aileron spars

[Jim Herpst]

The wood may be sound, but the adhesive will have long passed its prime. So if the spars are of the built up kind, it's likely the 77+ year old glue no longer provides adaquate performance. One piece spars can have the doublers replaced, but would be a tough proposition to dismantle and rebuild a built up spar and still have it dimensionally correct.

Both my aileron spars were built-up and both had failed glue joints (10 years ago). Failed glue joints has been an issue for years and will only become more of a provlem as time passes.

S

Failed glue joints are one thing . Proven as failed. I would not replace spars for the sake of replacing them . I have not seen in researching this subject where resorsinal glue has failed "due to age" epoxy glues one cannot say such . Has resorsinal glue failed ?.again resorsinal . I have not seen it. Agree to disagree.

[astjp2]

I am pretty sure it was Doug Fir is 26% heavier than Stitca Spruce and 23% stronger. (DON'T go on my memory!!!) I AM sure it was stronger AND heavier and if you use wood that meets the selection criterion new Fir will be stronger in the same dimensions than Spruce. I was mainly curious how much heavier a part like a spar was since they use a 12" x 12" x 1" piece of wood for the calculations, and VERY few parts have those dimensions. ;-)

15% is book for weight and strength, you just cannot reduce size to accommodate for the weight increase unless an engineering study is performed and submitted to the faa and then the will scratch their heads and decide if it’s an stc Or engineering only approval.

[N96337]

My spars were failing. The wood is all good, but the glue is letting go. They used hyde glue on the splices from the factory. Mine were signed by the guys that built them.....Ken knew both of them from working there in '46.....and were dated June 12, 1946 if I remember right. Not all the joints were failing, and the doublers were still fairly good, but it was pretty much the ribs that was holding my spars together.
John

[taylorukuk]

I am actually restoring a Miles Messenger from 1946 for a Museum at the same time as our Taylorcraft.

It is a fully wooden aircraft with ply skins- Every single glued joint falls apart in your hands!

[Jim Herpst]

Resorsinal will not be the glue failing as described above . Hyde glue one could see. Actually I restored an L2 several years back. I did completely rebuild the wings but was surprised to see how well the hyde glue was holding up. Also that plane had been a military bird and had been outside tons

The laminated spars used resorsinal glue as I recall Forrest or Bruce Bixler stating in an old Taylorcraft news letter. I will go find it.

[taylorukuk]

The glue on the Messenger was casein glue.

However the 4 spars we had all had cracks and/or signs of glue failure.

[Jim Herpst]

Thanks all

Your thoughts represent mine - There is no rot in the spars they just looked aged which is why we replaced the wing spars with new.

The aileron spars we had were absolutely gone....

I think there are maybe 1 bolt hole that needs positioning to the lesser stressed areas.

I will post what we manage to do for future info.

BR Ian

Are you discussing the Messenger or the Taylorcraft when saying all four spars were bad. Just confused as your earlier epost above was talking about the Taylorcraft which you indicated they were all good but "looked aged" which is why you replaced them . No flames intended.

[Jim Herpst]

Also full disclosure. I have not yet started on my wings. Fuslage getting closer to being able to be put aside so I can begin those. The spars will be scrutinized for ANY defects!

[taylorukuk]

Taylorcraft main wing spars looked aged and had been spliced a couple of times. The glue on the splices was not holding.

Taylorcraft aileron spars had signs of glue failure and were delaminating in parts.

[Scott]

Another way of looking at the wood parts of a restoration, is value. What's important in terms of the finished aircraft.... longivity, piece of mind, resale value and potential, return on investment?

Even before I looked at my spars in any detail, I had made the decision to replace them. In the whole scheme of a full restoration, the spars are a relatively straightforward element (notwithstanding material supply problems).

Like it or not, wood structure in aircraft is not perceived by most people as an attribute. Published info on aging aircraft does not distiguish between type of glue, just that glue joints are an issue. With current covering processes, a fabric airframe can have a 30 year or more life expectancy. How are the glue joints going to be when there 110 years old?

The statement "New spars" is therefore important and has, I believe, a similar effect on value and piece of mind as say "sealed struts," especially if the alternative is 80 year-old pieced together originals.

I have four salvageable one piece spars (one has a repair) and two forward and one aft untouched sitka blanks. I have them because shipping is a problem, even within North America. They're available for reasonable cost to anyone who can arrange pickup (they are in the US or Canada).

[Jim Herpst]

Done beating this. Thanks

[N96337]

Done beating this. Thanks

Maybe you should listen to people that have actually HAD a problem, Jim! You seem to want to say we are all telling stories.
John

[Jim Herpst]

Also full disclosure. I have not yet started on my wings. Fuslage getting closer to being able to be put aside so I can begin those. The spars will be scrutinized for ANY defects!

John Maybe you should read my post (s).

Much appreciated. Thank you

[taylorukuk]

The second aileron spar finished today with all holes drilled and just awaiting a coat of West epoxy - Both were cut from wing spars and passed through a planer thicknesser.