Potential Aircraft Purchase - Wooden Spar Concerns

[Fearless Tower]

Looking at a possible purchase (1966 Citabria) and have a concern about the wooden spar.

This particular aircraft has damage history -1983 hard landing - collapsed gear and damage to wingtips.

Left spar was replaced in 2000.
Right spar replaced in 1982 (before the accident)

Aircraft was painted in 2008.

The overall condition of the aircraft is very good. My concern from a purchase standpoint is the right wing. The paint (2 years old) is starting to chip and flake off along some of the rib seams. There is no paint chipping on the left wing, but the left spar is obviously much newer. Could this be a sign that the right spar is in need of replacemement and how much do spar replacements cost? It would seem to me that there is clearly more flex in the right wing vs left.

Obviously, a thorough pre-puchase inspection would answer my questions. Since I don't have any experience with maintaining a wood spar plane, I am mostly just wondering if given the info above, if it is worth paying the money for the inspection or if I should forget about this bird entirely and move on.

 

[Telemakhos]

If you're having a creepy feeling now, walk away. The plane might be fine, but you run the risk of always being rattled by it... no one needs a confidence destroyer.
Especially when the confidence problem is related to the possibility of in-flight wing failure or separation.

 

[Ken Ibold]

Finding someone competent to do wood spar inspections will depend on where the aircraft is located. They're getting hard to find in a lot of places.

The spar replacement would necessitate recovering the wing. When the aircraft was painted in 08, was it also recovered? If not, the flaking you're seeing may be due to the age of the fabric. If you have 1982 fabric under the paint on the right wing, you may be looking at an owner who put lipstick on a pig.

If the fabric was done in 08 along with the paint job and the paint is flaking already, you may have some wing flex issues, or you may just have a crappy recover/paint job.

No matter how you slice it, you need a competent wood spar inspector to go through this. Someone with wood spar experience is probably also experienced in fabric.

 

[Fearless Tower]

The spar replacement would necessitate recovering the wing. When the aircraft was painted in 08, was it also recovered? If not, the flaking you're seeing may be due to the age of the fabric. If you have 1982 fabric under the paint on the right wing, you may be looking at an owner who put lipstick on a pig.

If the fabric was done in 08 along with the paint job and the paint is flaking already, you may have some wing flex issues, or you may just have a crappy recover/paint job.

That makes alot of sense - thanks for pointing that out. I'll be sure to ask the owner and maintenance shop for the fabric age before pursuing the pre-purchase. Fortunately, we do have a few shops in the area familiar with wood spar/fabric covered Citabrias.

 

[Tom-D]

There is an AD on the wood spars on a Citabria, be sure it is complied with and the new inspection holes are there.

Inspecting the spar is no biggey, but complying with the AD for the first time is a PITA.

There is a upgrade to the metal spars it costs about 15k to convert.

 

[Tom-D]

http://www.bellanca-championclub.com/SL406A.html

http://www.aeroncapilots.com/Spar_AD.htm

 

[Tom-D]

The overall condition of the aircraft is very good. My concern from a purchase standpoint is the right wing. The paint (2 years old) is starting to chip and flake off along some of the rib seams.

Do you know which system was used to recover?

 

[Fearless Tower]

There is an AD on the wood spars on a Citabria, be sure it is complied with and the new inspection holes are there.

Inspecting the spar is no biggey, but complying with the AD for the first time is a PITA.

There is a upgrade to the metal spars it costs about 15k to convert.

Saw the AD - haven't spoken to the owner yet, but reading the AD, it looks like it should have been done initially back in 2001 and every year after that. The plane just came out of annual 2 weeks ago, so we'll see how well it has been 'maintained'.

As for the new wings - Current ACA factory price is around 20k now and apparently it boosts the max gross weight - kind of nice bonus for the 115hp.

 

[Tom-D]

Saw the AD - haven't spoken to the owner yet, but reading the AD, it looks like it should have been done initially back in 2001 and every year after that. The plane just came out of annual 2 weeks ago, so we'll see how well it has been 'maintained'.

As for the new wings - Current ACA factory price is around 20k now and apparently it boosts the max gross weight - kind of nice bonus for the 115hp.

Remember, the Ceconite never fails, it's the paint that failed to adhere.

The factory is the only place that will convert to the metal spar and give the gross increase. but you can buy all the parts and build up a set of wings and replace the ones you have cheaper than the factory conversion.

 

[Fearless Tower]

The factory is the only place that will convert to the metal spar and give the gross increase. but you can buy all the parts and build up a set of wings and replace the ones you have cheaper than the factory conversion.

Got ya, thanks!

 

[Anthony]

I don't know where you are located, but if you're anywhere near PA, take it to Tom Witmer at Witmer Aviation at Pottstown Muni, N47. He is the east coast Bellanca guru. Has guys that know wood and fabric really well.

 

[Ken Ibold]

There is an AD on the wood spars on a Citabria, be sure it is complied with and the new inspection holes are there.

Inspecting the spar is no biggey, but complying with the AD for the first time is a PITA.

There is a upgrade to the metal spars it costs about 15k to convert.

Tom, for YOU inspecting the spars may be no biggie. But I recall when the AD first came out there was a big spike in the number of good spars that were trashed because the inspectors didn't know what they were looking for, so erred on the side of throwing new parts at it. There are a lot of places where even experienced mechanics have never seen a wood spar before.

As for the metal spars, there is the Milman kit that replaces the spars but reuses the ribs. Gross weight is unchanged. IIRC the weight of the spar is just about a wash, so useful load is pretty close to unchanged. The factory spar conversion, which has the gross weight increase to 1750, means new spars and ribs.

 

[ebetancourt]

Again depending on where you are, the factory is a pretty neat place, they are pretty accommodating, reasonably priced, and you might talk to them about the pre-buy.

Ernie

 

[dmccormack]

Many fabric airplanes were painted with automotive enamels. These are likely to exhibit premature cracking and flaking.

Since 2001, the FAA has required that fabric covered aircraft (at least the fabric parts) be painted only with topcoat paints tested and approved on an STC. Use of any other topcoat paint will void the STC and airworthiness of the aircraft. Up to 2001, the STC's "ended with the silver", and any type paint was legal to use. This is no longer true. Over the years, increased use of brittle automotive or industrial paints caused enough cracking and delamination to cause the FAA to rethink approving untested topcoat paints over fabric. Failed topcoat paints expose polyester fabric to sunlight and UV damage.

http://www.polyfiber.com/stits/index.htm

 

[Tom-D]

Many fabric airplanes were painted with automotive enamels. These are likely to exhibit premature cracking and flaking.

http://www.polyfiber.com/stits/index.htm

That is Poly Fiber hype and a bunch o crap.

Recovering the aircraft has always been a major repair. (see FAR 43-A) and returned to service on a 337 with a compliance statement. (see block 6 of the form.) any fabric system must have a application instructions booklet which tells us how to apply the system.

OBTW Poly Fiber is crap. stinks to high heaven. is harmful to your health. and the most difficult to apply, and is the most expensive to buy.

 

[dmccormack]

That is Poly Fiber hype and a bunch o crap.

Recovering the aircraft has always been a major repair. (see FAR 43-A) and returned to service on a 337 with a compliance statement. (see block 6 of the form.) any fabric system must have a application instructions booklet which tells us how to apply the system.

OBTW Poly Fiber is crap. stinks to high heaven. is harmful to your health. and the most difficult to apply, and is the most expensive to buy.

Well, now that we know how you feel, my airplane is Stitts Polyfiber and is still tight and no cracks.

Where does what I quoted state that a recover *isn't* a major repair??

 

[tonycondon]

one of our clubs gliders is painted with automotive paint. it's got a bunch of cracks in the finish from the the wooden fuselage flexing...

 

[Ken Ibold]

Again depending on where you are, the factory is a pretty neat place, they are pretty accommodating, reasonably priced, and you might talk to them about the pre-buy.

Ernie

Last I checked, the factory will NOT repair wood spars. They want to see them all trashed ... and replaced by factory parts. They might inspect them, but I would be cautious of their motives if they failed the spar.

 

[Tom-D]

Well, now that we know how you feel, my airplane is Stitts Polyfiber and is still tight and no cracks.

Where does what I quoted state that a recover *isn't* a major repair??

my point was that the Polyfiber info was not correct, because every system has an installation manual and none authorize the use of auto finishes. they never have and probably ever will.

At one point in time the Stitz / polyfiber was the state of the art system, but not any more.

 

[dmccormack]

my point was that the Polyfiber info was not correct, because every system has an installation manual and none authorize the use of auto finishes. they never have and probably ever will.

At one point in time the Stitz / polyfiber was the state of the art system, but not any more.

I've been looking around and am leaning towards the Stewarts system, due to the lack of fumes and noxious chemicals. I had enough of that on Active Duty.

 

[tonycondon]

I've been looking around and am leaning towards the Stewarts system, due to the lack of fumes and noxious chemicals. I had enough of that on Active Duty.

I would highly recommend it.

 

[Dan Thomas]

I've been looking around and am leaning towards the Stewarts system, due to the lack of fumes and noxious chemicals. I had enough of that on Active Duty.

I hope the Stewart has no relation to the Blue River waterborne process. Have had two airplanes in here with it and it was terrible, terrible stuff. Hopeless. They don't even have the STC anymore. It would fall off the fabric. It would swell when cool and wet. I hope the Stewart has proven itself better than that.

I use Poly-Fiber because it stays flexible in the cold and doesn't crack and is easy to fix, something important around a northern flight school where the airplane doesn't have to be really shiny and pretty. I've had far more trouble fixing anything with urethane on it and sure wouldn't use the old flammable dopes.

Dan

 

[dmccormack]

I hope the Stewart has no relation to the Blue River waterborne process. Have had two airplanes in here with it and it was terrible, terrible stuff. Hopeless. They don't even have the STC anymore. It would fall off the fabric. It would swell when cool and wet. I hope the Stewart has proven itself better than that.

I use Poly-Fiber because it stays flexible in the cold and doesn't crack and is easy to fix, something important around a northern flight school where the airplane doesn't have to be really shiny and pretty. I've had far more trouble fixing anything with urethane on it and sure wouldn't use the old flammable dopes.

Dan

No idea if Stewarts = Blue River.

I'm impressed with the longevity of Poly-Fiber -- the covering on my Airplane was applied in 1979. We did a very thorough annual this year with a look-over by a local FSDO maintenance inspector -- everyone's impressed by the cover job. No one has guessed the age until told.

I still plan on a recover , but it's lower on my priority list.

 

[tonycondon]

No idea if Stewarts = Blue River.

I'm impressed with the longevity of Poly-Fiber -- the covering on my Airplane was applied in 1979. We did a very thorough annual this year with a look-over by a local FSDO maintenance inspector -- everyone's impressed by the cover job. No one has guessed the age until told.

I still plan on a recover , but it's lower on my priority list.

my google searching leads to some posts on a supercub forum by a stewarts salesman that say no stewarts is in no way related to blue river. apparently blue river was water based while stewarts is water borne.

the fabric on my glider was from 1972 i believe. The fabric was fine but the paint wasn't so great. It was loaded with cracking but most of that was probably due to the poly fiber topcoat not getting along well with whatever dope was used originally.

Leah's fabric is original JC Penny polyester from 1964. The paint job on hers was actually pretty good but that old dope underneath was slowly crushing the wood and the poly fiber on top was adding a lot of unnecessary weight.

 

[Tom-D]

I hope the Stewart has no relation to the Blue River waterborne process.

The Stewarts have no relation with any other system, theirs is a water born ura product. that works very well in any conditions

I use Poly-Fiber because it stays flexible in the cold and doesn't crack and is easy to fix, something important around a northern flight school where the airplane doesn't have to be really shiny and pretty. I've had far more trouble fixing anything with urethane on it and sure wouldn't use the old flammable dopes.

Dan

If Poly Fiber isn't a poly ura what is it?

I have three cans of the stuff, all three say it is a polyurethane.
all three stink, all three require a special thinner and activator, which all must be bought at their inflated prices.

Airtech has a special reducer and thinner for each of its coatings, all stink, but cure with in 8 hours to full hard ready to sand. and is full filling in 2 coats of primer, one sanding then apply the top coat. and does not require 6 coats of silver to stop UV light damage to the Ceconite. (which never rots any way) This system is used by the Ag-Croppers as it is chemical proof.

Stewart's system, requires fewer coats than does Polyfiber, but more than Airtech, and does not require any silver because like Airtech it has a built in additive for a UV blocker, it is water born and your equipment cleans up with water there is no reducer but there is a hardener for the top coat which can be Randolf coatings urethane.

I have been recovering aircraft since I was a kid, and was thrilled when we could go with Stitz, but now I will not use it because of the cost, and harmful vapors, and the required equipment to handle it.

 

[Dan Thomas]

If Poly Fiber isn't a poly ura what is it?

I have three cans of the stuff, all three say it is a polyurethane.
all three stink, all three require a special thinner and activator, which all must be bought at their inflated prices.

Airtech has a special reducer and thinner for each of its coatings, all stink, but cure with in 8 hours to full hard ready to sand. and is full filling in 2 coats of primer, one sanding then apply the top coat. and does not require 6 coats of silver to stop UV light damage to the Ceconite. (which never rots any way) This system is used by the Ag-Croppers as it is chemical proof.

Stewart's system, requires fewer coats than does Polyfiber, but more than Airtech, and does not require any silver because like Airtech it has a built in additive for a UV blocker, it is water born and your equipment cleans up with water there is no reducer but there is a hardener for the top coat which can be Randolf coatings urethane.

I have been recovering aircraft since I was a kid, and was thrilled when we could go with Stitz, but now I will not use it because of the cost, and harmful vapors, and the required equipment to handle it.

If your Poly says urethane, you have their Aerothane topcoat. It's an option and is as toxic as the dickens like any other urethane. The need for an activator is also common to urethanes (and epoxies). The rest of their system, including the standard Poly-Tone topcoat, is polyvinyl chloride, more commonly known as PVC. One of the most common plastics produced and used in everything from toys to upholstery to plumbing and so on. No activators; it just dries. But, as you say, it stinks, but it doesn't make me ill like the urethanes will. I won't work with urethanes or epoxies without a fresh-air hood and decent body protection. PVC is easily controlled with a charcoal vapor mask.

I do look forward to trying the Stewart system.

Dan

 

[jesse]

I have no idea what I'm doing but the Stewart system seemed pretty damn slick when I helped Tony cover his wings.

 

[tonycondon]

I have no idea what I'm doing but the Stewart system seemed pretty damn slick when I helped Tony cover his wings.

yea, its so easy even Jesse could do it

 

[Baron2PG]

Getting back on the subject of Wood Spars. I too am looking to purchase a Decathlon which is subject to the same wood spar AD as the Citabria. A "friend" advised that I only look at planes that have had the wood spar replaced with the aluminum spar or buy a newer 90's Decathlon that came from the factory with the AL spar.

Unfortunately, there are only a few '70s with the spar replacement and they are out of my price range. The new planes '90s onward are outside of my budget. There are a couple very nice '70s wood spar aircraft available. However, the seeds of doubt have been firmly planted and I'm not sure I'm comfortable with a wood spar aircraft. 1) I don't want the wing to fail (duh) though I know this probably is highly unlikely and there haven't been any documented wing seperation failures 2) I don't to get stuck with a $20K repair bill for a $40K airplane; this is the major concern. I buy a $40k plane and the 1st annual they find a cracked spar. Now I'm SCREWED.

 

[Tom-D]

If your Poly says urethane, you have their Aerothane topcoat. It's an option and is as toxic as the dickens like any other urethane. The need for an activator is also common to urethanes (and epoxies). The rest of their system, including the standard Poly-Tone topcoat, is polyvinyl chloride, more commonly known as PVC. One of the most common plastics produced and used in everything from toys to upholstery to plumbing and so on. No activators; it just dries. But, as you say, it stinks, but it doesn't make me ill like the urethanes will. I won't work with urethanes or epoxies without a fresh-air hood and decent body protection. PVC is easily controlled with a charcoal vapor mask.

I do look forward to trying the Stewart system.

Dan

try this, go to your local hobby store and get a embroidery hoop about 18" across, order 1 yard of ceconite 103, entrap the ceconite in the hoop, and use that as a experiment. call don at his order number and ask for a kit to try. 1 pt of ecofill, and 1 pt of top coat and activator.

they will be more that happy to allow you to try the system.

their process is all on youtube

http://www.youtube.com/watch?v=rl9I3FOA6Bc
http://www.youtube.com/watch?v=48OeYmvYHDM

 

[jesse]

yea, its so easy even Jesse could do it

I had better success with that then I did with drilling holes in your trailer. The 45,000 RPM single speed drill wasn't helping matters.

 

[gismo]

Getting back on the subject of Wood Spars. I too am looking to purchase a Decathlon which is subject to the same wood spar AD as the Citabria. A "friend" advised that I only look at planes that have had the wood spar replaced with the aluminum spar or buy a newer 90's Decathlon that came from the factory with the AL spar.

Unfortunately, there are only a few '70s with the spar replacement and they are out of my price range. The new planes '90s onward are outside of my budget. There are a couple very nice '70s wood spar aircraft available. However, the seeds of doubt have been firmly planted and I'm not sure I'm comfortable with a wood spar aircraft. 1) I don't want the wing to fail (duh) though I know this probably is highly unlikely and there haven't been any documented wing seperation failures 2) I don't to get stuck with a $20K repair bill for a $40K airplane; this is the major concern. I buy a $40k plane and the 1st annual they find a cracked spar. Now I'm SCREWED.

I've owned two wood spar airplanes and never had any concerns. It's my understanding that a) If a wood spar looks good to a mechanic well versed in wood/fabric airplanes it's perfectly safe as defects are always very visible assuming there's decent access for inspection; and b) when overstressed, wood spars generally fail in a manner that lets the plane keep flying unless the overstress is huge (in which case no metal spar would survive either).

IOW, to avoid that $20k surprise all you need to do is have it properly inspected by a qualified AI.

 

[Ken Ibold]

I've owned two wood spar airplanes and never had any concerns. It's my understanding that a) If a wood spar looks good to a mechanic well versed in wood/fabric airplanes it's perfectly safe as defects are always very visible assuming there's decent access for inspection; and b) when overstressed, wood spars generally fail in a manner that lets the plane keep flying unless the overstress is huge (in which case no metal spar would survive either).

IOW, to avoid that $20k surprise all you need to do is have it properly inspected by a qualified AI.

Lance is right on the money here.

In addition, you have to look at other dynamics when it comes to early American Champion models. They had some problems with their paint system from when they restarted production in 1995 until about 2003-2004 wherein there was rampant cracking along the tape lines on top of the wing and on the horizontal stabilzer and elevator. I asked the owner, the owner's son, and the factory tech people about it numerous times in my previous life as a journalist as well as an owner of an 01 Citabria, and each person gave me a different answer. Sometimes I got different answers from the same person. I don't think they were hiding anything (other than denial of the problem at first) so much as they didn't understand it for a while. I believe it's been addressed on recent production, but it you're looking at early American Champion models, look very closely at the tape lines on the upper wing surface, just outboard of the fuel filler, where the tape ends and the fabric begins. The cracks start out very small and it's easy to mistake them for a shadow or streak of dirt. The factory tape at this time was not pinked, so it's a straight line. After about 05 they stopped taping the lines altogether.

The crack propogates fairly quickly to the point where it will catch a fingernail, and then one day it may (or may not) just peel back a quarter inch or more.

The other issue with American Champion versions is poor quality control on the interior ( i reglued my side panels a dozen times), substandard (read: cabinet) hardware on such things as the oil filler door and the window latches, bare metal tail brace attachment and brakeline hardware that quickly corroded ...

Bottom line: I wouldn't worry so much about wood spar vs metal spar unless you need the higher gross weight of the factory aluminum spar models. Find a good airplane that has been well kept. But if you DO go for a wood spar, make sure you have a local mechanic who knows wood. It's one thing to take it to someone good for a pre-buy, another to have it inspected year after year.

 

[Dan Thomas]

Lance is right on the money here.

In addition, you have to look at other dynamics when it comes to early American Champion models. They had some problems with their paint system from when they restarted production in 1995 until about 2003-2004 wherein there was rampant cracking along the tape lines on top of the wing and on the horizontal stabilzer and elevator. I asked the owner, the owner's son, and the factory tech people about it numerous times in my previous life as a journalist as well as an owner of an 01 Citabria, and each person gave me a different answer. Sometimes I got different answers from the same person. I don't think they were hiding anything (other than denial of the problem at first) so much as they didn't understand it for a while. I believe it's been addressed on recent production, but it you're looking at early American Champion models, look very closely at the tape lines on the upper wing surface, just outboard of the fuel filler, where the tape ends and the fabric begins. The cracks start out very small and it's easy to mistake them for a shadow or streak of dirt. The factory tape at this time was not pinked, so it's a straight line. After about 05 they stopped taping the lines altogether.

The crack propogates fairly quickly to the point where it will catch a fingernail, and then one day it may (or may not) just peel back a quarter inch or more.

The other issue with American Champion versions is poor quality control on the interior ( i reglued my side panels a dozen times), substandard (read: cabinet) hardware on such things as the oil filler door and the window latches, bare metal tail brace attachment and brakeline hardware that quickly corroded ...

Bottom line: I wouldn't worry so much about wood spar vs metal spar unless you need the higher gross weight of the factory aluminum spar models. Find a good airplane that has been well kept. But if you DO go for a wood spar, make sure you have a local mechanic who knows wood. It's one thing to take it to someone good for a pre-buy, another to have it inspected year after year.

We have found some dangerous cracks in Champ spars. There are several types, one of the more dangerous being the compression failure at the ends of the strut attach doubler plates where local stiffening stresses the spar proper. Another place to find cracks is at the rib nail holes; the spar shrinks across the grain as it ages and the aluminum ribs don't so they hold the nails at fixed distances and the wood, as it shrinks, gets its grain pulled apart.

Positive thinking won't save a guy from disaster. There have been few failures, but I once flew an airplane that I later found had a badly cracked spar, a crack that had been there a long time and which would have failed altogether if I had pulled another G or so or gone inverted or hit some bad turbulence. I looked at another airplane that I suspected had a cracked spar, refused to deal on it, and it killed another guy a year later when that spar, which was cracked, broke in flight. Things like that, along with the other stuff I find as a mechanic, make one more than a little cautious.

Dan

 

[tonycondon]

i have 5 wood spars. i like em but it is nice doing this recover work that i get to have a good look at them. one of them does have a crack that i am slowly working towards getting repaired.

 

[Ken Ibold]

Positive thinking won't save a guy from disaster.

I hope you don't think I'm implying that. I just want to make it clear that there are many concerns to consider besides whether a spar is wood or not in that line of aircraft. Wood spars can succeed for decades, or they can fail. Aluminum spars can succeed for decades, or they can fail. The important thing is that the specific machine in question be examined by a competent inspector and that a decision be based on the condition of the entire airframe -- and that condition depends upon far more than the material the spar is made of.

 

[Baron2PG]

We have found some dangerous cracks in Champ spars. There are several types, one of the more dangerous being the compression failure at the ends of the strut attach doubler plates where local stiffening stresses the spar proper. Another place to find cracks is at the rib nail holes; the spar shrinks across the grain as it ages and the aluminum ribs don't so they hold the nails at fixed distances and the wood, as it shrinks, gets its grain pulled apart.

Positive thinking won't save a guy from disaster. There have been few failures, but I once flew an airplane that I later found had a badly cracked spar, a crack that had been there a long time and which would have failed altogether if I had pulled another G or so or gone inverted or hit some bad turbulence. I looked at another airplane that I suspected had a cracked spar, refused to deal on it, and it killed another guy a year later when that spar, which was cracked, broke in flight. Things like that, along with the other stuff I find as a mechanic, make one more than a little cautious.

Dan

Anyone know of a good "wood" inspector for a prebuy in the Atlanta area?

 

[weirdjim]

Things like that, along with the other stuff I find as a mechanic, make one more than a little cautious.

Dan

I once found cracked spars on five airplanes in a row ... until I found the crack in my inspection mirror.

 

[tonycondon]

Anyone know of a good "wood" inspector for a prebuy in the Atlanta area?

i have a couple friends in northern georgia who are vintage glider nuts who might be able to help. but i bet there are some champ guys you will find around Atlanta

 

[Fearless Tower]

Update to the story - just spoke with the owner - the 2008 paint job was just that, no recovering which likely explains the paint failures on the right wing. We'll see what the inspection finds under the fabric......