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  #1  
Old 01-03-2010, 11:43 PM
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Ironflight Ironflight is offline
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Default Random Notes on Skinning the RV-3 Fuselage

While we still have quite a ways to go before we have a canoe, the RV-3 taking shape in our hangar/workshop now sports skin (and LOTS of clecos) on everything aft of the F-305 aft cockpit bulkhead! Louise and I finished drilling the second side skin in place this afternoon, and we are quite happy at how well things have gone so far. Our jig has remained straight and true now after close to two months in the Houston atmosphere, and everything looks nice and straight to this point. I always figure that if things are fitting together well (no bunching or gapping, overlaps nice and straight), that?s an indicator that the airframe is coming together with good alignment. We?re going to continue on with fitting the skins for the forward sections using clecos before starting to rivet the aft section ? at least until we run out of clecos! (We?ve already taken on an extra 400 from the Mel and Ann Asberry home for wayward clecos?). Since the instructions for building a -3 are at best described as ?sparse?, here are a few thoughts and techniques we?ve used that worked out fine:

1) Wherever we had a bulkhead and stringer (or longeron) intersection, we drilled and placed a temporary AD3 rivet to allow fitting the skin without a cleco getting in the way, or the skeleton falling apart. Probably obvious to anyone who has built a prehistoric (before pre-punching) kit, but I hadn?t really thought about that problem before. We?ll drill those out and match drill the skins later.
2) The lower aft skin segment took a fair amount of non-intuitive trimming to make the cut-out for the tail wheel mount. Go slow, start small, and plan a couple a couple of work sessions to get it right. It helps to have another (completed) RV tail dragger in the hangar or nearby to look at as you go. Because this is pretty thick skin, cargo straps are really necessary to cinch it down when drilling to the skeleton.
3) Speaking of cargo straps, we used six of them to wrap around the aft section of the fuselage when pulling things together before drilling. I was surprised how easy it is to deform a longeron if you crank them too tight, so go easy. Place them near bulkheads to avoid crushing/deforming the frame.
4) The long lower skin section fit better than I expected, but as others have mentioned before, it is necessary to tilt the lower (upper in the jig) portions of the bulkheads fore and aft a bit to make them really match the contours. The tilt required is surprisingly small, and the cargo straps also help bring the skin to the right contour. Again, you can deform the bulkheads with the straps!
5) I used a long, narrow (3/8?) strip of .016 aluminum leftover from my RV-8 build (was supposed to be used as a backing for wingtip mounting nut-plates) as a rivet layout device. On one side, I marked 1.25? intervals, and on the other side 1? spacing. Once you?ve marked the centerline for the line of rivets, it?s a really fast way to mark out the spacing.
6) We went with Randy Lervold?s idea for rivet spacing on the Longerons. The plans call for AD4 rivets on 2? spacing here, but all later RV?s use AD3?s on 1? centers, and he decided to use the latter spacing and rivet sizes, since it allows less ?pucker? on the edge of the skins, and obviously works fine from a structural standpoint on the later designs. I don?t often make mods to Van?s structural designs, but this one has sound reasoning behind it.
7) After drilling the bottom skins in place, we strapped the port side panel in place, and found that to overlap the edge along the lower stringer; we needed to trim about ?? off the edge parallel to the longeron. Unfortunately, this meant that the jig cross-members where in t eh way for the temporary fitting. We solved this by drawing a line on the outside of the lower skin corresponding to the lower (upper in the jig) edge of the lower stringer, and measuring how much extra overlap there was on the side skin above each cross-member. We then marked that on the longeron edge, removed the skin, and sanded away that amount with a disk sander just where the skin sat on the cross-members. That allowed the skin to sit exactly where we wanted it, and we can go back and trim to the longeron line later (after we flip the canoe, probably).
8) We drilled the side skin to lower skin and lower stringer line from the F-308 bulkhead forward and aft, and let the side skin ?hang? from that line of clecos while drilling the bulkhead lines and then the middle stringer and longeron lines. We were very fortunate to have no bulging or bunching ? it all lay very flat. We drilled everything on the side skins from inside ? putting the drill through the holes in the stringers, bulkheads, and longerons with someone on the outside hold in the skin in place as you drilled by pushing out. The outside person clecoed as the holes appeared. It took us about three hours per side skin this way.
9) It really paid to have two drills and two air hoses when drilling the longerons, stringers, and bulkheads before hanging the skin. We had a real noise festival going for awhile, and the compressor never stopped!
10) I?m guessing we have close to 800 clecos in the structure right now, and will take half of them out to supply the never-ending need for ammunition as we move on to the forward bottom and side skins?..

More updates as we move along. Louise reminds me that we have a couple of remodeling jobs to get done in the house, and balance is the key to a happy universe?.we still hope to get the fuselage out of the jig in as short a time as we can, to preclude warpage ? but again?balance is the key to harmony!

Paul
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  #2  
Old 01-04-2010, 12:34 AM
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az_gila az_gila is offline
 
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.....
1) Wherever we had a bulkhead and stringer (or longeron) intersection, we drilled and placed a temporary AD3 rivet to allow fitting the skin without a cleco getting in the way, or the skeleton falling apart. Probably obvious to anyone who has built a prehistoric (before pre-punching) kit, but I hadn?t really thought about that problem before. We?ll drill those out and match drill the skins later.

You could also make this rivet permanent and adjust the bulkhead and stringer rivet spacing to miss it.

...or you could offset it so a final rivet can be added in the dead center of the stringer/bulkhead intersection.


5) I used a long, narrow (3/8?) strip of .016 aluminum leftover from my RV-8 build (was supposed to be used as a backing for wingtip mounting nut-plates) as a rivet layout device. On one side, I marked 1.25? intervals, and on the other side 1? spacing. Once you?ve marked the centerline for the line of rivets, it?s a really fast way to mark out the spacing.

A cheap flexible metal yard stick from the hardware store is a good substitute, and make a good "fairing test strip" for looking for spots at the previously mentioned bulkhead/longeron/stringer intersections where shims will need to be added.

.......We drilled everything on the side skins from inside ? putting the drill through the holes in the stringers, bulkheads, and longerons with someone on the outside hold in the skin in place as you drilled by pushing out. The outside person clecoed as the holes appeared. It took us about three hours per side skin this way.

This can be a bit easier if the bulkhead and stringer initial holes are drilled #50 and then a #40 or #41 drill is used from the inside to get through both layers.

I presume by now you have discovered how flexible a 12 inch long #40 drill bit is for those hard to reach spots....

...and for those REALLY hard to reach spots a 12 inch #50 drill bit can be used as a back drill, and then a final drill to #41 from outside. The 12 inch #50 drill bit is amazingly flexible.


......
Paul
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  #3  
Old 01-04-2010, 02:01 PM
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Ironflight Ironflight is offline
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Great ideas Gil - thanks! I posted this in the hopes of generating a few comments, as this building from non-punched or trimmed parts is challenging, rewarding - and I am afraid in danger of becoming a lost art! I love the fact that I get to come up with solutions to problems, and sometimes want to hear how others have solved them.

more than ever, i realize that there is still a lot of "art" to this kind of building - some wrong ways to do things, but many right ways - pick one, and move on!

We make extensive use of long bits, but hadn't thought of getting some 50's - I think we'll do that!

I spent an hour staring at the next few skin panels today, and might be ready to start fitting them after some more pondering. It's starting to look like a real airplane part though!

Paul
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RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
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Last edited by Ironflight : 01-05-2010 at 11:04 AM.
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  #4  
Old 01-05-2010, 10:39 AM
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randylervold randylervold is offline
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Quote:
Originally Posted by Ironflight View Post
Great ideas Gil - thanks! I posted this in the hopes of generating a few comments, as this building from non-punched or trimmed parts is challenging, rewarding - and I am afraid in danger of becoming a lost art! I love the fact that I get to come up with solutions to problems, and sometimes want to hear how others have solved them.

more than ever, i realize that there is still a lot of "art" to this kind of building - some wrong ways to do things, but many right ways - pick one, and move on!

We make extensive use of long bits, but hadn't thought of getting some 5-'s - I think we'll do that!

I spent an hour staring at the next few skin panels today, and might be ready to start fitting them after some more pondering. It's starting to look like a real airplane part though!

Paul
Paul,

It is an "art" indeed. As we all know there are those in the world who have "mechanical sense" and those that don't. Doesn't make anyone better or worse, but we all have different skillsets and predispositions. Current generation kits are so sophisticated that even those without mechanical sense can seemingly build them by diligently following the instructions. For the earlier kits there's no question that one needs that mechanical sense to be successful.

Your comment on spending an hour staring at the next few skins struck a chord with me... that is absolutely what it takes to build one of these things... visualize it out ahead of time creatively crafting strategies for building the assemblies. And you're absolutely right, that is a tremendously rewarding experience for the right people -- makes me want to build another one just thinking about it. I remember clearly noodling on various solutions for my canopy retention strut. It literally took me six months to come up with it. I have no idea how many hours I spend staring at it and considering different designs. Finally, the right idea emerged from the fog and voila. Sounds corny but I think that design was my crowning achievement on that plane -- so simple you look at it and think "well of course that's how it should work". (details here if curious)

Enjoy the journey!
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Last edited by randylervold : 01-05-2010 at 10:57 AM.
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  #5  
Old 01-05-2010, 02:26 PM
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Default I just looked at a -3 under construction...

...in Sandersville, Ga. and Ray pointed out how the wing skins are pre-cut at Van's and a tad short....so much so that edge distance from the ends is barely good enough with no room for error. The end rib even shows about 1/32"+ beyond the lower wing skin. Sure is cut close.

Best,
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  #6  
Old 01-08-2010, 10:20 AM
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Ironflight Ironflight is offline
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Default Oh...a Picture to prove it!

Finally remembered to download the shop camera this morning - here's a picture of our little "cleco farm", aft skins in place, ready to move forward!



Paul
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  #7  
Old 01-08-2010, 12:04 PM
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Default Amazing Progress

You are making great progress. Have you tried that little mag kit yet?
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  #8  
Old 01-08-2010, 12:12 PM
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GAHco GAHco is offline
 
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Cool I am real close!

I am real close, I just need to do a bunch of symmetry checks and then throw on the tail skins.

My idea for the junction of the stringer to bulkeads is use a soft bind nutplate rivet that the stem pulls all the way through and that can easily be drilled out accurately from either side.

I will print out and use your tips, I appreciate the shared knowledge.
Its somewhat like instant experience.
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  #9  
Old 01-08-2010, 01:15 PM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by JonJay View Post
You are making great progress. Have you tried that little mag kit yet?
Haven't had the need yet, but I can see it coming on some of the forward stuff!

Paul
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Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
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Old 01-08-2010, 01:18 PM
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A cold chill went up my spine when I saw all of those holes that need de-burring and blue plastic that needs removing! It looking great so far.
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