Had a friend contact me about going in halfs on an RV3. The one he is considering seems pretty nice but there is a gray area on the wing spars. The owner said he bought it from the builder. It was built 1980ish by an engineer and at that time there was some concern of the spar. He apparently went with a one piece spar design. The owner said this was something that a few people did before the mod came out and that the mod does'nt need to be done. Does anyone have any insight on this? Was this something built from plans, engineered and tested, or some scrap metal at the local machine shop? We are trying to get a copy of the build log and log book to see what we can find out. Just thought I would see if there is any knowledge of this method here, Thanks
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
One piece spar (built pre wing mod)
- Thread starter zx6rrider
- Start date
Have you called Vans? This sounds like something they would have at least discussed with RV-3 builders at one point, if not something they provided parts for.
Despite being an engineer myself, I still cringe sometimes when I hear "it was done by an engineer." You never know whether it was an electrical engineer who was building an airplane in his spare time, or a Boeing structural engineer building it with the help of his entire staff. You're correct to be wary.
Despite being an engineer myself, I still cringe sometimes when I hear "it was done by an engineer." You never know whether it was an electrical engineer who was building an airplane in his spare time, or a Boeing structural engineer building it with the help of his entire staff. You're correct to be wary.
Andy Hill
Well Known Member
Ummmm... sounds "dodgy" 
From a quick read:
I suggest a read of the FAA Notice, and the 2 CN documents, then see how it relates to what has been built / recorded.
If the wing spar has been built to anything other than Vans' plans, then it would seem it is neither an "RV-3" nor an "RV-3A" nor an "RV-3B". Where it sits wrt being allowed by the FAA to perform aerobatics might be an interesting question?
Andy
From a quick read:
- CN1 concerns the Rear Spar and Root Ribs i.e. not the Main Spar.
- CN2 concerns the Spar Caps, and seems not to be the centre section?
I suggest a read of the FAA Notice, and the 2 CN documents, then see how it relates to what has been built / recorded.
If the wing spar has been built to anything other than Vans' plans, then it would seem it is neither an "RV-3" nor an "RV-3A" nor an "RV-3B". Where it sits wrt being allowed by the FAA to perform aerobatics might be an interesting question?
Andy
nomocom
Well Known Member
Rv-3 with one piece spar?
One piece suggests that the left and right wing do not butt in the middle (tied together by bolts and plates), rather there is a monolithic spar without the joint in the middle. However, if this were the case, assembly of the airplane would be complicated as the spars do not drop into the fuselage, but slide in from the sides.
Assuming this were the case, I can't see that it would improve the front spar. However, in back, a one piece in concept would be better, as it would likely avoid the bolt hole edge distance issues found in some 3's. However, in the 80's it wasn't well understood what exactly the spar weaknesses were. Whatever hoops the builder went through to make a single piece wouldn't seem to address the deficiencies of weak wing roots (cn-1) and buckling of the upper web of the front spar (cn-2) while adaptions made to the fuselage to fit a one piece spar (whatever they were) could make things worse.
Intriguing.... let us know what the spar looks like. Build logs or not, a few pictures would be worth a thousand words. I'd suggest a pic of the front of the spar, shot down and back from above the fuel valve. That would show if the left and right spars are tied together with plates or if it is one piece. I'd also suggest a photo of the rear spar tabs/bolts. IIRC, unbolt the flap from the control rod, swing the flap down, then shoot forward into the wing-fuse intersection should show the rear spar tabs.
good luck
One piece suggests that the left and right wing do not butt in the middle (tied together by bolts and plates), rather there is a monolithic spar without the joint in the middle. However, if this were the case, assembly of the airplane would be complicated as the spars do not drop into the fuselage, but slide in from the sides.
Assuming this were the case, I can't see that it would improve the front spar. However, in back, a one piece in concept would be better, as it would likely avoid the bolt hole edge distance issues found in some 3's. However, in the 80's it wasn't well understood what exactly the spar weaknesses were. Whatever hoops the builder went through to make a single piece wouldn't seem to address the deficiencies of weak wing roots (cn-1) and buckling of the upper web of the front spar (cn-2) while adaptions made to the fuselage to fit a one piece spar (whatever they were) could make things worse.
Intriguing.... let us know what the spar looks like. Build logs or not, a few pictures would be worth a thousand words. I'd suggest a pic of the front of the spar, shot down and back from above the fuel valve. That would show if the left and right spars are tied together with plates or if it is one piece. I'd also suggest a photo of the rear spar tabs/bolts. IIRC, unbolt the flap from the control rod, swing the flap down, then shoot forward into the wing-fuse intersection should show the rear spar tabs.
good luck
I've inspected a LOT of RVs. I have never heard of this "option." I would like to see pictures.
WingsOnWheels
Well Known Member
I agree that a picture would be quite helpful. I wonder if rather than a one=piece spar, they used large machined bar stock like on the newer RVs rather than the usual stack-up.
I have a feeling that this is a miscommunication between the builder and current owner.
I have a feeling that this is a miscommunication between the builder and current owner.
I have a feeling there is a communication issue also. Not sure what the owner actually means and havn't gotten any good pics of it or the uild log. Thanks for all the responses, I've been on vacation so sorry I didn't reply earlier. I'm kinda thinking we may not pursue it due to the questionable wing and poor logs. My partner talked to vans and they are aware there were some other designs, although they cant comment on them as they were not directly involved in the engineering or building, all they said is there has not been an issue that they have heard of. If we decide to go through with it, I'll get a copy of the builder log and try to pass that info along. My partner said the owner got testy with him when he started asking more questions about the wing, sounds like hes getting upset because a few others have also called about it and got cold feet because of them. Not saying that they are bad as I havn't got a good chance to see the design myself, but all potential buyers have been wary of them. Ill keep you posted if we try and pursue it, Thanks
Now that really sounds dodgy, or at the very least shady. If the owner is getting testy when people are asking about the mod, you should stay away from it. If the mod is proven through documentation and analysis (and if it was an engineered solution it may be just fine) then he should have no problems with sharing that info with you. He should expect you to want it. Any prudent and informed shopper would.
If he doesn't want to share it, or is standoffish about providing more info on it, there's a chance he doesn't have anything to back up the claim that his mod is as good as the factory-offered mod. In which case he probably has a pile of scrap metal in his hangar, as no sane pilot would buy it in that condition.
If he doesn't want to share it, or is standoffish about providing more info on it, there's a chance he doesn't have anything to back up the claim that his mod is as good as the factory-offered mod. In which case he probably has a pile of scrap metal in his hangar, as no sane pilot would buy it in that condition.
danweseman
Active Member
rv-3 with one peice wing
I talked with the owner 2 weeks ago. the wing spar is built like other rv with bars but the front and rear spar are built in one long section tip to tip. to remove the wing you drill out two strips under the fuse then take out 4 bolts,2 front 2 rear and set the wing on the floor. its been flying alomost 30 years and for 2000 hrs! Its been flown acro its whole life and he said saw 260 IAS once? it has a fuse tank and a 160 hp engine. for 18k it may be a great airplane to retrofit the -b wings and tanks onto? Dan
I talked with the owner 2 weeks ago. the wing spar is built like other rv with bars but the front and rear spar are built in one long section tip to tip. to remove the wing you drill out two strips under the fuse then take out 4 bolts,2 front 2 rear and set the wing on the floor. its been flying alomost 30 years and for 2000 hrs! Its been flown acro its whole life and he said saw 260 IAS once? it has a fuse tank and a 160 hp engine. for 18k it may be a great airplane to retrofit the -b wings and tanks onto? Dan
