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Old 09-17-2016, 08:01 PM
xti xti is offline
Join Date: Apr 2016
Location: WA
Posts: 5
Default New RV-4 Build; Ancient but Gotta Be Done.

Hi All,
A few months ago I acquired a '93 RV-4 in several boxes and have some questions.

The only thing on the plane assembled so far is the tail pieces by previous owner. Just the skins and the horizontal stabilizer is a L and R but not tied together. Also 'Factory' solid wing spars came with it.

As I understand from reading, it seems I should be doing the wings first.

Is it safe from a gross weight standpoint (I don't know the weight and balance) to try to add about 10 gallons of gas to each wing?

My thought is to add a wing rib with lightning holes and a second pick-up where the outboard tank wall is supposed to be to maintain wing structure at that station, and then put the outboard tank wall outboard of that by about 8" to get that extra few gallons of gas? I realize Experimental means I can do anything I want, but I'm not interested in going too far outside the box.

Any thoughts would be greatly appreciated, thanks in advance.

rv4 '93 build in progress

Last edited by xti : 09-18-2016 at 12:21 AM.
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Old 09-18-2016, 06:26 AM
Michael Henning Michael Henning is offline
Join Date: Jun 2011
Location: Nashua, NH
Posts: 451

Hi Travis,
I built my -4, and if I had to do it over again, I would use RV-6 fuel tanks. The cg, and extra weight won't be an issue, as you can adjust your fuel load based on your mission requirements. Get to building, it is an incredible machine.
My mods are-
Moved roll bar back two inches (6'2", 245 pounds, and I fit perfectly)
Removed an inch from bottom of instrument panel
Two RV-10 vents installed
Todds canopy
Wing tip lockers as shown in RVator
RV-4 #2750
WW150C Prop
1018 lbs

Last edited by Michael Henning : 09-18-2016 at 11:06 AM.
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Old 09-18-2016, 06:51 AM
fixnflyguy fixnflyguy is online now
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 857
Default A few things to keep in mind..

You have a great start and will love the -4. I built mine , S/N 2667, a late 80's tail kit and bought my wing and fuselage kits around '93. I have never heard of a "Factory Solid Spar". I built my spar , which is a build up of many components to a very robust design. Vans advertised the "factory spars" as an option which are actually just kit spars sent to a vendor (Phlogiston) whom assembled it. they are easily identified by their gold anodizing. The wing spars are fit and drilled with a matched set of steel splice plates as well as the center fuselage bulkhead, which is why building the wings before the fuselage is pretty much mandatory. Make sure you have all the matching parts. Going forward , if you dont have the finish kit, you will get the new style longeron wedments , long gear and epoxy cowl, wheel pants and fairings. As Michael said,and I also did, move roll bar back( determines pilot seat back position), trim panel bottom. I am 6'1", and I fit fine. The extra fuel of the -6 tanks , I would also do in hind sight, but my missions are usually less than 2 hrs, so the stock 32 gallons is fine for me...Now get building!
Bill E.
41 Aeronca 65TC Defender
8A7 / Advance NC
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Old 09-18-2016, 02:02 PM
philcam's Avatar
philcam philcam is offline
Join Date: Aug 2005
Location: DFW, Texas
Posts: 195

Hotel Whiskey aviation makes extended range tanks that fit in the lightening holes.
Phil Campbell
VAF # 1043
Builder # 82699
RV-8 Builder, ex-Grumman AA1B owner
DFW Metromess
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Old 09-18-2016, 03:13 PM
WAM120RV WAM120RV is offline
Join Date: Dec 2006
Location: Coventry. England
Posts: 592
Default Baffle


It is possible to do this, as they say there is more than one way to skin a cat..

Just extending the tank to a six tank is problematic because you have the phlosigon spar and the web that attaches the tank is already fitted. That limits the tank width.

In the UK max all up weight is limited to 1550lbs. I know you can set your own in the states but Van is against this. The thing that limits the 4 is that all up weight. Adding 70lbs of fuel limits passenger load by that amount. Most 4s are between 950 and 1050 lbs depending on what instruments engine and prop are fitted.

So I would think carefully before adding more weight.

Steve Arnold

In completion stage of Loehle P5151
Built and now Flying G.BVLR Vans RV4
Rebuilt G.BDBD Tailwind
Rebuilt G BVTN Kitfox
Built G CDCD RV9A with WAM120
Riveted wings on Glastar G.LEZZ Now (G. SKUA)
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Old 09-18-2016, 03:19 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 3,336

The separate horizontal stabilizer halves might be an issue. The HS-409 spar bars get riveted to the spar webs across the joint between them and tie them together in the back, but they extend outboard too.

It might be hard to rivet them to the webs if the skins are already on.

If you meant the elevator halves then it's okay.

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Old 10-16-2016, 01:42 PM
xti xti is offline
Join Date: Apr 2016
Location: WA
Posts: 5
Default Step one (for this rv-4)

Thanks for the thoughts guys. Fate had it that a guy came by the shop on other business last week who happened to have RV building experience. Thanks to him I have direction now on 'what to do first' so; since the previous owners did the tail feathers I am undergoing a steep learning curve on the wings.

1. fluting pliers to make all ribs flat
2. line up ribs at right angle to spar
3. study/learn how to drill and debur holes
4. decide on gas tank plan

Now I'm looking to trade some of my scrap boat aluminum for an Avery tool kit. Boat aluminum is 5052H32, and extrusions are 6061T6. Channel, sched 40 pipe, flat bar, angle, and some 1"x1" square tube with .125 wall.

ps. I just read the directions on how to attach pictures to posts. Doesn't seem to work. Any tricks?
rv4 '93 build in progress
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Old 10-16-2016, 02:13 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 3,336

Van's practice kit for the toolbox might be a handy thing to try first. Also helpful for me was to make a channel of aluminum (or find a likely-looking channel like part in the kit, buy another, and use that) and rivet cap strips to the flanges. Lots of drilling, deburring and dimpling practice that way.

My philosophy is to first try to do something on a part or scrap that's not intended for the plane. I wreck enough airplane parts as it is.

RV-3B, now on the fuselage.
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Old 10-16-2016, 02:15 PM
xti xti is offline
Join Date: Apr 2016
Location: WA
Posts: 5

Links to pictures:

rv4 '93 build in progress
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Old 10-16-2016, 02:36 PM
az_gila's Avatar
az_gila az_gila is offline
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,084

That's the Pholgiston (factory) wing spar, and the tail section pieces look normal...
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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