aileron spars

[taylorukuk]

Has anyone managed to get aileron spars out of old wing spars?

We have 4 old wing spars but now cant source any more spruce.

[3Dreaming]

I have never tried to lay them out to see if it is possible, but I have heard of old spars being cut up to make smaller parts.

[Scott]

Dimensionally there's plenty of material. The problem is the holes left by nails, bolts, screws etc. There will be some nail holes at least, which will be acceptable to most people as long as they're free from rot. May be able to limit bolt holes to the non-critical areas. I would have no problem with spars built in this way but others may, so it may come down to the person signing it off.

AC43.13 has info on selecting wood, addressing anomolies and acceptable repairs.

Remember Taylorcraft made aileron and wing spars by joining, laterally, up to three separate pieces of spruce. It can be argued that a spar built up in this way actually has superior characteristics.
S

[taylorukuk]

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

[N96337]

Remember Taylorcraft made aileron and wing spars by joining, laterally, up to three separate pieces of spruce. It can be argued that a spar built up in this way actually has superior characteristics.
S

The one wing on my Tcraft has over a dozen pieces in it from the factory. Tcraft was broke and they took any acceptable wood and utilized it, according to a friend of mine that worked there in '46.
John

[Jim Herpst]

Has anyone managed to get aileron spars out of old wing spars?

We have 4 old wing spars but now cant source any more spruce.

You cannot find any aircraft grade Spruce out there? Guess I am glad I have hung onto the full set of new wing spars with elliptical tips for a clip wing that I made years ago...
The question is now what to do with em...

I think all the new spars from Wag Aero are fir...stronger but sure heavier

[Hank Jarrett]

Hey Jim, what is the weight of those Doug Fir spars? I calculated how much weight it would add once but the books don't take into account how much the weight can differ when actual wood is cut up. Evidently the density can be kind of wide ranging!

Hank

[Jim Herpst]

Hey Jim, what is the weight of those Doug Fir spars? I calculated how much weight it would add once but the books don't take into account how much the weight can differ when actual wood is cut up. Evidently the density can be kind of wide ranging!

Hank

Hank,

I do not have Doug fir spars (and I hope I will not need them either.l).have not gotten into the wings yet..once EVERYTHING is finished on the fuse to include tail feathers all ready for covering the wings will be next...AFTER uncover of the ailerons and going through them...so hopefully in the fall? (I wanted to start on them last fall lol.) Ah enjoying the process and progress every week however.

Jim

[taylorukuk]

We managed to source spruce to make 4 wing spars but at the minute the is NO spruce in the Uk which is aircraft standard.

Importing anything from the USA is now also very expensive with the postage costing more than the item itself.

[Jim Herpst]

We managed to source spruce to make 4 wing spars but at the minute the is NO spruce in the Uk which is aircraft standard.

Importing anything from the USA is now also very expensive with the postage costing more than the item itself.

Sorry did not think about you being accross the pond.

I know spruce is tough to get here in the US. Not on top of that at the moment however would not be surprised to hear it is very hard to get in the dimensions we need.

Hank you could probably easily average a given dimension of AC Spruce vs Doug fir then apply to each spar dimension and given your math skills get an answer quicker than me!!

I also do not know for certain Wag Aero is using Fir however I believe they used to mention it in the description....

[Hank Jarrett]

I have calculated the weight in the past (need to find it) but was just curious how close the book numbers are to reality. My books are from the 40s and a lot of today's wood is a lot wider grain and softer than the old wood. Wondering if anyone had actually weighed a spar. The scary part will be to cut out some test strips and break them to see if modern wood is as strong as the old stuff!

Hank

[Jim Herpst]

I have calculated the weight in the past (need to find it) but was just curious how close the book numbers are to reality. My books are from the 40s and a lot of today's wood is a lot wider grain and softer than the old wood. Wondering if anyone had actually weighed a spar. The scary part will be to cut out some test strips and break them to see if modern wood is as strong as the old stuff!

Hank

Strength of new vs old. Interesting topic. I know this. If there are no defects... CRACKS ! In my old spars there is no way I hell I would replace them because "new is better" wood has no memory ( from stress) BUT it sure can rot or crack.... Really close inspection rules the day. I would tend to believe that the old dry built up spars are indeed utopia.

[Hank Jarrett]

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. ;-)

[Mark Bowden]

The challenge is that you cannot just say Fir vs. Spruce. Region of growth and variety of type has quite different properties.

Most likely our forefathers found some nice spruce trees that were close to town and discovered that, Hey, this stuff works just fine! And used it even though a couple hills over there were stronger and just as light trees. It was likely just too far to hike.

In some cases Fir beats Spruce in nearly every single category including lower density and higher strength.

Tensile strength (lbs/in2) for: Pacific Silver Fir 95,500
Interior North Douglas Fir 107,000
Spruce, Engelmann, 84,800
Spruce, Sitka 59,300 (seems Sitka Spruce might be a lame as a choice, no?)

There are (4) Douglas Fir's and (7) Fir's.
For Douglas Fir the interior North and West (vs. coast) Fir are better.
For Fir, Pacific Silver is best.

There are (5) Spruce varietals.
Red, followed by Black are the best.

Douglas Fir is has the highest density, 0.43-0.50 @ 12% moisture.
Fir ranges from 0.35-0.40 @ 12% moisture.
Spruce ranges from 0.35-0.42 @ 12% moisture.

Fir and Spruce density is nearly identical, Douglas density is 10-25% higher but significantly stronger.

For more enjoyable bedtime reading, details are in Chapter 5 of the Wood Handbook published by the USDA and the Forest Service. It’s a free download!

You still have to follow the design guidelines for grain per inch and straightness, etc....
Mark.

[Scott]

Strength of new vs old. Interesting topic. I know this. If there are no defects... CRACKS ! In my old spars there is no way I hell I would replace them because "new is better" wood has no memory ( from stress) BUT it sure can rot or crack.... Really close inspection rules the day. I would tend to believe that the old dry built up spars are indeed utopia.

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