What kinda balsa?????

LAST EDITED ON Jun-07-03 AT 02:07 PM (CDT)
 
I got this chunk of balsa, it measures 1" X 3" X 36"

EDIT! It weighs 7 oz...

What density balsa is that and is it any good to use as the top for a built in fuselage?

Thankful in advance,

In Christ,

It's a common size of balsa but you need to know the weight of the balsa in pounds and its volume in cubic feet before you can calculate the density.

You might consider making laminated turtle decks on blue foam moulds/formers rather than carving them from solid balsa...it's less messy and less wasteful of expensive wood.

Sorry, Oliver, I forgot to put the 7oz.

Gotta be gettin' old...

In Christ,

>I got this chunk of balsa, it measures 1" X 3" X 36"
>
>EDIT! It weighs 7 oz...
>
>What density balsa is that and is it any good to use as the
>top for a built in fuselage?
>
>Thankful in advance,
>
>
>In Christ,
>
>Ion
>

A 1/4 x 3 x 36 inch piece of balsa that is of 4 pound density would weigh exactly one ounce. I always use this as my reference point from which to work. It makes it easier (for me) to weigh pieces of wood quickly and do an easy calculation in my head.

Your block is 4 times as thick, so a 4 pound density block of that size would weigh 4 ounces. Since it weighs 7 ounces you have 7 ounce (average) density wood. It is not the best, but certainly not bad, either, and could serve well as the top block in a fuselage since most of it will be carved away. Just remember to hollow well.

>I got this chunk of balsa, it measures 1" X 3" X 36"
>
>EDIT! It weighs 7 oz...
>
>What density balsa is that and is it any good to use as the
>top for a built in fuselage?

7 lb/cu.ft. - medium weight. Not the worst top block, but also not he best. The last block that size I got was 3.8 oz - very very light.

Thanks, Oliver, Len, Brett!

I'm gonna teke a good look at the plans, might be possible to use a molded sheet.

Ferenk Zamoly gave me a tip I find useful: When building a fuselage thet uses a carved up balsa block top you cover the top with 1/16 sheet, crossgrain. He said that the fuse will gain so much rigidity that you can even use marshmellow as a top...

In Christ,

Ion - do you store your balsa indoors, in your air conditioned home or out in the shop. It's pretty humid here in Florida, it's amazing what balsa can weigh after long term storage from one environment to another. I know some guys that do thier best to dry out a new ship indoors before Monokoting, so as not to get bubbles, when the heated moisture escapes.
EricV

Ion,

Leonard is correct...the density is 7 lb/cu ft., though he does it the hard way. <g>

Bill Calkins has two terrific Balsa Density Calculators programs on his site:

http://clflyer.tripod.com/Downloads/downloads.htm

Anyone that is interested in controlling the weight of their planes, has to know what the density is of the wood going into the project. Guess work here will just not get the job done.

Get a good digital scale and download either of the above two programs. The first program is written for Windows 3.1, and the second for Windows 9.x. Either work fine. The programs are flexible, allowing you to input the weight in either grams or ounces.

The procedure I used for measuring and marking the balsa is like this:

1- In the shop where my scale is, I weight each piece of balsa. Write the weight on a sticker, and apply the sticker to one end of the balsa.

2- As soon as I've done as much wood as I want, I carry the balsa to my computer table, and open Bill's program. Enter the dimensions and the weight off the sticker, and hit "calculate".

3- Using a felt tip pen ( to prevent damage to the balsa) write the density on the sticker, and go on to your next piece of wood.

When I'm through, the sticker on each piece of balsa, will have two numbers....the first is the total weight of the balsa in grams or ounces (I prefer grams), and the second number is the density in pounds per cubic foot.

Here's a neat feature of doing things this way. By putting the sticker on one end of your sheet or block, you can continue to cut parts from this piece of wood, and you will always know what the density is, right down to the last square inch. Very handy.

A big thanks to Bill for providing a terrific program.

Cheers,

One additional point when weighing the balsa. determine which end is the heavier and put the marking there. Then when sheeting a foam wing for example you not only put the heavy wood on the outside wing but the heavy end towards the outside even on the inboard wing. One kit for example wound up 1/2 oz heavier outboard before any tip weight by doing this.
I've been doing this since 1985 with a set of tables I created on Lotus (could do on Excel if that is all you have). My tables show the weight in grams for wood 1 to 4 inches wide 20 to 48 inches long and from 1/32 to 4 inches thick weighing from 4 to 12 lbs. They only take about 10 to 15 minutes to create print them then just weigh the wood and look it up on the tables.

SNIFF..

The idea of taking a perfectly good hunk of balsa and hollowing out (i.e. throwing away) most of it brings tears to my eyes. Better to mold thin sheets into the shape of a turtledeck, or cut one out of foam.

>SNIFF..
>
>The idea of taking a perfectly good hunk of balsa and
>hollowing out (i.e. throwing away) most of it brings tears
>to my eyes. Better to mold thin sheets into the shape of a
>turtledeck, or cut one out of foam.

But Isky, what else can I do with a balsa block?

As far as my knowlegde goes, the fate of balsa hunks is to be carved, wether you use them as fuselage tops, wing tips or whatever.

I'll be thankful if you can teach me other ways of using this chunk'o balsa.

If I can figure a way of doing the top of the plane I'm building with molded sheets I can even send it to you as a gift...

LAST EDITED ON Jun-08-03 AT 09:37 PM (CDT)
 
Get someone to saw it into sheets.. You can get two Flite Streak fuselages out of that wood, with some left over.

Molding turtledecks.. How about cutting a mold out of foam, and then draping hot-soaked balsa over it? Hold things in place with an ace bandage. Isn't this how Windy does it?

Hollowing blocks for turtle decks in particular, you waste more than 80% of that material. Environmentally, cutting down a tree and then not using it as efficiently as possible makes me cringe also. I have started molding as many pieces as possible. The High density foam mold works really well. And the foam is a recycleable material.

I guess its not just me.

PS: the slightly denser material is defineitely easier to hollow and handle than a piece of true 4Lb.

My understanding is that balsa "wood", is actually a grass, is this not correct. I thought it is more along the lines of bamboo, and grew very rapidly, and is very renewable, just not necessarily in the quality that we like it.

themouse

>My understanding is that balsa "wood", is actually a grass,
>is this not correct. I thought it is more along the lines
>of bamboo, and grew very rapidly, and is very renewable,
>just not necessarily in the quality that we like it.
>
>themouse

Ignore my ignorance, I did a google search, and it seems not everyone agrees if it is a weed or a tree, and I certainly don't know. I just read it in a magazine once, but it does grow back real fast.

themouse

LAST EDITED ON Jun-12-03 AT 02:59 AM (CDT)
 
It's most definitely a tree, of the broadleaf/deciduous/hardwood persuasion (i.e. non-conifer). The grass you're probably thinking of is bamboo.

http://www.uoguelph.ca/~antoon/hobby/sigbal.htm