Spar dimensions

[gmackay]

When ordering spar stock, what are the dimensions that need to be ordered for front and rear spars for a 46 BC12D? Or where can I find that info (I don't have mine torn apart yet)

Thanks,
Greg

[Don Eide]

Re: Spar dimensions

Greg,

My front one measures 3/4" x 5 11/16" x 16' 2 1/4.
My rear one is 5/8" x 4 3/8 x 16' 2 1/4"

Hope this helps.

Don

[gmackay]

Re: Spar dimensions

Thanks Don!

Greg

[gmackay]

Re: Spar dimensions

One more question..........it looks like the original spar is milled down at the fuselage attach point, then plywood doubler glued to it. What is the best way to do this , or have it done? Or is it required?

Thanks,
Greg

[Don Eide]

Re: Spar dimensions

Greg,

Yes it needs to be done, and the best way I can think of is to find a cabinet shop with a good powered planer and plane off 1/16" on both sides back
9 13/16" plus the radius of the planer. The plywood is 1/16 x 9 3/4 x 5 11/16.
Hope this helps.

Don

[Steve Green]

Re: Spar dimensions

I used a good router with a new bit, practiced on 3 or 4 scraps first, and it worked just fine. Work from the end of the spar in toward the middle, for the obvious reason of support for the router base. Just take your time.

[gmackay]

Re: Spar dimensions

Thanks everyone.

Greg

[Acroeric]

Re: Spar dimensions

Acually I found it easier to use a joiner as it is much more accurate and easier to control- pretty sure that is what the factory did.

The front spars are not 3/4 , they are 25/32 which is about .03125 thicker than 3/4. I have some factory dimensional data on the size somewhere. I would check with Forrest prior to ordering material but I am 99.9% sure.

I am getting ready to build another set of wings and plan to order from Wicks- they have been the best so far for spruce.

[gmackay]

Re: Spar dimensions

Eric,
So what sizes do you order then from Wicks? I see 3/4 and 13/16 but not 25/32. I just placed my order yesterday, but maybe can change it.

I suppose if a guy builds the wood ribs, he could make it whatever size he wanted. Also, what size capstrips would you recommend for the ribs? 1/4 or 5/16, or???

Thanks,
Greg

[jCandlish]

Re: Spar dimensions

I suppose it is easier to find a planer than spar stock.

Not that I have ever built a wing, but I did train and work as a jointer were one always planes to size.

[Forrest Barber]

Re: Spar dimensions

There are no wood ribs on a "B" Taylorcraft 0nly on the "D" . The spar stock is always over size then you plane to proper dimensions. That gets them straight.....

[crispy critter]

Re: Spar dimensions

Greg and Eric,
I have a copy of the factory blueprints for a BC12D.The spar drawings say 3/4" on the front and 5/8" for the back.Forrest is correct,if you order 3/4" it will be just a hair thicker or it should be.

[gmackay]

Re: Spar dimensions

Forrest,
Thanks, but I'm talking about an experimental clip wing. But you bring up a good point......what size capstrips did they use on the "D" model wood ribs?

Thanks,
Greg

[Dick Huish]

Re: Spar dimensions

Greg, the model "D" uses 1/4 X 3/8 cap strips. The vertical parts are 1/4 X 1/4. Dick

[Don Eide]

Re: Spar dimensions

ERIC,

Have you found the Factory Data showing 25/32 yet?????

1. My spars (all 4) are laminated and scarfed, the best I can count, 29 times. If you think the dimensions are the same, guess again. I have measurements from a strong 3/4 (a light 25/32) up to a strong 26/32 (13/16 plus) usually over a scarf joint but not always, including the thickness of many coats of varnish.

2. The Harer STC shows the main spar thickness to be 3/4 and the fittings are built with a 3/4 opening.

3. I also find it hard to believe (But anything is possible) that a Co. trying to make money would buy extra large wood and plane it down to 25/32.

4. Just so we are not all on the same page, I have better luck with Aircraft Spruce, the spars I have ordered were,,,, I would say perfect. I used them as is. No planing required.

Don