations that will need to be field approved, making it a one piece cover (without door) and amending the attachment method somewhat to do away with rivnuts going into upper longerons. This would have the added advantage of removing the corrosion threat posed by the holes in longerons.

Comments/Suggestions/recommendations?
Pete

 

[cubpilot2]

Pete:
1. Vera is an Awesome lady! When I worked with her about this STC (ten years ago) she wasn't sure about having the drawings at that time either but she searched their archives and found them. They were kind enough to have those drawings copied for me, and when they arrived they were full size (like 3 ft x 2 ft). The drawings were clear as to what is needed, and materials and all parts are cut from bulk tubing and the channel material which should be available in straight "bulk lengths" or fabricated as well. If they have lost the drawings then perhaps I should contact them to see if they want a copy back. I have some photographs of the drawings for my records but I can not share any of them without their permission.

2. There is no flight manual supplement.

3. To revert to the original from what you have would be much more work then to go with the STC change. If you are wanting to improve the value of your cub then you are taking a step backwards as very few people would have that preference. (My opinion of course)

4 To deviate from Pipers design for this cover would constitute a structural change and you are now again faced with the "engineering challenge".

Let me know if there is some way that I can help

 

[bob turner]

Interesting thread. I had no idea the A model was so desirable. If all that stuff above the longerons is structural, how come it cannot be considered structural when gluing fabric? I would think that anything other than main longerons and cabanes/ diagonals would not be considered structural. And they had rivnuts in the upper longerons? Yow!

Anyway, there are some definitions of major/minor alterations that would surely help here? Rumors are starting again that Field Approvals may again become viable, but I have heard that before. Lasts just long enough for a helpful maintenance inspector to be called on the carpet just before the stamp goes in block 3.

 

[cubpilot2]

Interesting thread. I had no idea the A model was so desirable. If all that stuff above the longerons is structural, how come it cannot be considered structural when gluing fabric? I would think that anything other than main longerons and cabanes/ diagonals would not be considered structural. And they had rivnuts in the upper longerons? Yow!

Bob:
The tubing in the "hopper bay" is structural in that it connects / supports the aft cabin wing attach structure to the aft fuselage. I guess you could refer to the outer tubes forming the bay as longerons, and yes they used lots of Riv-nuts in them, as well as the lateral tube at the aft end of the opening. There are no Riv-nuts in the main longerons.

I see no reason why you can't glue fabric to this tubing and in fact it is quite common.

I have seen many people drill out the Riv-nuts and weld the holes shut but you will often see the little bumps showing through the fabric and is unsightly. I prefer (when possible) to replace the tubing with new. This ensures that there is no hidden corrosion.

As to desirability; if all other things were equal between two cubs, one standard and one an A-model. I would pick the A. (just my opinion of course)

 

[Rice farmer]

Pete, we have obtained field approvals to remove the hopper door etc. in the past year. I am pleased with the way it turned out . As you have seen we retained the d windows and incorporated shoulder harness brackets in the new structure. If you need to see some of our paperwork let me know. Brett

 

[Steve Pierce]

Some pictures of an A model and hopper lid we took this weekend.
https://plus.google.com/photos/114718884762813339135/albums/5952784320254403841?authkey=CKr_8drA1ZL4Pg

 

[meinster]

Steve,

I'm not able to view the photos for some reason, either off browser or using the app. Id like to see them though

 

[Steve Pierce]

Sorry, Try this link.

https://photos.app.goo.gl/TnEjQnh6UuSQASDi6

and

https://photos.app.goo.gl/tCSNRDvc7BeMriD78

 

[Steve Pierce]

Just edited my link to make public.

 

[meinster]

Thanks to Andrew Phillpotts and John Scott, I just had three A model drawings scanned for the upper deck installation.

13308 door assy. top deck
13312 cover assy. top deck
14100 cover assy. top deck complete

All in one PDF.

If anyone would like a copy, just send me an email.

Thanks for those pictures Steve,was informative!

Cheers
Pete

 

[meinster]

PA-18A 150 fuselage

Had the FAA chap come by to take a look, thankfully a very nice guy with an awesome "can do" attitude.

Turtle deck
Restore to original state, no paperwork submission or logbook entries required. I'll leave the V section (writing it up "as found") conforming to Piper prints for regular PA-18 and submit 337 accordingly. That will allow me to keep the flat back without having to go back to hopper lid assembly.

Metal belly tabs are going back on as original (considered minor, so nothing more than logbook entry required)

Repair required
Corrosion to the lower lateral crossmember (10562-63 per Piper drawing 13220) between the aft landing gear attachment points. See photos. Any suggestions to expedite a repair with minimal structural messing about? Does anyone sell that tube with brackets already indexed, etc? The FAA would prefer to see it replaced altogether, I would prefer to affect a repair that won't require large scale cutting requiring jigs, manpower, etc.

Again, any help would be appreciated!

Just finished my instrument panel, also attached (need to do something to keep my morale up).

 

[Gordon Misch]

Check 43.13 - maybe can insert a new section with sleeves on each end. But probably just as easy to replace it. You don't need a jig; just tack weld a supporting piece(s) (such as angle iron) before carving out the tube, to maintain dimensions while welding in a new tube. Yeah, replace it. Make it match that great looking panel!!

New floorboard tabs are only $3 each here http://www.super-12.com/Products-Fuselage_components.html and are easy to install.

 

[skywagon8a]

Granted these are only internet pictures, I have serious reservations about more than just that one bottom cross tube. Where on earth has this fuselage been stored? It looks as though it has been in a salt water sand beach. Look at the bottom of the control torque tube. Whatever caused the cross tube to rust out has clearly effected other tubes as well. At the very least, that fuselage needs a good sandblasting before you start replacing a tube here and there.

 

[Steve Pierce]

Not uncommon in my experience to see this kind of corrosion in an A model. I don't know if the chemicals collected there or what but have repaired a couple of old A models that were the same. Make a small fixture and take lots of detailed measurements before you cut. I have a rear carry-thru tube removed from a damaged fuselage or Univair could maybe sell you one. If you can find some good tubing you could do a tube in a tube or tube over a tube but you might have to go all the way to the cluster.

 

[meinster]

I got a couple bags of garnet blasting media and will start cleaning frame piecemeal and painting with epoxy, but I have already taken my geologist's pick to the frame and haven't found any other major calamities, of course, that's still no assurance.

There was a paste composed of sand, grass, oil and pesticide about 1.5 inches thick built up in that area. Everything else actually looks alright, structurally. Aesthetically there are a bunch of things I should address.

Thanks Steve, I'll check univair, I would prefer to replace as complete assembly if it comes to that, to simplify the orientation for index. So if they don't have a pre-fabricated one, I may take the one you have off your hands. Think of a price ITMT.

As far jigging goes Andrew had some good suggestions for bolt on locations that would alleviate the need to weld anything temporary in place.

Thanks for feedback thus far.

Cheers
Pete

 

[cubpilot2]

I would encourage a complete replacement but that is not an easy tube to change due to the gear/strut fitting mass along with the torque tube supports.

This is an vital structural member and you want it to be "all it can be".

In my early years I was told (by the owner / operator of a large spray business) of an A model cub of his that was a spraying in Texas for cotton defoliation in the late 60s. They were using “arcenic acid” as the chemical, which was highly corrosive, and for whatever reason would often attack the inside of the tubing and not be visible outside.

His pilot was performing a fairly high G pull up over some trees and the tube in question came apart. The wings (as he described it) "slapped together over his ears".

The crossover tube was found to be severely corroded from the inside out.

The lesson learned was that these locations received very special attention during inspections for any signs of corrosion.

 

[meinster]

Good grief!

Last thing I need is wings doing a slow golf clap while I plummet to a grisly end.

If only we had super cub wrecks here in Hawaii, I could scavenge a larger section.

No one happens to have a spare fuselage laying about, do they?

I'll be buggered if there is going to be an easy way of accomplishing this efficiently and easily.

 

[cubpilot2]

The A model may be more prone to this problem then standard cubs in that all of the original A models came standard with the metal belly which didn't became an option for the standard cubs until sometime in the late 70s. The forward panel attached to the flimsy 3/8 inch channel under the crossover tube with a few "riv nuts" installed into the channel.
These riv-nuts didn't last long as the first time you tried to remove a screw they would be so corroded that they would start spinning. People would then start drilling new holes into the channel and use a bunch of small pk screws. This is ok until someone gets carried away with a drill bit and penitrates the crossover tube and thus creating a path for moisture. I have found screws going deep into this tube before....

This is something important to remember for anyone having the forward metal belly installed. Be cautious if drilling and don't use too long of a screw. Just the tip of a sharp screw that is contacting hard to the crossover tube can cause corrosion to start.

 

[meinster]

Well that may have contributed to the current situation, though metal belly had long since been removed, the little gussets/formers that were attached to the crossover tube had accumulated all the gunk I previously mentioned, the corrosion definitely started externally, now that I examine it closer. Metal belly would have facilitated easier access and preventive maintenance to that area.

Then again, it might not have. This aircraft was flying regularly with all the discrepancies I've noted, many not even listed here.

No use crying over spilled milk in this case, just need to do what's necessary to restore it.

It's been a steep learning curve, owning this aircraft, but other than the occasional sinking feeling in my gut, it has been very rewarding and interesting, delving into it head first. Sometimes feels like a treasure hunt, tracking down the necessary data for old STC's and blueprints.

Also got to know some real artisans that embody true journeymen, with a wealth of knowledge and skills that are pretty scarce nowadays. In a situation like this, my A&P certificate means very little, without that kind of experiential knowhow. Hell, if it paid enough to support my family, I'd apprentice to someone with that skill set in a heartbeat.

Regrettably it doesn't. Not in this State at any rate.

I would love to be able to run a perfect TIG bead and to be able to use an English wheel to make compound curves in sheet metal fabrication and have a proper paint booth setup, and have a machine shop that I can use to fabricate bits and pieces, etc etc.

The crown wheel in the Enstrom helicopter main rotor gearbox used to be cut by hand! You need a 5 axis milling machine to accomplish that nowadays. It astounds me how much knowledge and ability has been relegated to history.

Anyways, I digress... Feeling a little down now.