M

Millionrivets

Member
I've heard of this, but know little about it. I'm getting ready to skin the wings, and thought I'd look into the single piece .032 top skin idea. Buying a sheet of aluminum and coming up with the hole pattern doesn't sound too difficult. What about matching it up with the .025 leading edge skin? Anything else? I'm not building a show plane, just think this sounds like a good idea. Worth the trouble?

Thanks,
Chris
 
An old mod...

...that was favored by many of the early "hired gun" builders of RV-6s and -4s - the guys in Chino, CA and Avra Valley, AZ come to mind. By not ordering the top skins with the kit, it was a very minor cost delta, and you do end up with a "smooth looking" wing surface.

The most inconvenient part is transporting and handling the long skin.

Of course, the early kits were not pre-punched, so all of the hole locations had to be marked - it was all blank sheets of aluminum. With the later matched hole kits, you could use the two top skins as templates as mentioned above, but then you will have paid (many $$$) for a lot of square feet of skin that you won't use...:(

If you do this, it would be better to borrow some raw kit skins from another builder and use them as templates...:)
 
az_gila said:
...t
With the later matched hole kits, you could use the two top skins as templates as mentioned above, but then you will have paid (many $$$) for a lot of square feet of skin that you won't use...:(

I:)
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Gil,

Since the ribs are punched I would think you could get away with using the skeleton as the template. Of course the wing would have to be jigged just like in the old days to make this work.
 
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OK...

zilik said:
Gil,

Since the ribs are punched I would think you could get away with using the skeleton as the template. Of course the wing would have to be jigged just like in the old days to make this work.
Click to expand...

Gary... that would work...

...but a few issues come to mind...

1. The need for jigging - is that as well defined for the matched hole kits as the early kits?

2. The difficulty of transferring holes from the "inside" of the wing. This would have to be done with the bottom skins off, and there still would not really be a straight shot for a transfer punch or long drill... a good angle drill might work though.

3. With the bottom skin off, you would loose the "straightness" of each rib as you transfer the holes, and stand a really good change of getting curved rivet lines along the ribs. Since this whole change is to make the top surface look better, a non-straight rivet line would look bad...:rolleyes:

Item 1 is probably easy to overcome, but to keep the major advantages of the newer kits (no jigs and pre-defined straight rivet lines), using kit skins as templates would be better.
 
az_gila said:
...The most inconvenient part is transporting and handling the long skin.
Click to expand...
Two sheets of 144" X 48" X 0.032" from Spruce came in a box that was about 12" X 12" X 50". The good new is that they can ship up to 0.032" -maybe up to 0.040"- rolled.
 
That takes care...

w1curtis said:
Two sheets of 144" X 48" X 0.032" from Spruce came in a box that was about 12" X 12" X 50". The good new is that they can ship up to 0.032" -maybe up to 0.040"- rolled.
Click to expand...

...of the transporting issue... good to know...:)

The handling issue I mentioned was the in process working stuff of picking it up and placing it on and off the wing... the original skins are floppy enough, a 10 ft odd long skin will be a lot worse...

The sheet you mention is $185 each side for 2024-T3 at 0.032 thick.

William's method of using the Vans skins as templates seems to be the easiest and most accurate.
 
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All points well taken

az_gila said:
Gary... that would work...

...but a few issues come to mind...

1. The need for jigging - is that as well defined for the matched hole kits as the early kits?

2. The difficulty of transferring holes from the "inside" of the wing. This would have to be done with the bottom skins off, and there still would not really be a straight shot for a transfer punch or long drill... a good angle drill might work though.

3. With the bottom skin off, you would loose the "straightness" of each rib as you transfer the holes, and stand a really good change of getting curved rivet lines along the ribs. Since this whole change is to make the top surface look better, a non-straight rivet line would look bad...:rolleyes:

Item 1 is probably easy to overcome, but to keep the major advantages of the newer kits (no jigs and pre-defined straight rivet lines), using kit skins as templates would be better.
Click to expand...

Me thinks your right Gil. Beg, borrowing or stealing a local builders top skins as a template makes for the best option. I helped re-skin a Cessna's wings once and it only took a couple of hours to match drill both top skins. Mind you there are much fewer ribs in a 172's wing.
 
Buying large aluminum sheets for 1 piece Wing Skins

Millionrivets said:
I've heard of this, but know little about it. I'm getting ready to skin the wings, and thought I'd look into the single piece .032 top skin idea. Buying a sheet of aluminum and coming up with the hole pattern doesn't sound too difficult. What about matching it up with the .025 leading edge skin? Anything else? I'm not building a show plane, just think this sounds like a good idea. Worth the trouble?

Thanks,
Chris
Click to expand...

Chris,
One piece main wing skins started with the "Bakersfield Bunch". You can buy one piece non prepunched wing skins cut to size from Vans. I called Vans many years ago inquiring about getting prepunched one piece skins for my RV-8A project. I was told it was not available, so I made my own (top and bottom). About a year later, another local 8 builder received a set of one piece, prepunched skins from Vans. I asked him how he got them. He told me that during his first call to Vans, they denied that they were available. He simply made a pest of himself with repeated calls. Finally they told him that it would require a several months wait. He said OK, and got them with his wing kit several months later.
If you go the "make it yourself" route, look for an aluminum supplier who can supply you with a 5' X 12' sheet. While 4'X12' is more common, 5'X12' IS available. At the time I made my purchase, Vans wanted $144 for each 4'X12' sheet (4 required for both top and bottom main skins). I called a number of vendors.
While everyone had only good things to say about AirParts, and their shipping costs are very low compared to Van's (hey, I live in South Florida- not exactly around the corner from Oregon) I continued to look for a lower cost option. (Bear in mind these price quotes are years old)
Airparts quoted me $484 plus about $40 shipping to send me 37 running feet ( 4' wide) of .032" 2024-T3-QQA-250/5 alclad aluminium rolled sheet. I had called at least 15 aircraft aluminium suppliers in 5 states over 2 or 3 days. RV-4 builder (and Beechcraft A&P, IA) Jody Edwards suggested I contact Future Metals in Tamerac, Florida. They are local to me and are the main supplier of Raytheon (Beechcraft) Ft. Lauderdale. Future Metals has locations worldwide. See

http://www.futuremetals.com/locations.html

Lee Green, their salesman suggested using 60" X 144" (5'X12') sheets. This allowed me to obtain 2 wing skins out of 1 piece of material. He quoted me $203 per sheet of the above mentioned aluminium complete with PVC (plastic) coating, just like Van's sends out. I liked this option better for 3 reasons:
1) Lowest cost---- Cheaper than Van's ($140 per skin plus crating and shipping)
2) They are local to me ---- shorter wait and delivery included
3) I didn't trust myself not to scratch the non-coated Airparts Inc. rolled sheet.
I made all 4 main skins one piece units. This represented a considerable savings of money and time for me. Future Metals 2 5'X12' pieces = $406 with PVC coating approx. 28 sq. ft. of excess material
Van's Aircraft 4 4'X12' pieces = $560 plus ~$150 crating and shipping to me....with PVC coating, skins cut to size but not prepunched (no access panel cutouts either) plus 144 sq. ft. of excess material (Van gives you the leftover material from the 4'X12' sheets)
Airparts Inc. 37 running feet (37'X4') = $484 plus ~$40 shipping to me No PVC coating 56 sq. ft. of excess for 4 skins.
Local fabricator and EAA Chapter 133 member Ed Heishmann told me to really do my homework regarding this purchase. He said that I would find that most of the local suppliers were really buying their material from one or two main local suppliers. He was TOTALLY correct. My advice to anyone contemplating a large aluminium purchase, ask your large, local FBOs who they purchase their metals from. Don't settle for 2-3 quotes, do your homework. ;)
I love the way my wings turned out. It adds 1 pound per one piece skin to the wing weight however. Lots of guys do only the upper skin for cosmetic reasons. The thicker top skin only adds strengh (a small amount) in the negative G realm. The one piece skins eliminate that "starving Ethiopian" look of the outer skins. If you don't know what I'm talking about, check out any stock RV. Squat down by the wing tip. Sight down the wing (toward the wing root) with your eye close to the surface of the wing. You will notice that the .025" outer skin "sags" between the ribs. This doesn't happen with the .032" skins.
Charlie Kuss
 
Thanks for the great info, Charlie. In fact a Future Metals is just down the street from me, and they were very helpful, and indeed stock the 60"x10' sheets as a special size just for Boeing. However, it's now $385/sheet. Shopping around, so far it seems that this stuff is 'spensive these days, probably more than I'd want to pay. And the prices seems to jump when you go over 8 footers.

Here's the story on the RV-4, for those that would be interested. There are no matched holes, with the exception of the ailerons, which apparently come from the -7/-8 kits--at least that's what the drawing indicates. Boy, I sure like matched holes, especially after building the tail... Wing skins do come pre-punched (but not the ribs) these days (from the old RV-6 QB tooling, I assume?), which is both a blessing and a curse, as you have to line up the holes with the ribs, and on the Phlogy spars the pre-drilled reinforcement angle holes seem to be slighly off, so your ribs go where they have to go, and you lines up the skins best you can. Fabbing single peice skins would actually be easier, in that sense, because you could just custom your rivet lines to the ribs. You'd have to weigh that against the time savings of templating the holes with the stock skins.

One of the primary reasons the hired guns used .032 skins--according to a builder friend of mine--was that they could countersink the entire skin, and this saved a bunch of time (i.e. not having to dimple the ribs, etc.) banging out an airframe. Other than that, as has already been mentioned in other posts, it's mostly just costmetic.

If I add it all up, my conclusion is that I would probably do this if I built another airplane and could subtract the stock skins from my kit order. Design-wise it makes a lot more sense to me to slap one single skin on there, both on the top and bottom. Having a splice seam for no real design purpose that I can see, but because it was easier to ship two smaller skins (as I understand it), makes the lurking engineer mentality inside me squirm a little, but I can live with it.

Dang excited to be putting these skins on. Thanks for everybod's input.

Chris
RV-4
 
.032 skins

I did it on my -4, and several other local builders did it on -6's. Ordered wing kits without the 2 piece skins and locally purchased the 12' sheets of 2024-T3 clad .032. I dont recall the cost, but seems it was about 125.00 each..was a few years ago. I am in the aviation business, so our shop has a 20' shear, and making the cuts to size was easy, however the big metal distributors often will cut to size for you if you ask. Wasnt bad working with the big piece, and it looks great.I had no prepunched kit, so I backdrilled all mine through the ribs...no big deal if you have a 12" drillbit. Good luck!

Bill E.
RV-4 painting.
 
More reasons than convenience.

Millionrivets said:
Having a splice seam for no real design purpose that I can see, but because it was easier to ship two smaller skins (as I understand it), makes the lurking engineer mentality inside me squirm a little, but I can live with it.
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Reasons for using 2 skin thicknesses; in a stressed skin design, the loads are less as you move outboard. Therefore the outboard skins can be thinner reducing weight and cost. If you look at a Mooney wing for example, the skins are .050, .040, .032 and .025 from root to tip.
 
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