Spars

[joecnc2006]

Shipping for long pieces gets expensive, Looking over the irondesign242 videos (see attached) I see a notation of a scarf on the spar, has anyone done this to eliminate the long pieces for the spar and the caps, I would imagine they need to be staggered, etc. Can someone point me to an example post or source of it being done for the LE. I tried several searches but did not find anything.

[Dan_]

... I tried several searches but did not find anything.

Here is some reading on the spar cap laminating subject:

http://www.eaglersnest.com/forum/index.php?topic=374.0

http://www.homebuiltairplanes.com/forums/wood-construction/2773-scarfing-laminating-wing-spars.html

AC 43-13 calls for various reinforcement plates. 


YouTube Videos:

[ParQld]

Hey JoeCNC2006.

as I live in Australia, i had to order all my spruce in shorter lengths for transport as did Grant Booth from Temora. We both spliced the Spar caps using slightly different methods but got the same result. I will post some images soon

cheers Paul

[ParQld]

Joe here is a link to a video of me cutting the splices. Its a compilation done by Google so please excuse my wife's lasagne image that pops up, must their version of a TV commercial. anyhow you will get the idea.

https://goo.gl/photos/wrZ9VCv2zo13Tb6Q6

I made a tapering jig for table saw to complete the splices. The underside of the jig that overhangs the spar has "cats paws" or tiny brad nails that grip the spar cap to stop it slipping back in the jig during the cut.

There is also a link to some more images of what i did if you are interested.
https://goo.gl/photos/U9ZDFaw1PXiUtELMA

let me know if you have any questions.

[joecnc2006]

That looks great, how did you do the spar ply itself, being so thin you could not do a scar did you just but it up?
Also when constructing the spar were your spliced cut placed vertical or horizontal.

[ParQld]

Joe

the splices are vertical as this is the strongest and are covered by the plywood webs for added strength.

here is a snap shot from the DE Plans showing this. I did not scarf the plywood webs, could not see the point. 2 clean butt joins would be OK with good epoxy. In the DE all the splices are covered front and back with the webs, not sure about the LE. I will see what other image and  video i have and let you know.

cheers Paul

** just an addendum, where the ply webs but to each other, I used reenforcing gussets behind the plywood that are epoxied to the rear side of the web **

[joecnc2006]

I just need to decide where i want to place the splice, the wing is 154" long, and from the wing root the strut is 77" in the center of course do not want any splices in that location.

[Steve]

I just need to decide where i want to place the splice, the wing is 154" long, and from the wing root the strut is 77" in the center of course do not want any splices in that location.

Prudent to stay at least one rib bay away from the strut attaches and outboard of them... Never in the rib bays on either side of the strut attach...

[John Reinking]

Here is an FAA link about wood repairs, scarfing wood, etc.   Very helpful.   Wanted to upload it but it was too large a file.  Building DE spars at the moment.   Built a scarfbox jig for the router.   Works great.  Cheers.

[joecnc2006]

I got a quote from aircraft Spruce for the Spar Material listing of $663.54 and from wicks aircraft supply of $879.32 all before shipping. (note: no plywood yet quoted)
Where does everyone get their plywood, locally or just order from them also?

What were your cost and cost with shipping?

[Dan_]

Where does everyone get their plywood, locally or just order from them also?

You may want to try these guys...  http://www.boulterplywood.com/  

Perhaps someone on here has done business with them?

They claim instant quotes by phone or email from their contact page, and have spruce and fir.

Let us know how it turns out.

[joecnc2006]

Where does everyone get their plywood, locally or just order from them also?

You may want to try these guys...  http://www.boulterplywood.com/  

Perhaps someone on here has done business with them?

They claim instant quotes by phone or email from their contact page, and have spruce and fir.

Let us know how it turns out.

They have spruce but not aircraft grade spruce, he said it would may not be aircraft rated quality.

[joecnc2006]

I was also asked if I needed 45° or 90° plywood? I imagine this is the grain pattern, wouldn't 45° work better for this application if that's what they are talking about, or does it matter.

[Dan_]

I was also asked if I needed 45° or 90° plywood? I imagine this is the grain pattern, wouldn't 45° work better for this application if that's what they are talking about, or does it matter.

45 is best for the spar shear web.  You will want the grain oriented with the 45 to the outboard.   Like this if sitting in the pilots seat... Left side \\\\\\\, right side ///////.
http://www.eaglersnest.com/forum/index.php/topic,295.msg1605.html#msg1605

90 may bend easier around the leading edge... 90 should certainly be cheaper.

Edit:
NACA Technical Report 344 concludes 45 degree is preferred for shear webs.  However 90 is certainly used for economic reasons in our type aircraft.

Also, since aircraft plywood should have alternating layers of grain 90 degrees to each other, a case can be made for not needing to concern with orienting the face grain.  However there is a case to be made when there is a majority of grain in one direction.  For example 3 ply with the front and back plies in the same orientation.

There is a lot of engineering on the West coast Piet site.  

[joecnc2006]

Does anyone have their invoice from aircraft spruce handy that they could share, Or where ever you got your spruce and plywood.