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-   -   Folding Wing RV-4 (https://vansairforce.net/community/showthread.php?t=81903)

WingsOnWheels 01-27-2012 10:26 PM

Folding Wing RV-4
 
I just saw this on Barnstormers. Has anyone seen this plane in person, I wonder what mods were done to work this out. Reminds me of the Mustang II.


panhandler1956 01-28-2012 06:12 AM

interesting
 
Wow, that is interesting. I hope whoever did this has some engineering and test flying background - in my mind that is a pretty substantial modification/deviation from the plans.

It is cool though...

Nihon_Ni 01-28-2012 06:43 AM

I saw that too and had the exact same thoughts.

LAMPSguy 01-28-2012 07:13 AM

"just"
 
Wouldn't you "just" have to make the break in the spar stronger than the original? In college we had a lab where we had to redesign the wing attach bolts for a T-34 and perform testing in the lab to prove it...my group used, and PROVED that you could make zip ties work for up to utility category strength! :eek:

pierre smith 01-28-2012 08:46 AM

Wow.
 
Bet it has to go back into 'Phase One.' :D

Best,

edbooth 01-28-2012 08:49 AM

wing attach
 
Quote:

Originally Posted by LAMPSguy (Post 622680)
In college we had a lab where we had to redesign the wing attach bolts for a T-34 and perform testing in the lab to prove it...my group used, and PROVED that you could make zip ties work for up to utility category strength! :eek:

How many zip ties did you have to use and what size and quality ???

Ed Booth, Trenton, SC

FresnoR 01-28-2012 10:31 AM

That is soooooo cool. I wish we could convince vans to come out with this mod. You could fit 3-4 rvs in one hangar. It would look like an old aircraft carrier.

Of course I would only trust vans to come out with it. Or maybe a bunch of people with a bunch of testing hours. That guy has a lot of guts.

So cool

frankh 01-28-2012 11:23 AM

Better use certified zip ties for this though eh?

gasman 01-28-2012 11:35 AM

Just doesn't look like it will fit back into that hangar.

Mike S 01-28-2012 11:45 AM

This plane should be done in a Navy paint scheme.

WAM120RV 01-28-2012 12:32 PM

Odd!
 
I wonder if its still aerobatic?

Also there is something odd in the rear canopy.

Do you have a link for where this is, I could not find it on BStormers.

RV8R999 01-28-2012 12:48 PM

Did he split the flap as well or does the -4 flap stop short of the ailerons where he folds the wing? What about the fuel tank?

Snowflake 01-28-2012 01:03 PM

Quote:

Originally Posted by gasman (Post 622751)
Just doesn't look like it will fit back into that hangar.

That was my first thought too.

Wing folding mechanisms aren't really all that difficult... They do always add weight, though.

Here's the link to the ad, with more photos.

Look like the owner has used Sika or Proseal to bond in a plexi panel behind the passenger's head... Maybe stopping drafts?

WingsOnWheels 01-29-2012 12:05 AM

It would be great if Vans could off a mod to make the RV with folding wings like the Mustang II. I like the RV better, but the folding wings on the mustange are very cool.

newt 01-29-2012 01:09 AM

Only one wing?
 
The photo that's shot from the front shows that the flap on the folded wing is shorter than the one on the other wing.

I wonder if both wings fold, or only the port-side wing?

I also wonder if it has flown since the folding mod was performed. :D

- mark

PIN 37 01-29-2012 01:23 AM

It looks to me like only one wing folds and the flaps are definitely split, an unfinished project maybe, maybe the design intention was for both wings to fold but something interupted the project.:confused:

NickAir 01-29-2012 02:49 AM

The cool factor is high on folding wings. As with it all there will be a trade off.

Extra weight, out bound on wings.

My first thoughts: RV4 folding wings?? It only has a 23' wingspan! Why fold them?

Fun to see the photo. Very cool.

ccsmith51 01-29-2012 05:07 AM

It looks to me like both wings might fold. From the front photo you can see that there is a break in the right flap at the same station as the break in the left flap. There also appears to be some kind of a seam in the underside of the wing at that same station. On the other hand, I don't see any seam in the leading edge...

plehrke 01-29-2012 05:19 AM

Quote:

Originally Posted by gasman (Post 622751)
Just doesn't look like it will fit back into that hangar.

It would not help fit it in very many hangers I know (and especially in my hanger). Would only help in hangers with all low wing aircraft. Mine has 2 high wing airplanes so the low wing RVs fit under them.

In my opinion, no way does the precieved "cool factor" ever buy its way on an airplane espeicially for something already as cool as and RV but i do love the rules in E-AB that let people try these kind of things. Makes going to OSH fun to see what others have tried (do not get to see much at OSH what others have failed trying)

szicree 01-29-2012 09:25 AM

Deja Vu
 
This same aircraft was discussed on VAF several years ago:

http://www.vansairforce.com/communit...ing+wings+rv-4

NickAir 01-30-2012 03:44 PM

Quote:

Originally Posted by plehrke (Post 623046)
In my opinion, no way does the precieved "cool factor" ever buy its way on an airplane espeicially for something already as cool as and RV but i do love the rules in E-AB that let people try these kind of things. Makes going to OSH fun to see what others have tried (do not get to see much at OSH what others have failed trying)

The Cool Factor is added to aircraft for mission specific use in the military. It sometimes takes an unlimited check book, (Gov,) to accomplish the Cool Factor.

N941WR 01-30-2012 04:19 PM

Quote:

Originally Posted by WAM120RV (Post 622761)
I wonder if its still aerobatic?...

Good question. The folding Mustang II referenced in some of these posts is not aerobatic.

Although I couldn't find it on their site, one of our chapter members is building one and he said that was the only drawback to the folding option.

SHIPCHIEF 01-30-2012 04:39 PM

I wonder if that's true, or if it's "Common Knowledge"?
The final Thorp T-18 model, the S-18, is folding wing, and the aerobatic gross weight is 1500 pounds. The 'older' T-18 aerobatic gross weight is 1250 lbs.
The folding mechanism is said to be the same for the S-18 and the Mustang II.
I just flew out with the wife to look at an S-18 folder, on a trailer in a garage.
It was a great day trip with wonderful flying, and also wonderful new people to meet.
The aircraft in question is not a flier, more of a restoration project. but the folding wing mechanism was out in the open for easy viewing. I'd say it's pretty straight forward, and similarly strong.

N941WR 01-30-2012 05:21 PM

Quote:

Originally Posted by SHIPCHIEF (Post 623812)
I wonder if that's true, or if it's "Common Knowledge"?...

I've got to go with what the builder told me and the Mustang web site.
Quote:

Originally Posted by M-II FAQs
Does the Folding Wing Make It Weaker?

The folding wing modifications for the Mustang II do not change the main wing spar. Ultimate G loading is therefore not changed. The only structural difference is the wing rear spar attachment. From a design standpoint the folding wing version is stronger than the standard fixed wing airplane. This is because a 4130 steel bracket is used on the center section rear spar to attach the outer wing rear spar. The wing has an extra rear spar attach fitting added to sandwich a rod end bearing threaded into the center section steel fitting.

The folding wing is a mechanical device and is therefore more vulnerable to user-induced damage. Because of this, the manual says no aerobatics with the folding wing. The problem is if the wing is damaged while being folded and not repaired before being put through the rigors of aerobatics. We cannot control a circumstance where someone drops the wing while folding it or trailers it improperly and then without completing a proper inspection subjects the aircraft to high inflight loads. The rear spar absorbs the wing's drag load, which is highest during high angles of attack and high airspeeds. There has, however, never been a problem with our folding wing design over the many years it has been used.


Snowflake 01-30-2012 05:57 PM

Sounds like more of a "CYA" than "it's not aerobatic". As with any aircraft used for aerobatics, you want to be sure you know it's history and inspect it carefully before every flight where spirited manoeuvers are to be performed.

LifeofReiley 01-30-2012 06:06 PM

Hmm...
 
I find it totally amazing that the first thread posted referencing to this plane here on VAF was deleted almost ASAP due to a relation/reference to a Barnstormers ad, and this thread is totally ignored by the moderators... go figure. :confused:

Nice plane!

JohnInReno 01-30-2012 06:19 PM

Thought about buying
 
I looked at this plane about 4-5 years ago and what I remember is:

1. Was Subie - converted to o290.
2. Lots of engineering on the folding wings to fit in a garage at Widby? Island.
3. Tested to Utility class.
4. Handheld ICOM mounted as radio.

It was too experimental for me at the time.

If you are really interested, why not contact the seller?

Snowflake 01-30-2012 06:22 PM

Quote:

Originally Posted by WingsOnWheels (Post 623000)
It would be great if Vans could off a mod to make the RV with folding wings like the Mustang II. I like the RV better, but the folding wings on the mustange are very cool.

The *tapered* wings on the Mustang II are very cool too... ;)

bhassel 01-30-2012 06:36 PM

The folding wing on the T-18 was designed by the same gentle man that designed the S-18. He also designed the wider fuse mod on the T-18 that you can still get with the plans and that is standard on the S-18. The T-18 plans are no longer sold with the folding wings options (although the wider body options is available) and the S-18 is only available in a kit.

Bob

Quote:

Originally Posted by SHIPCHIEF (Post 623812)
I wonder if that's true, or if it's "Common Knowledge"?
The final Thorp T-18 model, the S-18, is folding wing, and the aerobatic gross weight is 1500 pounds. The 'older' T-18 aerobatic gross weight is 1250 lbs.
The folding mechanism is said to be the same for the S-18 and the Mustang II.
I just flew out with the wife to look at an S-18 folder, on a trailer in a garage.
It was a great day trip with wonderful flying, and also wonderful new people to meet.
The aircraft in question is not a flier, more of a restoration project. but the folding wing mechanism was out in the open for easy viewing. I'd say it's pretty straight forward, and similarly strong.



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