help with meaning of some words in plans
 

hello, i'm quite good at building foamboard planes, but now i want to try something from balsa, i've downloaded telemaster 400 plans, i've changed all measure units ibto metrical system... but still, because my english skills are not perfect, i can't understand some things here, maybe someone can explain me with simple words, what is SPAR(HARD), SHEAR WEBS and some mysterious looking T.E and L.E.(full thing looks like 1/4 sq t.e.)

Hi, Razzion! Welcome aboard! Never be afraid to ask questions. That's how we learn.
The spar is the main piece of wood that goes from the center of the the wing out to the end. The ribs attach to the spar. The spar will usually be located about 1/3 of the way from the rounded leading edge (L.E.) of the wing. The trailing edge (T.E.) is the narrow rear edge of the wing. In aircraft plans, they do not use the words front edge and back edge. They are referred to as the leading edge and trailing edge, or LE and TE.
The shear webs are pieces of wood that are installed on the front and back of the spar, between the wing ribs. Think of it as a sandwich, the shear webs are the two slices of bread and the spar is whatever you like to make your sandwich from, although I would not recommend trying to eat the spar and shear webs. You may get splinters in your mouth and that would not be any fun!
The SPAR(HARD) means that the spar should be made out of a hardwood, something other than balsa.
The 1/4 sq t.e. means that the trailing edge should be made from a piece of wood that is 1/4 of an inch, or .250, square in shape. Each side should be 1/4 of an inch across.
I hope this helps.
Nice having you here!

Nice response!

oh, now i understand :D thank you very much :D, i just used to make my previous planes by russian guides, and i just didn't had any chance to learn english terminology :) and yea, sorry for my english skills :D

Thank you.

I am glad I could help you. And don't apologize for your English. It's much better than my Russian! :D

I have to agree with RCPAUL, that was a nice response Flyboy
Razzion, do you have any other questions we can help you with?
BTW, I do want to add to Flyboy2610's definition of a shear web. It can be installed as two pieces, sandwiching the spars in between as described earlier, a single piece on either side of the spars or, more difficult to do is to slot the spars and sandwich the shear web in the slots between the spars. Any of the three can be used in any wing. One thing that is a must, however, is to have the web grain running up and down or it's just added weight that isn't helping you

as i understand, this web grai is marks of trees growth? so this web grain must be vertical(like in picture)?

No, the shear web grain should be vertical as in the direction that the tree grows, not the rings of the tree. I know that it seems like the wrong way for strength, but it ties the spars together very well.

oh, ok, i understand now :)

Looks like this.

i understand... it just connects two spars, and because of vertical webs, this connection is very strong :) i want to say thanks to everyone, I thought that i won't get so many friendly answers

We try to help!
As Red Green (http://www.redgreen.com/) used to say, after giving some advice to the men watching his program, "Remember, I'm pulling for you. We're all in this together."

The way I see it, if someone needs help and I can do so, I'd only be hurting myself to not do so

Spruce is the best wood for spars. Spars need tensile strength, and spruce has the best for its weight.

I don't know the particular plane you're building, but sometimes when the plans call out "spar hard", what they mean is hard balsa, not necessarily spruce. If using hard balsa, sheer webs will really add a lot of strength.

And, while that is true, I'd still consider spruce just due to the added strength over hard balsa.

i am building telemaster 400 (wingspan almost 1m) and thanks for advise, anyway i think that aditional strength can't be excess :)

When they say "spar(hard)" it can mean either of two things. Balsa comes in many weights and sometimes the designer just means to use the harder of the balsa spars. It could also mean use a different type of wood such as pine, bass wood, etc. but it usually means to just use the harder balsa as it is the stronger of the different weights (also usually much heavier per unit volume than the lighter grades of balsa. Just a bit of knowledge most do not realize is that balsa is defined as a hardwood as it is a deciduous type of plant. It can be so soft that you can poke your finger through a 1/4 inch sheet or so hard you need a saw or very sharp blade to cut it. Strange also is that a single balsa log can have a very soft part and a very hard section on the same limb.

yeah, i know about different types of balsa, thanks :)