BC12 Front Spar

[astjp2]

Spruce is what is original, so he is wrong

[Hank Jarrett]

Remember lamination is NOT the same as splicing! Laminated spars are stronger, splices are very HARD to.get the same strength. The difference is the glue line in a lamination FOLLOWS the grain and splices CROSS the grain. I would not make a splice in a spar unless it was just the tip (last rib to the tip bow) even if the FAA said I could. I don't think I am that good a wood worker and wouldn't trust my splice.

Hank

[taylorukuk]

Hank - I should have said laminate not splice.

Tcraft spars are spruce - That makes it all a bit easier as spruce is a bit easier to source!

Douglas fir came from Wag Aero website as the replacements are fir that they sell..

Thanks for the info.

[Scott]

My original spars(complete with TAC stamps) were single piece spruce. I think the factory used both solid and laminated to make the best use of their wood supply.

3 of my spars are still usable if the doublers were to be replaced. If they were laminated there's a good chance the glue in the laminations would have failed by now (as was the case with my aileron spars).

[astjp2]

Hank - I should have said laminate not splice.

Tcraft spars are spruce - That makes it all a bit easier as spruce is a bit easier to source!

Douglas fir came from Wag Aero website as the replacements are fir that they sell..

Thanks for the info.

Doug fit is acceptable as long as you do not reduce the size by the 15% increase in strength and weight the fir gives.

[taylorukuk]

Thanks all

[n6346m]

We looked at the WAG Aero option but they were not really interested in sending it to the UK and final price for a front spar was approaching $2500 delivered ($900 on the website)

Brian,
That's ridiculous. Someone must have made a mistake in their quote. If you give me your email address I can send you a copy the quote that I got from Lynden Transport to send a 192 inch long by 12 inch diammeter cylinder containing a wing spar weighing less than 100 lbs total from Seattle to London (air freight) for under $364 US. If you want to buy my used serviceable spar, i'm selling it for 1/2 of what Wag aero wants at $450 US and you pay for the shipping tube and freight. I don't know where you are in the UK but you'll have to pick it up in London or make arrangements to have it shipped from there.
The spar I am offering was removed from a used BC12 wing that I bought to dismantle and use the ribs and will not fit my L-2 as the L-2 has a thicker front spar than the B series airplanes. If you don't want a used spar at all and just want a new spruce blank, I may be able to help you there as well. When I bought the new spruce to make a new spar for my L-2 I got enough wood to make two new spars. I won't know if I will need to make another spar until I take the other wing apart which may be sometime from now. You can contact me at n6346m at gmail dot com.

Bob Picard

[TC747paul]

my L2 spars have the following (this is NOT the same as your BC)
front spar is a stacked wood design with full thickness 5/8" and two pieces stacked one on the other
the rear spar is a lamination of two 3/8" thick x full height x full length of the spar
if you look at the factory drawing (i think) used to specify spar blanks they allowed see notes 7 and 8
very interesting

[taylorukuk]

Thanks for all of the info

[Mark Bowden]

I have a '46 that has a full span splice on the top of the section, kind of like bonding on a spar cap. It is factory original.

Here are some numbers in the chart from the wood handbook. Fir and Spruce densities are quite similar.
The wood handbook (Chap 5) gives property numbers for all species, even species by region at two moisture contents, green and 12%. Fir is stronger.

If you would be interested in wood, it would be good reading, lol. And you can get it downloaded for free.


wood prop numbers.pdf

[astjp2]

I have a '46 that has a full span splice on the top of the section, kind of like bonding on a spar cap. It is factory original.

Here are some numbers in the chart from the wood handbook. Fir and Spruce densities are quite similar.
The wood handbook (Chap 5) gives property numbers for all species, even species by region at two moisture contents, green and 12%. Fir is stronger.

If you would be interested in wood, it would be good reading, lol. And you can get it downloaded for free.


[ATTACH]n190518[/ATTACH]

Is it the one I posted in the tech reference section?

[Mark Bowden]

Yes, it is. Sorry I should have noted you posted it earlier. I had it from my Cessna days so I forgot it was here.

[taylorukuk]

We are just about to drill / cut our new spar stock and was intending to use existing spars as a template.
We have 4 wings however none of the spars are the same!

One rear spar was repaired by a reputable engineer in 1995 (i have the receipt) with a new piece of spar stock spliced in and it has the inboard compression strut holes 1" out of position on the front spar - quite unbelievable!

Does anybody have a copy of Taylorcraft drawings B12-A80 (front spar) and B-A88 (rear)?

[Scott]

I put these drawings together by measuring the OEM spars that were in CF-CLR. They will no doubt include typical errors associated with measurements determined by tape measure and ruler (not to mention bifocals).

That said they may be useful to you for comparison purposes.
S

[taylorukuk]

Thanks Scott

Very useful