kit b. o. t.
10-19-2010, 12:41 AM
#1
Thread Starter
kit b. o. t.
hey guys.
im building a b. o. t. kit. i have 8pieces of balsa blocks measuring almost 3" long by 3/8" by 1/2". the wood grain runs the width of the block whicks which makes them snap very easy.i could not find them in the instructions or on the plans. i have been building since the 80's and have built many kits but this one has me stumped. thanks for any replies.
im building a b. o. t. kit. i have 8pieces of balsa blocks measuring almost 3" long by 3/8" by 1/2". the wood grain runs the width of the block whicks which makes them snap very easy.i could not find them in the instructions or on the plans. i have been building since the 80's and have built many kits but this one has me stumped. thanks for any replies.
10-19-2010, 06:52 AM
#4
Senior Member
RE: kit b. o. t.
ORIGINAL: Tinkrerpilot
Sounds like filler material for the wing joiner tubes in the wing spars.
Sounds like filler material for the wing joiner tubes in the wing spars.
Yeah, sounds like webbing between the wing spars from the root out.
10-25-2010, 01:19 AM
#5
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RE: kit b. o. t.
Hello,You should have 10 pieces of 3/8x1/2x3" balsawith the grain vertical on the 1/2' side.These are the sheerwebs that go in the rib bays marked with a dot on the spar from the rib bay aa-a and the four bays after that.Do not omit these as a catastrophic wing failure will result.
10-25-2010, 12:24 PM
#6
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RE: kit b. o. t.
HEY,
Shear webbing has verticle grain do to that is the direction of the (compression ) load. Webbing acts just like the middle piece of an I beam, it ties the top and bottom spar together. This keeps compression buckling of the spares minimal. Sometimes we see Kevlar tow wrapped around spars to cancel out buckling in the other direction. Usually though that is a job the glue does but you know how we love to push the limits on a winch launch.[sm=devious.gif]
Have you built the wing yet? We would love pictures
Boo boos HAPPEN to all of us so don't sweat it if you made one.
It wasn't a plane but just the other day I was making a kitchen cabinet door. My very first cut on the table saw was wrong[:'(] so off to the store for a new 24" x 48" sheet of cabinet grade plywood. My wife thought it was funny. I can tell because she shares the story every chance she gets
Shear webbing has verticle grain do to that is the direction of the (compression ) load. Webbing acts just like the middle piece of an I beam, it ties the top and bottom spar together. This keeps compression buckling of the spares minimal. Sometimes we see Kevlar tow wrapped around spars to cancel out buckling in the other direction. Usually though that is a job the glue does but you know how we love to push the limits on a winch launch.[sm=devious.gif]
Have you built the wing yet? We would love pictures
Boo boos HAPPEN to all of us so don't sweat it if you made one. It wasn't a plane but just the other day I was making a kitchen cabinet door. My very first cut on the table saw was wrong[:'(] so off to the store for a new 24" x 48" sheet of cabinet grade plywood. My wife thought it was funny. I can tell because she shares the story every chance she gets
10-31-2010, 04:01 PM
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RE: kit b. o. t.
They are your shearwebs for the inner wing panels. They must fit snugly between the wing ribs and spruce spars so that there are no gaps, not even small ones. Shear webs resist the buckling loads placed on the wing during a winch launch. When a sailplane wing breaks on a launch, it is usually due to a compression failure of the top spar. Shear webs will help prevent this to a point. The stock BOT wing will take a lite to moderate winch launch. Carbon reinforcement of the spars will give you a stronger wing.
Pete
Pete
07-06-2011, 04:43 AM
#13
RE: kit b. o. t.
I agree with the others about the "blocks" being shear webbing - that's how I treated mine. Y'all probably already know this but, in your spoilers (which are NOT shown in the plans - you're on your own) I would recommend a 3-bay spoiler. I did 5-bays with mine (1.5" chord) and it was way too much. Cut them down to 3 bays and it's a lot better.
Going back to the webbing, being such a long wing and I wasn't really sure just what the loads would be on it (I launch with a rather heavy-duty hi-start) I took no chances and ran webbing all the way to the tips - front and back to the bend and 2 bays beyond, front side from there to the tip. Probably wasn't necessary but I feel better about it.
There are some few points I'd change if/when I build another though - and these are just my personal thoughts, no real aeronautic necessity here. My next one will have a longer nose - probably about 3" longer to help with balancing (she comes out tail-heavy, even sanding as much off as I felt safe with, and I had to add what I think is a bit much in the way of lead to the nose), I'm increasing the amount of elevator travel (especially DOWN) to about twice the design-throw and I'd change the vertical stab/rudder to something more of a full-flying set-up - like the old Airtronics Aquila had while increasing the area of the rudder by at least 30%. Last mod would be a longer tail-skid. My flying field grass doesn't get cut as short as I'd like and the tail tends to "snag" more than I like on landings.
Like I said, these are not things of necessity here, just my thoughts on a bit of improvement for "my" way of flying.
Hey! Good luck with your build. She's a pretty good bird.
Dave
Going back to the webbing, being such a long wing and I wasn't really sure just what the loads would be on it (I launch with a rather heavy-duty hi-start) I took no chances and ran webbing all the way to the tips - front and back to the bend and 2 bays beyond, front side from there to the tip. Probably wasn't necessary but I feel better about it.
There are some few points I'd change if/when I build another though - and these are just my personal thoughts, no real aeronautic necessity here. My next one will have a longer nose - probably about 3" longer to help with balancing (she comes out tail-heavy, even sanding as much off as I felt safe with, and I had to add what I think is a bit much in the way of lead to the nose), I'm increasing the amount of elevator travel (especially DOWN) to about twice the design-throw and I'd change the vertical stab/rudder to something more of a full-flying set-up - like the old Airtronics Aquila had while increasing the area of the rudder by at least 30%. Last mod would be a longer tail-skid. My flying field grass doesn't get cut as short as I'd like and the tail tends to "snag" more than I like on landings.
Like I said, these are not things of necessity here, just my thoughts on a bit of improvement for "my" way of flying.
Hey! Good luck with your build. She's a pretty good bird.
Dave
