Aileron spar end-on profile

[mhorowit]

Playing with my old aileron spars, I noticed a taper as shown in the attachment.
If you've taken your aileron apart, did you notice the same thing?

Second, the spar stock I ordered was 3" wide, so it looks like I need to add shims to make up the 3/32" difference. Does anyone see a problem with the liberal use of shims? - Mike

[Bobdog]

Re: Aileron spar end-on profile

The taper on the top of the spar is correct. It is suppose to match the angle on the op of the rib. My aileron ribs had a 3/8 X 3/8 X 1/8 plywood shim under the flanges where they are nailed to the spars.

[Robert Lees]

Re: Aileron spar end-on profile

Mike:
This photo

and

this photo show the little shims to which Bob refers.

You will also note that I laminated an additional strip on one edge to increase the spar thickness.

Rob

[mhorowit]

Re: Aileron spar end-on profile

ALL RIGHT!!!!
I notice little bits of plywood acting as shim on SOME of the ribs, but I suspect I'll need to shim all; nice to know what others had to do. - Thanks

[mhorowit]

Re: Aileron spar end-on profile

It is suppose to match the angle on the op of the rib. .

I got "op" on the rib? ??? Please, what's an "op"? - Mike (running down to the basement to see if I can see if there is an angle in the slot of the rib).

[mhorowit]

Re: Aileron spar end-on profile

I got "op" on the rib? ??? Please, what's an "op"? - Mike (running down to the basement to see if I can see if there is an angle in the slot of the rib).

Don't know if it's "OP" but the slot is not at right angles to the flat or curved edge of the rib, hence the need for the taper.

Now, my new spars came untapered. Should I simply slip a shim 'tween the rib and spar and not worry about the untaper? - Mike

[mhorowit]

Re: Aileron spar end-on profile

I'm going to have to add about 1/4" to the width of my current spars in order to be able to add the bevel. I'd like to use spruce, since that's what the spar is made of. A local quality lumberyard doesn't carry unprimed spruce, but they do have fir. They say it's in the same family and shouldn't make a difference.
Since I'm making such a small addition to the existing spar, does anyone have an opinion as to whether or not I can use fir for the addition? - Mike

[high time cub]

Re: Aileron spar end-on profile

Mike,
How about ripping the needed 1/4 inch spruce from your old spars?

[mhorowit]

Re: Aileron spar end-on profile

Mike,
How about ripping the needed 1/4 inch spruce from your old spars?

It's a good idea, but I need the old spars for a pattern.
- Mike

[Hank Jarrett]

Re: Aileron spar end-on profile

Mike,
Douglas Fir is stronger AND heavier than Spruce. The strength to weight is lower for Fir but that just means if you make the part to the same dimension it will be stronger AND heavier. If you make the part to the same weight it will be weaker (kind of hard to do anyway). If you REDESIGN a part for Fir from a Spruce original design for the same strength it will be SLIGHTLY smaller, the same strength and just a little heavier. For really small pieces the Fir should be the same dimensions and the weight will be hard to even tell the difference. As long as the wood is good and the glue joint tests good you should be able to use the Fir with an unmeasurable weight gain.
Hank
Don't you love it when you ask the time and I tell you how to build a clock?(;f

[astjp2]

Re: Aileron spar end-on profile

Can you say HOME DEPOT airplane parts, Wood, Douglas Fir, verticle grain, clear with 6-8 grains per inch minimum and then cut them to the same angle as the top of your rib so they just slide over, and you can use the Aircraft grade plywood in most hobby stores for your gussets----costs about $20.00 per spar and a days time to make....good luck Tim

[mhorowit]

Re: Aileron spar end-on profile

Can you say HOME DEPOT airplane parts, Wood, Douglas Fir, verticle grain, clear with 6-8 grains per inch minimum and then cut them to the same angle as the top of your rib so they just slide over, and you can use the Aircraft grade plywood in most hobby stores for your gussets----costs about $20.00 per spar and a days time to make....good luck Tim

Hmmm
I had fixated on fir and the fancy lumberyard and forgot to go to HD for fir.
Think I'll pay them a visit and if they have fir, count rings. I still have the fancy 'yard to go to - Mike

[mhorowit]

Re: Aileron spar end-on profile

Mike,
... and the glue joint tests good ...

Talk to me about the need for a glue joint test; what's it testing? certainly not the correct mix of glue ingredients because I'd need to let the glue dry before beating on it and then mix up a new batch of glue.

And I don't mind the horology lesson - Mike

[astjp2]

Re: Aileron spar end-on profile

You can find the good wood in the hardwood section, I went through about 30 boards before getting a good 8' pair, I also bought a 4' one for the support where center the aileron attach fittings was. Good luck Tim

[Hank Jarrett]

Re: Aileron spar end-on profile

When you mix up your glue you need to use part of it to glue some test pieces together. You glue your parts and the test pieces at the same time from the same batch then break the test pieces to prove the glue was good. Hank