Eagler's Nest

Airframes => Single Seaters => XL => Topic started by: bmxmann on September 05, 2017, 04:31:06 PM

Title: Rear spar Grain
Post by: bmxmann on September 05, 2017, 04:31:06 PM

So I just built the initial portion of the front spars, and one rear spar.  I didnt notice until after I built the first rear spar though that the lower spar cap had the grain vertical, and not horizontal.  I had made sure to double check the front ones, but somehow this slipped past me on the first rear spar until I pulled it out of the jig.  

So my question is how critical is this?  I bought the kit from John so these were all pre-cut minus the length.  I was going to shoot him an email then realized he is right out of Houston so probably has alot more important things going on now.  Thoughts, suggestions?  Most of me is hoping this isnt a big deal... otherwise its going to involve ordering new 13ft lengths or splicing smaller junks.... ugh.  Attached some pictures if what I am saying doesn't make sense...

Nick

Title: Re: Rear spar Grain
Post by: Dan_ on September 08, 2017, 06:01:14 PM

It is true the front spar carries most of the load, but is this something that will be on your mind every time you hit a little turbulence..?

If you want to calculate the load on each spar see the attachment below.  I did not make the attempt.

BTW  I will attach the other 2 parts of ANC-18 in other posts to keep under the 5 meg attachment limit.

Title: Re: Rear spar Grain /ANC-18
Post by: Dan_ on September 08, 2017, 06:02:53 PM

Part 1 of 3 attached

Title: Re: Rear spar Grain/ ANC-18
Post by: Dan_ on September 08, 2017, 06:04:27 PM

ANC-18 part 3 of 3 attached.

Title: Re: Rear spar Grain
Post by: wojtekseta on September 11, 2017, 03:32:28 AM

Spar caps works mostly under compression (top cap) and tension (lower cap). In this case it doesn't matter wthat is the direction of the grains.  In ANC-18 on page 204 you will find six types of beams. You will see, that in our type of beam they INTENTIONALLY drew grains vertically.

Title: Re: Rear spar Grain
Post by: bmxmann on September 11, 2017, 06:28:18 AM

Thanks guys for the information, really appreciate it!  After thinking about it for awhile i decided to move forward with it.  

Nick

Title: Re: Rear spar Grain
Post by: Tom XL-7 on September 11, 2017, 11:13:41 AM

when you order from aircraft spruce or wicks, you don't get to select grain orientation. I imagine a phone call or specific request could get you a choice.
So unless you are buying a square like 3/4 by 3/4 you get what they send you.  I think my 5/8 spar cap came differently than the others. I didn't lose any sleep over it.  
Tom XL-7