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spruce

Old 02-03-2004, 03:54 PM
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haroldpo6
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Default spruce

my plans call for spruce spars, but the balsa supplyer that i am using does not carry spruce. the spars need to be tough and strong. what can i use instead. i have some straight-grain cedar i could cut to 3/8 sq. sticks. what do you think?
Old 02-03-2004, 03:56 PM
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spuck5644
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Default RE: spruce

You can use Bass wood. See if your balsa supplierhas that. You could also use a Balsa/CF laminate
Steve
Old 02-03-2004, 04:12 PM
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Default RE: spruce

Cedar is not as supple nor does it have the same tensile strength.

Carbon and balsa would be a good substitute but you would probably have to mail order the carbon. If you have to mail order you may as well get the spruce.

And lumberyard wood is NOT as good as proper aircraft grade Sitka spruce.

Er.... one exception. IF you can find some very nice close and straight grained hemlock that would be a decent compromise. Check in the area where the moulding wood is located. Specifically I'm talking about the 1/2 inch thick by 3,4 or 6 inch wide drawer side stock that some places sell. You're looking for wood that has a grain spacing of at least 20 rings per inch that shows very little runout. Look at the ends to check out the ring spacing.

PS: If this is intended for a highly loaded design such as a sailplane then stick with the right stuff. Or get the carbon. Hard balsa and carbon would be even better than spruce.
Old 02-03-2004, 04:17 PM
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Default RE: spruce

You can use Basswood, but it isn't quite as strong as spruce, but is a smidgeon lighter and is a good compromise. If you really want it to be as strong as spruce and are concerned about weight, then why not look into making some carbon fiber spars with a balsa core, or even just carbon fiber laminated balsa spars. They are very strong and lightweight.
If you absolutely, positively want to use spruce, then go to....

www.aircraftspruce.com

Patriot
Old 02-03-2004, 04:31 PM
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haroldpo6
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Default RE: spruce

thanks for the replys. I ordered the bass because they did not have the spruce with the rest of the order. I wanted to make sure it would be ok. they have a $25 min order.
Old 02-03-2004, 05:11 PM
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Default RE: spruce

If you go with the bass and are concerned at all with the strength, may I suggest you add a little beefier shear webbing to add to the overall strength, just as a little bit of insurance. It may be the differance between life and death.

Ok, maybe not quite that dramatic, but you get the idea.

Patriot
Old 02-03-2004, 05:34 PM
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Shane B
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Default RE: spruce

If you ever need spruce, i get mine from Wicks Aircraft, prices are good, and the wood is great,, Look them up on the web, I think you will be pleased,,,,They deal with real planes, so its not scraps your getting,,
Old 02-03-2004, 06:03 PM
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Default RE: spruce

thanks guys. I think I will go with bass and use 1/8 webbing. the plans called for 1/16. this plane is a cloud dancer 120 size. I will also be beefing-up the fuselage. I plan on using a g-23. I will also go with 98in wing. thanks harold
Old 02-15-2004, 02:15 PM
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Default RE: spruce

Hello, I see I'm not the only one having problems getting spruce. I have scaled up a 60" hooker to 120" and have been working and calling on Superior balsa for a month trying to get some 48" stuff but just don't have it. I had a large order with alot of balsa and spruce. Now i'm just getting the balsa that I need when I need it from a hobby shop. Expensive but at least I can get it. I will try the other places that I have read about on this post. Thanks and good luck guys. Hooker53
Old 02-15-2004, 05:10 PM
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Rodney
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Default RE: spruce

I have found that (if you are very selective in choosing the wood) that pine is nearly as strong as spruce. Just get close and straight grained boards and rip your own. Like mentioned above, if you get about 20 rings per inch and straight grained with no knots, it will do as well as spruce. Also, by making a weaker spar wider (not deeper) you increase the strength quite a bit. The sheer web does not have to be made thicker. The maximum bending stresses are in the outermost portion of the spar decreasing to zero at the halfway point.
Old 02-15-2004, 06:03 PM
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Default RE: spruce

Poplar, whicy is carried at Home Depot in thier craft woods... is a decent replaceent for Spruce. Its a bit heavier... but not a huge difference. Home Depot carries it in 1/4 X..... and 1/8 X.... (sheet widths, not sticks) 3 or 4 ft lentgths. Most hardwood dowels at the hobby shop... Poplar.
Old 02-15-2004, 08:00 PM
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Default RE: spruce

A few years ago i found a local lumberyard with some grade A douglas fir truss lumber. I bought a bunch of it, and just saw it up as needed and select it according to grain runout. I've also used plain old #2 pine 1x4s. Cut them into the necessary strips, throw out anything with excessive grain runout. ( more than about 1" in 14") Cheap and as good or better than the average hobby shop spruce sticks.

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