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Larryskydives 10-29-2014 01:30 PM

RV-4 Spar Information Needed
 
Looking at buying a RV4 Have not been able to get any good information on spars. Are the spars all aluminum, or were some early on laminated wood? Looking for experiences with te woods spars versus aluminum?

Thanks

Mike S 10-29-2014 01:32 PM

Welcome to VAF!
 
Larry, welcome aboard the good ship VAF:D

rvator51 10-29-2014 02:04 PM

I have never heard of a wood spar for a RV-4. I doubt there ever was.

Russ McCutcheon 10-29-2014 04:15 PM

All metal airplane
 
there is no wood structure in any RV's and there never has been.

Larryskydives 10-29-2014 05:03 PM

Thanks for the info. I didn't think there was but I am looking at a RV4 and the current owner said it has a wood spar. Going to look into it further. Let you know what he says. Thanks

LifeofReiley 10-29-2014 05:05 PM

Quote:

Originally Posted by Larryskydives (Post 928984)
Thanks for the info. I didn't think there was but I am looking at a RV4 and the current owner said it has a wood spar. Going to look into it further. Let you know what he says. Thanks

Run as fast as you can AWAY!!! :eek:

Neal@F14 10-29-2014 05:05 PM

Quote:

Originally Posted by Russ McCutcheon (Post 928960)
there is no wood structure in any RV's and there never has been.

I've seen a wooden instrument panel insert in one :p

Neal@F14 10-29-2014 05:09 PM

Quote:

Originally Posted by Larryskydives (Post 928984)
...I am looking at a RV4 and the current owner said it has a wood spar.

If somebody did build one with wood spars inside the wings, then it is no longer an RV-4 but something quite different, and with very unknown +/- G strength.

Mike S 10-29-2014 05:15 PM

Only wood spar connection I know of---------and I am stretching it a lot----------is the RV 1. It had wood wing, but that was before it became the RV 1.

Pretty sure it it is an RV 4, the wing is all metal.

southtarnation 10-29-2014 05:29 PM

The most likely explanation is that the seller "thinks" its wood...
And it is probably just like every other rv-4 spar, Not wood.

If someone (a laymen) looked at it from the top where it meets (or would meet) in the cabin it might look like wood due to it looking similar to several thin(er) pieces of wood that have been laminated into a single "spar".

Again though, it very likely just like every other Rv-4 spar.

scratch it and see.

Doug 10-29-2014 11:56 PM

Probably not an RV-4.

Snowflake 10-30-2014 07:34 AM

Quote:

Originally Posted by southtarnation (Post 928997)
If someone (a laymen) looked at it from the top where it meets (or would meet) in the cabin it might look like wood due to it looking similar to several thin(er) pieces of wood that have been laminated into a single "spar".

Best explanation yet. Maybe the current owner bought it used and doesn't really know how it was built. All those laminations coming together in the middle could be mistaken for wood grain, I guess. Especially if it was painted brown... :)

rbibb 10-30-2014 08:04 AM

The RV-4 has had only one spar design for its entire life as far as I know. The only "options" where whether one tapered the laminated stiffeners in length.

The spar (similar to all RVs) has a large U Shaped channel (web) that is formed from bent aluminum. To both the front and aft sides of this piece 1/8" thick (going from memory here) stiffeners are riveted to the spar web using 3/16" rivets. The stiffeners strips are about 1 - 1.5" wide and are stacked on top of one another to make the complete thickness of the spar.

Since loads lessen the farther toward the wingtip you go the need for stiffeners to meet the designed load carrying ability decreases, hence the number of stiffeners decreases. Indeed for the last foot or two only one stiffener thickness (forward side) is needed.

Also, the stiffeners were made from 1/8" x 1.5" (I think) bar stock (a standard size. In order to save weight the builder could optionally taper the spar strips in width per the plans. Builders of later model RVs will see the same design feature in the machined dimensions of the one piece stiffener used in later models. Access to a CNC machine makes fabrication simpler than when you are doing things with a hacksaw.

Back in the day there used to be discussions and such in the early editions of the RVator as to techniques the builder without access to a machine shop could use to cut such tapers. The best answers usually involved a bandsaw but using a hollow-ground planer blade on a table saw produced the nicest finish IIRC.

All eventually came to naught as the availability of pre-made spars with machined cut tapers, anodized finished parts, and precise set rivets (in a brake press probably) made user fabricated spars as rare as humble tail-dragger pilots.

So, if that plane is an RV-4 it has a metal spar. Only question is was it pre-made by Phlogiston (a good thing) or made by the builder (something that just needs a bit more inspection but, in itself, no reason to run for the hills).

If, upon inspection you see anything that looks like wood, congratulate yourself on finding a rare, probably one-of-a-kind example of the homebuilt aircraft world. But just know that it ain't an RV-4 even if you can understand why someone might want to claim to be one of the best flying airplanes ever designed.

eisnerrv4 10-30-2014 08:22 AM

RV-4 Spar
 
No sense adding my two cents worth. It's all been covered.

Good luck in purchasing one. Fabulous aircraft.

Mike S 10-30-2014 08:39 AM

Quote:

Originally Posted by rbibb (Post 929135)
as rare as humble tail-dragger pilots.

Gotta remember that one:D

Larryskydives 10-31-2014 12:46 PM

Thanks for all of the info. Knowledge is power. Talked with the owner again and asked if he was sure it was wood. Said it was, after I told him what I had found out, he said maybe it wasn't wood. I tend to think that the laminated look at a distance looked like a wood grain. But all for naught, I think he has sold it today.

On another note, I just can't understand a person buying an airplane. experimental or certified and not knowing it's construction. But such as it is, still in the hunt for an RV4, and again thanks for the info Never know when I might be back asking for more!!


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