Wood grain orientation

[rotornuts]

Below is an illustration I made up to try and describe grain orientation and what is considered common practices. The names are also common names although by no means an exaustive list of all the potential names used. The opinions expressed by me are in the context of what I would consider best practices for blade construction using commonly available wood at a moisture content of 12% or less. Other restrictions and conditions may apply.

 1 - Horizontal grain/Plain sawn

 2 - Vertical grain/Quarter sawn

 1a - Prefered layup method for horizontal grain. Alternate curvature but maintain horizontal grain orientation. This layup will be more elastic through its thickness than a vertical grain layup but is more prone to warpage and will experience its greatest deviation through its thickness as the moisture content changes.

 2a - Prefered layup method for vertical grain. Alternate curvature but maintain vertical grain orientation. This is commonly considered the most rigid through its thickness and least likely to warp layup. It will on the other hand experience the greatest deviation in its width as the moisture content changes.

 3 - Umm, just don't do this. As wood expands and contracts seasonaly the most through the growth rings this yields unpredictable and potentially undesirable results.

Conclusion:

Editors Note:
On request of the author the following was updated  

as noted in this comment
Comment

 2a - is considered best for blades due to its rigidity and its resistance to warpage.

 1a - is next best

 3 - is the least desirable

Disclaimer: Wood used to be a living breathing organism before harvest and processing as a result every single piece is as unique and diverse as the human race. It is only possible to try and predict woods behavior based on collective observation, labratory tests and an understanding of woods structure at a cellular level. There will always be exceptions to what is considered "normal" behavior for different species of wood.

Hope this helps a bit. Sorry for the qualifications and disclaimers but....

nuts

[PHinker]

Nice!  Thanks for the information, rotornuts.

Paul

[Shadow]

 A picture is worth a thousand words! This is soo much easier to see and understand in layman terms.I plan on laminating Cedar for next set of blades,I'm like Dan, a firm believer in Linseed oil. But I'm wondering if Linseed oil (or any oil) will affect the glue over time? A few years ago I built numerous 8 and 10 foot high slab fences and pens for raising Whitetail Deer, I wanted to put Linseed oil on but the vet said be careful in case the deer eat it or lick it, So Instead I went to the Wholesale store and bought 5 gal pails of Canola oil, 13.00 for 5 gals. filled up the back pack sprayer a gave everything two coats. Smelled like Macdonalds for about a month, but soaked in nice, protected the wood from greying, you can still 5 years later feel it with your fingernail.Probably coat them again this Summer. Sorry got off track here..

[rotornuts]

I've used vegetable oils myself for things going in the kitchen and for kicks to see how it works and it works pretty good but it can become tacky sometimes(in stickyness not style). That's neat to find out it works well outside. I can't say if linseed or other oils would effect glue but would say it's very unlikely unless maybe your using hide glues?

Thanks for the comments. It makes it worth while to go through the effort of preparing info this way.

Nuts

[ghurd]

With 2a, won't the thin blade tips be subject to spliting?

G-

[rotornuts]

Short answer gurd is yes. If you support the edges of a 1/4 sawn board and load the center it will split easier than a horizontal grain board but in a blade the wood is loaded equally across its width aside from aerodynamic forces which I highly doubt would split the board. Checking(splitting) of wood due to seasonal movement(moisture changes) typicaly occurs across the growth rings putting horizontal grain wood at risk of splitting anyway not to mention across the growth rings is a weak point anyway when the wood is thin.

1/4 sawn stays the winner in my point of view.

It's a good observation though and likely subject to debate.

Nuts

[kitno455]

am i mistaken, or did your conclusion of the first post suggest that plain sawn was better, but now you say quartersawn? or can i just not read?

allan

[rotornuts]

Your right I goofed it up. the conclusion list should read as 2a best then 1a and three as least desirable. Anyone know how to edit posts?

[JF]

Dear Rotonuts

Many thanks for your contribution to the discussions concerning laminated wood for rotor blades.

Although - I would perhaps suggest considerably more laminations. Likewise I am pleased that the grain sequence has been commented and rectified

May I suggest that others may wish to consult a previous 14-page file - the work of several friends and colleagues - concerning both the theory and praxis of not only blade visualization - but also the construction process and possible difficulties etc of this very usefull rotor technology.

http://www.otherpower.com/images/scimages/119/bladecar.pdf

Greetings and best wishes - JF

[rotornuts]

Thanks for the comment

I typically get my wood by "high grading" from lower grade lumber so the pieces are usually smaller than full dimensions. As a result most of my laminations are made up of many pieces and most of them are from 1" stock. To do a lamination 9" wide I would have  12 pieces involved. I'm all for more laminations in a wind turbine blade but I don't think it would be widely accepted so I decided to represent what I thought was a reasonable number of pieces.

I'm also happy that the sequence error was spotted but I wish I could correct the origional post. O well.

BTW. I'm actually not interested in building wooden blades myself as I don't have confidence in the ability to reproduce anything but the simplest designs with any accuracy without a cnc or patterned horizontal laminations. I posted this info because there had been some posts requesting info on grain orientation. Also I wanted to help out those who are willing to build wooden blades.

Nuts

[TomW]

Nuts;

What, exactly, would you like changed?

I am not tracking this whole thread very close but if you explain what you want altered in the original story I can do that for you no problem.

Cheers.

TomW

[BT Humble]

So Instead I went to the Wholesale store and bought 5 gal pails of Canola oil, 13.00 for 5 gals. filled up the back pack sprayer a gave everything two coats. Smelled like Macdonalds for about a month, but soaked in nice, protected the wood from greying, you can still 5 years later feel it with your fingernail.Probably coat them again this Summer. Sorry got off track here..

I use engine oil (new, not drained from the sump) on the handles of shovels, picks and other tools.  It dries off nicely to a shiny surface somewhat like varnish, but doesn't peel and blister in the same way.

BTH

[rotornuts]

If you look up at the origonal post, in my conclusions I stated that layup 1a was considered best and 2a was second best. This should be reversed to read 2a as best and 1a as second best. This of course reflects my preference for vertical (1/4 sawn) grain orientation when looking for resistance to warpage and stength through the thickness of a lamination. My conclusion list is contrary to that statement and I'm sure could easily lead to confusion.

If you could swap the 1a and 2a headers I would appreciate it.

Thank you,

Nuts

[rotornuts]

Tom. If I may I would also appreciate if you could place a note in the post at the coorection stating the coorection has been made to eliminate further confusion.

Thanks again,

Nuts

[bobn]

some aditional remarks about blade laminations.

http://www.woodenpropeller.com/Basic_Propeller_Construction-_Techniques.html

a pictur is worth a thousand words.

BobN

[TomW]

Nuts;

Well I edited it, hope it is what you wanted.

Cheers.

TomW

[rotornuts]

Yes, That's it. Thank you Tom.

Nuts

[rotornuts]

Bob, That link has a great image of the horizontal laminations I was refering to for acurracy of reproduction. It's the only way I'd do a multi blade set without specalized machinery.

Just a note to add confusion. In a different context than that refered to in the original post ideed horizontal laminations with a high number of plies will have the highest ultimate strength as well as be a lot more work.(more opinion)