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Spar upgrade

Spar Upgrade(s)

Has anyone completed spar upgrade?

There are various wing upgrades for the RV-3 as seen by the RV-3A I used to own which only had one upgrade accomplished. Mine didn't have the angle aluminum mod to the front spar, which didn't look like it would be that hard to do; but I had no intention of doing aerobatics while I owned it; so I never messed with it. If you do a search of the archives, you will find previous discussions and pictures of others who have already gone down that road.

Doug
RV-9A Mazda 13B/FWF
RV-3A O-290G (innovated, flown and sold)
 
Spar Upgrade Done!

Yes, I have had the spar upgrades done, both CN-1 and CN-2. Keep in mind, EVERY RV-3 is hand made, and not pre-punched. They are all different in some way. In order to complete my spar mods, we had to consult and get approved drawings from Vans, as (go figure) there were some differences in what we found inside my wings when we opened them up.
My plane was built in '84 by a guy who took the initiative and built some strengthening measures into the wings prior to the change notices. My plane is one of the original "Bakersfield RV's" imagined, built, flown and abused by the likes of John Harmon, and my builder Gary Banducci. N66GB was fitted with an O-360 and CS prop and raced at various points in her life, so the measures Gary built in kept it safe all these years, but in order to race at Reno, you have to demonstrate a 4.5 G pull-up, and without the spar mods, these older planes are limited to 4.2 G by Vans. Mine was tested and flown at over 6+ g's so I knew it was safe, but that pesky service bulletin from Vans meant I had to do the changes.

The "parts" amounts to some rivets and screws, and a bunch of angle metal...not much to it. But you have to order "the kits" from Vans, and register as having received them, and then make the required log book entries by qualified person stating that they have been completed in order to return the +6/-3 rating.

Its all in the details. The wings have to come off, which requires disassembly of the whole cockpit, then the wing skins get drilled out and rolled forward to expose the spars. Angle doublers, lightening hole patches, straps and brackets are installed and then you put it back together. It is no small project.

If you want to have it done, you need to find someone to do it...which is the hard part. I have a guy, he is an RV-3 owner and had done it before, so he fixed me up.


Best of luck

Dave
 
Thanks for the info Dave, I?ve decided I?m going to tackle this project myself. This baby will shine and do +6/-3 when I?m done.
 
Have you considered getting the RV-3B wings from Vans?
I think there's even a quick-build option. Then you "only " have to drill out and install the matched bulkheads in the fuselage.
I did the CN-2. Not all that difficult if you don;\'t mind drilling out tons of skin rivets.
Have a real heavy bucking bar to set those 3/16" rivets in close quarters.

Finn
 
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The Cn-2 fix is a lot cheaper only $70 for hardaware kit and only $45,000ish of my labor.
 
CN-2 spar mod

Best of luck. Its not complicated, but does require time and skills. If you find anything that does not match the plans, consult with Vans for sure. I have lots of pictures of mine at various stages if you want to see what you are in for.
Cheers
Dave Cronwall
 
Wing tanks

When we did CN-2, we drilled out and un-skinned the wings from the ailerons up to the spar, all the work is done at the root rib and the back of the spar. So no, you would not be able to do the wing tanks unless you did considerably more deconstruction to the wings.
Dave
 
can CH-2 be done and still accommodate leading edge fuel tanks?

Probably more of an anecdote than helpful information. But because of having the lower inboard skin peeled back for the CN-2 mod, I decided to make truly integral wing tanks. Using epoxy, I closed out the lightening holes in the outside LE ribs with round plates and pop rivets. Then coated the inside of the front bays with "angel hair" fiberglass cloth and epoxy. Installed filler neck, vent line and homemade capacitive fuel sender (tube within tube) from inboard bottom to outboard top). Then closed the lightening holes in the spar web with round plates, epoxy and pop rivets. Finally installed cover/access plates over inboard rib lightening holes. No lower skin stiffeners as the wing tanks were for long range use only -- I would normally only fly with the 25 gal fuselage tank. Months of work. I did get the tanks leak free -- for a while. I guess the repeated heating/cooling by the Florida sun of the epoxy and aluminum caused separation or cracking of the epoxy.

Perhaps would have been more lasting with just proseal -- if possible to get all joints clean enough. And, with help, you could install lower skin stiffeners.

Finn
 
I am in the process now of doing the CN-1 and CN-2 mods to an old RV-3 kit. I would be very interested in seeing any pictures you may still have of your mod. Can they be posted or could you provide a link to where I might see them. Did yours have they Type I spar caps or Type II?

Thanks,

Bob Anderson
 
Spar Mods RV-3

I did complete my spar mods. I have lots of pictures, but would need to compile them in one location and then figure out how to give access to them.
I will see if I can figure something out. Send me a PM and I can discuss.
Dave
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RV-3 Spar Mods

Dave,

Did you have the Type I wings or Type II? Also, did you have to change the configuration on your wing rear spar attachments? Any special technique used for drilling out all of those main spar cap rivets?

Thanks,
Bob
 
My main spar rivets were 1/8".
So didn't require high precision drilling because the new rivets called for are 3/16". (Just ensure adequate edge distance.)

I got a 7.5 pound chunk of tool steel I used as bucking bar. I was able to set the new rivets with my 3x gun.

However, if you anticipate setting the rivets being a problem, you could carefully ream the holes to tight fitting AN3 bolts (NAS if needed). Bolts are allowed per the change notices. Of course they will be heavier than rivets.

I've looked for pictures but it appears the only ones I have are on a VHS cassette (low resolution).

Finn
 
Spar Upgrade

My wings were type I, but the builder made the plane a year or 2 after the first couple failures which were attributed mostly to poor edge distance and builder technique. None the less, the wings were later tested and found to not quite meet the requirement so...the Change Notice.
Anyway, knowing of the failures, some upgrades were incorporated into my build which made it stronger, but did not meet the CN-1/CN-2 explicitly. So we had to work with engineers at the factory to make new details based on what we had. There were some extra straps and things we had to work around.
Now I have CN-1 and CN-2 completed, we did not need to change the spar attach, we had plenty of edge distance and the carry-through met the requirement. Like I said, mine was not typical.
Already mentioned, rivets were not precision drill due to using 3/16 going back in.
Dave
 
RV-3 Spar Mods

Thanks Finnflyer and Dacronwall. The idea for the a heavier bucking bar than normal sounds like a good idea. Did you back rivet the 3/16" rivets or squeeze the gun into the leading edge? Any other advice you think of feel free to pass along.
Thanks again - Bob (Chillibob)
 
If I remember correctly. I rested the bucking bar on a rag or foam on the leading edge skin and had the rivet gun on the rear side of the spar. I may have been resting the gun on something too, to help prevent it from wandering away from the rivet head. I short full trigger bursts too to make sure rivet set didn't wander off of the head.

Oh, and I had the wing positioned at a height so I could stand with arms and hands at maximum strength holding bar and gun. I think working position will be the key to setting the rivets. Do have the trailing skin peeled back enough to give you good access. Drilling out a few extra skin rivet will pay off.

It's very possible you could use a pneumatic rivet squeezer instead. Don't know if Van's still rent them. I think that was my plan B in case I had trouble with using the rivet gun.

Finn
 
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Thanks. That was very helpful. My skins have been drilled but not riveted yet so that should make it a great deal easier. My rear spar attachment was built to the 1984 plans version which is a doubler which puts the attach bolt in double shear but I don't think it gives enough edge distance compared to the current thinking so I am going to replace that as well. Thanks again for the help. This is going to be an interesting project.

Bob
 
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