Gregg Brightwell

Gregg Brightwell

Well Known Member
Ok guys, I remember past discussion on purchasing single piece top skins for the -4. I really like the idea, and am going to go with it. Need advice, warnings, help from those who have done it. Obviously, mistakes would mean replacing an entire skin, vs just inboard or outboard. I haven't gotten too deep into my plans yet, and can't remember, but the bottom skins overlap also right? Might do a one piece on top and bottom....

Who carries these skins, and at what cost?
And besides the obvious cosmetic appeal, do they add much/any strength?

Also going to go with the fastback.... love the look.

Thanks for any help!

Gregg
 
Single piece skins...

I just did a search and found the thread from '08 that discussed the one piece skins. Good info, but was wondering if anyone has recently done this mod, recent quotes for .032'' etc.....

Thanks
 
Sheet Aluminum

Airparts here in KC is $15.75 per foot for 2024-T3 in .032 or $189 for 4'x12':

http://www.airpartsinc.com/products/Aluminum-sheets-2024T3-6061T6-3003-5052.htm

Spruce is cheaper, $158.95 for a 4'x12' sheet:

http://www.aircraftspruce.com/catalog/mepages/alumsheet_2024t3.php

Crating, shipping, etc. can be deal killers and can change the order total in favor of one vendor vs. another. Might be worth a drive to order/pick up at a metal dealer closer to you.

If you decide to order, check into having the material coiled and boxed vs. crated.

Good luck,
Mike
 
Since you are...

...ordering a whole sheet of 2024-T3, it might be worth calling your local metal supplier and seeing if he can get it added to his next shipment...

Ask nicely - in person seems to help - and you can often get the commercial discount....:)
 
single piece skins

Transporter said:
Airparts here in KC is $15.75 per foot for 2024-T3 in .032 or $189 for 4'x12':

http://www.airpartsinc.com/products/Aluminum-sheets-2024T3-6061T6-3003-5052.htm

Spruce is cheaper, $158.95 for a 4'x12' sheet:

http://www.aircraftspruce.com/catalog/mepages/alumsheet_2024t3.php

Crating, shipping, etc. can be deal killers and can change the order total in favor of one vendor vs. another. Might be worth a drive to order/pick up at a metal dealer closer to you.

If you decide to order, check into having the material coiled and boxed vs. crated.

Good luck,
Mike
Click to expand...


Planedriver26 Will a 12 x 5 foot sheet of 2024 t3 32 thou split up the centre work ? IT worked on my rv3. Rivet centre rib on bottom skin first, work out with heaters on 4 foot remaining for a very nice finnish
Cheers
 
Single piece wing skins.

Gregg, Would you mind posting the link to that ‘08 thread on single piece wing skins?

From someone who hasn’t done it, but has an aeronautical engineering background I see it like this:
1. One problem is that each skin needs its own sheet of .032. OK, you’re going to have some sizeable off-cuts, but you will only get one skin out of each sheet. I’ve done the maths on how much this will cost and afterwards I had to have a cup of tea and a lie down…. I mean to sit down sometime with some cardboard and do the same exercise for the two piece skins, but I think you can make use of the material much more economically. 5 ft wide sheets are a new one on me, but then I live at the bottom of the world.…..

2. Unless you’re building a hot-rod RV, the only reason for doing this is appearance. In which case you’d only make the top skins single piece. This helps some with the dollars but does not appeal to my decision making process as you’re putting style ahead of substance. Why?

3. The bottom of the wing is the side of the wing that is in tension. So logically, it is more important to make the bottom skins single piece and leave the top two piece. By eliminating the join and increasing the outboard section of skin’s thickness, on the bottom, theoretically the wing should be a lot stronger.

4. The single piece skin should improve the stiffness of the wing, so if you’re building a hot-rod RV the benefits would be there I would think. How much, is the question though. Can any Rocket guys tell us if this is one of the changes with the Rocket wing?

5. Another consideration is that the .032 would allow machine countersinking meaning you won’t have to dimple at all, as the ribs then don’t need dimpling, but I mention that reluctantly as that comment could well ignite another war.

6. Also there is a weight penalty, but this on the face of it would be negligible, but I haven’t done the numbers. On the other hand, I know light planes are built by worrying about the grams.

My 2 cents worth.

Cheers,
Andrew.
 
Single piece skins...

Andrew.... You are likely not the only reader questioning my logic on going with the single piece skin..... Here are my answers to your questions... ;)

1. a 5' X 12' sheet of .032'' will make a top and bottom skin I believe; thus requiring only 2 sheets. (trust me, I had sticker shock too...)

2. I am really doing this more out of neccessity than 'style before substance'. I purchased a 2nd hand wing kit, and a couple of the wing skins were slightly corroded, and another was damaged badly. (crease) Therefore, I HAVE to buy skins. There is a metal place 3 hours from here that has 5 X 12 sheets that I can go get myself, ergo no shipping $$.

3. I am skinning top AND bottom with the single piece skins. Top for cosmetic purposes, and inverted stuff, and bottom for strength during positive stuff. ;)

skip 4

5. There are two ways to countersink in my opinion..... Dimpling, and .... that other way that I learned back in college in A&P class.....(hint hint) :)

6. The weight penalty, is about 1lb per skin, so 4 lbs. total. ( I think I am pretty close there.)

See, there is a method to my madness... well, at least to me there is... haha

Gregg
 
another thought

I didn't see anyone mention how much harder it is to handle that big piece vs. 2 smaller pieces.

Unless you plan to exceed the design limits of the aircraft adding strength would not be a factor for me.

As far as aerodynamics that tiny overlap would be little concern. Some have joggled to minimize this.

Just my thoughts, when I built my airplane anything I could do without help was a bonus.

Chris M
 
By the way, I don't know how to post the link for the other discussion from '08 on the single piece skin. But if you type ' single piece .032 top skin ' in the search box, it comes up.

I haven't really worried about 'handling' the big skin. I will make sure it has the plastic coating on it, and I will get help. That is a very short-term inconvenience.

As far as added strength, the airplane probably doesn't NEED it, But oh well. Also, even though the ribs are pretty close together, I believe that the .032 skin will also further reduce any 'oil canning' tendencies. Again, merely speculation.....

I am at work, anyone know the actual width of the main skin?

Gregg
 
Single Piece Wing Skins

I did single piece wing skins on my Rocket (for all intent and purpose here same as -4). Handling the skins during drill and dimple was a non-issue. The one issue I watched someone else deal with was during riveting the second skin; with the skin rolled back so you can reach in; as the "roll came nearer to the end the skin has sagged and this left the wing warped just a little. My (successful) solution was to preload the skin up just a bit as we riveted it. The result was that when I released the wing from the fixture it moved less than .020". Let me take another shot at explaining: The wing(s) were fixtured with the leading edge up; trailing edge down. The skin was clecoed on the inboard set of 3 ribs plus the surrounding spars. The skin was then "peeled back" so I could stand in-between and reach for bucking the rivets. If I just let the skin hang down in this peeled back situation it would shift slightly as I worked down the riveting to the outboard end. So to compensate for this I hung a rope from the ceiling and held this "rolled back" skin up slightly. As I worked my way outboard I slowly decreased the amount of upward preload. In the end the holes lined up perfectly and the wing came out straight.
 
I'm with you Gregg.

Your logic is quite easy to follow, not much different than mine. I can drive 10 minutes to a local parts supplier and buy a sheet of .032 for a price that means buying skins from Vans doesn't make a lot of sense. But mainly its that it is just there. Drive 10 mins and load it in the back of the wagon. A lot easier than buying from Oregon! Getting hold of 5ft wide sheets in New Zealand is a bit more problematic. But then, hey, yesterday I didn't know 5ft wide sheets existed!

Cheers,
Andrew.
 
I built a set of non pre-punched RV-6 wings (before we bought our -4) and used .032 single piece skins top and bottom. We bought the aluminum pre-cut, slightly over-sized and it was shipped rolled. I had a local metal shop do the final cutting with a large shear after we carefully measured the wing. We used "nesting dimples" (i.e., a slightly over sized dimple in the sub-structure [ribs and spars]) and high quality Cleveland dimples in the skins. We back riveted the top skin and used the "peel back" method on the bottom. I only installed the outer most wing walk rib and then slipped each rib in and riveted with solid rivets until we got to the root. This way way we were able to use solid shank rivets throughout. The dimples turned out quite well with a finish nearly as good as a machined countersink heads.

Point to ponder: the lower skins were over-kill and probably not worth the extra weight.

Cheers,

Vac
RV-4 N147BR
 
5' X 12' is the way to go!

planedriver26 said:
Andrew.... You are likely not the only reader questioning my logic on going with the single piece skin..... Here are my answers to your questions... ;)

1. a 5' X 12' sheet of .032'' will make a top and bottom skin I believe; thus requiring only 2 sheets. (trust me, I had sticker shock too...)

snipped

Gregg
Click to expand...

I can verify that you will easily get two wing skins from one 5' X 12' piece of 2024-T3. I did this on my RV-8A project when I learned how much "drop" [left over waste aluminum] I would have by using four 4' X 12' pieces.
I did mine years ago, so an actual price quote would be irrelevent now. I can say that buying two 5' X 12' pieces saved me about 30%.
I purchased my 2024-T3 from Future Metals here in the Fort Lauderdale, Florida area. They have 5 locations in the USA, plus International locations. See

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

Charlie Kuss
PS, They applied PVC plastic coating [like the blue plastic Vans applies] to the aluminum at my request. The PVC and local delivery were no extra charge.
 
Single piece skins... 12'?

Guys,

Forgive me if I am missing something here, but all we have been talking about is either 4'X12' pieces, or 5'X12' pieces.....

Looking at the plans, why do I need a 12' piece? Looks like a 10' piece would be plenty long. Am I to take it that 10' pieces are harder to find, or what?

I am excited to build these wings, just facing the challenges of a 2nd hand kit, and deviating from the norm with the one piece skins.

Thanks

Gregg
 
planedriver26 said:
Guys,

Forgive me if I am missing something here, but all we have been talking about is either 4'X12' pieces, or 5'X12' pieces.....

Looking at the plans, why do I need a 12' piece? Looks like a 10' piece would be plenty long. Am I to take it that 10' pieces are harder to find, or what?

I am excited to build these wings, just facing the challenges of a 2nd hand kit, and deviating from the norm with the one piece skins.

Thanks

Gregg
Click to expand...

Greg,
If you can find someone to sell you 10' long 2024-T3, good for you! Traditionally, aluminum is sold in 4', 8' and 12' lengths. 4' wide is the common width, although sometimes you can also find it 5' wide.
Charlie Kuss
 
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