RV-4 restoration : replacing the tanks, two times

RV-4 restoration : replacing tanks, two times

This is the story of an old RV-4 #1504. This RV was well-built in USA in 2001 (N90402), probably she did an heavy life and the worst fact is a wing-tail dismantle for overseas shipping to Europe (Germany) where she was bought from a friend of mine under Holland registration.





To become a legal italian Experimental aircraft their (buyer and plane) need to spend some time to restore in physical (plane) and mind (Experimental plane buyer here have to prove to our FAA official that he has the acknowledge to built an airplane); in this process I have an official role as DAR&Tech Couselor so I have a story that I like to share.

The plane was unpainted, metal surfaces worn but regular in shape, control tubes were loose, electrical system was ?low?, and tanks were leaking.

The tanks were adjusted (in Germany) in some manner just to sell the aircraft? so Enrico (the name of the buyer) had a problem : building new tanks.

First mistake :

Simply filling an order list of all the tanks parts coming from the preview dwg (the original drawing were missed) and building a couple of brand new tanks was not a good idea : Enrico did that without knowing that there are 3 different generations of RV-4 tanks (I didn?t know it too). It is important to get the appropriate parts as the tanks are not interchangable. When the tanks were finished and tested they were ? too short in depth (front/rear)!

After a call to my friend Gus @ MotherShip (april, 2015) we understood the problem and there was no other option than rebuilding another two tanks with an oversized skin to match the original length of the first generation RV-4 ribs.
Enrico was exhausted with his building tanks process so he chose to call Evan Johnson from Evan?s Aviation Products. All the right stuff were shipped to Evan with the oversized skins too.

Second mistake :

Last week, yes in december-2015, Enrico received the tanks built with an outstanding workmanship from Evan but they were ? too short in width (fuse/tip) side; unfortunately Evan trimmed the skin too much. [bad words here]

I?ll meet Enrico next Tuesday (yes we?ll spend all day in hangar) to try to solve the problem (side screws edge distance) ? probably we?ll change the W-423 JOINT PLATE to obtain a right edge distance.

I?ll keep you updated : stay tuned !

PS: Enrico is selling a couple of brand new RV-4 tanks, last generation, leak tested

Tanks a lot

Wow Luke, that kind of thing can really rain on your parade. After this you and Enrico will be the go to guys in Europe, and I'm sure that is what you want. This is a good reminder for us all that we need to measure twice and cut once, but there comes a time in every mans life when you have to take the bull by the tail and face the situation.
Keep us posted, wish I could help. Send me a round trip ticket to Italy and I will build them for free!!.

I would suggest that if another set of tanks need to be built you should have the mechanics follow the builders manual when constructing them. This would involve using the current wing as the fixture for locating / positioning of all the fuel tanks components, since the RV-4 tank skins and ribs are pre "matched-hole" and as you have already found out pretty much impossible to build otherwise. I have never attempted to build the tanks on the wing when installed on the aircraft and I'm sure that will present some challenges versus with the wing setting vertical in the original jig.

update of restoration

The problem is always there, you have to match two pieces of aluminium and two holes with their edge-distance. Mr. Evan built two perfect and beauty tanks but, unfortunately, he trimmed the outer (tip) side too short to match a flying 2001 rv-4 wing.



On the airplane there were a W-423 joint plate with the originals nutplates that not gave to the brand new tank skin T-401 the proper screws edge distance.

Another problem were the fact that the tank end rib T-403 was places too external (just a little) so it bumped the joint plate itself.

After removing the excess of proseal that protrude from T-403, we were ready to remove the joint plate to restore the edge distance



note : the old original italian AF flying suite is a courtesy of Franz - my leader (in soul) and wingman (in practical formation flying)

Scared about the next step, tons of measurements to check the doable things, we rebuilt another joint plate a little bit narrow to leave the tank rib reaching its natural position.



Then we put the tank on



check, double check, triple check ..... you can see two lines on the tank 1,5 to 2 edge distance in respect to the hidden joint plate.

Yes, we were ready to drill :



voilà, with a really thin edge distance we are able to take a breath and enjoy the task, you know what I mean



Right tank has a little bit more skin on the tip side, we'll change the joint plate but we'll be more relaxed in edge distance.

Lessons learned :

1 : matched drill kits are another thing

2 : Murphy's law is always there, especially if you don't work yourself

3 : when Vans Aircraft sells an oversized skin there is always a reason