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basswood vs. balsa wood vs. Spruce

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Old 12-29-2010, 04:58 PM
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psgugrad
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Default basswood vs. balsa wood vs. Spruce

I am curious to know the strengths of balsa vs basswood vs spruce. From what I've read/heard, spruce is about 3 times heavier than balsa but about 6-8 times stronger. Also that basswood is about the same weight as spruce but only about half as strong. Anyone else here know what the relative strengths/weights are? Is basswood acceptable for spars?
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Old 12-29-2010, 05:42 PM
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Default RE: basswood vs. balsa wood vs. Spruce

Everything is stronger then balsa but some wing designs don't require the stronger hard woods for stringers so no reason to add the weight. I cut my own stringers from long pieces of scrap wood left behind at my wood working club. If I find spruce I use it. I just go through the pile looking for light weight hard woods without any knots in it. If I find some hard balsa in the LHS, say in 1/2 inch I will buy that and cut stringers as needed from it.
I will have to copy a sheet we have at the shop that tells the strength and weight of the different hard woods and try to post it.
Gene
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Old 12-30-2010, 07:17 AM
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Default RE: basswood vs. balsa wood vs. Spruce

Unfortunately, any tables or charts for wood strengths are just averages. since wood strength varies with growth rate, moisture content, physical locations of growth (think tropic or arctic or anywhere between) you have to use a little judgment in choosing the wood you use by physical inspection. For instance, you can find balsa so hard you have a hard time driving a nail into it yet some is so soft you can poke your finger through it.
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Old 12-30-2010, 08:32 AM
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Default RE: basswood vs. balsa wood vs. Spruce

From what I've noticed, at least on the bigger airplanes I build, sheetingis the only big part of the airplane thats balsa, but there arestill small parts like the LE that use balsa, and areas needed to sand something to shape like a fillet. All the spars, ribs, webs, doublers, formers, ect are all ply/basswood. Thats on the bigger airplanes that is.

On smaller airplanes, more balsa is used mainly to lighten the airplane up. A extra 300 i finished not to long ago was 95% balsa wood.

More strength=Plywood/Basswood

Less Strength-very light= Balsa

Hope this helps!

Jason
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Old 12-30-2010, 09:32 AM
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Default RE: basswood vs. balsa wood vs. Spruce


Quote:
ORIGINAL: Rodney

Unfortunately, any tables or charts for wood strengths are just averages. since wood strength varies with growth rate, moisture content, physical locations of growth (think tropic or arctic or anywhere between) you have to use a little judgment in choosing the wood you use by physical inspection. For instance, you can find balsa so hard you have a hard time driving a nail into it yet some is so soft you can poke your finger through it.
Well said Rod!! We have a chart in our shop but it's a guide. We have a speed chart for lathe turning too but it doesn't always work. When I'm going through the scrap pile I go by feel, if it feels light enough and is clear then it's mine. Goes right onto the table saw and turns into many different sizes or comes home with me to age on the rack.
I think Jason is buying plans for display planes, I have never built one with a lot of hardwood in it. I have run into a few using what I thought was way too much light ply but not a lot of hard woods??
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Old 12-30-2010, 10:23 AM
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Default RE: basswood vs. balsa wood vs. Spruce

I am always shocked how strong Joe Bridi's wings are. Balsa spars and no shear webbing.

I do add 1/4" sq balsa trusses to the spars myself. When weighing the difference, it is a bit lighter than shear webbing, and just as strong. The balsa is a lot lighter than the hardwoods.

Of course, these are on 60 size airplanes and smaller....

Brian
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Old 12-30-2010, 10:32 AM
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Default RE: basswood vs. balsa wood vs. Spruce


Quote:
ORIGINAL: Gray Beard

I think Jason is buying plans for display planes, I have never built one with a lot of hardwood in it. I have run into a few using what I thought was way too much light ply but not a lot of hard woods??
I was talking about the REALbig planes, like 100+" wingspan. Airplanes over 20-25 pounds. For example, my Don Smith B-17 has all fuse formers, all ribs, all HSTAB and FIN called on the plans to be hardwood. Whether thats because it has 4 big heavy engines hanging off the stucture, and it needs the extra strength, or people just like building big flying big bolders!!!!

Jason
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Old 12-30-2010, 10:39 AM
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Default RE: basswood vs. balsa wood vs. Spruce

At that size, the materials will not be an adverse neccessity to the wingloading.

Brian
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Old 12-30-2010, 01:55 PM
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Default RE: basswood vs. balsa wood vs. Spruce

I use Lauan plywood its about 3/16. I made a rib to match a rib in a kit I have and it was .03 oz more than the balsa rib. A 4x8 sheet for $10 makes a lot of parts.
Ken
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Old 12-30-2010, 04:05 PM
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Default RE: basswood vs. balsa wood vs. Spruce


Quote:
ORIGINAL: box car

I use Lauan plywood its about 3/16. I made a rib to match a rib in a kit I have and it was .03 oz more than the balsa rib. A 4x8 sheet for $10 makes a lot of parts.
Ken
I don't recal hearing the name Lauan, is that the type of wood it is made from or the manufacture of the ply?? Sounds good. I have the plans for a big Hots but was put off by all the light ply used in the construction. I didn't even want to figure out the weight of the beast when finished. It has about a weeks worth of cutting out lightening holes just in the fuse!!
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Old 12-31-2010, 12:52 AM
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Default RE: basswood vs. balsa wood vs. Spruce

I get it at Lowe's. Stock #12549 5mm about $10 for a4x8 sheet. They do have it cut in 2x2 or 2x4 sheets. I like the 2x2 sheets easy to work with.
Ken
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Old 12-31-2010, 12:57 AM
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Default RE: basswood vs. balsa wood vs. Spruce

http://www.rcuniverse.com/forum/m_96...page_17/tm.htmhere are some ribs I made out of it. Post 423
Ken
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Old 12-31-2010, 07:18 AM
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Default RE: basswood vs. balsa wood vs. Spruce

Lauan plywood is generally just a less expensive (and some what lower quality) plywood than you will normally find in your local hobby shop. If you use it check for grain density and glue quality to make sure it will be okay for the task.
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Old 12-31-2010, 07:22 AM
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Default RE: basswood vs. balsa wood vs. Spruce

"the name Lauan, is that the type of wood it is made from or the manufacture of the ply"

A lot of it used in the 60's in kitchen cabinets, and RV interiors. A lot like ply, with a good looking skin, of various patterns. I added some access doors into the area below a seat in our travel trailer, and used an X-Acto knive to cut out the opening I wanted.

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Old 12-31-2010, 07:50 AM
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Default RE: basswood vs. balsa wood vs. Spruce


Quote:
ORIGINAL: LesUyeda

"the name Lauan, is that the type of wood it is made from or the manufacture of the ply"

A lot of it used in the 60's in kitchen cabinets, and RV interiors. A lot like ply, with a good looking skin, of various patterns. I added some access doors into the area below a seat in our travel trailer, and used an X-Acto knive to cut out the opening I wanted.

Les
Thats what they call it at Lowe's. I have used it for years never had a problem with it, I like it cause its lite. I never have seen it in a hobby shop.
Ken
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Old 12-31-2010, 09:04 AM
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Default RE: basswood vs. balsa wood vs. Spruce

Luan is a sub-species of honduran mahogany. generaly not as rot resistant considerably softer and lighter, with more plain grain figure. fast growing trees are grown plantation style in tropical climates. commonly used for door skins, cabinet backing, relatively cheap plywood of minimum ply count and inexpensive furniture. small parts don't hold up very well asthe integrity of the ply bonding is usually not very good. in dimensionallumber form,it is relatively stable when seasoned correctly and completely strong enough for our purposes in any use as it is generaly available in long , very straight grained, clear boards.
watch out for the prices at the big box stores, though, they will simply call it "mahogany", and price it accordingly, which is a major rip-off.
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Old 12-31-2010, 09:38 AM
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Default RE: basswood vs. balsa wood vs. Spruce

If I manage to get out on a road trip today I will pop over to Lowe's and take a look at the Lauan, thanks for the part number. Ordering light ply from a wood supply is getting a bit out of my price range plus the shipping cost. My club bought a pannel saw last year so buying a 4X8 sheet would work out great for me. Cost of wood and covering is one reason I gave up building big planes, just one reason but it is at the top of the list.
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Old 01-01-2011, 07:28 AM
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Default RE: basswood vs. balsa wood vs. Spruce


Quote:
ORIGINAL: ron ward

Luan is a sub-species of honduran mahogany. generaly not as rot resistant considerably softer and lighter, with more plain grain figure. fast growing trees are grown plantation style in tropical climates. commonly used for door skins, cabinet backing, relatively cheap plywood of minimum ply count and inexpensive furniture. small parts don't hold up very well asthe integrity of the ply bonding is usually not very good. in dimensionallumber form,it is relatively stable when seasoned correctly and completely strong enough for our purposes in any use as it is generaly available in long , very straight grained, clear boards.
watch out for the prices at the big box stores, though, they will simply call it "mahogany", and price it accordingly, which is a major rip-off.
Nice write up Ron, that about covers it all. I do seal mine with sanding sealer 2 coats asI do with my balsa. I only buy it at Lowe's or Home Depot at $10 a sheet.
Ken
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Old 01-01-2011, 08:42 AM
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Default RE: basswood vs. balsa wood vs. Spruce

If you guys want to stock up on spruce go here [link=http://www.aircraftspruce.com/catalog/wppages/capstrip.php]Aircraft Spruce[/link]

It is aircraft grade spruce and much cheaper than you can buy in a hobby shop. 1/4sq spruce for .21 ft . I am getting ready to order 500ft.
Anthony
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Old 01-01-2011, 09:26 AM
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Default RE: basswood vs. balsa wood vs. Spruce

Balsa is very strong for the weight if you pick it properly. The problem with using balsa, especially for larger models is, to get the strength you may need to use a large piece of balsa. To keep the volume down you use a smaller stronger piece of wood such as basswood or spruce. If you look at the strength to weight listed by the OP you will see spruce is about twice as strong for the weight, basswood is about the same strength to weight as balsa. The benefits of balsa over the other woods is balsa is easier to work, and lower cost. Up until about 15 years ago balsa was cheap and easy to get. As balsa become more expensive you will see the use of other woods, and composites, more and more.
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