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Jigging the wing

NorthernRV4

Well Known Member
At the point of drilling the alignment holes in the main/aft spar to get everything squared up. Wondering if anyone has some tips on fitting the main wing skins. Van's instructions say to fit the main wing skins first, then the leading edge skin. I've read another builder's site who fit the bottom main, leading edge, tank and then the top main skins in that order. I can understand the key here is getting everything lined up and gaps fit closely. I will have to flip the wing to the other side of my jig to skin the bottom (or top if I start opposite) so that means setting it up twice, although the second time should prove a little easier once the main skins on one side have been drilled/cleco'd.

Suggestions?

Wing jigging by James Soutar, on Flickr
 
I followed Van's directions and all wing skins went on fine. I do not understand why you state that you need to flip the wing over to get to the "other" side.
 
Don't flip it if you can avoid it. Taking it on and off the jig has the potential of introducing a twist or misalignment. If you must, I would make sure you have the skinned side cleko'd very well, but it will still want to twist.
I followed plans as well as far as sequence.
 
When you transfer dimensions from the jigged wing frame to the skins, don't rely on a tape measure - too many differing fractions involved...:)

Get some long thin strips of aluminum and use them as storey poles...

https://en.wikipedia.org/wiki/Storey_pole

It will be a more accurate and quicker transfer of dimensions.
 
The only reason I'd have to flip the wing around is to get at the other side if both wings are in the jig at the same time. My jig consists of two vertical posts, each with a horizontal arm extending out 12". So with both wings in the jig I'd not be able to get in the middle and even with one, the jig cross member that ties the posts together is a bit in the way. It's workable with one wing at a time and maybe I'll just skin one at a time so I don't have to move anything. I agree that I'd have to be very careful not to introduce any twists if I did move it.

So the "Storey Pole" method, do you use that vertically to position each hole or horizontally to locate the stations of each rib under the skin? So many ways to skin a cat ;-)
 
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So the "Storey Pole" method, do you use that vertically to position each hole or horizontally to locate the stations of each rib under the skin? So many ways to skin a cat ;-)

I used both.

Pick a good reference at each end - preferable attached to your vertical support - and work across marking the center line of each rib. Make one for each end of the ribs in case you have minor errors in the locations at the two spars.

I made a separate one for the rib rivet spacing that can be used for each rib, but this was actually more useful for working out the crimp locations.

If you get the rib spacing marked on the skins at end ribs of each skin you can use a long straight edge to mark the rivet location on the intermediate ribs. I then drilled the skin rivet locations undersize and match drilled into the ribs. A wide sharpie marked the flange center line and was a good reference to ensure the holes hit the rib flange correctly.
 
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Fuel tanks

Jim

You are at the perfect time in your build to consider increasing your fuel capacity.
The RV-4 has only 32 US gallons, which is the lowest of all Van's series ( except the 3).

If you are planning cross country flying, which these planes are great for, you will find you wish you had more fuel capacity.

It is quite easy, at this stage in your build, to add larger tanks.

John Harmon sells a 54 gallon tank kit for his HR 2 for $665. It uses the same wing as the RV-4.

Although I have two Harmon Rockets, I don't receive any benefit from mentioning his products.

Look into this option, especially if your considering a 180 HP engine.

Enjoy the build.

Carr
 
Jim

You are at the perfect time in your build to consider increasing your fuel capacity.
The RV-4 has only 32 US gallons, which is the lowest of all Van's series ( except the 3).

If you are planning cross country flying, which these planes are great for, you will find you wish you had more fuel capacity.

It is quite easy, at this stage in your build, to add larger tanks.

John Harmon sells a 54 gallon tank kit for his HR 2 for $665. It uses the same wing as the RV-4.

Although I have two Harmon Rockets, I don't receive any benefit from mentioning his products.

Look into this option, especially if your considering a 180 HP engine.

Enjoy the build.

Carr

Thanks Carr, from my understanding of the Harmon tanks I'd have to have built the spar with a longer spar web doubler. Since I have the prebuilt Phlogiston spars that doubler is already riveted in place and set up for the standard -4 tanks. Actually I would have liked to build in more capacity but drilling out the 3/16" rivets and modifying the spar was just too much for a first build effort.

If I decide I want more capacity I might look for a set of SafeAir1 ER tanks but the mission for this plane is not long cross country so 3hrs will likely be all I need.
 
Looking for some tips on adjusting rivet spacing or more accurately, modifying standard spacing to accommodate underlying structure.

The plans indicate the forward edge of the main skin where the skin is riveted to the main spar to be spaced at 7/8" but this doesn't put the rivet on the rib C/L or sometimes two rivets straddle a rib station. This means I either have to modify the spacing (closer together, never further apart) to get the rivets to land on the rib C/L at each station or to not worry about putting a rivet where the rib flange underlaps the spar flange. Obviously I don't want to create an edge distance issue and the plans don't really indicate if a rivet must land on the C/L of each rib along both the main/aft spar line.

The simplest solution is to space at 7/8" and move any rivets that interfere with a rib flange to either be on center or miss the rib completely. sometimes the spacing might be as little as 1/4" then pickup again with the 7/8" spacing until I get to the next rib and adjust accordingly.

I can also evenly space the required number of rivets between each rib station using a rivet fan. So for example, two ribs are 10" apart, 10/.875= 11.42 rounding up to 12 rivets evenly spaced and let the fan do the dividing and work my way station by station.

I'm sure there are other good methods and I want to make sure I'm doing it the correct and easiest way.
 
Adjusting spacing "tool"

As well as a "rivet fan" mentioned in the thread, I use an old favorite us old school repair guys have used for years when you want perfect spacing that you dont have to calculate. I have a 3' piece of 1/2" wide elastic band for clothing makers, and while in the unstretched condition, I marked it in 1/4" increments similar to a tape measure rule. When you have a line of rivets to lay-out, simply tape it next to your starting point, and pull it to the finish point, creating equal spaces if you get the picture. Most spacing is 1/2", 3/4", or 1" specified, but minor deviation plus or minus .
 
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