Spar wood replacement

[shipljl]

First question. My BC12-65 left wing has the original spar wood from 1941. The spar appears to be in excellent shape. Should it be replaced just because it is old? How old is too old?

Second question. Is there any precedent for milling lightening pockets in the spars, STC etc?

Third question. The ribs are only attached with 1/4 inch nails. When I reassamble, should the ribs be bonded to the spar as well as nailed?

thanks

[Robert Lees]

Re: Spar wood replacement

1. Your spars are made of wood, and were probably over 100 years old when new. If they're "only" another 65 years older, that's still good. If it ain't broke, don't fix it.

2. No.

3. No.

[Larry Lyons]

Re: Spar wood replacement

I concur! My 41 was just like yours only the spars were cracked through the root fittings. Very hard to see untill I took the fittings off the spars! Larry

[shipljl]

Re: Spar wood replacement

Thanks for the advice on the spar wood. I have a couple more questions and the first has to do with corrosion proofing my ribs. For weight saving reasons I would like to strip the ribs and alodine them. Is there any reason that this isn't a good idea? One wing has bare aluminum (apparently the way they were made, the other has painted ribs). Is it ok to alodine them?

Also, does anyone know a source for the folded aluminum "T" stock that the ribs are made of? I saw a photo sequence of a restoration of a BC12-65 online where some of the ribs were replaced with ribs formed from a flat sheet; looks like they came from a later BC12-D. Is it ok to replace damaged "T" ribs with the later sheet ribs?

[blakecarl]

Re: Spar wood replacement

I concur! My 41 was just like yours only the spars were cracked through the root fittings. Very hard to see until I took the fittings off the spars! Larry

Larry - We have had an issue come up regarding our spars, see “Spar Joints” thread. Based on your reply am I correct in concluding you are suggesting that even though it appears to be in excellent shape, the wing needs to be taken off and at least partially disassembled for inspection to insure it is?

Blake

[Hank Jarrett]

Re: Spar wood replacement

Cracks (actually splits) along the grain of a wood beam are not nearly as critical as splits that run through holes with pins transferring loads (the wing spar is essentially a beam and the spar to fuselage attach fitting bolts are pins through the beam). The failure is made worse because the spar attach fittings can cover the splits. The steel spar fittings are angled on the spar so that the holes will NOT line up for a split through the grain from one hole to another.
Split grain from a hole is SERIOUS BUSINESS. ESPECIALLY at the root end where the bending load is highest.
Hank

[jim cooper]

Re: Spar wood replacement

Who recovered the airplane last? When? 10-20-30 years ago? Are you able to SPEAK to the person who recovered it? Its impossible to REALLY see the entire spars by looking around thru the inspection holes, so.....If the airplane has never been groundlooped or otherwise damaged then you MAY be ok. Then again, if the logs are not clear (scrawled signatures, impossible to read entrys, etc.) Aircraft parked OUTSIDE alot? Then personally, I would recover the wings, looking everything over carefully. Cracks are very hard to see in some cases. My T-craft, totally redone in 1998, was then flown by the rebuilder until last year (600 hrs.) I can only assume he did inspect the spars carefully seeing as he was going to fly it around alot.JC

[Marv]

Re: Spar wood replacement

From my experience a log book is a liars sheet. Some things are entered in the log book to look good, some bad things are not entered at all, and the paperwork you have may be for a airplane that crashed and burned in 1950.The only way to be safe is start all over and check things properly, and not the quick, easy, and cheap way. That extra money and time you spend, may give you more time with your grand kids. Marv

[Larry Lyons]

Re: Spar wood replacement

My spars had no visible damage until I removed the wings. Looking at the end grain on the inboard end of the spar is where we spotted what looked like a crack. Although the wood was tight with no sign of movement at this point. After removing the wing attach fitting though I found the crack ran from the inboard end to to, I believe, the third bolt hole. It turned out I had another similar crack on the rear spar too! How long had this plane flown with this damage is unknown. The son of the owner tells me used to do multiple loops with her and gain altitude while doing so!
Larry

[Dennis Keels]

Re: Spar wood replacement

I think Marv is right you make a set of logs say anything you want.

[jim cooper]

Re: Spar wood replacement

MARV......is right on! I've mentioned this before. Many logs are to be read to children at night as fairy tales. (Especially the ones with the unreadable signatures and addresses, AI numbers, etc.) Occasionally though, you see a name or airport shop that you know to be good. Sometimes....not often, you even know the name of the person who did it. It really seems to be, either you buy a recently done aircraft from a reputable BUILDER or you take your chances. (You will eventually pay MORE for the poorly done aircraft as your constantly having to repair some hidden damage or engine screw up.) I had a Stearman and a 195. BOTH were sold by expert liars. I paid dearly in the end, in time and money. (Both LOOKED great!) My current T-Craft, I bought from the restorer. HIS logs are excellent ,(as is his reputation) and his are the only ones I really care about. What happened in 1948, 1955, 1960, etc. I couldn't care less. Its a better airplane than when it left the factory...FOR SURE! (Ex: When I pull into an airport, someone will invairably come over and say.."That is a great looking Taylorcraft! Who did it?" Open the cowl? its perfect. Look inside? Perfect. etc. Its fun to fly something like this!JC
!