Spars

[Miguel]

Hello, friends
I need to get a plane of the spars of BL12-65, or BC12D, that I believe are same.
I am rebuilding wings of may aircraft and unforunately I do not have the original spars.
I need the location of the different holes for fastiening fittings, compression strurs, & location
of ribs and spar reinforcements.
If anyone can supply me with a copy, I will be extremely gateful.-
Happy flights hours, or happy hours of rebuilding for everyone.
Miguel

[Hank Jarrett]

Re: Spars

The best way to locate the holes is by overlaying the old spars on the new blanks. Do you still have the old ones? Drawings are OK, but the paper is not stable and over the length of the spar will introduce some significant errors from temperature and humidity. If you don't have the old spars to use as a pattern you need to use the DIMENSIONS from good spars or a drawing, NOT a full size drawing used as a pattern!
I have a set of good spars at my house but that is a LOT of measuring if you aren't close!

Hank

[Miguel]

Re: Spars

Hello, friends
I need to get a plan of the spars of BL12-65, or BC12D, that I believe are same.
I am rebuilding wings of my aircraft and unforunately I do not have the original spars.
I need the location of the different holes for fastiening fittings, compression strurs, & location
of ribs and spar reinforcements.
If anyone can supply me with a copy, I will be extremely gateful.-
Happy flights hours, or happy hours of rebuilding for everyone.
Miguel

[Miguel]

Re: Spars

Thanks, Hank. Yes, you are correct. I need a drawing with locations of holes,
ribs and reinforcements. Of course, at scale 1-10 can be OK, if are specified
distances from each border.-
Miguel.-

[Hank Jarrett]

Re: Spars

URUGUAY!!!!!! I kind of doubt you can bring your spar blanks over to use mine as a pattern! I will start looking for a drawings, but I am not sure I ever had a set of the hole locations. Anyone else have the correct drawing before we start breaking out the drill bits and card-ex (a tool we used to use to precision measure hole locations)? Does anyone even know what the allowable location error is?

Hank

One way or another, this is information a LOT of us could probably use in the future. Our spars won't last forever.

[Hank Jarrett]

Re: Spars

I posted a request for the drawing on the other Taylorcraft group too. Hopefully someone has the drawing.

Hank

[Miguel]

Re: Spars

Thanks by your help, Hank!
MIguel.

[Hank Jarrett]

Re: Spars

Great news! Turns out the drawings for the spar drill tool DO EXIST and Forrest is going to try to find them. It may take a while, none of us are spring chickens any more (English saying meaning we are getting kind of old and slowing down). If the drawings aren't available within a couple of weeks, post again! Sometimes we need a reminder.

Hank

[skip]

Re: Spars

When I rebuilt my wings with new spars a couple of years ago, my A&P and my IA helped me a lot digging through the regulations to make sure we did everything by the book. We included the references on the major-repair 337 so that we could have all the "IAW" stuff chapter and verse.

The tricky part relates to producing an owner-produced part for the spars. In order to have an owner-produced spar, either the original spar must be available to be copied or factory approved drawings must be used. Here is 43.13-1b 1-41:

1-41. SPAR REPLACEMENT. Replacement of spars is a major repair. Spars may be
replaced by new parts made by the manufacturer or the holder of a Parts Manufacturer
Approval (PMA) for that part. Owner-produced spars may be installed providing they are made
from a manufacturer-approved drawing. Also, a spar may be made by reference to an existing
spar providing sufficient evidence is presented to verify that the existing spar is an original
part, and that all materials and dimensions can be determined. The dimensions and type of
wood used are critical to the structural strength of the aircraft. Care should be taken that any
replacement spars accurately match the manufacturer’s original design.

I referenced the original Taylorcraft stamps on my old spars and also the IA's examination of the general condition supporting the fact that my spars were original equipment. I also had the drawings from STC SA1-201, but those do not include the full spar drawing. So I referenced the copy clause rather than working from a "manufacturer-approved drawing". I did autograph and date the new spars (at the suggestion of my local FSDO) so that no one mistakes my new spars for factory originals. As careful as I was, it seems to not be legal to copy mine in the same way I copied the factory originals.

Does anybody actually have a factory approved drawing of the spars as required by 43.13-1b 1-41?

Another question for the FAA Lawyer wannabes out there. My reading of the literal words of 43.13-1B 1-41 seem to state that I can produce an owner produced part if I have a factory approved drawing, but then the next sentence might be read to say that ANYONE could make a new spar by copying the original as long as "sufficient evidence" is provided that the original was really a factory original.
Am I reading that right? Or does the FAA link the second sentence to the "owner produced part" and some random A&P copying an original spar would be in hot water? In either case I think that I am in good shape, but inquiring minds want to know...

[M Towsley]

Re: Spars

I posted a request for the drawing on the other Taylorcraft group too. Hopefully someone has the drawing.

Hank

What other Taylorcraft group???

[skip]

Re: Spars

URUGUAY!!!!!! I kind of doubt you can bring your spar blanks over to use mine as a pattern! I will start looking for a drawings, but I am not sure I ever had a set of the hole locations. Anyone else have the correct drawing before we start breaking out the drill bits and card-ex (a tool we used to use to precision measure hole locations)? Does anyone even know what the allowable location error is?

Hank

One way or another, this is information a LOT of us could probably use in the future. Our spars won't last forever.

And

43.13-1b 1-41. SPAR REPLACEMENT. Replacement of spars is a major repair. Spars may be
replaced by new parts made by the manufacturer or the holder of a Parts Manufacturer
Approval (PMA) for that part. Owner-produced spars may be installed providing they are made
from a manufacturer-approved drawing. Also, a spar may be made by reference to an existing
spar providing sufficient evidence is presented to verify that the existing spar is an original
part, and that all materials and dimensions can be determined. The dimensions and type of
wood used are critical to the structural strength of the aircraft. Care should be taken that any
replacement spars accurately match the manufacturer’s original design.

Hank, (and everyone else)

First, STC SA1-201 includes drawings of the spar root and has the dimensions for the root fittings and holes. We need to negotiate with Terry as he owns the STC, but that is approved data and we can use it as such. the STC doesn't include a full spar drawing with all the dimensions.

Reading 43.13-1b 1-41, it says
"a spar may be made by reference to an existing spar"
Not the one and only original spar from your plane, just AN existing spar. as long as it is verified as yada yada yada,

It then says "and that all materials and dimensions can be determined."
The material is solid or laminated spruce IAW the paragraph of 43.13 that describes legal spruce..
As for the dimensions,
It doesn't say to lay the old spar over the new blank and drill the holes.
It doesn't say that there must be approved data.
It just says the dimensions must be determined.

How hard would it be to measure an existing spar and publish the dimensions on the forum?
I guess the rub would be just what the FAA means by "must be determined". If I measured my spars and put the data out here and then you tried to use it, just how well have you "determined" the dimensions?

What might it take to verify and measure an original spar and then get the data out in a way that would satisfy the "all materials and dimensions can be determined" part of 1-41?

[Guest]

Re: Spars

Was thinking about how to measure it. I have an old spar set.

I suspect that one would have to bring the spar indoors and let it "dry" so that moisture content is not a fact (mine are outside but under cover).

Then make bushings that fit in each size bolt hole that have a point at the center so you can measure to the center easily OR some other scheme to achieve this.

Perhaps one could lay a piece of some sort of plastic that is dimensionally stable over the spar, mark teh holes then roll it up and mail it away?

After all of this and recalling that spar material will likely be shipped from the NW United States and incur freight costs then why not just buy a set of spars from Wag Aero? about $750 each on average.

Dave

p.s. I wonder where WagAero got their spar drawings from?? You and I will never see them.

[Hank Jarrett]

Re: Spars

Working now to get the factory dimensions so we can maybe reproduce the original tooling (using factory data). If we can do that we should be able to drill pilot holes in a spar blank for the owner to finish ream all holes and add the doubles and finish. The tool should be allowable as "legal" to locate the holes for the owner and the owner can do the rest of the work to satisfy the Owner Produced Parts requirements.

Miguel may be stuck with making another tool (kind of expensive to ship the tool or spars that far compared to making another tool) but at least if anyone else down there needed a spar teh tool would already exist fairly close by.

Hank

[Guest]

Re: Spars

Why not support the industry that supports us and buy from them? Wag Aero, Univair, Rainbow...

[skip]

Re: Spars

Why not support the industry that supports us and buy from them? Wag Aero, Univair, Rainbow...

This is an excellent point that bears repeating. If I ever do another wing I will probably support our good vendors by purchasing spars. I do value them. In my case the choice wasn't about cheap.

Having the opportunity to build up my own spars with some very expert and experienced tutelage was a rare and very valuable learning experience for me. The combination of needing a wing rebuild and having the experienced guidance available was an opportunity that I couldn't pass up. I don't think the vendors will begrudge the loss of a sale in that case.

I think if someone's attitude is "I've never built a spar but I can do it cheaper" then there is probably something really wrong going on.