New Wing Spars

[dejh22]

Ok, I have a silly question. What is meant by 1:15 maximum permissible grain deviation ( slope of grain) Would that be 1" of slope over 15" Also I have read an old post on here were someone mentioned 6-8 grains per inch. I have the book Aircraft Construction Repair and Inspection by Joe Christy. This book is verbatim only the parts of 43.13 that directly apply to light aircraft. I have found the 1:15 slope, but I can not find mention the 6-8 grain per inch.
I have found a place about an hours drive from me that said they could produce sitka spruce spar blanks for me. I would like to drive up there and see what they have. I think it might be helpful for me to know what to look for. My IA called the other night and said that he wants to look over my project again because he has been thinking about something he saw on one of my spars. He said he wanted to look at the spars again and as long as he was out he would look over the whole project again. If he is thinking something about a spar is questionable, I will just make up new ones. I already have to rebuild the ailerons, so why not make it all new!

[mikeg]

Re: New Wing Spars

Check out FAA Advisory Circular, AC 43.13, on line (FAA.gov.) . It is THE word.
Mike

[Guest]

Re: New Wing Spars

Ok, I have a silly question. What is meant by 1:15 maximum permissible grain deviation ( slope of grain) Would that be 1" of slope over 15" Also I have read an old post on here were someone mentioned 6-8 grains per inch. I have the book Aircraft Construction Repair and Inspection by Joe Christy. This book is verbatim only the parts of 43.13 that directly apply to light aircraft. I have found the 1:15 slope, but I can not find mention the 6-8 grain per inch.
I have found a place about an hours drive from me that said they could produce sitka spruce spar blanks for me. I would like to drive up there and see what they have. I think it might be helpful for me to know what to look for. My IA called the other night and said that he wants to look over my project again because he has been thinking about something he saw on one of my spars. He said he wanted to look at the spars again and as long as he was out he would look over the whole project again. If he is thinking something about a spar is questionable, I will just make up new ones. I already have to rebuild the ailerons, so why not make it all new!

I don't find that 6-8 grains per inch spec in ac43-13 and it also seems a bit coarse to me.

Now I am curious and want to measure that on a spar and I also have a copy of ANC 18 upstairs, the aviation wood handbook. I"ll look in there.

Dave

[dejh22]

Re: New Wing Spars

Thanks....I have checked out 43-13. The book I have is "Verbatim" to what it says. It has all the info for light aircraft. I still don't see where it calls for 6 to 8 grains per inch minimum. I did see mentioned Navy Commerce Department Bulletin ANC - 19. I can not find a copy of that bulletin online. Maybe that bulletin calls out for a 6 to 8 grains per inch minimum?

[dejh22]

Re: New Wing Spars

Thanks Dave, I think if it is spelled out it will be in ANC-18 or is it 19? I have looked online for it but with no luck. If you find it spelled out in there please let me know.....again thank you!

I don't find that 6-8 grains per inch spec in ac43-13 and it also seems a bit coarse to me.

Now I am curious and want to measure that on a spar and I also have a copy of ANC 18 upstairs, the aviation wood handbook. I"ll look in there.

Dave

[dejh22]

Re: New Wing Spars

I think I found it in ANC-19. I love the internet! http://babel.hathitrust.org/cgi/pt?i...125;view=image

Thanks Dave, I think if it is spelled out it will be in ANC-18 or is it 19? I have looked online for it but with no luck. If you find it spelled out in there please let me know.....again thank you!

[Guest]

Re: New Wing Spars

Hi Dale,

I have anc18, you can get it from ESSCO but it does not have ring count as anc19c does.

Dave

[waltermrich]

Re: New Wing Spars

Have you consider Douglas Fir it meets the requirements for aircraft use and is about 1/4 the cost of Stitka Spruce, and is available locally at wood suppliers, the draw backs are it weighs slightly more is a bit more dense therfore not as fexible and is not as clean to work with ( splinters ), I for one would like to have the Spruce on a rebuild but it is about $1000 for 4 pieces of Spruce from suppliers I have contacted, Another thing you want to consider is the moisture content of the wood. Some that is not sold only for aircraft use might be air dried and have a little more moisture in it than you want.

[dejh22]

Re: New Wing Spars

My I.A. really would like me to use spruce. So I will use spruce. I'm not all that educated on lumber. How does one determine moisture content? The place I'm looking to buy my spruce spars from gave me this quote:

To fill your order we would need to quote the following:

4pcs 4/4x9-20' Sitka Spruce



60 board feet @ $9.03 per BF

$40 minimum charge for machine work

$65 delivery to Cedar Springs

[waltermrich]

Re: New Wing Spars

The 4/4x9 means its is 4 quarters thick by 9 inches wide, the spars are ruffly 6 inches by 3/4 inches and less than 5 inches by 5/8 inches, you will be milling a lot of material off but a good csbinet shop can do that for you, If it is air dried it can have up to 6 to 17 percent moisture in it, I think you want kiln dried wood ,and they can tell you, ask them the moisture content of the wood. Most importantly be sure it meets the specs of AC 43.13 for grain slope and codition, they will know that too, Some spruce is used for wooden boats and being in Michigan thats probably what they sell most to, I would like ther number if you do not mind , shipping was very reasonable.

[dejh22]

Re: New Wing Spars

They were going to do the mill work. These are the dimensions I told him.

3/4" thick 5 11/16" wide 17' long 2 ea.

5/8" thick 4 3/8" wide 17' long 2 ea

I was going to have him cut them a little long. Just so I'm sure, could you explain the slope, is it 1" over 15 "? Thanks!

Here is the website of the lumber yard. http://www.theworkbench.com/

[waltermrich]

Re: New Wing Spars

The slope refers to how stright the grain of the wood is on a board ft, It should be nice straight grain no more than 1 inch in a 15inch lenght of board,

[dejh22]

Re: New Wing Spars

That is what I thought, just wanted to make sure. Thank You Sir!

The slope refers to how stright the grain of the wood is on a board ft, It should be nice straight grain no more than 1 inch in a 15inch lenght of board,

[high time cub]

Re: New Wing Spars

http://www.westcoastpiet.com/construction.htm

HT

[waltermrich]

Re: New Wing Spars

Thanks for the information for the Spruce supplier,sounds good there spruce is kiln dried I did ask , Do you have the actuall dimenions of the spars , I have searched for a factory drawing many times with no positive results, I have gone by what i currently have on my wings , but would like to find a factory drawing.